BROMELIACEAE: PROFILE OF AN ADAPTIVE
RADIATION
This book presents a synthesis of the extensive information available on the
biology of Bromeliaceae, a largely Neotropical family of about 2700
described species. Reproductive and vegetative structure and related
physiology, ecology and evolution are emphasized, rather than floristics
and taxonomy. Guiding questions include: why is this family inordinately
successful in arboreal (epiphytic) and other typically stressful habitats and
also so important to extensive fauna beyond pollinators and frugivores in
the forest canopy? Extraordinary and sometimes novel mechanisms that
mediate water balance, tolerance for high and low light exposures, and
mutualisms with ants have received much study and allow interesting comparisons among plant taxa, and help to explain why members of this taxon
exhibit more adaptive and ecological variety than most other families of
flowering plants. This volume concentrates on function and underlying
mechanisms, and thus complements a literature that otherwise mostly
ignores basic biology in favor of taxonomy and horticulture.
. is the Robert S. Danforth Professor of Biology at
Oberlin College, Ohio, USA. His research career has focused on the biology
of epiphytic vegetation, especially bromeliads and orchids. He is author of
The Biology of Bromeliads (1980) and Vascular Epiphytes (1990).
BROMELIACEAE: PROFILE OF AN
ADAPTIVE RADIATION
DAV I D H . B E N Z I NG
Oberlin College, USA
With contributions by B. Bennett, G. Brown, M. Dimmitt,
H. Luther, I. Ramírez, R. Terry and W. Till
The Pitt Building, Trumpington Street, Cambridge, United Kingdom
The Edinburgh Building, Cambridge, CB2 2RU, UK http://www.cup.cam.ac.uk
40 West 20th Street, New York, NY 10011-4211, USA http://www.cup.org
10 Stamford Road, Oakleigh, Melbourne 3166, Australia
Ruiz de Alarcón 13, 28014 Madrid, Spain
© Cambridge University Press 2000
This book is in copyright. Subject to statutory exception
and to the provisions of relevant collective licensing agreements,
no reproduction of any part may take place without
the written permission of Cambridge University Press.
First published 2000
Printed in the United Kingdom at the University Press, Cambridge
Typeset in 10/13pt Times NR MT in QuarkXPress™ []
A catalogue record for this book is available from the British Library
Library of Congress Cataloguing in Publication data
Benzing, David H.
Bromeliaceae: profile of an adaptive radiation / David H. Benzing;
with contributions by B. Bennett . . . [et al.].
p. cm.
Includes bibliographical references (p.
) and indexes.
ISBN 0 521 43031 3 (hardback)
1. Bromeliaceae. I. Title.
QK495.B76B45 2000
5849.85–dc21 99-30141 CIP
ISBN 0 521 43031 3 hardback
Contents
Part one
1
Part two
2
3
4
List of contributors
Preface
Acknowledgments
Glossary
Abbreviations
Brief overview
Introduction D. H. Benzing
Basic structure, function, ecology and evolution
Vegetative structure D. H. Benzing
Habits: general overview
Organization for foraging
Relationships of the body plans
Stems
Roots
Vascular cells
Foliage
Trichomes
Reproductive structure D. H. Benzing
Inflorescences
Flowers
Fruits, ovules and seeds
Pollen grains
Carbon and water balance D. H. Benzing
Ecophysiological peculiarities
The five ecophysiological types
Photosynthesis and water economy
Crassulacean acid metabolism: basic characteristics
Bromeliad CAM: basic characteristics
v
page ix
x
xiii
xv
xviii
1
3
17
19
22
36
42
46
48
50
52
70
79
81
89
98
105
107
110
111
114
115
117
vi
Contents
Ecological correlates of the carbon fixation syndromes
Ecophysiological profiles of the five types of
Bromeliaceae
Xeromorphy and water relations
CAM vs. C3 bromeliads: performances in situ
Predictors of photosynthetic capacity (Amax)
Hydration
CAM reconsidered as an evolutionary response to stress
Citric acid: its role in ecophysiology
CAM and hydration
Additional aspects of light relations
5 Mineral nutrition D. H. Benzing
External supply and plant demand
Nutritional peculiarities
Nutrients in the forest canopy
Mechanisms
Involvement of foliar trichomes
Nitrogen nutrition
Architecture and nutritional economy
Bromeliads as air quality monitors
6 Reproduction and life history D. H. Benzing,
H. Luther and B. Bennett
Pollination
Floral rewards
Fragrances
Flowering phenology
Breeding systems
Synchronization within populations
Genetic structure of populations
Seed dispersal
Seed viability and germination
Resource economics and life history
The organization of reproductive allocation
Demography
Asexual reproduction
Final comments
7 Ecology D. H. Benzing
Frost-tolerance
Distribution in forests
Roles in succession
120
123
145
151
160
162
168
174
174
176
187
188
197
199
209
229
235
238
240
245
246
264
268
268
276
280
281
284
299
301
305
308
323
326
329
331
339
362
Contents
10
8
9
Part three
10
11
Influences of shoot form on bromeliad distribution
Effects of epiphytic bromeliads on trees
Effects of bromeliad nutrition on forests
Terrestrial Bromeliaceae
Bromelia humilis: a case study of terrestrialism
Relationships with fauna D. H. Benzing
Predators and pathogens
Mutualisms
Ants and bromeliads
Evolution of ant/plant associations
Termites
Phytotelm bromeliads
Bromeliads and the definition of soil
History and evolution D. H. Benzing,
G. Brown and R. Terry
Fossils
Phytogeography
Chromosomes, hybridization and polyploidy
Ancestral habitats
Heterochrony
Neoteny and tillandsioid radiation
Historic relationships between mesophytism and
xerophytism in Tillandsioideae
Taxonomy: traditional characters
Chemical systematics
Relationships among subfamilies and Bromeliaceae
within Liliopsida
Final comments
Special topics
Neoregelia subgenus Hylaeaicum I. Ramírez
Taxonomic problems
Ecology and geographic distribution
Cytology
Vegetative morphology
Trichomes
Inflorescences
Floral morphology
Reproductive biology
Continuing taxonomic problems
Cryptanthus I. Ramírez
vii
369
372
382
384
400
405
405
414
421
431
436
437
459
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464
465
488
493
500
504
509
516
517
521
540
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545
545
547
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549
549
550
551
viii
Contents
12
Tillandsioideae W. Till
Anatomy and morphology
Phytogeography and evolution
13 Tillandsia and Racinaea W. Till
Evolution
Subgeneric treatments of Tillandsia
Racinaea
14 Ethnobotany of Bromeliaceae B. Bennett
Folk taxonomy of Bromeliaceae
Uses of Bromeliaceae
Indigenous management of bromeliads
15 Endangered Bromeliaceae M. Dimmitt
Factors threatening bromeliad populations
In situ conservation
Ex situ conservation
Conservation laws and their implementation
Literature cited
Name index
Subject index
Taxon index
555
559
569
573
575
578
585
587
588
589
607
609
610
615
616
619
621
657
665
675
Contributors
David H. Benzing
Department of Biology, Oberlin College, Oberlin, Ohio 44074, USA
Bradley C. Bennett
Department of Biological Sciences, Florida International University, Miami,
Florida 33199 and Fairchild Tropical Garden, 11935 Old Cutler Road,
Miami, Florida 33156, USA
Gregory K. Brown
Department of Botany, University of Wyoming, Laramie, Wyoming 820713165, USA
Mark A. Dimmitt
Arizona–Sonora Desert Museum, 2021 North Kinney Road, Tucson, Arizona
85743, USA
Harry E. Luther
Marie Selby Botanical Gardens, 900 South Palm Avenue, Sarasota, Florida
33578, USA
Ivón M. Ramírez
Centro de Investigacion Cientifica de Yucatán, A.C., Mérida, Yucatán,
Mexico
Randall G. Terry
Division of Biological Sciences, University of Montana, Missoula, Montana
59812, USA
Walter Till
Institut für Botanik der Universität Wien, Rennweg 14, A-1030 Wien,
Austria
ix
Preface
Bromeliads enter recorded history with Columbus’s account of Carib
Indians cultivating Ananas comosus (pineapple) on the island of Guadeloupe. Within the next hundred years, commercial production began at
numerous Old World sites, and by the mid-19th century major European
botanical gardens were displaying numerous ornamental Bromeliaceae.
Ready access in culture and often novel adaptations for life free of contact
with earth soil in turn guaranteed the attentions of early phytogeographers
and morphologists. Interest has continued to grow until today more is
known about the ecophysiology of the bromeliads than about the members
of almost any other family of tropical plants.
Major advances in systematics, natural history theory and functional
biology over the last two decades have heightened opportunity to reconstruct adaptive radiations and impute the conditions of ancestors and their
habitats. Evolutionary relationships inferred from the structure of DNA
provide the robust phylogeny necessary to order and date the origins of
those aspects of phenotype responsible for current adaptive variety and
importance in ecosystems. Molecular, combined with traditional taxonomic, data have already expanded insights on the histories of clades as
diverse as the Hawaiian silver swords and stickleback fishes. However, none
of the inquiries on plants has considered more than a few of the many traits
that shape botanical radiations by dictating growth requirements, mobility,
relationships with other biota and ecological tolerances. Enough literature
exists for Bromeliaceae to explain in exceptional depth how a sizable taxon
of tracheophytes has colonized so many, often unusual, kinds of substrates
in varied habitats.
Probably no other family exceeds Bromeliaceae for the variety of services
provided to dependent biota ranging from detritivores to pollinators, nor
does any comparably sized clade employ a more novel array of contrix
Preface
xi
vances to acquire and utilize water and mineral nutrients. Some of the more
stress-tolerant bromeliads root in media that exclude most other vascular
flora because they lack equivalent capacity to exploit unconventional supplies of moisture and key ions. In short, Bromeliaceae exemplifies botanical radiation in the extreme, hence represents an exceptionally propitious
taxon to study related mechanisms and outcomes. This volume is devoted
to that challenge. Conversely, it largely ignores taxonomy for its own sake,
instead adopting an existing system (Smith and Downs 1974, 1977, 1979)
to organize the information more immediate to our purpose. The only deviations involve allusions to certain post-1970s revisions of genera, most of
which are identified. Whenever possible, nomenclature follows Luther and
Sieff (1996).
Originally, this volume was planned as yet another of the familiar collections of contributed chapters published by specialists. However, something
closer to single authorship proved to be more conducive to an integrated
product – a volume that weaves together the many dimensions of
Bromeliaceae that affect where its members occur and how they interact
with other biota. For this book to warrant its title, more of the characteristics molded by natural selection than mentioned in the other monographs
of families must be described relative to effects on plant performance and
cast as products of natural selection, i.e., to the extent possible, set in environmental contexts.
Four authorities were asked to assist in the preparation of Chapters 7
and 9. One of these people, along with three additional experts, provided
what were retained of the formerly envisioned, more extensive set of specialized topics. Four of these chapters (10–13) give us a snapshot of the
more traditional approach to plant systematics and evolution as applied to
Bromeliaceae. They illustrate two issues worth the attention of botanists
contemplating work yet to do: (1) the extent of current taxonomic ambiguity and nomenclatural confusion in just four of the more than 50 bromeliad genera, and (2) the bases upon which authorities have circumscribed
taxa and attempted to infer phylogeny and identify the origins of key features like the absorbing trichome and impounding shoot.
This book is divided into three parts beginning with a short overview of
Bromeliaceae intended to set the stage for the following core of eight chapters devoted to vegetative and reproductive structure and function, ecology,
associations with other organisms, and finally evolution and phylogeny.
The third section presents the special topics. Together, these treatments
provide a detailed overview of how and why one family of flowering plants,
and a truly exceptional one by virtue of adaptive specialization to counter
xii
Preface
drought, came to assume such extraordinary importance in the Neotropics
and occupy so many kinds of often demanding ecospace. Clearly, the adaptive history of Bromeliaceae will continue to unfold as inquiry targeting
systematics, ecophysiology and ecology proceeds. Material provided in this
volume should promote future discovery by highlighting on-going controversies and identifying topics that seem especially ripe for further research.
Acknowledgments
My interest in Bromeliaceae began more than 45 years ago during a family
vacation in southeastern Florida. I recall how a colony of Tillandsia fasciculata bearing bright orange inflorescences and perched high in cypress
trees just across the street from our hotel beckoned while the surrounding
swamp prevented closer inspection. About a year later, back in Ohio, a
friend who had also visited Florida showed me an even stranger sight – an
air plant, he reported confidently – fully capable of living on air, hence quite
able to flourish tied to its burnished cypress knee suspended from the ceiling
of his enclosed porch. My skepticism about the fate of that forlorn T. paucifolia specimen and interest in bromeliads generally were forgotten until a
stint as a graduate student assigned to work at the University of Michigan
Botanical Gardens reintroduced me to those remarkable monocots. Much
of my research since that encounter has been devoted to Bromeliaceae and
the phenomenon of epiphytism so prevalent in this family.
Interest in Bromeliaceae has taken me through much of tropical America
and provided opportunity to work with all kinds of bromeliad enthusiasts
including a number of hobbyists who continue to make major contributions to bromeliad taxonomy. I am particularly grateful to members of this
dedicated group and the botanists who helped assure my success in field
work in remote parts of Brazil (Pedro Nahum, Elton Leme), Ecuador
(Calaway Dodson, David Bermudes), Venezuela (Tom Givnish) and
Mexico (Germán Carnevali), to name just a few. Members of the
Bromeliad Society and the Sociedade Brasileira de Bromelias are greatly
appreciated for their warm receptions on many occasions and frequent
encouragement of my work. I also wish to acknowledge assistance during
the production of this volume provided by Kaelyn Stiles.
Toni Renfrow, my research associate for more than 20 years, deserves
special recognition for assistance that ranged from the collection of data to
xiii
xiv
Acknowledgments
extensive record keeping and editing of most of my publications. I owe
more to her for my accomplishments in the pursuit of bromeliad biology
than to anyone else. A host of Oberlin College undergraduates worked with
me on many projects, more than a dozen sharing authorship of a larger
number of publications. Financial support for my work with bromeliads
has come from the United States National Science Foundation, the United
States Park Service, The National Geographic Society, Oberlin College,
and travel grants from a number of public and private sources in this
country and abroad. The Marie Selby Botanical Gardens and its staff have
been particularly helpful in providing support ranging from lodging to
greenhouse and library facilities.
Glossary
Accidental epiphyte A typically terrestrial species with occasional members
that grow to maturity while anchored on trees.
Anemochory The dispersal of seeds by wind.
Animal-assisted saprophyte A phytotelm bromeliad dependent on litter for
nutrients.
Ant-fed, ant-house bromeliad A species that produces hollow organs (myrmecodomatia) specifically for housing ant colonies.
Ant-nest garden bromeliad A species that regularly to exclusively roots in
arboreal ant nests.
Atmospheric bromeliad A species directly dependent on the atmosphere for
moisture and nutrient ions (member of Type Five).
Axenic Applied to trees that by nature do not support epiphytes.
Bromelioid An adjective applied to taxa assigned to subfamily
Bromelioideae.
CAM-cycling A photosynthetic syndrome characterized by diurnal CO2
fixation and nocturnal recapture of respired CO2.
CAM-idling A condition of stressed CAM plants that is characterized by
continuous closure of the stomata and energy maintenance through
internalized CO2 recycling.
Capacitance An aspect of water relations related to storage capacity.
Relative capacitance is expressed as change in RWC per unit change in C
(DRWC/DC).
Carton The composite material some ants and termites use to build their
nests and runways.
Chiropterophily Regular dependence on bats to disperse seeds or pollen.
Clade A group of species (lineages) that share a single ancestral lineage.
Cleistogamy The condition of a flower that promotes seed production
without presenting anthers or stigma to pollinators.
Decarboxylase An enzyme that catalyzes the release of CO2 from an
organic acid.
Diazotroph An organism capable of fixing N2.
xv
xvi
Glossary
Domatium (myrmecodomatium) A plant cavity regularly occupied by
nesting ants.
Earth soil Soil exploited by terrestrial flora (opposite of suspended soil).
Entomophily Regular dependence on insects to disperse seeds or pollen.
Epiparasite A parasite that taps its host via a fungus.
Epiphyll A nonvascular plant that inhabits the surfaces of foliage.
Eutroph A plant native to fertile substrates.
Everwet forest A forest that receives enough rainfall through the year to
support predominantly drought-sensitive vegetation (opposite of seasonal forest).
Facultative CAM Carbon fixation via CAM or C3 pathway depending on
growing conditions.
Facultative epiphyte A species that grows either epiphytically or rooted in
earth soil, often emphasizing one or the other habit at a particular location.
Frugivore A fruit-eating and often seed-dispersing animal.
Genet The product of a single zygote, one shoot with its roots for the nonbranching (monocarpic) bromeliad, or the potentially numerous
attached ramets produced by the sympodial (polycarpic) type.
Guild A group of co-occurring but not necessarily related species that
utilize one or more common resources.
Halophyte A plant native to saline habitats.
Haustorium The invasive appendage of a parasitic plant.
Hemiepiphyte A plant that accesses earth soil with roots for only part of its
life and anchors in a tree crown the rest of the time.
Homiohydry The condition of maintaining tissue water content relatively
independent of ambient humidity (opposite of poikilohydry).
Homoptera The taxonomic order of arthropods that includes plantsucking forms exemplified by aphids and scale insects.
Hypodermis A subepidermal zone of usually achlorophyllous, thin-walled,
collapsible water-storage cells in leaves.
Iteroparity The type of reproductive timing of a plant characterized by
repeated fruiting over as many seasons (polycarpy) rather than once as
in the monocarpic or semilaparous specimen.
Lineage The unbroken succession of generations that constitutes the
history of a taxon through geologic time.
Monocarpy The type of reproductive timing characterized by a single
episode of fruiting before the plant dies (semilaparity).
Myrmecochory The dispersal of seeds by ants.
Myrmecophyte A plant that regularly receives benefit from an associated
ant colony.
Neoteny A type of heterochrony whereby descendants as adults possess features that were characteristic of the juvenile stages of ancestors.
Glossary
xvii
Nitrogenase The enzyme complex responsible for reducing N2 to organic
form.
Nutritional piracy The process whereby epiphytes intercept nutrients
moving between the supporting tree crown and the forest floor.
Oligotroph A plant native to nutrient-deficient substrates.
Ornithochory Regular dependence on birds to disperse seeds.
Phorophyte A woody plant that supports vascular epiphytes.
Phytotelma The cavity formed by a plant to contain a phytotelmata.
Foliage plays this role in Bromeliaceae.
Phytotelmata A natural plant cavity filled with water often inhabited by
aquatic organisms.
Phytotelm bromeliad A bromeliad that produces a phytotelm.
Pitcairnioid An adjective applied to taxa assigned to subfamily
Pitcairnioideae.
Poikilohydry The condition of maintaining tissue water content at levels
strongly influenced by ambient humidity (opposite of homiohydry).
Ramet The individual offshoot or module of a sympodially branched, herbaceous plant.
Relative water content (RWC) A measure of water relations calculated as
fresh weight – dry weight/turgid weight – dry weight.
Reproductive index The proportion of the mature plant body committed to
seeds and associated reproductive tissue.
Rupestral A plant that grows on rocky soils.
Saxicole A plant that grows on rock (a lithophyte).
Sciophyte A plant tolerant of deep shade.
Sclerophylly The condition describing evergreen foliage that contains much
sclerified tissue.
Seasonal forest A forest characterized by one or more distinct dry seasons
(opposite of everwet forest).
Succulent The term describing stems and leaves much thickened to store
extraordinary amounts of water.
Suspended soil (humus) Soil-like rooting media suspended in the canopies
of many tropical and fewer temperate forests (opposite of earth soil).
Terrestrial bromeliad A species that typically roots on the ground (in earth
soil).
Tillandsioid An adjective applied to taxa assigned to subfamily
Tillandsioideae.
Transpiration ratio (TR) A coefficient produced by dividing the mass of
water lost in transpiration by the simultaneous gain in weight attributable to photosynthesis.
Trophic myrmecophyte See ant-fed, ant-house bromeliad.
Zoochory The dispersal of seeds by fauna.
Abbreviations
Amax
AR
chl
CAM
cpDNA
C3
C4
C3–CAM
E
g
H1max
MPa
MUE
PAR
PCRC
PEPc
PPFD
PPNUE
r
RH
RuBPc/o
RWC
TR
VAM
VPD
WUE
D
DH1
p
C
‰
Cleaf
maximum photosynthetic capacity
acetylene reduction as in the assay for nitrogenase
chlorophyll
crassulacean acid metabolism
chloroplast genome
Calvin/Benson photosynthetic pathway
Hatch and Slack photosynthetic pathway
facultative CAM
transpiration
diffusive conductance (leaf)
maximum acidification for CAM plants
megapascal
mineral-use efficiency
photosynthetically active radiation
photosynthetic carbon reductive pathway
phosphoenolpyruvate carboxylase
photosynthetic photon flux density
potential nitrogen-use efficiency
Malthusian coefficient
relative humidity
ribulose bisphosphate carboxylase/oxygenase
relative water content
transpiration ratio
vesicular-arbuscular mycorrhiza
vapor pressure deficit
water-use efficiency
carbon isotope ratio; 13C enrichment in parts per thousand
diurnal change in titratable acidity
solute potential
bulk water potential
parts per thousand
bulk leaf water potential
xviii
Part one
Brief overview
1
Introduction
Lower and middle Cretaceous Magnoliophyta remain too poorly known to
warrant definitive statements about many aspects of early angiosperm radiation (Taylor and Hickey 1992). Discovery of a compressed infructescence
purportedly from the Late Jurassic of east central Asia has recently
expanded its confirmed record (Sun et al. 1998), and raises the specter of
more fossils and better resolution ahead. Nevertheless, until this promise is
realized, answers to questions as fundamental as the habits (woody vs. herbaceous) of ancestors and the homologies of diagnostic organs (e.g., the
gynoecium) will remain speculative. One point germane to bromeliad
history is less equivocal: characteristic pollen and macrofossils indicate that
Liliopsida had emerged by the middle Cretaceous. However, evidence from
several quarters indicates that Bromeliaceae evolved later, and probably not
before the Tertiary.
Phytogeography also accords with youth that denied Bromeliaceae
opportunity to range beyond tropical America except for a single, probably
recent dispersal to west Africa (Fig. 1.1). Members of the three subfamilies
(sensu Smith and Downs 1974, 1977, 1979) and many of the larger genera
(e.g., Neoregelia, Hechtia) further suggest either exceptionally low mobility
(unlikely) or too little time to cross barriers breached by many other lineages. Nevertheless, most authorities (e.g., Cronquist 1981; Dahlgren et al.
1985) consider Bromeliaceae phylogenetically isolated among the extant
monocots, and a growing body of information on the organization of
several sequences of nucleotides within the chloroplast genome (e.g.,
Ranker et al. 1990; Terry et al. 1997a,b) supports this conclusion.
Uncertainty continues over which of the other Liliopsida are most closely
related to the bromeliads, particularly which family constitutes the sister
group, i.e., shares a common ancestor with Bromeliaceae.
Certain gymnosperms and the flowering plants considered primitive
3
4
Introduction
Figure 1.1. Geographic distribution of Bromeliaceae.
according to the paleoherb hypothesis challenge long-standing notions
about the nature of antecedents and the characteristics of the
Magnoliophyta that favored its ascent to unparalleled size and ecological
dominance among land flora. Hypotheses that zoophilous pollination and
certain additional aspects of reproduction drove the angiosperm radiation
to unparalleled heights must now accommodate discovery that most of
these same attributes occur (albeit in less advanced expressions) elsewhere,
especially among the gnetophytes (e.g., Friedman 1992; Kato et al. 1995).
Whether inherited as an older, intact suite of characters or derived piecemeal during the initial Lower Cretaceous expansion, these qualities alone
cannot fully explain the unprecedented success of the flowering plants.
Novel vegetative form and function were also important, as the bromeliads
so clearly demonstrate.
Rather than the woody archaetype (as exemplified by the ranalean magnoliophytes) posited by the euanthial theory, the angiosperm stock is
increasingly envisioned as low-growing shrubs to rhizomatous to scrambling herbs of moist, relatively disturbed (r-selecting), perhaps riverine,
habitats (e.g., Taylor and Hickey 1992). Rapid maturation made possible
by the combined effects of a novel nutritive tissue (endosperm), much
abbreviated (fast maturation) male and female gametophytes, and relaxed
Introduction
5
Table 1.1. Plant characteristics presumably responsible for the
unprecedented radiation of Magnoliophyta
Vegetative
(1) Cheap construction (herbaceousness)
(2) Rapid growth, potentially short life cycles
(3) Exceptionally efficient vascular systems
(4) Exceptionally diverse architecture (e.g., vines, herbs, trees)
(5) Exceptionally plastic ecophysiology (carbon fixation pathways, H2O balance
mechanisms)
(6) Exceptionally broad capacity to utilize diverse resource bases (e.g.,
parasitism, carnivory, and other sources of nutrients unavailable to other
flora)
(7) Exceptional chemical/mechanical defenses
Reproductive
(1) The flower as a reproductive organ of unmatched capacity for precise and
versatile function
(2) Unmatched capacity to manipulate pollinators
(3) Inexpensive, short-lived gametophytes
(4) Endosperm
(5) Devices to routinely screen male gametophytes (pollen tube competition and
various pollen recognition systems)
(6) Angiospermy and the associated possibilities for packaging seeds for
(6) protection and directed dispersal
needs for costly mechanical tissue probably account in large measure for
global dominance by the flowering plants (Table 1.1). These characteristics,
complemented by small size and versatile habits, account for the high densities of species in sites like humid tropical forests. Unmatched capacity to
manipulate pollinators and seed dispersers in turn probably spurred the
speciation necessary to stock the most densely packed modern communities. To what degree additional uniqueness, like angiospermy, which
permits the maternal parent to screen haploid genotypes, and greater
physiological variety (e.g., C4, C3 and CAM photosynthesis) influenced
outcomes remains more speculative.
Even though fossils and the geographic distributions of surviving lineages indicate phylogenetic youth, Bromeliaceae exceed many of the preTertiary clades (e.g., Fagaceae, Platanaceae, Juglandaceae) for number of
species and especially for adaptive variety (e.g., diverse habits, habitats).
Capacity to produce a simple, cheaply constructed, rapid-cycling body
varies among the magnoliophytes, and helps explain why some families
(e.g., Asteraceae, Poaceae, Orchidaceae) contribute more extensively to
angiosperm diversity than predominantly woody groups. Additional plant
6
Introduction
Table 1.2. Plant characteristics that account for the inordinate success of
Bromeliaceae in diverse, often demanding, habitats
Vegetative
(1) Small herbaceous body
(2) Rhizomatous habit
(3) Propensity for heterochrony/heterophylly
(4) Phytotelm shoot
(5) Foliar trichome capable of replacing absorptive roots and providing
additional services (e.g., light reflectance)
(6) Propensity for CAM, succulence and other xeromorphic features
Reproductive
(1) Less decisive for family success, although pollination and seed dispersal
(1) syndromes are diverse to match opportunities in disparate habitats
characteristics, such as the tight relationships between numerous orchids
and their high-fidelity pollinators and propensity to exploit underutilized
ecospace (e.g., forest canopy), in turn account in part for the different sizes
of the largely herbaceous clades. Although relatively modest by membership, perhaps because of weaker propensity for speciation, Bromeliaceae
exceeds these largest taxa for certain other kinds of biological variety, and
most certainly for importance to several kinds of fauna (e.g., mosquitoes).
Structure and function itemized in Table 1.1 largely account for the relatively high success of the flowering plants overall, while those traits listed
in Table 1.2 represent the finer-scale features that permit Bromeliaceae to
surpass most other families on several counts that at least equal species
richness as measures of biological importance. This family exhibits an
unusually propitious combination of angiospermous qualities and some
less pervasive ones conducive to life in widely available, underutilized and
often physically demanding ecospace. These more exclusive attributes at
once explain how one group of related species can be so ecologically versatile and stress tolerant, and also so often exceed co-occurring flora for
impacts in hosting ecosystems. Members tolerate punishing drought as epiphytes and lithophytes; the hardiest terrestrials may not experience rainfall
for months and, in the coastal deserts of northern Chile and southern Peru,
even for years, surviving solely on more reliable supplies of fog water (e.g.,
Figs. 1.2, 7.1).
Conversely, certain other bromeliads root in alpine bogs and additional
kinds of wetlands, and a few populations spend part of each year submerged in flowing water (Fig. 1.4G). Exposures vary from the UV-Benriched irradiance that prevails at .4000 m in the central Andes (Puya) to
Introduction
7
Figure 1.2. Bromeliads in situ. (A) Dyckia sp. growing in rocky soil of campos rupestres habitat in Minas Gerais State, Brazil. (B) Brocchinia tatei on marshy soil on
Cerro Neblina, Venezuela. (C) Alcantarea regina on granite outcrop in Rio de
Janeiro State, Brazil. (D) Large Aechmea angustifolia plant supporting diverse flora
in eastern Ecuador. (E) Hohenbergia sp. growing as a terrestrial in Bahia State,
Brazil. (F) Guzmania monostachia congregated in the lower crown of Annona glabra
in south Florida swamp forest. (G) Vriesea gigantea, a typical phytotelm bromeliad
in Espirito Santo State, Brazil. (H) Juvenile of Tillandsia streptophylla growing on
the base of Rhizophora mangle in Yucatán State, Mexico.
8
Introduction
the much attenuated photon flux under the canopies of evergreen forest
(e.g., various species of Cryptanthus, Pitcairnia; Fig. 1.3D). Frost-hardiness adequate for survival at certain temperate latitudes or in tropical
alpine habitats characterizes different sets of species. Access to key mineral
nutrients runs the gamut from the meager supplies that oblige pronounced
oligotrophy (e.g., the Tillandsia that clings to a small twig with its nonabsorptive roots; Fig. 1.3C) to relatively plentiful, for example the quantities
provided by symbiotic biota that process the litter intercepted by the phytotelm shoots of hundreds of ‘tank species’ (e.g., Fig. 1.2C,G).
Those qualities that grant Bromeliaceae exceptional tolerance for
drought and capacity to grow on nutrient-poor substrates required modifications of certain fundamental angiosperm features, but not of others.
Bromeliad flowers probably operate with roughly the same mix of breeding
systems and attractants for pollinators expressed across Magnoliophyta.
Pollen and seed dispersers, while also diverse, again seem unlikely to set
records for promoting speciation, ecological variety or dominance for
Bromeliaceae compared with other families. In effect, the bromeliads merit
special note among flowering plants for the novelty of the vegetative rather
than the reproductive characteristics of the most specialized species.
What poised ancestors for life in epiphytic, lithic and other sparsely vegetated (underutilized) habitats where more than half of the bromeliads reside
today was a body plan conducive to rapid cycling despite growing conditions
that limit carbon gain and thus diminish vegetative vigor and reproductive
power (Table 1.2; Figs. 2.1, 2.3). A remarkably adaptable leaf and shoot
assist resource scavenging (for water and nutrients) and promote stress-tolerance (to drought, high and low exposure). Propensities for neoteny and
specialized architectures that foster access to unconventional sources of
moisture and nutrients and promote economy during the use of these commodities also encouraged radiation into exceptionally stressful habitats.
An ecological taxonomy formulated by German morphologists and biogeographers over a century ago organizes the bromeliads according to
often unusual plant features that allow success in widely disparate kinds of
habitats (Table 4.2). Most important are aspects of roots, shoot architecture and the foliar trichome, which, depending on the mix of special modifications, favor carbon and water balance and mineral nutrition under
relatively conventional to extreme growing conditions. Some suites of characteristics foster epiphytism at relatively humid sites (Types Three and
Four), and another (Type Five), use of the same kinds of substrates in drier
regions. Five types are recognized in all, and references to specific bromeliads and groups of species hereafter will often employ these designations
Introduction
9
Figure 1.3. Bromeliads in situ (continued). (A) Tillandsia recurvata growing on telephone wires in southeastern Mexico. (B) Billbergia porteana growing on the trunk
of a palm in Bahia State, Brazil. (C) Tillandsia paucifolia growing on a cypress twig
in south Florida. (D) Cryptanthus bromelioides growing in the forest understory in
Rio de Janeiro State, Brazil. (E) Feral Ananas comosus in southern Venezuela. (F)
Aechmea nudicaulis extending out from a restinga ‘island’ along the coast of Rio de
Janeiro State, Brazil.
10
Introduction
Figure 1.4. Bromeliads in situ (continued). (A) Granitic dome (inselberg) covered
with lithophytic Bromelioideae in Rio de Janeiro State, Brazil. (B) Caatinga with an
understory rich in Bromeliaceae in Bahia State, Brazil. (C) Campos rupestres
habitat in Minas Gerais State, Brazil. (D) Elfin forest in eastern Puerto Rico. (E)
Restinga in Rio de Janeiro State, Brazil. (F) Remnant Atlantic Forest trees covered
with bromeliads in pasture in Rio de Janeiro State, Brazil. (G) A riparian colony of
Pitcairnia flammea in Rio de Janeiro State, Brazil. (H) Dwarfed cypress forest with
bromeliads in south Florida.
Introduction
11
(Table 4.2). Familiarity with this scheme is essential to understand bromeliad evolution and functional diversity.
Chapter 2 starts the eight-chapter core with a description of how sympodial branching combined with determinant shoots bearing adventitious
roots, or none at all, supports the bromeliads as hemiepiphytic vines, alpine
cushion or giant rosette plants, myrmecophytes, carnivores or soil-dependent terrestrials among an even longer list of habits (e.g., Figs. 2.2, 5.3B,
6.12D). Modifications of the shoot, and particularly its epidermis, impart
exceptional capacity to endure drought and impoverished substrates.
Tolerances for the multiple physical constraints that prevail in the most
exceptional habitats occupied by members of this family sometimes foster
almost exclusive occurrences there (e.g., Figs. 1.2C, 7.1E). Crassulacean
acid metabolism (CAM) promotes the water economy that helps many
populations survive seasonal drought and avoid photodamage, while
anchored on well-exposed bark and rocks. Similarly endowed relatives
utilize wetter habitats with the most vigorous individuals often located in
the shadiest microsites. In fact, CAM has been recorded in more members
of Bromeliaceae than in any other family (Martin 1994).
The nearly ubiquitous foliar trichome provides diverse services to
Bromeliaceae ranging from protection against potentially injurious insolation and insupportable transpiration through secretion to absorption associated with diverse nutritional modes and moisture supplies (Chapters 4
and 5; e.g., Figs. 2.5, 2.8). Bromeliaceae exceed all other families for variety
of sources of nutrients and water (Table 5.6). Foliar impoundments that
make litter an option for nutrition in turn assure the so-called phytotelm
types importance in communities far beyond what plant numbers or total
phytomass usually predict (Fig. 2.4). Dense populations of bromeliads in
forest canopies can also markedly influence fundamental system-wide processes and phenomena such as mineral cycling and hydrology.
Bromeliad taxonomy remains provisional, and needs substantial
improvement ranging from the reordering of species within many genera to
the establishment of additional higher taxa to accommodate revelations
fostered by accumulating molecular and traditional morphological data.
Smith and Downs’s three subfamilies include exceptionally isolated lineages (e.g., Brocchinia, Catopsis, Glomeropitcairnia; Tables 1.3, 1.4) in addition to core taxa, and many clades are almost certainly para- or
polyphyletic (e.g., Aechmea, Navia, Vriesea). Pitcairnioideae, while closest
to the monocot ground plan by many measures, including the status of the
trichome, basic plant architecture and reproductive morphology, is not, as
often reported, ancestral to either of the other two subfamilies.
12
Introduction
Table 1.3. Bromeliad diversity (number of species) across tropical America
Location
Colombia
Ecuador
Peru
Rio de Janeiro State, Brazil
Costa Rica
Florida
Venezuela
Bromelioideae Pitcairnioideae Tillandsioideae Total
70
56
59
170
27
0
56
125
70
153
17
19
0
188
196
242
199
124
145
17
120
391
368
411
311
191
17
364
Source: From Fontoura et al. (1991) and Holst (1994).
Bromelioideae and Tillandsioideae followed parallel evolutionary trajectories to become heavily epiphytic and dependent on foliar impoundments
and CAM. Certain other features diverged at least as much (e.g., fruit types,
reliance on foliar trichomes). DNA sequences are beginning to help align
and redefine the genera (e.g., Tillandsia/Vriesea), and should eventually
demonstrate how often, when, and under what conditions important
events, like the emergence of the absorbing trichome and CAM, occurred
during bromeliad history. Many aspects of vegetative structure and function are homoplasious (e.g., CAM, phytotelm shoot), as are most of the
many pollination syndromes recorded for the family.
Specialized Bromeliaceae, and some other flora from comparably
demanding habitats, inspired inquiry that helped launch the discipline of
physiological ecology during the late 19th century. Early functional
morphologists and biogeographers, including A. F. W. Schimper, C. Mez
and G. F. J. Haberlandt, firmly established the principle that plant function
tracks structure, and that both variables reflect growing conditions in situ.
Some of the most elegant examples came from experiments performed on
advanced Tillandsioideae, specifically those subjects labeled ‘atmospherics’
(Type Five; Table 4.2) because they rely on foliar trichomes to absorb airborne water and nutrients instead of the roots most land flora employ to
obtain the same resources from soil.
Major contributors since then include C. S. Pittendrigh (1948) who also
anticipated some of the discoveries of the current generation of ecophysiologists by postulating how plant habit and aspects of leaves and roots
account for the distribution of Trinidad’s bromeliads. His work also helped
validate the ecological classification provided in Table 4.2. Bromeliads
occupied a prominent place in Leopoldo Coutinho’s efforts in the late
1940s through the mid-1960s (e.g., Coutinho 1963) to demonstrate the
13
Introduction
Table 1.4. The bromeliad genera: selected statistics, ecological type and
geographic range
Genus
Number of Ecological
speciesa
type
Acanthostachys
Aechmea
Alcantarea
Ananas
Androlepis
Araeococcus
2
220
15
7
1
5
I
Mostly III
Mostly IV
II
III
I and III
Ayensua
Billbergia
Brewcaria
Brocchinia
Bromelia
Canistrum
Catopsis
Connellia
Cottendorfia
Cryptanthus
Deinacanthon
Deuterocohnia
Disteganthus
Dyckia
Encholirium
Fascicularia
Fernseea
1
62
2
17
49
11
21
5
1
42
1
14
3
120
30
5
2
I
III
I
I and IV
I and II
III
IV
I
I
I
II
I
I–II
I
I
I
I
18
I
2
IV
Fosterella
Glomeropitcairnia
Greigia
Guzmania
Hechtia
Hohenbergia
Hohenbergiopsis
Lindmania
Lymania
Mezobromelia
Navia
Neoglaziovia
Neoregelia
Nidularium
Ochagavia
Orthophytum
Pepinia
28
175
51
47
I and II
I and IV
I
III
1
36
6
9
95
3
95
54
3
26
48
III
I
III
IV
I
I
III
III
I
I
I
Geographic range
East central Brazil
Tropical America
Southeastern Brazil
South America
Central America
Southeastern Brazil
to northern South America
Guayanan Shield
Tropical America
Guayanan Shield
Guayanan Shield
Tropical America
Southeastern Brazil
Predominantly Mesoamerica
Guayanan Shield
Bahia and adjacent states, Brazil
Southeastern Brazil
Argentina and Paraguay
Mostly Bolivia
Guianas
Southeastern South America
Southeastern Brazil
Chile
Cerro Italia, São Paulo State,
Brazil
Predominantly west central
South America
Lesser Antilles, Trinidad and
adjacent Venezuela
Predominantly Andean
Tropical America
Predominantly Mexican
Mostly Jamaican and
southeastern Brazil
Mexico and Central America
Guayanan Shield
Southeastern Brazil
Andean
Guayanan Shield
East central Brazil
Southeastern Brazil
Southeastern Brazil
Chile (San Fernandez island)
Southeastern Brazil
Predominantly Amazonian
14
Introduction
Table 1.4. (cont.)
Genus
Number of Ecological
speciesa
type
Pitcairnia
Portea
Pseudaechmea
Pseudananas
Puya
Quesnelia
Racinaea
Ronnbergia
295
9
1
1
194
15
57
11
I
III
III
II
I
III
IV
III
Steyerbromelia
Tillandsia
Ursulaea
Vriesea
Werauhia
Wittrockia
3
518
2
227
64
12
I
I, IV, V
III
I, IV, V
IV
III
Geographic range
Tropical America
Southeastern Brazil
Colombia and Bolivia
Southeastern Brazil
Predominantly Andean
Southeastern Brazil
Mostly Andean
Panama to Peru,
Southeastern Brazil
Guayanan Shield
Tropical America
Mexico
Tropical America
Primarily Mesoamerica
Southeastern Brazil
Source: aFrom Luther and Sieff (1996).
mechanisms of photosynthesis among Neotropical epiphytes.
Bromeliaceae continue to attract investigators seeking more complete
answers to questions about carbon, water and nutrient balance, aspects of
reproduction, and phylogenetic relationships as detailed in the following
eight chapters.
Another set of pioneering biologists (e.g., Picado 1911, 1913) chose to
study this family because they recognized the importance of the bromeliad
phytotelmata to extensive fauna in many tropical American forests. Foliar
impoundments reportedly harbor high diversities and abundances of
aquatic and soil-type invertebrates, sometimes at densities above those
encountered in equivalent volumes of nearby forest soil (e.g., Paoletti et al.
1991; Fig. 8.15). Several more studies provide data on the physical and
chemical conditions in these microcosms, and yield insights on why certain
bromeliads host so many symbionts. Checklists indicate potentials for litter
processing and nutrient release comparable to those that prevail in more
conventional rooting media (Table 8.2). Broader perspectives suggest that
epiphytic Bromeliaceae, acting with certain other arboreal flora, intercept
and release key nutrients in ways that either augment or deprive co-occurring flora depending on conditions at the site (Fig. 7.18).
The eight-chapter core that follows these preparatory remarks also considers reproductive morphology, which, along with profiling the vegetative
Introduction
15
body, sets the stage to move on to basic life functions. Evolution is reserved
for the final installment. A modest third section contains short chapters
authored by specialists who treat several genera and the ethnobotany and
conservation of Bromeliaceae. As information continues to accumulate,
additional, specialized subjects will be able to be included in future
volumes, along with updates of the core chapters on basic structure and
function, ecology and family history.
Part two
Basic structure, function, ecology and
evolution
2
Vegetative structure
All of the impressive functional and ecological variety expressed by some
2700 species of Bromeliaceae is grounded on a single body plan, or what
Hallé et al. (1978) might consider one architectural model. Widespread
occurrence of this same design among extant monocots and the paleoherb
hypothesis (Taylor and Hickey 1992) suggest that early Magnoliophyta
possessed much the same basic organization. Except for the occasional
monocarp, a somewhat larger group of relatively caulescent species (Fig.
2.1), and another modest-sized assemblage of lateral-¯ owering taxa (Fig.
2.2B), the bromeliads share a distinctly modular bauplan characterized by
sympodial branching that leads to series of attached, compact, terminally
¯ owered ramets (Fig. 2.3). Roots, if present beyond the seedling stage,
mostly emerge along the lower half of each module.
Vegetative form that favors life on arboreal and lithic substrates also
imparts substantial horticultural value to many of the bromeliads.
Moreover, some of these same features assure exceptional importance in
ecosystems, including indispensability to extensive fauna with diverse needs
(Chapter 8). Two plant characteristics warrant special note on all three
counts: a generally compact, rosulate shoot (the ramet or module) that
often impounds moisture and nutrient-rich solids (creates the phytotelma
and consequently the phytotelmata; Fig. 2.4) and the usually peltate foliar
trichome (Figs. 2.5± 2.9). These attributes, combined with others involving
roots and shoots, favor success, including occasional dominance in some of
the most exacting kinds of ecospace colonized by vascular ¯ ora in tropical
America (e.g., Figs. 1.2C, 7.1).
Observations of the kind initiated by some of the most renowned of the
pioneering European morphologists constitute much of the vast literature
on Bromeliaceae. Contributions dealing with vegetative structure continue
and increasingly incorporate more revealing techniques, particularly
19
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20
Vegetative structure
Figure 2.1. Schematic diagram illustrating neoteny in Tillandsioideae whereby an
ancestor with mesomorphic foliage organized to maintain a phytotelmata gave rise
to descendants that lack phytotelm architecture and extensive root systems and
instead exhibit overall miniaturization combined with either reduced or increased
numbers of leafy nodes. All scale bars 51 cm. See text for additional details.
electron microscopy (e.g., Benzing et al. 1978) and histochemistry (e.g.,
Owen et al. 1988). Tomlinson (1969) devoted a substantial portion of
Volume 3 of the Anatomy of the Monocotyledons to the most recent review
of this information. We gratefully acknowledge the importance to our
treatment of Tomlinson' s synthesis and the growing body of related, interpretative information being amassed by plant physiologists and ecologists.
Our primary concern here is those aspects of vegetative structure that
distinguish Bromeliaceae among families (e.g., epiphytism) and foster
importance in ecosystems. Featured species showcase adaptive morphology, and, for example, illustrate how shoot architecture in¯ uences access to
Cambridge Books Online © Cambridge University Press, 2009
Vegetative structure
21
Figure 2.2. Bromeliad architecture. (A) Dyckia sp. in vegetative state. (B) Dyckia sp.
with lateral in¯ orescence. (C) Hemiepiphytic Pitcairnia sp. illustrating heterophylly.
(D) Neoregelia abendrothae ramets with only juvenile or juvenile and adult foliage.
(E) Brocchinia acuminata, sun (compact) and shade (caulescent) forms. (F)
Ronnbergia ecuadoriana illustrating putatively primitive architecture. (G)
Cottendorfia florida with leaves cut short to expose thick, ® re-resistant stem. (H)
Distichous Dyckia estevesii.
Cambridge Books Online © Cambridge University Press, 2009
22
Vegetative structure
Figure 2.3. Schematic diagram illustrating three patterns of growth in Bromeliaceae.
(A) Sympodial branching with determinant ramets. (B) Monocarpy. (C)
Monopodial with axillary ¯ owering.
resources that most plants obtain from soil. Finer details of carbon management, water balance and mineral nutrition are deferred to later chapters.
Likewise, taxonomy receives scant attention in this chapter except where
classi® cation happens to parallel form (e.g., foliar trichomes) that also
in¯ uences plant performance. In the ® nal analysis, our subject is how what
seems to be the fundamental monocot body plan, combined with often
novel arrangements and modi® cations of leaves, permits Bromeliaceae to
occur in most of the life zones comprising the American tropics.
Habits: general overview
Bromeliads range from small plants even by liliopsid standards to some of
the most massive-bodied of the monocots. More comparable among the
Cambridge Books Online © Cambridge University Press, 2009
Habits: general overview
23
Figure 2.4. Shapes of phytotelm (tank-producing) Bromeliaceae. (A± D) Four
arrangements of foliage that produce phytotelmata of different numbers, exposures
and depths per shoot. (E) Aechmea veitchii with virtually no impoundment capacity. (F) Carnivorous Brocchinia reducta. (G) Mature shoot of Aechmea bracteata cut
open to expose central dry chamber for ants and several older leaf bases con® gured
to intercept precipitation and litter. (H) Nidularium burchellii, discolorous foliage
arranged in a monolayer. (I) Tillandsia lucida, multilayered shoot. (J) Aechmea brevicollis, distichous phyllotaxis. (K) Billbergia porteana, tubular shoot. (L) Aechmea
brassicoides, central leaf forming dry chamber.
Cambridge Books Online © Cambridge University Press, 2009
24
Vegetative structure
Figure 2.5. Trichomes of Pitcairnioideae. (A± D) Goblet-shaped trichome of carnivorous Brocchinia reducta, illustrated in section (A), view from top (B), and labyrinthine outer wall of a distal cell in the hydrated (C) and dry (D) conditions. (E)
Fosterella penduliflora, in section. (F) Shield. (G) Brocchinia tatei, in section. (H)
Shield. (I) Brocchinia micrantha, shield. (J) In section. (K) Navia glandulosa, glandular trichome from sepal (left) and ¯ oral bract (right). (L) Uniserrate trichome
from juvenile leaf of Navia sp. (M) Trichome shield of Lindmania serrulata. (N)
Uniserrate trichome of Lindmania wurdackii. Parts E, F, L, M, N redrawn from
Tomlinson (1969).
rhizomatous types are the proportions of the individual ramets, or, for the
monocarp, just the seedling shoot because these species never branch (Fig.
2.3). The mature seedling and each of its subsequent ramets weighs from a
few grams fresh weight (e.g., neotenic Tillandsia and miniaturized
Brocchinia species; Fig. 2.1) to thousands of kilograms for those of the
Cambridge Books Online © Cambridge University Press, 2009
Habits: general overview
25
Figure 2.6. Trichomes of Bromelioideae. (A) Aechmea penduliflora, in section. (B)
Shield. (C) Billbergia brasiliensis, in section. (D) Shield. (E) Canistrum sp., in
section. (F) Shield. All parts redrawn from Tomlinson (1969).
largest sympodial types. Monocarpic Puya raimondii at maturity exceeds all
the other Bromeliaceae in mass and height and probably in the number of
years required for its unitary body to achieve ¯ owering size (Fig. 14.2C).
The individual bromeliad shoot typically consists of a short stem bearing
a few to many, closely placed, alternate, usually spirally arranged, strapshaped to ® liform leaves. Just two organs, one leaf and an enlarged prophyll, constitute each typically rootless ramet of neotenic Tillandsia
usneoides (Figs. 2.1, 2.10E). Hundreds of leaves characterize some of its
more caulescent relatives (e.g., monocarpic Puya, Tillandsia araujei).
Cryptanthus bromelioides and a number of other members of the same
genus bear smaller leaves along the rhizome compared with those at its
expanded terminus (Fig. 2.11C,D). Certain Bromelia and similarly stoloniferous members of many additional bromelioid genera exhibit even
stronger dimorphism, as do many Pitcairnioideae (e.g., Pitcairnia; Figs.
2.2C, 2.12B). Slender juvenile leaves appear on the shoot of Neoregelia
abendrothae before the broader utriculate organs that can trap litter and
water develop (Figs. 2.2D, 9.12). Heterophylly is less pronounced in
Tillandsioideae where, nonetheless, it has provoked more speculation about
evolutionary mechanisms (Fig. 2.11B; Chapter 9).
Leaf size and proportions, particularly the shape of the base and number
per shoot, in¯ uence ecophysiology and accordingly the suitability of speci® c substrates and climates for certain bromeliads. Phyllotactic fractions
range from 2/5 to 5/13 and probably go higher among the caulescent species
Books Online © Cambridge University Press, 2009
26
Vegetative structure
Figure 2.7. Trichomes of Tillandsioideae. (A± B) Trichome of Tillandsia ionantha
showing con® guration of shield when dry (A) and wet (B). (C) Rigid trichome
shield of Tillandsia bulbosa, abaxial surface. (D) Trichome shield of Tillandsia
crocata. (E) Trichome shield of Tillandsia recurvata. (F) Trichome shield of
Tillandsia karwinskyana. (G) Trichome of Catopsis nutans, in section. (H) Shield.
(I) Leaf of Tillandsia hildae showing banding attributable to presence of trichomes
distinguished by the widths of the shields. Parts D, G, H, redrawn from Tomlinson
(1969).
that bear numerous narrow leaves (e.g., Tillandsia funckiana, T. filifolia;
Fig. 2.1). However, even the most congested foliage of this type casts little
self-shade except where the blades are imbricate.
Overlapped leaves along the tiny shoots of caulescent Tillandsia bryoides
¯ ex outward most while the plant is fully hydrated (Fig. 2.1). Other exceptional taxa exhibit distichous organization (Dyckia estevesii, T. usneoides,
Cambridge Books Online © Cambridge University Press, 2009
Habits: general overview
27
Figure 2.8. Abaxial leaf surfaces of representative Bromeliaceae; scanning electron
micrographs. (A) Aechmea bracteata (3150). (B) Catopsis nutans (3150). (C)
Tillandsia tectorum (3100). (D) Pitcairnia macrochlamys (3150). (E) Tillandsia
ionantha (3175). (F) Bromelia sp. (3150).
Books Online © Cambridge University Press, 2009
28
Vegetative structure
Figure 2.9. Ontogeny of the trichome of Tillandsia usneoides viewed in section (A
series) and from top (B series). Redrawn from Billings (1904).
T. recurvata; Fig. 2.2H). Occasionally, patterns shift from spiral to distichous along the same shoot (e.g., T. paleacea), or they approach the orthodistichous condition (leaves two-ranked in a slight spiral; e.g., T. myosura).
Distichous phyllotaxis is more common among seedlings, especially in
Tillandsia subgenus Diaphoranthema, where in the adult it denotes juvenilization.
Axillary buds occur along the entire length of the typical bromeliad
shoot, but few ¯ ush and, except for the lateral-¯ owered species, those that
do produce the standard one or two reiterative ramets (Fig. 6.14). Some of
the longer-stemmed saxicoles (Tillandsia diaguitensis) and certain scrambling Pitcairnia species (Fig. 2.12B) branch less predictably, possibly
according to physiological status or some external cue like photoperiod.
Pitcairnia riparia branches whenever its stolons encounter obstructions
that block forward progress. Replacement meristems routinely activate following ¯ oral induction that culminates shoot development with as few as
one (Fig. 3.3L) to thousands of ¯ owers arrayed on a well-de® ned in¯ orescence (Figs. 3.2± 3.4).
Leaves with armed margins characterize most Bromelioideae, and many
Pitcairnioideae, presumably to discourage large herbivores (Figs.
2.12± 2.14). The epiphytes usually display weaker mechanical defenses than
the terrestrials, which if native to arid soils (e.g., certain Bromelia, Hechtia)
invest most heavily in spines. Most bromeliads can replace a lost apical meristem with an axillary bud, but apparently regeneration proceeds slowly
enough and predation is sufficiently high in many habitats to justify high
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Habits: general overview
29
Figure 2.10. Plant architecture and leaf anatomy of representative Tillandsioideae.
(A) Tillandsia usneoides, leaf cross-section. (B) T. recurvata, leaf cross-section. (C)
T. setacea, leaf cross-section. (D) T. crocata, leaf cross-section. (E) T. usneoides,
shoot. (F) T. usneoides, cross-section leaf vein. (G) T. usneoides, cross-section leaf
epidermis. (H) T. recurvata, cross-section leaf epidermis. (I) Catopsis floribunda, leaf
cross-section. (J) Tillandsia fasciculata, leaf cross-section. (K) T. fasciculata,
stomata. (L) T. duratii illustrating leaves capable of holdfast. (M) T. ionantha var.
van-hyningii (saxicole). (N) T. ionantha var. zebrina (epiphyte). Parts A± D, F± K
redrawn from Tomlinson (1969).
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30
Vegetative structure
Figure 2.11. Asexual propagation and related morphology. (A) Tillandsia flexuosa
with immature axillary ramet and additional offshoots on spent in¯ orescence. (B)
Grass-like basal ramets produced by many soft-leafed Vriesea species. (C± D)
Stoloniferous Cryptanthus sp., mature ramet (C) and immature ramet (D). (E)
Stoloniferous Nidularium lymanioides growing as a hemiepiphyte.
cost to protect the shoot tip. Soft-leafed exceptions include some
Cryptanthus species in Bromelioideae and Brocchinia and Fosterella of
Pitcairnioideae; according to certain sequences in the chloroplast genome
these genera lie beyond the core taxa of their respective subfamilies (Fig.
9.20). Unexpectedly well-defended foliage born by members of some arboreal Bromelioideae (e.g., Aechmea bracteata; Fig. 2.4G) raises the possibility of recent ancestors that rooted on the ground.
Sympodial Bromeliaceae branch at different locations along the parent
axis depending on the species (Fig. 6.14). Buds inserted at midstem or
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Habits: general overview
31
Figure 2.12. Growth habits, rhizome bracts and foliage of certain Pitcairnioideae.
(A) Drought-deciduous Pitcairnia heterophylla. (B) Scandent Pitcairnia riparia.
(C) Pitcairnia sp. equipped with rhizome bracts lacking armature below green
foliage with expanded blades. (D) Pitcairnia sp. bearing short, spiny basal leaves
that progressively give way to smooth-margined, broader and longer photosynthetic types. (E) Single leaf of nonheterophyllic Pitcairnia feliciana. (F) Swollen leaf
bases and bulb-like habit of Puya pusilla.
somewhat below suffice for most taxa. Two sets of ramets, the ® rst quite
small, grass-like and positioned near the base of parent shoots that themselves are still much less than ® nal size, characterize numerous
Tillandsioideae (e.g., some Vriesea species; Fig. 2.11). Later, after the
mother ramet begins to ¯ ower, one or two more robust offshoots emerge
from as many leaf axils midway along the shoot to just below the in¯ orescence. Still other species fail to branch the second time (e.g., Alcantarea
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32
Vegetative structure
Figure 2.13. Aspects of leaves of Bromelioideae. (A) Spiny blade margins of
Bromelia balansae. (B) Cross-section of blade of Bromelia balansae half way
between apex and base illustrating collapsible adaxial hypodermis, stomata and
stellate chlorenchyma. (C) Aechmea magdalenae, abaxial epidermis. (D)
Hohenbergia urbanianum, cross-section of blade. (E) Portea petropolitana, section
revealing nonvascular ® ber bundles. (F) Leaf silhouettes illustrating four patterns
of anthocyanin development (dark areas) common in Neoregelia and encountered
less often in several other genera. Parts B± E redrawn from Tomlinson (1969).
imperialis, Puya dasylirioides; Chapter 6), rendering them essentially monocarpic. Basal ramets in these instances exist primarily to continue the genet
should the seedling meristem fail to mature.
Exceptional Tillandsioideae and some Orthophytum augment sympodial
branching with offshoots where ¯ owers failed to set fruits (Fig. 2.11).
Location suggests origin from buds in the axils of ¯ oral bracts that for most
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Habits: general overview
33
Figure 2.14. Aspects of shoots and roots of Bromeliaceae. (A,B) Shoot of Bromelia
sp. sectioned and intact illustrating dense masses of trichomes on leaf bases and
absence of substantial impoundment capacity. (C) Holdfast roots of Tillandsia
edithiae. (D) Abundant apogeotropic roots exposed by removing the leaf bases of
caulescent Brocchinia micrantha. (E) Stoloniferous epiphytic Neoregelia sp. (F)
Aechmea chantinii illustrating banded distribution of trichomes on abaxial leaf
surface. (G) Banded pigmentation marking the leaves of Vriesea fosteriana. (H)
Billbergia sp. illustrating irregular spotting on foliage.
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Vegetative structure
species remain dormant unless activated by injury farther up the in¯ orescence. Monopodial types progressively die from the rear forward at the
same time as the shoot apex adds replacements, including a succession of
lateral in¯ orescences (e.g., Tillandsia complanata, some Dyckia, Greigia;
Figs. 2.2B, 2.3C). Inspection of certain reputed cases of monopody (e.g.,
Tillandsia multicaulis) reveals the usual sympodial condition that leaf-like
bracts obscure when the replacement meristem arises immediately below
the spent apex.
Exceptional sympodial bromeliads representing all three subfamilies
spread via axillary stolons up to several meters long that propagate above
or below ground depending on the taxon (e.g., Cryptanthus, Pseudananas;
Fig. 2.11D). Quite a few Pitcairnia, certain Cryptanthus and many
Tillandsia, among others, possess more upright, leafy, caulescent habits
(Fig. 2.12). Some of these plants (e.g., Nidularium lymanioides; Fig. 2.11E)
scramble through the lower canopy as hemiepiphytes following establishment on the ground, or they germinate in the canopy and then grow from
branch to branch (e.g., Pitcairnia riparia; Fig. 2.12B).
Extensive, ® brous root systems characterize all Bromeliaceae except the
most diminutive, dry-growing Tillandsioideae. Less typical for Liliopsida,
each organ travels basipetally from its point of origin inside the stem
through many nodes before emerging to penetrate adjacent substrates (Fig.
2.15). Mycorrhiza occur sporadically, but few reports identify the fungi and
none document a plant bene® t (Chapter 5). Sclerotic cortical and stelar
parenchyma provide the strength and durability the slow-growing epiphytes and saxicoles require for prolonged suspension. Absorptive capacity
probably varies among taxa and within genotypes according to growing
conditions, especially the suitability of substrates.
Bromeliad leaves develop from basal meristems much like those of most
monocots, but mature organs differ among and within genotypes (e.g., Fig.
2.12). Three types of heterophylly, that probably serve as many different
purposes as described below, occur through the family. Several
Pitcairnioideae rely on synchronized abscission to coordinate leaf displays
with the availability of moisture (Fig. 2.12A), and channeled blades with
in¯ ated, tightly clasping bases (ligulate leaves) mark the bromeliads with
phytotelm shoots (Fig. 2.4). The nonimpounders appear more grass-like, or
their leaves possess prominent midribs (Fig. 2.2F). Petiolate foliage similar
to that of some dicots can confuse all but the experienced collector (e.g.,
several Bromelia and Cryptanthus species; Fig. 2.12). Pronounced succulence distinguishes some taxa (e.g., Dyckia, dry-growing Tillandsia; Figs.
2.10A± D, 2.13B), whereas much thinner blades signal accommodation to
humid sites (e.g., Catopsis, Ronnbergia; Fig. 2.17A).
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Habits: general overview
35
Figure 2.15. Root and stem structure characteristic of many members of
Bromeliaceae.
Leaf color is exceptionally vivid and varied among the bromeliads, and
trichomes often further ornament foliage. Anthocyanins and chlorophylls
in many patterns set off the broad, ¯ at leaves of numerous Type Four
species (e.g., Vriesea fosteriana; Fig. 2.17B). Foliar indumenta range from
con¯ uent to sparse and from relatively ® ne to coarse textured. Alternating
bands of densely and sparsely covered leaf surfaces can produce striking
displays (e.g., certain Cryptanthus species, Aechmea chantinii; Figs. 2.14F,
2.18C). Importance to leaf moisture and ion and energy exchange vary
according to the amount of leaf area these appendages insulate, certain
specializations of their living stalk cells and the shape, mobility and other
aspects of the shields (Tables 2.1, 9.1).
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Vegetative structure
Figure 2.16. Aspects of the leaves of Pitcairnioideae. (A) Puya raimondii, crosssection of blade half way between base and apex illustrating stomata, trichome and
details of the mesophyll. (B) Cross-section of blade of Pitcairnia trianae illustrating presence of a palisade. (C) Cross-section of blade of Pitcairnia pungens showing
its undifferentiated chlorenchyma.
Organization for foraging
Evolutionary ecologists and ecophysiologists consider the typical rhizomatous herb as much a collection of closely related, interacting individuals
as one plant. Most bromeliads more than a few years old ® t this de® nition
because by this age they consist of several to hundreds of meta-individuals, viz. ramets, modules or `sympodial units' which originate, mature and
die as subordinated parts of a genetic individual (genet). Modules organized in this fashion act collectively to exploit patchy environments for
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Organization for foraging
37
Figure 2.17. Aspects of the leaves of Tillandsioideae. (A) Catopsis floribunda, crosssection of blade cut half way between apex and base illustrating anatomy of vein
and stomatal apparatus. (B) Representative patterns of anthocyanins displayed by
many soft-leafed Tillandsioideae and the presence of transverse commissures
linking the parallel veins of some species. Part A redrawn from Tomlinson (1969).
resources, respond to co-occurring biota, reproduce, and pass genes on to
future generations.
More than the plant with a more discrete body (e.g., a tree), bromeliads
and other ¯ ora with equivalent architecture exemplify how coordinated
growth in lieu of animal-like mobility grants capacity to maximize resource
capture and avoid certain localized hazards in heterogeneous, basically
two-dimensional habitats. Like other clonal herbs, qualities that help determine how effectively the sympodial bromeliad harvests nonrandomly
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Vegetative structure
Figure 2.18. Leaf pigmentation. (A) Neoregelia sp. with red-tipped foliage. (B)
Guzmania lindenii. (C) Cryptanthus sp. with horizontal bands of prominent trichomes. (D) Vriesea erythrodactylon with deeply cyanic leaf bases.
distributed commodities include branching angle, the numbers and locations of meristems, ramet life span, and plant capacity to utilize connected
modules as integrated physiological sources and sinks.
Bell et al. (1979) questioned why Y-type branching and only a few angles
of divergence among the much larger number possible characterize so
many plants, including Bromeliaceae, with horizontal (plagiotropic) rhizomes and orthotropic (upright), determinant ramets (Fig. 2.3A).
Apparently, branch angles above 60° (120° between two daughter axes)
allow such ¯ ora to maximize returns on resources committed to foraging,
i.e., to theoretically exploit the greatest amount of space per unit of
invested biomass (Fig. 2.19 pattern A). Additional species follow either of
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Organization for foraging
Table 2.1. Aspects of bromeliad trichome structure and related functions
Associated qualities
of trichome
Function
Occurrence in the family
(1)
Retard transpiration
and reduce heat
load and
photoinjury
Densely overlapping
re¯ ective shields,
especially abundant on
abaxial surfaces
All three subfamilies
(2)
Absorption of H2O
and nutritive ions
Stalk cells alive and
equipped with dense
organelle-rich
protoplasts, shields
various, wettable shield
Primarily
Tillandsioideae and
Brocchinia, leaf bases in
phytotelm
Bromelioideae
(3)
Deterrent to
predators and
pathogens
Structure ranges from
the peltate type that
protects the underlying
softer tissue to the
potentially bodypuncturing uniseriate
appendages of certain
Pitcairnioideae
Probably all three
subfamilies
(4)
Attraction of
pollinators
Peltate types that form
dense indumenta that
re¯ ect dim light from the
in¯ orescence
Possibly common among
night-¯ owering
Tillandsioideae, e.g.,
T. streptophylla
(5)
Attraction of seed
dispersers
As above but densely
investing ¯ eshy fruits
(Fig. 3.5G)
Bat-dispersed
Bromelioideae (e.g.,
Billbergia porteana) but
probably uncommon in
family
(6)
Secretion
(A) Possibly
digestive
enzymes to
process prey
(B) Deterrent to
predators
Stalk and shield cells
equipped with dense
organelle-rich
protoplasts
Uniseriate with
glandular distal cell
(Fig. 2.5K)
Brocchinia reducta and
B. hechtioides
Navia glandulosa,
Ronnbergia petersi
two more options that produce different architectures according to Bell and
Tomlinson (1980; Fig. 2.19 patterns B and C). Option two features a 45°
angle that, should every meristem survive, results in an octagonal instead
of a hexagonal grid. Option three (Fig. 2.19 pattern C) promotes linear
arrays of ramets. However, before moving on we need to consider why most
rhizomatous plants deviate from inherent patterns.
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Vegetative structure
Figure 2.19. Three patterns of branching that occur among rhizomatous herbs that
in¯ uence plant foraging for light, water and mineral nutrients.
Two conditions, one fundamental to plant geometry based on the hexagonal grid and the other a characteristic of all but the exceptional twodimensional environment, oblige ¯ ora with creeping, modular bodies to
depart from the ideal con® guration. Figure 2.19 (pattern A) illustrates how
a rigid branch angle of 60° would cause certain pairs of same-generation
ramets to overlap after just three iterations. Unevenly distributed resources
further oblige capacity to deviate from a grid pattern to achieve costeffective foraging. Finally, several additional considerations complicate
architectural analysis for such plants, especially Bromeliaceae.
Bromeliads and other similarly organized herbs determine the sizes and
shapes of the spaces they ® ll with leaves and roots by regulating meristem
vigor, number and location. Speci® cally, they enhance resource harvest by
concentrating appropriate organs where photons, water and nutrient ions
occur most abundantly. Effective foraging in heterogeneous space requires
opportunistic growth, essentially capacity to selectively invade enriched
patches of habitat and avoid or minimize investments in others that offer
lesser rewards. Targeting and coordination in turn oblige sensory capacity
and communication among connected modules. Some meristems thrive as
the genet expands while support for others that occupy less propitious
microsites diminishes because of poorly understood, plant-mediated economic analysis and response.
Clonal herbs tend to express either `guerrilla' or `phalanx' -type growth
depending on the relationship between plant architecture and foraging
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Organization for foraging
41
strategy. Both patterns represent evolutionary adjustments to frequently
encountered arrays of resources in situ. The ramets of guerrilla-type plants
grow variable distances before they branch (e.g., scandent Pitcairnia
riparia; Fig. 2.12B). Conversely, plants with phalanx-type architecture ® ll
horizontal space more systematically with ramets that grow as advancing
fronts. Greater opportunism characterizes the guerrilla-type plant given its
superior capacity to place roots in widely dispersed patches of fertile, moist
soil and chlorenchyma in far-¯ ung light gaps. So deployed, biomass yields
greater returns in photosynthate, water and key ions than if invested more
equitably or randomly among attached ramets.
Architectural models tend to distinguish the bromeliads according to the
nature of their substrates. The epiphytes, for example, usually produce
compact clones (phalanx strategy?) compared with certain terrestrials (e.g.,
Tillandsia vs. certain Bromelia species), which instead forage more widely
across typically more expansive soils. Saxicoles often range over more space
than their close epiphytic relatives (Bennett 1991; Chapter 6), but not
without exception. Lithophytic Abromeitiella (Deuterocohnia) lorentziana
iterates numerous small ramets connected by short stolons to achieve the
dense, self-insulating cushions that allow it to exploit protected exposures
on the leeward sides of rocks in cold, windswept, south Andean habitats.
Similar form under more benign conditions in culture demonstrates genetic
control over architecture. Aechmea nudicaulis var. aequalis (Fig. 7.13C)
along with some other natives of restinga habitats exhibits a linear array of
ramets (guerrilla strategy?), perhaps to assist growth out from under the
shade of the shrubs required for establishment. So far, Neoregelia pauciflora
alone represents Bromeliaceae among ¯ ora assigned to a recognized model
(modi® ed hexagonal; Bell et al. 1979).
Bell and Tomlinson' s (1980) three models for clonal herbs lend themselves to numerical analysis, which if considered in additional detail might
increase insights on the adaptive architecture of Bromeliaceae. However,
® ndings elsewhere probably need to be modi® ed to interpret conditions
among the more leaf-dependent species. At least as important for foraging
to these bromeliads is the shape of the shoot and the location there of functions most plants perform with roots. Shoots of Types Three, Four and Five
Bromeliaceae exhibit a bewildering variety of sizes and proportions (e.g.,
Fig. 2.4) that affect foraging in ways accorded fuller coverage below and in
Chapters 4 and 5.
Further inquiry might also target possible additional relationships
between architecture and physiology vs. microtopography and the distributions of light, water and nutrients in space. Resource allocation, including
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42
Vegetative structure
Figure 2.20. Schematic diagram illustrating plausible evolutionary relationships
among eight derived body plans and the more fundamental rhizomatous architecture characteristic of many monocots.
translocation and source/sink relationships, needs to be compared among
the attached ramets of clonal Bromeliaceae that exhibit relatively ¯ exible
growth and routinely occupy broader expanses of substrate (e.g., many
Neoregelia species, Pseudananas) than Abromeitiella and most of the epiphytes. Finally, relationships should be considered between architecture
and plant characteristics unrelated to foraging. Body plan complements
many aspects of natural history in other ¯ ora (Bell and Tomlinson 1980).
For example, species characterized by densely clonal genets more often
exhibit self-incompatibility than those with relatively dispersed ramets.
Plants with scattered vs. aggregated shoots may attract fewer predators by
virtue of lower apparency and so on.
Relationships of the body plans
Figure 2.20 illustrates how the body plan of a putative, sympodial ancestor
with a nonimpounding, rosulate shoot and extensive absorptive roots
relates to the eight additional arrangements exhibited among extant
Bromeliaceae. Many Pitcairnioideae (e.g., Fosterella, Pitcairnia) conform
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Relationships of the body plans
43
to what this scheme presumes to be the basic family condition. Degrees of
caulescence and root development, branching pattern, and many characteristics of foliage differentiate the eight derived arrangements, each of
which includes additional, ® ner-scale variation (not shown) among the
qualifying species. Roots diminish relative to shoots in ® ve of the eight
directions, paralleled by increased plant dependence on absorptive foliage.
Stems become more prominent in all three of the remaining directions.
Neoteny shaped the outcome in the case of the most specialized of the eight
architectures.
Aspects of habitats, and especially the nature of the substrate (stability,
utility as a source of moisture and nutrients), correlate with body plan.
Beginning on the right, sparsely branched, weakly determinant, xeromorphic shoots bearing reduced root systems (e.g., Tillandsia araujei; Fig. 2.1)
describe many of the dry-growing lithophytes (Chapters 6 and 9). Even
longer-stemmed forms featuring relatively drought-sensitive, often heterophyllic foliage and more roots reside in humid forests as vines and hemiepiphytes (direction two; e.g., Pitcairnia riparia; Figs. 2.2C, 2.12B). Arid,
relatively stable rooting media in the high Andes, that limit productivity
and permit extended life spans respectively, support bromeliads with two
more architectures. In addition to the cushion arrangement (direction
three) that grants Abromeitiella insulation from cold, desiccating wind, a
tuberous partially subterranean stem affords similar advantage under
somewhat less demanding circumstances to members of the Puya tuberosa
complex (direction four). Species with similarly swollen stems tolerate ® re
in rupestral habitats (Fig. 2.2G).
Monocarpic Puya (direction ® ve) illustrate the other, over-represented
condition (giant rosette type; Fig. 14.2C) at high elevations in which a
single leafy shoot constitutes the entire, long-lived genet. Woolly indumenta, compact shoots and a massive body prevent precipitous cooling as
ambient temperatures drop below freezing at night (Figs. 7.2± 7.4). An even
more palm-like habit evolved in Brocchinia, speci® cally in B. paniculata and
B. micrantha (direction six). Both of these species occupy wet, often densely
vegetated sites below 2000 m where a stout, unbranched, tall stem supporting a crown of water-impounding foliage favors gap-phase regeneration
(Givnish et al. 1997).
Neotenic Tillandsioideae, especially those native to arid and/or cool
regions, deviate most from the basic bromeliad bauplan (direction eight).
Roots develop sporadically, if at all, on adults. Shoots may be exceptionally leafy (Tillandsia bryoides) or sparsely foliated, just one absorptive leaf
and a single enlarged prophyll per ramet in T. usneoides (Fig. 2.1).
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Vegetative structure
Ancestors probably possessed the rosulate, water and debris-impounding
(phytotelm) shoot that continues to characterize most Tillandsioideae
(direction seven). Similar shoot form emerged in Bromelioideae and
Brocchinia (Pitcairnioideae).
Closer inspection of the individual subevents (directions) underlying the
family-wide radiation just described more precisesly reveals how
Bromeliaceae colonized so many kinds of often stressful habitats and can
utilize diverse sources of moisture and mineral nutrients. Speci® cally, these
smaller arrays of more closely related body plans illustrate how modi® cations of stems and foliage, and accordingly, the relationships between these
two kinds of organs, fostered major shifts in ecology. The sequence within
Tillandsioideae mentioned above and illustrated in Figure 2.1 constitutes
the most revolutionary among the component radiations because it
required fundamental reorganization of the shoot and root systems via
heterochrony. Powerful constraints peculiar to epiphytic and other extreme
habitats provided the impetus.
Pitcairnia and several related genera demonstrate that modi® cation of
the vegetative body need not be as fundamental as that experienced by neotenic Tillandsioideae to equip the resultant lineages for life under diverse,
and in some instances extreme, growing conditions. In this case, multiple
options were realized by stock that probably possessed determinant shoots
bearing congested foliage of a fairly generalized monocot type. Indeed,
perhaps the prototype for this radiation and that for the entire family were
identical. Moreover, this subevent was earth-based in the sense that descendants, like their antecedents, rarely anchor in any but terrestrial substrates
and root development remains substantial.
Evolution leading to architectures suitable for substrates ranging from
bare rock to more accommodating riparian soils and the moisture supplies
and irradiances prevailing in deep forest to open, semiarid, hot to cold habitats occurred simply by modifying the form, physiology and longevity of
leaves, degrees of foliar dimorphism, and the frequency at which the stems
supporting these appendages branch. None of the more extreme modi® cations that elsewhere (directions seven and eight) permit shoots to impound
moisture and solids or allow foliage to serve in lieu of absorbing roots
emerged here.
All but a few species comprising this land-based, pitcairnioid radiation
possess the familiar liliaceous, sympodial body plan expressed in the form
of serial ramets bearing foliage of various textures and forms that may or
may not abscise as the blades senesce (Figs. 2.3A, 2.12). Rhizomes clad with
nonphotosynthetic, bract-like leaves characterize these taxa as they do the
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Relationships of the body plans
45
rest of the genus and many other Bromeliaceae. But enough variation
occurs despite these shared characteristics to differentiate plant performances and accordingly, oblige correspondingly distinct growing conditions. Rhizome appendages of Pitcairnia andraeana, P. tabuliformis and
their kind lack spines as do the more distally inserted appendages designed
for photosynthesis rather than protection (Fig. 2.12C). Relatively mesomorphic blades die back from the tip (e.g., P. tabuliformis), or senesce more
evenly (e.g., P. andraeana).
Additional body plans that emerged during this pitcairnioid radiation
feature a few (the short-stemmed taxa) to many (the stoloniferous species)
abbreviated, persistent, spiny organs below others equipped with welldeveloped, smooth-margined green blades (Fig. 2.12A,B). A group of
short-stemmed, heteroblastic taxa exhibit progressively expanded and
smoother-margined appendages between the spiny bract-like and much
more expanded, unarmed photosynthetic types (Fig. 2.12D). Populations
equipped with short ramets often grow on exposed rocks and cliffs: those
with longer shoots sprawl over the ground or climb trunks as hemiepiphytes (e.g., P. riparia; Figs. 2.2C, 2.12B). Deciduous green leaves shed prior
to ¯ owering during the dry season distinguish Pitcairnia heterophylla from
most members of the short-stemmed group (Fig. 2.12A).
Typically short ramets featuring relatively long-lived, thick (often CAMequipped) foliage with marginal spines form the basis for still more habits
suitable for exposed, exceptionally arid sites. Pitcairnias that most closely
approach this description resemble certain of the generally more xeromorphic members of Dyckia, Hechtia and Encholirium (Fig. 2.2A,B).
Somewhat thinner, but still well-armed, leaves that die back rather than
abscise during the dry season identify Pitcairnia feliciana as a transitional
species that perhaps ® ts more comfortably within this group than the previous one (Fig. 2.12E).
Puya takes the putative prototypic body plan into two more adaptive
zones. Short ramets with swollen bases essentially render P. pusilla (Fig.
2.12F) and its kind hemigeophytes, while tall, thick, unbranched stems
qualify P. raimondii as a giant alpine rosette type (Fig. 14.2C). The ® rst
architecture favors reliance on the rooting medium for insulation. Massive
stems containing substantial stored moisture and dense crowns of succulent foliage offer the same protection from severe climate to plants that
conform to the second body design. Relationships between habit and
ecology receive additional consideration below and as parts of the discussions of heterochrony in Chapters 5 and 9, and the operation of the phytotelm shoot in Chapter 7. The balance of this chapter and Chapters 4 and 5
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Vegetative structure
and parts of Chapter 7 detail the modi® cations of leaves, roots and stems
that underlie the exceptional functional and ecological diversity of the bromeliads.
Stems
Leafy stems, except for those produced by the most reduced, neotenic
species, share similar monocot-type anatomy (Fig. 2.15; Chapter 12).
Typically, a narrow cortex-like layer is differentiated into two zones, the
outer one occupied by thick-walled, ligni® ed cells. Thinner-walled, sometimes starch-laden parenchyma constitutes the inner region, which lies
against the central cylinder and is separated from it by sclerenchyma of
various descriptions. Periderm-like (storied) tissue formed by periclinal
divisions of cells, derived from the apical meristem rather than a true phellogen, may develop at different depths below the epidermis, sometimes discontinuously, on older axes and under wounds and leaf scars. Bromeliads
also lack vascular cambia, and although the exceptional axis thickens considerably (e.g., the larger Puya species), it does so without any unusual
mechanism con® rmed so far. Reports (e.g., Harms 1930) that a cambiumlike cylinder occurs in the perennial (multiple crops of ¯ owers; Fig. 3.4J)
in¯ orescence axis of Deuterocohnia meziana need con® rmation.
Stem vasculature is complex in most Bromeliaceae in part because roots
accompany the bundles typically present there. Leaf traces enclosed by suberized `endodermis-like' (Krauss 1948± 49) sheaths intermingle with the still
embedded roots, and both entities travel through many nodes before entering a leaf base or, in the case of the root, departing from the stem (Fig.
2.15). Additional vasculature originates beneath each axillary bud.
Collateral bundles representing fused series of leaf traces (sympodia),
again often with robust sheaths, occur more densely nearer the edge than
the center of the central cylinder (e.g., Ananas comosus; Krauss 1948± 49).
Tissue vascularizing the stem of the most diminutive Tillandsia, including T. usneoides, forms an almost solid sclerotic core containing scattered
phloem strands and a few narrow tracheids probably because CAM and
reliance on foliar trichomes rather than roots greatly reduce the need for
water transport. Flux mostly occurs over short distances, primarily from
wetted leaf surfaces to adjacent parenchyma, and, for structurally less
reduced relatives with a differentiated mesophyll, from water stored in the
hypodermis to more desiccation-sensitive chlorenchyma during drought
(Chapter 4; Fig. 2.13B).
Mucilage accumulates in schizolysogenous cavities within the stems and
in¯ orescence axes of many bromeliads, particularly Tillandsioideae.
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Stems
47
Exudation accompanies certain kinds of injury and may explain Picado' s
(1913) report that digestive secretions elaborated by some Costa Rican
natives enhance the utility of phytotelmata for carnivory. His hypothesis
remains untested and improbable; more likely, these products deter predators, enhance drought-tolerance, or constitute carbohydrate reserves.
Ergastic inclusions in stems include silica bodies in the epidermis and
raphide sacs, especially in cortical cells adjacent to the intracauline roots.
Bromeliad stems exhibit tropisms consistent with conditions encountered in situ. Shoots produced by phytotelm Bromeliaceae that frequently
germinate under branches and along vertical surfaces always grow upright.
Sometimes just the in¯ orescence assumes this orientation among the nonimpounding species (Fig. 1.3C). Shoots of `stemless' taxa (e.g., Tillandsia
ionantha; Fig. 2.10M,N) lack sufficient length to respond to gravity while
not all of the caulescent forms that could, do so (e.g., T. schiedeana). Stem
shape also varies among taxa. Seedling axes and those of ramets often
become obconical as the apical meristem enlarges during growth.
Especially notable are the expanded, corm-like rhizomes of Puya tuberosa
and Cottendorfia florida (Fig. 2.2G), and on an even grander scale, the massively upright axes of monocarpic Puya raimondii (Fig. 14.2C).
Elongate stolons mark many of the soil-rooted and lithophytic
species, especially terrestrial Bromelioideae (e.g., Bromelia, Nidularium,
Pseudananas) and the hemiepiphytes (Pitcairnia; Figs. 2.2C, 2.12B), but
only the occasional epiphyte (e.g., Vriesea espinosae). Shoots of additional
soil-based types sprawl across the ground or grow up into low vegetation
(e.g., some Orthophytum, Cryptanthus), as do the offshoots produced on the
spent in¯ orescences of several tillandsias (Fig. 2.11). A basal constriction
promotes vegetative dispersal by encouraging the ramets of certain
Cryptanthus to disarticulate after becoming large enough to grow independently. Mobility fostered by re¯ exed foliage leading to spherical form may
encourage the detached ramets of certain species to roll and root well away
from parents (e.g., C. acaulis).
Ramets typically survive for 3± 4 years, while the seedling shoot (especially those of the monocarps) requires additional time to accumulate the
resources necessary to reproduce (Fig. 2.3). One or two seasons pass before
the average ramet ¯ owers, and seed crops ripen over additional months to
another year. Natives of stressful habitats (e.g., Abromeitiella, Tillandsia
hildae) cycle more slowly than plants less tolerant of physical stress
(Chapter 4). Daughter ramets receive photosynthate and residual N and P
and perhaps other useful constituents from their declining parents.
Concentrations of N, P and K among the attached ramets of T. paucifolia
collected in south Florida diminished with age, reaching lowest values in
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Vegetative structure
senescing, post-fruiting shoots (Benzing and Renfrow 1971a; Benzing and
Davidson 1979). Leaching from moribund foliage probably denies daughter ramets equal opportunity to recycle relatively labile K compared with
N and P.
Roots
Bromeliad roots exhibit features consistent with their frequent role as holdfasts. Figure 2.15 illustrates the pronounced scleri® cation responsible for
the uncommon durability and mechanical strength of those axes characteristic of many of the epiphytes and saxicoles. Note also the absence of
morphological loss; every tissue (primary phloem and xylem, endodermis
and pericycle) is present along with a root cap. The cortex is often
differentiated with the interzone accounting for most of the volume of the
root and much of its strength. Krauss (1948± 49) reported a thick-walled
endodermis in pineapple, but this physiologically decisive tissue is less
robust elsewhere (e.g., Billbergia sanderiana).
Type Five Bromeliaceae (Table 4.2; Chapter 12), including Tillandsia
ionantha, lack root hairs or soon lose them; conditions among the other
dry-growing forms remain largely undocumented. Roots of the more mesic
Bromelioideae and Pitcairnioideae produce abundant hairs as seedlings, as
does adult pineapple (Krauss 1948± 49; Fig. 3.8). Roots and shoots grow
episodically in culture, faster early in the growing season than later. Harms
(1930) reported a progressive loss of vascularity with increasing epiphytism
until phloem in strongly neotenic Tillandsioideae is greatly reduced and
only tracheids remain to transport water. Cheadle (1955) con® rmed
Harms' s ® ndings, noting tracheids exclusively in the roots of several Type
Five Tillandsia species and vessel elements with scalariform end plates in all
the other examined specimens of this description.
Roots originate in the previously mentioned `dictyogenous' zone within
about 1 cm of the shoot apex in pineapple (Krauss 1948± 49; Fig. 2.15).
Intrusive growth proceeds downward for many more centimeters before the
elongating organ emerges from the stem through relatively soft tissue at a
node. Cross-sections of older axes reveal darkly pigmented intercauline
roots that sometimes occur at sufficient densities to almost ® ll what appears
to be a true cortex. Unlike the rot-resistant, cable-like roots of the xerophytes, those of the bromeliads restricted to moist soils exhibit less robust
structure and probably more effectively absorb moisture and nutrients
(Chapter 5).
Unlike a number of aroids, orchids and other ¯ ora that produce one type
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Roots
49
of root for anchorage and another for absorption, roots of the typical bromeliad share the same structure although function may differ according to
location. Krauss (1948± 49) recognized `axillary' and `soil' roots depending
on where the organ originated along the parent shoot and, more importantly, where it emerges from the stem. Many species with rudimentary phytotelmata (e.g., Type Two Ananas and Bromelia) produce an extensive
system of axillary roots to explore adjacent leaf base chambers.
Compaction ¯ attens those organs that penetrate the deepest recesses of the
shoot. Soil roots in turn extend 1± 2 m beyond the base of a pineapple at
depths up to 85 cm when media permit (Krauss 1948± 49). Abundant roots
ramify through the remnants of the old leaf bases of arborescent
Brocchinia micrantha to intercept nutrient-charged ¯ uids over¯ owing from
the debris-laden bases of younger, intact foliage (Fig. 2.14D).
Bromeliads native to certain kinds of substrates exhibit matching root
growth. Anchorages oblige ageotropism among the Type Five bromeliads,
many of which regularly germinate on the undersides of branches after being
deposited there by stem ¯ ow. Thigmotropism occurs at least as widely and
involves taxa representing all three subfamilies. Brighigna et al. (1990)
reported abundant accumulations of a protein/polysaccharide mixture in the
caps of the roots that secured some Tillandsia latifolia and T. macdougallii
specimens to substrates. Free roots lacked this hydrophilic material as did the
exposed sides of the adhering organs, suggesting importance for holdfast.
Bromelioideae, and Tillandsioideae even more, rely on foliage for
absorption, although anchorage remains essential to all but stoloniferous
Spanish moss and scattered relatives with additional alternatives like the
curling, twig-grasping leaves of Tillandsia duratii (Fig. 2.10L). Root
systems serving neotenic Tillandsioideae diminished more than those of
related lineages as ancestors colonized increasingly arid habitats and
unyielding substrates (Fig. 2.1). Although the epiphytes and saxicoles alike
possess substantially reduced root systems, what remains of these organs
suggests different requirements to utilize bark compared with rock.
Several polymorphic taxa (e.g., T. ionantha varieties ionantha and vanhyningii; Fig. 2.10M,N) make the most compelling case for substrate-speci® c differentiation. Lithophytic types produce long, scarcely branched
roots, usually one each from widely scattered nodes along leafy caulescent
shoots. The epiphytes root more profusely, but each ramet remains relatively short except for a few small-bodied species like T. tricholepis and T.
capillaris. But even these bromeliads usually root to a single spot, namely
where their seeds happen to germinate.
Opportunity to promote cost-effective foraging by rooting largely on an
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Vegetative structure
as-needed basis varies among Bromeliaceae. Extreme emphasis on shoots
constrains participation for many Tillandsioideae, especially the essentially
rootless members of Type Five as just described. Substrates can have
greater in¯ uence elsewhere. Moist, compared with less accommodating,
media stimulate root development in a wide variety of cultivated
Bromelioideae, particularly Type Three and Four stock that as epiphytes
and saxicoles often grow on comparatively barren substrates (Table 4.2).
Capacity to strike ® ne roots from rhizomes or along thicker exploratory
roots should bene® t populations native to rocks and other substrates that
sequester moisture and nutrients in scattered, relatively inaccessible locations. Temporal variations in moisture supply can have similar effects.
Media utilized by many Dyckia and Hechtia species, among others, dry out
and recharge seasonally (e.g., Fig. 7.1E). But if the rapidly developed `rain
roots' of certain cacti and other desert-dwellers also exist in Bromeliaceae,
they remain unreported.
Vascular cells
Cheadle (1953, 1955) included 28 species representing all three subfamilies
of Bromeliaceae in his study of tracheary element evolution in Liliopsida.
Relatively narrow components, both vessel members and tracheids, occur
through the family, but ® ner structure varies among taxa and often differs
from one type of organ to another in the same plant (Fig. 2.21).
Bromeliaceae were judged moderately advanced and the subfamilies
roughly equivalent in evolutionary grade on the basis of tracheary
advancement. Water-vascular cells tend to be either similar to or less
advanced in stems, in¯ orescence axes and foliage compared with roots, a
pattern Cheadle (1953) ascribed to the monocots in general. Cross-sections
of the more robust foliar veins reveal many small and usually two broader
tracheary cells; fewer elements comprise the lesser veins (Fig. 2.17A). Many
species lack protoxylem lacunae in part probably because internodes are
short and growth is slow. Closer inspection of the in¯ orescence axes, some
of which elongate several centimeters per day and rise through phytotelmata, might reveal exceptions. The generally narrow sieve tube elements
look much like phloem parenchyma in transverse view (Fig. 2.17A).
Cheadle conducted his survey before certain agencies that in¯ uence the
hydraulic architecture of plants were recognized. Aspects of xylem tissue,
especially the dimensions of its conductive cells, probably re¯ ect current
growing conditions and related plant needs more faithfully than those experienced by ancestors if these conditions differ. Not surprisingly, Pitcairnia
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Vascular cells
51
Figure 2.21. Representative water-vascular cells in the vegetative body of
Bromeliaceae. (A) One end of the type of tracheid widely distributed through the
family. (B) Vessel element with multiperforate end plate that also occurs in most
Bromeliaceae. (C) Vessel element in root of Pitcairnia sp. illustrating the most
advanced structure for tracheary function present in the family. Redrawn from
Cheadle (1955).
alone of the surveyed taxa exhibited vessel elements with transverse, simple
perforate plates (Fig. 2.21). Members of this genus feature some of the
most mesomorphic foliage described so far for Bromeliaceae, organs that
oblige substantial streams of moisture to support relatively vigorous transpiration and photosynthesis (Chapter 4). Narrower cells lacking end walls
(tracheids) or vessel elements with multiperforate end plates characterized
the rest of the sample (Fig. 2.21).
Xylem strands made up exclusively of tracheids, or vessel elements with
multiperforate rather than uniperforate end plates, seem best suited for
most Bromeliaceae because so many species use water sparingly and succulence is so common (Table 4.1). So what can tracheary anatomy tell us
about the evolutionary status of the family and the relationships among its
species? Cells that just happen to ® t Cheadle' s de® nition as primitive probably resist cavitation by reason of the same supposedly archaic structure.
On the other hand, xylem tensions recorded for Bromeliaceae have always
been low, although most records come from succulent types that by virtue
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Vegetative structure
of this circumstance rarely, if ever, experience sufficient dehydration to
rupture water columns in xylem capillaries (Chapter 4; e.g., Fig. 4.18).
Clearly, Cheadle' s story remains incomplete.
A biophysical critique mindful of the relationship between xylem
anatomy and hydrodynamics is needed to explain why tracheary cell structure differs in the root vs. the stem and leaf of the bromeliads and
Liliopsida in general. Is Cheadle' s (1953) hypothesis supported, or do the
environments of these organs and the demands placed upon them by the
rest of the plant differ enough to explain his ® ndings without recourse to
evolutionary history? How does tracheary cell morphology among the
monocots, and the bromeliads in particular, relate to hydraulic demand and
the maintenance of capillary integrity (safety) in different organs of the
same plant and among species adapted to different growing conditions?
Foliage
Like liliopsids generally, all but the exceptional bromeliad emphasizes
foliage over stems and roots in the sense that leaves constitute the bulk of
the vegetative body. However, Bromeliaceae exaggerate this condition even
among the monocots because so many of the functions usually relegated
either to shoot or root so often operate together. Accordingly, leaf shapes
and textures indicate mode of resource capture and required growing conditions more conspicuously in this family than in most others.
Unfortunately, signi® cance was ignored by most of the anatomists who
described bromeliad foliage, in part because the tools and perspectives were
not available to address them. Foliar trichomes received inordinate attention on those few occasions when inquiry encompassed structure and
related function.
Low to moderate speci® c weights (leaf mass/unit surface area) and broad
and relatively glabrous and ¯ at surfaces usually signal shade-tolerance and
drought-sensitivity among the bromeliads. Conversely, thicker, enrolled
organs with more water storage and mechanical tissue and a denser indumentum denote life in more exposed, drier ecospace (Figs. 2.10, 2.13, 2.16,
2.17). But some confounding characteristics preclude more precise predictions. For example, McWilliams (1974) reported fresh/dry weight ratios of
5.98 and 17.06 for Puya mariae and Fosterella penduliflora to support his
suggested existence of succulent and nonsucculent `strategies' in
Pitcairnioideae. In fact, the second species sheds its leaves during the dry
season as be® ts a drought-avoider. Among tested Tillandsioideae, species
with thin, lightly trichomed foliage (e.g., Guzmania lingulata) and others
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Foliage
53
with unequivocal Type Five status (e.g., Tillandsia usneoides) yielded similarly low ratios. A reading of 13.00 for evergreen, drought-enduring Dyckia
brevifolia further indicates how poorly this measure re¯ ects growing conditions in situ.
Aspects of leaf margins and indumenta parallel certain taxonomic boundaries, provide information about relationships within subfamilies, and
sometimes also indicate the habits (e.g., epiphytic vs. terrestrial) and ecotolerances (e.g., to exposure, to drought) of individual populations.
Bromelioideae, especially Bromelia and certain Pitcairnioideae (e.g.,
Dyckia, Hechtia), feature strongly serrate-margined foliage while
Tillandsioideae never do (Figs. 2.2, 2.13A, 2.17). Presence of members
equipped with either unarmed (e.g., Brocchinia, Fosterella) or armed foliage
(most of the rest of the genera) accords with Pitcairnioideae as the evolutionarily broadest of the three subfamilies without denying that some of its
lineages possess what are probably the least derived of the body plans
extant within Bromeliaceae.
Trichome organization varies most among Pitcairnioideae; Bromelioideae come next. Trichome structure, which is remarkably concentric, and
its consistency clearly distinguish Tillandsioideae from the rest of the
family (Figs. 2.5± 2.8). However, other patterns are more ¯ uid, such as trichome density and the shapes of the shields that sometimes also vary
across the same leaf (Figs. 2.7I, 2.14B,F). Evolutionary polarity is often
obscure. Strehl (1983) concluded from her survey of 100 species that
adaxial trichomes exhibit more advanced organization than those on the
other side of the leaf. Scales on the leaf bases of phytotelm types supposedly feature less `conservative' characteristics than those born nearer the
apex, but Strehl provided no compelling rationale to support these conclusions.
Closely imbricated, utriculate leaves create the impoundments emblematic of phytotelm Bromeliaceae and lend a uniquely tropical American
aspect to the heavily colonized forest (Fig. 1.4F). The same architecture
accounts for an important resource base for symbiotic biota dependent on
aquatic media and/or moist detritus (Chapter 8). A derived condition
endows a group of smaller-bodied relatives (e.g., Tillandsia bulbosa) with
dry cavities to house plant-feeding and possibly plant-protecting colonies
of ants (Fig. 8.5). Channeled blades often direct precipitation and litter to
the axils of the phytotelm types; those of the myrmecophytes roll abaxially
to conserve moisture and better expose the green mesophyll to shade-light.
Although one or the other condition characterizes many species, a few
additional taxa (e.g., Aechmea bracteata, Brocchinia acuminata; Figs. 2.2E,
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Vegetative structure
2.4G) provide both kinds of living space, presumably with plant bene® ts
expanded accordingly.
Long petioles that increase shade-tolerance and perhaps impart other
advantages distinguish a variety of understory Bromelia, Cryptanthus,
Disteganthus, Ronnbergia and Pitcairnia species (e.g., Fig. 2.12B).
Otherwise similar foliage with ensheathing bases displayed as a rosette
would intercept less light, i.e., self-shade more. Luther (personal communication) concluded from observations in wet Andean habitats that laminae
held well above the stem help a number of terrestrials to avoid overgrowth
by bryophytes and other creeping ¯ ora (e.g., Ronnbergia deleonii). Two
additional features increase capacity to maintain upright foliage: corrugation adds considerable strength to a strap-shaped leaf according to Krauss
(1948± 49; Figs. 2.13, 2.16), as does a channeled compared with a ¯ at blade.
Pigmentation
Some of the most prized Bromeliaceae owe their popularity to ornamental
foliage, which growers have enhanced by selection (e.g., Vriesea fosteriana
chestnut; Fig. 2.14G). Several functions probably underlie these displays,
and some widely grown Tillandsioideae could be used to test hypotheses
(e.g., concolorous and heterochromic V. splendens var. formosa vs. var. splendens; Table 4.11). However, most displays characterize entire populations,
for example the horizontal bands of chlorenchyma underlain by similarly
con® gured patches of cyanic, abaxial epidermis that mark Vriesea fosteriana and several of its relatives. Guzmania equals Vriesea for ornate markings, including narrow, vertical pin stripes of anthocyanin-laden epidermis
extending from leaf base well up into the blade (e.g., Guzmania lingulata).
Diverse ¯ ora adapted to the shade cast by evergreen tropical forest (e.g.,
Vriesea simplex, Nidularium burchellii; Fig. 2.4H) share discolorous foliage
purportedly to recycle photons off the `red mirror' provided by an anthocyanin-laden abaxial epidermis and back into the overlying chlorenchyma
(Lee et al. 1979). A different explanation probably applies to the intricately
marked leaves just described for other Bromeliaceae because these appendages occur in more densely overlapping, self-shading con® gurations (e.g.,
Fig. 2.18B). Perhaps also signi® cant, these stiff-leafed plants, like all
Bromeliaceae, lack capacity to sun-track or reorient in some other manner
to avoid overexposure. Carbon budgets and security for cryptic detritivores
might be improved as well (see below) by the presence of the irregular zones
of chlorophyll-rich mesophyll backed by a cyanic epidermis illustrated by
Vriesea fosteriana (Chapter 4).
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Foliage
55
Additional Tillandsioideae display similar jagged arrays of deeper and
lighter-pigmented chlorenchyma, but without the red re¯ ectors (e.g.,
Vriesea hieroglyphica). Both arrangements suggest conditions elsewhere
that accompany unusual physiology (e.g., the C4 syndrome in other families, C4± CAM in some Peperomia species). If true, ultrastructure, especially
of the deeper green chlorenchyma and associated vascular tissue, should
reveal it. Suberized bundle sheaths or unusually large numbers of characteristically aligned plastids and mitochondria in chlorenchyma associated
with the commissures that always course through the deepest green zones
could indicate a CO2-concentrating mechanism (Fig. 2.17B). Unrecognized
variety probably exists in the photosynthetic apparatus of the bromeliads,
perhaps more than minor variations on common themes; the ornately pigmented Tillandsioideae appear to be the best candidates for interesting discoveries.
Ornamentations beyond those just described fall into several more categories. A deep purple to maroon epidermis on both sides of the leaf bases
of many phytotelm types (e.g., Vriesea erythrodactylon, numerous
Bromelioideae; Fig. 2.18D) should bene® t the dark-colored detritivores
that these plants need to process impounded litter; broken patterns may
more effectively obscure the silhouettes of lighter-colored residents.
However, not every display prompts an equally plausible explanation.
Those irregular interspersions of pigmented and achlorophyllous patches
that mark certain Bromelioideae (e.g., Billbergia sanderiana; Fig. 2.14H)
occur above the phytotelmata where their presence confers little apparent
advantage to tank occupants. Conceivably, herbivores avoid foliage so
marked, choosing instead food sources free of the appearance of competing folivores, perhaps leaf miners in this case (Fig. 8.2B).
Still another category of Bromeliaceae includes the species with eyecatching, red-tipped foliage (e.g., numerous Neoregelia and fewer
Nidularium species; Fig. 2.18A) that warrant the label `bulls eye' bromeliads. Viewed from above, the intensity (density) of the signal increases
toward the shoot center where otherwise poorly advertised ¯ owers and
fruits reside. Certain Hohenbergia and Wittrockia species along with
members of still other bromelioid genera exhibit similar to more expansive
patches of red or orange at the same locations. Up to one-third of the distal
ends of the leaves of Aechmea pectinata remain bright pink while the dull,
strobilate in¯ orescences display similarly inconspicuous ¯ owers. Several
Tillandsioideae also bear apically pigmented foliage combined with nondescript ¯ oral bracts that in some cases subtend bat ¯ owers (e.g., Vriesea bituminosa).
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Vegetative structure
Young leaves that color up or become chlorotic just prior to anthesis
characterize a second group of bromelioids also notable for their short
in¯ orescences (Fig. 3.2A). Several Brazilian Neoregelia (N. nivea, N. lactea)
and some navias attract pollinators by highlighting their ¯ owers with scattered white light. Should leaf bases remain albinistic, seed dispersers may
become the targets, which for Brazilian Bromelioideae include birds and
¯ ying and nonvolant mammals (Chapter 6). The same parts of many more
species become bright red (e.g., Neoregelia macwilliamsii) prior to anthesis,
while the foliage of still another group of taxa (e.g., N. petropolitana) is permanently green (Fig. 2.13F). Experiments and more data on plant visitors,
colors during reproduction, and other signals (e.g., Vriesea fosteriana
chestnut), and fruit qualities are needed to characterize the reproductive
syndromes of bromeliads. Speci® c displays may exist to promote pollination and seed dispersal in some cases and in others encourage the transport
of just one of these plant products.
Heterophylly
Bromeliads exhibit three kinds of heterophylly, each one associated with
additional plant characteristics. Leaf form changes but once during
ontogeny (typical heteroblasty) in two instances, whereas a third assemblage of species produce leaves of different morphology episodically
along stoloniferous shoots (e.g., certain scandent Pitcairnia; Fig. 2.2C).
A group of short-stemmed Pitcairnia exemplify the ® rst pattern. Recall
that each ramet of P. heterophylla initiates growth with tough, persistent
scale-like blades or modi® ed leaf bases armed with a sharp terminal and
multiple, marginal spines (Fig. 2.12A). A few transitional organs follow
until the vulnerable, linear, deciduous appendages emerge coincident
with renewed rainfall. Dormant or leafy, older specimens probably avoid
consumption by all but the most determined grazers. Conditions reminiscent of this same two-stage sequence involving short, spiny juvenile
foliage and equally persistent, laminate leaves characterize a host of relatives that routinely access more continuous supplies of moisture (Figs.
1.4G, 2.12D).
Pitcairnia riparia produces stiff, armed nonphotosynthetic organs until
the slender ramet swells preparatory to the emergence of a heteroblastic
series of more elongate green leaves (Fig. 2.12B). Contact with some physical impediment seems to stimulate this conversion. Relatively narrow
organs then precede broader, more distinctly petiolate foliage as the maturing shoot prepares to ¯ ower. Numerous members of Bromelioideae (e.g.,
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Foliage
57
Bromelia, Quesnelia) also bear tightly imbricated, scale-like leaves along all
but the apices of stoloniferous ramets.
As noted above and illustrated in Figure 2.12, Pitcairnia (sensu lato)
exceeds the other bromeliad genera for varied foliage that includes pronounced heterophylly, and, for the adult-type photosynthetic leaf, texture
ranging from semisucculence as exempli® ed by species such as P. tabuliformis to the much thinner, and more seasonal, appendages of P. heterophylla
(Fig. 2.12A). Pitcairnia feliciana combines drought-deciduousness (blades
shrivel simultaneously over a period of a few weeks rather than cleanly
abscising as in similarly seasonal P. heterophylla) with unexpectedly thick
(expensive) blades armed up to about one-third of the distance from the
base with stout marginal spines (Fig. 2.12E).
Many phytotelm Tillandsia and Vriesea (Type Four) illustrate the type of
heterophylly responsible for inspiring considerable speculation on an
important aspect of bromeliad evolution (Chapter 9; Figs. 2.1, 2.11B).
Compared with adult-type foliage, leaves born on seedlings and the precocious grass-like offshoots featured by quite a few mesic Tillandsioideae
(Table 4.7) exhibit stout morphology and lepidote (trichome-covered) surfaces that promote water storage and economical use in lieu of the phytotelmata that eventually relax requirements for these two attributes (Adams
and Martin 1986a,b,c; Reinert and Meirelles 1993). Gas exchange demonstrates more precisely how aspects of water and carbon balance shift as
plants mature.
Young and mature specimens of Tillandsia deppeana, one of the two
heterophyllic species examined, took up CO2 only during the day, indicating no change in photosynthetic pathway during ontogeny. However,
responses to drought and water supply varied with the life stage (Adams
and Martin 1986a; Fig. 4.9). If we can judge by T. deppeana, the seedlings
of tank-bearing Tillandsioideae more closely approach the ecophysiological performances of juveniles and the adults of the more specialized tillandsioids (Type Five) than their own phytotelm-equipped stages. Certain
Bromelioideae exhibit similar, although less exaggerated, heterophylly as
illustrated by some Nidularium species (Fig. 9.12).
Form and function exhibited by the juveniles of heterophyllic
Tillandsioideae that also characterize the adults of their Type Five relatives
suggest two possibilities. First, Type Five lineages evolved via heterochrony
from relatively mesic ancestors like Tillandsia deppeana (Chapter 9; Fig.
2.1). Alternatively, the seedlings of these otherwise mesophytic species
simply recapitulate the characteristics of drier-growing antecedents. In
either case, heterophylly remains adaptive, i.e., heavily trichomed, succulent
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Vegetative structure
juvenile shoots satisfy on-going need to accommodate the drought imposed
on epiphytes and saxicoles by high exposure and nonabsorptive substrates,
even in humid regions.
In essence, habitats wet enough to permit the adult to expend water at
the high rate required to grow vigorously nevertheless constitute veritable
deserts for the much smaller, hence structurally more constrained (less
favorable surface to volume ratio; Fig. 4.17), juvenile. Slow growth obliged
by the kind of xeromorphy peculiar to shoot-dependent and predominantly epiphytic Tillandsioideae must precede the opportunity for faster
growth that becomes possible only after foliar impoundments develop.
Life history
Leaf life spans among the magnoliophytes range from just a week or two
to many years, more or less according to the economic/evolutionary paradigm used to interpret a variety of plant characteristics (Chapter 4).
Limited data suggest that Bromeliaceae conform to the same rule ± that leaf
longevity correlates with cost and varies inversely with photosynthetic
capacity (Amax). Investments considered in these calculations include
expenditures to build and maintain biomass. Thickness and scleri® cation
in¯ uence the caloric value of foliage on a surface area basis.
Thin, broad and supple, hence relatively cheap, leaves such as those born
by many Type Four Tillandsioideae live about a year, while the more expensive, succulent and less productive and consequently more slowly amortized
foliage of their dry-growing relatives survives longer. Not surprisingly, speci® c leaf weights (mass/surface area) probably reach family-wide lows in
deciduous Pitcairnia and Fosterella. Nitrogen also in¯ uences the evolutionary economics of green tissues, but multiple sources (e.g., NO32 vs. NH41),
uneven costs of processing speci® c molecules, and variable plant capacity
to recycle tissue N mitigate its utility as currency for economic analysis
(Raven 1988).
Form and function also distinguish foliage inserted on a single axis.
Pineapple illustrates how the oldest and youngest leaves are shorter and
narrower than those located in between (Krauss 1948± 49). Position along
the phyllotactic spiral also determines when and for how long a leaf
remains functional, and how it contributes to the production of seeds and
the replacement ramet(s). Organs that develop early usually die before the
supporting shoot matures; younger leaves decline more synchronously.
Organ cost and payback should vary accordingly, but so far no one has conducted an economic analysis to test this possibility.
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Pitcairnia heterophylla, and the other members of the small group of
drought-deciduous Bromeliaceae, exhibit the most tightly coordinated leaf
life histories. Entire complements of green as opposed to the reduced, spiny
foliage appear in one brief ¯ ush (Fig. 2.12A). A pre-formed abscission
zone, consisting of a band of thin-walled cells located just above a sclerotic
hypodermis a few millimeters distil to each leaf sheath, mediates an equally
abrupt return to drought-invulnerability. Similar tissues explain why
senescing leaves separate about as cleanly among many evergreen Pitcairnia
species (Fig. 2.12B). Abscission zones also regulate leaf fall in Ayensua uaipanensis and Brocchinia melanacra, but so far none of the descriptions of
these ® re-tolerant Guayanan endemics mentions leaf life spans or phenology. Several weeks pass while the leaves of Fosterella penduliflora gradually
die back from tip to base as the more durable corm-like stem prepares for
drought.
Epidermis
Trichomes dominate the literature on the bromeliad leaf, while other
aspects of the epidermis and the tissues within receive far less to no coverage. Cuticles range from robust for the xerophytes of warm habitats (e.g.,
many Bromelia species) to unexpectedly delicate (e.g., Figs. 2.10, 2.13,
2.16). Type Five bromeliads fall across much of this range, even though
they share many other features consistent with xerophytism (e.g., CAM,
succulence). Tomlinson (1969) labeled the Tillandsia species equipped with
exceptionally thin cuticles to match equally delicate epidermal cells `hygromorphic' despite growth habits and habitats that assure only sporadic
opportunity to eliminate moisture de® cits. Additional qualities of the
cuticle and epidermis in¯ uence phenomena other than water balance.
Loose plates of wax that occlude the stomata of Tillandsia deppeana
native to northern Mexico may explain why it and certain other
Tillandsioideae sometimes grow in drier habitats than characteristic for
their ecophysiological type. Particles of the same composition re¯ ect light
and help Catopsis berteroniana and Brocchinia reducta trap and retain prey
in steep-sided phytotelmata (Fig. 5.3A,C). Additional species with no other
indications of carnivory (e.g., Tillandsia heterophylla) probably produce
similarly light-scattering cuticles on foliage to avoid photodamage.
Prominent ¯ oral bracts bearing the same products presumably help nectar
seekers locate nocturnal ¯ owers (e.g., T. heterophylla).
Epidermal cells beyond those that comprise the stomata and trichomes
vary in shape and alignment; some other, more consistent features probably
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Vegetative structure
impart important functional properties (e.g., Fig. 2.13). For example,
sinuous, interlocking radial walls strengthen the leaves of many bromeliads,
as do the inner tangential and radial walls of the xerophytes (e.g., Bromelia)
that thicken enough to con® ne the protoplast to less than 10% of the cell
volume (e.g., Fig. 2.13C). Uneven radial depths and wedge shapes foster
dovetailing that promotes rigidity and helps prevent the separation of the
epidermis from the underlying hypodermis (see Krauss 1948± 49; Fig.
2.16A).
A rugose, spherical mass of silica further con® nes the space allocated for
the protoplast in the epidermal cells of many bromeliads (Figs. 2.13C,
4.23I). Granule size (up to 5 mm) parallels the silica supply for cultivated
Ananas comosus (Krauss 1948± 49). Location in the center of a dish-shaped
lumina that also re¯ ects photons further underscores the importance of
redirecting excess radiance. Bromeliads with stout xeromorphic foliage
possess the largest crystals, and soft-leafed species better served by arrangements that enhance light absorption lack them (Tomlinson 1969). Dark
inclusions, perhaps tannins, located in the hypodermis below the adaxial
epidermis and sometimes in the sheaths of veins (Baumert 1907; Linsbauer
1911), along with the often-abundant anthocyanins, provide additional
protection for green cells located deeper in the foliage of many of the heliophiles.
Stomata
Tomlinson (1969) attempted to reconcile stomatal function with puzzling
morphology as several prominent morphologists had done before him. He
concurred that certain shapes and arrangements of the cells comprising the
stomata and subjacent mesophyll defy interpretation without speculation
about physiology. How, for example, can what are often exceptionally
thick-walled, achlorophyllous guard cells of certain species continue to regulate gas exchange (e.g., Fig. 2.13B)? Moreover, several diminutive
Tillandsia species feature anatomy that seems likely to prevent stomata
from closing! Mez (1904) and Billings (1904) deepened the controversy by
reporting that the stomata of certain Tillandsia species failed to move
during experiments.
Features that might allow Bromeliaceae with oddly shaped stomata to
nevertheless mediate gas exchange include certain con® gurations of associated hypodermal and subsidiary cells (Figs. 2.10K, 2.13C). Conceivably,
movements at these locations suffice in lieu of those usually involving guard
cells. Conversely, porosity may not be plant-controlled at all, or at least not
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in the manner expected for land ¯ ora consistent with some of the other
novel attributes of these highly specialized plants.
Tomlinson considered the paradoxically thin-walled epidermis and delicate cuticle of those `hygromorphic' Type Five taxa related to such a possibility, but offered an untenable view of water balance and plant nutrition
to make his case. Speci® cally, he suggested linkage between thin, porous
leaf boundaries and the need to eliminate the excess moisture that these
bromeliads supposedly must absorb to obtain enough required ions from
exceptionally dilute solutions, primarily precipitation.
In fact, whether taken up through roots or foliage, solutes never accumulate in plants by Tomlinson' s implied bulk ® ltration process, nor is another
unconventional mechanism or stomatal arrangement required to explain
the nutrition of the `atmospheric' bromeliads. High affinities for key ions,
combined with low plant demand, allow slow-growing, Type Five
Bromeliaceae to subsist on supplies that could not sustain more vigorous
¯ ora (Chapters 4 and 5). Pronounced capacity to scavenge solutes, including certain toxic agents, also underlies the successful deployment of these
bromeliads as air quality monitors, as detailed in Chapter 5.
Tomlinson (1969) recognized three kinds of stomata based on structure
and presumed operation. Related bromeliads possess similar and divergent
types indicating capacity for rapid evolution at least in some lineages.
Catopsis, Cottendorfia and a variety of similarly mesophytic types, mostly
in the same two subfamilies, feature thin-walled guard and subsidiary cells
aligned with the rest of the epidermis (Fig. 2.16A). An unobstructed substomatal chamber, which in the two more complex types accommodates
extensions of the adjacent epidermal or hypodermal cells, indicates that
these bromeliads probably ventilate leaf chlorenchyma in the usual manner.
Chloroplasts distinguish the hypodermal cells that line the air passages
leading to the mesophyll regardless of the type of stomata present (e.g.,
Figs. 2.13B, 2.16, 2.17A).
Members of all three subfamilies (e.g., at least some Guzmania,
Nidularium, Navia) possess the second type of stomatal apparatus, which is
marked by thicker-walled guard cells underarched by portions of lateral
and terminal subsidiary cells (Fig. 2.17A). Apertures can protrude above
the adjacent epidermis, while the rest of the apparatus lies recessed below
the leaf surface. An annulus of two to four, thin-walled, U-shaped, green
hypodermal cells is located beneath the guard cells (Fig. 2.17A). Lobes from
additional cells project into the substomatal chamber, meet, and sometimes
even grow up into the stoma. Typical function seems less likely here.
Modi® ed subsidiary and neighboring epidermal cells distinguish the
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third type of stomata (Fig. 2.13C). Unlike the second condition, the hypodermal cells in this instance lack conspicuous extensions; however, overlapping protuberances from in¯ ated subsidiary cells sometimes completely
occlude the superstomatal cavity. In other examples, adjacent epidermal
cells distort the stomatal complex enough to elevate its aperture above the
adjacent leaf surface. With few exceptions, certain Bromelioideae and
Pitcairnioideae (Ananas, Dyckia, Orthophytum, Puya) possess this most
complex of the bromeliad stomata, and these plants always grow under
semiarid to drier conditions.
Observations made by two pioneering morphologists exemplify the controversy over stomatal function. Lindsbauer (1911) suggested that those
protuberances located beneath some guard cells prevent closure even at
zero turgor, whereas Haberlandt (1914) considered the same arrangement
an impediment to gas exchange. Krauss (1948± 49) described how various
cells located in part or wholly under the guard cells swell as turgor mounts
and lift and push them apart to promote gas exchange. Tomlinson (1969)
adopted a more cautious stance when he wrote that at least those organs
with enlarged, lateral subsidiary cells `probably do not function like normal
stomata' .
More is known about the operation of bromeliad stomata today thanks
largely to the efforts of ecophysiologists primarily interested in CAM and
water economy among subjects as diverse as Aechmea nudicaulis, Bromelia
humilis and Tillandsia usneoides. Foliar conductances were found to routinely oscillate between night and day as expected for CAM plants and nonrhythmically in specimens challenged by abrupt exposures to drier air (Figs.
4.16, 4.19). Only one investigation addressed stomatal mechanics directly.
Martin and Peters (1984) applied abscissic acid, a regulator of guard cell
turgor in other, better-known ¯ ora, to demonstrate the expected responses
in T. usneoides. While these investigators con® rmed plant capacity to regulate diffusive conductance, no one has identi® ed which cells deserve the
credit.
Another rather exceptional claim made about bromeliad stomata concerns the smallest of the species. Once considered astomatous, the leaves of
tiny Tillandsia bryoides (Fig. 2.1) supposedly ventilate through scattered
patches lacking, or at most covered with a poorly developed, cuticle
(Lindsbauer 1911). Indeed, parallels exist in other land ¯ ora, most notably
among the so-called shootless orchids, which depend entirely on CAMequipped green roots without recognizable devices to regulate gas exchange
(Benzing and Ott 1981). Instead, these orchids maintain positive carbon
balance by coordinating phase three of CAM (the decarboxylation of
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stored malic acid) in light with capacity to ® x most of the resultant CO2
before it can diffuse to the atmosphere (Cockburn et al. 1985).
Evans and Brown (1989b) eventually discovered widely scattered, paracytic stomata (0.07 stomata mm21) located under the trichome shields, but
they made no assignment to any of Tomlinson' s three morphological types.
Recognition that autotrophic organs perforce need not physically regulate
gas exchange to achieve acceptable water and carbon economy might usefully inform future efforts to interpret bromeliad leaf structure and function when conclusions otherwise disagree with impressions of how leaves
should operate to conserve moisture.
Relationships between stomata and trichomes
Trichomes and stomata occur juxtaposed on the foliage of Bromeliaceae
other than Tillandsia bryoides. Pattern is most pronounced where both kinds
of organs lie in the intercostal grooves of the stouter-leafed types (e.g.,
Brocchinia paniculata, many Bromelia species and additional Bromelioideae
and Pitcairnioideae; e.g., Figs. 2.8F, 2.13A). Tillandsioideae less often
exhibit this kind of arrangement. More provocative is the numerical relationship between trichomes and stomata that distinguishes the three subfamilies
(Tomlinson 1969). Ratios between stomata and trichomes vary with leaf
function and suggest basic conditions that help explain how Bromeliaceae
could enter so many, often physically challenging, environments.
Stomata and scales co-occur among Bromeliaceae at ratios extending
from about 30:1 in Cottendorfia to 5:1 for sampled Pitcairnioideae except
Cottendorfia, to 0.5:l for Type Five Tillandsia and just 1.5:1 for the entire
subfamily. Bromelioideae fall between these two subfamily averages with 43
sampled species yielding a mean ratio of 3.2:1. Tomlinson' s (1969) implied
homology between the trichome and stomata, the possibility of a relatively
® xed number of versatile initials, and the striking ecological differentiation
of the subfamilies suggest special signi® cance for this range of numbers.
Readily altered ratios of these two organs and the multiple functions possible for the bromeliad trichome, combined with a generally plastic plant
architecture, perhaps set the stage for a radiation that, while not exceptional
for the numbers of species produced, would exceed most others for adaptive variety and novelty.
Leaves born by Type Five Bromeliaceae display dense covers of absorbing, light-re¯ ecting trichomes in lieu of conventional root systems.
Conversely, relatively few stomata need be present to CO2-saturate the
modest photosynthetic capacities of these dry-growing epiphytes and
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Vegetative structure
saxicoles (see discussion of optimization theory in Chapter 4). Where
liberal supplies of moisture obtained through extensive root systems or
capacious phytotelmata assure better-supplied, potentially more productive foliage (higher Amax), stomata must be more numerous, and the trichome functions primarily as an insulator (e.g., many Pitcairnia, Bromelia).
Scattered scales with broad, interlocking shields supported by stalks of
similarly inexpensive construction (thin walls and vacuolate if still alive)
will suffice as exempli® ed by Bromeliaceae with conventional root/shoot
apportionments (e.g., Figs. 2.5E,F, 2.8D).
In essence, a range of patterns characterized by speci® c ratios and types
of stomata vs. trichomes derived from some prototypical condition accommodate extant Bromeliaceae to contrasting kinds of environments. For
example, reduction in either the number of organs per unit leaf surface, or
simply the size of the trichome shield, occurred during radiation. Other features of shoots and roots also favored emergence of ecological variety and
stress-tolerance, for instance when a dense layer of absorbing trichomes
and impounding foliage began to complement one another to make several
modes of nutrition possible and release the plant from dependence on
water in soil (Chapters 4 and 5). Add the material economy granted by the
relaxed need for roots to the many additional bene® ts the indumentum and
an impounding shoot provide, and the array of substrates and climates
accessible to evolving Bromeliaceae became even greater.
According to this logic, capacity to allocate proportionally fewer epidermal initials to trichomes among the mesic forms (e.g., Type Four) permitted high stomatal density and sufficient diffusive conductance to support
the productivity permitted by relatively abundant supplies of moisture and
nutrients. Drier conditions and/or poorly developed root systems in turn
mandated proportionally more trichomes of the absorptive type at the
affordable cost of fewer stomata per unit leaf surface.
Finer adjustments in epidermal structure, also with major consequences
for ecophysiology, occurred along additional environmental gradients, at
least among Tillandsioideae. For example, stomata serving the soft-leafed
residents of humid montane sites (e.g., Guzmania sanguinea, Tillandsia
bulbosa) aggregate in the exposed regions of the epidermis beyond the
shields of adjacent trichomes in order to permit gas exchange during wet
weather (Fig. 4.23F; Table 4.8). Tillandsia with con¯ uent, relatively hydrophilic indumenta necessarily occupy more arid sites to avoid suffocation.
Here, far more often than not, the shields ¯ ex upward while dry, simultaneously exposing the stomata and scattering strong, potentially damaging
irradiance as described below (Fig. 2.7A,B).
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Mesophyll
Tissues below the epidermis reveal the presence of multiple mechanisms for
carbon and water balance; leaves also display additional anatomical detail
without recognized signi® cance. At one extreme, exempli® ed by Tillandsia
usneoides, an undifferentiated mesophyll surrounds just three to ® ve small
vascular bundles (Fig. 2.10A). Little additional strengthening tissue occurs
here or in the leaves of many other Type Five species (e.g., T. paucifolia, T.
ionantha, T. schiedeana), while some relatives (e.g., T. balbisiana, T. concolor) produce foliage that resists fracture even when folded. Sclerenchyma
tends to develop around the veins and immediately below the epidermis
depending on the species, and within a single plant, according to growing
conditions, especially exposure.
Most bromeliads possess a differentiated mesophyll. Multiple layers of
collapsible, accordion-pleated water-storage parenchyma lie beneath both
epidermal layers of the dry-growers, but depth is greatest on the adaxial
side (e.g., Figs. 2.13B, 2.16). Many populations native to everwet sites also
possess colorless hydrenchyma tissue, but considerably less than the volume
of adjacent green mesophyll (Fig. 2.13E). Occasionally, chlorenchyma lies
above and below a central nonphotosynthetic zone (e.g., Aechmea bracteata). Growth in full sun promotes scleri® cation and thicker hypodermal
layers and reduces the concentrations of chlorophyll (e.g., Guzmania monostachia; Chapter 4; Table 4.6; Fig. 4.26). Transitions between the often sclerotic outer and inner, more delicate hypodermal zones range from gradual
to abrupt.
Sharp boundaries typically separate the hypodermis and chlorenchyma
(e.g., Acanthostachys, Puya), but seldom is even a poorly differentiated palisade present (Fig. 2.16B,C). Extraordinarily capacious intercostal air
lacunae for CAM plants extend the length of the blades of most Bromelia
species and many other Type Two Bromeliaceae (Fig. 2.13B). Those of the
utriculate leaf traverse the entire organ, including the base where they
expand to become arenchyma-like as if required to ventilate tissue denied
more immediate access to O2 by the contents of ® lled phytotelmata.
Intercostal ducts are sometimes partitioned with diaphragms of abutting
stellate-lobed cells much like those characteristic of the spongy mesophyll
of many dicots (Fig. 2.13B).
The single row of bundles that vascularizes the length of the bromeliad
leaf varies in size across that appendage (Figs. 2.13E, 2.16C). Viewed in
cross-section, they lie about midway through the thin organ, but closer to
the abaxial surface in thicker blades because an adaxial hypodermis
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Vegetative structure
occupies more of the leaf interior. Extensions of the bundle sheaths usually
terminate below the epidermis. Rendered free, the tough vascular bundles
of Ananas comosus, Neoglaziovia, Aechmea magdalenae and several additional species of lesser importance support local ® ber industries (Chapter
14).
Strands of nonconductive sclerenchyma augment leaf strength for many
Bromelioideae (Fig. 2.13E). Those of Portea petropolitana contain septate
® bers, and, as elsewhere, occur in two series within the chlorenchyma, above
and below, but never interspersed among the veins. Transverse commissures embedded in narrow septa comprised of compact cells, sometimes
densely packed with chloroplasts as already mentioned for some of the variegated leaves, run above and below and cross the air lacunae (Fig. 2.17B).
Each junction consists of series of short, narrow water-vascular cells and a
thin phloem strand within a continuous sheath of parenchyma.
Optical properties
Horticulturists rely on several of the more conspicuous aspects of leaf
texture, shape and trichome cover already discussed to decide how to cultivate speci® c Bromeliaceae. More subtle structural and chemical indicators
provide more precise information about optimum growing conditions.
Diagnostic histology, for example the Kranz anatomy of a C4 plant, identi® es the photosynthetic pathway, and accordingly, patterns of carbon and
water balance. Speci® c leaf weights, and other indices of succulence and
sclerophylly, relate to modes of mineral nutrition, water use, and aspects of
leaf natural history, although often in ways that defy simple interpretation
(Chapter 5). Finally, even less accessible data on chemical composition and
physiology provide additional insights on plant life strategy.
Leaf anatomy also reveals which conditions of lighting best suit speci® c
Bromeliaceae. Optimum conditions range from high to low photosynthetic
photon ¯ ux density (PPFD) and the duration of that exposure from relatively continuous through the day for the lithophyte and savanna-dwelling
bromeliad to intermittent for those populations relegated to the forest
understory. Still other features of the leaf determine its responses to
spectral quality and beam alignment (collimation). Forest-dwelling
Bromeliaceae experience diffuse and direct-beam irradiance in different
proportions depending on the microsite. All four aspects of the energy
supply ultimately determine which combinations of leaf and shoot characteristics favor photosynthesis most in speci® c environments.
The presence of at least two photosynthetic pathways and leaf form and
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light response curves that also differ among closely related species document how rapidly the bromeliads have adapted to different growing conditions (Chapter 4). Distributions of these characteristics through the family
also demonstrate that CAM and succulence emerged repeatedly within
Pitcairnioideae and Tillandsioideae, just as drier conditions more than
once promoted dependence on trichomes in lieu of phytotelmata and
adsorptive roots (Table 4.1). However, the bromeliad literature says virtually nothing about the effects of light quality, collimation or sun ¯ ecks on
photosynthesis. Surprisingly, none of the considerable text devoted to discussions of the presumed conditions in ancestral habitats (e.g.,
Bromelioideae; Benzing and Renfrow 1971b; Medina 1974) includes comments about ambient light beyond its intensity in what were supposedly
either understory or more open sites.
Findings elsewhere can assist interpretations of the functional consequences of leaf form in Bromeliaceae as long as the effects of the light-scattering indumentum are taken into consideration. While the absorptive
trichome of a dry-growing Tillandsia promotes nutrition and water
balance, it also affects ecotolerance by altering the amount of irradiance
available to chloroplasts. Light scattering reduces the threat to vulnerable
pigment± protein complexes in some cases, while leaf structure of another
sort focuses incident diffuse light and enhances photosynthesis for other
species native to lower-energy habitats.
Many factors, including cell structure, the relative amounts of certain
pigments present, and leaf attitude relative to the source determine how
light travels through an epidermis and into the underlying chlorenchyma.
Penetration may be enhanced or inhibited by several organ-speci® c characteristics. Raised trichome shields scatter photons from the foliage of drygrowing Tillandsioideae and many other bromeliads (e.g., Fig. 2.8C,E).
Conversely, thin-® lm phenomena may help compensate certain understory
plants for the differential diminution of shorter-wave radiation in shadelight (Lee et al. 1979). Foliage in such cases appears bluish green under the
canopy compared with beyond it. Probably no bromeliad matches the performances of the spectacularly colored, exceptionally shade-tolerant pteridophytes, but several taxa (e.g., Nidularium burchellii; Fig. 2.4H) native to
dense rainforest suggest tendencies (fainter bluish tints) in that direction.
Timing, speci® cally the capacity of foliage to maximize energy harvest
from sun ¯ ecks, as elsewhere, probably depends more on leaf physiology
than optics or structure.
Anatomy affects leaf transparency beginning at the cuticle, which can be
highly re¯ ective to transparent, on down through the mesophyll to the
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Vegetative structure
opposing epidermis (Vogelmann and Martin 1993). Convex outer tangential walls of the adaxial epidermis of some understory ¯ ora concentrate
photons at focal points in underlying chlorenchyma with corresponding
diminutions elsewhere, especially if the source is diffuse rather than collimated. Within leaves, the shapes of the mesophyll cells and adjacent air
spaces further in¯ uence the paths followed by photons. Organs equipped
with a palisade transmit larger proportions of incident, high-angle light
than targets comprised of less aligned or more isodiametric cells.
Conversely, foliage featuring relatively undifferentiated interiors more
readily quenches collimated light, i.e., experiences more intrafoliar shading.
Light measured deep in the leaf indicates which kinds of anatomy favor
photosynthesis most under speci® c exposures, i.e., which arrangements
either screen vulnerable tissues from excess radiation or enhance the
capture of marginally adequate photon ¯ ux (Vogelmann and Martin 1993).
Presumably, ® ber optic probes could also be employed to determine the
suitability of a bromeliad to utilize shade (primarily diffuse) vs. un® ltered
(,85% collimated at noon) insolation. Populations (e.g., Ananas comosus;
Medina et al. 1991a, 1993) known for their capacity to accommodate speci® c ¯ uences could serve as subjects for tests. Experiments with cloned
materials maintained under different light regimens in turn would reveal
whether cell shapes and orientations exhibit more or less plasticity in widely
tolerant compared with ecologically more constrained genotypes.
Unexpected sources sometimes identify interesting subjects for investigations of the light relations of Bromeliaceae. Casual comments on herbarium labels or in the literature may indicate a phenomenon worth
consideration. For example, Hallwachs (1983) reported a bluish sheen to
the leaves of a forest-dwelling population of Bromelia pinguin in Costa
Rica. Usually this wide-ranging terrestrial experiences stronger light, often
as a `living fence' where stouter shoots develop shades of yellow-green.
Conceivably, its ability to acclimate so broadly rests partly on capacity to
alter leaf optics and chemistry to either enhance the capture of shade-light
or avoid injury in fuller sun. Conversely, more static arrangements may preclude similar ¯ exibility and, if also insensitive to natural selection, represent a signi® cant constraint on evolution. A constellation of Pitcairnia
species (sensu lato) may demonstrate such inertia, in this case related to the
organization of the mesophyll (G. S. Varadarajan, personal communication).
Few monocotyledons, including Bromeliaceae, possess a palisade comparable to the arrangement that prevails so widely in Magnoliopsida consistent with the linear, liliaceous leaf that so often orients parallel rather
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than perpendicular to direct-beam irradiance. Most Pitcairnioideae,
including all or much of Ayensua, Connellia, Cottendorfia, Lindmania,
Navia and Pitcairnia, follow this precedent by producing undifferentiated
chlorenchyma (Fig. 2.16C). However, a smaller group of thin-leafed,
forest-dwelling taxa exhibit an anticlinally elongated palisade above a basement layer of less densely packed and uniformly shaped components (Fig.
2.16B). Not surprisingly, leaves in this second case exhibit broad, ¯ at
laminae held more or less perpendicular to the most intense direct-beam
insolation. Additional characters unrelated to shade-tolerance, but indicative of phylogenetic relationship, suggest that these two conditions in¯ uenced evolution within Pitcairnia (sensu lato).
Species assigned to closely related Pepinia or Pitcairnia (sensu lato) that
share one of the two conditions of the mesophyll also differ relative to the
presence or absence of stolons, dimorphic or trimorphic foliage, deciduousness and certain aspects of trichome morphology (G. S. Varadarajan, personal communication). Speci® cally, Pepinia seems to circumscribe two
clades that parallel Pitcairnia in being more or less equipped to harvest
shade (scattered) light. Taxa with dimorphic chlorenchyma inhabit dark
understories (e.g., Pepinia corallina, Pepinia schultzei, Pitcairnia trianae;
Fig. 2.16B); the others more often grow as facultative epiphytes or riparian
terrestrials (e.g., Pepinia aphelandrifora, Pitcairnia pungens) where they typically receive strong direct-beam irradiance.
Similar patterns of leaf anatomy segregate the Puya species by altitude
and drought-tolerance as measured by the xericity of their habitats (G. S.
Varadarajan, personal communication). Again, shared morphology
involving other organs with no direct in¯ uence on light use (e.g., in¯ orescence branched or condensed) indicates the existence of two clades, each
disposed by leaf anatomy to colonize either strongly arid or more humid
habitats. However, Puya appear less differentiated by light environment
because the more mesic species inhabit open wetlands rather than the
understories of dense forests.
Downs (1974) reported additional species with `palisade-like' layers, and
some of the epiphytes among them regularly experience high PPFD as
upper-canopy specialists. Aechmea tillandsioides almost always roots in ant
carton, a medium that its architects assure will occupy sunny microsites
(Chapter 8). Aechmea nudicaulis also tends to encounter full exposure in
situ, especially in Brazilian restinga (Fig. 7.13C), across one of the broadest ranges achieved by a bromelioid. Other taxa with similar leaf anatomy
include Billbergia macrolepis, Brocchinia acuminata and Vriesea malzinei,
indicating convergence on the same arrangement for mesophyll in all three
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Vegetative structure
subfamilies. Examination of relatives with pronounced propensities for
darker or brighter habitats would help sort out which details of leaf
anatomy foster success in speci® c kinds of light environments.
Trichomes
Diverse agencies mediate the properties of plant boundary layers, particularly those covering foliage. The leaf epidermis stands out as a barrier that
must at once deter pathogens and predators, regulate gas exchange, help
maintain thermal budgets, and either screen excess light or enhance its
capture depending on PPFD and plant tolerances. Two additional tasks,
water and ion uptake, further complicate function for the bromeliads
lacking absorptive roots. Not surprisingly, these are the same species that
bear the most specialized foliar indumenta, and have received the greatest
attention from investigators.
Recognition that the foliar trichome of xerophytic Tillandsioideae performs operations usually associated with roots goes back more than a
century, but full appreciation of the consequence of this realignment
remains obscure. Recent revelations about the structure and operation of
the trichome of carnivorous Brocchinia reducta (Chapter 5) demonstrate
the value of more penetrating studies than most of those performed so far.
This ® nal section centers on the bromeliad trichome, speci® cally, how it
in¯ uences ecology through effects on a variety of basic leaf functions.
Chapters 4 and 5 more thoroughly consider foliage as root analog.
Almost all of the bromeliads possess some sort of foliar indumentum
that also often covers parts of the stem, in¯ orescence and ¯ ower. Glabrous
Navia species and others equipped with simple uniseriate hairs (e.g.,
Cottendorfia) belong exclusively to Pitcairnioideae (Robinson 1969; Fig.
2.5K,L,N). Relatively unspecialized ¯ owers, fruits and seeds, terrestrial
habits, and well-developed root systems indicate that of the three subfamilies recognized by Smith and Downs (1974), this one, minus Brocchinia,
most closely resembles the extinct, common ancestor, i.e., constitutes the
lowest of the evolutionary grades relative to ecology and vegetative structure, including the foliar trichome. However, molecular systematics indicates parallel rather than basal status for Pitcairnioideae (Chapter 9). If so,
the uniseriate trichome and glabrous epidermis represent apomorphies,
and the peltate hair or scale (e.g., Fig. 2.7), structure and function more
reminiscent of earlier times. Perhaps signi® cantly, unbranched hairs also
occur on the foliage of pineapple seedlings (Krauss 1948± 49).
Strehl and Winkler (1981) and Strehl (1983) assigned the types of tri-
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71
chomes present in each subfamily primitive to advanced status according
to the organization of the shield. The peltate scale occupies the basal position in Pitcairnioideae with the uniseriate form considered derived.
Aechmea bracteata illustrates the fundamental condition for
Bromelioideae, and those organs bearing the less common stellate shield
supposedly arose later. Guzmania monostachia receives the same designation in Tillandsioideae, while the relatively reduced trichome of the more
mesic forms (e.g., Catopsis nutans; Fig. 2.8B) and those with the most
expansive shields (e.g., Tillandsia crocata; Fig. 2.7D) are considered specialized for wetter and drier environments respectively. All three schemes seem
premature, but history need not be known to determine functions.
About the only trait shared by all bromeliad trichomes is multicellularity.
Even the simplest, unbranched appendages (Fig. 2.5K,L,N) consist of
adjoined cells, and members of the same genus and several others (e.g., some
Fosterella, Navia, Pepinia) possess stellate types (Fig. 2.5F,M). Virtually all
other Bromeliaceae bear scales comprised of a two to many-celled stalk
topped by a plate-like, single-layered, multicellular shield. Unlike those of the
stalk, components of the shield usually die at maturity, but not before their
walls develop important optical, hygroscopic and mechanical properties.
Aspects of indumenta important to insulation, such as the size and shape
of the shield and percent of the leaf surface covered, more closely parallel
growing conditions than taxonomic boundaries. Additional sets of characteristics vary to lesser degrees, but impacts on function may be more fundamental. Trichomes of Brocchinia, for example, usually conform to the
typical scale architecture (e.g., B. acuminata), the exceptions being those of
B. reducta and B. hechtioides that exhibit a goblet shape presumably related
to carnivory (Figs. 2.5A, 5.2E,F). On the other hand, every cell of the
mature trichome of several, if not all, members of this genus retains its
protoplast at maturity, a near novelty in the family (Fig. 5.2G).
On a ® ner scale yet, conspeci® cs (e.g., apparent ecotypes of Tillandsia
caput-medusae) growing under different exposures and humidities occasionally exhibit indumenta that match those conditions, especially PPFD
(Dimmitt 1985). Variables in this case involve both the structure of the individual appendage and density over the leaf surface. Brie¯ y, the widely
occurring scale, and particularly the organization of its shield, accounts for
most of the recorded structural variety among bromeliad trichomes. Table
2.1 summarizes the more salient of these anatomical peculiarities and identi® es where each type occurs in the family. Information is organized according to function, which ranges from secretion to the attraction of seed
dispersers and pollinators.
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Vegetative structure
Tillandsioideae
Billings (1904) described the ontogeny of the trichome of Spanish moss
and probably the pattern for the entire subfamily (Fig. 2.9). Development
begins with a single initial programmed to produce a uniseriate chain
topped by a cell destined to divide into four, equal-sized, wedge-shaped
daughters. Each of these four cells in turn divides unequally to yield the
central disc to the inside, while the smaller daughters proceed to form characteristic rings of cells and ultimately the wing. The result is a complex
device capable of changing shape to effect different functions according to
plant needs.
Consider the most specialized version of this organ beginning with the
central disc. Exceptionally robust, upper tangential walls alternately rise
and fall (xerophytic taxa, less so mesophytic types) on ¯ exible radial walls
as the adjacent cavities imbibe and lose water as weather dictates (Figs.
2.7A,B, 4.20, 4.21). While dry and collapsed, the upper tangential walls
block evaporation through the distal (dome) cell of the subjacent stalk.
Elevated, they expose the same cell to ¯ uids that ® ll the hydrated shield.
Below, two small foot cells anchor the entire appendage and mediate water
and ion ¯ ux from stalk to adjacent mesophyll.
Beyond the central disc lie one to four series of rings, each containing
twice the number of components as the one just inside (i.e., 8, 16, 32, 64)
except for the outermost series that may be incomplete (Fig. 2.7D± F,H).
Radial walls, except those of the cells of the central disc, become thickened
and rigid. Wings containing more than twice the number of cells present in
the outermost ring greatly expand the width of the shield of dry-growing
Tillandsioideae. Shields with the widest wings move more than the simple
rise and fall of the central disc as leaf surfaces alternately moisten and dry
(Fig. 2.7A,B).
A soft hinge provided by one or more series of ring cells equipped with
pliant upper tangential walls allows the expanded wing to ¯ ex upward upon
drying and scatter rather than propagate incident radiation. Warts, ridges
and additional irregularities sometimes further enhance re¯ ectivity (e.g.,
Tillandsia karwinskyana; Figs. 2.7F, 4.23H). Wing development varies with
the species, at one extreme endowing the mist-dependent types (e.g., T.
crocata, T. tectorum; Figs. 2.7D, 2.8C) with shields that extend far enough
above the epidermis to intercept aerosols. Leaves of the more shade-tolerant mesophytes support more widely scattered scales with shorter, nonoverlapping wings that cover less than 5% of the blade (e.g., Catopsis nutans;
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Fig. 2.8B). Many-celled stalks (highest in Glomeropitcairnia) supposedly
represent the basic condition in Tillandsioideae, but the evidence is thin.
Pitcairnioideae
The typically peltate trichomes of Pitcairnioideae feature one or fourcelled, small central discs that anchor expansive shields (Figs. 2.5, 2.8D).
Stalks tend to be narrow, few-celled, and equipped with less-developed
protoplasts than those featured by Tillandsioideae. Shield outline ranges
from more or less circular to oblong with entire to deeply incised margins.
Stellate form marks the exceptional species (e.g., Fosterella; Fig. 2.5F) as
do uniseriate trichomes or none at all (e.g., certain Navia). Concentricity
suggestive of Tillandsioideae distinguishes occasional Pitcairnioideae,
most notably members of Brocchinia, as described below (Fig. 2.5B,H,I).
Navia glandulosa stands out as one of the two bromeliads reported to bear
capitate, glandular hairs, in this instance predominantly on the ¯ oral bracts
(Fig. 2.5K). Ronnbergia petersi (Bromelioideae) produces similar appendages combined with more typical scales on its sepals (Gross 1991).
Trichome structure identi® es Pitcairnioideae allied by similar ecology,
but not as faithfully as in Tillandsioideae. Narrow, radially elongated cells
often produce a characteristic shield margin among the dry-growers (e.g.,
Hechtia) and fewer of the more mesic taxa (e.g., some Fosterella, Pepinia).
Alpine Puya feature dense layers of sometimes brownish woolly scales (Fig.
7.2). Shields never develop the structure that mediates the valve-like (hydrorectifying) action characteristic of dry-growing (Type Five) Tillandsioideae.
Arid-land Pitcairnioideae usually bear trichomes with relatively opaque
shields compared with relatives from moister, darker habitats.
The pitcairnioid indumentum tends to occur unevenly across the leaf
surface, often more densely on the abaxial than on the adaxial side (e.g.,
Pitcairnia). Scales of many of the dry-growing types anchor between the
costa, especially on the abaxial epidermis, where they insulate the stomata
(e.g., Dyckia). Relatives from humid sites and those few species that shed
foliage preparatory to drought produce scattered trichomes over one or
both surfaces. Quite a few of the mesophytes (e.g., Lindmania, Navia) lack
adaxial trichomes. Banded indumenta responsible for the ornamented
foliage of certain Bromelioideae (e.g., Aechmea chantinii, Billbergia zebrina
and especially certain Cryptanthus; Figs. 2.14F, 2.18C) and Tillandsioideae
(e.g., Tillandsia flexuosa, T. hildae; Fig. 2.7I) have no parallel in
Pitcairnioideae.
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Vegetative structure
Special mention is due Brocchinia, which, although assigned by Smith
and Downs (1974) to Pitcairnioideae, exhibit trichomes that by structure
and function (Figs. 2.5B,H,I, 5.2F,G) more closely parallel counterparts in
Tillandsioideae. Circular to oval shields contain different numbers of cells,
but concentric alignment is common. Relatively elongate components form
a rudimentary (e.g., B. reducta) to a better-de® ned (e.g., B. acuminata, B.
micrantha) wing peripheral to a less organized group of central cells.
Stalks may be uniseriate (e.g., B. acuminata; Fig. 5.2G) or expanded to
several cells near the top (e.g., B. reducta; Fig. 2.5A). Well-developed phytotelm architecture and demonstrated absorptive capacity among some
members of this enigmatic genus suggest circumstances that also fostered
the assumption of many root functions by leaves in Tillandsioideae. A
hypothesis offered in Chapter 9 describes how absorptive capacity may have
evolved in the trichome of Brocchinia and perhaps elsewhere among primitive Bromeliaceae.
Bromelioideae
Bromelioideae produce scales organized more like those of Pitcairnioideae
than of Tillandsioideae (Fig. 2.6). Speci® cally, a small disc of four cells may
occupy the center of the shield (e.g., Billbergia, Cryptanthus, Orthophytum)
and those beyond sometimes form rudimentary rings (e.g., Aechmea rosea,
Neoregelia pauciflora). One or two of the outermost series of shield cells
sometimes constitute a discernible wing (e.g., Canistrum fosterianum; Fig.
2.6F), but alignments never meet the standard set by Tillandsioideae.
Modestly lobed to deeply divided margins also parallel those of certain
Pitcairnioideae, while pronounced stellate morphology (e.g., some
Streptocalyx species) approaches arrangements in this taxon even more.
Shields with more or less circular form and entire margins occur widely
through many of the largest genera (e.g., some Billbergia, Bromelia,
Cryptanthus); those with strongly asymmetric outlines (e.g.,
Acanthostachys, other Bromelia) comprise a small minority.
Two-celled stalks characterize Neoglaziovia, Orthophytum and
Pseudananas, three distinguish Greigia, and up to 10 components anchor
the shields in additional taxa (e.g., Canistrum, Nidularium; Fig. 2.6). Stalks
in all instances lack clear differentiation into a dome and smaller transfer
cells as in Pitcairnioideae. Beyond Ananas comosus (Sakai and Sanford
1979), no reports mention ® ne structure that might promote absorption.
Scales on the leaf bases of at least some phytotelm Bromelioideae take up
nutrients from adjacent phytotelmata (Benzing et al. 1976), but not as
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avidly as those of the xerophytic Tillandsioideae tested under the same conditions (Chapter 5).
Trichomes of Bromelioideae often occur unevenly across the leaf. Deep
intercostal grooves accommodate the scales and stomata of many of the
thicker-leafed xerophytes (e.g., Bromelia; Figs. 2.8F, 2.13A) where they
probably help conserve moisture. Some Cryptanthus and Aechmea species
bear highly ornamental bands of re¯ ective scales (Figs. 2.14F, 2.18C).
More often con¯ uent indumenta cover the abaxial surface, whereas the
usually astomatous adaxial epidermis features fewer to no scales (e.g., some
Cryptanthus and Nidularium).
Denser concentrations of trichomes typically invest the leaf bases of the
phytotelm forms, including members of Type Two (e.g., Ananas, Bromelia;
Fig. 2.14A,B). Shields are generally also wider on the leaf base compared
with the blade (e.g., Aechmea bracteata). Trichomes of Bromelioideae have
attracted less attention than those of the other two subfamilies, although
more than half of the 50-plus bromeliad genera are assigned here. The 800
or so member species occupy a somewhat less extensive array of habitats
than colonized by the other two subfamilies (e.g., virtually none in upper
montane cloud forests).
Trichome functions beyond absorption
Bromeliad trichomes perform many of the same functions documented
among other Magnoliophyta (Table 2.1). Demonstrated and putative services vary with the species. Spiculate hairs born by certain Pitcairnioidae
may impale soft-bodied predators much as similarly shaped organs do elsewhere. Interlocking shields of the peltate types (Fig. 2.8D), in addition to
impacts on leaf energy budgets and gas exchange, may shield underlying
stomata from invading hyphae, or deter small predators seeking more nutritious mesophyll.
Trichomes comprised entirely of living cells (Brocchinia) might contribute digestive secretions to adjacent tank ¯ uids. No bromeliad reportedly
elaborates repellents or toxins for protection, although those capitate hairs
just described for Navia glandulifera (Holst 1996) could do just that (Fig.
2.5K). Silvery trichomes on the short, compact (nidulate) in¯ orescence of
forest-dwelling Neoregelia longisepala produce a strong visual signal for
fauna seeking nectar or edible fruit deep in the heavily shaded center of its
large rosette. Highly re¯ ective trichomes on the otherwise drab fruits of
certain Billbergia seem well disposed to guide fruit-feeding bats (Fig. 3.5G).
Multiple, sometimes inherently antagonistic, functions suggest that the
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Vegetative structure
leaf epidermis constrains ecological options most in Tillandsioideae. Even
so, species with similarly dense layers of absorbing trichomes experience
diverse microclimates and anchor on widely differing kinds of substrates.
Recall that Type Five species, more than 250 in all, share many aspects of
foliage in addition to dense indumenta that affect ecophysiology (e.g.,
CAM, succulence), yet these plants tolerate cool to high temperatures,
moisture supplies as distinct as rain, fog and dew, full sun to partial shade
and so on. So how can ¯ ora equipped with foliage characterized by the
same combination of specializations maintain tolerable thermal, moisture,
carbon and nutrient budgets under such disparate growing conditions?
Mez (1904) recognized that most dry-growing Tillandsia (Type Five) fail
in wet, shaded locations because the foliar epidermis of these plants prohibits survival under conditions suitable for many other ¯ ora. Capacity to
endure drought, often while rooted on unyielding substrates as these plants
typically do, requires a profound evolutionary trade-off. Hydrophilic scales
that so effectively enhance the impact of brief showers on plant hydrature
suffocate foliage moistened more frequently because they hold ® lms of
moisture over the stomata (Figs. 2.8C,E, 4.11; Table 4.8). A subtly different
indumentum mediates another kind of performance for some close relatives of these same obligate xerophytes (Benzing et al. 1978).
A few Type Five Tillandsia species (e.g., T. bulbosa; Figs. 4.23F,G, 8.5A)
exhibit unexpected tolerance for shade and humidity. Wetted at night, these
plants consume CO2 as if still dry (Table 4.8; Fig. 4.11). Exceptional trichome structure and rigidity and distribution relative to the stomata
explain this difference. Although organized like those of other
Tillandsioideae, the abaxial trichomes born by these species fail to move
like their counterparts serving Spanish moss and its kind, and the shield
wings lie beyond the stomata (Fig. 4.23F). Permanently ¯ attened against
the leaf surface, the scale probably promotes rather than reduces light propagation through the epidermis and, additionally, sheds water. Trichomes on
the largely inrolled and astomatous, adaxial surface exhibit the more
typical Type Five form and scatter irradiance, although not necessarily to
the advantage of T. bulbosa in its shady habitats (Fig. 4.23G).
Perspectives on how different features of the indumentum affect heat
loads, promote the uptake and retention of moisture, and help expose or
shield chlorenchyma from light require biophysical analysis. For example,
shields of some of the most drought and heat-tolerant tillandsias, like those
of T. bulbosa, move little if at all, but often exhibit elaborate ornamentations (e.g., Tillandsia karwinskyana; Figs. 2.7F, 4.23H). Does the rigid
shield displayed by this dry-growing species enhance stress-tolerance by
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77
insulating the stomata? If so, do those accompanying warty walls obviate
the need for the light-scattering effect of the ¯ exible trichome? Moving on,
does the attenuated wing of the mist-dependent bromeliad (T. tectorum;
Fig. 2.8C) promote condensation, and if so, how close does its structure
approach the theoretical ideal under ambient conditions?
What features re¯ ect the trade-off that has evolved between the needs of
these plants to re¯ ect light and obtain and conserve moisture? How much
self-shade is cast by various types of indumenta? Might certain of the more
transparent trichomes focus scattered photons and enhance photosynthesis in shade-light? Does light-piping ever promote shade-tolerance, for
instance for densely trichomed T. pruinosa, which in Florida occupies
understories free of the other local Type Five Bromeliaceae? Scale variety
among extant Tillandsioideae depicts radiation in miniature ± change in a
single organ that assisted colonization of diverse and often demanding habitats by well over 1000 species of bromeliads.
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3
Reproductive structure
A substantial literature dating back more than a century describes the bromeliad reproductive apparatus. Taxonomists working with dried specimens
authored most of the early treatments. Interest continues, but specimen
quality has improved allowing analyses to be more comprehensive. For
example, Brown and Terry (1992) used liquid-preserved ¯ owers and scanning electron microscopy to determine that the delicate petal scale that
® gures so prominently in the most recent monograph of the family (Smith
and Downs 1974, 1977, 1979; Fig. 3.1) circumscribes some genera more
convincingly than others. Wet material has also permitted determinations
of when certain features appear during ontogeny, and accordingly, their
utility for distinguishing taxa of low vs. higher rank.
Plant form underlying reproductive phenomena like pollination and seed
dispersal and the genetic structure of populations are our primary concern
for this review. Unfortunately, few of the hundreds of publications devoted
to the reproductive apparatus of Bromeliaceae provide much insight on any
of these subjects. Moreover, inquiry on ¯ owers, fruits and seeds continues
to be motivated primarily by interests in systematics. The exceptional
report that does depart from tradition usually addresses the same question,
namely who pollinates which bromeliad?
Today, molecular biology is augmenting the morphological data traditionally used to infer bromeliad history. However, cladograms based on
nucleotide sequences must be more fully resolved than those illustrated in
Chapter 9 to produce the phylogeny necessary to determine where, when
and how often decisive features of the reproductive apparatus evolved.
Additional information on gross morphology is also needed to address
questions such as whether the different conditions of the ¯ ight apparatus
of the seeds of Tillandsioideae re¯ ect separate origins (Palací 1997).
Speci® cally, do Tillandsia/Vriesea vs. Catopsis or Glomeropitcairnia share
homologous or convergent coma morphology?
79
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Reproductive structure
Figure 3.1. Aspects of ¯ ower structure among Bromeliaceae. (A) Dyckia ragonesei
gynoecium illustrating septal nectaries, placentation and partial fusion of the
carpels. (B) Six versions of petal scale morphology in six species representing all
three subfamilies. (C) Five recognized stigma types. Part A redrawn from
Bernardello et al. (1991); B redrawn from Brown and Terry (1992); C redrawn from
Brown and Gilmartin (1989b).
This chapter begins with brief surveys of the organization of the bromeliad ¯ ower, fruit, seed and in¯ orescence, emphasizing features that circumscribe genera and subfamilies. Next, we turn to aspects of the reproductive
apparatus responsible for distinguishing Bromeliaceae biologically (e.g.,
heavily epiphytic, extraordinary reliance on birds for pollen dispersal)
among angiosperms and shaping plant impacts in communities.
Relationships between plant structure and function receive priority
throughout. Much additional information on bromeliad reproduction,
including more detailed gross structure, appears in Chapters 6 and 9.
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Inflorescences
Most bromeliads ¯ ower terminally, either just once if the genet is monocarpic, or repeatedly in turn from each of a potentially in® nite number of
ramets produced by sympodial branching (Fig. 2.3A,B). Many fewer taxa
produce lateral in¯ orescences, i.e., are monopodial (Figs. 2.2B, 2.3C).
Structure usually differentiates the vegetative from the reproductive
portion of the shoot in the sense that the ¯ owers and ¯ oriferous branches
of the more complex in¯ orescences arise from the axils of bracts rather
than from undiminished foliage (but see Cryptanthus; Fig. 3.2H). Racemes
and spikes characterize an inordinate number of species; heads typify
several more genera (e.g., Neoregelia, Nidularium). Panicles comprised of
racemes and spikes occur among the larger-bodied members of all three
subfamilies (Figs. 3.2± 3.4). Architecture and peculiarities of development
differ, sometimes even among closely related populations, indicating considerable evolutionary plasticity and reason for caution when choosing taxonomic markers.
Tillandsioideae illustrate both the simplest and some of the most
complex in¯ orescences in the family (Fig. 3.3; Chapter 12). Reduction to a
single ¯ ower occurs exclusively in Tillandsia (e.g., Tillandsia usneoides)
where miniaturization associated with neoteny precludes more substantial
reproductive efforts (Chapter 6; Fig. 2.1). Flowers and branches born on
the more elaborate systems associate in either distichous (e.g., Vriesea bituminosa, V. hydrophora, many Tillandsia species; Figs. 3.3A, 3.5A,C) or
polystichous arrangements (e.g., Catopsis, Guzmania, Tillandsia imperialis;
Fig. 3.3G,H). Pedicles sometimes twist in one direction to produce a secund
spike (e.g., Vriesea oligantha; Fig. 3.3E), or they align the ¯ owers in similar
fashion along the subdivisions in branched systems (e.g., Tillandsia
secunda). Internodes range from elongate (often true of the main axis) to
telescoped (more often the ¯ ower-bearing axes), yielding arrays of relatively lax to more congested ¯ owers respectively. Tight heads surrounded
by petal-like bracts (Fig. 3.3K) suggest the more familiar pseudanthium of
Asteraceae.
Core Bromelioideae (e.g., Aechmea, Billbergia, Neoregelia; Fig. 3.2)
exhibit similar variety, including many to few-¯ owered forms (e.g.,
Aechmea pectinata, Neoregelia ampullacea respectively), condensed to
spreading types (e.g., various Aechmea, Portea), and species with distichous
(e.g., Aechmea tillandsioides) or polystichous (A. bromeliifolia) arrangements of ¯ owers. A few taxa produce pseudanthia (e.g., Canistrum). Much
the same variety can be cited for Pitcairnioideae (Fig. 3.4). Architectural
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Reproductive structure
Figure 3.2. Representative ¯ owers and in¯ orescences of Bromelioideae. (A)
Nidulate Neoregelia. (B) Aechmea fulgens. (C) Aechmea bracteata. (D) Aechmea
setigera illustrating armed ¯ oral bracts. (E) Greigia sp., whole plant and axillary
in¯ orescence. (F) Billbergia amoena showing conspicuous ephemeral scape bracts.
(G) Aechmea fasciata. (H) Cryptanthus correia-araujoi, ¯ owers subtended by foliose
bracts.
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Figure 3.3. Representative ¯ owers and in¯ orescences of Tillandsioideae. (A)
Tillandsia cyanea, prominent ¯ oral bracts. (B) Tillandsia argentea, ¯ oral bracts
much reduced. (C) Tillandsia loliacea, miniaturized ¯ owers consistent with neoteny
(arrow). (D) Guzmania wittmackii, foliose scape bracts. (E) Vriesea oligantha,
secund spike. (F) Tillandsia xiphioides, ® mbriate corolla. (G) Guzmania globosa,
head enveloped in mucilage. (H) Catopsis sessiliflora, staminate (below) and pistillate (above) plants, fruit, seed and structure of pistillate ¯ ower. Note vestigial
stamens. (I) Tillandsia streptocarpa, mass ¯ owering species. (J) Alcantarea nevaresii. (K) Guzmania lingulata, in¯ orescence forms pseudanthium. (L) Tillandsia albertiana. (M) Tillandsia viridiflora, chiropterophilous.
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Reproductive structure
Figure 3.4. Representative ¯ owers and in¯ orescences of Pitcairnioideae. (A) Navia
caulescens. (B) Navia linearis with isolated pistil. (C) Navia polyglomerata with isolated pistil. (D) Entomophilous Fosterella penduliflora (below) and ornithophious
Fosterella spectabilis (above). (E) Pitcairnia with radial ¯ ower and ¯ aring corolla.
(F) Pepinia pruinosa. (G) Chiropterophilous Encholirium glasiovii. (H)
Chiropterophilous Pitcairnia brongniartiana. (I) Sepal nectary of Dyckia floribunda
in section. (J) Perennial in¯ orescence of Deuterocohnia meziana; arrows indicate
sites of proliferations for additional ¯ owering after the ® rst season. (K) Pitcairnia
flammea with zygomorphic ¯ ower in cyme. (L) Pitcairnia bakeri showing dense
spike. (M) Pitcairnia arcuata; stippling on older ¯ oral bracts indicates extent of progressive deliquescence.
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redundancy across all three subfamilies reveals the distinctly homoplasious
nature of the organization of the bromeliad in¯ orescence.
Other groups of monocots, for example Poaceae, parallel Bromeliaceae
for diverse in¯ orescence structure, except that the small, wind-pollinated
grass ¯ ower allows more compact arrangements, and the bracts tend to
protect and help disperse seeds rather than attract pollinators and frugivores. Imperfect ¯ owers also occur in both families, but the bromeliads
more often exhibit related dimorphism. Pistillate plants of dioecious
Catopsis and Hechtia feature more abbreviated in¯ orescences with fewer
¯ owers than their male counterparts (Fig. 3.3H). Pistillate Hechtia carlsoniae produces a spike, while its staminate counterpart is di- to tripinnately
branched, presumably to enhance male relative to female function (assure
high ratios of pollen to ovules).
Anthesis usually proceeds acropetally through spikes and cymes (e.g.,
Encholirium; Figs. 3.4G, 6.2A), and from the outside inward for heads (e.g.,
Neoregelia; Fig. 3.2A). Exceptions include certain Canistrum species where
the buds in the middle of what approaches a capitulum open ® rst. Members
of Aechmea section Ortgiesia ¯ ower basipetally, (from the top down), and
occasionally from the middle in both directions. Deuterocohnia meziana
lacks rivals for its shrubby in¯ orescence that ¯ owers repeatedly for 6± 8
years (Fig. 3.4J). Thick axes warrant closer inspection to con® rm the
reputed presence of a vascular cambium. Occasional proliferation of additional ¯ oral primordia around the periphery of spent infructescences
allows some of the ramets of several members of Neoregelia subgenus
Hylaeacium (e.g., N. eleutheropetala, N. myrmecophila) to reproduce during
a second season.
Lateral in¯ orescences characterize Greigia and certain members of
Dyckia, Encholirium and Hechtia among others (Figs. 2.2B, 3.2E, 6.2B).
Tillandsia complanata produces small, multiple spikes on lax scapes from
axillary buds on indeterminate shoots; outwardly similar T. multicaulis and
T. monstrum in fact remain cryptically sympodial as described in the previous chapter. Lateral ¯ owering occurs sporadically in the exceptional, sympodially branched population, for example the occasional in¯ orescence of
Quesnelia lateralis that arises as a neotenic ramet devoid of expanded
foliage. Discovery that conspeci® cs ¯ ower from one or the other location
obliged the synonymy of Q. centralis with Q. lateralis.
Bracts, which sometimes occur in several orders and sizes on the same
in¯ orescence, assist reproduction by targeting speci® c pollen and/or seed
dispersers. They also protect the developing ¯ owers and later sometimes the
ripening fruit (Figs. 3.2± 3.4). Sterile nodes below those bearing ¯ owers
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Reproductive structure
usually subtend the largest, most colorful appendages among
Bromelioideae (e.g., Billbergia; Fig. 3.2F); similar organs tend to distribute
more evenly through the in¯ oresences of Pitcairnioideae and especially
Tillandsioideae (Fig. 3.4L,M). A sterile 15± 25 cm extension of the otherwise nidulate in¯ orescence of Guzmania sanguinea var. comosa bears bright
orange bracts whose purpose can only be attraction for birds.
Bracts may be elaborate and persistent (e.g., Aechmea fasciata; Fig.
3.2G), or much reduced and more ephemeral (e.g., Aechmea fulgens; Fig.
3.2B). Ancillary functions characterize the exceptional species, for example
the red bracts that also secrete nectar to attract ant guards to Tillandsia balbisiana (see below). Floral bracts produced by Aechmea setigera bear a
sharp terminal spine that seems not to impede either pollination or seed dispersal, but may deter large grazers (Fig. 3.2D).
In¯ orescence bracts help identify tillandsioids dependent on certain
kinds of pollinators (Chapter 6). Those of fundamentally ornithophilous
Tillandsia subgenus Tillandsia both enclose the developing ¯ ower(s) and
fruit(s) and provide the major visual signal for nectar-seekers (e.g.,
Tillandsia punctulata; Fig. 6.1B). The same appendages serve entomophilous and autogamous members of subgenus Anoplophytum and
Diaphoranthema as the smaller, often less colorful organs needed primarily
to insulate meristems and young ¯ oral buds (Fig. 3.3C,I). Aechmea fulgens
(Fig. 3.2B) and various Pitcairnia (e.g., P. bakeri vs. P. flammea; Fig. 3.4K)
exemplify the same arrangements in Bromelioideae and Pitcairnioideae
respectively.
Visual attractants other than anthocyanins brighten the in¯ orescence of
some of the other bromeliads. Boat-shaped, foliaceous bracts covered with
copious, re¯ ective wax, combined with fragrant nocturnal ¯ owers, probably lure moths to Tillandsia heterophylla. The same appendage born by
numerous other Tillandsioideae (e.g., Vriesea cylindrica; Fig. 3.5D) dries
out to a light brown before the associated ¯ owers open. Persistent drops of
water indicate that V. hydrophora features functional hydrathodes on its
¯ oral bracts (Fig. 3.5A). Appendages subtending the ¯ owers of some
Cryptanthus species resemble foliage, as do those of Tillandsia brachycaulos and T. capitata, although the latter color up long enough to help attract
pollinators (Fig. 3.2H).
Breeding system and other aspects of ¯ owers and the durability of bracts
sometimes suggest greater importance for seed dispersal than for pollination. For example, the scape bracts of paniculate and autogamous Aechmea
bracteata color up to a bright pink before anthesis and remain undiminished thereafter, apparently to act as fruit ¯ ags. Conversely, the colorful
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Figure 3.5. Flowers and fruits of Bromeliaceae. (A) Guttating ¯ oral bracts of
Vriesea hydrophora. (B) Nidulate in¯ orescence of Neoregelia sp. with pollinator. (C)
Sticky ¯ oral bracts of Vriesea bituminosa with captured insects. (D) Thief seeking
nectar from base of corolla of Vriesea cylindrica. (E) Melaponid wasp visiting
¯ ower of chiropterophilous Vriesea atra at midmorning. (F) Pendant spike of
Tillandsia dodsonii. (G) Ripe fruits of Billbergia porteana photographed against the
foliage of a shrub at dusk with ¯ ash to illustrate re¯ ective trichomes. (H) Armed
fruits of Aechmea angustifolia.
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Reproductive structure
primary bracts of usually ornithophilous Billbergia fade within days to pale
pastels, sometimes even before the youngest ¯ owers open (Fig. 3.2F).
Signi® cantly, the sometimes strong-smelling brown to yellow or trichomecovered fruits on pendant spikes attract bats (e.g., B. porteana; Fig. 3.5G).
Even more curiously ephemeral, the pink and imbricated bracts of Pepinia
fimbriatobracteata soon degrade to a glutinous blackish-brown residue
reminiscent of a deliquescent sporocarp of the fungus Coprinus. Several
related species (e.g., Pitcairnia arcuata; Fig. 3.4M) engage in less pronounced autolysis.
Extra¯ oral nectaries help deter herbivores and perhaps distract nectar
thieves for members of at least three genera in two subfamilies. Koptur
(1992) photographed ants collecting nectar on the immature bracts of
Tillandsia balbisiana, a likely bird-pollinated epiphyte in southern Florida.
Galetto and Bernardello (1992) described secretions from glands located
on the calyx of nine species of Dyckia and a Deuterocohnia native to northeastern Argentina (Figs. 3.4I, 8.2E). Regular ant-nest users (certain
members of Aechmea, Neoregelia) also merit inclusion in this group if
they, like so many of the nonbromeliads that share the same media, also
produce ant food. Glands reported so far differ from those located in the
ovary, conforming instead to the easily overlooked `formless type' (Fig.
3.4I).
Orientation, timing, and rates of maturation further distinguish bromeliad in¯ orescences, and help promote relationships with speci® c kinds of
pollinators and seed dispersers. Those of the epiphytes often hang below
the shoot, while the same organs of the terrestrials almost always stand
upright (Figs. 3.5F,G, 6.2A,B). Oddly deviant Pitcairinia corallina produces a bright red spike that, unexpectedly for its color and presumed pollinators, sprawls along the ground seemingly out of range of most
nectar-feeding birds.
Many months pass before some of the largest and usually monocarpic
Tillandsioideae (e.g., Tillandsia grandis, Alcantarea regina) and
Pitcairnioideae (e.g., Puya raimondii) with erect, multibranched in¯ orescences exhaust complements of hundreds to tens of thousands of ¯ owers.
Certain one to few-¯ owered relatives (neotenic Tillandsia) must set fruit
within a few days, but typically dense populations of somewhat asynchronous individuals or attached ramets assure more extended opportunities to
set fruit (Chapter 6).
Weeks to several months pass between the ® rst visible signs of bolting
and the ® rst ¯ ower opening, and growth often accelerates as anthesis
approaches. Downs (1974) reported that Billbergia elegans required nearly
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a month to emerge from the funnelform shoot, but just four more days to
expand to ® nal size and present the ® rst ¯ ower. Scapes elongated at rates of
up to 10 cm day21. At the other extreme, the short, capitate in¯ orescence of
Neoregelia exhibits more conservative and precisely regulated growth,
extending just enough to allow the tubular ¯ owers to emerge above the phytotelmata and assure the resulting inferior-ovaried fruits opportunity to
develop submerged, perhaps to avoid predators (Figs. 3.2A, 3.5B). Fruits
of some species elongate enough at the base to protrude several centimeters above the waterline at ripeness (Fig. 3.6F).
In¯ orescences produced by species with phytotelm shoots pose interesting questions about morphogenesis. Speci® cally, does ethylene play a regulatory role similar to that responsible for the measured elongation of the
shoots and leaves of certain emergent aquatics (e.g., Nymphaeaceae)?
Would the in¯ orescences of the nidulate bromelioids still end up just long
enough to position the ¯ owers just above the waterline if they developed
while tanks were empty?
Agents other than water may also impede gas exchange with different
consequences. Copious mucilage, presumably secreted from the ¯ oral
bracts or buds, insulates the fruits of Guzmania globosa (Fig. 3.3G) until
capsules dehisce after which the plumose seeds require drier conditions to
take ¯ ight. Lesser secretions characterize many additional Tillandsioideae,
and these products sometimes cause the leaves and ¯ oral bracts to `quill'
i.e., stick together (e.g., Vriesea glutinosa).
Quite likely, growth factors synthesized in the developing in¯ orescence,
or the absence of substances formerly produced by the vegetative apex,
activate one or more of the axillary buds programmed to produce ramets.
Anthocyanins that temporarily suffuse the shoots of many bird-pollinated
types probably owe their synthesis to light and chemical signals originating
in the embryonic in¯ orescence. Those scattered taxa (e.g., several
Orthophytum, Tillandsia flexuosa, T. paucifolia; Fig. 2.11A) that produce
offshoots from buds subtended by ¯ oral bracts raise additional questions
about the involvement of hormones in bromeliad reproduction.
Flowers
Bromeliad ¯ owers range from relatively small to large and inconspicuous
to showy. All of the species feature the differentiated perianth characteristic of related taxa like Commelinaceae and Zingiberaceae rather than the
tepals of most Liliales. Zoophily prevails except for the occasional autogamous types that require no pollinators (e.g., neotenic Tillandsia; Fig. 2.1).
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Reproductive structure
Figure 3.6. Fruits and seeds of Bromeliaceae. (A) Fruit of Ananas bracteatus. (B)
Germinating seeds removed from berry of Aechmea dactylina. (C) Armed fruits of
Ronnbergia deleonii. (D) Fruit and appendaged seeds of Araeococcus micranthus.
(E) Cryptanthus bromelioides showing thin-walled fruit and one seed. (F) Elongated
ripe fruits of Neoregelia stolonifera extending above the phytotelmata. (G)
Billbergia brasiliensis, fruit and seeds. (H) Seeds of Aechmea magdalenae and
Aechmea bracteata (right to left). (I) Structure of testa of Billbergia elegans (above)
and Glomeropitcairnia penduliflora (below). (J) Seed of Tillandsia germiniflora illustrating coma. (K) Seed of Tillandsia castellanii with multiple embryos. (L) Seeds of
Aechmea angustifolia, A. bromeliifolia and A. kuntzeana from left to right.
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Tiny ¯ owers with exerted styles and anthers born by certain small-bodied
navias might be wind pollinated (Fig. 3.4A).
Several peculiarities mark the bromeliad ¯ ower, most notably the
unpaired sepal that lies above the ¯ oral bract, and the twisting of all three
calyx members to the left to cover the margins on the right and produce an
involute whorl (Chapter 12). Derived conditions include the imbricated
sepals of Brocchinia and the variously overlapped calyces of some
Cottendorfia species. Foliaceous texture predominates, but succulent (e.g.,
Aechmea fulgens; Fig. 3.2B) to membranous types occur, especially the
latter condition if a bract encloses the calyx (e.g., many Tillandsia subgenus Tillandsia; Fig. 3.3).
Fleshy, colorful calyces augment the attractiveness of some
Bromelioideae to frugivores, especially when fruit set is low (Fig. 3.2B).
Sepals elsewhere in this subfamily probably assist seed dispersal in additional ways. Those of numerous aechmeas mature to sharp spines, perhaps
to encourage frugivores to mash berries and thus release seeds ill equipped
to pass through guts undamaged (Figs. 3.5H, 3.6C; Chapter 6). Identical
service may be provided by the same three appendages combined to a hard,
single sharp projection (Fig. 3.6B). Softer-textured versions of this
arrangement grant foraging birds the grip necessary to remove ripe fruits
from the ¯ at infructescences of certain nidulate bromelioids (Fig. 3.5B).
Corollas are symmetrical except where one petal forms a hood over the
stamens as in some Pitcairnia (Fig. 3.4K) and certain Tillandsioideae such
as T. imperialis. Petal shape ranges from linear to ovate and the margins
from entire through denticulate to ® mbriate (e.g., Tillandsia xiphioides; Fig.
3.3F). Tubular, stiff corollas help de® ne ornithophilous and sphringophilous taxa; those of Tillandsia albertiana seem almost waxy (Fig. 3.3L).
Flared and recurved types mark the bee-serviced species (Fig. 3.3A,F,I).
Yellow, maroon and scarlet occur less commonly than shades of lavender
through white to pale green. Brightly pigmented bracts and foliage dominate the visual signal for many bird-pollinated Bromelioideae and
Tillandsioideae. Similar arrangements highlight the ¯ owers of numerous
Pitcairnia and Navia, among others.
Stamens arise in two whorls of three members each (Fig. 6.1).
Antipetalous ® laments commonly join the corolla base in gamopetalous
species (e.g., Guzmania), and connation distinguishes additional genera
(e.g., Bromelia, Dyckia). Stamen morphology has proven especially informative in relatively well-studied Tillandsia where the disposition of the ® lament, particularly its length and thickness relative to the corolla tube,
identi® es some of the subgenera, although not always as faithfully as some
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Reproductive structure
authorities have presumed (Figs. 3.3, 6.1). Smith (1934a) used the transversely plicate (folded) ® lament (Fig. 6.1C) to circumscribe subgenus
Anoplophytum, but Evans and Brown (1989a) disagreed in part because
similarly modi® ed stamens characterize certain species assigned to congeneric Allardtia and Tillandsia. Folded stamen ® laments also occur elsewhere in Bromeliaceae (e.g., Nidularium ambiguum, Canistrum lindenii).
A complex growth/senescence process recorded by Evans and Brown
(1989a) causes plication in Tillandsia. Soft tissues collapse as the ® lament
ages, allowing it to bend in response to the torsion effected by the now
unconstrained (by turgor) xylem strands. Although the ® lament shortens
as folding proceeds, compensatory growth occurs at its base. Hence, plication does not promote self-pollination by pulling the dehisced anthers
down against the stigma. Perhaps the pleat-like foldings simply enlarge the
tissue mass formed by the six ® laments enough to create a plug-like seal that
retards evaporative concentration of deep-seated nectar. Thickened stamen
® laments that occlude the tubular corollas of certain members of Tillandsia
subgenus Tillandsia native to dry Mexican habitats probably effect the same
outcome (Gardner 1982; Chapter 6; Fig. 6.1A).
Three carpels equipped with U-shaped placentas that fuse progressively
upward during ontogeny characterize the gynoecia of all Bromeliaceae, but
other details vary among taxa (Fig. 3.1; Chapter 12). The orthotropous
ovules can be small and numerous (e.g., Fosterella) to few and larger (e.g.,
some Cryptanthus). Ovary position ranges from superior to inferior in
Pitcairnioideae and Tillandsioideae, in the second subfamily contrary to
Smith and Downs (1977) who report hypogeny throughout except for halfinferior Glomeropitcairnia.
Bromelioideae usually produce fully epigenous ¯ owers that typically
precede berries (Fig. 3.6). Pitcairnioideae illustrate greater variety, sometimes substantial variation among close relatives. Receptacle tissue surrounds all to just part of the ovary of many Pitcairnia, and the ¯ owers of
Brocchinia range from about half to fully inferior. An epigynous tube
obscures the position of the ovary in monotypic Ayensua. Typically hollow
styles range from narrowly cylindric and straight to curved according to the
conformation of the corolla (e.g., many pitcairnias) to short and stout
(Fosterella; Fig. 3.4D).
Bromeliaceae exhibit diverse breeding systems, some accompanied by
conspicuously modi® ed ¯ oral structure. Imperfect ¯ owers occur in one or
more species of Aechmea, Androlepis, Catopsis, Cottendorfia, Cryptanthus,
Hechtia and Lindmania. Aechmea marie-reginae, Androlepis skinneri, more
than half of Catopsis and all of the Hechtia species are dioecious (Fig.
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93
3.3H). Some members of Dyckia warrant closer scrutiny, as do less-studied
Cottendorfia and Lindmania; Cryptanthus subgenus Cryptanthus is
andromonoecious (Chapter 11). Catopsis species range from perfect-¯ owered to dioecious, and arrangements sometimes vary within the same taxon
(Table 6.5). Catopsis pisiformis from Panama illustrates largely hermaphroditic structure that obscures its functional dioecism (Rauh 1983a). Pistillate
plants bear outwardly normal anthers ® lled with nonviable pollen.
Staminate ¯ owers were not described. Elsewhere, organ structure usually
indicates functional competence (e.g., C. floribunda; Fig. 3.3H).
Septal nectaries
Massive septal nectaries may have predisposed Bromeliaceae to exceptional
dependence on vertebrates rather than less demanding insect pollinators.
Organ structure conforms to the `labyrinthine common nectarial cavity'
type (Schmidt 1985), but details vary with other aspects of the ovary (e.g.,
Cecchi Fiordi and Palandri 1982; Böhme 1988; Chapter 12). Varadarajan
and Brown (1988) examined numerous Pitcairnioideae chosen to represent
a range of ¯ oral morphologies and pollination syndromes. They reported
that three longitudinal systems of channels, one per septum, always join
within the ovary axis (Fig. 3.1A). From there, nectar exits through circular
or slit-like ori® ces at locations in¯ uenced by the hypogenous or epigenous
condition of the ¯ ower. Triradiate cavities sometimes extend upward to the
style along circuitous routes.
Glandular tissue occupies different portions of the epithelium lining the
collecting system. Superior-ovaried taxa (e.g., Deuterocohnia schreiteri,
Dyckia ragonesei) possess three additional secondary nectar channels oriented toward the placenta, while half and fully inferior-ovaried gynoecia
(e.g., Pitcairnia heterophylla, Puya harmsii) develop septal channels only.
Simple sugars dominate the relatively dilute secretions (Table 6.3).
Böhme (1988) examined over 90 species representing all three subfamilies in her attempt to identify features of potential systematic signi® cance.
Gynoecial position and the manner in which the three carpels join proved
less consistent than the literature claims. She also reported that the amount
of nectariferous tissue varied, as did its con® guration and that of the collection system. Auxiliary secretory tissue sometimes extended beyond the
gynoecium, occasionally on to the petal bases. Böhme constructed a
scheme to depict nectary evolution, and attempted to reconcile gland structure with ¯ oral biology.
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Reproductive structure
Stigmas
Much information useful for taxonomy and interpretations of reproductive
function resides in the fresh stigma. Brown and Gilmartin (1984, 1989b)
obtained the wet-preserved materials required for the necessary scanning
electron micrographs through a network of collectors at botanical gardens
and other sites scattered through the Neotropics. In all, they examined
material for over 400 species and identi® ed ® ve architectures, viz. conduplicate-spiral, simple-erect, convolute-blade, cupulate and coralliform
(Figs. 3.1C, 12.1; Chapter 12). Essentials of the conduplicate-spiral pattern
emerge early during ¯ oral ontogeny, not long after the carpels appear.
Subsequent growth causes the primordia of many species to change shape,
and ultimately correspond to one of the four apparently derived arrangements (Brown and Gilmartin 1988).
Speci® c stigma types occur discontinuously through the family (Table
3.1). Surveyed Bromelioideae and Pitcairnioideae mostly exhibited the
putatively basic conduplicate-spiral morphology (Fig. 3.1C). Less consistency characterizes Tillandsioideae where every condition occurs in at least
one genus. Catopsis, Tillandsia and Vriesea possess stigmas of two or three
types, although patterns vary less within subgenera (e.g., all Phytarrhiza
examined bore the coralliform type and every available representative of
Diaphoranthema, the simple-erect form). Similar polymorphism characterizes Brocchinia and Fosterella within Pitcairnioideae. Stigma morphology paralleled some additional taxonomic boundaries, and challenged the
validity of others.
Flowers of Guzmania and Mezobromelia, which resemble each other
except for the presence or absence respectively of petal scales on fused
corollas, also possess distinct stigma types (Chapter 12). Cupulate stigmas,
the least common form, appeared only among members of the thecophylloid alliance within Vriesea. Tillandsia subgenus Allardtia, long suspected
to be polyphyletic, duly exhibited both conduplicate-spiral and simpleerect stigmas, whereas species (seven) of Gardner' s Group Five recognized
within subgenus Tillandsia (Chapter 9; Fig. 6.1) alone demonstrated the
simple-erect instead of the conduplicate-spiral form. Tillandsia linearis and
T. xiphioides, already recognized as anomalous within subgenus
Anoplophytum by their lack of plicate stamen ® laments, displayed a conduplicate-spiral rather than the simple-erect stigma of their supposed closest
relatives.
Compared with some other aspects of ¯ ower structure (e.g., placentation, pollen nucleation), the morphology of the bromeliad stigma corre-
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Flowers
Table 3.1. Summary of known distribution of stigma types in the three
subfamilies of Bromeliaceae
Stigma type
Bromelioideae
Conduplicate-spiral
Simple-erect
Convolute-blade
Cupulate
Coralliform
No data
Pitcairnioideae
Conduplicate-spiral
Simple-erect
Convolute-blade
Cupulate
Coralliform
No data
Tillandsioideae
Conduplicate-spiral
Simple-erect
Convolute-blade
Cupulate
Coralliform
Distinctive type
Occurrence
20 genera
Cryptanthus, Orthophytum
None
None
None
5 genera
11 genera (Brocchinia and Fosterella, in part)
Brewcaria, Cottendorfia, Hechtia, Brocchinia, Fosterella
(in part)
None
None
None
Connellia
Catopsis, Mezobromelia, Tillandsia, Vriesea (all or in part)
Catopsis, Guzmania, Tillandsia, Vriesea (in part)
Guzmania, Vriesea (in part)
Vriesea (in part)
Tillandsia (subgenus Phytarrhiza only)
Glomeropitcairnia
Source: After Brown and Gilmartin (1989b).
lates with aridity and reproductive mode. Stigmas belong to the wet type
and accordingly, elevate demands for moisture as surface area increases,
perhaps enough sometimes to compromise ® tness. Simple-erect stigmas
present less of a liability (surface area), and, perhaps not coincidentally,
occur primarily among xerophytic Tillandsia. Stigma type also tends to
accompany certain other ¯ oral characteristics related to breeding system
and the pollen carrier, for example dioecism (Catopsis, Hechtia) and
andromonoecy (Cryptanthus), which are often associated with simple-erect
form. The cupulate type (Fig. 3.1C) that occurs only among the thecophylloid vrieseas may somehow foster reliance on the bats and birds these largebodied bromeliads routinely attract to set fruit.
Varadarajan and Brown (1988) concluded that the degree of compaction
of the lobes and papillae of the stigma of Pitcairnioideae more reliably
identi® es targeted pollinators than coarser structure. Highly condensed,
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Reproductive structure
conduplicately folded, spathulate stigma lobes usually signaled ornithophily (e.g., Pitcairnia corallina, P. meridensis), while those bearing semicompact lobes, with or without papillae (e.g., Ayensua uaipanensis, Puya
aristeguietae), accompanied ¯ owers that regularly attract bats. Stigmas
with ovate to lanceolate, somewhat loosely folded lobes lacking papillae
overoccurred among species rendered entomophilous by small, pale, actinomorphic ¯ owers (e.g., Brocchinia steyermarkii, Deuterocohnia longipetala,
Pitcairnia brevicalycina) born on lax panicles.
Petal scales
Smith and Downs (1974) considered the petal scale, also called a ligule,
nectar scale or lateral fold, one of the premier indicators of generic-level
relationship in Bromeliaceae (Fig. 3.1B). Appendaged corollas characterize about one-third of the family, including at least some members of 14 of
the 27 genera comprising Bromelioideae, six more in Pitcairnioideae, and
three in Tillandsioideae. However, recent ® ndings drawn from studies of
ontogeny question its current broad application as a taxonomic marker,
particularly in Tillandsioideae where presence or absence differentiates
Vriesea from Tillandsia (Brown and Terry 1992). Even Smith and Downs
granted overall similarity greater weight at least once by subsuming
Tillandsia pabstiana under Vriesea drepanocarpa. Petal scales clearly lack
diagnostic value elsewhere in the family, for example in Pitcairnia and Puya
where several species (e.g., Pitcairnia pulverulenta, Puya hofstenii) include
individuals with appendaged and naked corollas.
The bromeliad petal scale assumes a variety of forms at maturity following a more uniform beginning. Development starts with the emergence of
a pair of adaxial excrescences on the base of the expanding petal on either
side of the antipetalous stamen ® lament (Fig. 3.1B). Primordia of
Pitcairnioideae and some Tillandsioideae fuse into a single, variously bi® d
or lobed, tongue-like ¯ ap with an entire margin. Six petal scales characterize the more elaborately appendaged ¯ owers of many Bromelioideae, one
on each side of the three stamen ® laments opposed to the same number of
corolla members. Final shape may be sac or pouch-like with distal lobations or fringes. Accessory lateral folds of undetermined homology embellish some scales. Conversely, those of typically ant-inhabited Aechmea
bracteata remain much simpler, perhaps consistent with small, autogamous
¯ owers and the modest amounts of nectar they produce to encourage outcrossing (Fig. 3.2C).
Brown and Terry (1992) discovered that petal scales emerge shortly
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before the bud expands preparatory to anthesis. Initiation sometimes coincides with microsporogenesis, but usually occurs later along with the postmeiotic, tetrad stage. Most signi® cantly, scales proved to be the last external
multicellular structures to form during petal development. So timed, this
organ can appear and disappear in the evolutionary sense without effecting
fundamental change in corolla structure.
As a `terminal ontogenetic character' , these delicate appendages probably represent recent, minor modi® cations of more deeply seated ¯ oral patterns. If so, features determined earlier during ontogeny should provide
superior markers for genera and higher taxa. A hybrid between Billbergia
nutans (appendaged) and a Cryptanthus (unappendaged) species possessed
petals with scales, suggesting genetic dominance at a single locus. Brown
and Terry (1992) concluded that petal scales represent synapomorphies in
some parts of the family (e.g., possibly several subgenera in Aechmea,
Neoregelia subgenus Hylaeaicum) and homoplasies within groups containing more divergent populations (e.g., Tillandsioideae, Pitcairnia, Puya).
Most of the speculation about petal scale function has focused on intra¯ oral nectar management. Frequent ornithophily and the occurrence of
septal nectaries at the bases of elongated ¯ owers support this contention.
Brown and Terry (1992), Ueno (1989) and Böhme (1988) demonstrated
that the ducts and pore systems occur in different locations to assure
product delivery into capillary rather than noncapillary space located near
the base of the corolla. Nectar consistently exits from points on the gynoecium (superior-ovaried species) or the ¯ oor of the hypanthium (inferiorovaried species) opposite the antipetalous stamens. Scales and other ¯ oral
parts assume various shapes and juxtapositions to elevate columns of
nectar within essentially tubular corollas and stabilize the nectar' s sugar
concentration and viscosity by retarding evaporation, or they guide the
mouth parts of pollinators.
Varadarajan and Brown (1988) obtained information on two Pitcairnia
species that bears on scale function. Speci® cally, they noted how this organ
appears to diminish without reinforcing selection. Pitcairnia brevicalycina
features yellow ¯ owers with or without petal appendages. When present,
the scale is simple to match the accompanying modest nectar production.
Pitcairnia heterophylla (Fig. 2.12A), on the other hand, produces scarlet,
nectar-rich ¯ owers bearing larger scales equipped with elaborate distal
modi® cations.
Bee pollination seems to explain corolla structure and ¯ oral reward in the
® rst species; birds or large moths with comparably high caloric demands
service the second population (Varadarajan and Brown 1988). Although
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Reproductive structure
petal scales assist nectar presentation in Pitcairnia heterophylla, they
appear to be vestigial in Puya brevicalycina. However, nectar scale structure
can be deceptive; even a pair of simple, vertical folds with no discernible
glandular lining held nectar in the corollas of some Puya floccosa populations. Other modi® cations of the bromeliad ¯ ower, such as the coherent,
swollen ® lament bases in some Dyckia, may help maintain reservoirs of
nectar in the absence of scales.
Fruits, ovules and seeds
Fruit type and seed morphology differentiate Bromeliaceae into three subfamilies (sensu Smith and Downs 1974, 1977, 1979; Fig. 3.6), but not as
de® nitively as some taxonomic descriptions imply. Dry capsules and naked
or double-coated seeds with or without appendages characterize
Pitcairnioideae. Seeds equipped with an elaborate ¯ ight apparatus born in
capsules indicate Tillandsioideae (Figs. 3.3H, 3.6J; Chapter 12), while the
berries produced by most Bromelioideae contain naked seeds equipped
with or lacking soft, unbranched appendages (Figs. 3.5G,H, 3.6L).
Exceptions include the fruits of Fascicularia, Ochagavia and Orthophytum
(Bromelioideae), which tend toward dryness, and those of some Pepinia
(Pitcairnioideae) that are just as unexpectedly ¯ eshy. Dehiscence varies
among the capsular types, and at least one Ronnbergia species forcibly
ejects its ripe seeds. Epigeny sometimes prevails where reports indicate
hypogeny (e.g., many Tillandsioideae) and vice versa (e.g., some
Pitcairnioideae).
Bromeliad seeds range from medium to small by angiosperm standards
(e.g., ,0.1 mg for some Pitcairnia), but none approach the proportions of
the minute diaspores produced by the orchids and holoparasites. Those of
terrestrial Bromelioideae exceed the sizes of the seeds of the related epiphytes if the pattern noted in similarly ¯ eshy-fruited Araceae and Cactaceae
also prevails in this subfamily (Madison 1977). McWilliams (1974) determined that the seeds of Tillandsioideae generally weigh less than those of
Pitcairnioideae.
Dispersal modes probably vary more among the bromelioids than
among members of the other two subfamilies (Chapter 6). Mass also varies
more among Bromelioideae. Seeds of some taxa (e.g., Acanthostachys,
certain Bromelia, and Cryptanthus) exceed all others in size, and accordingly, ripen in smaller numbers. A pliable, sticky appendage probably effects
adhesion to substrates and perhaps also to dispersers (Fig. 3.6L).
Embryos usually occupy about one-quarter to one-third of the seed
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Fruits, ovules and seeds
99
Figure 3.7. Embryology of Tillandsia usneoides. Redrawn from Billings (1904).
volume, with starchy endosperm (and some oil in certain taxa) making up
the balance (Fig. 3.7). Development is helobial according to Davis (1966).
Billings (1904) described embryology in Tillandsia usneoides as conventional for monocots, but polyembryony occurs in some close relatives (Figs.
3.6K, 3.7). Gross (1985) surveyed 11 species of Tillandsia subgenus
Diaphoranthema and discovered one to four embryos in at least the occasional seed of all but T. recurvata. If more than one progeny was present,
the largest of the group appeared to be zygotic and the others of undetermined origin and positioned lateral to it. More endosperm remained in
seeds bearing one compared with multiple embryos.
The outermost layer of the endosperm consists of starch-free, cubical
cells containing darkly pigmented, granular materials. Szidat (1922) suggested its identity as an aleurone layer. If so, component proteins, like those
of the cereals, probably promote germination by mobilizing food reserves
for growing embryos. Thin-walled endosperm tissue deeper in the seed contains abundant starch, usually as lenticular grains. Elongated cotyledons
equipped for absorption occupy the distal end of the seed where they
remain, rendering germination hypogeal (Figs. 3.7, 3.8). Intercalary growth
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100
Reproductive structure
Figure 3.8. Germination. (A) Canistrum lindenii. (B) Pitcairnia flammea. (C) Vriesea
scalaris.
near the base of the hypocotyl pushes part of that organ and the adjacent
radicle through the testa. Seedlings of Tillandsioideae fail to produce roots
for weeks to months (Fig. 3.8C). The greatest delays characterize neotenic
Tillandsia.
Several features describe the ovules and seeds of Bromeliaceae, for
example anatropous morphology, two layers of cells comprising each of
the two parts of the integument, predominantly starch reserves, and a rel-
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Fruits, ovules and seeds
101
Figure 3.9. Seed types and seed phylogeny in Pitcairnioideae. Redrawn from
Varadarajan and Gilmartin (1988b).
atively small embryo (Billings 1904; Fig. 3.7). Some endosperm always
remains to nourish the young seedling. Mature seeds provide numerous
potentially informative, but little-utilized, traits for taxonomy (Gross
1993). Seed morphology varies far more than most of the literature suggests.
A closer look at the development of the outer seed coat seems advisable
to evaluate several suggestive similarities, including possible homologies
between the ¯ ight apparatus of Brocchinia tatei and Tillandsioideae, especially Glomeropitcairnia (Varadarajan and Gilmartin 1988b; Figs. 3.9,
6.1D; Chapter 12). Navia seeds exhibit an interesting parallel with those of
Bromelioideae: both lose the outer integument during development,
although conditions differ at maturity as described below (Fig. 3.9). The
sticky strand of material (funiculus) that helps fasten the seeds of many
Aechmea species (e.g., A. angustifolia; Fig. 3.6L) to substrates appears to be
derived from the testa.
Searches for ever ® ner structure for systematic and functional analysis
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102
Reproductive structure
continue. Several classical papers (e.g., Poisson 1877; Szidat 1922;
Netolitzky 1926) report modi® cations of the outer testa that in¯ uence seed
mobility. However, neither these studies nor the others published since
exhaust the possibilities for major revelations about family history, and
how aspects of dispersal and seedling establishment favor success on speci® c kinds of substrates. For example, Palací (1997) discovered that the
coma of Catopsis (Fig. 3.3H) is not homologous with the ¯ ight apparatus
of the other Tillandsioideae, further underscoring the isolation of this
genus within its subfamily. Conceivably, Catopsis evolved capacity to disperse among aerial substrates independently. If so, epiphytism and lithophytism, although nearly universal through Tillandsioideae, could well be
homoplasious.
Bromelioideae
Seeds of Bromelioideae reportedly lack appendages, and the outer integument simply degenerates to augment the gelatinous pulp that ® lls much of
the often tough husk of the ripe berry (Smith and Downs 1974). Figure
3.6L illustrates some exceptions. Seeds in some cases possess unique qualities that seem likely to encourage transport or adhesion to substrates,
perhaps in the second instance acting like the viscin threads of some mistletoes. Seeds of several ant-nest taxa promote myrmecochory with alluring chemicals (Chapters 6 and 8), and closer examination might reveal that
some of the material attached to the seed constitutes tissue evolved to serve
as ant food. Seeds of Bromelioideae (Ronnbergia) that disperse ballistically
remain little studied. Self-fertile Ronnbergia petersii germinates within the
pear-shaped, orange (mammal-dispersed?) fruits that contain about 100
seeds, each enveloped in a gelatinous coat. Aechmea dactylina behaves similarly (Fig. 3.6B).
Authoritative sources (e.g., Smith and Downs 1979) describe
Bromelioideae as baccate, which ® ts reality except for those few, relatively
dry-fruited exceptions just mentioned. However, this designation conveys
no information about the likely consequences of the diverse colors, sizes,
textures and nutritional values of the berries most of these plants produce
(Chapter 6; Table 6.7). Shape and seed number per fruit surely in¯ uence
appeal and access to vectors and substrates. For example, Madison (1979)
suggested that size and form may help some species employ pupal mimicry
to support ant-garden status (e.g., Aechmea mertensii). One ¯ at side on the
seeds of certain epiphytes (Aechmea bracteata, Billbergia elegans; Fig.
3.6H) may promote sufficient contact with bark to counter gravity.
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Fruits, ovules and seeds
103
Aechmea magdalenae, a widespread terrestrial through Central America
south to Ecuador, produces elliptical seeds that seem better suited to germinate on substrates other than bark (Fig. 3.6H).
Thick-walled sclerids forming the outer seed coat provide the protection
the embryos and endosperm of zoochorous ¯ ora require (e.g., Billbergia
elegans, B. rosea; Fig. 3.6I). Inner integuments consist of two layers of
heavily scleri® ed cells that vary enough among taxa to distinguish certain
genera. Associated differences in hardness and resistance to corrosive gut
secretions and grinding crops may reveal specializations for ingestion by
mammals vs. avians.
Tillandsioideae
Seeds of Tillandsioideae feature a plumose coma or ¯ ight apparatus of
varied construction and homology (Figs. 3.6J, 6.5D,G; Chapter 12).
Development occurs in septacidal capsules of diverse proportions and
anatomy depending in part on the position of the ovary. The testa accounts
for the ¯ ight apparatus, but differently depending on the genus. Typically,
the outer integument closely invests the seed until near maturity when it
separates from the inner integument except at the base and becomes a
three-layered series of long, hair-like extensions. Both outer layers form the
umbrella-like portion of the coma and the inner layer, which remains
attached to the seed proper, its handle (Fig. 3.6J). A much less elaborate
apical plume contributes some additional buoyancy to most seeds.
Catopsis exhibits a ¯ ight apparatus comprised of elongated cells (true
hairs with hooked ends) that extend off the seed apex. The short capsule
forces the developing coma to remain folded until dehiscence, causing its
kinky morphology (Fig. 3.3H). The inner integument is similarly ® brous,
but coherent at maturity and sufficiently unique to differentiate groups of
species, perhaps what could be members of valid genera. Szidat (1922) and
Röhweder (1956) described the tillandsioid coma in great detail, as did
Gross (1988a) during her search for seed morphologies valuable for systematic analysis. Walls of the component cells bear potentially signi® cant pits
and ornamentations. Hairs of some Guzmania and Tillandsia species
exhibit bifurcate cross-walls that may favor adhesion to speci® c kinds of
surfaces, perhaps bark vs. rock to match epiphytic or saxicolous habits (Fig.
6.5D).
Usually the ¯ ight apparatus extends off the base of the seed with only a
short plume at the opposite end (Fig. 3.6J). Sometimes the apical extension
consists of no more than a short, membranous hood. However, the apical
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104
Reproductive structure
plume in Tillandsia grows much longer and divides into multiple parts;
Vriesea subgenus Alcantarea (genus Alcantarea according to Grant
1995a,b) illustrates the opposite condition. Here, relatively short appendages extend from both ends of the fusiform seed, perhaps consistent with
strong selection against buoyancy as highly insular saxicoles in southeastern Brazil (Fig. 1.2C). Experiments conducted by McWilliams (1974) and
Bennett (1991) indicated that the architecture of the ¯ ight apparatus of
Tillandsia, its mass relative to that of the seed proper, and structural details
affect seed mobility and possibly securement to speci® c kinds of substrates
(Chapter 6).
Pitcairnioideae
Pitcairnioideae, like Tillandsioideae, produce capsules and dry seeds, but
morphology diverges more in the ® rst subfamily, consistent with recognition of roughly twice the number of genera. Conversely, most
Pitcairnioideae feature seeds equipped with entire-margined appendages,
and no member is particularly well equipped for long-distance dispersal by
the form of its propagules (Fig. 3.9). A few species reputedly rely on ants
or water to disperse (Chapter 6). A bipartite testa develops except for Navia
where only the inner layer remains at maturity. Here, as elsewhere through
the subfamily, a scleri® ed inner integument protects the embryo and endosperm. The outer portion forms a hump or wing on the back and apex of
the ovules of Puya and Pitcairnia, and sometimes extends over the apex on
the ventral side nearly to the micropyle (Fig. 3.9).
An almost circumferential wing distinguishes the diaspores of Pepinia,
some Puya, and members of several other genera. Seeds of additional taxa
(e.g., Cottendorfia, Brocchinia, Fosterella) bear appendages comprised of
clusters of sharp-pointed ® bers extending from one or both ends of the
seed (Figs. 3.9, 6.1D). Glomeropitcairnia penduliflora (Tillandsioideae)
exhibits a ¯ ight apparatus up to 2 cm long, at least outwardly suggestive of
affinities between the two capsular subfamilies. Again, seeds contain proportionally massive endosperms and small embryos. Germination exposes
the basal part of the cotyledon, which soon becomes green and laminar
(Fig. 3.8B).
More structural variety exists among the seeds of Pitcairnioideae than
among either of the other two subfamilies. Varadarajan and Gilmartin
(1988b) divided Pitcairnioideae into six groups according to seed morphology, and hypothesized an ancestral, `unadorned' simpler form (Fig. 3.9).
Some modi® cations of the integument correspond to individual genera (the
Cambridge Books Online © Cambridge University Press, 2009
Pollen grains
105
`Brocchinia type' and `Navia type' ), while others, for example the `Fosterella
type' , likely evolved repeatedly, in this case in Abromeitiella, Ayensua,
Connellia, Deuterocohnia, Fosterella, Hechtia and Pitcairnia. Particularly
interesting are the seeds of Brocchinia, especially the condition of the basal
appendage. Only a simple or digitate projection occurs in the examined terrestrial forms (e.g., B. acuminata, B. reducta); its condition in often epiphytic B. tatei suggests the ¯ ight apparatus of Tillandsioideae (Figs. 3.9,
6.1D).
Pollen grains
Taxonomists account for virtually every publication on bromeliad pollen,
and none of these reports suggest strong correlations between morphology
and either related functions (e.g., type of pollinator, breeding system) or
taxonomic boundaries (e.g., Halbritter 1988, 1992; Chapter 12). Androlepis
and Hohenbergiopsis disperse pollen in tetrads while the other grains separate. Walls vary from smooth to reticulate or foveolate (Fig. 12.2). Three
aperturate types occur: porate (exclusively Bromelioideae), inaperturate
(various Bromelioideae and Tillandsioideae), and sulcate (Pitcairnioideae
and Tillandsioideae), indicating much homoplasy in grain morphology, or
insufficient resolution to recognize subgroups within larger, arti® cial categories. Pollen grain morphology remains largely untested for utility in
tracing Bromeliaceae through the fossil record (Chapter 9).
Cambridge Books Online © Cambridge University Press, 2009
Cambridge Books Online © Cambridge University Press, 2009
4
Carbon and water balance
Temperate zone ¯ ora dominate the early literature on plant ecophysiology,
but Bromeliaceae account for a disproportionate number of the tropical
species studied during this period. Billings (1904) recorded moisture
exchange during his inquiry on the biology of Spanish moss. Mez (1904)
and several European contemporaries demonstrated how the foliar trichome of this same epiphyte and comparable Tillandsioideae eliminates
need for absorptive roots. Harris (1918) contrasted osmotic pressures in the
leaves of trees and associated bromeliads and co-occurring vascular epiphytes in Florida and Jamaica.
Wherry and Capen (1928) surveyed Tillandsia usneoides growing along
Florida highways for its capacity to accumulate nutrients and certain technological metals. Research on pineapple metabolism began in earnest
during the late 1930s. Finally, Leopoldo M. Coutinho included numerous
Bromelioideae and Tillandsioideae in his pioneering investigations on the
pathways responsible for CO2 assimilation by diverse Brazilian ¯ ora (e.g.,
Coutinho 1963). Since then, a growing number of scientists have been
measuring gas exchange, chlorophyll ¯ uorescence and other indicators of
plant performance and physiological state to expand the database on
Bromeliaceae.
Current records of carbon ® xation pathways, many accompanied by
data on water balance and light relations, document the ecostrategies of
more bromeliads than of members of any other family (Martin 1994; Table
4.1). Moreover, concerns about issues ranging from global change to
drought-tolerance assure continuing interest in the ecology and evolution
of Bromeliaceae. Ananas comosus, Aechmea magdalenae, Bromelia humilis,
Tillandsia usneoides and Guzmania monostachia constitute the best-known
species; less complete pro® les of many more taxa further attest to the
exceptional variety of growing conditions these plants experience in situ.
107
Cambridge Books Online © Cambridge University Press, 2009
Table 4.1. Details of photosynthesis for representative bromeliads
Taxon
Photosynthetic
pathway
D value
A
Light
Light
compensation
saturation
Apparent
intensity
intensity
quantum
(mmol m22 s21) (mmol m22 s21)
yield
Bromelioideae
Aechmea magdalenae
Aechmea magdalenae
Ananas comosus
Ananas comosus
(high light-grown)
Ananas comosus
(shade-grown)
Ananas comosus
Bromelia humilis
Bromelia humilis
(shade-grown)
Bromelia humilis
(high light-grown)
Bromelia humilis
Cryptanthus bromelioides
Neoglaziovia variegata
Nidularium innocentii
Wittrockia campos-portoi
Ð
CAM
CAM
Ð
C3± CAM?
Ð
Ð
2.0 mmol m22 s21
216.2
Ð
213.4
Ð
Ð
2.2 µmol g21 dry weight s21
223.1
Ð
Pitcairnioideae
Pitcairnia integrifolia
Pitcairnia integrifolia
Pitcairnia flammea
Puya floccosa
Puya copiapina
Puya ferruginea
Ð
Ð
C3
C3± CAM?
CAM
C3
Ð
Ð
227.9
222.5
215.4
224.8
Tillandsioideae
Catopsis nutans
Catopsis nutans
Guzmania monostachia
Guzmania monostachia
Guzmania lingulata
Guzmania lingulata
Tillandsia usneoides
Tillandsia usneoides
Tillandsia usneoides
Vriesea simplex
C3± CAM?
Ð
C3± CAM
Ð
Ð
_
CAM
Ð
Ð
C3
223.7
Ð
Ð
Ð
223.7
Ð
Ð
0.69 µmol CO2 m22 s21
Ð
Ð
Ð
1.6 µmol CO2 m22 s21
213.7
Ð
Ð
Ð
Ð
4.8 µmol g21 dry weight s21
224.4
Ð
CAM
Ð
CAM
215.5
Ð
Ð
0.3 mmol CO2 m22 s21
213.5216.5
Ð
Ð
Ð
Ð
Ð
CAM
Ð
212.1
Ð
Ð
Ð
Ð
Ð
Ð
Ð
Ð
50
Ð
2.2 mmol m22 s21
Ð
26
Ð
Ð
Ð
Ð
Ð
Ð
Ð
Ð
Ð
Ð
Grif® ths and Smith 1983
P® tsch and Smith 1988
Medina et al. 1991a
0.07
Borland and Grif® ths 1989
0.03
Ð
Ð
Borland and Grif® ths 1989
Borland and Grif® ths 1989
Grif® ths and Smith 1983
10
1000
0.09
Fetene et al. 1990
1000
Ð
Ð
Ð
Ð
Ð
0.08
Ð
Ð
Ð
Ð
Ð
Fetene et al. 1990
Medina et al. 1991b
Medina et al. 1991b
Medina et al. 1991b
McWilliams 1970
Medina et al. 1977
13
300
Ð
Ð
Ð
Ð
Ð
0.03
Ð
Ð
Ð
Ð
Ð
Lüttge et al. 1986a
Lüttge et al. 1986a
Medina et al. 1977
Medina and Troughton 1974
Medina et al. 1977
Medina et al. 1977
Ð
50
Ð
1000
Ð
Ð
600
Ð
250
250
Ð
Ð
Ð
Medina and Troughton 1974
Benzing and Renfrow 1971b
Medina and Troughton 1974
Maxwell et al. 1995
Grif® ths et al. 1986
Grif® ths et al. 1986
Medina and Troughton 1974
Martin et al. 1986
Martin et al. 1986
Grif® ths and Smith 1983
Ð
Ð
Ð
Ð
Ð
33
Ð
Ð
Ð
Ð
Ð
Ð
Ð
5 µmol CO2 m22 s21
Ð
Ð
Ð
Ð
Ð
Ð
Reference
Ð
Ð
Ð
20
Ð
50
80
Ð
Ð
Cambridge Books Online © Cambridge University Press, 2009
Ð
Ð
Ð
0.01
Ð
Ð
Ð
Ð
Ð
110
Carbon and water balance
On-going inquiry promises to produce additional revelations, perhaps even
unrecognized stress-moderating mechanisms, in one or more of the drygrowing species. This chapter considers the data, critiques its interpretations, and identi® es promising avenues for additional research.
Ecophysiological peculiarities
Capacity to tolerate often hostile substrates and harsh climates in diverse
tropical and subtropical American habitats helps distinguish many
Bromeliaceae from most of the other ¯ owering plants. Additional ¯ ora also
accommodate considerable aridity and impoverished rooting media, but
few of these plants draw nutritive ions and moisture from the same unconventional sources. More than half of the bromeliads obtain moisture
directly from the atmosphere, or from aquatic impoundments located
among overlapping leaf bases rather than soil (Fig. 5.1). And no family
comes close to matching Bromeliaceae for the variety of media and the
mechanisms and devices members utilize for mineral nutrition.
Occasional bromeliads grow in permanent seepages or marshes, or they
root in seasonally saturated soils (e.g., some Brazilian Pitcairnia flammea
and a number of Bromelioideae). The more exceptional population tolerates periodic submergence in fast-moving streams (Fig. 1.4G). Climatically
arid habitats or dry microsites at wetter locations characterize much more
of the family. Xerophytes abound and include the over-represented epiphytes and lithophytes, many of which rival the other exceptionally stress-tolerant terrestrial ¯ ora for capacity to survive protracted dry weather solely
on moisture stored in succulent foliage (Figs. 2.2A,B, 2.13B). High-altitude
Bromeliaceae endure UV-B-enriched insolation and freezing nights
assisted by woolly, light-scattering indumenta and dense accumulations of
anthocyanins (Figs. 7.2± 7.4). Different combinations of shoot architecture
and pigment display enhance light harvest deep in the forest understory in
the manner described below.
Mineral nutrition remains the least-studied facet of bromeliad ecophysiology. Chapter 5 addresses this subject by considering sources and the
plant devices employed to absorb required ions. Additional aspects of
nutrition that in¯ uence carbon budgets and water balance following uptake
have also received some attention. Complex interactions among plant
nitrogen and moisture status and photosynthetic photon ¯ ux density
(PPFD) characterized Ananas and Bromelia species monitored in situ and
in the laboratory, but impacts on ® tness remain unclear, as we shall see. If
exceptionally ¯ exible ecophysiology turns out to be a hallmark of
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The five ecophysiological types
111
Bromeliaceae, it should be no surprise given the family' s frequent dependence on supplies of moisture and nutrients that tend to be scarce, transitory, and unavailable to most other ¯ ora.
The literature contains so much information on the carbon and water
relations of Bromeliaceae that an exhaustive coverage would likely deter all
but the most dedicated reader. Therefore, I have segregated the family into
® ve ecological/functional (ecophysiological) types to facilitate comparisons. Table 4.2 lists the de® ning characteristics of each type, and cites familiar, representative species. Pittendrigh (1948), impressed by observations
recorded by Schimper (1884, 1888, 1898), Tietze (1906) and others, re® ned
their four-parted scheme based on sources of moisture and nutrients (soil
vs. atmosphere) and the plant devices (foliar trichomes vs. roots) used to
access them to organize his ® ndings on Bromeliaceae in Trinidad. I follow
this arrangement except where important differences warrant dividing Type
Three in the old system into two new ones.
The five ecophysiological types
Pittendrigh' s Type One, the `soil root' group, matches mine (Table 4.2).
Members root exclusively in media characterized by plentiful supplies of
water (e.g., moist mineral soils, rocks with deep ® ssures) at least through a
wet season. Degrees of xeromorphy and photosynthetic pathway vary,
obliging requirements for more or less continuous (e.g., mesophytic
Pitcairnia and Fosterella; Fig. 2.16B,C) to intermittent (e.g., dry-growing
Hechtia and Dyckia; Fig. 1.2A) access to soil moisture. Plant architecture,
faithful to the division of labor between shoot and root systems, follows the
fundamental monocot pattern, which probably also represents the basic
condition for Bromeliaceae as a whole (Fig. 2.20). Foliage routinely performs little if any of the absorptive function that allows the more specialized bromeliads to dispense with roots except for holdfast. Two subfamilies,
Bromelioideae and Pitcairnioideae, contribute species to this ® rst and most
fundamental of the ® ve ecological types.
Type Two corresponds to Pittendrigh' s second, `tank root' designation,
and, like his examples, species included here possess somewhat succulent
foliage with modestly dilated bases (Fig. 2.14A,B). Enough moisture and
nutrient-rich debris collects in the upright shoot to meet plant needs via
apogeotropic roots and relatively unspecialized, absorptive trichomes.
Roots of cultivated pineapple, which may access soil moisture more
effectively than those of some of the other Type Two bromeliads, supplied
less water to transpiring shoots than those serving an adjacent stand of
Cambridge Books Online © Cambridge University Press, 2009
Table 4.2. The five ecological types: basic characteristics and occurrence in Bromeliaceae
Root system
Shoot architecture
Foliar trichomes
Photosynthetic
syndrome
Habit
Type I
Absorptive soil
roots
No phytotelma
Nonabsorptive
C3 or CAM
Terrestrial
Most Pitcairnioideae/
many Bromelioideae
Type II
Absorptive soil
and apogeotropic
roots
Weakly developed
phytotelma
Absorptive on leaf
bases
CAM
Terrestrial
Bromelioideae
Type III
Mechanical to
conditionally
absorptive
Well-developed
phytotelma
Absorptive on leaf
bases
Mostly CAM
Terrestrial/
saxicolous/
epiphytic
Bromelioideae
Type IV
Mechanical to
conditionally
absorptive
Well-developed
phytotelma
Absorptive on leaf
bases
Mostly C3
Mostly epiphytic
Tillandsioideae
and a few
Brocchinia species
Type V
Mechanical or
missing
No phytotelma,
often neotenic and
miniaturized
Absorptive over
entire shoot
CAM
Mostly saxicolous
or epiphytic
Tillandsioideae
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Taxonomic
distribution
The five ecophysiological types
113
Bermuda grass in one set of ® eld tests (Ekern 1965). Except perhaps for a
few species of Brocchinia (e.g., B. vestita; Fig. 5.3D), Bromelioideae ± most
notably certain members of Ananas and Bromelia ± constitute Type Two,
and soil and rocks rather than bark usually sustain these plants.
My Types Three and Four represent taxon-distinct segregates of
Pittendrigh' s Type Three, or what he called the `tank absorbing trichome'
group. Members of both new categories produce sizable phytotelma from
which the bases of mature foliage and perhaps the entire surfaces of the
wholly submerged, younger leaves draw moisture and nutrient ions; roots
provide anchorage and conditionally (contingent on the quality of the
medium) augment mineral nutrition and water balance (Figs. 1.2E,G, 2.4).
Simultaneous feeding through roots and shoots promoted superior growth
among some cultivated bromeliads compared with either route alone (e.g.,
Sieber 1955), but shallow to impenetrable media often oblige nearly complete reliance on phytotelmata in situ. Assignment to Type Three (all
Bromelioideae) or Type Four (impounding Tillandsioideae and some
Brocchinia) also distinguishes the `phytotelm' or `tank' bromeliads according to the prevailing photosynthetic mechanisms (Type Three, predominantly CAM; Type Four, mostly C3), and whether the foliar trichomes
possess low or higher absorption capacity (Type Three, low; Type Four,
higher).
Pittendrigh' s fourth category, the `atmospheric, absorptive trichome'
bromeliads, equals my ® fth type (Figs. 1.3A,C, 2.1). Members lack capacity to impound water or solids (except ant-provisioned materials in the case
of the myrmecophytes) in leaf bases, and roots, if present, lack signi® cant
absorptive capacity. Instead, these bromeliads depend on dense indumenta
of air-exposed foliar scales (Figs. 2.7, 2.8C,E, 4.23E± H). Type Five species
represent the ultimate response among Bromeliaceae to the challenges
imposed by multiple, physical stresses. However, similar leaf specializations, particularly pronounced succulence, belie the needs of some of these
`atmospherics' for frequent irrigations. Many a Type Five bromeliad, for
example Spanish moss, holds moisture less tenaciously than certain relatives with nonabsorptive indumenta (e.g., many Dyckia and Hechtia
species).
Transitional forms abound, especially between Types Two and Three and
Types Four and Five. The usefulness of this ® ve-parted classi® cation, essentially appreciation of the ecophysiological variety it organizes, requires
some preparatory discussion of photosynthesis and related aspects of
water balance.
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Carbon and water balance
Photosynthesis and water economy
Bromeliads face the same dilemma experienced by virtually all land-based
¯ ora: they must obtain CO2 without losing too much moisture. Simply put,
transpiration (E) always accompanies photoassimilation (A) unless conducted in a water-saturated atmosphere, a rare event even deep within the
everwet tropical forest. Vegetation with more or less continuous access to
moisture usually operates with relatively poor water-use efficiency (WUE5
water expended divided by CO2 ® xed). The xerophytes, a different subset of
¯ ora united solely by capacity to counter drought, operate differently.
Unlike their less water-constrained, hence more mesic, counterparts, the
xerophytes either reduce the ratio of moisture transpired to dry matter
accrued (the drought-endurers), or foliage is shed with timing that precludes losses sufficient to cause serious injury (the drought-avoiders).
At greatest potential risk of life-threatening desiccation among
Bromeliaceae are the members of Type Five (all evergreen, and therefore
drought-endurers) that experience frequent high evaporative demand while
rooting on naked bark or rock or supported by arid-land soils. More than
the rest of the family, these plants must obtain CO2 from air that is often
characterized by high vapor pressure de® cits (VPD), and they depend on
modest, often temporary, sources to rehydrate. Xerophytic Bromeliaceae,
like similarly adapted vegetation belonging to about 25 other families,
greatly improve WUE through deployment of a complex mechanism or
`syndrome' called crassulacean acid metabolism (CAM). CAM fosters nonautotrophic (dark) CO2 uptake from what tends to be relatively water-saturated night, compared with daytime, air.
Severe climates and substrates incapable of storing moisture explain the
frequent occurrences of absorptive trichomes, succulence, impounding
shoots and CAM among members of Bromeliaceae. Of the approximately
225 species for which records exist (Martin 1994), about two-thirds exhibit
some version of CAM. In fact, bromeliads demonstrate both the versatility of this syndrome as an ecophysiological response to multiple physical
stresses and the ease of its derivation from more fundamental C3-type
photosynthesis. Reversals, perhaps encouraged by historic shifts in climate
or the geographic ranges of ¯ ora, mark certain Bromelioideae and perhaps
additional lineages in the other two subfamilies (Chapter 9). So far, no compelling evidence indicates C4 photosynthesis anywhere in the family,
although some suggestive leaf anatomy makes a case for looking more
closely at certain Tillandsioideae.
Table 4.1 provides a sample of Bromeliaceae selected to illustrate the
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Crassulacean acid metabolism: basic characteristics
115
family' s mixed ecophysiological composition and the close phylogenetic
juxtapositions of C3 and CAM populations in Pitcairnioideae and
Tillandsioideae. Bromelioideae appear to be most fundamentally disposed
to CAM, with largely montane, wet-growing Greigia (26 species) comprising the largest clade among the exceptions. Other C3 species scatter through
small and larger genera (e.g., Nidularium burchellii, N. innocentii), probably
also as evolutionary retrogrades. Likely additions (e.g., mesomorphic
Ronnbergia) would not alter this tally much considering the documented,
near to complete CAM status of all the largest genera (Aechmea, Billbergia,
Bromelia, Neoregelia) and most of the medium-sized ones (e.g.,
Cryptanthus, Quesnelia, Orthophytum; Martin 1994). Ancestors probably
operated in the C3 mode prior to evolving the current array of variations
on CAM present in descendants, but when, where and how often remain
unclear (Chapter 9).
Crassulacean acid metabolism: basic characteristics
Crassulacean acid metabolism has attracted extraordinary attention
because of its pervasiveness and importance in many kinds of habitats.
Occurrences in about two dozen families of ¯ owering plants, Gnetophyta,
several fern genera, and Isoetes of Microphyllophyta indicate ancient
origins and broad utility, or at least compatibility, with other plant characteristics and diverse growing conditions. Performance varies among CAMequipped ¯ ora, and sometimes shifts within the same individual and even
the same organ during ontogeny. Lüttge et al. (1986b) recorded differences
in several measures of CAM among leaves born by the individual shoots of
Aechmea aquilega specimens in Trinidad, and even from one part to
another of the same blade! Variation also tracks the seasons and certain
less predictable environmental events, particularly those that affect plant
moisture status.
Little beyond reliance on phosphoenolpyruvate carboxylase (PEPc) to
® x CO2 at night during at least part of the life cycle unites thousands of
species under the label CAM-equipped ¯ ora. Included are the obligate
(constitutive) types, the `switchers' or facultative CAM plants, the CAMcyclers, and the additional, less-studied forms with even more puzzling patterns of carbon management, gas exchange and related leaf anatomy (e.g.,
Peperomia; Ting et al. 1985). CAM-cyclers behave like C3 plants by taking
up CO2 during the day, but also re® x (recycle) carbon respired at night to
malic acid as described below for CAM. All CAM types probably CAMidle, which means that whenever drought reduces stomatal conductance (g)
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Carbon and water balance
to zero, respired CO2 alone fuels acidi® cation, and during the day allows
enough photosynthesis for plant maintenance.
CAM plants adjust WUE and CO2 exchange in response to a variety of
external cues and metabolic states depending on the genotype and previous
and immediate growing conditions. Speci® c determinants include photoperiod, thermoperiod, plant nitrogen status, bulk tissue water potential
(Cleaf), salinity, VPD in adjacent air, and light intensity. Enhanced water
and carbon economy impart bene® t in arid locations, but other advantages
can accrue where challenges differ.
Martin' s (1994) demonstration that elevated CO2 (to 430 ppm) doubled
peak tissue acidity (H1max) in Tillandsia ionantha supports Knauft and
Arditti' s (1969) suggestion that CAM may appreciably improve carbon
budgets where abundant respiration (e.g., forest understory) elevates
ambient partial pressures at night. Some aquatic macrophytes, including
certain Isoetes, deploy CAM in the same way to increase access to dissolved
CO2 in soft-water (low carbonate) lakes. Enhanced N economy and
perhaps the same for other scarce nutrients and more effective harvest of
the radiant energy in sun ¯ ecks probably promote ® tness for bromeliads in
a variety of habitats. CAM also helps protect Guzmania monostachia
against photodamage (Maxwell et al. 1992, 1994, 1995).
CAM-equipped land ¯ ora experience heightened water economy in
part because PEPc compared with ribulose bisphosphate carboxylase/oxygenase (RuBPc/o), its functional equivalent in the photosynthetic carbon
reductive (PCRC or C3) pathway, exhibits the higher affinity for CO2.
This same quality is central to its role as mediator of CAM as the CO2cocentrating enzyme. Most importantly for dry-growing Bromeliaceae,
PEPc permits plants to accumulate (concentrate) a carbon supply at night
for photosynthesis later. If employed in lieu of some of the RuBPc/o,
invested by an otherwise comparable C3 plant, the lower molecular weight
of PEPc also improves nitrogen-use efficiency. Yet despite knowledge of
these multiple bene® ts and the additional ® ndings on the mechanisms discussed below, questions persist about why CAM plants occur under such a
variety of growing conditions.
Different CAM plants and the same individuals under different conditions vary in their proportional dependencies on PEPc and RuBPc/o to
harvest CO2 from air. Facultative compared with constitutive types track
changing environments, alternating between C3 and CAM photosynthesis
as the season and other plant and more site-speci® c circumstances change.
Additional features that distinguish the different expressions of CAM,
some with no documented bene® ts, include the nature of the carbon/energy
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Bromeliad CAM: basic characteristics
117
reserves utilized to generate the PEP, reducing power and adenosine triphosphate (ATP) necessary to trap CO2 from night air, the growing conditions and plant status that promote CAM-idling, and the relative quantities
of citrate to malate accumulated during dark CO2 ® xation and metabolized
during the day.
Bromeliad CAM: basic characteristics
Bromeliad CAM conforms to the pattern ® rst recorded for certain
Crassulaceae. Although succulence is usually less developed than for much
of the other dry-growing ¯ ora with the same photosynthetic pathway (e.g.,
Agavaceae, Cactaceae), both carboxylases operate in green mesophyll cells.
Additionally, the two proteins function mostly at different times of the day,
which minimizes futile CO2 recycling. Here too (Table 4.1), 13C in biomass
compared with its presence (relative to 12C) in the atmosphere expressed in
parts per thousand (½ , or D), indicates the photosynthetic syndrome.
Both C4 and CAM plants discriminate less against the heavier carbon
isotope 13C (as 13CO2) than do the C3 types. The D values for biomass produced by CAM and C4 ¯ ora range between 28 and 222½ vs. between
approximately 223 and 235½ for subjects that depend exclusively on the
PCRC pathway (Fig. 4.1). Values at midrange, if not in¯ uenced by a biased
source (e.g., decomposing C3 biomass), signal substantial ® xation of CO2
from the atmosphere by both carboxylases (facultative CAM). Certain
other phenomena that affect the diffusion of CO2 through the leaf to the
chloroplasts also in¯ uence D.
Unlike C3 and C4 types which assimilate CO2 exclusively by day, ¯ ora
operating in the CAM mode, as exempli® ed by Tillandsia usneoides (Fig.
4.2), do so predominantly at night. Carbohydrates, either soluble sugars or
starch and glucans, provide the necessary energy, reductant, and carbon
skeletons. Beta carboxylation of PEP and subsequent reduction of the
resulting oxaloacetate to malic acid constitute the CO2 capture and storage
processes, or what is known as phase one (Fig. 4.2). A relatively brief burst
of CO2 uptake around sunrise (phase two) before the stomata close involves
® xation by both carboxylases, primarily PEPc at ® rst with gradual replacement by RuBPc/o.
As the day progresses, CO2 generated by the decarboxylation of the malic
acid mobilized from the vacuole reaches concentrations several times
ambient (the CO2-concentrating mechanism), and reprocessing via the
PCRC pathway continues (phase three). Elevated concentrations of CO2
suppress photorespiration and inhibit the accumulation of photo-oxidative
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Carbon and water balance
Figure 4.1. Distribution of 13C enrichment values (13C or D) among species representing the three subfamilies of Bromeliaceae (after Medina 1990).
Figure 4.2. CO2 exchange by Tillandsia usneoides with the four phases of CAM indicated (modi® ed from Martin and Siedow 1981).
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Bromeliad CAM: basic characteristics
119
reactants that could impair the light-harvesting apparatus in overexposed
foliage (Maxwell et al. 1992, 1994, 1995). Well after midday, with the malic
acid supply exhausted and respiration now the sole source of CO2 for
photosynthesis, stomata reopen allowing PEPc and RuBPc/o access once
again to CO2 in the atmosphere (phase four; Fig. 4.2).
In one study (Cote et al. 1989) about 50% of the CO2 consumed by wellwatered Ananas comosus from about the middle of phase four to dusk accumulated as malate. Reinert et al. (1995) demonstrated simultaneous
involvement of PEPc and RuBPc/o by measuring the isotopic composition
of CO2 in air passing over the shoots of Neoregelia cruenta in a Brazilian
restinga (Fig. 7.13C± E). Each of the three light environments tested shifted
the relative intensities of the four phases, i.e., the proportional involvements of the two carboxylases. Griffiths et al. (1990) and Griffiths (1992)
also used on-line mass spectrometry to monitor instantaneous carbonisotope discrimination as Tillandsia utriculata performed CAM (biomass
D 517.4½ ). Recycled CO2 accounted for 72% of DH1 (diurnal change in
titratable acidity). Both PEPc and RuBPc/o operated during phase two and
four, accounting for 4.0 and 22.5% respectively of the carbon gained over
the 24-h CAM cycle.
Because phase three operates behind closed stomata during the hottest,
driest part of the day, CAM plants usually expend less H2O per unit of
biomass manufactured than is possible for C3 and C4 plants facing equivalent evaporative demand. Instantaneous transpiration ratios (H 2O/CO2)
can drop to about 10:1 (Tables 4.3, 4.4), leading to better performance than
typical for C3 ¯ ora. Transpiration rates differ as much or more, but also
with some overlap. Ekern (1965) reported that Ananas comosus lost 0.3± 0.5
mg H2O cm22 day21, whereas comparable values for corn (a C4 plant) were
26 and ruderal Xanthium (C3), 43. However, the bene® ts of gaining CO2 primarily after dark exact a cost: like many other CAM types, pineapple grew
by far the slowest of these three subjects.
The identity of the energy reserves expended to drive phase one and
accordingly, where mobilization begins, whether in the cytoplasm or plastids, distinguish at least one bromeliad from many other CAM plants.
Ananas comosus and some unrelated taxa (e.g., Aloe) exemplify the more
recently described type. About 20± 170 times the reserves consumed over
the same period by dark respiration were expended to build up the pool of
carbon needed to sustain net photosynthesis during the following photoperiod (Carnal and Black 1989). Starch accounts for much of the CO2 stored
as malic acid by most of the nonbromeliads studied, the observed reservoirs
of hexose being inadequate. Glucose and fructose fractions changed
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Carbon and water balance
Table 4.3. Gas exchange characteristics of C3 and CAM bromeliads in
Trinidad
Transpiration
(mmol H2O m22)
Net CO2 uptake
(mmol m22)
Transpiration ratio
(H2O/CO2, w/w)
C3 species through
entire photoperiod
Vriesea amazonica
Vriesea splitgerberi
Vriesea jonghei
Tillandsia fendleri
24.2
24.2
31.3
57.6
1.82
10.96
10.33
Ð
31
185
135
46
CAM species during
phase four
Aechmea lingulata
Aechmea aquilega
Aechmea nudicaulis
13.3
3.7
4.6
3.33
0.27
0.84
102
30
75
Source: After Grif® ths et al. (1986)
enough in pineapple foliage to account for DH1 assuming that pyrophosphate-dependent phosphofructokinase, not ATP-dependent phosphofructokinase, catalyzed the phosphorylation of fructose-6-phosphate. Glucan
contributed modestly to acidi® cation in A. comosus. Foliar sucrose also
diminished at night, but probably through export rather than metabolism.
Tillandsia usneoides monitored in a North Carolina forest illustrates how
one CAM bromeliad behaves under a strongly seasonal climate. Subjects
gained dry weight and consumed CO2 most vigorously from mid-spring
through mid-fall (Martin et al. 1981). Acid ¯ uctuations and net CO2 uptake
almost ceased in midwinter. Consistent with the situation in many other
CAM types, carbon gain varied with temperature, DH1 peaking in late
spring as daytime highs approximated 25± 30 °C. If night air was programmed in a growth chamber to remain at 20 °C, diurnal maxima up to
35 °C had no dampening effect on CO2 consumption; however, as the nights
grew warmer, net CO2 uptake fell, beginning with the disappearance of
phase four. If the daytime maximum reached 20 °C, phase one could be sustained to a nocturnal low of about 5 °C. Net ® xation ceased below 5 °C, or
if day/night temperatures ¯ uctuated by less than 5 °C.
Ecological correlates of the carbon fixation syndromes
Textbook treatments often imply that vascular ¯ ora segregate into clearly
de® ned CAM, C3 and C4 types. Likewise, these authors tend to assign
Cambridge Books Online © Cambridge University Press, 2009
Table 4.4. Night-time gas exchange and related phenomena in CAM and C3–CAM bromeliads in Trinidad
Species
Aechmea aquilega
Aechmea aquilega
Aechmea nudicaulis
Aechmea nudicaulis
Aechmea fendleri
Aechmea lingulata
Tillandsia elongata
Tillandsia utriculata
Bromelia plumieri
Guzmania monostachia
Total CO2 uptake
Recycled CO2
E
Annual precipitation 18.00± 06.00 hours
DH1
as % of total 18.00± 06.00 hours Transpiration ratio
at study site (mm)
(mmol m22)
(mol m23)
® xed
(mol H2O m22)
(H2O/CO2, w/w)
1281
2625
1612
2625
2637
2625
1612
2366
1281
2366
6.5
36.3
46.4
54.8
45.0
47.6
15.9
3.9
0.5
0.6
113
393
301
469
332
309
271
251
72
70
89
83
71
78
56
65
82
95
99
94
Source: After Grif® ths et al. (1986).
Books Online © Cambridge University Press, 2009
0.78
0.85
3.08
1.02
4.24
5.86
2.80
2.28
0.92
2.27
49
10
27
8
38
50
72
239
753
422
122
Carbon and water balance
speci® c kinds of plant performance and native habitats according to the
same, oversimpli® ed paradigm. Bromeliaceae challenge the second generalization except on two counts. First, relative compatibility between C3
metabolism and cool to cold growing conditions probably does explain the
near absence of CAM in Bromeliaceae (mostly Puya) above about 3000 m.
Second, C4 species appear to be absent, perhaps in part because none of the
bromeliads possess certain other characteristics (e.g., short life cycle)
usually associated with this photosynthetic syndrome.
Reasons why CAM imparts advantage to so many bromeliads in such
diverse kinds of habitats, and why one situation favors one compared with
another version (e.g., obligate vs. facultative) of this syndrome, remain
elusive. For example, many months pass without opportunity to eliminate
moisture de® cits for those species native to hyperseasonal sites, while relatives with similar D values sometimes grow where drought may be more frequent but less severe.
Leaf anatomy provides no greater insights on ecotolerance, as demonstrated by succulence that varies among CAM Tillandsia anchored on the
same trees (e.g., T. paucifolia, dry weight524.5% fresh weight vs. T. balbisiana, same value536.0% in southern Florida). Higher ® ber content in the
second species probably re¯ ects mechanical requirements obliged by exceptionally elongated blades. Hypodermal development fails to predict
drought-tolerance for commonly sympatric T. paucifolia and T. recurvata
(this tissue accounts for 38 and 3% of leaf volume respectively; Loeschen
et al. 1993). Other plant characteristics complicate the issue further.
Phytotelmata enhance the effectiveness of scarce rainfall for hundreds of
epiphytic and lithophytic bromeliads, perhaps enough sometimes to render
accompanying CAM more important for other purposes (Skillman and
Winter 1997; Skillman et al. 1999).
Environmental uncertainty may explain why CAM pervades so much of
Bromeliaceae. CAM-equipped ¯ ora remain active during moderate drought,
and, if necessary, can enter a quiescent state (CAM-idle) rather than deeper
dormancy should stress exceed some threshold. Facultative types capable of
shifting into the more productive C3 mode as circumstances allow (e.g., the
® rst rain at the end of a drought) are especially well positioned to thrive on
episodic or unpredictable supplies of moisture. Guzmania monostachia demonstrates that plant readiness to exploit ecological opportunity during
drought-enforced quiescence includes maintenance of the integrity of the
photon-harvesting apparatus as described below. Then again, CAM may not
always promote ® tness beyond that possible with an alternative photosynthetic syndrome, but instead represents a sustainable anachronism.
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123
Conditions prevailing where many CAM plants grow, and the selfshading inherent to thick stems such as those of many cacti and the typically compact shoots of many other desert succulents, have promoted a
third, erroneous impression that CAM-type ¯ ora routinely require substantially higher exposure than the C3 forms. Heliophily does accord with
the heightened supply of ATP (6.5 vs. 3.0/molecule CO2) needed to operate
via CAM compared with the PCRC pathway, but additional, undetermined
costs for biomass preclude de® nitive comparisons (e.g., Raven 1985).
Whatever the price of biomass in energy or any other potentially growthlimiting resource, many CAM bromeliads inhabit the forest understory,
and several populations native to more open habitats (e.g., Bromelia
humilis; Medina et al. 1986) exhibit greater productivity in partial than in
full sun.
Numerous studies, including some conducted in situ, indicate how
Bromeliaceae, especially the CAM types, respond to speci® c combinations
of temperature, nutrient supply, drought and exposure. Diverse methodologies and contradictory results cloud some of the interpretations, but even
so the data demonstrate that designation as a CAM type says relatively little
about other important aspects of plant biology (e.g., epiphytic vs. terrestrial habit, phytotelmata present or absent, shade-tolerant or intolerant).
Our consideration of ecophysiological diversity among the bromeliads
begins with a description of the qualities of members of Type Two, the best
known of the ® ve categories, and one of the three that contains CAM
species exclusively beyond the occasional Brocchinia (C3) that, by shoot
form, also belongs here (Table 4.2).
Ecophysiological profiles of the five types of Bromeliaceae
Type Two species
Reports on pineapple greatly outnumber those for any other bromeliad,
and information on several ecologically signi® cant phenomena (e.g., effects
of photoperiod on CAM) comes exclusively from this cultigen.
Unfortunately, domestication precludes uncritical extrapolation to wild
types because certain aspects of ecophysiology, in addition to fruit qualities, represent engineered rather than naturally selected characteristics
(e.g., Baker and Collins 1939). Manipulations initiated long ago in indigenous South American agroecosystems may account in part for tolerances
for certain growing conditions among surviving genotypes, some of which
persist untended by humans (Fig. 1.3E). However, the other half a dozen
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Carbon and water balance
or so Ananas species, closely related Pseudananas, and scattered additional
Bromelioideae (e.g., several Bromelia species, Aechmea magdalenae; P® tsch
and Smith 1988) share similar ecology, structure and physiology (Table 4.1;
Fig. 2.14A,B).
Forest understories support the occasional deeply shade-tolerant Type
Two bromeliad (e.g., Aechmea magdalenae), while the more heliophilic
forms (e.g., Neoglaziovia; Fig. 6.12A) inhabit savannas, open restingas, and
of course, for the pineapple, extensive croplands. Opinions vary about basic
propensities; some authorities considered Ananas comosus, Bromelia
humilis and the rest of their kind fundamentally heliophilic (e.g.,
Pittendrigh 1948), while other investigators (e.g., Medina et al. 1993) view
B. humilis and Bromelioideae overall as shade-tolerant through derivation
from forest-dwelling stock. Medina et al. (1991a,b, 1993) further concluded
that Type Two bromeliads, and Ananas in particular, are good subjects in
which to investigate how lineages descended from relatively light-sensitive
antecedents became better performers in full sun. Most ® eld crops,
although modi® ed architecturally (e.g., higher harvest index) and shortercycled, ® x carbon no more vigorously on a leaf area basis than their wild
progenitors. Pineapple might be an instructive exception.
Ananas comosus responded differently to light in separate experiments in
part according to the cultivated vs. `wild' status of the subject and preconditioning relative to water, PPFD and N supply. Martin' s (1994) appendix
summarizes the extensive data on the light relations and carbon and water
balance of pineapple. Studies by Nose et al. (1977, 1981) and Sale and
Neales (1980) exemplify a substantial part of that literature. Gas exchange
by well-watered specimens at PPFD ranging from 200 to 1500 mmol m22
s21 indicated that photosynthesis light-saturated at 1000± 1500 mmol m22
s21, high enough to warrant designation as heliophiles. Different pretreatments and conditions during other runs produced other values. Nose et al.
(1981) recorded only slightly increased CO2 uptake (net over 24 h) as potted
subjects responded to exposures ranging from 600 to 1200 mmol m22 s21.
Still another group of hydroponically grown plants reacted similarly to
200± 500 mmol m22 s21, but they showed no further increase even when
PPFD was doubled.
Borland and Griffiths (1989) reported that sufficient time under low or
moderate exposure (60 or 600 mmol m22 s21) produced specimens with
standard sun/shade characteristics. Low-light plants consumed CO2 less
vigorously, and showed lower light compensation intensities and higher
apparent quantum yields (Table 4.1). However, some feral subjects demonstrated more fundamentally shade-adapted photosynthetic responses.
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Ecophysiological profiles of the five types of Bromeliaceae
125
Bromelia humilis also grows across shady to fully exposed microsites in
coastal strand and inland habitats in northern Venezuela (Medina et al.
1986). Unlike some genotypes of Ananas comosus, high exposure, or
perhaps the attendant heating or drought, inhibits growth at some sites to
the extent that few seeds and only occasional ramets develop (Chapter 7).
Medina et al. (1991b) conducted one of the most ambitious analyses of
Type Two Bromeliaceae when they examined cultivated and woodland
populations of pineapple and three of its undomesticated congenerics (A.
ananassoides, A. paraguazensis, A. lucidus) in northern Venezuela. Aechmea
aquilega, Bromelia chrysantha, B. goeldiana, B. humilis and two C3 types,
Brocchinia micrantha and Pitcairnia bulbosa, were also included in the
survey. All three Ananas species and several of those escaped `varieties' of
A. comosus typically grew under taller vegetation. Foliage born by shadegrown individuals contained higher concentrations of N compared with
samples collected in the more exposed, rocky sites, supposedly owing to the
greater fertility of forest soils and the less scleri® ed nature of shade vs. sungrown foliage.
Foliar N, which routinely predicts Amax in C3 plants, also did so for H1max
among these Venezuelan bromeliads, but not CO2 consumption during
phase four when RuBPc/o assists ® xation. Sun compared with shade-grown
foliage produced by the same genotype discriminated less against deuterium (D; presumably fractionated from H2O/D2O in the transpiration
stream), indicating heightened reliance on PEPc because fuller exposures
promoted CAM (Fig. 4.3). Relatively still air and closer proximity to
decomposing C3-type litter may have in¯ uenced D values for the subjects
that grew in the understory.
Evidence that Medina et al.' s plants discriminated against D according
to the prevailing ® xation pathway and incident PPFD was mixed (Fig. 4.3).
Contrary to ® ndings elsewhere (e.g., Sternberg et al. 1984), isotopes sometimes failed to distinguish C3 from CAM types. Speci® cally, two C3 species
yielded less negative dD values than expected, while records for ® ve CAM
types deviated in the other direction. Generally, except for six paired, shade
and sun-grown samples, the former gave more positive readings.
Presumably, determinants (e.g., variable D/H ratios among the local moisture supplies) beyond the responsible carboxylases must be normalized in
more thoroughly controlled experiments. Even so, Medina et al. (1991b)
suggested that dD values provide a `very promising' tool to investigate the
acclimation of CAM bromeliads and other plants to altered PPFD.
Aechmea magdalenae, more than either Ananas comosus or Bromelia
humilis, demonstrated that deep shade constitutes a major dimension of the
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126
Carbon and water balance
Figure 4.3. Distribution of D and dD values for C3 and CAM species grown in sites
characterized by widely divergent light and humidity conditions (after Medina et
al. 1991b).
realized niche of a Type Two bromeliad (P® tsch and Smith 1988). This
extraordinarily robust terrestrial (leaves up to 3 m long) routinely dominates understory sites in humid forests from Costa Rica to Ecuador at
abundances up to one spiny shoot per m2. On Barro Colorado island, colonies occupied 25± 100 m2 patches of forest ¯ oor with enough interlocking
shoots to largely halt regeneration by local woody ¯ ora (Brokaw 1983).
Frequent fruiting and vigorous ramets characterized populations under
both closed (.3%) and more open (.35%) canopies. Plants moved into the
laboratory received 15 mmol m22 s21 (LL plants) or 300 mmol m22 s21 (HL
plants) for 6± 8 weeks prior to measurements of CO2 exchange under high
and low PPFD. Brokaw also recorded leaf production by a second set of
undisturbed plants in the same Panamanian forest.
Low-light-grown subjects responded similarly to weak and stronger
PPFD (Fig. 4.4). Amounts of CO2 (net) consumed over complete day/night
cycles differed little, and subjects treated either way relied on CAM, but not
to the same degree. Eighty to ninety vs. about 60% of the carbon gained
under high and low exposures respectively accumulated during phase one,
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Ecophysiological profiles of the five types of Bromeliaceae
127
Figure 4.4. Diurnal course of CO2 exchange by Aechmea magdalenae grown
exposed to high (~300 µmol m22 s21; HL) or low (~17 µmol m22 s21; LL) light after
being preconditioned for 6± 8 weeks under shade cloth that provided 5 or 35% sunlight (after P® tsch and Smith 1988).
with phase four accounting for the balance. Conversely, HL plants failed to
maintain positive carbon balances during the LL runs and took up somewhat more CO2, again via CAM, under the HL treatment. Forest plants
grew slowly (0.76 g m22 day21), only a small fraction of the growth recorded
for some cultivated, exceptionally vigorous CAM plants representing
Agavaceae and Cactaceae (Nobel 1991).
Aechmea magdalenae specimens growing under relatively open canopy
gained weight faster than those in deeper shade purportedly because moisture, not photosynthetically active radiation (PAR) was more abundant
there (P® tsch and Smith 1988). Thinner foliage prevailed under dense canopies as did low apparent quantum yields (0.01± 0.001). This forest-dweller
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Carbon and water balance
surely quali® es as one of the most shade-tolerant bromeliads, and could
well rank with the record-holders among CAM plants adapted to lowenergy habitats. It also demonstrated extraordinary capacity for photosynthesis at another shaded location.
Koniger et al. (1995) and Skillman et al. (1999) compared Aechmea magdalenae to diverse, co-occurring C3 herbs (e.g., species of Calathea,
Dieffenbachia, Piper), also on Barro Colorado island, to explain this
bromeliad' s impressive growth as a CAM plant in deep shade. Maximum
photosynthetic capacity (17.5 mmol O2 m22 s21) exceeded that for neighboring C3 types (2.1± 6.1 mmol O2 m22 s21), as did nitrogen-use efficiency.
Compared on the basis of dry weight and chlorophyll content rather than leaf
area, observed rates more closely approached parity owing to the 2± 4-fold
thicker foliage of the bromeliad. Calculations using measured Amax further
indicated that nitrogen-use efficiency for Aechmea magdalenae equaled 188
mmol O2 mol N s21, twice that of the co-occurring C3 ¯ ora and comparable
to values obtained on the same occasion for several of the local trees.
Observations conducted in Venezuela also demonstrated how certain
metabolites ¯ uctuated in foliage as Ananas comosus and A. ananassoides
performed CAM (Medina et al. 1993). Exposures differed enough among
sampled populations to induce conspicuous sun and shade plant characteristics. Higher leaf weight/area ratios and greater succulence (water
content/leaf area) characterized the HL subjects, as did more vigorous
phase one activity. Substantial citric in addition to malic acid accounted for
DH1 in leaf sap, although somewhat unevenly among treated populations.
Fructose consistently exceeded concentrations of the other assayed sugars,
with sucrose yielding the lowest values of all. However, this substrate alone
cycled inversely with DH1 suggesting involvement in phase one. Fructose
and glucose levels in the sun, but not shade, leaves of several A. comosus
cultivars diminished at night, while the proportions of several cations
(K1.Ca21.Mg21) changed little. All three nutrients occurred most abundantly in shade-grown specimens. Leaf sap osmolality increased signi® cantly toward dawn only among HL plants.
Type Two bromeliads have also demonstrated plant acclimation to temperature, and how this variable in¯ uences CAM. Warm days followed by
cooler nights (30/15 °C) maximized CO2 consumption by Ananas comosus,
while constant temperatures and inverted oscillations depressed uptake
(e.g., Neales et al. 1980). Bartholomew (1982) reported broad day and night
optima for phase one. Generally, CO2 consumption diminished during the
® rst and fourth phases of CAM as stress imposed by several agencies
increased (e.g., drought in addition to thermal), and decidedly unfavorable
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Ecophysiological profiles of the five types of Bromeliaceae
129
conditions caused plants to lose carbon. Gradual changes impacted carbon
budgets less, probably because they more closely parallel circumstances in
native habitats. High thermal optima characterized some lowland forms,
for example about 27 °C for Aechmea nudicaulis (Type Three) in Trinidad
(Smith et al. 1986). Broader surveys of CAM Bromeliaceae would likely
con® rm that the most propitious temperatures for carbon gain vary as
much as those prevailing in situ.
Pineapple indicated that photoperiod affects CAM in at least one bromeliad. Subjects maintained in growth chambers at constant PPFD under
different day lengths (daily photon dosages varied) exhibited similar DH1,
perhaps because every treatment provided enough irradiance to maintain
the carbohydrate reserves needed for robust acidi® cation (Friend and
Lydon 1979). However, foliar H1 rose more slowly as day lengths diminished. Short photoperiods strengthened phase one in another set of runs,
although plants grown under longer days consumed more CO2 during
phase four (Nose et al. 1986).
Nitrogen supply also in¯ uences carbon gain according to observations
on several Type Two species. Nose et al. (1985) demonstrated that foliar N,
which they manipulated in A. comosus by altering the composition of
hydroponic media, correlated with nocturnal CO2 uptake. Nitrogen starvation caused plants grown under high light to increase the proportion of
DH1 dependent on recycled CO2 relative to supply from the atmosphere
(Borland and Griffiths 1989). Low N status also promoted citric in proportion to malic acid synthesis during phase one. Fetene et al. (1990) noted
similar responses for Bromelia humilis, and interpreted these results relative
to the conditions many Type Two bromeliads experience in situ, as discussed below (Figs. 4.5, 4.6).
Still undetermined are the relative contributions of plasticity and genotype to the exceptionally broad ecotolerances of certain Type Two bromeliads. Two Ananas comosus cultivars demonstrated different capacities to
adjust across a range of PPFD that may accord with distinct origins in
Venezuela (Medina et al. 1991a). Variety Brecheche was probably selected
by farmers indigenous to the Orinoco river basin for cultivation in full sun
to partial shade in palm swamps, while Spanish Red, the second genotype,
provides most of the commercially produced pineapple in that country
today. Subjects grown in phytotrons under low and higher light (25± 50 or
325± 400 mmol m22 s21) with ample irrigation and fertilizer developed
different ecophysiological pro® les, including responses to shade. Brecheche
acclimated to high and low light more successfully than Spanish Red
according to DH1, gas exchange and shifts in leaf chemistry. By the end of
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Carbon and water balance
Figure 4.5. In¯ uence of growth PPFD and nitrogen supply on the nitrogen-use
efficiency of Bromelia humilis (after Fetene et al. 1990).
the six-week pretreatments, chlorophyll and N contents in LL plants were
2.8 and 1.4 times those of the better-exposed specimens.
Type One species
Type One Bromeliaceae remain less studied than species representing the
other four types in part because they lack commercial value and the novelty
of the phytotelm and wholly trichome-dependent species. Even so, enough
is known about these plants to report that mechanisms of carbon and water
balance vary with the substrate, exposure and climate as with Type Two
species (Martin 1994). Certain genera exhibit CAM (e.g., Hechtia, Dyckia,
Encholirium) and others C3-type photosynthesis (e.g., Fosterella,
Pitcairnia). Views vary on Puya, one of the largest and most ecologically
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Ecophysiological profiles of the five types of Bromeliaceae
131
Figure 4.6. Light response curves of integrated net CO2 uptake for the dark period
by Bromelia humilis expressed per unit of leaf area (after Fetene et al. 1990).
diverse of the genera comprising this category (Fig. 14.2C). Medina (1990)
assigned the entire taxon C3 status, despite his own contradictory determinations (D5,15± 25½ ; Table 4.1) for several species.
Puya copiapina yielded a particularly convincing 15.4½ (Medina et al.
1977). On the other hand, natives of the coldest habitats would deviate
from the norm for alpine ¯ ora if equipped for other than C3 photosynthesis. Frost probably exceeds aridity as the primary challenge to these high
Andean bromeliads, much as nightly freezes account for the novel physiology and morphology of the giant rosette-forming herbs in other families
(Figs. 7.2± 7.4). Facultative CAM probably characterizes a substantial
number of Puya species from warmer (lower) sites, and P. floccosa
(D522.5½ ) reportedly CAM-cycles (Medina et al. 1977; Smith et al. 1986).
Even fewer reports address instantaneous performances. Lüttge et al.
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Carbon and water balance
(1986a) measured gas exchange by Pitcairnia integrifolia, a pseudolithophyte (Chapter 7) in Trinidad. Carbon gain commenced at dawn, intensi® ed, and then diminished during midday coincident with leaf
temperatures that occasionally approached 52 °C. Poor WUE indicated
extensive root systems and an abundant moisture supply. Greenhousegrown subjects light-saturated between 200 and 400 mmol m22 s21 and
10± 15 mmol m22 s21 balanced respiration. Quantum yields between 0.02
and 0.03 con® rmed shade-tolerance.
Broad shields (Fig. 2.8D) born by the foliar trichomes characteristic of
Type One Pitcairnioideae native to relatively dry habitats supposedly
reduce transpiration and vulnerability to photoinhibition (Lüttge et al.
1986a). Glabrous, adaxial leaf surfaces produced by architecturally similar
P. bifrons re¯ ected just 20% of incident PAR (70° angle to the blade
surface), while the densely invested abaxial side scattered 39.4% of the same
beam. Restriction of the indumentum and stomata to the abaxial epidermis here and among many relatives suggests greater importance for water
conservation than for photoprotection. Such arrangements might provide
a third service by repelling pathogens that could otherwise attack susceptible foliage through stomata.
The occasional Pitcairnia species, Ayensua and probably some members
of Brocchinia shed their green foliage (but not the spiny, reduced achlorophyllous organs in the case of Pitcairnia heterophylla; Fig. 2.12A) to conserve moisture during the driest months of the year. Leaves of some
Fosterella species, like many other drought-avoiding monocots (e.g.,
grasses), lack the same discrete abscission mechanisms, instead gradually
withering beginning at the tip. As for many other deciduous plants, the
behavior of cultivated, well-watered specimens points to photoperiod as
the primary cue for senescence (Chapter 6).
Type Three species
Types Three and Four Bromeliaceae exaggerate the relatively modest utriculate morphology of the leaves of the Type Two species (Fig. 2.4; Table 4.2).
Accordingly, the more capacious leaf axils impound enough moisture and
debris to permit abandonment of the substratum for all but physical
support. Apogeotropic roots (Fig. 2.14D) occasionally penetrate the phytotelmata, but water and nutrients mostly enter the shoot through foliage.
Juveniles remain too small for months to several years to accumulate adequate soil substitutes in leaf axils. Seedlings of Type Three Bromeliaceae
(Figs. 3.8A, 6.5A,F) presumably rely on roots to obtain moisture and nutri-
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Ecophysiological profiles of the five types of Bromeliaceae
133
ents. Consequently, occurrences on fundamentally hostile media like bark
and rock probably require the presence of mitigating nonvascular ¯ ora that
adult morphology (phytotelma) renders unnecessary (Fig. 6.5A,F).
Type Four Bromeliaceae, although likewise dependent on phytotelmata
later in life, spend the ® rst weeks to months of life root-free, suggesting
greater dependence on foliar trichomes and diminished opportunity for
substrates to in¯ uence where seeds can succeed (Figs. 3.8C, 6.5G). Surveys
in situ and a closer look at trichome function through the plant life cycle
would probably con® rm what seems almost certain to be one of the important distinctions between Type Three and Type Four Bromeliaceae. Certain
embellishments of the bromeliad shoot provide the phytotelm species
several options for nutrition by favoring speci® c kinds of events in phytotelmata (Chapters 5 and 7, and below). Carnivory appears to be limited to
Tillandsioideae (Catopsis) and Brocchinia. Little is known about how any
of the impounding bromeliads affects events in its phytotelmata.
Laessle (1961; Fig. 8.12) noted diurnal rhythms in pH in the solutions
impounded by diverse Jamaican bromeliads that Benzing et al. (1972) con® rmed in the laboratory with Aechmea bracteata (Fig. 8.14). Dissolved CO2
accounted for some of the change, but boiling failed to neutralize all of the
acidity that developed during the night (McWilliams 1974). Solutes, including organic acids synthesized during phase one, may leak into phytotelmata
fast enough to account for the observed acidi® cation. Whether reabsorption from the same unstirred solutions explains the morning rebound is less
likely. Presumably, moisture impounded in a bromeliad shoot represents
the ® rst in a series of coupled compartments that constitutes a hydraulic
continuum, much as soil water is in¯ uenced by the free energy status of the
moisture in the adjacent plant. Opportunities to exchange solutes across
the same boundaries must be subject to more stringent plant control.
Type Four species
Tillandsioideae that comprise Type Four mostly possess relatively thin,
sparsely trichomed C3-type foliage (Figs. 1.2G, 2.8B; Table 4.2); leaf axils
trap substantial amounts of moisture and litter except for the carnivores
(Figs. 2.4F, 7.16). The single bromeliad (Guzmania monostachia) with welldocumented facultative CAM also belongs here, suggesting the possibility
of additional examples of this and other mixed syndromes as considered
below. Light relations probably vary about as much among the Type Four
bromeliads as across the entire family. Exceptional members, like Catopsis
berteroniana (Fig. 5.3B) and Brocchinia reducta (Fig. 2.4F), require high
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Carbon and water balance
exposure to satisfy the inherently high energetic costs of prey-dependence
(Givnish et al. 1984). Reliance on ¯ ying, light-seeking rather than nonvolant fauna (primarily ants), as does B. reducta, further restricts fruiting
specimens of Catopsis berteroniana to the uppermost perches in supporting canopies.
Vertical foliage covered by an extraordinarily re¯ ective cuticle helps
protect the three carnivores and certain other Type Four species from
potentially injurious irradiance in what are typically well-exposed microsites (Fig. 5.3A). Residence deeper in the canopy, where many other Type
Four species occur, mandates more horizontally oriented foliage, that by
promoting litter capture may diminish shade-tolerance (Figs. 2.4H, 7.16).
Low PPFD limited carbon gain by noncarnivorous, forest-dwelling
Tillandsia fendleri and Vriesea jonghei monitored in northern Trinidad
(Griffiths et al. 1986). Additional features of foliage, particularly the layering of leaves and their pigmentation (Figs. 2.14G, 2.17B, 2.18B), distinguish other phytotelm Tillandsioideae within Type Four, and in some cases
probably promote performance in dim light as Lee et al. (1979) proposed
for some other tropical herbs.
Quite likely, Type Four bromeliads with lax, sometimes discolorous,
monolayered foliage (Fig. 2.4H) rank among the most shade-tolerant
members of the family. Leaves of Guzmania lingulata photosaturated below
300 mmol m22 s21, and exhibited compensation intensities less than onetenth as strong whether preconditioned for nine months with high or low
(45 vs. 400± 700 mmol m22 s21) exposures (Smith 1989; Fig. 4.7). Smith also
noted acclimation, speci® cally that chlorophyll concentration and vulnerability to photoinhibition increased and dark respiration slowed when specimens were transferred from high to low light. Conversely, Amax remained
essentially unchanged. Other Type Four species that Pittendrigh (1948)
considered shade and exposure-tolerant included Tillandsia monadelpha, T.
anceps and Vriesea simplex. Excised foliage of all three species exhibited
light responses (low compensation and light saturation intensities) consistent with shade-tolerance (Benzing and Renfrow 1971b). Catopsis nutans
and Tillandsia complanata also possess demonstrably malleable light-harvesting systems (see Martin 1994 for summarized data).
Type Four bromeliads that bear densely congested canopies featuring
unusually thin, uniformly green foliage instead of the bicolored, more
robust and monolayered displays of Catopsis nutans and Guzmania lingulata also tolerate heavy shade. And as Pittendrigh surmised (Fig. 7.11),
these plants would probably occur more widely if better equipped to
counter drought. Grown fully exposed in wet sites, particularly at high alti-
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Ecophysiological profiles of the five types of Bromeliaceae
135
Figure 4.7. Response of net photosynthesis (CO2 uptake) to PPFD by Guzmania lingulata pretreated for nine months in low (average 45 µmol m22 s21) or high (average
250 µmol m22 s21) environments (after Smith 1989).
tudes, abundant sun-screening anthocyanins accumulate in the adaxial epidermis. Tillandsia complanata, for example, appears almost chlorophyllfree under such conditions, the light-harvesting pigments masked by a
suffuse, brownish-red screen. Substantial shade induces this same wideranging epiphyte to develop deep bluish-green foliage in part owing to more
concentrated chlorophylls. It, like many other, routinely more ornamented
Tillandsioideae (e.g., Vriesea irazuensis) brought under glass or into shade,
or if simply moved from high to lower elevations, develops unremarkable
green foliage within weeks. On the other hand, some taxa, or just certain
populations within a species, remain brightly colored in sun and shade (e.g.,
Tillandsia biflora).
The apparent incapacity of Catopsis to synthesize anthocyanins may
present no serious problems because other compounds serve as well for at
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Carbon and water balance
least two of the same purposes. Fruits are dry so frugivores need not be
attracted, and all of its ,20, probably entomophilous species produce
white, green or yellow ¯ owers and associated bracts. The most heliophilic
member of the genus, Catopsis berteroniana, features that dense, powdery
re¯ ective epicuticle (Fig. 5.3A) over the yellowish foliage just mentioned, as
do some related taxa (e.g., C. morreniana). Similar coatings mark the large,
distichous bracts of still other Tillandsioideae (e.g., Tillandsia heterophylla), probably to attract nocturnal pollinators. Catopsis species usually
con® ned to deep shade (e.g., C. floribunda, C. nitida) lack these conspicuous wax deposits and maintain deep green foliage.
Guzmania monostachia, the widest-ranging member of its sizable genus,
exhibits exceptional ecological versatility, including tolerance for high to
low exposures, assisted in part by facultative CAM (Medina et al. 1977;
Maxwell et al. 1992, 1994, 1995). Unstressed, it takes up CO2 mostly by day;
while droughted or overexposed, even if well watered, a typical CAM
pattern strengthens as described in greater detail below (Fig. 4.8; Table 4.6).
Scores for biomass ranged from D5223.7 to 231.5½ . Specimens at the C3
end of the spectrum experienced relatively equable growing conditions,
while those with less negative values occupied seasonally drier or relatively
exposed sites at wetter locations. Guzmania monostachia may differ regionally on some or all of these counts. Florida' s small population routinely
occupies shady habitats, whereas others farther south often experience less
diminished sunlight. Structurally comparable Tillandsioideae with somewhat less extensive geographic, but greater altitudinal, ranges (e.g., G. sanguinea) may owe their success to similarly ¯ exible ecophysiology.
Some Type Four Bromeliaceae probably CAM-cycle. McWilliams (1970)
reported suggestive metabolic rhythms for Vriesea fenestralis, and Medina
(1974) identi® ed malic acid as the leaf constituent responsible for these ¯ uctuations in Catopsis nutans, Guzmania mucronata, Tillandsia adpressiflora
and Vriesea platynema. Cyclers in other families (e.g., Pereskia of
Cactaceae) also lack pronounced xeromorphy, instead achieving water
economy as mentioned above by re® xing dark-respired CO2 that would
require the expenditure of additional moisture to replace from the atmosphere (Harris and Martin 1991; Martin 1994).
Heterochrony appears to explain much of the novel architecture and specialized foliar epidermis of the Type Five bromeliad. If so, evolution began
with a more mesic stock and progressed through a series of increasingly
abbreviated, xeromorphic and generally miniaturized stages represented
today by an array of surviving lineages (Fig. 2.1). Tillandsia subgenus
Diaphoranthema culminates this sequence with the most diminutive of
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Ecophysiological profiles of the five types of Bromeliaceae
137
Figure 4.8. Dawn/dusk titratable acidity (DH1) for Guzmania monostachia exposed
for 14 days to high light under water-stressed and well-watered conditions (after
Maxwell et al. 1994).
these putative descendants. Phytotelm Tillandsioideae, as exempli® ed by
Tillandsia deppeana and Vriesea geniculata, may resemble evolutionary
antecedents according to a long-standing hypothesis (Schulz 1930) and
some recent ® ndings on structure and function.
Tillandsia deppeana and Vriesea geniculata inhabit relatively humid
forests where as adults they maintain substantial, water-tight leaf axil
chambers that permit roots to be primarily mechanical (Fig. 4.9). Because
the root system lacks appreciable absorption capacity, the shoot must be at
least one-quarter full size (i.e., possess foliar impoundments) before opportunities to hydrate and absorb nutrients exceed those brief intervals while
leaves remain wet from precipitation. Epidermal structure, in addition to
leaf and shoot morphology, changes with plant age, as do related aspects
Cambridge Books Online © Cambridge University Press, 2009
Table 4.5. Summary of leaf H2O relations of the bromeliads investigated at six study sites during the dry season in Trinidad.
n 5 number of species examined at each site. Number in parentheses indicates mean annual rainfall (in mm) determined from
records for 2–6 years
Minimum p leaf (MPa)
Minimum xylem tension (MPa)
Maximum xylem tension (MPa)
Point Gourde
(1281) n53
Tucker Valley
(1612) n55
Areva
(2625) n58
Simla
(2566) n55
Lalaja
(not given)
Textel
(2637) n55
0.98
0.67
0.82
0.66
0.61
0.92
0.59
0.31
0.56
0.58
0.29
0.58
0.57
0.29
0.46
0.51
0.30
0.47
Source: After Smith et al. (1986).
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Ecophysiological profiles of the five types of Bromeliaceae
139
Figure 4.9. Diurnal patterns of CO2 exchange by juvenile and adult Tillandsia deppeana denied irrigation. Irradiance 650± 900 µmol m22 s21, 25/18 °C day/night leaf
temperature, 50± 60/70% relative humidity day/night (after Adams and Martin
1986a).
of water relations. Trichomes born by Vriesea geniculata during its ® rst
several years of life cover about 80% of the leaf surface, but later that value
falls below 5% (Reinert and Meirelles 1993; Table 4.7).
Shield morphology, speci® cally its width, accounts for part of the
difference in cover value as greater numbers of cell divisions produce the
Cambridge Books Online © Cambridge University Press, 2009
Table 4.6. Morphological and physiological characteristics of the central portion of the leaf blade of Guzmania
monostachia under three light regimes in situ
Microhabitat
Thickness
(mm)
Chlorophyll
Succulence Chlorenchyma Air space
(mg g21
DH1
DH1
(kg m22)
(%)
(%)
fresh weight) (high PAR) (low PAR)
Exposed
0.46(60.02) 0.33(6 0.02)
Semiexposed 0.46(6 0.02) 0.32(6 0.03)
Shaded
0.34(60.01) 0.21(6 0.04)
25
44
62
8
7
14
228
597
1021
65(6 2.4)
60(6 4.6)
15(6 2.5)
Source: After Maxwell et al. (1992).
Cambridge Books Online © Cambridge University Press, 2009
Xylem tension (MPa)
Dawn
Dusk
48(6 5.7) 0.73(60.01) 0.61( 6 0.03)
40(6 4.5) 0.69(60.04) 0.58(6 0.02)
Ð
0.50(60.01) 0.45(6 0.02)
Ecophysiological profiles of the five types of Bromeliaceae
141
juvenile (418116132164) compared with the adult (418132) pattern
(Fig. 2.9). Stomatal densities also rise and chlorophyll concentrations
increase on a fresh weight basis to further distinguish adult from juvenile
foliage much as these two features and trichome density differentiate
mature Type Four and Type Five bromeliads (Benzing and Renfrow 1971b;
Martin 1994). Finally, juveniles appear (no numbers yet) to produce relatively succulent foliage, a life-long feature for the Type Five but not the
Type Four bromeliad.
Despite the relatively xerophytic qualities of the seedling compared with
its water-impounding adult, drought probably exacts a high toll on Type
Four Bromeliaceae until shoot architecture moderates the threat of serious
desiccation. A missing element in this scenario is CAM, which might
reduce mortality, especially of juveniles, were its capacity to conserve tissue
moisture experienced early in the life cycle. However, D values recorded for
Vriesea geniculata seedlings ranged between 26.7 and 27.2½ and for adults
between 24.2 and 26.0½ (Reinert and Meirelles 1993), while Tillandsia deppeana exhibited C3-type gas exchange through the entire life cycle (Adams
and Martin 1986a,b; Fig. 4.9). Perhaps C3 photosynthesis rather than
CAM remains the better strategy because what are often accompanying
higher rates of carbon gain shorten the initial, relatively drought-sensitive
life stage.
Several additional indicators, none directly related to photosynthetic
pathway but all signi® cant for survival, revealed an even more important
distinction between the early juvenile and older Tillandsia deppeana specimen. Young and more mature subjects alike achieved quite respectable
water economies; in fact performances equaled those of some C4 and CAM
plants (Fig. 4.10). Gas exchange also demonstrated why growth accelerated. Maximum values for g, E and Amax all increased up to a full order of
magnitude on a fresh weight basis as adult replaced juvenile morphology.
Such size-related differences in Amax may be characteristic for many other
plants, and the phenomenon may be especially accessible to study using epiphytes (Zotz 1997b), although not necessarily heterochronic, Type Four
Bromeliaceae.
Responses to imposed drought followed by irrigation also supported
neoteny as the explanation for the evolution of Type Five Bromeliaceae.
Net photosynthesis by initially well-watered juveniles of Tillandsia deppeana maintained in a growth chamber dropped 60% after just one day
(Fig. 4.9). Additional days of drying brought further, smaller diminutions,
but some carbon gain continued through the run. Adults treated identically
responded more dramatically, almost ceasing net uptake by the end of the
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142
Carbon and water balance
Figure 4.10. Water-use efficiencies of adult and juvenile Tillandsia deppeana at constant leaf temperatures and relative humidity of 55% (after Adams and Martin
1986a).
® rst photoperiod. Carbon balance became negative sooner, by about noon
each day thereafter during the imposed, nine-day drought.
Additional mature plants, also drained of their tank contents, moderately desiccated, and then re® lled, failed to resume pretreatment rates of
photosynthesis for about a day. Similarly treated juveniles completely
recovered shortly after leaves were moistened ± a capacity attributed to the
denser cover of absorbing trichomes present. So it seems that adult T. deppeana emphasizes carbon gain, expending much water in the process; juveniles operate with greater economy, the trade-off being slower growth
(Adams and Martin 1986a).
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Ecophysiological profiles of the five types of Bromeliaceae
143
Type Five species
Of the several hundred Tillandsioideae that satisify Type Five criteria,
Tillandsia usneoides provides the fullest opportunity to pro® le a representative species. However, responses to similar treatments have varied and
probably for several reasons, including the age of the truss, its composition
(number of components, live and dead shoots) and preconditioning. Kluge
et al. (1973) demonstrated increasing CO2 consumption as exposure rose
from 200 to 1000 mmol m22 s21, but pretreatment at 200 mmol m22 s21 had
lasted just six days. Sections of shoots that had previously grown for eight
weeks at 30, 300 or 800 mmol m22 s21 photosaturated at about 500 mmol
m22 s21 according to O2 exchange (Martin et al. 1989).
Another set of plants taken from trees immediately prior to runs under
7± 15% full sunlight (100± 200 mmol m22 s21 PAR at midday) differed less
than expected from fully exposed (1500± 1600 mmol m22 s21) controls in
those features that usually reveal sun or shade-adaptation (Martin et al.
1985, 1989). Low-light plants contained more concentrated chlorophyll,
while chlorophyll a/b ratios remained unaffected. High irradiance
enhanced starch deposition, but had no other visible effects on chloroplast
structure. Finally, internode length, leaf size, stomatal density, and trichome and guard cell morphology were indifferent to PPFD. Maximum
acidity measured about 60% of that recorded for fully irradiated greenhouse subjects.
Spanish moss collected from the darkest of three exposures (55, 80, 1000
mmol m22 s21) in a South Carolina forest achieved higher DH1 than specimens maintained under glass (Martin et al. 1986). Performance did not,
however, deviate substantially from that of the more exposed subjects at the
other two ® eld sites. Stomata were somewhat more numerous and trichome
shields only slightly smaller compared with the plants grown in fuller sun.
Chlorophyll data paralleled those recorded for the specimens maintained
under glass. Additional runs yielded light saturation values between about
125 and 400 mmol m22 s21 using several methods to determine carbon gain.
Apparently, T. usneoides in nature and cultivation acclimates across a broad
range of PPFD without substantial morphological or metabolic adjustment, and a full day of only about 10 mol m22 can saturate photosynthetic
capacity. Evidence that high exposures photoinhibited still other batches of
Spanish moss further underscored its shade-adapted character (Martin et
al. 1986, 1989).
Desiccation typically depresses carbon gain, but Tillandsia usneoides has
sometimes exhibited the opposite response to drying and another, more
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Carbon and water balance
Figure 4.11. Effect of wetting on CO2 exchange by Tillandsia usneoides. Plants were
removed from the chamber, brie¯ y dipped in water and returned to the chamber
(after Martin and Siedow 1981).
consistent reaction to excess moisture. According to Kluge et al. (1973) and
Martin and Siedow (1981), partial dehydration stimulated uptake, but the
same condition slowed CO2 consumption on another occasion (Martin and
Schmitt 1989). Conversely, wetted leaf surfaces always depressed gas
exchange, almost eliminating it for a variety of Type Five species (Fig.
4.11). A con¯ uent layer of water-saturated trichome shields apparently
slowed the diffusion of gases through the underlying stomata while the
foliage was wet (Benzing et al. 1978; Martin et al. 1981; Martin and Siedow
1981; Fig. 2.8C,E). Treated identically, only the leaves of the sparsely trichomed, phytotelm types and myrmecophytic Tillandsia bulbosa behaved
as if still surface-dry (Table 4.8; Fig. 2.8B).
Tillandsia usneoides does not represent its type particularly well, but then
neither do any of the 250± 300 other species characterized by the same combination of absorptive trichomes, largely holdfast roots, succulence and
CAM. Nor do these most specialized of the bromeliads occupy similar habitats or exhibit the same water and light relations. Some representatives
retain moisture more tenaciously or rehydrate more rapidly than others.
Spanish moss, for example, had lost more than half of the moisture held in
initially well-watered shoots after just 1± 2 weeks of drought (e.g., Penfound
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Xeromorphy and water relations
Table 4.7. Characteristics of the leaves of heterophyllic Vriesea geniculata
as a juvenile and an adult
Trichome density
on midblade
% covered by
(mm22)
trichome shields
Chlorophyll
concentration
Density of
(mg mg22
stomata (mm22) dry weight)
Juvenile
Abaxial
Adaxial
18.366.8
13.363.4
66
87
19.8 67.7
0
263.8
Adult
Abaxial
Adaxial
6.864.3
2.961.6
2
0
26.86 5.2
0
423.4
Source: After Reinert and Meirelles (1993).
and Deiler 1947; Biebl 1964; Martin and Siedow 1981; Fig. 4.12), in part
owing to unfavorable architecture.
Quite a few relatives (e.g., T. filifolia, T. gardneri, T. tectorum) possess
surface to volume ratios no better suited for dry climates. Some of these
same tillandsioids also feature a surprisingly thin epidermis and cuticle (see
Tomlinson 1969; Fig. 2.10A± H). Conversely, Tillandsia concolor, T. karwinskyana and T. circinnatoides, among others, resist desiccation more
effectively, aided in part by compact habits and stouter epidermal barriers
bearing layers of scales with appressed rather than elevated shields (Fig.
2.10K; Table 4.10). Differences in shoots and leaves, especially the indumentum, among Type Five species may relate more to the nature and timing
of the moisture supply (dew, cloud droplets or rainfall) and the need to dissipate potentially damaging radiation than to requirements for high WUE.
Xeromorphy and water relations
Bromeliads counter drought in two ways, neither of which brings to bear
the powerful xylem tensions that the so-called euxerophytes generate to
maintain adequate supplies of moisture during prolonged dry weather.
Survival depends on either high hydraulic capacitance ± enough to qualify
as succulents, combined with extraordinary WUE or drought-avoidance in
the sense that shoots jettison relatively vulnerable (permeable) foliage
before scarcity imposes intolerable moisture de® cits (e.g., Pitcairnia heterophylla; Fig. 2.12A). Leaf characteristics, viz. capacitance and the anatomy
responsible for water storage, insure that species comprising the ® rst group
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146
Carbon and water balance
Figure 4.12. Water content of clumps of Tillandsia usneoides over the course of
three days while sheltered from precipitation (after Penfound and Deiler 1947).
experience, at most, modestly depressed Cleaf (bulk leaf water potential)
even while substantially desiccated. These bromeliads differ little from the
typical mesophyte in the range of Cleaf experienced even during the driest
weather, i.e., when relative water contents (RWC) are most depressed.
Well-watered ¯ ora typically sequester enough moisture to continue A
(and accompanying E as well) for some interval after opportunity for
replenishment ceases (e.g., supporting soil reaches critical wilting point). A
few additional hours of operation at Emax causes the stomata to close and
g to approach zero. Viability may continue, but growth ceases until tissues
recharge. Succulents greatly extend the time available for carbon gain under
the same conditions through more sparing use, usually aided by CAM, of
larger stores (greater capacitance) of water per unit of transpiration
surface. Capacitance probably varies many fold among Bromeliaceae as
does Emax, and these two properties relate inversely. Zotz and Andrade
(1997) report that measured relative capacitance (DRWC/DC) was about
0.70 MPa for Tillandsia fasciculata and 0.30 MPa for Guzmania monosta-
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Xeromorphy and water relations
147
chia. Values for epiphytes in general (ferns low end, cacti high end) range
from about 0.15 to 0.70 MPa (Andrade and Nobel 1997).
As de® cits mount within the succulent plant, moisture sequestered in its
often voluminous, collapsible water-storage tissue or hydrenchyma moves
to adjacent, more vulnerable chlorenchyma, a transfer requiring only
modest (,1.0 MPa) C gradients across short distances, whether in stems
or leaves (Figs. 2.10, 2.13, 2.16). Basically, succulence tends to decouple E
(hence A) from the environmental supply of moisture, imparting major
advantage where many bromeliads grow. Compared with many other drygrowing plants, bromeliads possess limited capacity to access soil water, i.e.,
powerful xylem tensions would serve no useful purpose for the epiphytes
and saxicoles, or for the terrestrials, many of which possess weakly absorptive or poorly developed root systems.
Foliage provides most of the capacitance for the large majority of
drought-enduring Bromeliaceae. Stems contribute modestly to shoot
volume and water supply except for certain species of Puya that, unlike the
rest of the dry-growing bromeliads, experience drought and relief on a daily
basis. As alpine endemics, these plants co-occur and look more like some
Espeletia (Asteraceae) and the other cool-growing, giant rosette-forming
herbs than the balance of Bromeliaceae, including lower-elevation Puya
(Fig. 14.2C). Taxonomic affinities aside, the group shares convergent architecture and probably much ecophysiology.
Unlike most high-altitude ¯ ora, which diminish in physical stature where
ranges exceed the tree line, species of Espeletia, Puya and to a lesser degree
Lupinus (Fabaceae) become more massive-bodied (Fig. 14.2C). Compact
shoots and in¯ orescences and dense indumenta clearly distinguish those
populations adapted for the coldest Andean ranges, in part to promote heat
retention as described in Chapter 7 (Figs. 7.2± 7.4). Frigid nights also exacerbate water balance by freezing soil moisture and reducing root conductivity ± in effect by promoting physiological drought.
Goldstein et al. (1984) compared seven Venezuelan Espeletia species
graded by size and distribution between 3100 and 4200 m. Natives of the
coldest and driest habitats produced the tallest, thickest stems containing
the largest volumes of water-® lled parenchyma. Usually wetter, lower sites
harbored the test subjects with less stem capacitance per unit surface of
supplied foliage. Basically, reserves available to the coldest-growing forms
are sufficiently large and adequately coupled hydraulically to leaves to
permit undiminished transpiration for up to 2.5 h, enough time for the
morning sun to thaw soils frozen the previous night and warm chilled
root systems. Consequently, photosynthesis can occur through the entire
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Carbon and water balance
Figure 4.13. Diurnal ¯ uctuations in malate content (DH1) and nocturnal consumption of CO2 for six species of Tillandsia relative to percent of mesophyll occupied
by hydrenchyma (succulence) expressed on a dry weight (DW) basis (after Loeschen
et al. 1993).
photoperiod. Additionally, Cleaf ¯ uctuated least, turgor loss points were
lowest, and hydraulic resistance to ¯ ow from soil to foliage was highest in
the tallest species, further underscoring the importance of stored water to
mitigate short-cycled drought. Similar water relations probably explain the
caulescent habit in Puya, its densely packed foliage, thick indumenta, and
restriction of the most massive species to paramo and puna rather than
more permissive, lower-elevation habitats.
The adaxial hypodermis, which sometimes occupies more than half of
the leaf interior (e.g., 53% in Tillandsia variabilis; Figs. 2.13B, 4.13), sequesters much of the water that sustains most dry-growing Bromeliaceae during
droughts. A second, shallower layer of similarly colorless, thin-walled
tissue lies between the chlorenchyma and abaxial epidermis, even in some
of the relatively mesic forms, for example Catopsis floribunda, Vriesea
incurvata and many Pitcairnia species (Fig. 2.16B,C). Observations indicate
that moisture in this compartment is more labile than that residing in green
mesophyll. Sideris and Krauss (1955) reported accordion-like shrinkage of
the pleated-walled hypodermis of droughted Ananas comosus, while the
dimensions of the adjacent chlorenchyma changed little (Fig. 2.13B).
Presumably, the low bulk elastic moduli (i.e., high wall elasticity) and
turgor-maintenance responsible for similar behavior in Peperomia magnoliaefolia (Schmidt and Kaiser 1987) and Agave deserti (Schulte and Nobel
1989) also prevail in Bromeliaceae.
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Xeromorphy and water relations
149
Stiles and Martin (1996) reported a leaf bulk elastic modulus of 3.3 MPa
for Tillandsia utriculata. Values calculated from pressure/volume curves
indicated capacity for osmotic adjustment (0.13 MPa from full hydration
to the point of turgor loss), and corresponding opportunity to maintain
turgor during drought. Stiles and Martin cited these attributes to help
explain why tested specimens could continue to gain carbon after 31 days
without irrigation. Griffiths et al. (1986) and Lüttge (1987), among others,
have also reported osmotic adjustment in desiccating Tillandsia shoots,
although they made no attempts to determine the bulk elastic moduli of
stressed foliage.
Leaf succulence occurs in all three subfamilies and supports species that
root on diverse substrates and experience many kinds of climates.
Substantial capacitance also characterizes much of the memberships of
Types One, Two and Five. Principal sources of moisture for these bromeliads include the contents of modest phytotelmata, soil, rainfall, dew or mist
exclusively or two or more together. Plant demands (Emax) also differ
(Tables 4.3, 4.4). Less is known about the effects of dehydration on viability. Severely droughted Tillandsia ionantha (Benzing and Dahle 1971) and
some relatives had lost more than half of their initial stores (e.g., .64% for
T. recurvata and T. usneoides; Biebl 1964), yet shoots fully rehydrated and
regained full photosynthetic capacity soon after irrigation. Remarkably,
Cleaf never fell below 21.0 MPa (see also Table 4.5). Guzmania monostachia
survived losses in excess of 90%, the record for documented desiccation-tolerance (Zotz and Andrade 1997).
Poorly understood mechanisms beyond closed stomata that deny
access to exogenous CO2 cause photosynthesis to decrease as Cleaf falls
below certain values. Taylor and Martin (in Martin 1994) used ethylene
glycol solutions to demonstrate reduced O2 evolution and undiminished
respiration in sectioned shoots of Tillandsia usneoides as Cmedium was
lowered to 24.0 MPa. Although interesting, their ® ndings offer little
insight on in vivo performance. Values for Tillandsia utriculata specimens
that were so severely desiccated in growth chambers that no CO2 exchange
could be detected still averaged about 21.5 MPa (Stiles and Martin 1996).
These numbers also represent the lowest readings reported for a bromeliad.
A robust foliar epidermis accompanies CAM in Bromeliaceae except for
those exceptional `hygromorphic' Tillandsia species (Fig. 2.17). Stout cuticles and thick, inner tangential and radial walls stand out most prominently, the latter often reducing the lumina to a few percent of the total cell
volume (Figs. 2.5J, 2.6A, 4.23I). Ananas comosus possesses such gas-tight
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150
Carbon and water balance
Figure 4.14. Light re¯ ectance off adaxial leaf surfaces of Catopsis nutans and
Tillandsia fasciculata, the second species while wet and dry. Responses for Catopsis
nutans were undifferentiated while dry surfaces of Tillandsia fasciculata re¯ ected
more light (after Benzing and Renfrow 1971b).
foliage that illuminated shoots released O2-enriched (78%) bubbles into
hydroponic media through the ends of severed roots (Ekern 1965).
Thirteen species representing all three subfamilies and all the ecological
types revealed how excised leaf blades with sealed edges resisted desiccation over CaCl2 (Benzing and Burt 1970; Table 4.10). Two of the most
decidedly mesomorphic Tillandsioideae examined, Guzmania lingulata and
Tillandsia multicaulis (Type Four), proved most vulnerable to drying, losing
more than 20% of their initial weights during the ® rst 24 h. Conversely, subjects intermediate in form between Types Four and Five (e.g., T. achyrostachys and T. karwinskyana) held moisture much more tenaciously. Tested
Bromelioideae dried to similar degrees. Ananas comosus performed as
expected considering Sideris and Krauss' s (1928) demonstration that intact
shoots required several months to lose about half of their original mass.
Peltate trichomes positioned above the stomata and sometimes colocated
within pronounced intercostal grooves (Figs. 2.8F, 2.13A) help conserve
water for many Bromeliaceae. A dry, re¯ ective indumentum also scatters
considerable sunlight, reducing heat loads and the likelihood of photodamage to underlying chlorenchyma. A large druse crystal positioned in the
center of each cell of the adaxial epidermis augments both functions (Figs.
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CAM vs. C3 bromeliads: performances in situ
151
2.13C, 4.23I). Re¯ ectivity shifted with conditions during experiments on
several Tillandsioideae. Surface-dry foliage of Tillandsia fasciculata
returned up to 45% of the incident radiation between 450 and 600 mm (Fig.
4.14). While wetted, values for the same surfaces fell 25± 50%, to within the
range recorded for Catopsis nutans and several other Type Four species that
also bear widely scattered rather than overlapping trichome shields
(Benzing and Renfrow 1971b; Fig. 2.7B). Baumert (1907) used `thermoneedles' and a galvanometer to demonstrate similar dynamics in some
other bromeliads.
Another aspect of the leaf epidermis may in¯ uence gas exchange and
consequently drought-tolerance for certain Bromeliaceae. Wax deposits
occlude the stoma of sparsely trichomed Tillandsia deppeana, and could
explain why this wide-ranging, generally mesomorphic epiphyte sometimes
accommodates substantial aridity. Perhaps the simplicity of this arrangement, and presumably related ease of modi® cation, favor plant accommodation to long-term shifts in growing conditions better than alterations that
require more fundamental change of, for example, stomatal density, succulence or photosynthetic pathway.
Pittendrigh' s (1948) survey of Bromeliaceae arrayed across the seven climatic zones he recognized for Trinidad (Fig. 4.15) at once demonstrates the
tendency of CAM and C3 types to segregate along regional moisture gradients and the importance of xeromorphy to drought-tolerance. Leaves
serving residents of the everwet, seasonal evergreen, and drier deciduous
forests across the island differed quantitatively by several characteristics
that in¯ uence the accumulation, storage and economical use of water,
including blade thickness, percent area covered by indumenta, and the
dimensions of the trichome shields (Smith 1989; Table 4.9). Moreover,
stomata occurred most densely on the leaves of the least drought-resistant
C3 taxa. Many additional data and the optimization theory discussed below
help explain these associations and identify which bromeliads should
exhibit high or low values for Amax and Emax.
CAM vs. C3 bromeliads: performances in situ
Bromeliaceae offer exceptional opportunity to evaluate the impacts of the
CAM and C3 syndromes on plant ® tness, and compare more immediate
measures of plant performance, because related species distinguished by
these arrangements occasionally co-occur. Plants of both descriptions
monitored in situ in Trinidad and Venezuela exhibited similar, modest rates
of gas exchange, relatively low osmotic pressures, and, at most, moderate
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Carbon and water balance
Figure 4.15. Distribution of epiphytic Bromeliaceae by photosynthetic pathway
along a regional humidity gradient in Trinidad. Letters along the top of the ® gure
indicate habitat type beginning with (a) deciduous seasonal forest, (b) semievergreen seasonal forest, (c) evergreen seasonal forest, (d) lower montane rainforest, (e)
upper montane rainforest and (f) subalpine rainforest (after Smith 1989).
xylem tensions (Smith et al. 1985, 1986; Griffiths et al. 1986; Lüttge et al.
1986a,b; Tables 4.1± 4.5). Here and there, a CAM species transpired more
rapidly than a sympatric C3 type. Diurnal ¯ uctuations in Cleaf were similar
except that lows occurred late in the day and during early morning for
members of the two groups respectively.
Every bromeliad monitored in these studies consumed CO2 slowly
(,3 mmol m22 s21), yet H1max sometimes approached unprecedented highs
± up to 625 mol m23 on a sap volume basis for CAM-equipped Aechmea
nudicaulis. However, recycled CO2 accounted for more than half of the
total (Table 4.4). Water-use efficiency varied among species, the mean transpiration ratios (TR) averaging 42 for nocturnal gas exchange by ® ve CAM
species and 99 for diurnal uptake by four C3 taxa, with some overlap (Table
4.3). Performances over 24 h differed less because WUE diminished during
Cambridge Books Online © Cambridge University Press, 2009
Table 4.8. Leaf surface characteristics and the effects of surface wetting on CO2 uptake by nine ecologically
diverse Bromeliaceae
Trichome density
(mm22)
Species
Wettability of leaf
surface
Ecological type
Adaxial
Abaxial
Adaxial
Abaxial
% inhibition of CO2
uptake when wet
III
I
IV
IV
V
V
V
V
V
3.3
3.0
57.6
31.3
63.1
59.5
45.4
75.3
58.5
22.5
14.1
31.6
14.1
32.0
28.2
42.7
47.9
36.3
Low
Low
Low
Low
High
High
High
High
High
Low
Low
Low
Low
High
High
High
Low
Low
0
0
0
0
Almost complete
Almost complete
Almost complete
0
~50%
Aechmea bracteata
Pitcairnia macrochlamys
Guzmania monostachia
Catopsis nutans
Tillandsia paucifolia
Tillandsia ionantha
Tillandsia tectorum
Tillandsia bulbosa
Tillandsia butzii
Source: After Benzing et al. (1978).
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Carbon and water balance
Table 4.9. Aspects of leaf morphology of Bromelioideae distributed across
three forest types in Trinidad
Lower montane
rainforest
(n510)
Evergreen
seasonal forest
(n56)
Deciduous
seasonal forest
(n53)
0.4260.14
0.7460.31
0.8660.18
Diameter of foliar trichome (mm)
Abaxial
71
Adaxial
36
85
87
124
110
Cover by indumentum (%)
Abaxial
Adaxial
18
19
95
90
1666
0
1964
0
Leaf thickness (mm)
4
1
Stomatal frequency (1 mm2)
Abaxial
24613
Adaxial
0
Source: After Smith (1989).
phase four among the CAM species, while the C3 types lost less water overnight (Griffiths et al. 1986; Smith 1989).
Specimens sampled in Trinidad also demonstrated the sensitivity of
CAM (monitored as DH1) to immediate and previous growing conditions,
speci® cally, time since the last rainfall and irradiance received the day
before. Griffiths et al. (1986) recorded rapid declines in carbon gain after
only one to a few rainless days, a ® nding reminiscent of Adams and
Martin' s (1986a) observations on Tillandsia deppeana. During one of the
night runs, g fell sharply coincident with the arrival of a warmer, drier air
mass, further highlighting the capacity of even the well-watered plant to
sense, probably via stomata, conditions that might compromise water
balance without pre-emptory adjustment (Fig. 4.16).
Most of Griffith et al.' s (1986) subjects were growing in relatively moist
habitats in the north of Trinidad. Less permissive conditions prevail southward, and here photosynthetic pathways more consistently predicted plant
distributions (Fig. 4.15). Segregation by photosynthetic syndrome sharpened along the steep, generally north/south rainfall gradient until only
CAM types, and relatively few of these species, inhabited the driest regions.
A more compressed ordering of similar nature characterized Bromeliaceae
arrayed from lower to upper perches in the wettest montane forests (Fig.
7.11). Only C3 species with lax foliage tolerate deep shade here, while an
assemblage composed of Type Three and Four taxa occurred in the more
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CAM vs. C3 bromeliads: performances in situ
155
Figure 4.16. Effects of an abrupt decrease in ambient relative humidity and higher
temperature accompanying a weather change in Trinidad on Aechmea aquilega and
Aechmea nudicaulis relative to g (conductance) and CO2 exchange. Data points represent averages for both species. Arrow indicates time of weather change (after
Griffiths et al. 1986).
fully illuminated space higher in the canopy. Type Five species were absent
throughout, probably excluded because everwet conditions even in the
most exposed microsites preclude the drying necessary to permit sufficient
gas exchange through dense, hydrophilic indumenta (Fig. 4.11; Table 4.8).
Conceivably, CAM favors survival for some wet-growing populations by
providing needed stress-tolerance during the infrequent, severe drought.
Still, restriction of a species like Aechmea aripensis (CAM) to an extremely
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Carbon and water balance
humid (.6 m year21) habitat on a single mountain seems paradoxical
without imputing some other plant bene® t, or an accident of history such
as a founder event. Perhaps CAM simply represents a suboptimal, but sustainable, anachronism for A. aripensis under present circumstances.
Aechmea, despite its large size and problematic status as a `good' genus
(Chapter 9), appears to be CAM-equipped throughout (e.g., Medina and
Troughton 1974; Medina 1990). But exceptional ecophysiological versatility also characterizes its membership, and may contribute to the survival of
A. aripensis. Recall that A. magdalenae matches extensive, co-occurring C3
¯ ora in its capacity to subsist on shade-light in the understory of humid
Panamanian forest.
Bromelioideae further demonstrate the puzzling juxtaposition of CAM
and high humidity with additional taxa like A. bromeliifolia, several
Billbergia species, Nidularium procerum and Quesnelia quesneliana, all of
which occasionally root in continuously sodden soils in Brazilian restinga,
sometimes in standing water during the rainy season (Fig. 7.13B). Yet by
leaf texture and general structure, these plants look like many other CAMtype bromelioids. CAM has receded somewhat in at least a few populations
native to exceptionally dark, moist habitats (e.g., Nidularium innocentii,
D524½ ; Medina et al. 1977). Apparently, greater capacity for C3 photosynthesis than usual for Bromelioideae favors at least some of the species
that grow under conditions usually associated with this syndrome.
Zotz and Andrade (1997) compared Guzmania monostachia and
Tillandsia fasciculata to discover why these two wide-ranging bromeliads
partition microsites by high vs. more moderate exposure on pond apple
trees on Barro Colorado island in the Republic of Panama. Their unusually comprehensive examination of water relations revealed how many
dimensions of plant structure and function beyond photosynthetic
pathway determine vulnerability to drought. On ® rst glance, thinner, less
conspicuously trichomed foliage and C3± CAM status suggest that
Guzmania monostachia should desiccate faster during the approximately
four-month dry season that prevails at the study site. Indeed, leaf areabased transpiration rate exceeded that of Tillandsia fasciculata by about
15%. Still, drought-tolerance was impressive for both species, especially
adults, because additional plant attributes brought the overall water relations of these two epiphytes into closer conformity.
Guzmania monostachia and Tillandsia fasciculata both produce tanks,
but ratios of plant water content to impoundment capacity for the second
species (,1.7) change little after the diameter of the shoot exceeds several
centimeters (after impoundment becomes possible), whereas values for
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CAM vs. C3 bromeliads: performances in situ
157
Figure 4.17. Relationship between leaf area (LA) and plant water content (PWC) as
a function of plant size for Guzmania monostachia. Each data point represents a
separate plant (after Zotz and Andrade 1997).
Guzmania monostachia peak and even fall below 1.0 during the same, relatively vulnerable early part of the life cycle. Values for adults compare
closely with those of Tillandsia fasciculata (1.7). Leaf area to plant water
content ratio falls sharply over the same interval, demonstrating in part
why seedlings experience stress sooner than adults denied irrigation under
the same conditions (Fig. 4.17).
Water potential and solute or osmotic potential (p) ¯ uctuate in tandem
over the year, whereas DH1 indicates continuously more pronounced CAM
in T. fasciculata (Fig. 4.18). Although capacitance is substantially higher
for T. fasciculata (0.70 vs. 0.30), Guzmania monostachia recovered following more severe desiccation (60 vs. 90%). In the ® nal analysis, plants denied
irrigation lost similar amounts of moisture for the ® rst 4± 5 days, and, following stomatal closure, held the remaining stores of water with about
equal success. Leaf C never fell below 20.8 MPa.
Just as Smith et al. (1985, 1986), among others, discovered among the
bromeliads of Trinidad, photosynthetic pathway did not reconcile with all
of the other determinants of water relations, i.e., speci® c mechanisms
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Carbon and water balance
Figure 4.18. Aspects of water relations of Guzmania monostachia and Tillandsia fasciculata. (A,B) Seasonal shifts in the diurnal ¯ uctuation of DH1. (C,D) Seasonal
¯ uctuations in osmotic pressure and water potential (after Zotz and Andrade 1997).
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CAM vs. C3 bromeliads: performances in situ
159
presumed to foster drought-endurance are not always coincident. Two
explanations for this inconsistency come to mind: (1) different combinations of plant features yield comparable results (equivalent drought-tolerance), or (2) CAM in such cases provides different plant bene® ts. Guzmania
monostachia, whose more desiccation-tolerant foliage transpires relatively
rapidly, may rely on CAM primarily to avoid photodamage rather than
conserve moisture. Maxwell et al.' s (1992, 1994, 1995) ® ndings clearly
support this contention for G. monostachia, although the same bene® ts may
apply for Tillandsia fasciculata.
Returning to Zotz' s question about distributions on pond apple trees,
Tillandsia fasciculata may be better equipped to grow where exposure
(drought-stress) is more severe in Panama because its seedlings (but not
adults) maintain a lower ratio of leaf area to total water content than
Guzmania monostachia (although the latter species has greater relative
impoundment capacity as a juvenile). Consequently, losses relative to internal reserves are signi® cantly lower than those experienced by Guzmania
monostachia subjected to the same evaporative demand. Zotz' s (1997b) discovery that Amax (and E) increase with plant size further underscores the
need to know more about the factors that affect carbon and water balance
than photosynthetic pathway to explain why co-occurring Bromeliaceae
often distribute differently along environmental gradients.
Finally, Zotz and Thomas (1999) modeled Guzmania monostachia and
Tillandsia fasciculata to compare how effectively phytotelmata supply
plants in lieu of water-absorbing roots. Speci® cally, they inquired whether
impoundments deliver year-round or only seasonal supplies of moisture for
plant use, and if one of these two bromeliads or a particular life stage bene® ts more than another. Factors that potentially distinguish these two epiphytes on this basis include the characteristics just mentioned and several
more that also affect water balance. Actual measurements (e.g., time
required for ® lled tanks to dry out) conducted in situ on Barro Colorado
island provided data for model validation.
Simulations indicated that seedlings should experience longer periods
with empty impoundments than adults growing under the same conditions
in seasonal Panamanian forest. Additionally, shoots of adult Guzmania
monostachia would lack foliar reservoirs for fewer days during the year
(total of about one month) and have to endure no more than 12 successive
days of such deprivation compared with Tillandsia fasciculata (about two
months and 16 days respectively). Success of phytotelm Bromeliaceae
facing drought will also depend on additional species-speci® c parameters
not included in the model such as sensitivity of stomata to humidity (Fig.
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Carbon and water balance
Figure 4.19. Effects of abrupt change in chamber air relative humidity (RH) on CO2
exchange by Tillandsia usneoides. Daytime RH was 55%, night-time RH was 92%
up to arrow at which time RH was reduced to 72%. RH was than increased to 95%
and maintained at this level for the rest of the night (after Martin and Siedow 1981).
4.19), tolerance to desiccation and how rapidly tissues reach lethal water
contents after tanks empty. Presumably, the relative performances of these
two bromeliads and their life stages shift along environmental gradients
(i.e., at locations featuring different patterns of rainfall and evaporative
demand).
Predictors of photosynthetic capacity (Amax)
Land plants, presumably including Bromeliaceae, combine aspects of leaf
structure, chemistry, physiology and life span to optimize photosynthesis
relative to available photons, water and key nutrients (Farquhar and
Sharkey 1982). Coordination is particularly tight between A and g and N
content, the nutrient that inordinately in¯ uences Amax (Chapter 5). The
interactive effects of environment and plant on A and water use range from
transitory (e.g., minutes for stomata to substantially alter g in response to
abruptly drier air; Fig. 4.16), to orders of magnitude slower (e.g., improved
N nutrition that requires days to weeks to elevate inherent photosynthetic
capacity; Fig. 4.6). Heterophylly and deciduousness in¯ uence patterns of
water use and carbon gain over weeks to months (Fig. 2.12A).
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Predictors of photosynthetic capacity (Amax)
161
Coordination of the sort imputed by optimization theory maximizes the
utilization of plant potential (Amax), while minimizing unnecessary expenditures of water to produce the currency (photosynthate) crucial to ® tness.
Mediation by the plant is largely effected through regulation of guard cell
physiology, which in turn affects g, such that immediate plant capacity to
® x CO2 is fully engaged, i.e., water use to gain carbon is optimized within
certain genotype-speci® c constraints described below. Consequently, WUE
changes less under unstable conditions than a less responsive (less capacity
for both feed-forward and feed-back regulation of g, hence the CO2 supply
to chloroplasts) system would allow (e.g., Fig. 4.10).
Because PPFD and VPD in¯ uence A and E, and like many other aspects
of the environment they both ¯ uctuate in situ, stomata must continuously
adjust to stabilize WUE. Other factors that affect the same two processes,
like supplies of moisture and nutrients, change more slowly and accordingly, so do the plant responses that optimize their use to harvest photons.
Occasional events, like the abrupt arrival of that drier air mass in northern
Trinidad, temporarily override plant propensity to optimize E and maximize A, for a time denying the mesophyll full utilization of its immediate
potential to ® x CO2 (Fig. 4.16). Threatening conditions simply take precedence, reducing short-term gains in favor of plant survival.
All ¯ ora possess some capacity to optimize water use as growing conditions change, but ecophysiological performances vary within plant-speci® c
limits that constitute adaptations to the extent that they match requirements for survival in native habitats. In essence, Amax and WUE represent
set points adopted to accommodate routine growing conditions, especially
PPFD and water and N supplies. Leaf structure, function and longevity
evolve in tandem to achieve rates of resource use (and determine related
demands) and A appropriate for speci® c environmental contexts and
important aspects of the plant (e.g., shoot/root ratio, type of life history).
Values for A that fall at the low end of the range for all ¯ ora, and the opposite for WUE, indicate that the bromeliads routinely fail to encounter the
conditions necessary to sustain more vigorous photosynthesis and meet the
accompanying elevated demand for water (Tables 4.1, 4.3, 4.4; Fig. 4.7).
The inverse relationship between Amax and WUE has major biological
consequence. Land-dwelling ¯ ora achieve either high WUE, an outcome
that promotes ® tness in physically stressful (usually droughty) habitats, or
substantial vigor, a sounder response to the stiff competition fostered by
more resource-rich (humid) ecospace. Bromeliaceae generally ® t the ® rst
more closely than the second strategy according to leaf morphology
in addition to those modest values for A, g and E. Densities of stomata
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162
Carbon and water balance
(generally low) parallel the gas exchange data for most of the examined C3
and CAM bromeliads, i.e., they correspond to the modest demands for CO2
at Amax (see summarized data in Martin 1994). Foliar anatomy of course
reveals little about g, or whether components other than the guard cells
control gas exchange, as some unusually structured stomata prompted
Tomlinson (1969) and several earlier morphologists to suggest (Figs.
2.13B,C, 2.17A).
Hydration
Foliar trichomes in¯ uence leaf energy budgets, light reception and water
retention across Bromeliaceae, and for the more specialized species they
also mediate mineral nutrition and rehydration. The importance of roots
and their cost relative to the shoot shifts accordingly, diminishing as the
foliar epidermis becomes increasingly multifunctional and the body plan
deviates from the typical arrangement among monocots (Table 4.2). Brie¯ y,
bromeliads assigned to Type One and many members of Type Two, Three
and Four produce relatively extensive, presumably fully operational root
systems. Even the heavily scleri® ed organs of at least some dry-growing
Tillandsioideae (e.g., Tillandsia subgenus Diaphoranthema) contain some
well-developed water-vascular cells (Cheadle 1955). At the other end of the
plant, absorptive scales line the phytotelma of Type Two, Three and Four
Bromeliaceae; those serving Type Five Tillandsioideae perform the same
tasks over the entire shoot. A few of these most specialized species lack
roots as adults (e.g., Tillandsia usneoides, T. duratii; Fig. 2.10L).
Information on root function is easily summarized. Ekern' s (1965)
inquiry on pineapple demonstrated substantial contributions from soil
roots to water balance, and Burt and Benzing (1969) and Nadkarni and
Primack (1989) monitored the movements of radionuclides, presumably
via the xylem, from potting media to the foliage of several Type Three and
Four species. Sieber (1955) determined that feeding through roots
enhanced the growth of several ornamental species over that effected by
placing the same solutions in phytotelmata. However, only the ® rst of these
reports identi® es the volumes delivered, and none addresses the possible
occurrence of mechanisms that insulate the aerial roots from dry air
without compromising access to typically intermittent moisture supplies.
Brighigna et al. (1990) described unusual cell structure and hydrophilic
materials in the root caps of two Type Five Tillandsia species, but they suggested importance for anchorage rather than for water balance.
Moisture absorbed through the bromeliad leaf may enter by two routes.
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Hydration
163
Benzing et al. (1976), Owen et al. (1988, 1991) and Owen and Thomson
(1988) con® rmed trichome involvement in the uptake of several solutes and
presumably water as well (Chapter 5). Sakai and Sanford (1979) reported
extensive membranes and other suggestive ultrastructure in the stalk cells
of the scales located on the leaf bases of pineapple, as did Dolzmann (1964,
1965) and Brighigna et al. (1988) for those of Tillandsia usneoides.
However, water may penetrate less specialized regions of the epidermis
adjacent to the phytotelmata where cell walls and cuticle thin out.
Type Five bromeliads employ trichomes in the way ® rst envisioned by a
number of European botanists about a century ago (e.g., Mez 1904).
Considerable study followed (e.g., Benzing and Burt 1970; Table 4.10), but
consensus on some important details, for example whether the most leafdependent species obtain signi® cant amounts of moisture from vapor in
air, came later. Suggested alternatives (Haberlandt 1914, Dolzmann 1964,
1965) aside, a simple osmomechanical mechanism adequately explains how
the trichome of dry-growing Tillandsioideae relieves water de® cits (Fig.
2.7A,B).
Early investigators, including Mez (1904) and Haberlandt (1914), con® rmed the dual roles the tillandsioid trichome plays in moisture and nutrient absorption by noting the effects of vital dyes and hypertonic solutions
placed on intact leaf surfaces. Stalks and adjacent mesophyll stained and
plasmolyzed respectively, whereas neighboring epidermal cells remained
unaffected. Dense indumenta proved to be especially well suited to magnify
the bene® ts of light showers that only brie¯ y moisten shoots. Rather than
beading up as occurs on most foliage, drops rapidly spread to wet much
more surface. Each trichome within range immediately imbibes enough
water to engorge the four large cells dominating the central disc, which in
turn bulges upward causing the attached wing to ¯ ex down against the leaf
surface (Fig. 2.7A,B).
As the indumentum of many a Type Five Tillandsia dries, the central disc
in each shield collapses, ¯ exing the wing upward to re-establish the trichome' s full protective powers. Speci® cally, a stout plug comprised of the
much thickened outer tangential walls of the four innermost disc cells
effectively seals off the underlying dome cell, preventing moisture from
wicking up from the mesophyll along its path of entry. The indumentum' s
recti® cation of moisture exchange across the epidermis of these drygrowing bromeliads parallels the operation of the root cortices of certain
desert terrestrials (Nobel and Sanderson 1984). Trichomes also moderate
stress by scattering incident radiation, which in exposed habitats often
exceeds plant needs and may impede photosynthesis by inhibiting
Cambridge Books Online © Cambridge University Press, 2009
Table 4.10. Desiccation over CaCl2 of leaf discs (midblade) of 13 bromeliads representing all three subfamilies and the five
ecological types
Subfamilies and
species
Mean density of
trichomes (mm22)
Ecological
type
Mean dry weight of
9 mm discs (mg)
III
III
II
II
I
13.3
7.9
11.5
20.5
8.9
19.1
15.2
23.9
12.6
26.9
Pitcairnioideae
Pitcairnia undulata
Pitcairnia macrochlamys
I
I
5.8
4.3
Tillandsioideae
Catopsis berteroniana
Guzmania lingulata
Tillandsia achyrostachys
Tillandsia karwinskyana
Tillandsia multicaulis
Vriesea carinata
IV
IV
V
V
IV
IV
4.2
3.8
12.0
14.4
5.1
3.0
Bromelioideae
Aechmea bracteata
Aechmea tillandsioides
Ananas comosus
Bromelia balansae
Cryptanthus acaulis
% surface
covered
by shields
Adaxial
Abaxial
% H2O de® cit after ® ve
days over CaCl2
20.4
8.7
43.5
41.3
36.9
15
35
80
35
60
20
20
90
90
85
20.5
34.5
23.8
19.8
37.2
0
0
34.8
43.4
0
0
95
95
29.0
28.1
16.5
17.4
60.9
82.6
36.9
24.0
18.7
20.9
40.0
63.0
40.5
21.9
2
4
95
95
4
4
2
4
80
60
4
4
41.5
47.9
10.2
18.2
50.6
40.0
Adaxial Abaxial
Source: After Benzing and Burt (1970).
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Hydration
165
Figure 4.20. Partial desiccation and rehydration of excised leaves of Tillandsia streptophylla during exposure to water-saturated air and liquid moisture (after Benzing
and Pridgeon 1983).
photosystem II. In summary, trichomes of the most specialized Bromeliaceae act as one-way hydraulic valves and energy dissipaters, alternately
charging the plant with moisture and insulating it against avoidable drying
and excessive insolation.
Leaf blades of Tillandsia streptophylla (Type Five) maintained for three
days over CaCl2 desiccated about 30%, and then gained no weight during
a fourth day in a moisture-saturated atmosphere (Fig. 4.20). However, the
same samples fully recovered in a water bath within a few more hours.
During another run, Catopsis nutans, a soft-leafed, sparsely trichomed
Type Four species, lost more weight and failed to rehydrate appreciably
while surface-moistened with mist (Fig. 4.21). Additional bromeliads
treated identically performed similarly, recharging within 12 h in liquid
water only if members of Type Five (e.g., Tillandsia schiedeana; Fig. 4.21;
see also Benzing and Burt 1970). Studies in Puerto Rico on Tillandsia recurvata and T. usneoides demonstrated that these two wide-ranging species
could also rapidly eliminate substantial de® cits incurred over several weeks
of rainless weather (Biebl 1964).
More information on moisture exchange, some of it contradictory, exists
for Tillandsia usneoides than for any other bromeliad. Penfound and Deiler
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166
Carbon and water balance
Figure 4.21. Partial desiccation and rehydration of excised leaves of Tillandsia schiedeana and Catopsis nutans (after Benzing and Burt 1970).
(1947) noted sizable and precipitous weight changes in plants monitored in
a closed room in southern Louisiana (Fig. 4.12). Humid air promoted substantial rehydration (discussed in more detail later). Martin and Schmitt
(1989) examined Spanish moss for an entire year in North Carolina where,
during the course of a 20-day drought, trusses lost about three-quarters of
the water present at the beginning of that episode.
Similar performances by T. ionantha prompted Benzing and Dahle
(1971) to suggest that some Type Five Tillandsia approach poikilohydrous
status on three counts. Like true resurrection plants, these bromeliads also
rehydrate across intact leaf surfaces, lose moisture rather quickly to dry air,
and tolerate severe desiccation, although not the 95± 97% de® cits routinely
experienced by many bryophytes and some ferns. However, recall that Cleaf
remains high and the chlorenchyma turgid, probably even in severely dehydrated specimens, features foreign to poikilohydry, but expected of succulents.
Picado (1913) proposed that Type Five bromeliads make unusually
effective use of water vapor, a claim subsequently supported and challenged. Trusses of Spanish moss changed weight in concert with shifting
relative humidity (RH) during crude experiments performed by Penfound
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Hydration
167
Figure 4.22. Mean changes in tissure water content for ® ve clumps of Tillandsia
usneoides held for three days at 30 °C, 50% RH during the photoperiod and 30 °C,
90% RH at night (after Martin and Schmitt 1989).
and Deiler (1947; Fig. 4.12). Another set of plants droughted to an average
222% water content had rehydrated to 506% after two days in humid air
(.90% RH). According to De Santo et al. (1976), several Type Five bromeliads among the 10 they tested absorbed moisture from drying atmospheres (,35% RH), but weight gains were minor compared with those
reported by Penfound and Deiler. Species from relatively arid habitats (e.g.,
Tillandsia schiedeana) hydrated most during the 12-h runs, while relatives
from wetter forest (T. flabellata) weighed no more after treatment than
before. De Santo et al. erroneously concluded that `moisture is captured by
the dead (shield) cells and taken into the mesophyll through the living stalk
cells' . Martin and Schmitt (1989) conducted the most de® nitive study of
moisture exchange to end the controversy.
Figure 4.22 illustrates how clumps of T. usneoides responded during threeday runs as RH oscillated between 30 and 90%, and air temperature remained
at 30 °C (Martin and Schmitt 1989). Fluctuating plant weights accord with
the presence of a proportionally (relative to the whole plant) small volume of
strongly hygroscopic tissue. Findings by De Santo et al. (1976) had also suggested that the shoots of Spanish moss consist of two compartments that
differ in size and affinity for water vapor in adjacent air. Uptake was modest
because only the indumentum possesses sufficient hygroscopic power to draw
water from a subsaturated atmosphere, whereas the mesophyll accounts for
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168
Carbon and water balance
most of the leaf volume. Recall that succulents, including the thick-leafed
bromeliads, maintain Cleaf at .21.0 MPa, whereas water at 99% RH and
20± 30 °C in air, for example, exists at values many fold lower. Osmotic potentials determined for diverse Type Four and Five Tillandsioideae never fell
much below 21.0 MPa, and most readings were closer to half that value
(Harris 1918; Biebl 1964; Smith et al. 1986; Fig. 4.18).
Water vapor surely promotes bromeliad water balance, but without condensation only by slowing E as for other land ¯ ora. Withhold irrigation and
death inevitably follows. Tillandsia usneoides died after being shielded from
rain for four months even while suspended above the ¯ oor of a swamp
forest (Garth 1964). Some of Penfound and Deiler' s (1947) results either
contradict physical principles or vapor condensed unnoticed on shoots
during the runs (Fig. 4.12). Even so, declining weights indicated that longer
experiments would likely have ended as Garth' s did.
CAM reconsidered as an evolutionary response to stress
Data on CAM and related ecology for Bromeliaceae may exceed that available for any other family; nevertheless, a full accounting of its signi® cance
to these plants remains elusive. As indicated above, especially vexing is the
frequent association of CAM with everwet climate, or, where precipitation
is more seasonal, with phytotelmata sufficient to provide plants continuous
access to water. Could the bene® ts of CAM for these bromeliads still relate
primarily to water balance and only apply during the exceptional 10, 25 or
50-year drought with negligible consequences for ® tness the rest of the
time? Perhaps the unpredictability of the moisture and photon supplies in
and under the forest canopy account for the overoccurrence of this syndrome among many Bromeliaceae.
Maxwell et al. (1992, 1994, 1995) demonstrated that the advantages of
avoiding photoinhibition probably explain the presence of facultative
CAM in Guzmania monostachia, but what about the importance of this
syndrome relative to other dimensions of the light environment? CAM may
enhance plant access to energy delivered in sun ¯ ecks by relaxing the
requirements for stomatal control that some C3-equipped understory ¯ ora
employ to coordinate CO2 supply with brief surges in PPFD. Abruptly ¯ uctuating irradiance might have less impact on WUE if CO2 supplied from
stored malic acid allows g to remain continuously low through much of the
photoperiod (see also Skillman and Winter 1997). Rehydration is another
possibility considered later.
Finally, might the mix of CAM-mediated plant responses and the result-
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CAM reconsidered as an evolutionary response to stress
169
ing bene® ts routinely shift over the year for many Bromeliaceae? Below, we
review one more set of studies to consider some mechanisms that help
certain CAM, and perhaps certain C3, bromeliads coordinate diverse
signals from the environment and physiological status to minimize plant
stress and maximize resource-use efficiency as growing conditions change.
Carbon recycling lies at the heart of this issue.
CAM-idling and recycling
Current wisdom assigns CAM in its idling mode importance as a stressmitigating, maintenance mechanism ± a state of quiescence rather than
dormancy ± that keeps the mesophyll primed for renewed opportunity, viz.
renewed water supply. As stomata close while desiccation progresses and E
falls, idling ensues and CAM, now totally dependent on respired CO2,
hence diminished overall, continues to provide enough energy to avoid
death, or the need to lapse into an inactive condition from which recovery
would be slow. Idling also maintains a CO2 source to help protect the lightharvesting apparatus (Maxwell et al. 1992, 1994, 1995). Photosynthesis for
the CAM-idling plant returns to pre-stress levels within hours to a day or
two following return to wet weather, much faster than possible for a
drought-avoiding shrub, or a similarly deciduous Pitcairnia that likewise
must ® rst regenerate its canopy.
One of the most perplexing facets of CAM concerns certain details of
carbon management, particularly the continued prominence of CO2 recycling in recovered foliage and sometimes leaves that never experienced
severe drought. Why do apparently well-watered subjects so often depend
so heavily on recycled CO2 compared with inputs from the atmosphere?
According to Martin (1994), CAM-idling in the strictest sense (recycled
CO2 accounts for 100% DH1) has never been recorded for a bromeliad (but
see Stiles and Martin 1996). However, many plants examined in situ were
processing much more carbon than could be accounted for by gas
exchange, and often well above what seemed necessary.
Griffiths et al. (1986) and Griffiths (1988) reported values ranging from
50 to 99%, sometimes even during fairly wet weather, for the diverse taxa
included in their survey in Trinidad (Table 4.4). Thoroughly irrigated subjects exposed to a variety of growing conditions have often behaved similarly. Why were these plants gaining carbon so feebly compared with
respiration, even while seemingly unstressed? Before trying to answer this
question, we need to revisit the relationship between carbon and water in
the context of CAM.
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170
Carbon and water balance
The algorithm used to calculate fractions of DH1 attributable to recycled
carbon vs. exogenous CO2 employs the stoichiometry of two titratable H1:
one malic acid molecule: one CO2 molecule. Internally generated CO2 represents the balance remaining after subtracting from DH1 the amount from
outside according to measured gas exchange. Whatever other bene® ts
accompany CAM, its capacity to recycle dark-respired CO2, whether in or
out of the idling mode, promotes WUE in the same way described earlier
for the CAM-cycler (see also Martin et al. 1988). Fetene and Lüttge (1991)
proposed using the ratio of moisture saved through recycling to transpiration, which, by substituting A/E for WUE, was reduced to estimate the
advantages of CAM to water balance in Bromelia humilis.
Bromelia humilis also demonstrated how cues related to growing conditions affect the carbon budget of a CAM bromeliad. More precisely, Fetene
and Lüttge illustrated why well-watered plants sometimes rely so heavily on
respired compared with exogenous CO2 ± why, despite adequate irrigation,
they so readily reduce g. Respiration always assures some recycling, but
only enough to account for a small fraction of H1max while CAM remains
robust, i.e., while CO2 reaching PEPc from the atmosphere greatly exceeds
the supply from mitochondria. The acidity assignable to recycling by nonstressed CAM types should approximate DH1 in an otherwise comparable
CAM-cycler because the stomata of the cycler close at night, trapping
endogenous CO2 for nonautotrophic re® xation.
Recall that Fetene et al. (1990) and Fetene and Lüttge (1991) demonstrated how well-fertilized and N-deprived B. humilis pretreated at two
exposures gained different amounts of carbon under the same high and low
PPFDs (Figs. 4.5, 4.6). They also manipulated drought-stress, leaf-to-air
VPD and night-time temperature to note shifting dependency on recycled
vs. exogenous CO2. While these data provide no de® nitive answers, they
suggest some intriguing possibilities and underscore the complexity of the
CAM syndrome and its sometimes dubious utility as an indicator of ecophysiological status (prevailing plant stress). More importantly, their
manipulations demonstrate how disparate aspects of the environment,
both historic and immediate, can affect the operation of CAM. Bromelia
humilis, at least, shifts toward CAM-idling whether challenged by N-de® ciency, drought, high temperature or steep VPD in night air, i.e., the same
plant response reduces vulnerability to several threats to water balance and
perhaps other essential processes like light harvest.
High temperatures at night (.30 °C) shifted 24-h carbon budgets closer
to or into negative territory, and more substantially for 2N than for 1N
plants. Relative reliance on recycled CO2 for phase one increased apace
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CAM reconsidered as an evolutionary response to stress
171
until at 35 °C, contributions from respiration about equaled the amounts
of CO2 derived from the atmosphere at 20 °C (30 mmol m22 12 h21 for 1N
plants and 18 mmol CO2 m22 12 h21 for subjects grown on unamended
soil). CO2 uptake responded more sensitively to temperature than DH1,
and about equal amounts of acid accumulated at 35 °C and 20 °C, perhaps
due to an unusually high temperature coefficient (Q10) for dark respiration
as Lüttge and Ball (1987) noted for some other CAM bromeliads.
Regardless of pretreatment, dark respiration rose exponentially with temperature, but more in 2N plants than in better-nourished specimens.
Temperature coefficients ranged between 2.3 and 3.0 (10± 25 °C) with 2N
plants, once again exceeding the responses of better-fertilized subjects.
The more elevated of the two applied VPDs (7.46 Pa KPa21 vs. 15.49 Pa
KPa21) reduced CO2 uptake to different degrees depending on pretreatment. Reliance on recycling was about 2± 6-fold greater at the higher VPD.
Water saved by recycling as equivalents of E (ratio of recycled CO2 to net
nocturnal CO2 assimilation) increased from 0.08 to 0.60 at the lower VPD
and from 0.80 to 3.0 at the higher one. Thus, at the lower VPD, amounts of
water equal to only 8± 60% more than the total transpired remained unexpended, while savings in drier air rose to 80± 300%. Less moisture-saturated
air had reduced g to just 5± 23% of that prevailing when the more humid
atmosphere had threatened plant water status less. Ten days of drought
almost shut down CO2 uptake and reduced H1max to just 30± 40% of prestress levels. However, recycling increased proportionally from about
25± 35% to near 100%. By day 10, the water saved by recycling amounted
to 2± 6-fold the quantity that plants had transpired. After 12 days, CO2
uptake almost ceased, indicating that the protection afforded by reducing
g developed much faster here than for some nonbromeliads.
Agave deserti, Opuntia ficus-idea and Ferrocactus acanthoides required
11± 20 days just to reduce initial rates of CO2 uptake 50% in another study
(Nobel 1988). Apparently, CAM serves Bromelia humilis quite well in its
highly seasonal, hot and probably often infertile habitats. Rather than an
all-or-nothing response, proportional reliance on endogenous CO2 waxes
and wanes with ¯ uctuations in several aspects of the environment capable
of reducing water economy and growth and, if severe enough, of in¯ icting
serious plant injury. Sensitivity, if greater here than usual, would mean that
this bromeliad anticipates threatening conditions sooner than some other
CAM types. Or modest capacitance may simply permit water-stress to
develop faster for Bromelia humilis compared with these other xerophytes
when subjected to comparable droughts. Viewed either way, an unusually
sensitive response to conditions that can suppress phase one of CAM (e.g.,
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Carbon and water balance
high temperature, poor nutrition) or accelerate E (e.g., high temperature,
high VPD) mitigates the liability imposed by the low capacitance (for a
CAM plant) of this bromeliad, thus promoting its tolerance to diverse
kinds of stress.
Sensitivity to VPD allows plants to reduce nonproductive water use, but
do responses vary among Bromeliaceae according to other plant characteristics that in¯ uence vulnerability to drought? Dry air reduces g for
Tillandsia usneoides (see Lange and Medina 1979; Fig. 4.19), but species
with substantial capacity to replace losses from large phytotelmata (e.g.,
Aechmea nudicaulis, A. aquilega) behave the same way, although perhaps
less sensitively. Light constitutes another agency that effects rapid changes
in g and accordingly, shifts relative dependence on atmospheric vs. respired
CO2 among CAM bromeliads. Tillandsia usneoides recycled proportionally
more carbon after transfer to higher PPFD (Martin et al. 1986), whereas
Aechmea nudicaulis did so upon relocation into shade (Griffiths et al. 1986).
Finally, chronic, pronounced recycling need not seriously limit growth.
Cultivated Ananas comosus rivals some C3 crops for the production of dry
matter, yet recycling accounted for 45% of DH1 in one analysis involving
irrigated specimens (Sale and Neales 1980).
So it seems that a variety of chronic and more transitory stresses, including excessive temperature, nutrient scarcity and suboptimal VPD, promote
heavy dependence on recycled CO2 in at least some CAM bromeliads.
Signi® cantly, all of these challenges from the environment in¯ uence plant
water economy and carbon budgets at least indirectly (e.g., N status
through its effects on A). Still, drought often appears to act most decisively,
although unevenly according to several studies on Type Five Bromeliaceae
in the laboratory and ® eld (see Fig. 4.15 for strong circumstantial evidence).
Several of these investigations indicate how drought probably affects recycling for the more notably stress-tolerant epiphytes.
Whereas less than 50% of the titratable acidity present in the wellwatered shoots of usually arboreal Tillandsia schiedeana (Type Five) at
dawn had come from recycled CO2, 30 days without irrigation in a growth
chamber boosted that ® gure to about 90% (Martin and Adams 1987).
Recycling varied more over the year on an absolute than on a proportional
basis in Tillandsia flexuosa growing in one of its semiarid coastal
Venezuelan habitats (Griffiths et al. 1989). Recycled carbon accounted for
76 vs. 73% of the total acid synthesized from mid-wet to mid-dry season,
although H1max diminished 35% as aridity intensi® ed. Exogenous CO2
accounted for only 1% of the malic acid accumulated by terrestrial
Bromelia plumieri in Trinidad (Griffiths et al. 1986; Table 4.4). Neither
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CAM reconsidered as an evolutionary response to stress
173
moisture-stress nor nutritional de® ciencies were mentioned, but readings
date from February and March, two especially arid months (,25 mm precipitation) at this strongly seasonal site. On that occasion, no rain had
fallen for several weeks.
Thicker-leafed Aechmea fendleri recycled proportionally more CO2 than
A. nudicaulis, suggesting that succulence may elevate endogenous CO2
enough to simulate a stress symptom in a relatively well-hydrated subject.
However, Griffiths (1988) considered hydrenchyma too inert to account for
the difference, and Lüttge and Ball (1987) supported his assessment with
data from additional species. While achlorophyllous storage tissue comprised 60± 75% of the mesophyll of Hechtia glomerata, it accounted for only
9.5% of the CO2 available for recycling. The presence of exceptionally
active tissue constitutes another possibility that has some support. Several
CAM plants endemic to warm habitats, including three bromeliads
(Aechmea fasciata, Ananas comosus, Hechtia glomerata), exhibited dark
respiration with Q10s that ranged from 2.13 to 4.09 between 10 and 30 °C.
Additionally, all CAM plants require ATP to mediate the massive traffic in
malate across the tonoplast. Finally, a biochemical peculiarity also in¯ uences how much endogenous CO2 certain CAM plants produce compared
with others. Bromeliads may stand out because they consume free hexose,
which assures relatively high rates of respiration, rather than the glucans
many other CAM plants (e.g., Kalanchoe) employ to drive phase one.
Loeschen et al. (1993) used 12 dry-growing Tillandsia species to rule out
nongreen tissue as a major source of CO2 for phase one. Recycling did not
correlate with leaf anatomy; in fact only one subject, T. schiedeana, deviated substantially from the 1:1 ratio mandated by the stoichiometry of
malic acid production during CAM (Fig. 4.13). Tillandsia schiedeana alone
acidi® ed beyond what could be explained by the consumption of exogenous CO2. Several other taxa yielded values above one, but less than two.
Note that T. schiedeana (30% water-storage tissue) occurs about midway
within the range (0± 53%) exhibited by their sampling. Tillandsia usneoides
produced a modestly positive value despite its undifferentiated mesophyll
(Fig. 2.10A), while T. valenzuelana (53%) synthesized less acid than gas
exchange predicted. Different degrees of stress supposedly accounted for
the mixed results, and this explanation is plausible given the single pretreatment provided to all 12 of these ecologically diverse species.
Additional inquiry might pro® tably focus on the functions of foliage
with anatomically uniform vs. dimorphic mesophyll. Perhaps drought
depresses A in a less precipitous fashion among subjects with the second
compared with the ® rst type of leaf structure, i.e., one or the other kind of
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Carbon and water balance
plant reduces g sooner as water de® cits develop. Green cells in T. usneoides
presumably lose turgor faster when plants are subjected to drought than
those of species featuring hydraulic coupling to collapsible, water-storing
parenchyma. Moreover, architectural constraints may oblige a speci® c type
of leaf anatomy even if another option would grant superior drought-performance. Perhaps the leaves of Spanish moss are simply too small to
support a division of labor between water storage and photosynthesis.
Finally, what other physiological or structural peculiarities co-occur with
an anatomically undifferentiated mesophyll? And what about those exceptionally thin epidermal layers and delicate cuticles illustrated in Fig. 2.10?
Citric acid: its role in ecophysiology
Citric acid affects a variety of cellular processes central to the ecology of
some (e.g., Clusia species; Franco et al. 1992) and perhaps many CAM
plants. Substantial amounts of this tricarboxylic acid augment malic acid
to account for DH1 in certain species ± 30± 50% of H1max depending on N
supply and PPFD in a study using Bromelia humilis (Lee et al. 1989). These
two acids share several and differ in other qualities that in¯ uence carbon
and water balance and stress-tolerance. Malic, but not citric, acid synthesis can effect carbon gain and heighten WUE (Lüttge 1988; Franco et al.
1992). However, citric acid synthesis does recycle carbon, and, like malic
acid, it increases p (although only one-half as much) if starch or some
other polymer constitutes the substrate (Lüttge 1987, 1988).
Citric exceeds malic acid for capacity to supply CO2 to chlorenchyma
(three vs. one CO2 per molecule) during phase three when overexposure and
stomatal closure maximize potential for photoinhibition (see below). Citric
compared with malic acid synthesis also yields substantially more reducing
power (Lüttge 1988). Finally, citric acid endows vacuoles with high
buffering capacity, a fact that may explain why some Bromeliaceae (e.g.,
Aechmea nudicaulis, as discussed below) exhibit such vigorous CAM
despite distinctly nonsucculent foliage.
CAM and hydration
Bromeliads account for some of the highest DH1 values recorded, but
rarely were the responsible solutes (citric vs. malic acid) identi® ed (Table
4.4), obscuring potential consequences for photoprotection, energetics and
hydration. On this last point, CAM purportedly allows succulent Senecio
medley-woodii (Asteraceae) to access additional moisture from desert soils
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CAM and hydration
175
(Ruess and Ellers 1985). Martin (1994) sought evidence of coupling
between hydration and Cleaf in Tillandsia ionantha, as did Schmidt and
Blank (see Lüttge 1987, 1988) using T. recurvata, neither attempt having
notable success. Findings on other species make a somewhat better case.
Aechmea nudicaulis in Trinidad exhibited a mean nocturnal depression of
0.52 MPa associated with an H1max of up to 625 mol m23. Xylem tension
followed, as did hydration, both increasing as phase one progressed.
Aechmea aquilega provided the most compelling evidence for CAMdriven hydration. Xylem tension had diminished from its maximum night
value of 20.54 to 20.24 MPa at dawn, dew having formed on foliage
between these two records. However, C3 Vriesea amazonica exhibited a
similar response under the same conditions. Interpretation is further complicated by a second reality: both species possess phytotelmata that storms
probably topped up shortly before the readings were taken (Griffiths et al.
1986). Finally, lower densities of trichomes on the blades compared with
the bases indicate less capacity for hydration by the ® rst compared with the
second route.
Osmotic potentials that peak early in the day should enhance water
balance most for the Type Five species, and under certain circumstances
perhaps prove decisive for survival. Tillandsia paleacea, T. purpurea and T.
werdermannii native to the hyperarid (except in El Niño years) coastal
deserts of Peru seem especially well situated to bene® t from daily ¯ uctuations in p driven by CAM. Heavy nightly mists (`garuas' ) off the Paci® c
Ocean probably insure adequate hydration between May and October. The
rest of the year, dew, which quickly evaporates in the early morning sun,
must suffice.
Conditions elsewhere may grant CAM similar importance and account
for some of that paradoxical anatomy among generally xeromorphic Type
Five bromeliads. Finely dissected shoots and attenuated trichome shields
(Fig. 2.8C) could make contacts with moisture that pass too quickly to
sustain less specialized ¯ ora adequate to support T. tectorum and its kind.
In quite another ecological context, Type One bromeliads with deeperrooted neighbors may bene® t from CAM-dependent p if water drawn up
to shallower soil horizons nightly by hydraulic lift arrives in timely fashion.
Species equipped with large phytotelma, and those that root in continuously moist soil, should bene® t less from the osmotic consequences of
DH1.
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Carbon and water balance
Additional aspects of light relations
We need to revisit the subject of how bromeliads respond to high and low
light to round out this discussion of ecophysiology. Undiminished PPFDs
from sea level to above 4000 m, to the much attenuated ¯ ux that penetrates
to the ¯ oor of dense evergreen forest, sustain numerous Bromeliaceae.
Aspects of leaf and shoot structure, pigments and physiology, and leaf life
span parallel these contrasting energy supplies. Species with the thickest
foliage and most compact rosettes, i.e., those that operate with the highest
leaf area indices (e.g., Hechtia, Dyckia; Fig. 2.2B) typically experience the
highest exposures and quite often also the potentially complicating effects
of drought. Indeed, these plants often grow more vigorously in partial
shade. Overexposed, the more sensitive types become chlorotic, grow feebly
and may not reproduce.
Xeromorphic Bromelia humilis reportedly exists in a chronically photoinhibited state in the sunniest microsites within certain habitats in northern
Venezuela (Medina et al. 1986). Exceptionally ¯ exible Guzmania monostachia, with its much more lightly constructed foliage, demonstrated signi® cant inhibition in Trinidad, but escaped the more serious, longer-term
impairment of the light-harvesting apparatus that drought-stress combined with high exposure can in¯ ict (Maxwell et al. 1992, 1994, 1995). In
fact, this species, more than any other bromeliad, has demonstrated how
plants can reduce photodamage that would diminish carbon gain in environments characterized by shifting PPFD.
Plant features that promote carbon gain at either low or high ¯ uences fall
into two categories: structural (relatively static) and chemical/physiological
(more dynamic). Widely tolerant Spanish moss showed little adjustment by
either route as noted above. Other taxa exhibited expected patterns, sometimes with additional responses peculiar to Bromeliaceae. According to
Dimmitt (1985), Tillandsia caput-medusae from a highly exposed, Sonoran
Desert site bears a denser and more re¯ ective indumentum than a second
set of plants collected from wetter, forested locations. Cultivated side by
side for several years, the sun-adapted stock continued to produce its
better-shielded foliage.
High and low-light phenotypes rather than ecotypes of many more
species stand out at a glance. In addition to a more glabrous surface,
thinner, laxer blades characterize the foliage of specimens acclimated to
shade. Typically broader leaves with shorter, but stiffer more upright,
blades probably enhance drought-tolerance in addition to reducing exposure to direct-beam light by increasing tank capacity relative to shoot
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Additional aspects of light relations
177
volume for the sun-grown phytotelm bromeliad like Tillandsia utriculata
(Fig. 4.23B,C).
Adjustments to PPFD can also involve reorganization of the chloroplast.
Bromelia humilis cultivated under 20± 30 compared with 700± 800 mmol m22
s21 PPFD developed thicker granal stacks in addition to higher concentrations of chlorophyll and exhibited lower light compensation intensities.
However, light response curves proved less sensitive to preconditioning,
especially for those subjects provided supplemental N. Zeaxanthin, a component of the xanthophyll cycle, occurred more abundantly in the foliage
of the high-light plants (Fetene et al. 1990).
Aechmea magdalenae indicated that Bromeliaceae bene® t from the same
mechanism mediated by carotenoids that reduces photo-oxidative damage in
other plants stressed by supersaturating PPFD (Koniger et al. 1995; see also
Skillman and Winter 1997). The size of the xanthophyll-cycle pool (267.2
mmol mol21 chlorophyll) approximated those determined for the 12 C3-type
species assayed in the same understory habitat in Panama. Several-fold
higher ratios of carotenoids to chlorophyll in the foliage of adjacent gapphase and canopy trees indicated weaker capacity to accommodate high
PPFD and likely shade-plant status for this Type Two bromeliad and the cooccurring herbs. However, Aechmea magdalenae alone among the compared
understory species deviated from the usual correlation between Amax and
xanthophyll pool size because of its capacity to ® x CO2 at twofold and higher
rates on a leaf area basis compared with those companion C3 plants.
Zeaxanthin (X) typically accumulates in light-saturated foliage at the
expense of violaxanthin (V) and antheroxanthin in a partially characterized mechanism involving the transthylakoid pH gradient that dissipates
excess excitation energy. Subsequent darkening allows zeaxanthin-epoxidation and organ recovery, although more slowly in Aechmea magdalenae
than violaxanthin-de-epoxidation according to assays conducted on the
same plants examined for Amax. Expoxidation state (EPS) (the % V to X
conversion) indicated the extent to which Koniger et al.' s subjects were
exposed to excess irradiance and could engage the xanthophyll cycle to
avoid photoinhibition. Values of the ratio of variable to maximum ¯ uorescence (Fv/Fm) consistently above 0.84 further indicated no sustained impairment among the A. magdalenae specimens monitored over several sunny
days. Many of their readings followed exposure to prolonged sun ¯ ecks that
constitute the primary source of energy for this understory species.
Consistent with performances recorded elsewhere (e.g., Medina et al.
1977), Guzmania monostachia responded differently on several counts at
different points across steep light gradients (Maxwell et al. 1992, 1994,
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Carbon and water balance
Figure 4.23. Plant responses to water and light. (A) Unidenti® ed Tillandsioideae on
fallen tree illustrating leaf injury resulting from the consequent abrupt change in
exposure to light. (B) Shade-grown Tillandsia utriculata. (C) Tillandsia utriculata at
the same site exposed to stronger light. (D) Tillandsia kurt-horstii on granite
outcrop in Bahia State, Brazil. (E) Tillandsia kurt-horstii illustrating substantial
surface area available to intercept fog water provided by its dissected shoot and
dense indumentum of trichomes with elongated shields. (F) Abaxial leaf surface of
Tillandsia bulbosa (3150). (G) Adaxial leaf surface of Tillandsia bulbosa (3150).
(H) Portion of trichome shield of Tillandsia karwinskyana illustrating its rough
light-re¯ ecting texture (3225). (I) Adaxial leaf surface of Brocchinia micrantha
illustrating the large crystal present in each epidermal cell (3150).
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Additional aspects of light relations
179
1995). Pronounced nocturnal acidi® cation characterized the more light and
drought-stressed plants perched in the lea¯ ess crowns of seasonally deciduous trees, but not so some other, more shaded specimens rooted on nearby
evergreen supports (Fig. 4.8). Foliage also differed by chlorophyll content,
a/b ratio, blade thickness, proportional volumes of chlorenchyma vs. colorless hypodermis, and some revealing physiology (Table 4.6). Darkadapted (10 min) chlorophyll ¯ uorescence and O2 evolution relative to
PPFD provided measures of the photochemical efficiency of photosystem
II and an important response to high light.
Quantum yields routinely diminished through the day as did
Fv/Fm (0.70± 0.42) in fully exposed plants compared with individuals maintained in 40% shade (Fig. 4.24). Recovery for both treatment groups
began after midday as PPFD started to fall, and ® nished by late afternoon, indicating no damage of the type that requires more time to repair
(Long et al. 1994). CAM that persisted in well-hydrated, unscreened subjects, but disappeared in shade, further demonstrated the probable photoprotective function of a mechanism that supplies CO2 to irradiated
mesophyll while stomata are closed. Too little capacitance or impoundment capacity in leaf bases prevails even if coupled to high WUE and a
typically (for Bromeliaceae) modest Amax (Table 4.1) to allow G. monostachia growing in either sun or partial shade to prolong carbon gain through
the dry season.
Maxwell et al. (1992, 1994, 1995) concluded that a dual mechanism helps
maintain the integrity of the photon-harvesting system of G. monostachia.
In addition to light or drought-induced CAM, sufficient photochemical
capacity mediated by the xanthophyll cycle exists to down-regulate photosystem II activity. In one set of runs, CO2 regenerated from malic acid synthesized the previous night provided 24% of the carbon reprocessed via
RuBPc/o; the same source dominated in droughted specimens subjected to
the same high PPFD because net CO2 uptake had diminished 87%.
Paralleling CAM was exceptional (compared with many C3 species) capacity for radiation-less dissipation of excess excitation energy at potentially
incapacitating exposures.
Figure 4.25 illustrates how de-epoxidation of the xanthophyll pool constituents proceeded over the course of two days of contrasting integrated
PPFD during the rainy season in Trinidad. Note that maximum conversion
prevailed at midday, was more pronounced in unshaded specimens, and
reached highest values during the brighter of the two days. Plants moved
between sites featuring 30 or 100% exposure rapidly adjusted chlorophyll
contents (Fig. 4.26), suggesting that acclimatization also involved the loss
and gain of photosynthetic units. After just ® ve days in full sun, chlorophyll
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Carbon and water balance
Figure 4.24. Diurnal variation in photosystem ¯ uorescence characteristics (FV/Fm)
of Guzmania monostachia under natural conditions in Trinidad. (A) Plants growing
in exposed microsites under contrasting daily PAR (s, 43.7 mol photons m22; d,
24.3 mol photons m22). (B) Semiexposed plants under contrasting daily PAR (s,
26.2 mol photons m22; d,14.6 mol photons m22). CAM activity preceding the dark
periods averaged 65 and 48 mol H1 m23 (after Maxwell et al. 1992).
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Additional aspects of light relations
181
Figure 4.25. Zeaxanthin content as a percentage of violaxanthin, antheraxanthin
and xeaxanthin present for Guzmania monostachia at intervals over two contrasting
days during the rainy season. (A) On the ® rst day total PPFD was 17.4 and 7.1 mol
photons m22 day21 for the exposed and semiexposed populations respectively.
Values for the second day (B) were 33.3 (exposed) and 15.7 (semiexposed) mol
photons m22 day21. Open circles indicate plants that received more photons; ® lled
circles are plants that received fewer photons (after Maxwell et al. 1995).
Figure 4.26. Total chlorophyll content over ® ve days following transfer of Guzmania
monostachia plants between 100 and 30% PPFD (after Maxwell et al. 1995).
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Carbon and water balance
content had fallen to less than 50% of its former value. The opposite treatment indicated that this process is reversible.
In summary, seasonal variation in PPFD rapidly promotes two contrasting conditions of the photosynthetic apparatus of Guzmania monostachia
that together enhance carbon gain by long-lived foliage with generally low
inherent capacity to ® x CO2. Sink strength is maintained relatively high
throughout the lower-energy photoperiods of the wet season. More
depressed (down-regulated) photosystem II efficiency coupled with more
active CAM in turn compensates for higher PPFD and greater droughtstress (reduced access to CO2) during the drier months. However, Fig. 4.27
illustrates that exposed plants still gained more carbon during the dry
season if partially shaded, whereas fully and semiexposed plants continuously perform at about the same level.
Additional species with comparable habits and habitats probably operate
like Guzmania monostachia did in situ and Tillandsia deppeana in the laboratory (Adams and Martin 1986a). Epiphytic Vriesea platynema (Type
Four) exhibited suggestive behavior during extreme drought ± essentially
no gas exchange ± less than half way through the dry season on unshaded
perches in a northern Venezuela cloud forest (personal observation).
Shoots were performing C3-type photosynthesis 2± 3 days after their previously dry phytotelma had been re® lled.
A second group of nonphotosynthetic pigments plays a more conspicuous role in the light relations of bromeliads. High exposure routinely
induces extraordinary accumulations of anthocyanins, primarily in the epidermis, presumably to screen solar radiation in the absence of a con¯ uent,
photon-scattering indumentum. Permanently red to maroon or green
foliage differentiates other populations regardless of PPFD (e.g., certain
forms of Tillandsia capitata, T. flabellata). These same pigments provide
additional, better-known services as attractants for pollinators and seed
dispersers. Involvements in mineral nutrition and shade-tolerance constitute additional possibilities worth consideration.
Intricately dissected, ® xed patterns of chlorophyll and anthocyanins displayed by some Type Four species (e.g., Guzmania zahnii, Vriesea fosteriana; Figs. 2.14G, 2.17B, 2.18B) suggest several functions, possibly including
enhancements of photosynthesis. Leaves in some cases feature species-speci® c arrays of chlorophyll-rich zones (shutters) and chlorophyll-poor
regions (windows or fenestrae), sometimes with densely cyanic epidermis
located below each shutter. Nitrogen and phosphorus contents that also
distinguish shutters and windows, like the differences in pigmentation,
diminish as the blade matures (Benzing and Friedman 1981; Fig. 2.14G).
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Additional aspects of light relations
183
Figure 4.27. Diurnal patterns of CO2 assimilation during two days representative of
the rainy and dry seasons. Measurements were performed on the same days for both
exposed (A) and semiexposed (B) plants. Integrated PPFD was 24.9 and 34.9 mol
photons m22 day21 for the rainy and dry-season days respectively (after Maxwell et
al. 1995).
Shutters ® xed CO2 more vigorously on a surface area basis than adjacent
windows until the two shades of green converged with age, after which
uptake occurred at about the same modest rate across the blade.
Species with suggestive coloration warrant closer inspection for the possible presence of an accompanying CO2-concentrating mechanism.
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Carbon and water balance
Paraffin-embedded and sectioned blades revealed no anatomical
differentiation between the chlorophyll-laden and adjacent, paler, mesophyll cells. However, the commissures that often join the more robust parallel veins of these Type Four species routinely traverse only the shutters
(Fig. 2.17B). Further inquiry might reveal the nonuniform distributions of
key enzymes, uneven wall thickenings, and concentrations of plasmodesmata that elsewhere indicate the presence of the gas-tight barrier needed for
C4 photosynthesis. Other taxa (e.g., Ronnbergia; Fig. 2.2F) with similarly
thin foliage exhibit different arrangements of pigments suggesting still
other possibilities.
Fenestration unevenly partitions the photosynthetic machinery in
foliage, but bene® ts from the resulting visual effect may exceed any advantages related to carbon gain. Nutrition is a distinct possibility for plants
reliant on intercepted litter and the biota needed to process it. A fenestrated
leaf can also be larger at reduced cost per unit area than an otherwise comparable concolorous organ by distributing unevenly the same amount of N
and P allocated to energy capture. The resulting larger leaf area would
increase impoundment capacity, hence plant access to moisture and nutrients, without requiring additional investment in these two scarce commodities. Perhaps resource-rich zones distributed in a matrix of less nutritious
tissue also discourage herbivory. Finally, could the nonuniformly pigmented bromeliad leaf deter gravid folivores by appearing already occupied
by larvae?
Because Type Three and Four bromeliads need detritivores to extract
nutrients from litter, selection should promote characteristics that favor
plant attraction of these fauna (Fig. 2.18D). Some circumstantial evidence
supports this possibility as it applies to pigmentation. Horizontal variegations (e.g., Guzmania zahnii; Fig 2.18B) and parallel stripes (e.g., G. lingulata) tend to be most pronounced on the bases of leaves where capacity to
obscure the outlines of tank occupants would be most bene® cial to the
plant. Importance as a signal to remind resident pollinators of a sporadic
food source (as suggested for the red/orange markings on certain
Gesneriaceae) seems less likely because some of the most elaborately
marked bromeliads (e.g., Vriesea fosteriana, V. hieroglyphica, Guzmania
zahnii) ¯ ower at night and disperse wind-carried seeds. The plausible explanation must also account for those occasional species (e.g., Guzmania bismarckii) that produce ornamented foliage as juveniles only to become
concolorous later.
Light harvest might improve with certain ornamentations. Conceivably,
a compact shoot captures more incident PAR if its congested leaves possess
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Additional aspects of light relations
185
Figure 4.28. Transparency to PAR at noon on a clear day of the leaves of three bromeliads distinguished by leaf form and pigmentation (after Benzing and Friedman
1981).
both translucent, relatively inactive and opaque, more vigorously photosynthetic zones. Should windows diminish the quantum yields of the upper
leaves compared with what uniformly green organs could achieve, overall
more incident PPFD might still be utilized by a multilayered shoot. Vriesea
fosteriana and its kind could be especially well suited to harvest sun ¯ ecks
or operate where the upper layers of the shoot become photoinhibited
during the brightest part of the day.
A number of deeply shade-tolerant Type Three and Four bromeliads
(e.g., Aechmea miniata, Lymania smithii, Tillandsia viridiflora, some Vriesea
splendens) display discolorous foliage, which elsewhere purportedly
enhances the utility of shade-light (Lee et al. 1979). Speci® cally, the maroon
to red adaxial epidermis scatters unabsorbed irradiance back up into the
mesophyll. Its co-occurrence with horizontal, monolayered leaf displays
(e.g., Nidularium burchellii, Aechmea fulgens, Vriesea simplex) supports this
contention (Fig. 2.4H).
Densely congested, self-shading shoots characterize many Bromeliaceae
with affinities for high-energy sites (Fig. 1.2G) or, if such a plant is shadetolerant, its foliage is exceptionally thin by family standards (e.g., Tillandsia
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Carbon and water balance
Table 4.11. Arrangements and conditions that should prevail among certain
Bromeliaceae if the interpretations of leaf form and pigmentation detailed
in the text are valid
(1) Leaves bearing a cyanic abaxial epidermis should occur in monolayers and
be relatively long-lived. Leaf structure, composition and physiology should
indicate shade-tolerance.
(2) Bromeliads equipped with fenestrated foliage should require relatively high
exposure. A densely inhabited phytotelmata would be consistent with
protective function.
(3) Leaves with darkly pigmented bases are most likely to characterize shoots
that grow singly rather than form compact clusters. Exceptionally rich tank
faunas would also be signi® cant here.
(4) Species with multilayered shoots habitually encountered in moderate shade
should have translucent, uniformly green, inexpensive (thin, low N/unit area)
foliage.
(5) A densely cyanic adaxial epidermis should characterize specimens exposed
(5) to strong illumination.
leiboldiana, T. complanata). Ecologically ¯ exible Guzmania monostachia
exempli® es what could be a less vulnerable alternative (i.e., more leaves to
lose to predators) with no corresponding trade-off in shade-tolerance.
Three or more of its concolorous but translucent leaves must lie directly
over one another under full sun to deny the lowest organ adequate light to
balance respiration (Benzing and Friedman 1981; Fig. 4.28). Conversely,
little PAR penetrated the foliage of Nidularium burchellii or the similarly
monolayered, but concolorous, leaves of shade-tolerant Catopsis nutans.
Optical enhancements for the capture of shade-light may also involve
light-focusing protuberances on the cells of the adaxial epidermis and thin® lm effects. Suggestively felt-like textures and bluish-green re¯ ectance characterize some deep forest natives like Nidularium burchellii and
shade-grown Bromelia pinguin. Arrangements of mesophyll cells that probably affect light propagation through the interiors of the foliage of shadetolerant bromeliads are described in Chapter 2.
More study is warranted to determine whether certain mechanisms and
ecological correlates prevail. If the logic offered above to explain the purposes of the unusual combinations of pigments, shoot architectures and
leaf texture apply, additional research should con® rm the predictions summarized in Table 4.11. The following chapter completes the coverage of
bromeliad ecophysiology with a discussion of mineral nutrition.
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5
Mineral nutrition
Arid climates and harsh substrates explain why certain Bromeliaceae figure
so prominently in studies of drought-tolerance and CAM. Mineral nutrition has drawn sufficient attention to dispel misconceptions about how and
from where the most specialized species secure essential ions, but certainly
less interest than warranted by the presence of additional, even more exceptional mechanisms.
Contrary to appearances, none of the epiphytes invades host vasculature,
nor does anchorage on bark or rock necessarily impose nutritional stress
given the frequent access these plants have to fertile alternatives like decomposing litter, ant carton and prey (Figs. 5.1–5.3). Nitrogen-fixers and plantfeeding ants assist still other Bromeliaceae (Fig. 5.1). On balance, only a
small fraction of the family, namely certain dry-growing Tillandsioideae
(Fig. 1.3A,C), rely exclusively on precipitation and dry deposition for nutrition, hence deserve the loosely applied label ‘air plant’.
Leaf chemistry indicates that Bromeliaceae accumulate the expected six
macronutrients and nine trace elements in the usual proportions (Table
5.1). Uptake also includes additional ions that support the same and other
functions elsewhere. For example, Si, which in grasses helps deter grazers
and stiffens the Equisetum stem, contributes to the light-reflecting granules
in the epidermis of bromeliads native to sunny exposures (Fig. 4.23I).
CAM types probably utilize Na like other similarly equipped xerophytes.
Now and then, certain required elements concentrate far beyond metabolic
needs; others accumulate for no recognized purpose, although they convey
useful information about environments. Type Five Tillandsioideae exhibit
sufficiently high affinities for certain ‘technological’ metals (e.g., Cr, V, Zn)
and S to serve as inexpensive alternatives to the mechanical devices usually
employed to monitor air quality (Tables 5.2, 5.3).
Much of the literature germane to bromeliad nutrition deals primarily
187
188
Mineral nutrition
Figure 5.1. Schematic diagram illustrating the major sources of mineral nutrients
for Bromeliaceae dependent largely on shoots for uptake (i.e., primarily the epiphytes and lithophytes).
with systematics and comparative morphology. Other reports worth
reviewing for this chapter emphasize air pollution or the fertility of precipitation and rooting media in tropical forests. Data on the growth of certain
ornamental species in hydroponic and aseptic culture mostly appear in horticultural journals and publications for hobbyists. Except for one preliminary survey (Benzing and Renfrow 1974a), no treatment compares
Bromeliaceae among vascular flora relative to sources, needs and tolerances for shortages and oversupplies of mineral ions. Our purpose here is
to update this summary insofar as the still meager database for bromeliads
and extrapolation from other, better-known taxa permit.
External supply and plant demand
Everwet forests that harbor adaptively diverse bromeliad species demonstrate how family members partition nutrient capital in shared ecosystems.
Resolution is uncommonly high for reasons related to plant architecture,
physiology and capacity to grow on the ground and up through the canopy
to its most exposed and hostile perches (e.g., Figs. 5.1, 7.11, 7.12).
External supply and plant demand
189
Figure 5.2. Aspects of Bromeliaceae related to mineral nutrition. (A) Tillandsia utriculata illustrating litter impounded by a phytotelm shoot. (B) Autoradiograph of a
medially sectioned Tillandsia caput-medusae shoot after being fed 45Ca through the
surface of a single leaf base. (C) Small arboreal ant carton in southern Venezuela
supporting seedlings most of which appear to be Codonanthe sp. (Gesneriaceae).
(D) Phytotelmata of Vriesea gigantea containing a drowned insect in Espirito Santo
State, Brazil. (E) Trichome of Brocchinia reducta, no label present (control). (F)
Autoradiograph of Brocchinia reducta trichome exposed to 3H-leucine. (G) Autoradiograph of Brocchinia acuminata trichome exposed to 3H-leucine. (H)
Autoradiograph of Tillandsia streptophylla trichome exposed to 3H-leucine.
190
Mineral nutrition
Figure 5.3. Aspects of Bromeliaceae related to mineral nutrition (continued). (A)
Loose epicuticle on foliage of Catopsis berteroniana. (B) Catopsis berteroniana
growing as an epiphyte in Bahia State, Brazil. (C) Atrophied trichome on the upper
part of the leaf of Brocchinia reducta above the phytotelmata illustrating the fibrillar nature of the loose epicuticle (3250). (D) Brocchinia vestita growing on boggy
soil among carnivorous Heliamphora sp. on Cerro Neblina, Venezuela.
External supply and plant demand
191
Table 5.1. Mineral nutrients present in the foliage of a typical eutroph
(cereal crop) and of Tillandsia paucifolia on nutrient-stressed and betternourished cypress trees in Florida
Generalized
minimum
requirement for
eutrophic vegetation
Nutrient
N
P
K
Ca
Mg
S
Mn
Fe
B
Cl
Cu
Zn
Mo
% dry weight
ppm
1.50
0.10
1.00
0.50
0.20
0.10
Concentration in
T. paucifolia
growing on
nutrient-stressed
cypress
% dry weight
ppm
0.36
0.072
0.33
0.66
0.17
0.05
50
100
20
100
6
20
0.10
Concentration in
T. paucifolia
growing on
relatively vigorous
cypress
% dry weight ppm
0.35
0.085
0.54
0.98
0.23
0.097
27.5
154.8
15.2
—
9.2
35.5
1.43
22.5
195.8
18.3
—
10.0
41.8
1.60
Source: After Benzing (1990).
Substrates, degrees of dependence on roots vs. shoots for ion absorption,
and engagements with nutrition-enhancing mutualists often differentiate
bromeliads that share the same kinds of microsites. Appreciation of this
variety requires familiarity with phenomena that operate at the level of the
hosting ecosystems, to the individual plant, and on down to its subcellular
components.
A modest literature devoted to plant-feeding ants, diazotrophic
microbes, impounded litter and canopy leachates describes the sources of
nutrients available to specific kinds of bromeliads. These reports also indicate the existence of numerous nutritional modes (Table 5.4). Other publications describe the uptake of certain solutes, particularly the absorptive
qualities of the foliar trichome. Two concepts never mentioned in any of
these treatments allow more fundamental comparisons of bromeliads, viz.
nutritional sufficiency, the state of being adequately nourished, and
mineral-use efficiency (MUE), a metric that expresses plant performance
relative to the deployment of acquired nutrients. Considerations on both
counts enhance prospectives for this overview.
Table 5.2. Concentrations of metals (ppm) in the shoots of Tillandsia usneoides collected in the Big Thicket National
Preserve in southeastern Texas. Data represent contents of five collections. An asterisk indicates concentrations in ash.
Values for the other elements are based on dry weight
Sample
1
2
3
4
5
Ash (% dry weight)
Ag*
Cd
Cr
Cu*
Mg
Mn*
Na
Ni
Pb*
V*
Zn
Zr*
3.59
4.03
3.71
3.48
6.04
2.0
5.0
,1.0
,1.0
,1.0
0.32
0.22
0.23
0.24
0.23
2.27
0.69
0.97
1.08
1.41
150
70
100
70
50
1713
2180
1293
1526
2730
5000
7000
7000
5000
3000
3617
1433
511.3
321.0
1460
3.97
2.70
2.72
1.60
2.50
700
300
300
700
300
150
30
70
30
70
68.54
26.40
23.17
36.99
30.59
70
70
70
70
200
Source: After Benzing (1989).
Table 5.3. Mineral uptake efficiencies of Tillandsia paucifolia for 11 elements expressed as percentages of initial levels.
Whole plants were immersed in aerated treatment solutions for 0.5 h per day
Treatment series 2:
Micronutrients at 5 31028 M in all runs,
macronutrients at five concentrations
Treatment series 1: All elements
equimolar
Element and initial
concentration in shoots
(mg kg21 dry weight)
60 days
120 days
60 days for all runs
1025 M 1026 M
1027 M 53 1028 M
33 1024 M 83 1025 M 2 31025 M 1 3 1025 M 5 31026 M
N (4600)
P (680)
K (4000)
Ca (6800)
Mg (2200)
N/C
1132
N/C
N/C
N/C
N/C
129
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
136
N/C
127
151
241
118
N/C
186
115
134
115
119
174
N/C
113
113
N/C
N/C
N/C
113
N/C
N/C
N/C
N/C
115
N/C
N/C
N/C
Mn (32.5)
Fe (124)
B (13.3)
Cu (16.2)
Zn (36.8)
Mo (1.40)
1454
1218
N/C
1235
1405
1341
287
121
N/C
707
372
136
267
143
138
663
295
N/C
324
N/C
125
453
322
N/C
N/C
N/C
135
160
200
123
162
N/C
132
193
211
116
196
N/C
N/C
241
179
N/C
168
N/C
113
256
169
N/C
210
N/C
120
235
176
N/C
Source: After Benzing and Renfrow (1980).
Note: N/C, final level less than 110% of initial concentration.
194
Mineral nutrition
Table 5.4. The nutritional modes of Bromeliaceae
Type
Occurrence in family
Remarks
(1) Root-dependent
terrestrial
Most Pitcairnioideae,
many Bromelioideae,
those few
Tillandsioideae with
well-developed root
systems
Shoot contributes little
to nutrient uptake, root
system well developed
A few Brocchinia species
and many Bromelioideae
and Tillandsioideae
Detritivores and
saprophytes process litter
impounded in
phytotelmata for plant
use
Modifications present to
trap and process prey are
relatively unspecialized
Aerobic N2-fixers active
in phytotelmata
Several tubular species
likely candidates
(e.g., Billbergia porteana)
(2) Tank-based
(A) Animal-assisted
saprophyte
(B) Carnivore
(C) Diazotrophassisted
(D) Vertebrateassisted
(3) Myrmecotrophs
(A) Ant-house
(B) Ant-nest garden
(4)
Atmospherics
Two Brocchinia species
and Catopsis
berteroniana
Undetermined number
of phytotelm species
Undetermined number
of phytotelm species
Brocchinia acuminata,
many Bromelioideae like
Aechmea bracteata,
unknown number of
bulb-forming
Tillandsioideae and
additional phytotelm
species with dry leaf
axils
Mostly Bromelioideae
(e.g., Aechmea,
Neoregelia)
Tillandsioideae
exclusively
Importance to plant
nutrition largely
unproven
Ant-dispersed and
routinely rooted in ant
cartons
Dense indumentum of
absorbing hairs extracts
nutritive ions from
passing fluids. Substrates
serve primarily for
anchorage
External supply and plant demand
195
Concentrations of key elements in some reference organ, usually a leaf
of a certain age or location on the plant, indicate enough about nutritional
status to formulate fertilizer regimens for many crops. Benzing and
Renfrow (1971a) and Benzing and Davidson (1979) surveyed Tillandsia
paucifolia on this basis to investigate the nutritional sufficiency of an epiphytic bromeliad relative to its hosts in southern Florida. Specifically, leaf
composition was compared among the epiphytes and these values in turn
with those obtained from the foliage of the supporting trees (Figs. 7.8, 7.9).
Trends were parallel, i.e., stressed trees supported the most deficient bromeliads. Comparisons involving two or more species of Bromeliaceae or
any other flora present a greater challenge.
Nutrition peculiar to specific patterns of natural history (e.g., that
typical of the representative annual weed vs. a perennial herb or tree) influences which concentrations of what key elements represent nutritional
sufficiency for certain flora. Requirements in each case parallel important
nutrient-related performances like Amax and fecundity. A bromeliad
equipped to draw on a nutrient-enriched phytotelmata or a relative that
instead roots in fertile soil must accumulate the relatively high concentrations of N and P required to achieve the requisite vigorous photosynthesis
to compete with co-occurring vegetation drawing on the same abundant
resources. The more stress-tolerant, Type Five relative obliged by architecture and impoverished substrates to subsist on scarcer, transitory supplies,
primarily precipitation and canopy washes, operates with lower demands
(Table 5.5; Fig. 5.1).
Biomass produced per unit of incorporated nutrient, a number that
quantifies MUE, also parallels adaptation, and reflects growing conditions experienced in situ by tested subjects. Energy returns on investments
of the elements whose supplies limit growth to the greatest degree vary
on two time scales and accordingly, yield two values for MUE.
Instantaneous mineral-use efficiency, essentially the maximum output
(Amax) possible per unit of invested (in foliage) N or P, expresses shortterm return, and by this measure the typical phytotelm bromeliad substantially outperforms its Type Five relatives. Bromeliads probably assort
differently on the basis of lifetime (leaf life span) yields relative to investments of key nutrients.
Field and Mooney (1986) proposed a more precise coefficient to compare
plants using photosynthate accrued from investments of one nutrient in
particular. Their index, known as potential photosynthetic nitrogen-use
efficiency (PPNUE), recognizes the tight correspondence between the N
allocated for the construction of energy-harvesting organs and Amax.
196
Mineral nutrition
Table 5.5. Mineral elements in leaf blades (% dry weight) representing the
five ecological types in Bromeliaceae
Species
Ecological type/
location
Ca
Bromelia karatas
Type II/Jamaica 1.19
Pitcairnia bromeliifolia Type I/Jamaica 1.06
Catopsis floribunda
Type IV/Jamaica 1.15
Aechmea nudicaulis
Type III/Jamaica 0.38
Guzmania lingulata
Type IV/Trinidad 0.44
Tillandsia balbisiana
Type V/ Florida 0.83
Tillandsia usneoides
Type V/ Florida 0.67
K
Mg
2.48
1.02
1.59
1.94
1.59
0.34
0.50
0.14
0.14
0.18
0.20
0.25
0.14
0.29
N
Na
P
0.67 0.064 0.068
1.37 0.036 0.084
1.36 0.32 0.091
0.57 0.18 0.057
0.88 0.19 0.063
0.36 0.41 0.035
0.82 0.55 0.012
Source: After Benzing and Renfrow (1974a); Table 4.2.
Vegetation constrained by N-poor foliage – species with low critical concentrations of this key nutrient (the concentration needed to realize growth
potential, i.e., to achieve Amax) – gain carbon slowly, and thus express inherently poor instantaneous PPNUE. In essence, leaf longevity and Amax vary
inversely because investments in green tissue must be amortized via photosynthesis plus a marginal gain to support growth, reproduction and plant
maintenance. Slow payback and additional time for profit mandate comparably durable biomass made relatively expensive by obligatory investments in defensive chemistry, strengthening polymers, and other
compounds beyond the pigments, enzymes and additional plant constituents required to harvest photons.
Similar leaf characteristics (e.g., high durability, high cost in carbon/unit
leaf surface area) equip plants for drought and infertile substrates, and
both conditions also constrain Amax. Therefore, PPNUE should be modest
for most Bromeliaceae, and foliage relatively long-lived and well defended.
Preliminary data obtained with a portable photosynthesis analyzer in wet
pre-montane forest at Rio Palenque, Ecuador and in a northern
Venezuelan cloud forest support one of these suppositions. Ecuadorian
Guzmania monostachia fell closer to findings for woody evergreens than
deciduous trees, shrubs and annuals on the basis of Amax as a function of
N content on a leaf area basis (Field and Mooney 1986).
Table 5.6 provides values for two epiphytic ferns, co-occurring phytotelm
Vriesea platynema, and foliage from the supporting guava tree at the just
mentioned site in northern Venezuela. However, both sets of numbers
would indicate more about local growing conditions and plant access to
Nutritional peculiarities
197
nutrients and water if referenced on the longer of the two time scales – if
expressed as integrated rather than instantaneous MUE. Foliage that generates photosynthate slowly over an extended life span signals scarce
resources. Shorter-lived, less expensive (in carbon) leaves capable of fixing
CO2 faster on a leaf area basis represent the superior strategy in more
equable habitats, which as already indicated tend to favor the superior competitor.
Nutritional peculiarities
Plants reflect the fertility of their habitats in additional ways. Eutrophic
types, those species endemic to nutrient-rich substrates, exhibit critical concentrations of N and P that fall at the upper end for vegetation generally.
High shoot/root ratios, short life cycles as well as foliage that turns over
rapidly further identify these taxa. Moreover, fecundity is exceptionally
elastic: it tracks available nutrients as illustrated by annual weeds and their
derived cultigens, the consummate eutrophs. Nutritionally deprived specimens grow poorly and, faced with extreme scarcity, fail to reproduce.
Sufficiently fertilized, they do quite the opposite.
Another response favors plant life on habitually deficient media. Dilute
supplies of nutrients never seriously stress the inherently slow-growing oligotroph, even though concentrations of key elements may fall well below
levels in the comparable tissues of the better-supplied members of the same
stock (e.g., Tillandsia paucifolia; Table 5.1). Shoot/root ratios tend to be
low, foliage evergreen, and the life cycle of the plant protracted.
Salt-tolerators
Additional peculiarities related to mineral nutrition and ion balance adapt
many land plants for still other chemical environments. Sensitivities to
heavy metals (Tables 5.2, 5.3) and NaCl vary among taxa and may distinguish populations within species. Diverse Bromeliaceae occupy saline habitats, some as narrow endemics like Pitcairnia halophila on rock outcrops
just above high tide in the southern portion of Costa Rica’s Puntarenas
Province (Grant 1994a). Pitcairnia integrifolia occurs under similar conditions in Trinidad. However, low osmotic pressures (,0.91 MPa) in foliage
indicate either salt-exclusion or avoidance of saline media (Lüttge et al.
1986a).
Certain members of Bromelioideae and Tillandsioideae also inhabit
maritime sites, and possess architecture that obliges contact with salt.
198
Mineral nutrition
Tubular Aechmea nudicaulis, which ranges from Mexico southward,
approaches the intertidal zone in southeastern Brazil where it, along with
the many other bromeliads of the restinga formation (Fig. 7.13C), often
grows close enough to the surf to regularly intercept salt spray. Bromelia
humilis extends from several hundred meters above on to low-lying, saltladen soils along the south Caribbean coast, also without measurable
effects on tissue chemistry, as described below.
Several sets of data indicate tolerance and perhaps even benefit from
access to sea salt among Type Five Tillandsioideae (Fig. 1.2H). Molar concentrations of Na exceeded those of K in the shoots of Tillandsia flexuosa
native to Venezuela’s northern coast (Griffiths et al. 1989). Leaves of
Tillandsia paucifolia growing on red mangrove (Rhizophora mangle) in
south Florida contained Na at up to several percent of dry weight (Benzing
and Renfrow 1971a; Benzing and Davidson 1979). Additional populations
farther inland bore lower salt burdens, but K/Na ratios remained above
unity. Surveys of additional Type Five Tillandsia (e.g., Shacklette and
Connor 1973) further suggest benefits from Na where scarce supplies of K
(e.g., telephone wires, treetops; Fig. 1.3A) or poor root development favor
substitutions.
Gómez and Winkler (1991) used AgNO3 and sectioned leaves to determine whether members of a suite of wide-ranging Mesoamerican bromeliads (Tillandsia dasyliriifolia, T. caput-medusae, T. baileyi, T. festucoides, T.
schiedeana, Catopsis sp. and Aechmea sp.) growing on red mangrove accumulate salt at a site along the Pacific coast of Guatemala. Plants were generally more robust and their foliage thicker compared with relatives in other
kinds of nearby forest. Staining indicated that Tillandsia dasyliriifolia and
the unspecified Catopsis contained the most Cl2. Highest concentrations
occurred in the mesophyll, specifically in cells surrounding the vasculature
and those located below the trichomes.
Co-occurring Bromeliaceae and Orchidaceae sometimes develop
different chemical profiles in the same tree crowns, perhaps in part owing
to their distinct body plans. Encyclia tampensis (Orchidaceae) foliage contained substantially more K than Na compared with Tillandsia paucifolia
(Benzing and Renfrow 1974b; Benzing 1978b). Other bromeliads operate
more like the orchid. Foliage that resisted penetration by 36NaCl in one
experiment helps Pitcairnia integrifolia remain largely unaffected by sea
water in coastal habitats in Trinidad (Lüttge et al. 1986a). Correlations
between leaf chemistry and relative dependence on roots vs. shoots for
uptake underscores the need to better understand trichome function to discover how high Na status develops.
Nutrients in the forest canopy
199
Oligotrophs and other extreme strategists
Among the most oligotrophic of the bromeliads judging by substrates,
plant structure and growth rates are the pulse-supplied forms, those species
without phytotelmata, ant nests or soil roots to provide more continuous
streams of essential ions (Fig. 1.3A,C). Aerosols, precipitation and canopy
washes suffice instead. In fact, nutrient requirements for Type Five
Tillandsia may rank among the most modest of all for vascular flora.
Predictably, these plants grow slowly and produce durable foliage that
sometimes contains exceptionally low concentrations of N, P and K compared with phytotelm and soil-rooted species (Tables 5.1, 5.5). Because
drought and habitually scarce supplies of key elements promote similar leaf
morphology and oblige low vigor, Brocchinia species native to the moist,
base-poor savanna habitats of the Guayanan highlands of northern South
America probably demonstrate bromeliad oligotrophy in its purest form.
Bromeliaceae illustrate several additional nutritional modes. Among the
family’s membership are several carnivores, at least 50 ant-fed species of
two types, and another, much larger and more important group labeled the
animal-assisted saprophytes (Table 5.4). Before moving on to describe these
relatively novel arrangements, we need some information about the fertility of several kinds of habitats. Supplies of nutrients available to
Bromeliaceae more or less fall into two categories distinguished by whether
or not mutualists are involved. Few records beyond those for cultivated
pineapple describe the media that support terrestrial Bromeliaceae, but
given the diverse kinds of sites these plants occupy, species dependent on
absorptive roots probably experience soils of widely varying qualities.
Enough is known about sources for the epiphytes to warrant a brief survey.
Nutrients in the forest canopy
Nutrient stocks accessible to arboreal flora originate from the atmosphere
and the soil, in the second case following movement up the transpiration
streams of supporting trees. Availability to resident Bromeliaceae depends
largely on the capacity of these plants – which varies among species – to
utilize leachates, litter, certain animal products or prey. Opportunities for
the individual bromeliad may be limited, but no other family exceeds this
one for nutritional variety – either for the diversity of the sources utilized
or for the number and novelty of the devices employed to tap them. Most
of this variety is expressed among the epiphytes.
Table 5.6. Net photosynthesis and N and P present in the leaves of five epiphytes growing on the trunk of a single guava tree
and the foliage of that phorophyte at Rancho Grande, Venezuela, 7–10 January 1988
Net photosynthesis (mmol CO2 m22 s21)
Species and photosynthetic pathway
Psidium sp. (C3)
Vriesea platynema (C3)
Stelis sp. a (CAM)
Peperomia sp. a (?)
Microgramma lycopodioides (C3) (drought-deciduous fern)
Pleopeltis astrolepis (C3) (a resurrection fern)
Unirrigated After 1 day After 2 days After 3 days
27.369.6
0
0
0
3.70 61.7
0
29.9612.5
—
0
10.0262.60
0
0
0
0
—
—
7.15 60.82
—
—
6.96 62.11
0
0
—
6.5360.98
Source: After Benzing (1990). a Gas exchange monitored day and night.
Note: The dry mat of suspended humus supporting these plants was soaked with water after the first measurements.
Leaf N
(g m22)
N
P
0.64
0.26
—
—
0.142
0.104
0.079
0.027
—
—
0.0214
0.0056
Nutrients in the forest canopy
201
Figure 5.4. Wet and dry-season inputs from the atmosphere for five elements in a
cloud forest in northern Costa Rica (after Nadkarni 1984).
Inputs from the atmosphere
Nutrients from the atmosphere arrive as dry deposition, including vapor,
and in solution. Vapor provides S and N, in the second case mostly as NH3,
while NH41 and NO32 predominate in precipitation. Magnesium, K and P,
among the other elements required in relatively large quantities by plants,
also arrive primarily dissolved in rain. Still others, including certain potentially troublesome metals, more often concentrate in dry deposition. Rates
of delivery vary many fold depending on the site, with annual inputs of
decisive nutrients, for example P, ranging from 0.07 to 1.70 kg ha21 year21
in just two studies (Nadkarni 1984; Newman 1995; Fig. 5.4).
Certain elements exceed others in the particulates that lodge on plants,
and chemical signatures often indicate specific origins, for instance whether
derived from land, sea or biota (e.g., Clarkson et al. 1986). Composition
varied among the shoots of Tillandsia usneoides sampled across the southeastern United States (Shacklette and Connor 1973; Connor and
Shacklette 1984). Shifting proportions of Al, Ba, Ca, Ga, Fe, Sn and Y
indicated multiple, site-specific sources. Concentrations of technological
metals also changed with the sample, but differently as described below.
Should the indumentum contribute to the remarkable scavenging capacities of the ‘atmospheric’ bromeliads by enhancing capacity to trap
202
Mineral nutrition
nutrient-laden aerosols, then another service can be added to the list of
benefits provided by the bromeliad trichome (Table 2.1).
Precipitation contains all of the plant nutrients in at least minute
amounts to concentrations exceeding those in many soil solutions (Table
5.7). Local and regional geology (e.g., desert, proximity to ocean), type of
vehicle (e.g., rain, cloud water), season, and a variety of other natural and
anthropogenic factors determine the compositions of these solutions.
Global change is also an increasingly important player. Mounting inputs
reflect changing land use, especially the burning of biomass and the consumption of fossil fuels (Moffat 1998). Impacts on oligotrophic flora and
many Bromeliaceae and other plants dependent on foliage and the atmosphere to acquire mineral nutrients seem likely whether burdens of reactive
N continue to increase or level off. Acidified precipitation could exacerbate
the problem given the weakly buffered nature of the rooting media and phytotelmata of many of the epiphytes. A rising CO2 level further challenges
attempts to predict plant responses to elevated delivery of H1, P and N.
Inputs from the atmosphere relative to other sources vary in importance
with the nutrient and the affected flora. Sulfur deposition often exceeds
local requirements, whereas inputs of N, P and K fall well short of the
needs of all but the primarily rain-fed communities like raised ombrotrophic Sphagnum bogs and heathlands (Clarkson et al. 1986). Epiphytes
in forests over impoverished soils can substantially influence system-wide
nutritional dynamics (Chapter 7). Several surveys (e.g., Nadkarni 1984;
Clark et al. 1998; Table 5.11) illustrate how much of the stocks of several
key elements reside in suspended phytomass. Table 5.8 demonstrates why
phytotelm bromeliads are so well suited to subsist on impounded litter, and
at high densities in infertile ecosystems collectively immobilize significant
quantities of local nutrient capital.
Data collected by Nadkarni (1984, 1986) in lower montane, Costa Rican
rainforest are useful for this discussion because the habitat supported considerable numbers of Bromeliaceae, and she specified the times of delivery
and the vehicles. Precipitation tended to be more nutritive during the dry (N
0.28 ppm, P 0.95 ppm) compared with the wet (N 0.05 ppm, P 0.11 ppm)
months. However, the greater volume of wet-season rainfall considerably
diminished dry-season influences on total inputs (Fig. 5.4), although not
necessarily the welfare of impacted Bromeliaceae if uptake parallels concentrations in sources. Nitrate far exceeded NH41 as a nitrogen supply for the
local epiphytes. Clouds and mist (occult precipitation) also delivered substantial inputs, in part because concentrations were several fold higher than
those in rainfall (e.g., Clarkson et al. 1986; Coxson and Nadkarni 1995).
Table 5.7. Chemical composition (ppm) of rainwater, throughfall and stem flow in the forest canopies of central Amazonia,
eastern Panama, Haiti and South Florida
Central Amazoniaa
Eastern Panamab
Haitib
Stem flow
Nutrient
Rainwater
Throughfall
Stem flow
Rainwater
Throughfall
Na
K
Ca
Mg
Mn
N (NH41)
N (NO32)
N (NO22)
N (total)
P (PO432)
S
Fe
Zn
0.12
0.10
0.07
0.02
0.27
1.24
0.25
0.19
2.11
6.58
1.72
0.97
0.02–1.4
0.4–3.6
0.04–0.64
0.003–0.68
2.4–5.6
2.0–2.8
0.44–0.80
0.010–0.036
3.00
1.00
4.30
trace
1.23
0.17
0.11
0.002
0.41
0.003
0.05
0.56
0.01
9.20
0.27
0.02
0.151
0.095
0.033–0.075
0.024–0.068
0.053–0.340
0.017–0.079
0.036–0.416
0.029–0.062
0.15
0.17
0.41
Source: aFrom Junk and Furch (1985). bFrom Benzing and Renfrow (1980).
South
Floridab
Stem flow
0.25–1.30
3.04–9.60
0.52–0.61
0.40–0.76
0.017
Mineral nutrition
204
Table 5.8. Distribution of nutritive elements in the shoots and phytotelmata
of Guzmania monostachia specimens growing in a swamp forest in south
Florida. Values are averages for two specimens
Mineral content (mg)
Element
Vegetative
Mature
organs
infructescence
N
P
K
Ca
Mg
Na
Mn
Fe
B
Cu
Zn
151.2
18.8
399.5
189.6
116.3
48.4
1.02
1.41
0.27
0.035
0.042
50.6
10.7
90.4
21.1
18.3
2.56
0.24
0.37
0.068
0.017
0.16
Phytotelmata
197.8
11.3
17.0
288.0
24.0
4.4
0.45
2.91
0.55
0.031
0.28
Percentage of total
plant pool replaceable
from foliar
impoundments
98.0
38.3
3.5
136.7
17.8
8.6
35.7
163.5
162.7
59.6
271.8
Source: After Benzing and Renfrow (1974a).
Bromeliaceae experience shared habitats differently depending on the
mix of species present. For example, had the two bromeliads illustrated in
Fig. 5.1 resided in the dry Honduran forest (1200 mm year21) Kellman et
al. (1982) examined, they would have encountered half or more of the
annual inputs of important nutrients arriving via precipitation during as
few as 1–10 rainy days. Contact with nutrients would have been brief for
the Type Five bromeliad (assuming it harbored no plant-feeding ants) compared with its tank-equipped relative, which maintains more continuous
contact with sources represented by impounded litter and possibly
nitrogen-fixers.
A variety of phenomena in addition to storm frequency and duration
affect the timing of the delivery of nutrients to arboreal Bromeliaceae. Ions
scrubbed from the atmosphere during a storm enrich early more than laterarriving precipitation. Subsequent contact with coating and exchange sites
within the canopy further enrichs or depletes solutions after rain becomes
throughfall and stem flow. Concentrations of Ca21 and K1 usually increase
at this stage, while the abundances of others change less predictably (Table
5.7).
Nutrients in the forest canopy
205
Table 5.9. Mineral element content in stem flow and the outer bark and
foliage of dwarfed and relatively vigorous Taxodium distichum hosting
Encyclia tampensis and Tillandsia paucifolia in south Florida
Element (mg 5 g21 dry weight)
Status of host
(1) Bark
Water extract
N
P
K
Ca
Mg Na
Dwarfed
Vigorous
0.22 0.004 0.11
0.38 0.004 0.37
HCl extract (0.01 N)
Dwarfed
Vigorous
0.13 0.014 0.14 33.9 0.33 0.24
0.34 0.096 0.74 107.0 1.11 0.20
Nutrients remaining
after both extractions
(bark wet-digested)
Dwarfed
Vigorous
5.31 0.063 0.07
6.46 0.251 0.33
(2) Foliage
Dwarfed
Vigorous
(3) Stem flowa
Dwarfed
Vigorous
53.0
72.0
2.80 21.5
6.50 33.5
0.28 0.02 0.24
6.22 0.08 0.13
42.7 0.12 0.03
47.6 0.53 0.02
103.5 4.20 1.95
165.5 7.50 3.75
0.76 0.017 0.25
0.40 0.017 1.30
3.04 0.52 0.60
9.60 0.61 0.64
Source: After Benzing and Renfrow (1974b).
Note: aStem flow mineral element content is expressed in ppm.
Bark, suspended soils, and other aerial media
So far, discussion has focused on nutrients in aerosols, precipitation and
canopy washes, and, for the phytotelm bromeliad, on inputs from symbiotic diazotrophs and litter impounded in phytotelmata. Except for the
wholly shoot-reliant species, the properties of ant carton and other animal
products, bark, suspended mats of humus, and rotting wood that contact
roots also influence the nutritional welfare of epiphytic Bromeliaceae.
Several publications report the fertility of canopy substrates for these
plants.
Dilute HCl stripped only modest quantities of N, P and K (Table 5.9)
from the outer bark of dwarfed cypress trees that supported exceptionally
nutrient-deficient Tillandsia paucifolia in Florida (Chapter 7; Benzing and
Renfrow 1974b; Table 5.1). Preparations from more vigorous trees hosting
relatively robust specimens yielded K and P at 5–7-fold and N at about
threefold higher concentrations. Substrates for epiphytic aroids, bromeliads, gesneriads and ferns in an abandoned Theobroma cacao plantation at
Rio Palenque, Ecuador also differed in important chemical properties
(Table 5.10). Compared with subjacent soil, all five types of media tested
Table 5.10. Chemical characteristics of mineral soil and suspended media (one sample each) in wet forest at
Rio Palenque, Ecuador
Description of material
pH
% base
saturation
Outer bark of large Theobroma
branches with associated debris
and nonvascular plants
Outer bark of Theobroma twigs
Rotten wood of Theobroma
Fern root ball
Carton of ant-nest garden
Earth soil
6.2
6.7
7.1
5.2
6.3
6.3
79.1
85.8
90.2
56.4
78.4
55.3
Source: After Benzing (1990).
Cation
exchange
capacity
123.5
137.4
163.3
135.1
115.3
31.1
meq 100 g21
K
Ca
20.0 49.7
18.7 67.4
4.6 112.3
7.5 57.3
20.1 56.2
0.5 14.0
ppm
Mg
H
Na
N
P
K
25.5
31.5
30.1
11.1
12.2
2.5
25.8
19.5
16.0
58.9
24.9
13.9
2.6
0.3
0.3
0.4
1.9
0.2
3.0
2.2
1.5
1.8
2.9
0.3
0.34
0.22
0.09
0.10
0.39
—
0.67
0.71
0.18
0.25
0.79
—
Nutrients in the forest canopy
207
Table 5.11. Mineral nutrient capital in the crowns of two dwarfed Quercus
virginiana hosts growing in a coastal strand community in south Florida:
percentage of total found in the epiphyte load
N
P
K
Ca
Mg
Na
Mn
Fe
B
Cu
Zn
Mo
Specimen 1 35.4 53.4 50.2 41.4 76.4 60.8 44.0 77.1 36.2 55.2 62.4 62.1
Specimen 2 35.9 33.9 57.2 43.4 43.9 69.9 55.8 28.6 39.0 49.4 60.5 50.2
Source: After Benzing and Seemann (1978).
exhibited superior cation exchange capacity, higher base saturation values,
and a preponderance of N over P and K. Neutral to moderately acid pH
prevailed, but may not be typical: suspended humus collected in pluvial
forest in northwestern Ecuador produced readings down to 3.8 (Bermudes
and Benzing 1989).
Lesica and Antibus (1991) discovered that the epiphytes, including many
Bromeliaceae, in humid lowland Costa Rican forest at La Selva root in substrates at least as fertile as those available to co-occurring terrestrial flora.
However, the much larger volumes of soil on the ground probably assure
greater total supplies for plants. Uneven rates of mineralization (higher
below; e.g., Vance and Nadkarni 1990) further distinguish rooting media in
the same forests, as does soil reaction. Whether this chemical mosaic contributes significantly, as Lesica and Antibus suggested, to the high diversity
of local epiphytes, especially relatively root-dependent Bromeliaceae,
remains to be seen.
More extensive sampling than at either Rio Palenque or La Selva allowed
Nadkarni (1984) to determine that humic soils (histosols) suspended within
the canopy of a lower montane rainforest in Costa Rica contained large
fractions of the total on-site pools of several essential ions. A similar
pattern prevailed in upper montane cloud forest in Colombia (Hofstede et
al. 1993) and in biomass largely attributable to Tillandsia recurvata in the
crowns of dwarfed Quercus virginiana in a coastal strand community in
southwest Florida (Benzing and Seemann 1978; Table 5.11). Nadkarni also
examined key processes that influence the mineralization of suspended
humus, specifically the transformation of complexed N into plant-usable
forms.
Less nitrification occurred in suspended compared with forest-floor
litter, although microbial biomass was about the same in both compartments at Nadkarni’s Costa Rican site. Cellulose discs embedded in canopy
debris lost less weight than those worked into litter on the ground at the
208
Mineral nutrition
same location (Nadkarni 1986; Vance and Nadkarni 1990). Terrestrial
samples weighed 23–45% less after eight weeks, while those incubated
within suspended humus over the same interval changed little. Epiphytederived soils also harbored fewer detritivores, had lower water but higher
fiber content, had a higher carbon/nitrogen ratio, and seemed to be dissipating polyphenols more slowly than phytomass decomposing on the
ground. Densities of mites, adult beetles, holometabolous insect larvae,
Collembola, amphipods and isopods averaged 2.6 times higher in earth
compared with canopy soils. Only ants occurred at about equal densities in
both media. Nadkarni and Matelson (1991) further concluded that the histosols suspended there largely develop in place. Except for the modest
amounts of material intercepted in the shoots of phytotelm bromeliads,
shed plant parts mostly fall to the ground.
Contrary to Nadkarni’s findings for mats of epiphytes and suspended
humus in Costa Rica, Paoletti et al. (1991) documented conditions favorable for rapid litter breakdown in the canopy of cloud forest at two sites in
northern Venezuela. Up to fivefold greater detritivore densities (number of
animals per unit volume of impounded humus) occurred in the shoots of
resident phytotelm Bromeliaceae as on the forest floor (Fig. 8.15).
Moreover, dried Psidium foliage placed in nylon mesh bags and incubated
in the leaf axils of these epiphytes on average weighed 21–27% less after
three months – about the same rate of loss recorded for samples buried in
earth soil under the host trees. Additional surveys could help determine
whether the soil fauna observed in phytotelm bromeliads also attack debris
elsewhere in the canopy.
Identifying the sources of nitrogen
Processes similar to those that fractionate the stable isotopes of carbon and
hydrogen during photosynthesis also provide opportunity to track another
important element through ecosystems. According to Schulze et al. (1991),
fractionation during transfers between trophic levels enriches the 15N
content of biomass 3–5‰. Midgiey and Stock (1998) took advantage of
this phenomenon to demonstrate carnivory in Roridula gorgonias, and the
same approach could help determine inputs from prey and ants to phytotelm and myrmecophytic bromeliads. Stewart et al. (1995) concluded from
the isotopic makeup of the N distributed among forest flora at two sites in
Brazil that the assayed epiphytes more than the supporting trees rely on the
atmosphere, perhaps partly via nitrogen fixation, for this key nutrient.
Specifically, heavy N was relatively depleted in most of the assayed epiphy-
Mechanisms
209
tes (cacti, ferns, orchids and Peperomia in addition to the bromeliads) relative to foliage born by the phorophytes.
Bromeliads yielded the lowest 15N values (x̄ 525.2 and 24.9‰), even
lower than those of the other assayed epiphytes (all means5.23.0‰),
while the trees exhibited positive readings (x̄ 52.6 and 3.1‰), as expected
for plants rooted in soil, a typically more 15N-enriched medium.
Conversely, the major N sources in the atmosphere (fixed N2, NO32 and
NH41) contain proportionally less 15N (,23.0‰). Unfortunately, Stewart
et al. failed to identify the bromeliads to species so their claim that plant
habit (architecture) had no effect on 15N/14N ratios in biomass (i.e., utilization of specific N sources) cannot be confirmed for this family. Type Five
species should yield lower values than those equipped with phytotelmata,
unless little of the N present in tree litter makes its way into the impounding shoot. Clearly, Stewart et al.’s and Midgiey and Stock’s approach holds
great promise for more penetrating studies of bromeliad nutrition.
Mechanisms
Assistance from microbes
Certain fungi and the nitrogen-fixers promote plant nutrition in different
ways depending on the types of participants and certain other variables.
Diazotrophs convert dinitrogen to forms available to themselves and eventually other biota. Leaky exchanges characterize paired, free-living organisms compared with the traffic between partners in the most intimate,
coevolved mutualisms (e.g., the legume–Rhizobium association).
Mycorrhizal fungi assist hosting flora by promoting the sorption of P and
several other mineral nutrients and sometimes water.
Nutritional enhancements effected by vesicular-arbuscular mycorrhizae
(VAM) accrue largely through enhanced geometry. Much finer than the
narrowest rootlet, hyphae simply represent more cost-effective extensions
of the plant to explore substrates. Uptake of soil-immobile elements, like
P, by VAM more or less occurs in direct proportion to the amount of
medium contacted, whether by roots or by associated hyphae. Some of the
fungi involved in the less familiar types of mycorrhizae (e.g., ericaceous,
orchidaceous) attack soil humus to obtain essential ions (e.g., N), including some for plant use. They may also impart tolerance for certain toxins.
Enhanced disease resistance probably exceeds nutritional benefits among
the strongly mycorrhizal plants with extensively branched root systems
(Newsham et al. 1995).
210
Mineral nutrition
Several publications report fungi in the roots of bromeliads, but details
vary. Pittendrigh (1948) failed to document his contention that terrestrial
Bromelia humilis maintains mycorrhizae in northern Trinidad. Vascular
epiphytes at Rio Palenque and in wetter forest between 800 and 1800 m in
northwestern Ecuador bore extensive infections, and demonstrated the
difficulty of determining consequences for the host flora (Bermudes and
Benzing 1989). Roots of arboreal Pitcairnia pungens, the only bromeliad
examined, lacked spores and hyphae, but samples from another member of
the same genus native to lower montane forest at Monteverde, Costa Rica
supported light infections by an unidentified fungus (Lesica and Antibus
1990). Allen et al. (1993) examined the roots of three epiphytic bromeliads
(Catopsis nutans, Tillandsia bartramii, T. balbisiana) in seasonal woodland
near Chamela, Jalisco, Mexico and found no VAM, although septate
hyphae ramified through parts of every sample. Infected plant tissue free of
browning and fluorescence suggested something other than a pathogenic
relationship.
If Bromeliaceae form mycorrhizae, VAM is most likely (Janos 1993), and
indeed Rabatin et al. (1993) reported Glomus tenue infecting Vriesea platynema at the more arid of the two montane forest sites they sampled at
Rancho Grande, Venezuela. Extrarhizal hyphae extended from the roots
outward into the surrounding organic soil much as this hypomycete colonizes similar, relatively undegraded, desiccation-prone substrates at some
terrestrial sites. Spores and other diagnostic structures permitted additional identifications. Roots of Aechmea lasseri and Vriesea splendens contained auxiliary cells produced by Gigaspora and Scutellospora at the
second, wetter location, but neither fungus appeared in soil from the forest
floor. Rodents and invertebrates, especially those partial to the debris
impounded in and around bromeliad shoots (Paoletti et al. 1991; Table 8.2),
may transport inocula, much as their ground-based counterparts do among
terrestrial flora.
Experimental inoculation enhanced the vigor of the single bromeliad
tested so far. According to Aziz et al. (1990), pot-cultured Ananas comosus
grew more vigorously on P-deficient media following infection with VAM.
Pittendrigh’s Bromelia humilis and additional terrestrials less closely related
to pineapple probably also support mycorrhizae, perhaps obligatorily like
so many other soil-based plants. Then again, growing conditions in the
canopy may constrain photosynthesis too severely to render the inescapable costs of routine, compared with facultative, mycotrophy supportable
for the epiphytes (Janos 1993). Frequent occurrences of several largespored dictyostelid slime molds in canopy soils around the bases of
Mechanisms
211
Guzmania berteroniana and Vriesea macrostachya specimens in wet forest in
eastern Puerto Rico (Stephenson and Landolt 1998) indicate that heavy
propagules alone should not restrict the incidence of VAM among epiphytic Bromeliaceae.
Antibus and Lesica (1990) discovered surface-bound acid phosphatases
produced either by roots or by adhering micro-organisms associated with
22 epiphytes, including an unidentified phytotelm Aechmea species and
myrmecophytic Tillandsia bulbosa, at La Selva, Costa Rica. Assays based
on fresh weight placed the two bromeliads within the point scatter depicting the rest of the collection. Both species grew on bare branches, and, like
the several anthuriums and orchids and two ferns with similarly exposed,
relatively robust roots, they yielded lower readings than those recorded for
the epiphytes removed from the moist mats of bryophytes and humus covering the trunks and largest limbs. These more soil-like media possibly harbored a richer microflora; they certainly encouraged finer branching
leading to more root surface relative to mass. Acid phosphatases sometimes
increase access to organic P in soil, but whether similar benefits accrue to
the epiphytes remains unclear, as does the significance of the phytases and
acid phosphatases noted in the tank fluids of the sampled Aechmea specimens.
Aerobic N2 fixation attributed to cyanobacteria appeared in both terrestrial and arboreal substrates supporting bromeliads in eastern Ecuador
(Bermudes and Benzing 1991). Scrapings from Theobroma branches to
which a variety of bromeliads and other vascular epiphytes rooted at
Rio Palenque exhibited acetylene reduction (AR) rates equivalent to
5.4–17.7 ng g21 sample h21 (Table 5.12). Parallel sampling at the same sites
shortly after a heavy rain yielded higher values, ranging from 8.5 to 110.0
ng g21 sample h21.
Brighigna (1992) examined 12 Mexican Tillandsia species representing
either Type Five or taxa equipped with weakly developed phytotelma for
evidence that resident epiphyllae benefit hosts in a manner similar to what
certain microflora provide for some vascular epiphytes in India (Sengupta
et al. 1981). Freshly excised leaf segments and controls yielded comparable
AR activity, but bacteria plated on N-free media from eight of the sampled
species reduced significant amounts of acetylene. Isolates from relatively
dry-growing T. bartramii, T. circinnatoides and T. schiedeana outyielded all
the others. Bacillus and Pseudomonas species most often appeared in the
cultures; those of Aeromonas, Rahnella and Vibrio that more typically
inhabit wetter environments developed less often. Supposedly, transpiration provides the moisture needed to sustain the more drought-sensitive of
212
Mineral nutrition
Table 5.12. Acetylene reduction activity associated with epiphytic
bromeliads in the canopies of Ecuadorian forests. Values expressed as N
equivalents assume 1 mole of acetylene reduced 5 0.25 moles of N fixed.
Standard deviations are shown in parentheses
Species
Site 1 (Rio Palenque)
Aechmea angustifolia
A. angustifolia
A. angustifolia
A. angustifolia
A. angustifolia
A. zebrina
A. zebrina
A. zebrina
Vriesea ringens
Site 2 (Imbabura)
Guzmania melinonis
Guzmania sp.
Tillandsia asplundii
Unidentified species
(Bromelioideae)
Site 3 (Esmereldas)
Guzmania sp. (1)
Guzmania sp. (2)
Material sampled
ng N ha21
equivalent of C2H4
Tank fluid
Submerged epiphylls
Seepage zone (wet)
Seepage zone (dry)
Lichenized area
above bromeliad
Tank fluid
Submerged epiphylls
Seepage zone (wet)
Tank fluid
0.0a
0.0a
255b (19.8)
15.3b (10.8)
0.0c
0.0c
43300d
2600d
0.0b
1.12a (0.54)
0.0a
7.6b (1.5)
0.0a
0.0d
15.4c
0.0c
456d
0.0c
Submerged epiphylls
Submerged epiphylls
Submerged epiphylls
5.0a (0.57)
6.4a (3.7)
23.3a (0.43)
29.7c
13.8c
186c
Submerged epiphylls
30.9a (9.4)
123c
Submerged epiphylls
Submerged epiphylls
11.3a (4.9)
3.7a (1.12)
135c
32c
Source: After Bermudes and Benzing (1991).
Notes: aPer leaf. bPer cm2. cPer plant. dPer seepage zone.
these fixers, but considering the impressive water economy of the hosting
bromeliads, humidification must be minimal. Tillandsia circinnatoides, for
example, endures lengthy dry seasons in Mexican thorn forests by sparing
use of the moisture sequestered in its succulent foliage.
Puente and Basham (1994) concurred about the improbability of significant N2 fixation on the surfaces of Type Five bromeliads at the same time
as they reported a potentially beneficial endophyte in one of these same
plants. Their case rests on the recovery of Pseudomonas stutzeri from
surface-sterilized pieces of Tillandsia recurvata leaves plated on media
lacking combined N. Of the many additional bacteria also recovered, this
bacterium alone exhibited nitrogenase activity in AR assays. Tested plants
had grown on cacti and telephone wires in Baja California, raising the inter-
Mechanisms
213
esting question of how a microbe usually found in wet substrates infects
this exceptionally dry-growing bromeliad (Fig. 1.3A).
An arrangement noted in certain Poaceae may also benefit other monocots. Organisms that synthesize defensive chemicals reside within the leaf
sheaths of the grasses in question, having established there following
passage from the previous plant generation via contaminated seeds. More
germane to Puente and Basham’s claim, Acetobacter diazotrophicus living
in root, stem and leaf tissue meets up to 80% of the N requirement for some
Brazilian populations of sugarcane. But in the final analysis, in situ fixation
must be demonstrated to determine whether Pseudomonas stutzeri or any
other endophyte significantly augments the N budget of a bromeliad.
Bermudes and Benzing (1991) demonstrated a likely relationship
between cyanobacteria and phytotelm bromeliads in Ecuador. Incubated
whole plants and the scrapings from the seepage zones on adjacent bark
sometimes promoted substantial AR (Table 5.12). Assays of impounded
fluids and adjacent plant parts indicated that the diazotrophs resided
among the submerged epiphyllae. However, these colonies never grew as
abundantly as those responsible for the gelatinous masses that sometimes
clog the central tanks of Brocchinia tatei in eastern Venezuela (Givnish et
al. 1984). A broad variety of sometimes heterocystic taxa were recovered
from these Venezuelan specimens.
A phytotelm bromeliad may favor N2 fixation well beyond simply providing a convenient vessel when its foliage absorbs the NH41, amino acids
and other potentially autoinhibitory, low molecular weight nitrogenous
compounds that some diazotrophs release into N-poor media (Benzing
1970b; Fogg et al. 1973). Plant-encouraged inputs of certain other required
ions (e.g., K, P) from decomposing litter may further enhance diazotrophy.
Should the absorptive foliar trichomes featured by these epiphytes parallel
the transfer cells of certain other flora involved in more intimate exchanges
(e.g., Anabaena and the water-fern Azolla), the case for mutualism rather
than a fortuitous relationship becomes even stronger. Location of a
nitrogen-generating system comparable to a biological chemostat in leaf
impoundments could also help explain why many Type Three and Four
Bromeliaceae grow so vigorously and provide such high-quality habitat for
diverse canopy-based biota (Chapter 8).
Feeding by ants
Plant-feeding ants benefit certain Bromeliaceae through mechanisms that
divide the myrmecotrophic members into two categories (Madison 1979;
214
Mineral nutrition
Huxley 1980; Benzing 1991). One arrangement involves facultative to
obligatory use of ant-provided rooting media (i.e., carton; Fig. 8.1C).
Bromeliads rank among the better studied of these so-called ant-nest
garden types, but even so reports provide at best only sketchy perspectives
on a complex phenomenon that also involves numerous species of ants and
diverse plants (also species of Araceae, Gesneriaceae, Moraceae and
Piperaceae, among other families).
Nest-gardens warrant closer scrutiny to determine how they operate. For
example, do the tending ants, beyond providing substrates for the plants,
deter, ignore or encourage herbivores (e.g., Homoptera; Fig. 8.2D)? Roots
certainly reinforce the often brittle cartons, and the results of an experiment conducted by Yu (1994) suggest a second, potentially more decisive
influence. Vegetated nests in Amazonian Peru shorn of their foliage, but
otherwise left intact, incurred greater damage from heavy rain than unaltered controls, suggesting a sump pump-like action driven by transpiration.
Within months, cartons deprived of their leafy extensions collapsed,
forcing the ants to relocate. Other outcomes are more precisely documented. For example, ants responding to alluring fragrances, and sometimes edible appendages on seeds, assure plant dispersal from established
to developing cartons (Chapter 6).
Central to plant welfare, and our principal concern here, is the antconstructed rooting medium, specifically its chemistry, water-holding
capacity and durability. Carton represents a complex maché with physical
and nutritive attributes (Table 5.10) determined by the behavior of the
architects and supplies of local building materials. Soil or feces sometimes
receive high priority, whereas other Formicidae prefer fiber and similarly
inert materials less accommodating to seeds (Davidson and Epstein 1989).
Honeydew and the antibiotic secretions of the mandibular and other ant
glands add complexity and potential insect-specific qualities to carton
(Maschwitz and Holldobler 1970). However, the mycelia of at least one
fungus, Cladosporium myrmecophilum, regularly permeate certain arboreal
ant nests without obviously harming either the resident animals or the
plants.
Ants manipulate materials in tree crowns much as many of their relatives
and termites do on the ground (Lobry De Bruyn and Conacher 1990).
Certain arboreal Formicidae add to the debris accumulated by the
impounding shoots of epiphytic Platycerium and Drynaria ferns in the
process of improving these plants as nest sites (Koptur 1992). A diverse collection of opportunistic species colonize the Neotropical epiphytes, including many bromeliads (Chapter 7). Carton galleries crisscross much of the
Mechanisms
215
bark in some Amazonian forests, allowing extensive arboreal flora without
myrmecochores or special cavities for founding queens to also utilize antprovided substrates. Longino (1986) proposed that the ant-nest garden syndrome simply represents the most conspicuous manifestation of a
widespread and general use of carton by epiphytic vegetation. Associations
between termites and terrestrial and canopy-based Bromeliaceae come up
again in Chapter 8.
Members of the second group of bromeliads entice ants to supply nutrients to absorptive foliage rather than roots. Like the nest-garden flora, these
ant-fed, ant-house bromeliads and counterparts in other families usually
grow as epiphytes. The exceptions (e.g., Aechmea phanerophlebia,
Brocchinia acuminata; Figs. 2.2E, 2.4G, 8.1D) anchor on rocks or infertile
soil. In all, one or more species in at least seven families (Asclepiadaceae,
Bromeliaceae, Melastomataceae, Nepenthaceae, Orchidaceae, Piperaceae
and Polypodiaceae) reportedly produce myrmecodomatia (special hollow
organs or cavities within more conventional plant parts to accommodate
plant-feeding symbionts; Huxley 1980). But, unlike some of the other
species engaged in this same kind of mutualism, ant-fed, ant-house bromeliads offer no extrafloral nectar or solid food primarily to support their associates.
Low-cost housing represents the ant-house bromeliad’s single contribution to the welfare of its zoobiont, except where inflorescences and perhaps
other vulnerable organs provide convenient substrates to farm Homoptera
(Fig. 8.2D). In return, the myrmecotroph definitely obtains nutrients,
perhaps with a modicum of protection included, but almost certainly less
than received by certain better-known terrestrials (e.g., Acacia, Cecropia).
Trees and shrubs of this second description shelter massive populations of
pugnacious ants in probably nonabsorptive thorns and stems, primarily to
deter herbivores. Unlike the relatively docile mutualists that inhabit bromeliads and some other epiphytes, those defending these small trees need
not leave their hosts to search for additional food. Ant-house and ant-nest
garden ants, by contrast, forage widely, acting as proxies for root systems
incapable of exploring as much space as workers scour to feed their nest
mates.
Exchanges between ants and the bromeliads they inhabit or supply with
rooting media remain little studied beyond some crude experiments.
Calcium (45Ca), a phloem-immobile element applied to leaf bases, moved
throughout the shoots of cultivated ant-house Tillandsia caput-medusae
(Benzing 1970a; Fig. 5.2B). Ant-deposited materials extracted from chambers within the bulbs of this same species in Costa Rica, and provided as
Mineral nutrition
216
Table 5.13. Quantities of elements intercepted
over a 10-month period by sample bottles
suspended in the crowns of Quercus virginiana
near Tampa, Florida. Values are mg per bottle
Sample number
Element
N
P
K
Ca
Mg
Na
1
27.2
3.23
3.54
5.36
0.81
2.43
2
7.19
0.41
1.34
5.74
1.09
0.84
3
15.6
1.46
1.76
11.7
2.72
3.68
4
3.20
0.28
—
2.00
0.20
0.30
Source: After Benzing and Renfrow (1974a).
an amendment to aseptic media, supported considerable growth by
Aechmea bracteata seedlings. More comprehensive inquiries could characterize important aspects of bromeliad myrmecotrophy, specifically, ant
contributions to nutrient budgets, consequences for plant fitness, and any
peculiarities of ion sorption or N metabolism. Non-nutritional aspects of
the ant/bromeliad symbioses receive more attention in Chapters 6 and 8.
Nutrition that requires a phytotelma
Plant reliance on phytotelmata fashioned from foliage (the phytotelma),
although widely homoplasious among the ferns and angiosperms, nowhere
exhibits as many interesting dimensions as in Bromeliaceae. Hundreds of
species intercept moisture and nutrient-rich solids in cistern-like shoots,
while the roots of these plants serve primarily for anchorage to bark or rock
(Figs. 2.4, 5.1). Urine sample bottles set out as crude simulators for nearly
a year in live oak (Quercus virginiana) trees in central Florida accumulated
substantial nutrients, mostly derived from litter (Table 5.13). A short stem
bearing numerous, channeled leaves, each with an expanded water-tight
base, accomplishes the same outcome more effectively (e.g., Table 5.8).
Solids recovered from a mature specimen of Guzmania monostachia
growing in a Florida swamp forest yielded larger quantities of several
essential elements than present in the tissues of the impounding shoot
(Table 5.8). Humus present in the leaf axils of Vriesea platynema specimens
early in the dry season at Rancho Grande, Venezuela contained N, P and
Mechanisms
217
K at concentrations above those reported in soil under the same trees
(Paoletti et al. 1991). Dissolved P occurred in the tanks of several Jamaican
bromeliads between 0.1 and 0.51 ppm (Janetzky and Vareschi 1993; Fig.
8.13). However, no effort was made to determine how much of this reserve
was immediately available (ionic) to the plant or still required processing by
tank biota.
Important aspects of nutrition differ among the phytotelm bromeliads
according to the kinds of materials intercepted, and who prepares these
inputs for plant use. In all instances, animals provide assistance, but the
nature of that involvement varies, as does the fate of the participating
fauna. Greater plant specialization and energetic cost accompany the utilization of prey compared with litter, so carnivory warrants coverage first.
Carnivory
Carnivorous plants produce traps often equipped with lures and digestive
secretions in order to supplement the typically meager supplies of mineral
nutrients present in soils where these plants grow. Impoverished substrates
probably favored Darwinian modification of foliage to secure inorganic
nutrients in addition to photons, but this change brought complications. As
the costs of construction and operation increased while the leaf evolved the
qualities necessary for carnivory, its photosynthetic capacity diminished.
Consequently, the power to amortize investments in an organ that now provides two vital, but not particularly compatible, plant services also diminished (Givnish et al. 1984). The Givnish et al. model essentially explains the
evolution of carnivory using the same economic paradigm described earlier
to rationalize the relationships among leaf longevity, chemical makeup and
cost, and capacity for photosynthesis.
Two additional environmental factors influence the economics of botanical carnivory. Substantial drought or shade, both of which constrain
photosynthesis, also render habitats unsuitable for the sundews, pitcher
plants and other obvious prey-users as the model contends (Thompson
1981; Givnish et al. 1984). Protocarnivores, those flora that capture fauna
with less expensive foliage than the more specialized leaf traps, should
exhibit less stringent growth requirements. How many Bromeliaceae experience conditions that favor either condition remains obscure, but the
numbers and distributions of the unequivocal prey-users suggest limited
opportunity.
Claims that a particular bromeliad is carnivorous sometimes rest on
weak foundations. Wheeler (1921), in his classic writings on Neotropical
218
Mineral nutrition
ants, said of Tillandsia species with hollow bulbous bases (i.e., ant-house
species; Figs. 8.1D, 8.5) that ants ‘make fatal incursions into H2O-containing chambers’. Wheeler’s trapping sequence could not be corroborated
using either Mesoamerican Tillandsia butzii or T. caput-medusae (Benzing
1970a). Dissected shoots displayed dry axils teeming with brood and adult
ants, and repeated attempts to flood intact bulbs by immersion or spraying
failed. Also present were those previously mentioned ant-deposited nutrients and the absorptive trichomes needed to exploit them.
Picado (1911, 1913) was the first authority to provide experimental
results to support claims about bromeliad carnivory. Amino acids added to
the phytotelmata of several Costa Rican Tillandsioideae vanished as if
absorbed through adjacent leaf surfaces. Picado also discovered proteolytic
enzymes associated with mucilage, presumably the same product released
by the damaged foliage and stems of many Type Four Tillandsioideae. No
glands were apparent, nor did Picado demonstrate that these proteins came
from the bromeliad rather than from co-occurring microbes. In more
closely monitored studies, two typical phytotelm forms, Aechmea bracteata
and a Nidularium hybrid, appeared to take up amino acids and perhaps
bovine serum albumin from tank fluids (Benzing 1970b). However, the
absorption of organic molecules similar or identical to those that degrading tissues release, although consistent with prey use, is not proof of this
activity.
Rees and Roe (1980) reported that giant Andean Puya raimondii, the
largest of all the bromeliads and a colonizer of some of the harshest of the
high Andean habitats supporting vascular flora (Chapter 7; Fig 14.2C), utilizes nutrients released from the carcasses of decomposing birds impaled
on its well-armed foliage. Forced to use these exceptionally tall bromeliads
for lack of other perches in barren landscapes, local avians often fall victim
to the sharp, recurved marginal spines supposedly evolved to harvest them.
Givnish et al. (1984) disagreed, suggesting instead that the responsible
armature probably evolved its present character to thwart Andean bears
whose descendants continue to eat many of the emerging inflorescences of
other local Puya species, as do indigenous Homo sapiens. Additional bromeliads produce comparable spines (e.g., Hechtia, Bromelia, other Puya;
Fig. 2.13A) that repel large herbivores seemingly without threatening birds.
Heliophilic, phytotelm Catopsis berteroniana (Fig. 5.3A,B) ranges from
southern Florida to southeastern Brazil, reputedly depending more on
animal than plant biomass for nutrients (Fish 1976). Its shoots differ from
those of most of the other Type Four species by a more upright stature, yellower color, and the presence of a copious, friable, epicuticle (Fig. 5.3A).
Mechanisms
219
Leaf bases bear heavier coats of wax than the blades, and exposed sites at
the tops of trees support the densest populations of vigorous specimens.
Tanks contained relatively more animal remains and less litter than those
of the other co-occurring phytotelm bromeliads located in similarly
exposed microsites in Florida.
Fish reasoned that UV light reflected from the cuticle helps trap prey,
much as some pitcher leaves (e.g., Heliamphora; Fig. 5.3D) improve their
catch aided by the same material. Supposedly, flying insects become confused as they cue on sky light according to the usual practice used to negotiate canopy obstructions. After colliding with a poorly outlined shoot,
fauna tumble into its impounded fluids and drown, unable to escape
because that same light-scattering wax also denies sound footing. Victims
eventually decompose, releasing nutrients that enter the shoot via its
absorptive trichomes. Plants produced no detectable digestive secretions,
relying instead on symbionts to degrade prey.
Catopsis berteroniana captured more insects than several other tank bromeliads while combinations of test plants were interspersed on fence posts
during an experiment in Florida (Fish 1976; Frank and O’Meara 1984), but
the suggested importance of UV reflectance to that outcome requires confirmation. Surveys of nutrients in plants and tanks and rates of interception are also needed to establish whether processed prey contribute
significantly to plant welfare. If nutrients provided by nonsymbiotic fauna
routinely eliminate or greatly reduce the requirement for litter, then designation as a low-grade carnivore seems reasonable. However, terrestrial
Brocchinia reducta (Fig. 2.4F), and probably also closely related B. hechtioides, exhibit the greatest investments and specializations for prey use in
Bromeliaceae.
Brocchinia reducta ranges more extensively through the Guayanan highlands than most of its fewer than 20, mostly ground-based congeners
(Chapter 9; Givnish et al. 1997). The largest populations inhabit moist
savannas situated over porous, impoverished soils derived from
Precambrian sediments of the Roraima Formation. Brocchinia hechtioides,
a somewhat larger version of B. reducta, grows largely confined to the
cooler, humid summits of the scattered, ancient table mountains (tepuis) of
the Pantui known for their extraordinarily relictual and endemic biotas.
Environments at both kinds of locations favor botanical carnivory according to economics (Givnish et al. 1984) and the composition of the co-occurring flora. Many communities inhabited by Brocchinia reducta and B.
hechtioides also support one or more species of Drosera, Genlesia,
Heliamphora and Utricularia. Collectively, these taxa constitute variety
220
Mineral nutrition
unequaled elsewhere among the carvivores except possibly on similarly
low-quality substrates in the most humid regions of southwestern
Australia.
Brocchinia reducta belongs to a group of carnivores defined by several
aspects of prey use and a sometimes narrow food base. It and four cooccurring South American pitcher plants (all Heliamphora) mostly trap
ants (but see below) attracted by color, fragrance and, in some cases, nectar.
Sarracenin, an enoldiacetal monoterpene first identified as the fragrance
lure for related Sarracenia flava, also assists Heliamphora, perhaps as one
of a suite of fragrances that vary with the taxon and possibly among geographically distinct biotypes of the same species. A similar, perhaps identical, pleasant-smelling product characterizes B. reducta, although this plant
does not utilize nectar like that presented on the distal appendage of the
more brightly colored, red and green trap leaves of Heliamphora.
Hallmarks also include a tall, tubular, uniformly yellow shoot densely
covered on adaxial surfaces by a loose cuticular powder that impedes the
escape of prey from the single, steep-sided phytotelma (Fig. 2.4F).
Brocchinia reducta shoots examined by Givnish et al. (1984) in the Gran
Sabana, Venezuela contained abundant, and unusually diverse, degraded
prey. Exoskeletons representing 31 families in six orders filled the lowest
1–2 cm of each tank, but ants belonging to eight genera, all potential
nectar-seekers, still constituted about 90% of the total catch. Mosquito
larvae (Runchmyia and Wyeomyia) frequented shoots with impunity, fully
tolerant of acidities (pH around 2.8–3.0) well below those recorded for any
other bromeliad except B. tatei. Most indicative of carnivory among the
many traits present, according to Givnish et al., is the fragrance.
Association of the same odor with the crushed foliage of several noncarnivorous Brocchinia species suggested another, earlier role unrelated to the
attraction of insects.
Jaffe et al. (1992) detected proteolytic enzymes in the fluids contained in
the young, unopened and older pitcher leaves of Heliamphora tatei, but not
in the traps of its four relatives, the phytotelmata of co-occurring
Brocchinia tatei, or an unidentified local Tillandsia species. However, pH
was sometimes much lower in the phytotelmata of the bromeliads (3.4–5.7)
than in those of the heliamphoras (.4.9). Gonzales et al. (1991) surmised
that Brocchinia reducta competes for its primary prey with Heliamphora
nutans on Kukenan-tepuy in southeastern Venezuela. Solenopsis sp., the
only ant recorded at the study site, widely exceeded all other fauna in the
traps of both plants (Table 5.14).
Gonzales et al. (1991) assigned Brocchinia reducta generalist feeder status
Mechanisms
221
Table 5.14. Percentage of plants containing arthropods in a patch of
Brocchinia reducta and Heliamphora nutans in Kukenan-tepuy.
Individuals per leaf tank (mean diameter) is given in parentheses
Brocchinia reducta
Inhabitants
Diptera (larvae)
Culicidae
Wyeomyia sp.
Chironomidae
Metriocnemus sp.
Prey
Aranea
Diplopoda
Acarina
Collembola
Homoptera
Lepidoptera
Coleoptera
Diptera
Ceratopogonidae
Culicoidel spp. (adults)
Sciaridae
Others
Hymenoptera
Formicidae
Solenopsis sp.
Chalcidoidea
Large plants
.40 cm
(n55)
Small plants
,25 cm
(n56)
Heliamphora nutans
(x̄512 cm; n515)
0 (0)
0 (0)
47 (1.9)a
80 (14.2)
100 (33.2)a
67 (23.5)
80 (1.8)
0 (0)
20 (0.2)
0 (0)
60 (0.6)
0 (0)
80 (1.2)
67 (1.2)
0 (0)
50 (4.0)
100 (36.2)a
83(2.3)a
17(2.3)
0 (0)a
13 (0.2)
7 (0.1)
0 (0)
0 (0)a
0 (0)a
0 (0)
0 (0)
0 (0)
0 (0)
40 (1.2)
83 (11.2)a
100 (7.4)a
50 (0.8)
27 (3.6)
13 (0.5)
33 (0.4)
100 (28.8)
0 (0)
100 (144.7)a
100 (2.8)a
100 (159.0)
0 (0)a
Source: After Gonzalez et al. (1991).
Note: aIndicates statistically different samples (Mann–Whitney U-test) P,0.05;
between small and large B. reducta (in second column) or between H. nutans and
all B. reducta (in third column).
because it captured the greatest variety of sometimes unexpected fauna.
Among the partially digested arthropods in many sampled phytotelmata
was a parasitic chalcidoid wasp lured for unknown reasons only to preflowering shoots. Phytotelmata of Brocchinia reducta and Heliamphora
nutans both nurtured symbionts, primarily larvae of the potentially preyprocessing midge Metriocnemus sp. Young shoots of the bromeliad produced the strongest fragrance and contained the most abundant exoskeletal
fragments. Substantial quantities of plant debris, including frass, suggested
222
Mineral nutrition
that each Brocchinia reducta shoot becomes increasingly arthropod-fed
after an initial carnivorous stage. Long-established genets bear several
cohorts of interconnected ramets so may benefit from both mechanisms
simultaneously.
Joel (1988) considered Brocchinia reducta a likely Batesian mimic, not of
flowers, but of sympatric and rewarding Heliamphora hederodoxa, which it
resembles in size, shape, color, smell and nutritional mode, but not nectar
secretion. A Batesian designation requires that the bromeliad offer no
reward to the operator (potential prey), which it apparently does not, but
still attract fauna seeking food. Insects that successfully visit H. hederodoxa
pitchers may learn that objects of this general description offer sustenance,
and, from that experience, end up even better primed to become prey for
Brocchinia reducta. All other cases of mimicry among carnivorous plants
involve, according to Joel, Müllerian mimicry. They and co-occurring
species that bear nectar-producing flowers utilize a convergent strategy by
offering rewards, but to different ends of course. These insect-pollinated
angiosperms and the carnivores that also use nectar lures reinforce one
another to the extent that pollinators drawn to traps survive that experience.
Additional information indicates that the plants that utilize prey qualify
as Batesian rather than Müllerian mimics. No evidence suggests that insects
visit pitchers by mistake and no specific models seem to exist for any of the
carnivores. Finally, recognized prey-dependent flora usually occur too
abundantly at the exceptional locations that favor this life style to succeed
as deceptive mimics. But then Brocchinia reducta sometimes vastly outnumbers Heliamphora hederodoxa where the two taxa grow interspersed in the
Venezuelan Gran Sabana (personal observation). Obviously, the intricacies
of Brocchinia reducta nutritional biology exceed the theory and data currently available to explain them.
Carnivory represents but one way fauna enhance bromeliad nutrition,
and the other mechanisms cost the plant less, occur more broadly through
the family, and incorporate mutualisms rather than predation. Feeding by
live ants takes plant economy a substantial step beyond the use of prey
because nothing need be digested. Thompson (1981) suggested that more
epiphytes engage in myrmecotrophy than carnivory because cost is low, and
shade and drought so often prevail in tree crowns. Additionally, organs
modified to house ant colonies tend to be durable, thickened stems that
simultaneously provide mechanical and vascular support and even water
storage, a need the epiphytes more often satisfy with succulent foliage.
Finally, housing constitutes a scarce commodity for many tropical ants,
Mechanisms
223
and that fact in turn probably added impetus to the emergence of plant cavities suitable as nest sites.
Animal-assisted saprophytes
Litter-dependent bromeliads employ the least complicated and arguably
the cheapest arrangement in the family to use animals to assist nutrition
(Figs. 2.4, 5.1, 5.2A). Simply put, moist habitat within a funnelform shoot
readily sustains a rich microflora, abundant detritivores, and additional
fauna that variously hide, feed or oviposit in comparative safety; in return,
the host obtains substantial required ions in addition to a relatively constant supply of water. Given the ubiquity and ease of maintenance of biota
capable of mineralizing phytomass, plant costs remain low. No myrmecochores or other ant foods are needed, nor must the bromeliad tolerate cultivated Homoptera. Whether vulnerability to herbivory exceeds that of the
ant-house, and particularly the nest-garden, species remains unclear.
Givnish et al. (1984) highlighted the importance of humus to the approximately one-third of all Bromeliaceae dependent on this medium by applying the label saprophyte, which, although accurate, fails to credit all of the
players.
So how does what I prefer to call animal-assisted saprophytism compare
with botanical carnivory? Phytotelm bromeliads dependent on humus and
the pitfall carnivores (pitcher plants) share some, but not all, features
related to nutrition. Both groups rely on absorptive foliage and support
symbiotic fauna (e.g., Okahara 1932; Plummer and Kethley 1964), but the
relationships between plants and attracted animals differ. Most notably, the
pitcher plants, at least those that secrete digestive enzymes (e.g., Nepenthes,
some Sarraceniaceae), differ from litter-dependent Bromeliaceae in the relatively commensalistic vs. mutualistic nature of their interactions with symbionts.
These two arrangements differ in complexity and probably also in importance to the plant. The often diverse collections of invertebrates that colonize bromeliad shoots augment and benefit from the activities of the
microbes that decompose phytomass. Specifically, they shred litter, consuming some, and, to varying extents, feed on each other (Chapter 8).
Microbes affect mineralization through the entire sequence, and probably
promote the digestibility of the material ingested by the detritivores
(Cummins et al. 1989). Bradshaw (1983) reported that arthropod larvae
and a collection of lower organisms also hasten the consumption of
drowned prey in Nepenthes and Sarracenia traps. But are these scavengers
224
Mineral nutrition
really necessary for plant welfare, or would enzymes from the plant or associated microbes be adequate for that task?
The occurrence of just two or three prey-users within a clade of about
3000 species poses another interesting question. Every other family with
carnivorous members, some comprised of dozens of species distributed
among two or more genera (e.g., Lentibulariaceae), include no noncarnivorous populations. So why does a device, the phytotelm shoot, that occurs
so widely through Bromeliaceae so rarely exhibit the necessary embellishments for prey use? Why have just those two lineages, one in Pitcairnioideae
(two species), the other in Tillandsioideae, independently become carnivorous? Constraints related to the costs of lures, enzymes and related devices
provide a plausible argument for the general rarity of botanical carnivory,
but can economics also explain why so few phytotelm bromeliads utilize
animal rather than plant tissues?
Botanical carnivory, while consistent in some respects (e.g., all participating plants occur on exposed, infertile and humid substrates), varies on
two important counts. First, extrafloral nectaries, fragrances and digestive
glands are optional; several combinations of plant characters, some lacking
one or more of these three features, suffice for prey use. Second, these three
and the other characteristics involved in the direct use of fauna for plant
nutrition evolved repeatedly through redeployments of widely available
genetic potential (Benzing 1987b).
Modifications for carnivory in Bromeliaceae are notably simple compared with those of the more specialized prey-users (e.g., Dionea,
Utricularia), and the component features provide unrelated services to
close relatives. Many fully autotrophic bromeliads produce floral fragrances and friable cuticles, and their foliage is organized into a steeply
tubular phytotelma much like Brocchinia reducta and Catopsis berteroniana
(Figs. 2.4F,K, 5.3B). So why are only three bromeliads carnivorous when
hundreds of additional species also maintain phytotelmata and grow on
infertile substrates, in many cases with limited access to litter? Or maybe we
should reverse the question: why do the fauna attracted to bromeliad phytotelmata ever promote plant welfare as prey rather than litter processors?
Perhaps phytotelm Bromeliaceae engage fauna for nutrition in ways
beyond carnivory and animal-assisted saprophytism as scattered reports
suggest. We could be dealing with a collection of mechanisms that manipulate animals in different ways for the same plant benefits. Much could be
learned about bromeliad nutrition by examining plants with different shoot
architectures, and watching the animals that visit them. Two questions
could guide these inquiries. First, are species beyond the three recognized
Mechanisms
225
carnivores always animal-assisted litter processors as just described?
Second, how much variety exists among the taxa truly dependent on phytomass in the ways they use this resource? An important consideration concerns the nutritional value and digestibility of the two substrates in
question, viz. animal and plant biomass.
Litter processing with plant-produced enzymes is untenable. Although
vegetable, rather than animal, tissue constitutes the most abundant source
of nutrient ions in the forest canopy, the former’s recalcitrant nature (e.g.,
abundant cellulose, lignin) and low quality (nutrient content) prohibit
direct recycling from litter. Unsustainable investments in plant protein
would be necessary to extract the same amounts of nutrient contained in
the much smaller volumes of material secured by the carnivore. Therefore,
reliance on mutualists accords with the ubiquity of that biota, the refractory nature of plant cell walls, and the massive amount of spent phytomass
that settles cost-free on bromeliad shoots in so many habitats. Nevertheless,
access to animal-assisted saprophytism poses problems for some
Bromeliaceae, enough perhaps to favor uses of fauna in ways other than as
prey or detritivores.
Plant investments required to encourage mutualists to release nutrients
from impounded phytomass are comparatively low, but yield probably
varies with the element. Whereas unusually mobile elements such as K
readily diffuse from dead vegetable and animal tissue, others remain more
tightly bound in plant remains. Nitrogen, in particular, may mineralize too
slowly to allow more than marginal harvest before the impounding shoot
dies, according to assays of Guzmania monostachia in Florida (Table 5.8).
Nitrogen to potassium ratios in the materials taken from shoots ranged
from about 5:1 to 39:1 compared with about 1:1 to 2:1 for functioning tree
foliage (Benzing and Renfrow 1974a). Much of the K formerly incorporated in that phytomass had either been recovered prior to abscission,
entered the bromeliad, or been flushed from the phytotelmata before
uptake could occur. Much more of the N apparently remained immobilized, perhaps significantly depriving the bromeliad.
Shoot architecture, anchorages and climate favor specific kinds of phytotelm nutrition. Plants with spreading foliage (Fig. 2.4H) operate like
filter-feeders, readily intercepting settling plant debris. Like their sessile,
invertebrate counterparts (e.g., bryozoans, corals) in marine habitats,
inputs vary according to body form and exposure, which on land influence
the types of phytomass intercepted, and the processors the bromeliad will
likely host. Laessle (1961) and Frank (1983) described broad differences in
the animal and vegetable contents of tanks depending on the microsite.
226
Mineral nutrition
Laessle labeled the associated nutritional modes ‘dendrophilous’ or
‘anemophilous’. Primary sources for anemophilous types remain obscure,
but probably include more than wind-blown debris. High exposure and a
spreading shoot promote an autotrophic community in phytotelmata, and
shade, whether self-imposed or from without, encourages heterotrophy.
Photosynthetic types might compete with the bromeliad for key ions
(excepting N if diazotrophic).
Shoot morphology and exposure also influence plant nutrition by
affecting washout. Those broad shoots with channeled leaves that so
effectively intercept litter (e.g., Fig. 2.4) sometimes overflow, although not
necessarily to the detriment of the bromeliad, according to one experiment.
A nonabsorbent dye placed in the water-filled axils of immature Aechmea
bracteata plants indicated substantial, but incomplete, flushing during
heavy showers (Benzing et al. 1972; Table 5.15). Solids and litter, and the
biota needed to process it, presumably require even greater turbulence to
dislodge. Shoots of other configurations would probably behave differently
under the same conditions.
Aspects of space and time also influence options for nutrition, and shed
additional light on why litter rather than prey use prevails among phytotelm Bromeliaceae. On average, the Sarracenia purpurea leaf (Fish and Hall
1978), and presumably the traps produced by other pitcher plants, survive
no more than one year, too little time to build up the complex communities
needed to degrade abundant phytomass. Individual leaves of the phytotelm
bromeliad may live no longer (Fish 1983), but they develop close together,
and important fauna need move only short distances to migrate with their
somewhat mobile habitats (Fig. 2.4). Closely connected, sympodial shoots,
compared with the more widely separated trap leaves of many of the carnivores, further reduce needs to rebuild communities of detritivores.
Climate that influences plant form, which in turn affects litter supply,
predisposes certain bromeliads for useful contacts with drought-sensitive
vertebrates rather than detritivores. Billbergia porteana (Fig. 2.4K), for
example, illustrates how exposure and drought favor a shoot that accommodates neither the litter-dependent nor the carnivorous condition, but
instead encourages a third arrangement with beneficial fauna. Upright
stature and slender shape minimize exposure to direct-beam insolation and
insulate the water supply enough to account for the over-representation of
species with this form in strongly seasonal habitats (e.g., Brazilian caatinga;
Fig. 1.4B).
Tubular form that reduces capacity to intercept litter grants Billbergia
porteana and its kind extraordinary opportunity to use amphibians that in
Mechanisms
227
Table 5.15. Impoundment capacity of an Aechmea bracteata specimen, the
recharge of that same shoot after being emptied, and the dilution of a dye
solution in the same tanks by rain showers
Percentage of dye
Tank number by
Percentage of tank remaining in the
position from the shoot Capacity of the capacities filled by same tanks after
center outward
tanks (ml)
2.6 cm rainfall
2.1 cm rainfall
Center
1
2
3
4
5
6
7
93
61
43
49
20
15
46
8
81
75
100
89
100
100
100
63
39.5
16.0
59.5
35.0
62.0
66.0
46.5
67.0
Source: After Benzing et al. (1972).
some cases already bear evidence of extended and intimate associations
with bromeliad shoots. Particularly striking are the exceptionally flattened
heads that certain frogs employ to close off the narrow phytotelmata characteristic of several Brazilian species (Fig. 8.4E,F). Prolonged occupancy
during dry weather virtually assures the inhabited bromeliad a supply of
nutritive excrements. Statistics on visitations and animal outputs relative to
plant requirements would help evaluate the biological significance of these
relationships. Additional discussion of how the architecture of the bromeliad shoot influences where these plants grow appears in Chapter 7.
Tank soil-root bromeliads
Certain Ananas and Bromelia species (Fig. 2.14A,B) bear mention because
they probably resemble family ancestors in aspects of structure, function
and ecology. Pittendrigh (1948; Table 4.2) reserved his Type Two designation, the tank-root type, for these Bromelioideae because roots often
ramify more extensively among adjacent leaf axils than through underlying soil. Trichome-covered leaf bases augment uptake for Ananas comosus
(Sakai and Sanford 1979), although the amounts of impounded debris
often seem inadequate to totally satisfy plant needs. Ecophysiology further
distinguishes these plants. In addition to moderate succulence, recessed
stomata, and thick cuticles – in effect a basically xeromorphic character –
crassulacean acid metabolism (CAM) assures the water economy needed
228
Mineral nutrition
to survive lengthy dry seasons in typically warm, lowland habitats (Fig.
2.13B).
Studies of Ananas comosus and several Bromelia species have revealed
complex relationships among plant vigor, light response, N status and relative emphasis on CAM vs. C3 metabolism (e.g., Fetene et al. 1990; Medina
et al. 1991a,b; Chapter 4). Controversy about how phenotype reflects
growing conditions now as compared with the past continues. Responses in
situ and in the laboratory suggest that members of both genera, if not the
entire subfamily, share a decidedly shade-tolerant stock. Whatever the
nature of the ancestral habitats, extant wild types utilize high photosynthetic photon flux density (PPFD) less effectively than some other CAM
plants (e.g., certain Agave, Opuntia; Nobel 1991) that, along with similarly
heliophilic pineapple cultigens, match the productivities of several C3 and
C4 crops, in some cases exceeding them in water-use efficiency (WUE).
Chapter 4 provides additional details on photosynthesis and water
balance in Ananas and Bromelia. Briefly, N invested in foliage – that reliable predictor of Amax mentioned earlier – diminished in situ in Venezuela
at high PPFD whether expressed on a leaf area or weight basis. Medina et
al. (1986) and Medina et al. (1991a,b) suggested two potential causes:
greater soil fertility in understory habitats and more structural carbon in
sun vs. shade leaves, i.e., a dilution effect (see also Maxwell et al. 1995).
Water and temperature stresses purportedly further curtailed growth in
fully exposed microsites, a claim supported in most comparisons by less
negative D values in biomass, which indicate greater reliance on CAM.
Medina et al. (1991a,b) made no mention of a third agency that probably
helps explain why foliar N diminishes with exposure. Strong fluence photoinhibited some Bromelia humilis specimens enough to require several hours
in shade for recovery (Medina et al. 1986); more severe stress may chronically reduce N concentrations. Sufficiently overexposed foliage requires
weeks to months to replace the labile D1 proteins associated with photosystem II and restore quantum efficiency (Long et al. 1994). Maxwell et al.
(1995) reported dramatic reductions in the chlorophyll content in
Guzmania monostachia moved from partial to full sunlight (Fig. 4.26).
Perhaps a better-protected light-harvesting apparatus, irrespective of N
content, accounts for the relatively heliophilic nature of certain Ananas
comosus cultivars. Uneven capacity to dissipate excess light energy via xanthophyll-cycle activity may also explain why specific Bromeliaceae perform
differently in full sun.
Involvement of foliar trichomes
229
Involvement of foliar trichomes
Absorbing foliar trichomes operate under a variety of conditions, and
structure and function varies to match specific circumstances. Those
appendages lining the leaf bases of the phytotelm bromeliad remain continuously bathed in nutritive fluids. At the opposite extreme, no degrading
biomass, ant products or earth soil help sustain the hundreds of nonmyrmecotrophic Type Five, mostly epiphytic and lithophytic Tillandsioideae
(Fig. 5.1). Uptake occurs solely when precipitation bathes otherwise dry
shoot surface equipped with dense indumenta; these same foliar organs
mediate additional services during dry weather. Roots, when present,
provide holdfast only (Figs. 2.1, 2.10). Our concern here is the uptake of
water and nutrient ions by trichomes, primarily absorption of the second
of these two resources.
Water relations
Chapters 2 and 4 describe the foliar scale of Tillandsioideae as a peltateshaped organ comprised of a shield or plate of usually dead cells anchored
to the epidermal basement by a living stalk (Fig. 2.7A,B). Briefly, four large,
equal-sized central cells dominate the center of the shield and secure it to
the dome cell, which constitutes the distal member of that subtending, uniserrate stalk. Extraordinarily thick tangential walls of the central disc alternately rise and fall on flexible radial walls as precipitation and evaporation
alternately fill and empty the underlying lumina. Several additional rings of
cells, each made up of twice as many members as the one within, surround
the four central cells. An outermost, asymmetrical wing contains many
more and much more elongated cells than those within (Fig. 2.7D).
Absorption occurs while ion-charged fluids contact those parts of the
shoot bearing trichomes.
Ultrastructure reveals that the dome cell is well equipped to mediate ion
uptake. Moreover, its boundary lies just microns away from the nutrientcharged fluids that periodically to continuously engorge the central disc.
Diverse organelles, especially rough endoplasmic reticulum, dictyosomes,
microtubules and mitochondria, densely fill the protoplast (Dolzmann
1964, 1965). An elaborately folded plasmalemma characteristic of plant
transfer cells assures intimate contact with abundant electron-dense
material located just within the cell wall (Brighigna et al. 1988).
Concentrations of plasmodesmata at every junction along the stalk allow
extensive communication with the mesophyll. A parallel apoplastic conduit
230
Mineral nutrition
also seems likely, given the absence between cells of the cuticle that invests
the outer walls of the stalk.
Several workers, including Haberlandt (1914) and Mez (1904), demonstrated that hypertonic salt solutions applied to intact leaf surfaces plasmolyze the mesophyll cells adjacent to the bases of the affected trichome
stalks. Vital stains followed the same route, but more compelling evidence
of the involvement of the foliar indumentum in nutrition would require the
more sophisticated techniques that would not become available for many
more decades (e.g., Benzing et al. 1976; Ehler 1977; Owen et al. 1988).
Water relations would also attract continuing attention. For example,
Brighigna et al. (1988) noted little difference in the ultrastructure of the
stalk cells of Tillandsia usneoides whether leaves had been fixed following
incubation for eight days at 80% relative humidity or desiccated up to 23%
over silica gel. Foot cells of the better-hydrated samples contained larger
vacuoles. These investigators also reported that the shields of mature trichomes sometimes retain their protoplasts, a rarely reported condition that
challenges the classic explanation of how the foliar scale operates as a oneway valve.
Rather than beading up, a drop of moisture placed on the leaf of a Type
Five Tillandsia spreads from one trichome shield to the next, in turn,
causing the upper walls of the central discs to rise and the wings to flatten
as the lumina fill with water (Fig. 2.7A,B). Mez (1904) imputed an accompanying suction mechanism (hence his term ‘trichomepump’) during
engorgement without demonstrating that force. Moisture subsequently
fluxes from the charged shield into the dome cell and on to the mesophyll
until either the water potentials inside and out equilibrate or the indumentum dries. In the second case, the lumina of the central disc collapse, restoring the barrier provided by the thickened walls of the central disc. So
configured, the shield prevents water from wicking out the leaf along the
path of entry. Reflexed upward, the wing again scatters light, and the
silvery, rough texture that highlights the shoots of Type Five Bromeliaceae
returns.
In effect, trichomes of the type that invest the foliage of Type Five
Tillandsioideae serve as one-way valves and energy dissipaters, alternately
hydrating the plant and insulating it against water loss, photoinjury and
excess heating. Controversy continued for many years over whether trichomes appreciably amend water deficits from adjacent moist air (Chapter
4). Plants do gain moisture by this route, but not enough to replace the need
for contact with liquid moisture (Garth 1964; De Santo et al. 1976; Benzing
and Pridgeon 1983; Martin and Schmitt 1989; Figs. 4.12, 4.22).
Involvement of foliar trichomes
231
Sorption of solutes
Bromeliads with essentially mechanical or no root systems accumulate
nutrients primarily while precipitation, canopy washes or impounded solutions bathe the foliar trichomes. Potentially beneficial gases (e.g., NOx,
NH3, SO2) may also enter foliage through stomata, and perhaps in
sufficient quantities for the slowest growers to significantly reduce dependence on the indumentum (e.g., Ziereis and Arnold 1986). Vapor accounts
for mercury contamination and perhaps some of the burdens of certain
additional ‘technological metals’ discussed below. However, experiments
conducted to date dealt exclusively with absorption from prepared solutions over intervals that extended from less than an hour to several months.
Individual cells to whole plants were targeted.
Trichomes of Pitcairnioideae exclusive of one genus possess relatively
low-grade organization and exhibited little, if any, capacity to absorb ions,
according to autoradiographs obtained from the few Pitcairnia species
examined so far (e.g., Benzing et al. 1976; Fig. 2.5). Brocchinia constitutes
the exception, perhaps reflecting an erroneous taxonomic assignment, or,
in some of its species, habits and ecology conducive to this kind of trichome
involvement that occur nowhere else in the subfamily. Novel trichome
structure, which nevertheless varies substantially among the fewer than 20
described species, clearly distinguishes Brocchinia from the balance of
Pitcairnioideae (Fig. 2.5).
Absorptive trichomes accompany carnivory, myrmecotrophy and litter
use in Brocchinia (Figs. 5.2F,G). Trichomes born by Type One B. prismatica also accumulated label in assays using 3H-leucine, while those of litterimpounding B. tatei and B. micrantha were inactive by comparison.
Perhaps significantly, trichomes occur at the highest densities and cover the
highest percentages of the leaf surface where they assist uptake by carnivorous B. reducta (Givnish et al. 1997; Chapter 9; Table 9.1). Still, the presence of absorbing hairs on nonimpounding relatives like B. prismatica and
Steyerbromelia diffusa (also Type One) suggest that closer study would
reveal some capacity for trichome-mediated nutrition in all of the
Brocchinia species equipped with phytotelma.
Ananas comosus provides the most complete picture of how the trichome
serves at least some Bromelioideae. Sakai and Sanford (1979) reported that
its leaf bases bear overlapping scales, each comprised of a living, two-celled
stalk topped by a multicellular, dead shield. Numerous plasmodesmata
connected the dome cell with the underlying mesophyll as in Brocchinia and
Tillandsioideae. Additional shared structure changed with conditions.
232
Mineral nutrition
Similar to Dolzmann’s (1964, 1965) observations on Tillandsia usneoides,
leaves fixed while surface-dry featured layers of electron-dense material
between the plasmalemma and walls and abundant granules around the
periphery that periodic acid–Schiff base reaction indicated was a polysaccharide. Neither substance was apparent in samples that had been presoaked in water for 12 h. Larger numbers of smaller mitochondria with
swollen cristae further suggested altered cell status likely related to absorptive function. Dictyosomes and spherosomes remained scattered as before.
Trichomes lining the phytotelmata of at least some Type Three
Bromelioideae promote nutrition, according to several studies. Resolution
varied with the experiment. Amino acids and bovine serum albumin added
to the tanks of Aechmea bracteata diminished over time as indicated above
(Benzing 1970b). Microbes probably metabolized some of these supplements, but could not explain higher leaf N at the end of the runs. Two
studies (Burt and Benzing 1969; Nadkarni and Primack 1989) designed to
compare the absorption of several radionuclides provided as inorganic salts
by roots vs. shoots confirmed foliar involvement, although not necessarily
via trichomes. Several ornamental taxa fertilized in similar fashion to determine optimum culture (Sieber 1955) proved about as competent to feed by
either route. Autoradiography demonstrated 3H from labeled leucine in the
trichome stalks of Neoregelia sp., although several Tillandsioideae treated
at the same time exhibited more impressive accumulations (Benzing et al.
1976).
Brocchinia reducta, the best-known member of its ecologically diverse
genus, provides the most thorough appraisal of the structure and function
of any bromeliad trichome (Owen et al. 1988, 1991; Owen and Thomson
1988). Cells comprising the distal portion of the atypically goblet-shaped
organ, about 30 in a radial array, remain alive following maturation if
bathed by impounded fluid (Figs. 2.5A,B, 5.2F). A labyrinthine array of
electron-dense and more translucent zones mark the outer tangential and
radial boundaries of these distal-most cells, especially those that interface
with the phytotelmata (Fig. 2.5C,D). Canaliculate spaces represented by
the translucent regions disappeared if leaf surfaces were dry prior to
embedding in plastic.
Studies conducted to determine the permeabilities of the Brocchinia
reducta trichome proved especially enlightening. Dextrans conjugated with
fluorescent dyes confirmed the presence of pores in hydrated cap cell walls
with Stokes diameters of at least 6.6 nm, sufficient clearance for small to
medium-sized proteins or the partially hydrolyzed products of larger molecules. Plant secretions, including enzymes, might pass in the opposite direc-
Involvement of foliar trichomes
233
tion through the same channels. Vigorous protein synthesis would explain
the numerous polysomes in the adjacent protoplasts (Owen et al. 1988).
However, final assessment of trichome involvement in carnivory in B.
reducta requires determination of whether the plant or its symbiotic
microbes digest the prey.
Diffusing lanthanum confirmed the existence of an apoplastic conduit
extending from the phytotelma through the trichome to the underlying
mesophyll. Lucifer yellow, a fluorescent tracer, revealed the parallel symplastic pathway and, for the first time, endocytotic uptake of a nontoxic
substance by a walled, whole cell (Owen et al. 1991). Again, entry occurred
exclusively via the distal stalk cells after passage through gaps in the thin
cuticle (Fig. 2.5C). After traversing the canaliculi, label accumulated in the
adjacent plasma membrane, specifically in coated invaginations, prior to
migration into the cytosol. Owen et al. (1991) also detected Ca-precipitated
pigment in coated and partially coated vesicles, either free in the cytosol or
associated with the dictyosomes. Occasionally, accumulations occurred in
tubular and swollen elements of the smooth endoplasmic reticulum.
Fluorescence in the lumina of the dictyosomes accorded with the passage
of label through the Golgi apparatus.
Tested amino acids performed differently (Owen and Thomson 1988).
Leucine moved most freely through the system, eventually emerging as a
visible, insoluble osmium/leucine complex within the cristae of mitochondria, on the surface of lipid bodies, and less often in spaces associated with
the tubular invaginations of the plastid interenvelope. Glycine only penetrated to the matrix of the mitochondria in some cells. Arginine-treated trichomes contained complexed deposits in the labyrinthine channels alone,
perhaps because the plasmalemma lacks capacity to transport this more
structurally complex metabolite.
Nyman et al. (1987) demonstrated metabolic involvement in the accumulation of numerous amino acids through the intact leaves of Tillandsia paucifolia, presumably via trichomes. More extended studies illustrated that
this same Type Five epiphyte, minus its few roots, can concentrate a variety
of inorganic ions (Benzing and Renfrow 1980). Daily 0.5-h immersion in
nutrient solutions brought about a 20-fold increase in P content within 120
days. Levels of N and K also rose, but not as much. Identical contact with
equimolar solutions (1025–1027 M for trace elements) killed every individual within 60–90 days. Post hoc examination revealed Cu concentrations
(dry weight) up to 20-fold above those in controls; Zn and Mo contents also
increased substantially (Table 5.3). Concentrations of B, Fe and several
macronutrients changed little or not at all.
234
Mineral nutrition
Figure 5.5. Uptake of three plant nutrients by leaf discs of five bromeliads over 3 h.
Numbers over the bars depicting P accumulation represent the combined densities
(mm22) of trichomes on both leaf surfaces (after Benzing and Pridgeon 1983).
Additional experiments using labeled inorganic nutrients compared
more than 20 Bromeliaceae representing every ecological type and all three
subfamilies (Benzing and Burt 1970; Benzing and Pridgeon 1983).
Autoradiography differentiated another set of subjects by subfamily and
architecture within Tillandsioideae (Benzing et al. 1976). In the first
instance, segments of leaf blades of several Type Five Tillandsia accumulated more 45Ca, 32P, 35S and 65Zn from treatment solutions during 3–12-h
runs than did comparable samples excised from sparsely trichomed, tankforming Catopsis nutans (Benzing and Pridgeon 1983; Fig. 5.5). Tested
Bromelioideae and Pitcairnioideae also exhibited lower affinities for the
ions provided. Following exposure to 3H-leucine for 0.5 h, the trichome
stalks of all treated Tillandsioideae contained abundant 3H, whereas the
adjacent epidermal cells and nonliving shields remained unaffected (Fig.
5.2H). Trichomes of the included Bromelioideae and Pitcairnioideae took
up much less or no label (except for several Brocchinia species as indicated
above).
Without question, the foliar trichome has played a decisive role in bromeliad radiation. Why this appendage acquired its capacity for absorption
remains unclear and controversial. Conceivably, nutritional insufficiency
rather than drought was responsible for the evolution of the absorptive
capacity that allows extant Bromelioideae and Tillandsioideae to play so
many important roles and anchor on diverse kinds of often unyielding sub-
Nitrogen nutrition
235
strates. Pittendrigh (1948) suggested arid habitats, but access to nutritive
ions in phytotelmata may have been more influential (Benzing et al. 1985;
Chapter 9). A reconstructed phylogeny would help determine how carnivory, myrmecotrophy and animal-assisted saprophytism relate to one
another and to the absorbing trichome, and when and how often each of
these features evolved.
Nitrogen nutrition
Nitrate, sometimes augmented by substantial NH41, constitutes the bulk of
the N supply for most land flora. However, low temperature retards mineralization enough in certain Arctic ecosystems to permit at least one tundra
species to meet about half of its requirement from organic sources (Chapin
1993). Nonmycorrhizal Eriophorum vaginatum (Cyperaceae) took up
several amino acids during experiments designed to test relative availability. Growth was superior on the organic supplements compared with either
NO32 or NH41, in part owing to more favorable absorption kinetics and
only modest capacity to assimilate nitrate. Combined supplies of the most
abundant amino acids in native soils exceeded concentrations of the prevailing inorganic species (2–8 vs. 0.5–1.1 mg Ng21).
Myrmecotrophy, carnivory and the other variations on tank nutrition,
and humic rooting media similar to the substrates that support many
boreal plants suggest that certain Bromeliaceae might also possess special
capacities to utilize organic N. Facility to use nitrate vs. ammoniacal N may
also differ among species depending on the pH of substrates in native habitats. Decomposing litter, excrement from ants and other symbionts, and
digesting prey all increase the variety of N-containing compounds adjacent
to root systems and foliar trichomes. Those amino acids Picado (1913)
added to the tanks of some Costa Rican bromeliads, the similar demonstration by Benzing (1970b), and Owen et al.’s (1988) findings on Brocchinia
reducta trichomes all indicate permeability and physiology consistent with
unusual N nutrition.
Certain Bromeliaceae possess distinct capacities to utilize oxidized vs.
reduced inorganic N in aseptic culture, but these findings must be considered relative to conditions in situ to assess possible biological significance
(Benzing 1970c). Ammoniacal nitrogen usually prevails at low pH, while
nitrate predominates under more neutral conditions. Humus-rich substrates support many of the terrestrials (e.g., Cryptanthus, Orthophytum),
and the bryophyte-based mats at cooler, wetter montane sites harbor a relatively sparse microflora in addition to sometimes abundant Tillandsioideae
Mineral nutrition
236
Table 5.16. Growth by three bromeliads representing three ecological types
on diverse sources of N plus all other required nutrients expressed as percent
dry weights relative to those of 2N controls. The N sources were provided
at 0.002 M nitrogen equivalent concentrations
Aechmea bracteata
(Type III)
Vriesea jonghii
(Type IV)
Pitcairnia andreana
(Type I)
251
231
266
83
253
245
177
167
244
80
164
151
217
215
170
138
169
43
152
117
110
53
161
44
106
63
105
140
244
224
249
78
129
83
91
89
252
94
162
86
76
181
(NH4)2SO4
KNO3
(NH4)2SO4 1KNO3
Alanine
Asparagine
Aspartic acid
Citrulline
Glycine
Glutamine
Glutamic acid
Ornithine
Tyrosine
15 amino acids
Urea
Source: After Benzing (1970c).
(Vance and Nadkarni 1990). Phytotelm types may experience preponderances of NH41 because the fluids they impound typically range between
about pH 3.5 and 6.0. Finally, NH41 frequently exceeds NO32 in precipitation (e.g., Coxson and Nadkarni 1995).
Different responses of the seedlings of five bromeliads representing
Types One (Pitcairnia andreana, Puya mirabilis) and Three and Four
(Aechmea bracteata, A. recurvata, Vriesea jonghei) to aseptic media containing amino acids, amides, urea and NH41 and NO32 salts as sole sources
of N may reflect the compositions of the supplies available to these plants
in situ (Benzing 1970c; Table 5.16). Phytotelm types developed rapidly on a
greater variety of organic sources than soil-rooted forms. Glutamine consistently promoted growth compared with N-free controls, and usually
about as effectively as NH41 and NO32 alone or combined. Other amino
acids (e.g., alanine, glutamic acid) were inhibitory. Aechmea bracteata,
which regularly hosts ant colonies and collects litter in phytotelmata,
thrived on the greatest number of organic species (Fig. 2.4G). Aechmea
recurvata and Vriesea jonghei responded somewhat similarly and the two
Type One Pitcairnioideae proved least able to substitute organic for inorganic N.
Nitrogen nutrition
237
Figure 5.6. Course of nitrate reductase induction in the roots and foliage of Vriesea
hieroglyphica fed Ca(NO3)2 through the same organs (after Nievola and Mercier
1996).
Mercier (1993) recorded a more extensive array of plant responses to N
supply using glutamine and urea, vs. reduced and oxidized inorganic
sources in sterile culture. Seedlings of Pitcairnia flammea and Vriesea
philippo-coburgii represented Types One and Four respectively, while
Tillandsia pohliana (Type Five) added one of the most leaf-dependent bromeliads for comparison. Together, NH41 and NO32 always promoted vigorous growth, as did glutamine. Concentrations of phenolics, free NH41,
and various growth factors in tissues also varied among the three subjects
depending on the N source. Root formation in Vriesea philippo-coburgii
and Tillandsia pohliana was delayed by (NH4)2SO4. Conversely, Ca(NO3)2
and NH4NO3 stimulated growth, perhaps consistent with measured
changes in the relative concentrations of endogenous cytokinins.
Whether or not the biota in phytotelmata generate more or less NH41
compared with NO32, Vriesea hieroglyphica specimens fed the second
source either through the root system or through the shoot developed considerable nitrate reductase activity (Nievola and Mercier 1996; Fig. 5.6).
238
Mineral nutrition
However, induction occurred more slowly (4 vs. 2 h) in roots than in foliage.
The type of supply (e.g., Ca(NO3)2 vs. (NH4)2SO4) also influenced the activities of additional N-processing enzymes, namely glutamate dehydrogenase
(GDH) and aspartate aminotransferase (AAT) in Pitcairnia flammea,
Vriesea philippo-coburgii and Tillandsia pohliana. Differences consequent
to feeding were most pronounced in the electrophoretic mobilities of
GDH. Urea inhibited AAT in terrestrial Pitcairnia flammea but promoted
activity in epiphytic Tillandsia pohliana. While somewhat difficult to relate
to plant habits and conditions in nature, Mercier’s findings demonstrate
distinct N relations among three ecologically divergent bromeliads.
Architecture and nutritional economy
Additional aspects of morphology beyond the inflated leaf bases, that
when closed favor myrmecotrophy and when open the capture of litter and
its processing by symbionts, also promote bromeliad nutrition. Benefit
from these other arrangements accrues through increased mineral-use
economy. Once again, the most conspicuous examples come from
Tillandsioideae. Especially noteworthy are the Type Five species, which collectively constitute an evolutionary grade whose members probably
emerged repeatedly from more mesic stock characterized by phytotelm
architecture (Gilmartin and Brown 1986; Chapters 9, 12 and 13).
Tillandsioideae include species that possess well-developed to nearly
nonexistent root systems well suited respectively for relatively equable to
harsh anchorages. Shoot organization parallels this trend with progressive
miniaturization accompanied by either reduced numbers of vegetative
nodes per ramet or greater caulescence and expanded leafiness (Fig. 2.1).
Tillandsia usneoides exhibits the most abbreviated of all the derived bauplans with its nearly root-free ramet, which at maturity bears just one leaf
and a single prophyll prior to the appearance of a solitary, terminal flower
(Figs. 2.1, 2.10E).
Structural reduction illustrated by Tillandsia subgenus Diaphoranthema,
which includes T. usneoides, and T. bryoides (a notably caulescent form;
Fig. 2.1), prompted Tomlinson (1970), among others, to invoke heterochrony without comment about causes, mechanisms or consequences.
Improved material economy offers a plausible explanation for this phenomenon because it accords with two unrelated growing conditions, and the
fundamental capacity of vascular flora to emphasize root or shoot development according to plant needs. Moreover, current growing conditions
indicate that these bromeliads are ideal candidates for the kind of hetero-
Architecture and nutritional economy
239
chrony that explains the array of body plans exhibited among extant
Tillandsioideae.
Two benefits potentially accrue to any vascular plant that, by virtue of
morphology and habitat, requires just one rather than two organ systems
to conduct basic vegetative functions, viz. absorb water and essential ions
and harvest photons and CO2. Plants so organized can deploy biomass in
patterns unavailable to more conventionally organized flora. Plants with
shoots, but few or no roots, also potentially require less time to mature than
others obliged to allocate resources more evenly between green and nonproductive (root) tissue owing to the principle of compounding interest. A
shortened life cycle in turn favors rapid population growth, which, combined with the enhanced inputs for propagules made possible by rootlessness, increases capacity to exploit habitats that impose relatively high rates
of mortality on juveniles (e.g., Cole 1954; Benzing 1981a).
More succinctly, economies of time and material inherent to the body
plan of the Type Five bromeliad should promote fitness wherever drought
or infertility slow carbon gain and scattered safe sites, disturbance or any
other agency that kills large numbers of pre-reproductive individuals
mandate compensatory (elevated) fecundity (Benzing 1978a). Dry-growing
Tillandsia experience some of the most stressful (nonproductive) of all the
environments colonized by land flora, and they often root on unstable
media that mandate rapid plant cycling. Small, mobile seeds, a consistent
characteristic of Tillandsioideae, also accord with the scattered and ephemeral nature of bark, which is the substrate these plants use more frequently
than any other.
The multifunctional shoot combined with a largely vestigial root system
not only help explain why Bromeliaceae dominate so many arboreal and
lithic floras in the American tropics, but also abrogate a basic principle of
morphology. Plant success on land beginning some 450 million years ago
required diverse novelties (e.g., vascular tissue, cuticle), and that the sporophyte be reorganized to accommodate two rather than the single ancestral
aquatic medium. Part of the plant body now occupied an energy-rich, but
drying, environment, namely the atmosphere, while the other portion was,
and continues to be for most modern flora, relegated to dark, moister and
more nutritive space. Exceptions include the fully exposed epiphyte and lithophyte that once again inhabit relatively uniform ecospace where the longstanding need for shoot/root system differentiation no longer applies. Similar
opportunities and corresponding conditions mark the more retrograde flora
(e.g., rootless Ceratophyllaceae), and with fewer functional trade-offs given
the more forgiving nature of water vs. the atmosphere as a growth medium.
240
Mineral nutrition
Whatever advantages prompted evolution from Type Four to Type Five
status, ecological latitude diminished in certain other respects as stress-tolerance increased. Absorptive trichomes with large, hydrophilic shields complicate life in shady habitats and preclude existence in overly humid ones
(Benzing et al. 1978; Fig. 4.11; Table 4.8). Additionally, rootlessness may
exacerbate certain metabolic problems, particularly ion balance, specifically the need to dispose of excess of either H1 or OH2, depending on the
N source (oxidized or reduced). Many plants avoid damaging buildups by
dumping potentially toxic inorganic ions through extensive root systems
(Raven 1985, 1988). Type Five Tillandsioideae may avoid this complication
by growing slowly or perhaps they render these products harmless by some
other mechanism.
Bromeliads as air quality monitors
Instruments provide most of the data on air quality; flora constitute a
cheaper alternative, but are not without disadvantages. Plants differ in their
avidities for certain naturally occurring and anthropogenic substances
depending on the species, the physiological status of the specimen, growing
conditions and a host of additional variables. For example, assays of contaminated foliage reflect microrelief and electrical attractions between
plant surfaces and charged aerosols. Coatings on foliage and other organs
continuously change as surfaces saturate independent of the mix of substances moving around them. At best, the composition of plant tissue offers
a biased, time-averaged record of the chemical environment of that organism; it does not mirror the performance of the mechanical device designed
to strip air of all of its contaminants.
Nevertheless, absolute and relative concentrations of certain components in ashed tissue represent useful data. For example, abnormally elevated levels of certain technological metals indicate anthropogenic
contamination. Ratios of Na to Al or to some other element abundant in
inland soils signal marine influence. Elements that fluctuate less in concentration relative to tissue dry weight than to percent ash, a value particularly
sensitive to the thickness and composition of coatings on plant surfaces,
are probably nutrients. Factor and principal component analyses more precisely define associations of elements that distinguish anthropogenic from
natural sources, and differentiate constituents essential for life from those
potentially harmful to organisms.
A substantial literature indicates that lichens exceed most vascular flora
as worthwhile devices for air quality surveillance, and reasonably so. Most
Bromeliads as air quality monitors
241
higher plants root in soil, and hence contact a source of many of the same
elements that concern the environmentalist. Additionally, lichens often
respond more sensitively to the gases and metals that pollute ecosystems
and threaten public health. Industrial and automotive emissions already
account for the collapse of formerly dense populations of lichens near
many industrial and urban sources. Various conifers also exhibit exceptional susceptibility to certain air pollutants (e.g., O3), but being essentially
nontransportable as adults, are useless for many applications.
Unlike most vascular flora, the epiphytes are small and easily relocated.
They also grow above ground and subsist on nutrients from aerial rather
than soil-based sources. Furthermore, pollutants impact some of these
plants as much as they do the lichens, but with broader possibilities to
quantify the effects. Stomatal conductance and associated physiology
unique to vascular flora offer special opportunity for inexpensive and nondestructive diagnosis of sublethal injury and subsequent plant recovery.
Spanish moss was the first bromeliad to provide information on atmospheric chemistry, and it and several congeners continue to stock most of
the surveys that employ vascular epiphytes. Wherry and Capen (1928)
examined ashed shoots for signs of contamination in Florida. Martinez et
al. (1971) and Robinson et al. (1973) used the same approach and bromeliad to determine that lead from auto exhaust occurred at extraordinary
concentrations in a number of roadside collections; T. usneoides also
revealed Ni contamination via aerosols near a battery plant in South
Carolina (Carcuccio et al. 1975). Schrimpff (1981) employed T. recurvata to
map polluting metals, pesticides and aromatic hydrocarbons at two locations in Colombia, South America.
Burdens of several metals in Spanish moss increased toward a petrochemical complex in southeast Texas (Benzing 1989). Total S in the foliage of
Tillandsia balbisiana, T. paucifolia and T. utriculata reached highest concentrations in collections taken closest to the urbanized coast of southeastern
Florida (Benzing and Bermudes 1992). Spanish moss revealed alarming contamination from Hg vapor emanating from a gold refining operation in
Brazilian Amazonia (Calasans and Malm 1994). Exposures of a few months
within and near processing sheds elevated concentrations from less than one
up to 60 ppm! Contaminated clothing worn by the employees who boil off
metallic Hg spread the risk off-site. Calasans and Malm (1994) also placed
baskets of T. usneoides inside the electrolysis chambers of a chlorine-soda
facility in Brazil for 15–68 days and recovered Hg up to 13000-fold
(30–35 mm g21 dry weight) above levels in control plants. Other samples maintained outside the factory contained 5–175 times ambient concentrations.
242
Mineral nutrition
Experiments and horticultural practice indicate extraordinary responses
among Bromeliaceae to a variety of toxic substances. Arboriculturalists
formerly sprayed lead arsenate to selectively kill T. usneoides and T. recurvata infesting shade and orchard trees in Florida. Copper salts continue to
serve the same purpose. For example, two applications during one growing
season of Cu(OH)2 at 35g l21 eliminated T. recurvata on crape myrtle in
southern Louisiana (Holcomb 1995). More costly Cu-based fungicides
have been employed for many years to control ballmoss in Texas (Shubert
1990). Caldiz and Beltrano (1989) and Bartoli et al. (1993) achieved 100%
kills of T. recurvata and T. aeranthos with little damage to Argentinian
hosts using the herbicides atrazine and simazine. Experiments such as those
of Benzing and Renfrow (1980) demonstrated susceptibility to overloads of
several metallic micronutrients (Table 5.3).
Tolerances to corrosive gases varied according to the treatment.
Tillandsia balbisiana, T. paucifolia, T. recurvata and T. utriculata survived
6-h exposures to O3 (0.15–0.45 ppm) and SO2 (0.3–1.2 ppm), applied alone
and combined, in continuously stirred tank reactor exposure chambers
(Benzing et al. 1992). Neither DH1 nor foliar conductance diminished
during or immediately following these comparatively short nocturnal runs.
Many of the test subjects flowered the following year in greenhouse culture,
indicating no significant delayed injury. Remarkably low diffusive conductances even for a CAM plant probably reduced exposure of the mesophyll
enough to avoid damage over such short runs. Fumigated at 3.8–4.0 ppm
SO2 for several days, T. aeranthos exhibited considerable leaf necrosis
(Arndt and Strehl 1989).
Shacklette and Connor (1973) and Connor and Shacklette (1984) conducted a study that exceeded all the others using bromeliads in its geographic and chemical dimensions. Briefly, factor analysis identified three
series of elements that accounted for almost three-quarters of the variation
in log concentrations in the ash of 123 samples of Spanish moss collected
across the southeastern United States. Aluminum, Ba, Ca, Co, Ga, Fe, Mn,
Ti, Yb and Zr constituted a pedological association present in samples
from all sites. Three more elements (Ca, Na and Sr) that occur abundantly
in less widely distributed substrates were associated with, but somewhat
distinct from, the other 10. Inconsistent proportions between the concentrations of members of the first series of 14 elements and total plant ash
suggested enrichments by wind-deposited particles. Plant absorption contributed far less.
Distributions of several of the elements in this first series among the
samples indicated different terrestrial sources. Limestone dust from
Bromeliads as air quality monitors
243
roadbed fill and quarrying operations probably produced the frequent, proportionally high values for Ca and Sr relative to Al. Collections with the
highest Na:Al ratios usually came from Florida and the Gulf and Atlantic
coast sites (Shacklette and Connor 1973) to the west and north, indicating
strong marine influences. Presumably coatings on leaves near the ocean
contained more sea salt and marine limestone dust, whereas materials
derived from terrestrial soils predominated farther inland.
Nine elements (B, Cr, Cd, Cu, Li, Ni, Pb, V and Zn) formed a second
series made up principally of the technological metals. Generally low logarithmic correlations of these constituents with log Al in ash suggested that
sources other than soil accounted for their occurrence in the samples. Lead
concentrations peaked near heavily traveled highways, as noted in some of
the other studies with T. usneoides (e.g., Martinez et al. 1971). Occurrences
of Zn, Cu and Cd in the same vector fan of the Connor and Shacklette
varimax model further indicated that these plant constituents originated
from vehicles, most likely from lubricants, tires and abraded body parts, if
not exhaust. The same explanation probably applied to Cr and Ni.
Boron, Li and V emerged at the other end of the technological metals
vector fan. Residual oil used for heating and power generation, in addition
to some soils, represent potentially major sources of V in the southeastern
United States (Schroeder 1970; Zoller et al. 1973). Glass manufacture
employs considerable Ba and Li, and Cd, Cr, Ni, V and Zn indicate other
industrial processes. Coal-burning volatilizes many metals. Connor and
Shacklette concluded that, unlike the soil–element association, anthropogenic aerosols rather than absorbed natural particulates accounted for the
extraordinary accumulations of technological metals.
A geographic dimension further differentiated the series one and series
two metals. Substratum-related elements exhibited broad regional (e.g.,
landward vs. coastal) trends in their proportional concentrations in
Spanish moss, while the technological metals showed more localized occurrences reflecting nearby discrete sources. Sheline and Winchester (1976)
also identified characteristic combinations of elements in samples of
Spanish moss in northern Florida, which they considered consistent with
plant uptake of aerosol particles.
Magnesium, P and K formed a third varimax series in Connor and
Shacklette’s study, distinguished from the others by pattern of occurrence
and status as plant macronutrients. Log concentrations of all three elements varied independently of the other 23 surveyed and percent ash,
reputedly because the bromeliad controlled their accumulation according
to need.
244
Mineral nutrition
Two inherent characteristics probably account for the remarkable
affinities Type Five bromeliads exhibit for diverse substances: dependence
on the atmosphere rather than soil for nutrients, and a relatively nondiscriminating organ (the foliar trichome) for absorption. Capacity to scavenge often scarce ions is essential for these plants. However, the same
mechanisms apparently promote toxic accumulations of required (e.g., Cu)
and other substances if supplies become too enriched. Consequently, oligotrophic members of Tillandsia, probably more than most vascular flora,
offer exceptional opportunity to monitor air quality. However, as slowgrowing CAM plants, these bromeliads do not match the sensitivity of
much other vegetation (e.g., certain crops) to chronic exposures to several
common corrosive gases.
6
Reproduction and life history
D. H. B E NZ ING, H. LUT HE R AN D B. BEN N ETT
Reproduction is central to the evolutionary theme of this volume, but an
uneven literature precludes a balanced treatment. Numerous reports deal
with issues like pollination, while a host of other subjects (e.g., breeding
systems) remain largely ignored. Reasons for the disparity range from
botanical tradition to differences in the ease and costs of pursuing speci® c
kinds of inquiry. Publications on ¯ ower, fruit and seed structure exceed all
others on bromeliad reproduction to the extent that even a reasonable overview of this material requires a separate chapter (Chapter 3). Issues such as
seed dispersal and gene ¯ ow and demography, along with the other phenomena that in¯ uence reproductive success and evolution, receive ® rst priority here.
A single, fundamental bauplan and life under often stressful growing
conditions help explain why most Bromeliaceae share several de® ning
aspects of natural history. Life cycles usually proceed slowly and several
years to decades pass before the typical bromeliad produces the ® rst of
usually multiple seed crops (iteroparity) from branched, determinant
shoots (Fig. 2.3). About half a dozen genera in Pitcairnioideae and
Tillandsioideae also include one or more members that fruit just once (the
monocarps) after some 15 to many additional years devoted solely to
resource accumulation (Figs. 2.3B, 14.2C). Genets of the iteroparous types
that survive long enough fragment into multiple, autonomous units, and
especially successful genets of the most aggressive terrestrials dominate
extensive habitat (e.g., Brokaw 1983; Murawski and Hamrick 1990).
Numerous less routine aspects of reproduction and life history accommodate speci® c Bromeliaceae to speci® c kinds of ecospace and growing
conditions. Fruit and seed morphology indicate dispersal by wind, perhaps
¯ owing water, several groups of vertebrates, ants and possibly some
other invertebrates. Breeding systems and pollinators also distinguish
245
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Table 6.1. Representative Bromeliaceae and their putative pollinators
Species
Aechmea magdalenae
Aechmea distichantha
Alcantarea regina
Ayensua uaipanensis
Billbergia horrida
Billbergia porteana
Dyckia ferox
Encholirium glaziovii
Fascicularia bicolor
Guzmania lingulata var. minor
Hohenbergia blanchetii
Nidularium procerum
Pitcairnia corallina
Pitcairnia loki-schmidtiae
Pitcairnia brevicalycina
Puya alpestris
Puya ferruginea
Tillandsia duratii
Tillandsia argentea
Tillandsia utriculata
Vriesea carinata
Vriesea in¯ ata
Vriesea atra
Werauhia gladioli¯ ora
Pollinator
Reference
Hummingbirds
Hummingbirds
Bats
Bats
Hummingbirds
and bees
Hummingbirds
Hummingbirds
Bats
Hummingbirds
Hummingbirds
Hummingbirds
Hummingbirds
Hummingbirds
Bats
Insects
Hummingbirds
Bats
Moths
Small moths
Hummingbirds
and small moths
Hummingbirds
Hummingbirds
Bats
Bats
Murawski and Hamrick 1990
Bernardello et al. 1991
Vogel 1969
Varadarajan and Brown 1988
Ruschi 1949
Ruschi 1949
Bernardello et al. 1991
Sazima et al. 1989
Mez 1896
Stiles 1978
Ruschi 1949
Ruschi 1949
Varadarajan and Brown 1988
Vogel 1969
Varadarajan and Brown 1988
Johow 1810
Vogel 1969
Bernardello et al. 1991
Gardner 1986a
Gardner 1986a
Ruschi 1949
Ruschi 1949
Vogel 1969
Vogel 1969
populations, sometimes even conspeci® cs. Nectar-seeking birds service
many Bromeliaceae, and moths and bats transport pollen for some of the
others, as do additional kinds of insects and here and there a nonvolant
mammal. At another extreme, the occasional population routinely self-pollinates, sometimes via cleistogamy. Interest in asexual reproduction has
grown in recent years, and several preliminary reports indicate greater
variety than expected for plants with such a uniform body plan.
Pollination
Diverse fauna, but predominantly birds, set the fruits of Bromeliaceae
(Table 6.1). However, few accounts provide the additional data necessary to
determine how pollinators affect the structure of plant populations, in¯ uence the quality of the resulting offspring, or affect the evolution of the
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247
¯ ower. Gardner (1984, 1986a,b) conducted one of the most provocative
inquiries, drawing on her extensive knowledge of Mexican Tillandsia.
Other authorities choose various Pitcairnioideae, while Bromelioideae
remain least studied of the three subfamilies. Gardner' s descriptions and
analyses provide a starting point to consider the breeding mechanisms of
Bromeliaceae, but ® rst we need some background on this remarkable genus
and its subfamily (Chapters 12 and 13).
Tillandsioideae
Tillandsia (sensu Smith and Downs 1977) contains over 500 described
species according to the latest count (Luther and Sieff 1996; Chapter 13).
This tally will surely grow, although not the size of Tillandsia per se if the
views of several authorities prevail. Smith and Downs (1977) listed just 410
species in seven subgenera and one of these segregates, Pseudocatopsis, has
already been elevated to Racinaea by Smith and Spencer (1992). Additional
components (e.g., subgenus Pseudalcantarea; Beaman and Judd 1996) will
likely also prove untenable as currently conceived, in this case owing to convergence on a similar chiropterophilous ¯ oral syndrome (Fig. 3.3M). The
paraphyletic status of Vriesea and the affinities of several other taxa (e.g.,
Catopsis and Glomeropitcairnia) that stand well removed from core
Tillandsioideae further underscore the need to better resolve Smith and
Downs' s organization of this subfamily (see Chapters 12 and 13).
Vriesea (two subgenera, .225 species) closely parallel Tillandsia in architecture, geography and ecology, with formal assignment to one or the other
taxon based wholly on the presence or absence of petal scales (Fig. 3.1B).
Even Smith and Downs (1977) occasionally challenge the utility of their
key character (e.g., recognition that T. pabstiana5V. drepanocarpa despite
the absence of scales). But whatever the taxonomic fate of Tillandsia vs.
Vriesea, populations currently assigned to these two genera and perhaps
several others collectively constitute one of the largest assemblages of
closely related bromeliads. Moreover, parts of this clade exhibit signs of
continuing, active radiation.
Plants representing many different species have been hybridized in
culture, and additional combinations are spontaneous (Table 6.2).
Frequent sympatry and substantial ecological equivalence, particularly
among the epiphytes, further suggest evolutionary youth. Guzmania
(.150 species) populate everwet forests of the Colombian Chóco with
about 40 described species, many sympatric and scarcely distinguishable by
vegetative characteristics or substrates. Most important for our purposes,
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Reproduction and life history
Table 6.2. Some hybrids involving Tillandsia
subgenus Tillandsia
Tillandsia brachycaulos3T. bulbosa
T. brachycaulos3T. balbisiana
T. brachycaulos3T. capitata
T. brachycaulos3T. caput-medusae
T. brachycaulos3T. ionantha
T. brachycaulos3T. foliosa
T. brachycaulos3T. mirabilis
T. fasciculata3T. foliosa
T. fasciculata3T. lieboldiana
T. ¯ abellata3Vriesea incurvata
T. ¯ abellata3T. tricolor
T. ionantha3T. schiedeana
T. punctulata3T. krukof® ana
T. jalisco-monticola3T. xerographica
Source: After Gardner (1984).
better-known Tillandsia, especially subgenus Tillandsia, provide exceptional opportunity to consider the in¯ uences of pollinators on cladogenesis, the characteristics of ¯ owers, and the integrity of closely related
populations.
Subgenus Tillandsia, a primarily Mesoamerican assemblage of .150,
mostly epiphytic and often markedly drought-tolerant species, makes up
the second largest (after Allardtia) of the formally recognized segregates
comprising genus Tillandsia. Flowers with slender, tubular, regular to
somewhat zygomorphic corollas, at most ¯ aring modestly, characterize the
entire subgenus (Fig. 6.1A). Nevertheless, Gardner (1986b) was able to
employ shared ¯ oral characteristics to differentiate 85 of its member
species, plus a few similar taxa from Allardtia, into ® ve groups preparatory
to more extensive study. At issue were reproductive biology and systematics, and especially what appears to be an exceptionally high incidence of
multivalent pollination syndromes among members of Group One.
Prominent ¯ oral bracts that enclose ¯ ower buds and young fruits, the just
mentioned narrow petals rolled into a tube, well-insulated, deeply placed
nectar, and exerted sexual organs suggest fundamental ornithophily for
Group One and perhaps the entire subgenus. Different arrangements
prevail elsewhere, especially in much smaller Group Two, which indicate
other primary pollinators (Fig. 6.1A). Overall, as many architectures make
up what appear to be basic ¯ oral themes for the ® ve groups comprising
most of subgenus Tillandsia. Variations on the ¯ oral pattern expressed by
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249
Figure 6.1. Aspects of ¯ owers and seeds of Bromeliaceae. (A) Flower structure
characteristic of Gardner' s (1986b) ® ve groups of species recognized mostly within
Tillandsia subgenus Tillandsia. (B) Flower of Tillandsia punctata demonstrating
light-colored petal tips. (C) Plication of stamen ® lament illustrated from left to right
by Tillandsia gardneri, T. stricta and T. aequatorialis. (D) Seed morphology among
species of Brocchinia.
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Reproduction and life history
all members of Group One demonstrate continuing capacity to evolve as
changing environments reorder the advantages of relying on one vs. other
kinds of fauna, or so it seems.
Certain Tillandsia also demonstrate the in¯ uence of rooting medium and
plant size on breeding system and ¯ ower morphology. The most diminutive
forms (e.g., T. capillaris, T. recurvata), those species that tend to colonize
twigs consistent with their small stature, also often display much reduced,
autogamous ¯ owers (Fig. 3.3C). These species consistently set self-seeds,
sometimes by cleistogamy (T. capillaris; Gilmartin and Brown 1985),
perhaps because they lack capacity to entice fauna to fertilize enough of
what are already reduced numbers of ovules in miniaturized capsules.
Anthers in several cases form a hood above the stigma that at once prevents
outcrossing and assures fruit set (Till 1992a). Additional members of this
highly neotenic subgenus produce showy ¯ owers that emit powerful perfumes (e.g., T. crocata, T. myosura).
Sel® ng also occurs in subgenus Tillandsia, and most conspicuously where
monocarpy rather than small size or ephemeral substrates mandates that
most ovules become seeds (e.g., T. utriculata in Group Two; Fig. 6.1A).
However, variations on the basic ¯ oral plan of Tillandsia subgenus
Tillandsia Group One offer superior opportunity to learn about the evolution of reproductive biology because several of Gardner' s Mexican subjects
illustrate recent or on-going change in this system (Gardner 1982, 1986a).
Sometimes geographic distributions and ecology indicate what may be
related adaptation involving aspects of subjects other than their ¯ owers.
Circumstantial evidence suggests that pollinators currently isolate many
co-occurring populations, and that they also fostered much speciation
within oversized Group One. Tillandsia andrieuxii (lavender corolla,
diurnal anthesis) and T. erubescens (chartreuse, nocturnal), for example,
exhibit such close overall similarity that Mez (1934± 35) considered them
varieties of the second taxon. Tillandsia parryi illustrates a similar pattern
with accompanying changes in ecology that indicate additional change,
perhaps even cladogenesis. Epiphytes quite similar to T. parryi collected
near Monterey, Mexico and described as T. sueae (Ehlers 1991), and similar
plants growing south of Xilitla in San Luis Potosi State, ¯ ower just once
(monocarp) and display lavender corollas that open in midmorning
(Gardner 1982). However, specimens east of the city of San Luis Potosi
occur as iteroparous lithophytes equipped with chartreuse petals that separate at dusk. Winter vs. summer ¯ owering further suggests dependence on
different kinds of pollen carriers.
Certain members of subgenus Tillandsia attract the same kinds of polli-
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251
nators using different variations on the same basic ¯ oral syndrome.
Populations comprising Group One serviced by nocturnal visitors lack fragrances, whereas species elsewhere in the same taxon (Group Three), especially night-¯ owering T. heterophylla, produce powerful perfumes.
Appropriate timing and color clearly suffice for fruit set in Group One,
perhaps rendering osmophores functionally redundant and an unnecessary
investment. Lavender petals among certain members of Group One
become more re¯ ective, hence visible in dim light, simply by accumulating
less anthocyanin (e.g., T. seleriana).
Tillandsia streptophylla uses the same basically ornithophilous syndrome
(large ¯ oral bracts, exerted sexual appendages, tubular corolla, extensive
nectar production) to signal crepuscular and night ¯ iers with densely lepidote, light pink ¯ oral bracts. Deep purple-¯ owered T. punctulata may do
the same even more subtly by displaying a lightly pigmented, exerted style
with matching petal tips (Fig. 6.1B). Little impetus may exist to augment
with odors or other major investments a possibly minor backup arrangement needed only to commit the few gynoecia overlooked by the diurnal
pollinators (birds for T. punctata) that these species target more expensively
and conspicuously (large, bright red and green ¯ oral bracts).
A widely shared feature of ¯ oral development may predispose many
Tillandsia subgenus Tillandsia species to high fruit set and mixed-paternity
progeny. Diurnal ¯ owers typically last about 48 h, extending access to
fauna active after sundown. Similarly, ¯ owers that open during the night
tend to remain turgid into the following day. Related embellishments to
attract night or day ¯ iers vary with the example. Tillandsia roland-gosselinii
represents one extreme by relying on a brilliant, parrot-like combination of
a large, bright red scape and slick green ¯ oral bracts to promote seed set.
For good measure, and normally as a prelude to lavender ¯ owers in similarly colored relatives, the entire shoot becomes scarlet. Finally, and incongruously, emerging petals add a relatively faint, pale chartreuse signal just
before sunrise.
Gardner' s use of ¯ oral characters to segregate 85 species into ® ve groups
revealed ecological correlates, some of which may constrain ¯ oral evolution. Most members of Group One occupy arid habitats, i.e., belong to ecological Type Five, or, if equipped with thinner leaves that impound
moisture (Type Four), constitute relatively xeromorphic members of that
assemblage. Soft, green, essentially glabrous foliage more consistent with
conditions in everwet forests prevails through Groups Two and Three.
However, most of these plants exhibit nocturnal or diurnal anthesis respectively. No comparable information exists for Groups Four or Five (only one
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Reproduction and life history
or two species in each), nor are enough data available to speak with authority about timing for primarily ornithophilous and diurnal Group One.
Factors other than pollinators in¯ uence the evolution of the ¯ ower, and
possibly did so in Tillandsia. Aridity and extended anthesis in addition to
frequent dependence on birds may explain some of the distinguishing ¯ oral
characteristics shared by members of Group One. All of these plants
possess distally broadened and ¯ attened stamen ® laments that, combined
with an apically narrowed corolla, may deter all but legitimate pollinators
± those with long mouth parts like hummingbirds (Fig. 6.1). Alternatively,
aridity, speci® cally its capacity to concentrate nectar enough to impede
extraction, rather than gate-keeping explains the same morphology.
Protogyny prevails in Group One as it does through most of the rest of
the subgenus. Anthers fail to reach the exerted and precocious stigma
except in some autogamous populations where mature organs of both
types extend the same distance beyond the corolla (Fig. 6.1A).
Occasionally, the two-tiered con® guration lasts only a few hours as if to
encourage allogamy after which elongating ® laments brush self-pollen
against any stigma that remains receptive. Fewer than every ¯ ower favors
autogamy by this mechanism in still other species (e.g., T. achyrostachys, T.
concolor, T. capitata, T. matudae), perhaps to relieve plants unable to
mature every potential capsule. Benzing and Davidson (1979) determined
that specimens of T. paucifolia bearing the largest numbers of fruits in
Florida invested exceptionally large proportions of their N and P there,
enough to slow the growth of the next ramet compared with subjects with
some barren ¯ owers.
Mixed ¯ oral syndromes may help account for the relatively frequent
spontaneous hybridizations among some members in Group One (Table
6.2). Tillandsia punctulata, with its white-tipped, purple corolla, noctural
anthesis and bird-attracting bracts, often crosses with diurnal, green-¯ owered (prominent green ® laments) T. krukoffiana in the highlands north of
Puebla, Mexico. However, conclusions about the importance of ¯ owers
and pollinators vs. agencies more remote to this outcome are best drawn
within a broader context. Intensive agriculture in Mexico and Central
America beginning about 4000± 5000 may have encouraged gene
exchange among Tillandsia subgenus Tillandsia populations through the
activities of pollinators that foraged more selectively in pre-agrarian habitats (Gardner 1984).
Uniform chromosome numbers indicate a minor role for polyploidy
during the history of Tillandsia beyond subgenus Diaphoranthema
(Chapter 9). Genetic analyses (see below) of several populations of
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253
Mexican Tillandsia ionantha (Group One) and T. recurvata (subgenus
Diaphoranthema), except for a single triallelic locus in the latter (Soltis et
al. 1987), and Kress et al.' s (1990) less comprehensive analysis (three
enzymes) of Florida T. recurvata, T. usneoides and T. recurvata, support this
hypothesis. Distributions in many instances (e.g., T. fasciculata, T. utriculata) across Mesoamerica into northern South America, and included
ranges of numerous close, more insular relatives (see below), accord with
comparative youth and recent colonizations of separated habitats.
Capacity to readily adopt different pollinators to service often self-compatible ¯ owers and ¯ oral morphology conducive to spontaneous autogamy
(e.g., T. recurvata) probably assisted the exceptional radiation demonstrated by the size of Tillandsia subgenus Tillandsia. Outlying populations
of several species (e.g., T. balbisiana, T. ¯ exuosa in Florida) regularly set
self-fruit, perhaps as founders did to establish populations. Breeding
systems even shift across short distances. Southernmost Florida Tillandsia
balbisiana, for example, produces bright red ¯ oral bracts, whereas members
of isolated outlying colonies farther north at about mid-peninsula develop
little color, yet mostly ripen abundant seeds.
Floral syndromes that unambiguously target insects also characterize
Tillandsia subgenus Tillandsia. Tillandsia utriculata (Group Two) initiates
anthesis after dark with ¯ owers bearing large, creamy petals further distinguished by an apical twist (Fig. 6.1A). The lateral aperture exposes the style
and six stamens with circular, uniformly slender ® laments. Anthers attach in
versatile rather than basi® xed fashion, supposedly to promote sphingophily
(moth pollination; Vogel 1969). Self-compatibility probably describes all T.
utriculata, and sometimes this bromeliad requires no assistance to reproduce. Certain populations in northeastern Mexico mature relatively low percentages of gynoecia (average 33% at seven locations; Gardner 1982, 1984),
while plants in Florida with similar ¯ owers, but paler bracts, set nearly every
fruit. Breeding systems in these outlying populations may re¯ ect depauperate faunas, or, again, bottlenecks effected by autogamous founders.
Like those of Group One, members of Group Three possess large
primary bracts, perhaps owing to a bird-serviced ancestry. Pigmentation
usually follows suit (e.g., T. imperialis, T. ponderosa, T. deppeana), but not
¯ ower structure, which better matches another group of visitors.
Characteristically basi® xed anthers exceed the lengths of those presented
by members of the other four groups, and more pollen is produced. Diurnal
anthesis and corolla shape also signal melittophily (bee pollination). Firm
lavender petals curve gently or roll back to provide a credible landing site
for medium-sized visitors (Fig. 6.1A).
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Reproduction and life history
Petals of zygomorphic-¯ owered T. multicaulis, rather than curving
downward to expose the anthers, twist apically to provide access to nectar
and pollen along one side of the corolla tube much like many Pitcairnia
species (Fig. 3.4K). One petal rolls down the side of the T. deppeana ¯ ower
to again furnish a landing site, presumably for Hymenoptera. Tillandsia
heterophylla (Group Three) alone in subgenus Tillandsia stands out for its
large, leafy-green, glaucous ¯ oral bracts that presumably help guide moths
to the pale, spreading corolla. A spicy, sweet fragrance complements this
sphingophilous arrangement.
Gardner also attributed phalaenophily (pollination by moths) to
Tillandsia tortilis and T. lepidosepala, in part because small, densely lepidote (light-scattering) shoots characterize both species. Imbricate ¯ oral
bracts project a dull, rose-pink hue to highlight the protruding, re¯ exed,
moss-green petals surrounding the uniquely included stigma and conspicuous yellow anthers (Fig. 6.1A). Abundant pollen produced precociously
indicates protandry, a second novelty for subgenus Tillandsia. A long ¯ exible scape (T. tortilis), or characteristic orientation on rocky substrates for
shorter-stemmed T. lepidosepala, positions ¯ owers downward.
Floral variety exceeding that present in subgenus Tillandsia occurs elsewhere in Tillandsia and the rest of Tillandsioideae. Unequivocal chiropterophily in at least two versions and entomophily and ornithophily, much as
previously described, appear repeatedly, as do additional mixed and more
exclusive syndromes for insects and birds (Fig. 3.3). Powerful fragrances,
included rather than exerted sexual appendages, widely ¯ ared white, yellow
and lavender corollas, small, dull bracts, and continuously green shoots
characterize most of the allogamous Anoplophytum, Diaphoranthema and
Phytarrhiza ± species also known as the fragrant tillandsias (Fig. 3.3A,F,I).
Catopsis (.20 species) seems to lack capacity to produce anthocyanins, and
its usually modest-sized, white to yellow ¯ owers (Fig. 3.3H) often emit
pleasant fragrances during the day (e.g., C. paniculata) or night (e.g., C.
nutans). Many Guzmania and Vriesea species ® t the ornithophilous syndrome, as does Mezobromelia (four species).
Van Sluys and Stotz (1995) provided one of the most comprehensive
accounts of ornithophily involving Tillandsioideae by observing Vriesea
neoglutinosa in an open habitat within the Reserva Forestal de Linhares of
Espirito Santo State, Brazil. Records were kept for large and smaller
clumps of plants over a ® ve-day interval during the approximately onemonth period that local plants ¯ owered. Tubular, odorless ¯ owers subtended by red bracts opened before 06.00 hours and secreted nectar most
copiously in the morning and again later in the day before the corollas with-
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Pollination
255
ered. Four species of birds exploited this resource, with greater attention
accorded by territorial Amazilia ® mbriata and Polytmus guainumbi than
trap-lining Chlorostilbon aureoventris and Phaethornis idaliae. Visitation
peaked during the morning, but continued through the afternoon. Patches
offering the fewest ¯ owers received the fewest visits (range 1± 7 per day).
Small compared with large patches also experienced signi® cantly fewer
visits per in¯ orescence (1.33 vs. 1.79). Capsules ripened by plants in small
patches contained fewer seeds than those obtained from the larger clumps
(152.6 vs. 180.5). Similar values obtained by Snow and Snow (1986) for epiphytic V. incurva and V. jonghei in Atlantic Forest led them to conclude that
pollen supply limited local seed production.
Utley (1983) and Vogel (1969) studied Central American thecophylloid
Vriesea species (part of section Xiphion), many notable for bat-attracting,
unusually large, pale, wide-mouthed ¯ owers featuring hood-like arrangements of stamens with oversized anthers (see Fig. 3.5E for a Brazilian
Xiphion). Heavy nocturnal odors help advertise for pollinators, while the
large green bracts primarily protect buds and developing fruits. According
to Utley, derived forms (e.g., V. vietoris, V. leucophylla, V. hainesiorum)
abandoned bats, adopting instead brightly colored in¯ orescences and
diurnal anthesis to utilize birds. Tubular corollas and symmetrical androecia further differentiate ornithophilous from chiropterophilous forms.
Grant (1995a,b) erected genus Werauhia to recognize the close relationship
and distinctness of these unusually large-bodied Tillandsioideae.
Vriesea of the Organ mountains of southeastern Brazil constitute
another exceptionally broad radiation within Tillandsioideae far south of
the ranges of most Tillandsia subgenus Tillandsia. While ornithophily prevails in this second group as well (e.g., V. carinata, V. erythrodactylon with
red/orange bracts and green to yellow petals; Table 6.1), other species lure
unrecorded fauna with fragrant day or night ¯ owers often subtended by
green, deep carmine or dry, brown ¯ oral bracts. Mixed systems characterize several of the more ornamental species as in Mesoamerica. Vriesea
philippo-coburgii bears reddish bracts and yellow day ¯ owers with pleasant
aromas, suggesting versatile syndromes designed for bees and birds as in
some Tillandsia (e.g., T. imperialis).
Night-¯ owering taxa lack bright pigments, producing instead pale to
dark corollas associated with odd scents never reported for Tillandsia.
Flowers of Vriesea longiscapa open at dusk and emit a yeasty grease aroma;
those of nocturnal V. regnellii display even larger, 3± 5 cm, ¯ ared, pale corollas sprinkled with wine-red dots accompanied by another disagreeable
odor. Nocturnal Vriesea unilateralis seems oddly disadvantaged if it has to
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Reproduction and life history
compete for the same fauna given its lack of re¯ ective bracts, a ¯ ared
corolla or a strong scent.
Sazima et al. (1995) con® rmed chiropterophily for six Vriesea species
native to Brazil' s Atlantic Forest. Flower color ranges from cream (V. gigantea), through yellow (e.g., V. sazimae), to brownish red (V. bituminosa).
Stiff, tubular corollas always ¯ are more than those of their bird-pollinated
relatives, open at dusk and begin to collapse by midmorning (Fig. 3.5E).
Anthers bend to the lower side except for V. gigantea where the display
remains radial. Flowers distichously inserted on spikes or branched in¯ orescences with divergent or secund orientations emit nectar tainted with
garlic-like odors. Subtending bracts exhibit shades of green, with or
without dark spots, to deep carmine.
All three of the species with opposite-¯ owered spikes secrete abundant
mucilage, perhaps to deter nectar thieves. Two species of long-tongued,
small glossophagine bats visited one to all six of these bromeliads.
Hummingbirds sometimes harvested residual nectar from withered ¯ owers
after dawn. Additional vrieseas representing section Xiphion and recently
resurrected Alcantarea with similar ¯ oral syndromes indicate even wider
use of bats through this complex of primarily rock and bark-dwelling
Tillandsioideae (Fig. 3.3J). Some larger-¯ owered Alcantarea attract larger
bats, including the stenodermatine frugivore Artibeus lituratus.
Andean Guzmania rival Mesoamerican Tillandsia and Brazilian Vriesea
as subjects to investigate interesting aspects of bromeliad pollination.
Ecuadorian Guzmania alcantareoides parallels certain other bat-pollinated
Tillandsioideae, including Alcantarea (Fig. 3.3J) and Tillandsia subgenus
Pseudalcantarea (e.g., T. viridi¯ ora; Fig. 3.3M; Beaman and Judd 1996).
Large white ¯ owers that open at night further advertise by smelling like
slightly spoiled cabbage. Stamens with outsized anthers, that along with the
petals droop limply by morning, distinguish this species from homoplasious relatives. Bat-attracting Guzmania present either smaller, widely
¯ ared, white, cream or pale green corollas with a conventionally arranged
androecium (e.g., G. coriostachys, G. fosteriana) or, like G. mucronata,
feature a larger, campanulate, green corolla enclosing anthers arrayed
somewhat like those of thecophylloid Vriesea (Luther 1993).
Other species clearly attract other kinds of pollinators, or they defy
assignments to any of the recognized categories. North Andean Guzmania
wittmackii, a day-¯ owering, close relative of G. alcantareoides, produces a
brilliantly colored in¯ orescence to catch the attention of birds, demonstrating once again the plasticity of the ¯ oral syndrome in Tillandsioideae, as
does wide-ranging Guzmania monostachia (autogamous in Florida, mostly
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257
allogamous and more brightly colored beyond). Additionally, some
Guzmania species exhibit combinations of ¯ oral characteristics about as
incongruous as those presented by certain Tillandsia and Vriesea. For
example, white ¯ owers that open around midnight and close soon after
dawn accompany bright orange-rose ¯ oral bracts in Ecuadorian Guzmania
kentii.
Summarizing brie¯ y, Tillandsioideae, especially as demonstrated by the
Tillandsia/Vriesea complex and Guzmania, repeatedly co-opted widely
available pollen carriers that require speci® c plant form and function to
manipulate to set seeds. And where monocarpy, small plant size or ephemeral substrates mandate substantial fecundity, lineages sometimes abandoned pollinators entirely. However, the evolutionary pathways that link
the ¯ oral syndromes remain largely unexplored. Reconstructed phylogenies
would increase insights on historical events and underlying determinants,
for example the extent to which past conditions of ¯ owers and in¯ orescences limited options for pollen dispersal later.
At this point, nonrandom distributions of ¯ oral syndromes among
related lineages suggest that the ¯ oral biology of ancestors in¯ uenced outcomes in descendants, i.e., operated as phylogenetic constraints. Vriesea
psittacina, the type species for its genus, attracts birds, as do many of what
appear to be its closest relatives (e.g., V. carinata), whereas a second group
of conspeci® cs that includes many Vriesea section Xiphion species (now
Werauhia) depend primarily on bats. Many members of a third, natural
assemblage of about 15 saxicolous species ± former Vriesea species (genus
Alcantarea) also native to southeastern Brazil ± mostly attract day-¯ ying
insects with large, perfumed, yellow-petaled ¯ owers (Fig. 3.3J). To what
degree do these patterns re¯ ect inherent barriers to arrangements that
would promote fruit set by other kinds of pollinators?
Pitcairnioideae
Pitcairnioideae rival Tillandsioideae for ¯ oral variety and kinds of pollinators attracted. Also, tendencies to deviate from basic designs characterize
some clades more than others. Reproductive structure and pigmentation
suggest near to complete dependence on insects for Brocchinia,
Cottendor® a, Deuterocohnia, Dyckia, Encholirium, Fosterella, Lindmania
and Hechtia. Conversely, in¯ orescence shape (massive cylindrical to loose
paniculate), diverse ¯ ower colors, radial to zygomorphic corollas, hypogenous to epigenous architecture and observations in situ indicate that more
varied fauna service Pitcairnia and Puya. Pronouncements about Navia
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Reproduction and life history
(probably many syndromes, but no entries in Table 6.1) and some of the
other Guayanan endemics would be premature. At this point, Pitcairnia
more than any of the other pitcairnioid genera compares with Guzmania,
Tillandsia and Vriesea for ¯ oral variety.
Members of Pitcairnia (sensu lato), which is the largest genus (.250
species) within its subfamily, mostly produce elongate tubular ¯ owers with
actinomorphic to moderately zygomorphic corollas, which in the second
case open on one side below the intertwisted petal tips to expose anthers
and stigma (Fig. 3.4F,H,K,L,M). Further embellishments heighten appeal
to birds (red corolla, copious nectar, diurnal presentation; e.g., P. corallina,
P. nubigena), bees (white, yellow to green petals, lesser amounts of nectar,
diurnal opening; e.g., P. brevicalycina, P. albi¯ os), moths (white corolla,
strong odor, abundant nectar, crepuscular/nocturnal anthesis; e.g., P.
¯ ammea var. pallida, P. unilateralis) and bats (pale corolla, unpleasant night
odor, abundant, exposed nectar; e.g., P. loki-schmidtiae, P. palmoides).
Pitcairnia ® mbriato-bracteata surely ranks among the most exceptional
species relative to ¯ oral biology. Reddish ¯ owers born on an equally garish,
sinuous in¯ orescence extend from what by anthesis has become a glutinous
mantle of autodigested, brownish, overlapping ¯ oral bracts. More modest
deliquescence characterizes additional species such as P. arcuata (Fig.
3.4M). Pitcairnia rubro-nigri¯ ora holds the record for striking ¯ ower color
with an almost black-purple corolla contrasting with the bright red calyx.
A comparably red in¯ orescence produced by Pitcairnia corollina snakes
along the ground, exposing foraging birds to terrestrial predators, unless
of course typically precipitous substrates, often cliff sides, reduce this
threat.
Bat-serviced Pitcairnioideae, like comparable Tillandsioideae, manipulate pollinators with scents, abundant nectar, and ¯ owers and in¯ orescences
organized along two patterns. Chiropterphilous Pitcairnia and Puya
display large, well-separated and exposed ¯ owers that open sequentially to
present extended, tubular perianths enclosing often clustered stamens (Fig.
3.4H). Pale to greenish petals that form a more or less wide-mouthed gullet
and musty, nocturnal fragrances further distinguish these taxa from ornithophilous relatives. Conversely, Encholirium glaziovii, the bromeliad with
the most thoroughly documented dependence on bats (Sazima et al. 1989),
like much of the rest of its genus, produces a cylindrical brush-type, many¯ owered (.200) spike 1.5± 1.8 m tall (Figs. 3.4G, 6.2A). For about 10 days,
relatively small, protogynous ¯ owers, each with a wide mouth, persistent
(several days) perigon and stiff, spreading stamens and style, bloom in a
wide acropetal belt (Fig. 3.4G). Enough dilute nectar (4.6% solids) issues
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259
Figure 6.2. Habits and seeds of certain Bromeliaceae. (A) Unidenti® ed Encholirium
in Bahia State, Brazil. (B) Hechtia schottii in Yucatán State, Mexico. (C) Fruiting
monocarpic Tillandsia utriculata in south Florida. (D) Seeds of Tillandsia paucifolia glued in groups of four to the bark of Taxodium distichum in south Florida in
the manner employed to test germination.
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260
Reproduction and life history
from the many simultaneously active gynoecia to ¯ ow down the grooved
in¯ orescence axis.
While chiropterophilous Tillandsioideae typically inhabit dense, humid
montane forests as epiphytes and attract diverse phyllostomids, terrestrial
Encholirium glaziovii more closely parallels similarly pollinated Mexican
Agavaceae. Populations occupy open, semiarid, rocky scrub communities
characteristic of the `campos rupestres' of interior southeastern Brazil
(Fig. 1.4C). Its single bat visitor at the study site, trap-lining Lonchophylla
bokermanni, hovered to collect nectar beginning about 30± 60 min after
dusk. Visits at 5± 40-min intervals consisted of several wide loops around a
spike interrupted by nectar collections that lasted less than a second, yet
long enough to brush pollen on and off the animal' s snout. Several other
¯ ower-dependent bats in the same area ignored E. glaziovii, apparently preferring less exposed food plants in nearby gallery forest and cerrado.
Sphingids and some other moths sporadically visited the same E. glaziovii
¯ owers.
Exclusively Guayanan Navia (,100 species) contains many narrowly distributed lithophytes. The small ¯ owers born by many taxa are probably
inadequate to satisfy the caloric needs of vertebrates. During anthesis
brightly pigmented foliage highlights sessile, somewhat larger ¯ owers born
in the typically capitate sessile in¯ orescences of one group of relatively
robust species. Just the proximal portions of the younger leaves color up to
deep orange/red (e.g., N. arida), or they bleach to brilliant white (e.g., N.
jauaensis). Foliar pigmentation changes little in other instances, that role
falling to the ¯ oral bracts (e.g., N. splendens). Densely congested ¯ owers
with somewhat oversized stigmas and anthers presented above the shoot
suggest anemophily or dependence on small insects in another part of the
genus (Fig. 3.4A± C).
Even fewer records address Connellia (® ve species) from the same poorly
collected, remote upland habitats. Corollas are showy, rose-pink in C.
smithiana, and location among the leaf-like bracts suggests pollination by
Hymenoptera. Most of the remaining larger genera (Cottendor® a, Dyckia,
Hechtia, Fosterella), and several lesser ones (e.g., Brewcaria,
Steyerbromelia), exhibit principally entomophilous, relatively small, open
¯ owers in a variety of mostly pale pastels. Fosterella spectabilis alone in its
otherwise white to cream-¯ owered genus probably attracts birds with a
coral red, predictably more elongated corolla (Luther 1997; Fig. 3.4D).
Members of Puya, the second largest of the nearly 20 pitcairnioid
genera, also utilize diverse pollinators through mostly Andean ranges.
Ortiz-Crespo (1973) observed specimens in the botanical gardens at the
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Pollination
261
University of California at Berkeley and in situ in Ecuador. Plants at both
locations produced concentrated nectar from relatively large, often bluish
to green, showy ¯ owers rendered additionally conspicuous by bright
orange anthers. Tubular corollas, unaccompanied by scent, the production
of sticky pollen and a simple stigma further implicated birds as the primary
vectors. Colibri coruscans, and a few, much larger Patagona gigas, maintained near continuous presence, while a colony of Puya aequatorialis ¯ owered for about six weeks at a site approximately 20 km north of Quito,
Ecuador. Small, agile Colibri coruscans, the most aggressive of the lot,
often denied two or three additional hummingbirds access to nectar.
In¯ orescences had been under its surveillance for several days before the
® rst ¯ owers opened.
Other Puya species reportedly serviced by hummingbirds include P. chilensis (yellow ¯ owers), P. berteroniana and P. venusta (most consistently by
Patagona gigas). Flocks of hungry Austral blackbirds (Curaeus curaeus)
also visited P. chilensis. In¯ orescence and ¯ ower structure either encouraged or denied use by additional ® nches and ¯ ycatchers according to ¯ ight
and feeding behaviors (Johow 1910). Species that lack sterile extensions on
the lateral axes of what are usually dense panicles also possess ¯ owers with
deep corolla tubes (subgenus Puyopsis; e.g., P. venusta) to discourage all but
the hover ¯ iers. Those taxa (subgenus Puya; e.g., P. chilensis) able to accommodate perching birds also offer shorter ¯ owers accessible to ¯ ying and stationary feeders alike. The diurnal moth Castnia eudesmia feeds both as a
larva and as an adult on some of the same Chilean Puya species. Its reputed
ability to drive similarly disposed insects and even birds from favored food
sources warrants further study.
Abundant nectar disposes the larger-bodied Puya species for ornithophily; requirements to set fruit, especially the monocarps, and often hyperdispersed populations may permit no alternatives. Few other trap-liners
range into paramo and puna formations where Puya often dominate otherwise sparse ¯ oras (Fig. 14.2C). Certain high-elevation species strengthen
the case for obligate dependence on powerful ¯ iers to the extent that their
self-incompatibility characterizes the other alpine Puya. Puya mirabilis
(self-compatible) and P. ferruginea demonstrate the feasibility of chiropterophily at lower elevations. Insufficient capacity to support ¯ ower visitors
with high caloric demands may help explain the absence of many additional Pitcairnioideae and more than a modest contingent of
Tillandsioideae at these same cold, barren sites. The importance of plant
size to frost-tolerance in tropical alpine habitats may further limit the
success of Bromeliaceae above the tree line (Chapters 4 and 7).
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Reproduction and life history
Varadarajan and Brown (1988) considered stigma morphology diagnostic for the primary pollinators of certain Pitcairnioideae. For example, ornithophilous Pitcairnia usually possess compact, conduplicately folded
stigmas (Figs. 3.1C, 12.1) bearing spathulate lobes covered with densely
packed papillae. Organs characterized by less condensed parts, with or
without papillae, accompany large, white, actinomorphic corollas, strong
fragrances, and nocturnal presentation, perhaps to round out an attractive
combination of traits for bats (e.g., Ayensua uaipanensis, Puya aristeguietae). Those taxa equipped with stigmas bearing lanceolate, still more
loosely folded lobes free of papillae supposedly also produce small, diurnal,
white, yellow to green ¯ owers attractive to bees (e.g., Brocchinia steyermarkii, Lindmania guianensis, Deuterocohnia longipetala, Pitcairnia brevicalycina).
Varadarajan and Brown further proposed that the degree of lobe compaction and the disposition of the papillae reveal ¯ oral syndromes more
reliably than does gross stigma shape. Petal scales and septal nectaries also
help identify targeted fauna by providing information on the quantities of
nectar produced and its mode of presentation (Fig. 3.1A,B). Bernardello et
al. (1991) examined a variety of Argentinian Pitcairnioideae to identify the
plant characteristics responsible for the attentions of certain kinds of
¯ ower visitors. Nectary structure and the composition of secretions were
emphasized. Their conclusions, several con® rmed in nature, sometimes
contradicted those of Varadarajan and Brown, as indicated below.
Bromelioideae
Approximately the same array of fauna pollinate Bromelioideae as pollinate Pitcairnioideae and Tillandsioideae. Likewise, ornithophily probably
predominates, according to reports and ¯ oral syndromes displayed among
the larger genera (e.g., Aechmea, Billbergia, Neoregelia, Quesnelia; Table
6.1). Flexibility, like that documented by visits by hummingbirds and butter¯ ies (Eurema diara and Phoebus spp.) to Costa Rican Bromelia pinguin
and B. karatas (Hallwachs 1983), may be especially common in this subfamily. Unusual morphology complicates some interpretations, for
example the nearly submerged, capitulate in¯ orescence of most Neoregelia
species (Fig. 3.2A). Flowers equipped with lavender to pink or white corollas barely extend above the surface as if to deter predators seeking buds and
developing fruits (Fig. 3.5B). Nevertheless, insects and hummingbirds
readily access nectar located deep within the tubular corollas.
Members of the Neoregelia/Nidularium complex and the other nidulate
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Pollination
263
Bromelioideae usually exhibit one of two ornamentations, which in one
and perhaps both instances attract fauna (Fig. 2.13F; Leme 1997, 1998a,b).
Immature foliage and the lower parts of older leaves often accumulate
bright red through orange to purple pigments (occasionally albinistic as in
certain Navia species, e.g., Navia ocellata (formerly N. lactea)) following
¯ oral induction, and sometimes these displays persist long enough to in¯ uence seed dispersal. Rather than conspicuously pigmented centers, other
Neoregelia and a few Hohenbergia and Nidularium species and Wittrockia
superba feature red to purple leaf tips, although not necessarily for the same
purposes (Fig. 2.13F; Chapter 11). Parallels exist in Tillandsioideae (e.g.,
Vriesea platynema, V. minuta). Guzmania sanguinea much more closely
resembles the ® rst group in the way its ¯ owers extend just above the surface
of the phytotelmata maintained by utriculate foliage.
Sweet fragrances emanating from small ¯ owers on often dull in¯ orescences signal entomophily in exceptional Aechmea (e.g., Aechmea purpureorosea, A. lingulata), the largest (.150 species) and among the most
arti® cial of the bromelioid genera. Corollas of Aechmea fasciata change
color from powder blue early in the day to deep rose-red by late afternoon
whether pollinated or not (Fig. 3.2G). Most Billbergia produce pendant,
rapidly elongating in¯ orescences bearing large, ephemeral pastel primary
bracts and hummingbird-serviced ¯ owers (Fig. 3.2F); exceptional entomophilous types (e.g., fragrant B. horrida) stand upright and present
¯ owers subtended by vestigial, equally pale bracts. Billbergia robert-readii
departs farthest from the norm with its odd-smelling, night-blooming,
upturned grayish chiropterophilous ¯ owers born on a lax spike.
Reproductive organs generally suggest that fewer Bromelioideae than
Pitcairnioideae or Tillandsioideae depend on bats to produce seeds.
Ant-inhabited Aechmea bracteata ripens full crops of purple-black
berries on densely ¯ owered panicles in the greenhouse following displays of
small yellow ¯ owers that probably attract insects in situ (Fig. 3.2C). Its deep
pink in¯ orescence bracts seem to advertise fruits rather than ¯ oral nectar.
Unlike the similarly pigmented appendages born by many Billbergia that
sometimes begin to fade even before the last ¯ ower opens, those of
Aechmea bracteata remain turgid and bright, withering only after the comparatively inconspicuous berries begin to shrivel.
Characteristics of ¯ owers, in¯ orescences and foliage further indicate that
insects pollinate most members of several of the larger, predominantly terrestrial genera and also the large majority of Hohenbergia species.
Cryptanthus, which deviate from other Bromelioideae by chromosome
numbers and gender expression (subgenus Cryptanthus; Chapter 11), all
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Reproduction and life history
qualify. Andromonoecy (staminate and perfect ¯ owers on the same plant)
prevails except for members of exclusively perfect-¯ owered subgenus
Hoplocryptanthus. Corollas range from white to pink, and the exceptional
species (e.g., C. exaltatus, C. odoratissimus in Hoplocryptanthus) emit powerful, spicy perfumes. Closely related Orthophytum includes populations
with conspicuous red bracts (e.g., O. saxicola), while more of its membership exhibit entomophily (e.g., O. humile).
Short, globose, axillary in¯ orescences obscured by dense foliage mark
Greigia species as candidates for some of the more unusual pollination and
seed dispersal syndromes among Bromeliaceae (Fig. 3.2E). Flowers range
from drab (e.g., Mexican G. oaxacana) and obscured by subtending, foliaceous bracts and adjacent foliage to quite colorful (e.g., Chilean G. sphacelata) due to red to pink corollas and bracts. Some members of similarly
overlooked Fascicularia, Fernseea and Ochagavia display showy, birdattracting in¯ orescences.
Floral rewards
Most Bromeliaceae reward pollinators with abundant nectar produced by
glandular tissue located in gynoecial septa (Fig. 3.1A). Pollen may augment
these secretions, and perhaps largely replace it for the exceptional, small¯ owered species (e.g., Fosterella penduli¯ ora; Fig. 3.4D). No evidence suggests that visitors collect resins, fragrances or any other nontrophic
rewards, nor is ¯ oral deception a recognized strategy for fruit set by any
Bromeliaceae. Nectar chemistry has become a relatively popular subject in
recent years. Prior to Bernardello et al.' s (1991) study, readings were available for fewer than a dozen species (Percival 1961; Scogin and Freeman
1984; Freeman et al. 1985).
Septal nectaries throughout Bromeliaceae ® t Fahn' s (1979) `structural'
type, because they contain nectariferous parenchyma and a distinct epithelium (Fig. 3.1A). Sucrose, fructose and glucose occurred in every sample,
whereas alkaloids, lipids, phenolics and protein did not, although antioxidant activity of undetermined origin characterized three species
(Bernardello et al. 1991). Secretions collected from 12 of 20 taxa contained
amino acids at concentrations (,7.5 mg ml21) lower than those detected in
the extra¯ oral secretions of several of the same species.
Refractometer readings indicated that dissolved solids ranged from
about 16% in Dyckia ferox to 48% in one of the several samples obtained
from Deuterocohnia longipetala. Disaccharides and monosaccharides
among tested Pitcairnioideae agreed more closely, although the ratios of
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Floral rewards
265
constituent sugars varied substantially among species. Hexose-rich products occurred exclusively in Dyckia ragonesei and D. velascana, while
sucrose predominated in the nectars collected from the other taxa. Both
Bromelioideae assayed, Aechmea distichantha and Bromelia serra, yielded
hexose-dominated nectars, but the ratios of fructose to glucose were high
and low respectively.
Among surveyed Tillandsioideae, all of which belonged to either
Tillandsia or Vriesea, sucrose again dominated, while glucose exceeded
fructose. Con® rmed ornithophils presented sugars at concentrations up to
twice that considered typical for bird-serviced ¯ owers in other families
(Stiles and Freeman 1993). Ratios of the major constituents also deviated
somewhat from expectations. Secretions of hummingbird-pollinated
¯ owers usually contain two to four times as much sucrose as hexose, and
fructose and glucose approached parity, or the former predominated
(Freeman et al. 1985). Puya demonstrates disparities between species pollinated by hummingbirds vs. passerines that Baker et al. (1998) suggest
re¯ ect evolutionary responses to these distinct groups of avians. Sucrose
dominated the sugars in nectar produced by four species (mean 57.0%)
reliant on hummingbirds; hexose predominated in the secretions of three
others regularly visited by passerine birds.
Other values reported for Bromeliaceae generally agree with those
obtained by Bernardello et al. (1991). Percival (1961) also encountered
hexose-rich nectar in Aechmea bracteata, indicating that pollinators probably continue to visit this spontaneously autogamous species, while ornithophilous and self-incompatible Billbergia nutans differed with its
sucrose-rich product. Freeman et al. (1985) noted high sucrose to hexose
ratios for bird-serviced Tillandsia macdougallii. Puya spathacea, the only
species examined by different investigators, yielded higher sucrose to
hexose ratios for Scogin and Freeman (1984). Total solids also varied within
species, perhaps re¯ ecting unequal amounts of evaporation. No relationship seems to exist between the structure of a nectary and the chemistry of
its product.
Martinelli (1994) determined the speci® c gravity of numerous ¯ oral
nectars during his study of the pollination biology of 35 Bromeliaceae
native to Atlantic Forest in Rio de Janeiro State, Brazil (Table 6.3).
Readings ranged from 12.4% for Alcantarea regina to 30.6% for Billbergia
amoena var. amoena. Mean sugar content for 27 taxa was 18.5%. Nectar
volume averaged 11.7 ml for Quesnelia lateralis and 218 ml for Alcantarea
regina, but higher sugar content in the ® rst instance (30.5 vs. 12.4% respectively) reduced the difference in calories per ¯ ower.
Cambridge Books Online © Cambridge University Press, 2009
Table 6.3. Mean volume per ¯ ower and sugar concentration (range in parentheses) in the ¯ oral nectar of some Brazilian
Bromeliaceae. Primary pollinators and breeding system are also provided where available
Species
Aechmea fasciata var. fasciata
Alcantarea regina
Billbergia amoena var. amoena
Neoregelia marmorata
Pitcairnia ¯ ammea var. pallida
Pitcairnia ¯ ammea var. ¯ ammea
Quesnelia lateralis
Vriesea atra var. atra
Vriesea haematina
Vriesea hydrophora
Vriesea neoglutinosa
Volume (ml)
15.6
218
17.6
17.9
60.8
30.7
11.7
209
137
90.8
63.3
Sugar content (%)
28.0
12.4
30.6
26.0
12.7
17.4
30.5
13.3
21.1
13.0
19.8
(22± 32)
(8± 20)
(23± 32)
(24± 30)
(8± 19)
(11± 25)
(24± 36)
(9± 19)
(19± 23)
(7± 15)
(16± 28)
Pollinator
Breeding systema
Hummingbirds
SI
Hummingbirds
Hummingbirds
Hawkmoth?
Hummingbirds
Hummingbirds?
Bats
Hummingbirds
Bat; hawkmoth?
Hummingbirds
SC
?
SC
SC
SI
SC
SC
SC
SC
Source: After Martinelli (1994).
Note: a SI, self-incompatible; SC, self-compatible.
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Floral rewards
267
Less information is available on how Bromeliaceae reward nectarseeking bats than on birds. Sazima et al. (1995) assayed products obtained
from those six Brazilian chiropterophilous vrieseas observed in situ.
Dissolved solids ranged between 17.6 and 19.6%, meaning that concentrations were somewhat higher than the average for the other bat-serviced ¯ ora
tested. Relatively modest nectar volumes per ¯ ower (,0.25 ml), and mostly
distichous spikes that bear one or two open ¯ owers at a time, may oblige
this premium (Fig. 3.5E). Conversely, enough of the dilute secretion
(4.65%) offered by Encholirium glaziovii from the many ¯ owers open on a
given day on its brush-type in¯ orescence accumulates to ¯ ow down the
scape axis (Sazima et al. 1989; Fig. 3.4G). Nectar produced by three of the
four night-¯ owering Vriesea species studied by Martinelli (Table 6.3) contained less sugar than the average for species in what is largely an ornithophilous group.
Field work con® rmed ornithophily for several of the bromeliads surveyed for nectar chemistry. Chlorostilbon aureoventris and Sappho sparganura visited Dyckia ¯ oribunda, D. velascana and Puya spathacea ¯ owers.
Chlorostilbon aureoventris foraged on Deuterocohnia longipetala, Dyckia
ragonesei and Tillandsia lorentziana. Colibri coruscans cropped a population of Vriesea friburgensis. At least some ¯ oral syndromes lacked exclusivity. The butter¯ y Papilio thoas collected nectar offered by a cluster of
Dyckia ¯ oribunda. Apis mellifera harvested pollen from these same
Pitcairnioideae and Dyckia velascana, as presumably could native bees.
Floral characteristics alone persuaded Bernardello et al. (1991) that Dyckia
ferox, Deuterocohnia haumanii and Aechmea distichantha utilize birds.
Tillandsia duratii, one of the most fragrant of all Tillandsioideae, also
appeared to be psychophilous (pollinated by butter¯ ies), while its white¯ owered and comparably fragrant relative T. xiphioides probably attracts
sphingids. Bernardello et al. (1991) disagreed with Varadarajan and
Brown' s (1988) contended entomophily for Dyckia and Deuterocohnia.
Dioecious Hechtia attracts diverse insects, according to Mitchell (1974)
who recorded Bombus sp., Apis mellifera and an unidenti® ed beetle foraging mostly on male, `nutty' -smelling in¯ orescences of H. scariosa.
Coleoptera by the dozen crawled over the ¯ owering shoots of a strongsmelling Hechtia sp. in central Mexico (Benzing, personal observation).
Honey bees replaced a small wasp as the most frequent visitors to the male
¯ owers of H. schottii as the day progressed in a scrub forest in Yucatán
State, Mexico (Fig. 6.2B). John Utley (personal communication) agrees
that some members of this genus at least approach cantharophily (beetle
pollination) according to ¯ oral characteristics (e.g., aminoid odor).
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Reproduction and life history
Fragrances
Anecdotes about the qualities of ¯ oral fragrances among the bromeliads
abound, but few of these publications (e.g., Hegnauer 1963, 1986; Chapter
13) include chemical determinations. Adjectives that range from sweet and
pleasant (triterpenes such as citronellol, geraniol and nerol in some tillansdias; Hegnauer 1963) to musty, garlic-like, greasy, bituminous, as in coal
gas, and reminiscent of spoiled cabbage indicate varied chemistry and
diverse targets. Associations with speci® c ¯ ower form, color and timing
indicate two groups of chemicals, one attractive to the common insect pollinators and the other to bats.
Closely allied lineages tend to produce similar odors (e.g., Tillandsia,
particularly subgenera Anoplophytum, Diaphoranthema and Phytarrhiza,
and Catopsis sweet-smelling and Vriesea section Xiphion unpleasant types).
Lures may be convergent with those produced by other taxa. Knudsen and
Tollsten (1995) reported reliance on the same and related S-containing
compounds by bat-serviced ¯ owers representing six families (no
Bromeliaceae). Odors that attract prey to Brocchinia reducta shoots belong
to the ® rst category (Chapter 5).
Timing also distinguishes the fragrant-¯ owered bromeliads.
Chiropterophilous types smell strongest at dusk or later during the night.
Quite a few sweet-scented species do the same, or their emissions peak after
sundown following more modest activity that day. Pale corollas, sometimes
with ® mbriate margins (T. xiphioides; Fig. 3.3F), probably indicate moth
pollination. Till (1992a) reported that several species of Tillandsia subgenus Diaphoranthema (e.g., T. aizoides, T. virescens) developed strong fragrances at about dawn, became odorless between about 10.00 and 17.00
hours, and then resumed advertisement through the night after which the
corolla withered. Sazima et al. (1989) reported only a faint scent from the
in¯ orescences of Encholirium glaziovii, which otherwise is well equipped for
bat pollination. Knudsen and Tollsten (1995) interpreted this de® ciency as
evidence of derivation from ornithophilous stock. If true, one ¯ oral character changed less than several others as ancestors abandoned one group
of vertebrates for another.
Flowering phenology
Influences of pollinators
Like most other ¯ ora, bromeliads use cues from the environment to coordinate fruit set and seed dispersal with local conditions that affect repro-
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Flowering phenology
269
ductive success. Stimuli responsible for inducing speci® c phenomena parallel those that trigger the same processes in other tropical plants. Likewise,
shoot and in¯ orescence architecture, ¯ ower physiology, and additional
agencies constitute the inherent factors that determine for how long the
individual bromeliad and its population engage in speci® c reproductive
activities. Pollination demonstrates the con¯ uence of environment, plant
and population in setting the schedule for one stage of the reproductive
cycle.
Cause and effect relative to who pollinates which population of
Bromeliaceae and for how long each year seems straightforward enough at
® rst glance. Dependence on speci® c fauna indeed obliges temporal (e.g.,
diurnal vs. nocturnal anthesis) precision as illustrated by the ¯ oral syndromes previously described in Tillandsia. Pollinators further in¯ uence
plant timing according to other aspects of their natural history, for instance
the resident periods of migrant birds and the schedule of emergence and
life spans of ¯ ower-visiting insects. Additional characteristics of the environment, like the seasonality of rainfall, affect the number, quality and
success of seeds. In effect, phenology de® es explanation to the extent that
environmental cues, animal biology and plant characteristics interact to set
tolerances for plant schedules.
Mechanisms that operate at the level of the ¯ ower, the plant, its population and the hosting community all affect the timing and direction of pollen
exchange, and accordingly, in¯ uence the numbers and genotypes of
progeny. Answers to a variety of questions would illuminate important
determinates for speci® c Bromeliaceae. For example, how might ® tness be
affected by the number of ¯ owers produced by a single ramet and the order
in which they open? Do certain displays encourage or discourage visits by
speci® c kinds of pollinators thereby affecting, for example, the proportions
of single vs. biparental seeds or mate selection for allogamous parents? Do
certain arrays of ¯ owers manipulate speci® c kinds of pollinators more
effectively than others to promote fecundity and bene® cial combinations of
genes? How should a population be arrayed in space, and the phenology of
its membership synchronized, to maximize reproductive success? Again,
Tillandsioideae provide some informative examples, and underscore the
challenges of interpreting bromeliad reproduction in the context of adaptation.
Depending on the species, a bromeliad (one genet, variable numbers of
ramets) displays one to many pollen-receptive and/or pollen-donating
¯ owers on a given day, and a few days to many months suffice to complete
anthesis. Impediments to, and tolerances for, adequate fruit set vary
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Reproduction and life history
accordingly. For example, co-occurring individuals with massive, paniculate in¯ orescences (e.g., Tillandsia grandis, Alcantarea regina) need less synchronization to exchange genes than smaller, sparser-¯ owered types. On the
other hand, each Tillandsia macdougallii specimen expends its modest
(,15) complement of ¯ owers within a few days, and smaller-bodied species
(e.g., T. ionantha, T. caerulea) must exchange pollen during even briefer
intervals. Gardner (1984) reported that synchronized ¯ owering by Mexican
T. andrieuxii and T. erubescens (,10 ¯ owers/shoot, 2± 3 open/day) assured
that local populations completed anthesis within 2± 3 weeks.
Some bromeliads follow more episodic schedules characterized by ¯ oriferous days interspersed among barren ones (e.g., T. schiedeana, Vriesea
splendens). Fragrant, night-blooming Tillandsia dodsonii exhibits an especially curious pattern better known in some Neotropical orchids.
Thousands of plants simultaneously, but irregularly, each produce one to
four fragrant, nocturnal ¯ owers with large, white to creamy corollas per distichous, pendant spike (Fig. 3.5F). Cool nights following late afternoon
showers supposedly promote this kind of behavior in Sobralia in some of
the same Ecuadorian habitats. However, stimuli with the same effect
operate elsewhere. Three colonies of T. dodsonii maintained under glass at
the Marie Selby Botanical Gardens in Sarasota displayed 12 ¯ owers on
eight spikes on 18 December 1996 (Benzing, personal observation).
Nothing followed until ® ve nights later when 12 more buds opened on the
same in¯ orescences.
Several factors promote reproductive success among the more diminutive species that outcross; Tillandsia albertiana advertises its single, unusually heavy-textured, bright scarlet ¯ ower, one per shoot, longer than the
usual 1± 2 days (Fig. 3.3L). It, like most of the other neotenic species, also
grows gregariously. Well-established populations comprised of millions of
less than fully synchronized shoots potentially exchange genes over
extended intervals, about two months for T. usneoides in parts of the southeastern United States.
Jaramillo and Cavelier (1998) recorded Tillandsia complanata in ¯ ower
through nine consecutive months and anthesis among T. turneri specimens
at the same Colombian site limited to two 3-month intervals. Kubisch
(1965) reported that 27 Tillandsia species distributed across Mexico each
¯ owered over 3± 4-month intervals. Summer schedules predominated, but
no month lacked reproducing populations. Two polymorphic taxa engaged
pollinators twice at different times of the year at the same locations with
different results. Tillandsia carlsoniae remained in anthesis from October to
November and March to April (Wül® nghoff 1967), but no fruit developed
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Flowering phenology
271
following the fall event. Tillandsia plumosa behaved similarly, except that
phenology divided the population more evenly, and fruits developed on
both occasions. However, Kubisch' s data say little about synchronization
among co-occurring bromeliads, or the timing of ¯ owering of the same
species at different locations.
Martinelli (1994) examined the phenology of 35, mostly ornithophilous,
bromeliads native to Atlantic Forest in Rio de Janeiro State and identi® ed
two patterns described by Gentry (1974). Most common was the `steady
state' arrangement (22 species). Plants in this category open 2± 4 ¯ owers
each day or night over periods of three or more weeks. Another 13 subjects
showed `cornucopia' -type phenology because they displayed 3± 8 receptive
¯ owers each day over just 3± 10 days. Billbergia pyramidalis var. pyramidalis
and B. amoena var. amoena exhibited the second pattern, but populations
showed less synchrony and ¯ owers were available for 8± 12 days. Martinelli
also recorded a strong seasonal bias for these bromeliads, with 73% of the
species ¯ owering between November and February, which happen to be
the wettest and warmest months. Only seven species (23%) ¯ owered during
the much drier, coolest months of April to September, perhaps in part
because many of the local hummingbirds migrate to lower elevations to
avoid the frequent misty days that also characterize midwinter.
Coordinated reproduction can bene® t mixed ¯ oras and the pollinators
they share for different reasons. Sometimes co-occurring populations
reduce competition by ¯ owering asynchronously, while convergent schedules may bene® t any participant unable to attract enough attention without
the assistance of one or more populations that share its pollinators. The
® rst arrangement may also set the stage for speciation leading to arrays of
sympatric lineages like those interfertile Mexican Tillandsia species mentioned earlier. However, no pairs of bromeliads unequivocally rely on
reproductive phenology to coexist, although one report describes a suggestive pattern.
Ecological sorting of predisposed populations, or simple chance instead
of concerted evolution, probably accounts for the staggered phenology of
the several bromeliads (Aechmea nudicaulis, Guzmania monostachia, G.
nicaraguensis) that constitute part of a mixed guild of bird-serviced species
in a humid Costa Rican forest. Whether it was fortuitous, sorted or evolved
in situ, Stiles (1978) demonstrated sequential ¯ owering that may bene® t
participating ¯ ora through maintenance of a group of shared pollinators
(Fig. 6.3). By offering nectar continuously rather than ¯ owering on more
overlapped schedules, and then only for part of the year, these plants favor
a well-fed avifauna and reduce competition for their services as pollen
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272
Reproduction and life history
Figure 6.3. Flowering phenologies over four years of three bromeliads and two nonbromeliads comprising part of a guild of ornithophilous herbs in a wet Costa Rican
forest (after Stiles 1978).
vectors. Incidentally, none of the participating bromeliads are sufficiently
related to conclude that disruptive gene ¯ ow has in¯ uenced the guild' s ¯ owering schedule.
Martinelli (1994) failed to identify mutually complementary phenology
during his analysis of ¯ oral biology among 35 primarily ornithophilous
Atlantic Forest Bromeliaceae (Fig. 6.4). Moreover, high rates of fruit set
despite protandry that often obliges outcrossing demonstrated little or no
competition for pollinators. Another report bears on the question of
whether Bromeliaceae may in fact possess exceptional capacity to adjust
anthesis to track changing environments. Wright and Calderon (1995)
noted that ¯ owering among a 17-member bromeliad ¯ ora on Barro
Colorado island, Panama (® ve during the dry season and the other 12
during wetter months) indicated no major phylogenetic or weather-related
constraints on scheduling compared with some other local epiphytes (e.g.,
the more numerous orchid species). Several communities in southeastern
Brazil suggest that co-occurring Bromelioideae partition the services of the
local seed dispersers (Fischer and Araujo 1995).
Photoperiodism
An unknown number of Bromeliaceae cue on photoperiod to coordinate
important plant activities, like ¯ owering and branching. Cultivated materials underscore the pervasiveness of day length as a ¯ owering stimulus.
Cambridge Books Online © Cambridge University Press, 2009
Flowering phenology
273
Figure 6.4. Flowering phenology of 15 bromeliads native to wet Atlantic Forest at
Macae de Cima (900± 1400 m), Rio de Janeiro State, Brazil distinguished by pollination syndrome. Stippled blocks represent intervals of maximum ¯ owering of
night-¯ owering species. Black blocks indicate bird-serviced, day-¯ owering species
(after Martinelli 1994).
Raack (1985) recorded the dates of ® rst ¯ owering for more than 100 species
and hybrids representing 12 genera growing under glass in southern Ohio.
Just three subjects initiated anthesis during February while 15, the record
number, did so during November. Timing and precision varied with the
subject. Aechmea warasii began to ¯ ower between the ® rst and tenth day of
January over four consecutive years. Guzmania zahnii routinely did so
between the ® rst and middle of June. Exceptional species behaved less consistently, for example Guzmania sanguinea var. brevipedicellata, which
entered the reproductive phase during March, July, December and
November in as many years. Conspeci® c varieties (e.g., Aechmea fulgens)
sometimes followed distinct schedules, and Vriesea simplex 3`Mariae'
¯ owered on dates falling roughly between those of its parents. Table 6.4
illustrates the mostly consistent ¯ owering exhibited by seven Billbergia taxa
in central Florida.
Mastalerz (1957) conducted greenhouse experiments to demonstrate
Cambridge Books Online © Cambridge University Press, 2009
Table 6.4. Dates of maximum ¯ owering for plants representing clones of eight species of Billbergia under cultivation in
central Florida. Note that winter ¯ owering is characteristic and phenology tends to be consistent for speci® c clones
Species
B. amoena var. amoena
B. distachia var. distachia
B. euphemiae var. euphemiae
B. horrida var. tigrina
B. nutans
B. pyramidalis var. concolor
B. saundersii var. debilis
B. vittata clone A
B. vittata clone B
B. vittata clone C
1988
1989
1990
1991
1992
Ð 11
19 Feb
Ð 11
30 Mar
3 Mar
4 Jan
8 Nov
Ð 11
17 Jan
18 Jan
2 Feb
2 Feb
10 Oct
28 Apr
6 Mar
Ð 11
18 Nov
6 Jan
22 Jan
3 Jan
10 Feb
10 Feb
30 Mar
17 Mar
17 Mar
21 Feb
10 Nov
21 Jan
21 Feb
Ð 11
21 Jan
16 Mar
30 Mar
10 Apr
2 Apr
25 Dec
16 Oct
18 Dec
16 Mar
Ð 11
Ð 11
1 Jan
Ð 11
Ð 11
Ð 11
Ð 11
27 Jan
Ð 11
Ð 11
Ð 11
Source: Data provided by D. Beadle of Venice, Florida.
Cambridge Books Online © Cambridge University Press, 2009
1993
Ð
11
Ð 11
Ð 11
26 May
Ð 11
Ð 11
Ð 11
Ð 11
Ð 11
Ð 11
1994
1995
14 Jan
Ð 11
11 Mar
Ð 11
1 Mar
Ð 11
Ð 11
14 Jan
Ð 11
14 Jan
12 Mar
Ð 11
22 Mar
Ð 11
Ð 11
12 Mar
Ð 11
Ð 11
Ð 11
Ð 11
Flowering phenology
275
photoperiodic ¯ owering in Billbergia nutans. Day lengths extended with
arti® cial light delayed the onset of ¯ owering from mid to late January to
about 1 April in one run. Another group of plants covered with black cloth
to effect short days ¯ owered four days before the fully exposed controls.
Subjects maintained in a vegetative state with a simulated summer regimen,
nevertheless, produced ramets, thus engaging in what is usually a post-¯ owering event. Photoperiodism may be especially important for B. nutans
because it ranges farther poleward in Brazil than the other members of its
genus.
Downs (1974) investigated photoperiodism among a selection of
Bromeliaceae with `not very conclusive' results except for deciduous
Pitcairnia heterophylla (Fig. 2.12A). After each treated shoot had generated
about 16 of the unarmed green leaves under 12-h or shorter days, the scalelike, spiny, nongreen foliage and bulbous base that usually presage ¯ owering began to appear. Fourteen-hour days prevented this transition, but not
the formation of additional green leaves. Shoots induced to swell under
short days reverted to the production of green leaves as if some additional
requirement for ¯ owering remained unsatis® ed. Neither simulated drought
followed by heavy irrigation nor defoliation induced in¯ orescences to
appear. However, after producing additional linear leaves, and without
altering the photoperiod, plants bulbed and ¯ owered. Apparently, ¯ oral
induction requires short days, and, judging by the failure of short-day subjects with less foliage to reproduce, also the presence of more than 16 green
leaves.
Inadvertent smoke-induced ¯ owering by pineapple plants in Hawaii ® rst
alerted investigators to a pervasive chemical sensitivity (Downs 1974).
Subsequent inquiry demonstrated that a variety of synthetic auxins (e.g.,
2,4-dichlorophenoxyacetic acid, 1-naphthalene acetic acid, indole acetic
acid), ethylene and related compounds stimulate diverse Bromeliaceae
including Ananas. Beta-hydroxyethylhydrazine (BOH), an ethylene-generating compound, continues in widespread commercial use, but the underlying mechanisms remain poorly understood. Ethylene and acetylene
promote auxin synthesis during several other growth responses (e.g., hypocotyl unbending), and probably act similarly in responsive bromeliads, or
these agents somehow sensitize shoot meristems to endogenous auxins and
possibly other native growth factors.
Hydroperiod, broadly de® ned as changes in the height of the water table
and the arrival of dry or wet weather, coordinates the activities of many
tropical plants. Phenology related to the second stimulus remains undocumented in Bromeliaceae, but certain behaviors are suspicious, for example
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276
Reproduction and life history
the weather-related altered ¯ owering schedules exhibited by some of those
phytotelm species comprising the described Costa Rican guild of ornithophils (Stiles 1978). A closer look at ¯ owering, bud break and, for the deciduous types, leaf turnover relative to moisture supply rather than some
accompanying seasonal cue like photoperiod could prove rewarding.
Breeding systems
Plants observed in situ and in cultivation, ¯ oral morphology and several
experiments con® rm the existence of diverse breeding systems among the
bromeliads. Speci® c mating systems demonstrate expected correlations
with certain aspects of natural history and ecology; occurrences often
follow taxonomic boundaries (Table 6.3). For example, many watch-spring
Billbergia species (subgenus Helicodia) regularly set self-seeds, whereas
members of putatively more primitive subgenus Billbergia generally do not.
The known exceptions among subgenus Billbergia occupy ranges that
usually extend beyond the geographic center for the subgenus in southeastern Brazil, suggesting derivation from what may have been autogamous
founders in a largely self-incompatible clade (e.g., B. amoena var. amoena,
B. pyramidalis var. pyramidalis).
Additional features that in¯ uence the proportions of uniparental vs. outcrossed progeny characterize many bromeliads. Dichogamy (asynchronous
maturation of sex organs) and herkogamy (juxtapositions of sex organs
that limit sel® ng) promote allogamy for many of the self-compatible types,
and for the self-incompatible plant may help diminish stigma clogging.
Protogyny occurs almost without exception among the .150 members of
Tillandsia subgenus Tillandsia (Gardner 1982). Martinelli (1994) reported
protandry for all 17 of the bat or bird-pollinated Vriesea species (not all
closely related) he studied in Brazil. Dichogamy or weak protandry characterized the four Quesnelia species also included in his survey.
Plant characteristics in addition to those already mentioned and substrates also seem to in¯ uence the breeding mechanisms of Bromeliaceae.
For example, species cultivated by ants (e.g., Aechmea mertensii, A. tillandsioides) regularly set self-seeds (Madison 1979), while Bush and Beach
(1995) suggested that epiphytism generally favors autogamy. All of the
monocarpic Bromeliaceae can probably set self-seed, some routinely, yet
many of the same species invest substantial resources to attract pollinators.
Puya raimondii sets it own fruits with up to 8000± 10000 large, brightly pigmented ¯ owers well provisioned with nectar. Considerably smaller
Brocchinia tatei performs similarly with hundreds of yellow, diurnal
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Breeding systems
277
¯ owers. Tillandsia prodigiosa and T. eizii display large primary bracts
colored bright rose to soft pink and green to light purple from which
tubular corollas protrude. Spectacular Alcantarea regina produces showy
yellow corollas in addition to red bracts.
Allogamy, if basic to Bromeliaceae as McWilliams (1974) suggested, has
repeatedly given way to arrangements that favor or oblige (e.g., via cleistogamy) offspring sired by a single parent. Closely placed, developmentally
synchronized stigmas and anthers probably reinforce self-compatibility to
account for the high rates of fruit set characteristic of monocarpic
Bromeliaceae. Maturing stamens reorient to contact any still receptive
stigmas in some populations of Tillandsia utriculata (Gardner 1982).
Whatever the fundamental condition for the family, biparental reproduction enforced by self-incompatibility (SI) occurs widely in Bromelioideae
and Tillandsioideae and, although mostly uncon® rmed, probably in
Pitcairnioideae as well.
The only genetically con® rmed case of SI in Bromeliaceae involves
Ananas comosus, and the mechanism is homomorphic gametophytic SI;
Ananas ananassoides and A. bracteatus can self (Brewbaker and Gorrez
1987). Distributions across Magnoliophyta suggest that neither homomorphic sporophytic SI nor heteromorphic SI is likely to occur in
Bromeliaceae, while the still poorly understood, late-acting SI systems
cannot be ruled out. Martinelli' s (1994) discovery that tubes produced by
allogamous pollen on the stigmas of certain apparently self-incompatible
Vriesea species native to southeastern Brazil grew faster than those from
self-pollen supports McWilliams' s claim and underscores the subtly mixed
nature of at least some of the sexual systems of hermaphroditic
Bromeliaceae.
Self-sterility is more difficult to demonstrate, especially in situ, where a
variety of environmental factors also reduce fruit set. Consistently barren
in¯ orescences among stock protected from predators and pollinators more
reliably signal SI, although the behaviors of individual plants may not
re¯ ect that of populations and certainly not widespread species. Specimens
collected from a particularly ornamental colony of Tillandsia caputmedusae near San José, Costa Rica routinely fail to set fruit in the Oberlin
College greenhouse, whereas stock originating from another population in
southern Mexico characterized by a much duller, pink in¯ orescence do so
every year in the same enclosure.
Numerous additional Tillandsioideae (e.g., T. bulbosa, T. polystachia, T.
stricta, Guzmania monostachia) exhibit similar color polymorphisms and
sometimes unusual mechanisms to insure some reproduction even if the
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Reproduction and life history
sexual process fails. Wide-ranging Tillandsia paucifolia sets self-fruit in
Florida, while certain apparently self-incompatible relatives in South
America proliferate offshoots on otherwise barren in¯ orescences (Fig.
2.11A). Tillandsia dasyliriifolia operates the same way in the tintales (low
inundated forests) of Yucatán State, Mexico (Fig. 6.5C).
Martinelli (1994) conducted self and cross-pollinations and concluded
that at least 20 (mostly Tillandsioideae) of the 35 Atlantic Forest bromeliads he manipulated can produce self-seeds. Fluorescence microscopy indicated masses of tubes from selfed grains, many extending into the ovules.
Pollen from seven more species, all Bromelioideae, also germinated on the
stigmas of the donors, but their tubes barely penetrated into the style. No
obvious aspects of life history or ecology distinguished these plants in ways
that might explain why they possess different sexual systems.
Mechanisms other than SI oblige outcrossing for many bromeliads (Fig.
3.3H). Dioecy occurs in every subfamily, but not extensively (few species),
and close relatives sometimes breed by different mechanisms. Most of the
large genera exhibit hermaphroditism throughout, Aechmea mariaereginae being the single major exception. Predominantly dioecious clades
concentrate in Central America. Wholly dioecious Hechtia (,50 species)
occupies a primarily Mexican range (center of diversity in Chiapas State),
with no species reported south of Nicaragua. Sexually mixed Catopsis
occur from Mexico to Panama, although occasional perfect-¯ owered populations extend to the east and south (C. berteroniana from Florida to
southeastern Brazil; Table 6.5).
Aechmea mariae-reginae and related monotypic Androlepis range from
Costa Rica into Colombia and Venezuela. Should Cryptanthus, and
perhaps also Dyckia, contain dioecious members, then conditions favoring
this arrangement for Bromeliaceae must also exist south of the Equator.
Smith' s (1986) brief allusion to his discovery of a unisexual ¯ ower ± gender
not provided ± on a herbarium specimen of a Cottendor® a demonstrates
our ignorance about even the most basic aspects of reproduction among
the more horticulturally obscure components of this family.
Flower structure suggests that Catopsis exceeds all the other bromeliad
genera for varied and sometimes labile gender expression. What appear to
be consistently dioecious or hermaphroditic species, about six of each
(Palací 1997; Table 6.5), comprise about two-thirds of the genus. The
remaining members for which we have information appear to be either predominantly dioecious (e.g., C. morreniana) or perfect-¯ owered (e.g., C. berteroniana, C. wangerinii). Catopsis nutans follows a site-speci® c pattern with
perfect-¯ owered populations in Florida and dioecious forms in Mexico, El
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Breeding systems
279
Figure 6.5. Aspects of bromeliad reproduction. (A) Seedlings of an unidenti® ed epiphytic member of Bromelioideae growing on a moss-covered branch in Atlantic
Forest in Rio de Janeiro State, Brazil. (B) Seedling of an unidenti® ed Encholirium
sp. characteristically growing against a rock removed from a campos rupestres
habitat in Minas Gerais State, Brazil. (C) Offshoots propagating off the in¯ orescence of Tillandsia dasyliriifolia in Yucatán State, Mexico. (D) Coma hairs of
Tillandsia balbisiana (3450) showing morphology that may increase adhesiveness
to suitable substrates. (E) Approximately two-year-old seedlings of Tillandsia paucifolia that as seeds had been glued to this Taxodium distichum branch (about actual
size). (F) Seedlings of Wittrockia superba on a moss-covered rock in Atlantic Forest
in Rio de Janeiro State, Brazil. (G) Approximately three-month-old seedling of
Tillandsia balbisiana (3125).
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Reproduction and life history
Table 6.5. Gender expression in Catopsis
C. berteroniana
C. compacta
C. delicatula
C. ¯ oribunda
C. hahnii
C. juncifolia
C. mexicana
C. micrantha
C. minimi¯ ora
C. montana
C. morreniana
C. nitida
C. nutans
C. paniculata
C. pisiformis
C. sessili¯ ora
C. subulata
C. wangerinii
C. wawranea
C. werckleana
Flowers perfect or plants rarely functionally unisexual
(southern Mexico)
Dioecious
Status of taxon unclear
Flowers perfect
Dioecious
Flowers perfect
Status of taxon unclear
Dioecious
Status of taxon unclear
Dioecious
Mostly dioecious ¯ owers, sometimes perfect (Costa Rica)
Flowers perfect
Flowers perfect or plants dioecious
(Mexico and Central America)
Status of taxon unclear
Flowers perfect
Flowers perfect or plants dioecious
(Mexico and Central America)
Dioecious
Flowers perfect, or plants rarely dioecious
Status of taxon unclear
Status of taxon unclear
Source: After Palací (1997).
Salvador and Guatemala. Panamanian Catopsis pisiformis produces one
type of ¯ ower with functional gynoecia, but the anthers contain no
effective pollen (Rauh 1983a). Monomorphic, functionally unisexual
¯ owers also characterize certain populations of C. morreniana.
Insights on questions such as how often and why dioecism evolved in
Catopsis should emerge as knowledge of phylogeny increases. Meanwhile,
sex ratios and other potentially revealing demographic data need to be collected before more of the wild populations disappear. Several colonies of
Hechtia schottii contained from 1.7 to 2.0 pistillate to staminate plants in
Yucatán State, Mexico, indicating that ratios among dioecious
Bromeliaceae can deviate from 1:1 (I. Ramírez, personal communication).
Synchronization within populations
Data for Bromeliaceae permit some remarks about reproductive coordination within populations. Hechtia schottii devotes enough axillary meristems
to in¯ orescence to support ¯ owering through much of the year in Yucatán
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Genetic structure of populations
281
State, Mexico (I. Ramírez, personal communication; Fig. 6.2B). Large
plants often bear two in¯ orescences at different stages of maturity, unlike
many of the other members of the same genus. Likewise, except for the
occasional errant ramet, populations of the sympodial bromeliads usually
¯ ower during the same short intervals each year. Plant longevity, minimum
size at ¯ ower induction and year-to-year differences in seedling recruitment
in¯ uence what fraction of a population of a monocarpic bromeliad ¯ owers
during a given season, as documented for Puya dasylirioides below.
Candidates for mass ¯ owering include Tillandsia imperialis, Alcantarea
imperialis and at least one Brocchinia. Not one specimen of giant
Brocchinia micrantha growing along the highway ascending the escalara to
the Gran Sabana in eastern Venezuela bore fruits or ¯ owers among the
dozens of individuals large enough to do so (Benzing, personal observation). Perhaps too few of these exceptionally long-lived bromeliads typically co-occur to more than rarely encounter simultaneous ¯ owering at a
single location. Moreover, just one individual of smaller-bodied and presumably shorter-cycled Brocchinia tatei in the same locality was reproducing that year. Longer-term studies indicate that some years can be more
fruitful than others for slow-growing monocarps. Numbers of ¯ owering
specimens of effectively semilaparous Puya dasylirioides varied almost 10fold during the four-year study conducted by Augspurger (1985) and
discussed below. Specimens of shorter-cycled Tillandsia utriculata fruit
every year in Florida, but no counts are available (Benzing, personal
observation).
Genetic structure of populations
Soluble proteins (allozymes) provide markers to determine the genetic
structures of populations and patterns of gene ¯ ow. Findings for
Bromeliaceae accord with those described for other ¯ ora relative to ¯ oral
biology and certain additional aspects of life history. For example, Soltis et
al. (1987) chose two bromeliads to characterize the effects of different
breeding systems on the genetics of arboreal vs. terrestrial types. Specimens
representing Central American Tillandsia ionantha (subgenus Tillandsia,
Group One) came from Mexico where brightly colored foliage during
anthesis, a stiff, tubular corolla, and uneven seed crops indicate ornithophily (Fig. 2.10M,N). Plants often failed to set fruit in closed greenhouses.
Tillandsia recurvata (subgenus Diaphoranthema), the bromeliad exceeded
only by T. usneoides for greatest distribution, grew in the same general area.
Consistent with experience across its geographic range, fruits routinely
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Reproduction and life history
developed following displays of small, poorly advertised ¯ owers. Comose,
wind-carried seeds (Fig. 3.6J) characterize both populations, although
mobilities may differ, as described below.
Allozymes coded by 19 loci revealed pronounced inbreeding for
Tillandsia recurvata (ballmoss), while T. ionantha (16 loci examined) more
closely matched the genetic pro® le of an outcrosser. Speci® cally, values for
the proportions of polymorphic vs. homomorphic loci, mean heterozygosity, mean number of alleles per locus, and observed heterozygosity all
exceeded those for T. ionantha. Like other autogamous species, T. recurvata
exhibited less genetic variety locally, but substantially more diversity
overall.
Birds apparently mix the alleles of neighboring Tillandsia ionantha.
Inbreeding coefficients (F values) approached those expected at
Hardy± Weinberg equilibrium, whereas numbers calculated for T. recurvata
indicated almost no heterozygotes. However, even as an outcrosser, T.
ionantha demonstrated less overall genetic similarity than most allogamous
plants, in part because so many of the characterized loci code for more than
one allozyme, i.e., are polymorphic. Findings also indicated diploidy or
diploidized, polyploid genomes with the single exception of the locus
responsible for phosphoglucomutase, which in T. recurvata and closely
related T. usneoides coded three isoforms.
Clearly ballmoss and Tillandsia ionantha organize genetic variety in
different patterns with potentially different consequences. Limited gene
exchange may promote capacity to accommodate diverse, site-speci® c
growing conditions for T. recurvata. Similar behavior allows many a cosmopolitan weed to tolerate diverse soils, climates and land uses far beyond
native habitats. Adventiveness in ballmoss, speci® cally its ability to rapidly
colonize so many kinds of substrates, including telephone wires, may rest
on a similar genetic foundation (Fig. 1.3A). However, T. usneoides, even
more than T. ionantha, amply demonstrates that allogamy, in this case
mediated by insects visiting fragrant nocturnal ¯ owers, need not impede
success across broad, ecologically heterogeneous ranges.
Kress et al. (1990) examined four enzyme systems (isocitrate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucose isomerase and
phosphoglucomutase) to conclude that sampled populations of Tillandsia
recurvata, T. usneoides and T. utriculata in central Florida exhibit distinct
genetic structures related to their disparate breeding systems. Autogamous
Tillandsia utriculata was monomorphic for two of the three readable
enzymes and polymorphic for the third. Tillandsia recurvata was polymorphic only for 6-phosphogluconate dehydrogenase. Every subpopulation of
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Genetic structure of populations
283
Spanish moss possessed more than one allele for all three enzymes except
for a single instance of monomorphy for phosphoglucomutase.
Izquierdo (1995) mapped genetic variety in representative populations,
or in one case the only known population, of four species of Aechmea subgenus Podaechmea in Mexico. Aechmea mexicana and A. lueddemanniana
occur widely compared with A. macavughii and A. tuitensis, which occupy
highly insular ranges in the west central part of that country. Izquierdo' s
results only partially matched predictions from geography.
Aechmea mexicana yielded the lowest values for observed heterozygosity
(0.054) and mean number of alleles (2.4) per polymorphic locus. Almost
half of the loci examined were polymorphic, whereas the two narrow
endemics exhibited 2.5 and 2.6 alleles respectively per polymorphic locus.
Most of the populations sampled for each species included high frequencies of homozygotes and evidence of pronounced genetic drift. Overall,
Izquierdo' s results indicate constrained gene ¯ ow among all four species
probably fostered by extensive inbreeding and low seed mobility. Clonal
growth also strongly in¯ uenced genetic structure. For example, the most
proli® c genet of A. tuitensis at the single site sampled accounted for 32.1%
of all the local ramets.
Murawski and Hamrick (1990) examined nine colonies of terrestrial
Aechmea magdalenae, seven located on Barro Colorado island and two on
the adjacent mainland, to characterize the genetic structure of a plant
chosen primarily to represent tropical understory herbs. Of 18 loci that regulate 10 enzyme systems, six were polymorphic for at least one of those colonies with the effective number of alleles ranging from 1.09 to 1.25
(xÅ 51.21), more than recorded for either Tillandsia ionantha or T. recurvata,
but below values obtained for the Mexican Aechmea species. Mean percent
polymorphic loci within colonies was 24.1%, placing A. magdalenae below
average among sampled herbaceous clone-formers.
Highest genetic diversities characterized those colonies featuring the
largest numbers of ramets, and mean heterozygosities exceeded values
expected at Hardy± Weinberg equilibrium. Murawski and Hamrick concluded that small effective population sizes (number of genets) probably
initiated by at most a few founders, and subsequently augmented by outcrossed progeny in most of the nine cases, accounted for the large amongpopulation components of genetic diversity. Frequent genetic identity
between neighbors (within 10 m) demonstrated reliance on stolons for
colony development.
Population structure paralleled reproductive biology here as in the
Tillandsia species with distinct breeding systems and those four self-fertile,
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Reproduction and life history
architecturally varied members of Mexican Aechmea (e.g., A. mexicana
with short vs. A. tuitensis with long ramets). However, Aechmea magdalenae represents a special case because it rarely fruits, just three events in as
many years of observation. Each successful pollination observed during
the study involved a single shoot, always within one of the smaller colonies.
All of the other ramets branched after achieving some threshold size,
perhaps following spontaneous abortions of the still vegetative meristems.
Trap-lining Phaethoris superciliosis alone visited the few ¯ owers produced to set the multiseeded, large, ¯ eshy berries that probably account for
the multiple genotypes within colonies. Aechmea magdalenae also exhibited
a more structured gene pool than the co-occurring trees, probably owing to
its patchy distribution, large numbers of densely packed ramets, and
shorter-range seeds. In the ® nal analysis, A. magdalenae was a poor choice
for a wild type if its periodic cultivation for ® ber by indigenous people has
altered the reproductive performances and related genetic structures of the
populations Murawski and Hamrick assayed in Panama.
Seed dispersal
Morphology described in Chapter 3 con® rms the dispersal of bromeliad
seeds by diverse fauna, wind, gravity and, probably for the exceptional
species, ¯ owing water. We need to review this information before dealing
with issues of seed transport and consequences for plant distribution and
evolution. Again, as with pollination and breeding systems, an uneven literature precludes equal treatments of the subfamilies.
Tillandsioideae
Tillandsioideae disperse among arboreal and lithic substrates via small,
wind-transported seeds structured according to a single aerodynamic
design (Fig. 3.6J; Chapters 12 and 13). Most notable is the coma, which
consists of numerous hairs extending from both ends of the integument
(Alcantarea, Catopsis, Glomeropitcairnia), or just its base (all the other
taxa). If hygroscopic movements like those that assist targeting by some
other anemochorous taxa (e.g., Salix) also bene® t Bromeliaceae, they
remain unreported. Subtle embellishments of a different type probably do
increase seed success in another way. Hairs comprising the ¯ ight apparatus
of certain Catopsis species possess barb-like ends and these, like the joints
and projections featured in some other taxa (e.g., Tillandsia balbisiana; Fig.
6.5D), seem likely to promote adhesion to substrates and perhaps especially
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Seed dispersal
Table 6.6. Distance traveled by the seeds of
10 bromeliads native to Florida with coma present
and removed. Note that the coma promotes
airworthiness to different degrees for different
species
Distance traveled (cm)
Species
Catopsis berteroniana
Catopsis ¯ oribunda
Catopsis nutans
Guzmania monostachia
Tillandsia fasciculata
Tillandsia paucifolia
Tillandsia pruinosa
Tillandsia setacea
Tillandsia usneoides
Tillandsia utriculata
With coma Coma removed
115
73
125
80
130
110
62
145
105
132
26
46
53
55
60
55
50
30
50
25
Source: After Bennett (1992c).
hospitable ones. Experiments indicate that buoyancy and mobility correlate
with the apportionment of mass between the coma and the seed proper.
Bennett (1992c) investigated seed dispersal using four Tillandsia species
chosen to represent closely related bromeliads distinguished by polycarpy
vs. monocarpy and occurrences on bark or rock or both media interchangeably. Peruvian T. sphaerocephala grows as a lithophyte in semiarid habitats;
T. ionochroma occurs in the same general area with populations distributed
either on small trees and shrubs or on rock outcrops. Nothing is known
about the genetic structure of this second taxon, hence the possibility of
substrate-speci® c ecotypes. Tillandsia fasciculata and T. utriculata usually
anchor on trees, the latter sometimes on rock, through much of
Mesoamerica and parts of northern South America. Both populations
Bennett tested root exclusively upon, or at least begin life anchored to, trees
in southern Florida.
Of Bennett' s four subjects, only T. utriculata fruits just once and perhaps
routinely so only in Florida. He recorded three features of seeds related to
their mobility: terminal velocity, distance traveled in a wind tunnel, and the
morphology responsible for these performances. Sedimentation rates
differed substantially (Table 6.6). Seeds of T. utriculata settled slowest
(0.21 m s21), and those of T. sphaerocephala half again as fast in still air
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(0.33 m s21). Distances traveled ranked the two taxa in opposite order
(110.9 vs. 88.2 cm respectively).
More broadly, the epiphytes achieved relatively low terminal velocities at
least in part because they allocate proportionally more biomass to the coma
vs. the seed proper. Percentages (60.0± 61.7%) of the aggregate seed mass
represented by the ¯ ight apparatus grouped the obligate (T. utriculata and
T. fasciculata) and facultative (T. ionochroma) epiphytes together, with saxicolous T. sphaerocephala (41%) as the outlier. In short, the more consistently bark-dependent the taxon, the greater the relative cost of the coma,
the more buoyant its seeds, and the greater the dispersal range.
In addition to providing buoyancy, the coma must secure the seed after
impact until germination occurs and roots replace hairs for holdfast.
Successful dispersal measured by adhesiveness varied inversely with terminal velocity and plant habit. Finally, comas responded unevenly to different
kinds of targets. Seeds of all four species blown against wood, masonite or
even less bark-like concrete blocks in the wind tunnel more often stuck to
the ® rst two media, and differences continued after that. Impacted propagules of T. ionochroma remained most securely attached to all three substrates despite its identity as a lithophyte, whereas those of T. utriculata
proved to have the weakest grip.
An expanded set of subjects might have performed less consistently had
it contained certain additional taxa. For example, Alcantarea (15 species)
occupy granitic outcrops in southeastern Brazil, sometimes as narrow
endemics (Fig. 1.2C). Quite likely seeds equipped with the exceptionally
short appendages illustrated by these bromeliads (e.g., apical and basal
comas approximately one-third and one-half relative to the length of the
whole propagule respectively for A. nevaresii; Leme and Marigo 1993)
re¯ ect the island-like distributions of their habitats, and perhaps also the
surface textures of the local rock outcrops (Fig. 7.1G).
Garcia-Franco and Rico-Gray (1988) conducted the ® rst in situ study of
bromeliad dispersal using a small patch of cloud forest in the Parque
Ecologico, near Xalapa, Mexico. Tillandsia deppeana, a wide-ranging,
montane, phytotelm epiphyte that grows predominantly (58% of adults) on
local Liquidambar styraci¯ ua, inspired the experimental design and provided the test material. Preliminary observations indicated that the surveyed phorophytes supported on average 4.2 adult T. deppeana specimens,
36% of which occurred between 3 and 11 m above the ground. Mean distance between occupied trees was 14.8 m and the two-dimensional crosssection of an occupied crown averaged about 88 m2. Fecundity equaled
3839 seeds per ramet.
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287
A single tray containing 8500 freshly collected seeds dusted with a UV¯ uorescent powder and placed on a branch 6.8 m off the ground in the
`origin tree' served as the parent bromeliad. Five days later, the authors
scanned the six down-wind traps, each of which consisted of a suspended
series of ® ve rectangular strips of sticky tape exposing a total of 3.4 m2 of
adhesive surface. More than half (4449) of the initial stock remained on the
tray, and of those missing just 171 had impacted the tapes and then always
between 3.3 and 10.6 m above ground. Sixty-two percent traveled between
8.8 and 15.0 m and 28% between 24.5 and 28.8 m from the source. The most
mobile seed ¯ oated 38.0 m with just a 0.037% likelihood of reaching any of
the six targets.
Garcia-Franco and Rico-Gray used the observed outputs of the local
bromeliads, population density (4.2 fruiting plants per tree) and the mean
area (cross-section) of the local Liquidambar styraci¯ ua crowns to calculate
that 4415 seeds encounter, but not necessarily adhere to, each phorophyte
each year. If true, pre- and post-germination mortality reduces this number
of offspring dramatically and obliges the uncommon T. deppeana in the
Parque Ecologico that does achieve maturity to potentially disperse multiple crops of seeds to sustain the population, i.e., to be polycarpic. We return
to the circumstances that favor iteroparity vs. monocarpy at the end of this
chapter.
Although impressive given the challenge, Garcia-Franco and RicoGray' s experiment failed to faithfully simulate natural conditions. First,
they made no effort to assess recruitment where success probably occurs
most frequently ± on the origin tree. Most of the one and two-year-old T.
paucifolia seedlings surveyed in Florida shared cypress tree crowns with
probable maternal parents (Benzing 1981a). Second, sticky tape may intercept airborne seeds more or less effectively than twigs and branches that
exhibit more varied surface textures and effects on passing air streams.
Finally, Liquidambar crowns represent three- rather than two-dimensional
targets. Additional problems also probably compromised their results, but
the willingness of these investigators to seek explanations for complex phenomena in situ deserves high praise.
Pitcairnioideae
Septicidal capsules derived from fully superior to inferior ovaries and
medium-sized to small seeds suggest relatively uncomplicated, mechanical
dispersal for most Pitcairnioideae. Membranous or hair-like extensions of
the outer integument of the seed often promote buoyancy, except for Navia
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Reproduction and life history
that alone lacks a two-layered testa (Fig. 3.9). Occasional arrangements
suggest extraordinary functions. Gross (1993) assigned the spongy, textured wing of Pitcairnia aphelandri¯ ora, a bushy species described from
along the Napo River in Ecuador, and Pepinia punicea importance for
water transport ± a reasonable supposition that warrants testing.
Zoochory seems less likely among Pitcairnioideae, although cryptic
elaiosomes like those attached to the dry seeds of other myrmecochorous
¯ ora may turn up yet. Rodents present another possibility if wild relatives
share the partiality domesticated guinea pigs exhibit for certain Pitcairnia
and Puya seeds. Diverse shapes and sizes, which exceed those of
Tillandsioideae and most Bromelioideae (although delivery in a berry complicates comparisons on this second count), suggest multiple dispersal
mechanisms and diverse rooting media. Whatever its biological basis, seed
form circumscribes several genera enough to serve as a taxonomic marker.
Pitcairnia seeds, for example, possess hair-like projections from both ends
of the testa, while those of closely related Pepinia bear a wing more reminiscent of Puya (Fig. 3.9).
The occasional epiphyte (all facultative; e.g., Pitcairnia heterophylla,
Brocchinia tatei) possesses arguably the most airworthy seeds in the subfamily. Conversely, low seed mobility elsewhere helps explain the often
clumped dispersions and fragmented populations of certain terrestrials
(e.g., Andean Puya species; Fig. 9.2). However, rather ordinary morphology need not preclude long-range dispersal. Pitcairnia, for example, ranks
among the most widely distributed of the bromeliad genera, and P. feliciana
alone illustrates the successful outcome of a transoceanic dispersal (Fig.
1.1). Insularity, mostly on tepuis, like isolation on oceanic islands, possibly
favored the unappendaged and probably short-ranged seeds of Navia.
Although basically terrestrial, Pitcairnioideae exploit a variety of kinds
of soils and, quite often, less accommodating substrates like precipitous
rocky cliffs (e.g., various Hechtia, Navia, Pitcairnia; Fig. 7.1B). Perhaps the
myriad shapes and sizes (six major classes; Fig. 3.9) of the seeds that characterize this subfamily partly re¯ ect the microtopography of rooting
media, which for the saxicoles may parallel the lithology of colonized outcrops. Brocchinia (Fig. 6.1D) offers extraordinary opportunity to match
bromeliad seeds with speci® c kinds of substrates because its fewer than 20
species colonize bark, soil and rocks alone or interchangeably. Data on seed
longevity and requirements for germination (e.g., light) would complement
those ® ndings.
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Seed dispersal
289
Bromelioideae
Mostly baccate fruits assure that seed dispersal among the bromeliads
reaches its greatest complexity in Bromelioideae (Fig. 3.6A± H,L). Several
members of this subfamily employ ballistic mechanisms, and many more
of the zoochorous types produce appendaged seeds perhaps better suited
to adhere to feathers, beaks or fur than pass through a gut (Fig. 3.6L).
Fruits of Ronnbergia explodens burst at ripeness to release numerous sticky
seeds, whereas a light touch induces R. deleonii to eject similar projectiles
several meters. A third set of taxa (e.g., several Aechmea species) encourage
ants to carry seeds laced with pheromone-like chemicals (Davidson and
Epstein 1989; Seidel et al. 1990).
Fruits of additional taxa (e.g., Fascicularia, certain Orthophytum) more
closely approach capsular than ¯ eshy status. However, most Bromelioideae
utilize avians, which means that the extensive literature on ornithochory
based on ® ndings for other, better-known plants may also provide insights
on how many hundreds of bromeliads manipulate similar fauna to disperse
their seeds. Almost certainly Bromelioideae employ some of the same
mechanisms described in other families. Unquestionably, reproductive
variety within Bromelioideae exceeds that implied by the typically terse
statements offered by taxonomists to the effect that many-seeded, inferiorovaried, ¯ eshy fruits characterize the entire taxon.
Devices and mechanisms that mediate zoophilous pollination are more
amenable to selection by ¯ ower visitors than aspects of fruits and seeds by
frugivores because plant bene® t increases as pollen moves among rather
than away from members of the same species. The probability that a seed
will succeed rises as distance from conspeci® cs, whether the parent or some
less closely related individual, increases. Not surprisingly, bromeliad
¯ owers and in¯ orescences, more than berries and infructescences, display
familiar dispersal syndromes. Then again, a closer look at Bromelioideae
may reduce this disparity.
Frugivorous birds favor certain colors and food item sizes, and select
among available fruits to meet species-speci® c dietary requirements (e.g.,
Levey 1987; Martinez del Rio et al. 1988; Stiles 1993). Some species seek
primarily lipid-rich meals, while others prefer items much richer in carbohydrates (e.g., thrushes vs. tanagers). Some avifauna possess remarkable
capacities to detect differences in the concentrations of both nutrients
(Martinez del Rio et al. 1988; Stiles 1993). Many of the mammals that disperse seeds locate food by smell, but they often lack the visual acuity of
birds and so on. Furthermore, like pollinators, seed dispersers vary in kind
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Reproduction and life history
and local abundance through tropical America, increasing the advantage
of plant specialization to use speci® c fauna. Quite likely much of the
variety exhibited by the bromelioid fruit and infructescence parallels the
needs and sensory capacities of these diverse frugivores.
Quests for unifying principles in the 1960s and 1970s prompted the
hypothesis that ornithochorous ¯ ora belong to two categories distinguished by fruit size and chemical composition and the characteristics of
the birds that disperse their seeds. According to McKey (1975), a modestsized, but inordinately important, collection of tropical trees exempli® ed
by many Lauraceae, Arecaceae and Burseraceae depends on large-bodied,
obligate frugivores, while the balance of the bird-users rely on avifauna
with broader diets. Bellbirds, hornbills and quetzals, among the other specialists serving the ® rst group of plants, exhibit narrow, plant-based diets
that oblige meals of protein and oil-rich pulp. Bills are specialized to
manipulate and discard rather than help swallow large seeds that consequently need no hard testa. Because dispersal is exceptionally reliable, these
animals permit their food plants to produce relatively few, unusually wellprovisioned embryos (massive seeds).
Plants comprising the much larger second group of tropical ornithochores produce smaller-seeded fruits that provide their dispersers with less
expensive, leaner meals, mostly just carbohydrates, inorganic compounds
and water. Protein and lipids come from other kinds of food. Hard envelopes, either a scleri® ed integument or an endocarp, protect the seeds of the
generalist against often muscular guts and grinding crops. Differences in
the numbers of seeds produced per plant, the cost of the individual fruit,
and rate of seed success prompted McKey to consider members of the ® rst
category more K-selected than the species constituting the less specialized
second type.
Small plant size, patchiness and frequent disturbance (substrates) in tree
crowns (Benzing 1981b) favor adoption of the typically many-seeded,
cheap fruits and generalist-type dispersers that serve epiphytic
Bromelioideae. Super® cially these plants fall into McKey' s poorly resolved
second category, which in reality probably includes multiple syndromes
shared with other ¯ ora. For example, Snow and Snow (1971) identi® ed a
mixed assemblage of epiphytes, including several bromeliads, utilizing the
same avifauna in tropical America. Arboreal Anthurium species and one
Ripsalis, all characterized by small berries, in addition to local
Loranthaceae, comprise this guild in Trinidad. Less information exists for
the aroids and cacti, but the mistletoes produce moderately large, naked
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Seed dispersal
291
seeds, 1± 2 per fruit, enveloped in viscin that hastens passage through guts
and helps secure the voided seed to bark.
Certain Bromelioideae, particularly some Aechmea species and those
Anthurium and cacti mentioned above, may parallel American
Loranthaceae for features that favor safe passage through the honey creepers and tanagers most often responsible for their dissemination in tropical
America. However, a second feature in addition to the presence of a hard
seed coat fails to satisfy the mistletoe model; no bromelioid reportedly also
produces the seed toxins that the branch parasites employ to distinguish
predator from potential disperser. Rather than being endozoochoric like
the mistletoes, some arboreal Bromelioideae may use birds and possibly
other large fauna to disperse seeds without ® rst swallowing them as discussed below. Fruits and seeds of terrestrial Bromelioideae vary even more
than those of the epiphytes, perhaps in some cases to attract fauna absent
in the forest canopy.
McKey' s bipartite scheme essentially consolidates Bromelioideae by dispersal syndrome, whereas the more recent dichotomy formulated by Levey
(1987) imputes importance to another aspect of the fruits these plants
produce. According to Levey, the ease with which seeds separate from the
husk, the morphology of the berry, and aspects of the associated bracts
suggest important facts about dispersers and matches between speci® c frugivores and bromeliads.
Feeding behavior differentiates the avians that consume small-seeded,
soft-walled fruits. The `gulpers' swallow food items intact, while the
`mashers' only ingest the pulp, increasing the likelihood that any delicate
seed appendage or enveloping mucilage present will remain intact to
promote holdfast until anchoring roots develop (Fig. 3.6L). Fruit form suggests involvement of both types of dispersers for the bromeliads, while
chemical composition is less informative.
Fruit chemistry indicated no exceptional nutritional qualities among a
sizable sample of Bromelioideae (Table 6.7). Reducing sugars predominate,
ranging from ,80 to less than 15% on a dry weight basis. Lipids in pulp
never exceeded 3%, nor did protein (not shown). Also important for the frugivore is the size of the potential meal, which, in addition to the mass of the
individual berry, varies on a per plant basis with ripening sequence on the
individual infructescence and in communities according to the density of
fruiting ramets. A single specimen of Bromelia balansae or Aechmea bracteata left unvisited until its entire crop ripens could satiate several sizable
dispersers. Another taxon equipped with exceptionally small fruits (e.g.,
Cambridge Books Online © Cambridge University Press, 2009
Table 6.7. Aspects of fruits and seeds of representative Bromelioideae. Most of the values for fruit chemistry are averages for
two determinations of two samples, each of which was comprised of many ripe berries from one to several plants. Low seed
counts (*) are probably due to poor pollination in the greenhouse
Species
Aechmea
penduli¯ ora
Aechmea
tillandsioides
Bromelia
balansae
Billbergia
brasiliensis
Neoregelia
pascoaliana
Neoregelia
stolonifera
Pseudananas
sagenarius
Quesnelia
testudo
Fruit
color
Fruit
armed
Bract/leaf
color
at fruit
ripeness
Fruit
dry weight
(g)
Likely
seed
disperser
Number of
seeds
per fruit
Seed
dry weight
(mg)
Soluble
Seed
carbohydrate
Lipids
appendaged (% dry weight) (% dry weight)
Blue
Yes
Dull red bracts
0.34
Bird
113.5
0.56
Yes
38.9
3.5
Blue
Yes
Red bracts
0.37
Bird/ants
22.7
5.67
Yes
14.2
5.3
Orange
No
None
9.93
51.8
No
29.3
1.13
No
None
2.95
Nonvolant
mammal?
Bat
2.5
Orange
109.4
11.6
No
62.1
1.36
White
Yes
None
0.22
Bird
238.6
0.81
No
80.4
3.1
White/
blue
Yellow/
brown
Yes
None
0.22
Bird/ants
27
2.27
6.51
None
nonvolant
mammal
Ð *
54.8
2.95
White/
purple
Yes
None
212.2
(multiple
fruit)
0.24
Yes
(both ends)
No
36.7
No
25.5
2.85
Bird
2.0*
Ð
1.25
Source: After K. Stiles et al. (unpublished).
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Ð
Seed dispersal
293
Figure 6.6. Fruit ripening phenology of co-occurring Bromelioideae in coastal habitats in São Paulo State, Brazil, illustrating degrees of overlap among species dependent on the same kinds of dispersers. (A) Bird-dispersed species. (B)
Mammal-dispersed species. Heavy lines indicate periods of greatest fruit production (after Fischer and Araujo 1995).
Araeococcus micranthus) may mitigate that disadvantage by occurring at
high densities or attracting smaller fauna.
Seed size, numbers per fruit, ratio of seed to pulp mass, and ripening
schedule range widely among Bromelioideae (Figs. 3.6A± H, 6.6; Table 6.7).
How these and other qualities favor the use of speci® c kinds of rooting
media, or determine importance as food for particular frugivores, remains
obscure. Among berries generally, those of Bromelioideae range from small
(e.g., Aechmea, Neoregelia, Nidularium) to moderate-sized (e.g., Billbergia,
various Bromelia). Groups of related species often exhibit similar fruits and
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294
Reproduction and life history
seeds. For example, members of Cryptanthus subgenus Cryptanthus (e.g.,
C. beuckeri) produce modest-sized berries even by subfamily standards,
each containing just one to a few large seeds. Berries ripened by members
of subgenus Hoplocryptanthus (e.g., C. pseudoscaposus) package many
more, smaller seeds.
Finer points of reproductive morphology conceivably also match bromeliads, dispersers and substrates, for example aspects of seed shape and
surface texture respectively to certain kinds of rooting media or digestive
systems. A ¯ at side probably helps secure the ovoid seeds of Aechmea bracteata (Fig. 3.6H) against gravity, and the same snug contact may promote
imbibition from moist bark. Dejean and Olmsted (1997) report that seed
shape accounts for the regular occurrence of this epiphyte in the crotches
of rough-barked hosts in the seasonally inundated forests along Mexico' s
northern Yucatán coast (Fig. 8.1B). Additional important detail distinguishes tissues around the seeds (Fig. 3.6I). Berry color ranges from drab
(e.g., some Billbergia species), to orange (e.g., Bromelia), to white, lavender
and blue (e.g., Aechmea, Neoregelia). Those sticky seed appendages (Fig.
3.6L) probably also enhance water balance, and by encouraging bill-wiping
promote transfers of adhering seeds from feeding birds to bark.
Most bromelioid fruits lack fragrances consistent with bird use; some of
the exceptions emit pungent, pleasant odors (e.g., Ananas, Bromelia) or
suggestions of rotting fruit (e.g., Billbergia zebrina). Seeds of Billbergia
elegans germinated following passage through a bat to provide the only
published documentation of endozoochory in Bromeliaceae (Abendroth
1957). Presentation also varies. Those pleasantly aromatic berries of
Bromelia balansae nestle amid congested, armed, foliage well positioned to
defy any large frugivore. Small, nonvolant mammals probably harvest most
of the largely obscured, brownish, globose fruits presented by certain
Greigia species. Foliose bracts mostly hide the dull orange, melon-scented
fruits of an unidenti® ed Wittrockia.
Additional, more subtle aspects of fruit display and release may enhance
dispersal for certain Bromelioideae. Remarkably little pressure, probably
well within capacity for a small frugivore, need be administered to separate
the ripe Aechmea bracteata berry from its pedicle and extrude several of the
sticky seeds (Fig. 3.6H). Spontaneous discharges following detachment
(e.g., certain Billbergia) suggest the condition antecedent to ballistic dispersal. Foraging behaviors may help explain some otherwise puzzling reproductive morphology. For example, Abendroth (1965) noted that
Tachyphonus coronatus checks for ripeness by pulling at the oversized calyx
of the berries born on the capitulate infructescence of Neoregelia concen-
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Seed dispersal
295
trica (Fig. 3.5B). Several seeds routinely remained in the discarded leathery
husks. Pedicles sometimes (e.g., Neoregelia stolonifera) undergo intercalary
growth to elevate the mature berry above the surface of the phytotelmata
(Fig. 3.6F).
A broader survey might reveal suites of plant characters speci® c to
certain dispersers, or the types of animal behaviors needed to successfully
manipulate one or another kind of fruits and seeds. For example, are the
armed berries and ¯ oral bracts that seem so well disposed to discourage
fruit gulping (Figs. 3.2D, 3.5H) associated with seeds that rely on digestible
appendages for anchorage? Indeed, can the delicate attachments that characterize so many bromelioid seeds survive passage through the guts of frugivores? Why do seeds such as those of Billbergia lack equivalent
embellishments (Fig. 3.6G)? Finally, which fauna are targeted by certain
Aechmea subgenus Chevaliera species that produce berries with hard, sharp
apices stubbornly embedded in equally resistant stem tissue?
Myrmecochorus Bromeliaceae comprise part of a guild of convergent,
ant-dependent taxa that includes representatives of about 10 families, but
primarily Araceae, Gesneriaceae, Piperaceae, Moraceae and Orchidaceae
(Davidson 1988; Benzing 1991). Occasional Tillandsioideae participate
(e.g., T. fasciculata; Catling 1995), but too sporadically to warrant inclusion
among the nest-garden ¯ ora. Bromelioideae and some other plants
restricted to ant-provided substrates share methyl-6-methylsalicylate, benzothiazole and additional 6-substituted phenyl derivatives as volatile seed
constituents (Davidson and Epstein 1989; Seidel et al. 1990). Other aromatics that also proved attractive in cafeteria-style tests with nest-gardening
Camponotus femoratus, Crematogaster linata and Azteca spp. in Peru
included ortho-vanillyl alcohol and limonene. Ant food, often an oily seed
appendage, characterizes many of the carton-users, but none of the bromeliads.
Pulp containing more concentrated lipids and proteins than necessary to
attract bats or birds may encourage certain ants to mine seeds from the
berries of the bromeliads they farm. Madison (1979) noted a ¯ eshy funiculus on seeds produced by ant-gardened Aechmea brevicollis, A. mertensii
and A. angustifolia in Brazil. Aechmea tillandsioides, yet another nest specialist, produces the same carbohydrate-laden fruit recorded for
Bromeliaceae without known relationships with ants (Table 6.7). Perhaps
something else, neither food nor fragrance, prompts collection and incorporation into ant carton. Ule (1906) and Madison (1979) suggested pupal
mimicry based on seed shape and size and possibly odor as the mechanism
some bromeliads use to colonize one nest from another. Perhaps birds
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296
Reproduction and life history
remain the primary vectors of these bromeliads, consuming intact berries
after which the ants recover and use the voided seeds much as bats and ants
act in tandem to help disperse certain epiphytic ® gs.
Lower vertebrates, and perhaps even some macroinvertebrates, disperse
the occasional ¯ eshy-fruited bromeliad. Hyla truncata, a frog that sometimes consumes fruit almost exclusively according to gut contents, and terrestrial Neoregelia cruenta (Fig. 7.13E) reportedly mediate the
establishment of a dominant shrub (Erythroxylon ovalifolia) in certain
Brazilian restingas (Fialho 1990). Seeds defecated in moist leaf bases more
often succeed than those deposited elsewhere.
Another documented disperser of certain nonbromeliads (e.g., Pandanus
species), the omnivorous land crab Gecarcinus lateralis, decimated the
abundant fruits of Bromelia pinguin in a coastal dry forest located in central
Vera Cruz, Mexico. These crustaceans were so intent on feeding that they
risked predation by climbing the infructescences, but only fragments of
integuments turned up in dropping. Nevertheless, Garcia-Franco et al.
(1991) suspected that the rare seed that germinates may endure for hundreds of years via less vulnerable ramets.
Table 6.8 summarizes characteristics of infructescences, fruits and seeds
that distinguish ® ve putative seed dispersal syndromes in Bromelioideae.
Note that the persistent, often stiff sharp calyx is assigned importance as a
deterrent to the gulper (Fig. 3.5H). Conversely, its presence may help the
masher detach berries from dense infructescences. Timing represents yet
another variable, which is not shown in Table 6.8. Coordinated ¯ owering is
not the only reproductive activity that simultaneously promotes a continuous supply of food for required fauna and relaxes the need for plants to
compete for dispersal services.
Fischer and Araujo (1995) reported evidence that shared seed dispersers
in¯ uence phenology among Bromelioideae native to four lowland coastal
habitats in southeastern Brazil, three covered by forest and the fourth situated along an open, rocky seashore. Subjects included members of
Aechmea, Quesnelia and Nidularium, some in two, three or all of the surveyed communities (Table 6.9). They also examined local Tillandsioideae,
all of which depend on wind currents to disperse. Unspeci® ed passeriforms
and, according to feeding trials, two mammals ± Proechimys iheringi, a
rodent, and Philander opossum, a marsupial ± carried seeds for the sampled
Bromelioideae.
All three Quesnelia species, the two populations representing Nidularium,
and one of the ® ve local Aechmea species attracted mammals rather than
birds to usually less colorful berries than those presented by the other four
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Table 6.8. Putative seed dispersal syndromes of Bromelioideae
Additional
remarks
Type
Fruit color
Fruit presentation
Fruit size (length)
Fruit fragrance
Birds
Bright colors: red,
blue, white, purple
Presented on elongate,
spreading infructescence
Small (,15 mm)
No odor
Fruits armed or
unarmed perhaps
depending on
reliance on
gulpers or
mashers. Presence
of seed
appendage may
re¯ ect the same
dichotomy
Bats
Dull colors, sometimes
densely covered with
re¯ ective trichomes
Presented on exposed,
elongate infructescence
Medium (15± 20 mm)
Odor of rotten
fruit
Fruits unarmed,
seeds
unappendaged
Dull colors
Sometimes hidden by ¯ oral
bracts on short, compact
infructescence
(e.g., Neoregelia)
Small to large
Odor present
Plants terrestrial
or low- growing
epiphytes
Bright colors as in
bird-dispersed species
Presented exposed (e.g.,
certain Aechmea species)
or relatively hidden
(e.g., Neoregelia)
Small (,15 mm)
Volatile, antattracting
compounds
associated
with seeds
Ants may disperse
seeds from feces
of larger animals
Nonvolant
mammals
Ants
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298
Reproduction and life history
Table 6.9. Dispersal syndrome, shade-tolerance and location of substrates
among 10 animal-dispersed Bromelioideae native to coastal Atlantic Forest
habitats in São Paulo State, Brazil
Species
Habit
Aechmea organensis
Aechmea gamosepala
Aechmea nudicaulis
Aechmea pectinata
Aechmea distichantha
Quesnelia arvensis
Quesnelia humilis
Quesnelia testudo
Nidularium antoineanum
Nidularium innocentii
Facultative
Facultative
Facultative
Facultative
Terrestrial
Terrestrial
Epiphyte
Epiphyte
Epiphyte
Facultative
Location of substrates
Seed
Shade- (average height above
disperser tolerant
ground in m)
Birds
Birds
Birds
?
?
Mammals
Mammals
Mammals
Mammals
Mammals
No
No
No
No
No
No
Yes
Yes
Yes
Yes
1.0
2.6
6.6
3.2
0.0
0.0
3.6
4.6
2.7
0.5
Source: After Fischer and Araujo (1995).
bromeliads (Table 6.9). Characteristic short, foliose infructescences positioned close to the centers of leafy shoots further obscured the fruits of
Nidularium. Fischer and Araujo mentioned no odors, but the marsupial
may feed by olfaction and sight. Ornithochorous Aechmea presented more
exposed and more colorful berries on inclined or horizontal in¯ orescences
readily accessible to small perching birds. Only Aechmea pectinata of the
mammal-dispersed taxa deviated from precedent by also bearing bright red
fruits on a vertical infructescence.
Light requirements and rooting media usually paralleled dispersal mode.
All of the observed Tillandsioideae, eight Vriesea species and Tillandsia
stricta, anchored in the canopy exclusively, six of the nine only in wellexposed microsites. Conversely, the surveyed Bromelioideae rooted in soil
or were facultative epiphytes at proscribed elevations where forests occurred
(Table 6.9). Distributions further indicated that four of the berry-producing
subjects tolerated deeper shade and relied primarily on mammals to disperse progeny. Bird-sown Aechmea occurred most abundantly in the
restinga formation and in the other, even more sparsely vegetated seashore
communities. They also anchored higher in tall vegetation than relatives
dependent on mammals. Just two taxa, Aechmea distichantha and Quesnelia
testudo, combined shade-intolerance and dispersal by mammals.
Phenology consistent with dispersal mode characterized all 19 subjects,
but only the zoochoric bromeliads illustrated patterns reminiscent of the
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Seed viability and germination
299
temporally structured guild Stiles (1978) reported for those bird-pollinated
species in Costa Rica (Fig. 6.3). Each of the three bird-dispersed Aechmea
species (A. gamosepala, A. organensis, A. nudicaulis) fruited over 2.5± 5.0month intervals, yet activity overlapped remarkably little anywhere (Fig.
6.6). Schedules, whether coincidental or modi® ed through selection to
match local circumstances, assured nearly continuous supplies of berries
for the dependent fauna.
The four less consistently co-occurring mammal-disseminated species
(Quesnelia testudo, Q. humilis, Nidularium antoineanum, N. innocentii) in
the two tall forest habitats also provided more or less constant supplies of
fruit with only modest phenologic redundancy (Fig. 6.6). Schedules for terrestrial Quesnelia arvensis and Aechmea distichantha overlapped much
more at the rocky shore and restinga scrub locations. All nine
Tillandsioideae shed seeds during the dry season, and even then rainmatted comas prevented many propagules from leaving the dehisced capsules.
Site-speci® c timing characterized Nidularium innocentii, perhaps to
heighten the attention of the local mammals needed to disperse its seeds
(Fig. 6.6). Individuals that advertised edible fruit from March to May
occurred exclusively in the restinga community, whereas plants in the same
condition from December to early February invariably occupied either the
riparian or dense forest sites. Were ripe fruit also a March to May phenomenon in the second and third communities, N. innocentii might have to
compete with three other bromeliads for the same frugivores. A different
pattern prevailed in restinga, where N. innocentii alone requires mammals
and, apparently for unrelated reasons, fruits later in the year.
Seed viability and germination
Seed viability and germination rank among the least-studied aspects of
bromeliad reproduction. Downs (1963) and colleagues tested diverse conditions and reported a variety of sometimes puzzling responses (Table
6.10). Longevity and temperature optima varied, and most subjects
responded to light (were photoblastic). Seeds of Billbergia elegans
remained viable for at least 72 weeks and about half of those of Neoregelia
concentrica germinated 76 weeks after harvest. An unidenti® ed Puya continued to respond for 30 months (Vasak 1969), con® rming potential for
seed banks, although no other evidence supports this possibility.
One brief exposure to light induced Billbergia elegans to germinate,
whereas a single, much longer pulse or several shorter ones over as many
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Table 6.10. Effect of various frequencies and durations of light exposure on the germination of seeds of bromeliads
Species
Pitcairnia sp.
Pitcairnia ¯ ammea
Vriesea haematina
Vriesea scalaris
Nidularium fulgens
Aechmea coelestis
Puya berteroniana
Percent germination
Duration of
experiment
(days)
Continuously
dark
8 h light:
24 h
1 h light:
24 h
26
26
18
18
10
10
17
0
0
0
6
0
0
0
10
91
96
100
98
83
100
0
0
96
100
98
65
0
Source: After Downs (1963).
Books Online © Cambridge University Press, 2009
1/4 h light:
12 h
Ð
0
Ð
100
Ð
Ð
100
1/12 h light:
2h
92
Ð
96
Ð
98
91
Ð
Resource economics and life history
301
days sufficed for some relatives (e.g., Alcantarea regina, Puya berteroniana).
A linear dose response leading to 70 and 100% success after ® ve days characterized Aechmea nudicaulis and Wittrockia superba. Downs' s (1963) list
of 33 species representing all three subfamilies indicated that only
Tillandsia stricta germinated about as well in light as in darkness. Five
additional Tillandsioideae exhibited some germination in covered containers, but exposure usually increased yields. Experiments identify phytochrome as the pigment responsible for light sensitivity, but behavior varied
with the subject. Exposure to far red light completely reversed the effects
of red light for some species, while the seeds of others responded inconsistently.
Temperatures prevailing in situ predicted behavior in the laboratory. For
example, seeds of natives of lowland, tropical and subtropical regions (e.g.,
Aechmea nudicaulis, A. coelestis, Wittrockia superba, Vriesea scalaris)
failed to germinate at 15 °C and responded best between 20 and 30 °C.
Conversely, yields for Puya berteroniana, a high Andean terrestrial, began
to decline as temperature rose above 15 °C, and only a few percent would
germinate at 25 °C.
Resource economics and life history
Economists employ tools that can also be used to analyze the growth and
body form of organisms in terms of evolution and ecology. According to
this approach, plants resemble factories because they also acquire raw
materials, in this case CO2, water, light and essential ions, to fabricate valueadded `products' , speci® cally progeny. Like any enterprise using the same
materials that other factories require to manufacture the same products, cooccurring plants compete. Just how severely they interfere with one another
depends in large part on the distinctness of the strategies used to obtain
mutually required resources.
Green plants vary in the ways they amass and process the resources necessary for photosynthesis, and then how the resulting photosynthate is allocated among different parts of the body to support growth and
reproduction. More to the point, plants differ in ways that determine ® tness
under speci® c growing conditions, including those attributable to the presence of other plants in the same habitats. Interferences among co-occurring
species diminish as patterns of resource use diverge or become complementary in some way as populations assemble to establish communities during
succession and over longer-term evolutionary time. Ultimately, organization and compatibility emerge that result from and bene® t plants with
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302
Reproduction and life history
distinct strategies growing together (e.g., a small, light-sensitive herb
growing in the shade of a more heliophilic tree to cite a simple example).
According to the economic/evolutionary interpretation of plant growth,
structure and function, the vascular plant apportions photosynthate
among roots, stems and leaves, and then reproduces within constraints
peculiar to its natural history. That natural history or ecological strategy in
turn allows the plant to accommodate speci® c growing conditions (kinds
of habitats). For example, frequent disturbance mandates that the weedy
annual invest an extraordinary proportion of its biomass in many small,
long-lived, photoblastic seeds. On a coarser scale, ruderals also allocate
more dry matter to shoots than roots. Longer-lived plants adapted to more
stable substrates favor vegetative organs to achieve architectures more conducive to competition and resource conservation for extended life and
repeated reproduction (e.g., most Bromeliaceae).
Additional variety distinguishes the architectures of the herbaceous perennials, much of it dictated by the differential availability of resources in
speci® c kinds of habitats. For example, compared with vegetation native to
moist forest, desert plants invest more biomass in roots than in shoots
because survival is challenged more by the acquisition of adequate moisture than by that of light, which is the more abundant of the two resources
relative to plant needs. On a ® ner scale, photon-trapping and processing
molecules receive biosynthetic priority over those responsible for the dark
reactions of photosynthesis in shade compared with sun leaves. The developmental program does recognize that conditions vary in the same environments. While life-history type proscribes fundamental structure and
function, opportunity for modest adjustment (phenoplasticity) remains.
Although environment affects the expression of all developmental programs, plasticity varies with the ecological strategy. Plants with relatively
short life cycles native to habitually heterogeneous habitats, and those types
forced to accommodate often changing conditions, possess the greatest
malleability. Features like root/shoot ratios shift dramatically among weeds
depending on the prevailing supplies of photons, water and key nutrients ±
much more so than for the slow-growing, stress-tolerant perennial. As longlived plants more or less con® ned to limited ecospace (unlike a vine), bromeliads, or at least the individual ramet, exhibit relatively modest plasticity.
In effect, their architectures (dense rosettes of foliage incapable of sun
tracking) represent time-averaged, relatively ® xed responses to past selection and current conditions.
Reproductive allocation (RA), the ratio of phytobiomass or calories
committed to reproductive vs. vegetative tissue by the individual plant,
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Resource economics and life history
303
serves as a crude measure of ecological strategy, but multiple functions
(e.g., green in¯ orescence bracts) and other complexities preclude precise
cost-accounting. Iterative growth (iteroparity) causes additional problems.
Much of the investment in the perennial in¯ orescence of Deuterocohnia
schreiteri (Fig. 3.4J), for example, performs repeated duty by ripening successive crops of seeds over an equal number of years.
Nevertheless, no other metric has been employed as often or can be so
easily obtained to infer ecological strategy and related requirements for
growth. According to the analogy between ¯ ora and industry, RA reveals
how plants deploy photosynthate to maintain ® tness under speci® c
growing conditions. Finer details of form (e.g., leaf anatomy) were
accepted long ago as indicators of plant performances and conditions in
habitats (e.g., water-use efficiency and water supply respectively); architectural analysis simply extends this practice to a higher level of plant organization.
Bennett (1991) applied regression statistics to determine whether RA
increases with epiphytism among the same bromeliads he used to compare
seed mobility. Speci® cally, he determined whether the slope of the allocation regression would sort these species in the following sequence from low
to high: T. sphaerocephala, T. ionochroma (saxicolous then epiphytic), T.
fasciculata, and ® nally T. utriculata. Four of the ® ve populations yielded
signi® cant RA to V (vegetative dry mass) regressions. Vegetative tissues
accounted for 28± 79% of the variability in RA.
Regression slopes for the iteroparous species ranged from 0.145 (T. fasciculata) to 0.213 (T. sphaerocephala), with no statistical differentiation.
Tillandsia utriculata yielded a much higher value at 0.466. Every y-intercept
deviated signi® cantly from zero, except for epiphytic T. ionochroma, which
produced a value of 0.356. If immature ramets of the iteroparous taxa contribute resources to attached ramets as they ¯ ower, then the intercept may
be positive. Because the generally more caulescent saxicoles also branch
more frequently than the epiphytes, their intercepts should be greater, and
those for the monocarpic populations of T. utriculata zero or negative.
Benzing and Davidson (1979) determined how T. paucifolia allocates
mineral nutrient capital for reproduction in Florida habitats distinguished
by the numbers and sizes of this epiphyte present (Figs. 1.3C, 6.7). Previous
examination of the same species (Benzing and Renfrow 1971a; Figs. 7.8,
7.9) had revealed correspondences between N, P and K concentrations in
shoots and whole-plant mass at maturity and number of fruits. They also
found that the most fecund individuals subsequently produced the smallest
ramets, suggesting greater inherent emphasis on seed production than the
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304
Reproduction and life history
Figure 6.7. Ontogeny of Tillandsia paucifolia. A± I correspond to the nine size/age
classes used for the demographic analysis described in the text. A± G represent pre¯ owering stages, H, adults fruiting for the ® rst time, and I, plants with ramets (after
Benzing 1981a).
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The organization of reproductive allocation
305
continuance of, or at least the robustness of, established genets. However,
adults always reserve enough resources to support additional fruiting later,
as Garcia-Franco and Rico-Gray (1988) noted for T. deppeana in central
Mexico.
The organization of reproductive allocation
Inferences about ecological strategy based solely on RA lack the resolution
possible with additional data on seed size, number and packaging.
Variations in the ® rst two, if not all three, of these parameters correlate
with other features of plants indicating adaptive value. But how tightly
coupled are plant and environment at this level of detail? Certain bromeliads produce ovules in numerous gynoecia, while others ripen comparable
crops of seeds in many fewer ovaries. Do these arrangements decisively
in¯ uence reproductive success? Might hyperovulate gynoecia compensate
for infrequent pollination as in many Orchidaceae (Benzing 1987a)?
Conversely, could large numbers of gynoecia, each containing fewer ovules,
spread the risk of predation? More ¯ owers and fruits can extend the time
available to attract pollinators and disperse seeds, but the same higher
numbers and longer displays also increase plant apparency for searching
herbivores. Perhaps some more fundamental aspect of plant architecture,
possibly the basic organization of the in¯ orescence (e.g., the short, dense
head of most Neoregelia species), constrains fruit number.
Members of Tillandsia vary enough to consider how seed packaging
relates to life history among a group of closely related, but ecologically
diverse, bromeliads. Those populations of Tillandsia ionochroma and T.
utriculata observed by Bennett (1991) produced approximately the same
number of seeds per infructescence (about 11 200 vs. 13300), but in 74 compared with 56 capsules. Tillandsia utriculata matured 237 seeds per fruit,
while T. ionochroma averaged just 153. Are these distinct loadings adaptive,
selectively neutral, or mandated by inherent design (phylogenetic) constraints? At least two hypotheses provide plausible explanations for the
same condition. First, perhaps pollen supply historically limited fruit set
for T. ionochroma, whereas shoot size has had the greatest in¯ uence on
fecundity for self-pollinating T. utriculata. Alternatively, the sample year
was an exceptionally good one for T. ionochroma and its seed crop larger
than usual. In fact, relatively few T. utriculata specimens bore fruit, just
5.3% of the surveyed near-adults (close to or just short of ¯ owering size),
and capsules per mature plant varied several fold. Demographics
confuse the comparison even further; Tillandsia ionochroma outreproduced
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306
Reproduction and life history
T. utriculata on a population-wide basis because more of its shoots ¯ owered that year.
Conceivably, breeding systems and associated patterns of resource allocation help explain why these two taxa package seeds differently. Material
economy accrues from producing more ovules in fewer gynoecia, assuming
no density-independent predation. If seed mass also remains constant
(untrue among Tillandsia species), investments in capsule walls and ancillary non-green tissues that also support reproduction decrease on a per
progeny basis as seeds per fruit rises. Savings may be especially signi® cant
for the monocarp with its heavier dependence on seeds to maintain populations.
Case histories
Bennett (1991) cited aspects of branching, seeds and demography to
support his contention that the durability and areal extent of rooting media
have helped differentiate the life histories and architectures of certain
Tillandsia species. Saxicoles compared with the examined epiphytes consistently exhibited lower fecundity and seed mobility. Rock-dwelling T. sphaerocephala and T. bi¯ ora bore more ramets but dispersed fewer seeds than
the epiphytes (e.g., 2362 to 70 681 seeds per infructescence for T. sphaerocephala and T. utriculata respectively), and populations included fewer juveniles per adult. Post-¯ owering shoots of Tillandsia bi¯ ora averaged more
than 20 ramets and T. sphaerocephala seven compared with fewer than two
offshoots for the epiphytes and facultative T. ionochroma. Shoots that
branched before ¯ owering suggested diminished apical dominance among
the saxicoles. In all, six characteristics distinguished Bennett' s bark-users
from his rock-users: higher ratios of seed weight to coma length, longer
comas, more proli® c seed production, a larger in¯ orescence, greater overall
plant mass, and stronger apical dominance (less branching).
One of Bennett' s seven subjects demonstrated the effects of substrates on
evolution more impressively than the other six. Tillandsia utriculata exceeds
most members of its genus by number of intraspeci® c taxa, many of which
appear to represent the products of ® ne-tuning to local growing conditions,
especially the stability of rock vs. bark as a rooting medium. Plant architecture and habit (epiphyte vs. saxicole) shift together across Mesoamerica,
more or less according to climate and available substrates. Recall that
Florida populations examined by Benzing and Davidson (1979) and
Bennett (1991) grow exclusively in tree crowns under relatively humid conditions, while those in Mexico often experience greater drought and fre-
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The organization of reproductive allocation
307
quently anchor on rocks. Capacity to produce ramets and display bright
colors to promote outcrossing also shift with location.
Average fruit set among plants representing a series of Mexican populations observed by Gardner (1982), whether anchored on rocks or on bark,
ranged from 16 to 50%. Florida specimens achieved greater success,
perhaps because stamens contact the style as ¯ owers age, a feature not
reported elsewhere for this species. North American subjects also lack the
same bright pigmentation and routinely die without activating a single axillary bud, sometimes even after injury destroys an immature in¯ orescence.
Relatives in Mexico vary on both counts by routine production of deeper
pink ¯ oral bracts and frequent branching. Some other features of reproduction, including nocturnal anthesis and pale white to greenish, modestly
spreading corollas, prevail everywhere.
Tillandsia utriculata var. utriculata ranges through the same part of
northeastern Mexico occupied by T. utriculata var. pringlei (formerly T.
pringlei, but synonymized by Mez in 1896), where they differ in size, aspects
of leaf, in¯ orescence and ¯ oral morphology, capacity to produce ramets,
and substrates. Gardner (1982) considered the second variety a diminutive,
relatively xeromorphic, epilithic derivative of the more broadly distributed,
predominantly arboreal T. utriculata var. utriculata. A third, closely related
and according to some authorities conspeci® c saxicole, T. karwinskyana,
constitutes an even more stress-adapted lithophyte. Also Mexican, it differs
from T. utriculata var. pringlei by still shorter stature (,60 cm vs. up to
1.25 m), an even more abbreviated in¯ orescence, a broader, more ornamented trichome shield, precocious ramets, and unvarying saxicoly. All
three taxa hybridize freely, and in some combinations cross with additional,
more distinctly differentiated taxa (e.g., T. makoyana; Gardner 1984).
These three taxa suggest that rocky substrates encouraged lithophytic
populations to diverge from epiphytic stock suited for more equable conditions. Outcomes varied, enough change occurring in some instances to
justify varietal designations. Smaller stature and condensed (unbranched
or sparingly branched vs. bi- to tripinnately compound) in¯ orescence
within this complex may re¯ ect the more meager supplies of litter on rocky
substrates compared with bark, and greater exposure to desiccation.
Caulescence and abundant sympodial branching accords with greater
opportunity for extended survival on rock compared with bark (Fig.
2.10M,N). Flowers and pollination biology remain relatively unchanged
compared with shoot architecture and tendency to clone. Evidence of
similar transitions from bark to rock, and perhaps back to epiphytism,
exists elsewhere in the genus (e.g., T. fasciculata).
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Reproduction and life history
Saxicolous and arboreal habits and plant architecture distinguish closely
allied genotypes elsewhere in Bromeliaceae. Saxicolous populations within
some Quesnelia species also exhibit longer-stemmed shoots than the otherwise similar epiphytes. Moreover, in some instances (e.g., Q. testudo), plants
¯ ower less regularly if rock-dwelling rather than epiphytic. However,
Bennett' s example and the Tillandsia utriculata complex illustrate just one
of the two modi® cations for saxicoly among the bromeliads. Stable media
also favor monocarpy and extraordinary large size as illustrated by
Tillandsia grandis and several Alcantarea species (Figs. 1.2C, 7.1D).
Demography
Several accounts, in addition to those provided by Gardner (1982) and
Bennett (1991), describe aspects of the demography of one or more populations of bromeliads, and some of these reports include data on recruitment and survivorship. Epiphytes predominate, with Tillandsia paucifolia
heading the list (Figs. 1.3C, 6.7). Figure 6.8 illustrates statistics for colonies
supported by Taxodium distichum in the Big Cypress National Preserve of
southern Florida. Benzing (1978b, 1981a) also observed germination in
culture and in situ and the fates of seedlings over four successive seasons.
Hurricane Andrew provided an exceptional opportunity in 1993 to observe
the impact of a major tropical storm on this same epiphyte and several of
its relatives in the southern part of the same state.
Recruitment
Seeds of Tillandsia paucifolia arti® cially secured to the bark of trees in
Florida performed much as naturally dispersed progeny do. Test patterns
consisted of 12 groups of four seeds, comas intertwined, affixed with glue
in two parallel rows (Fig. 6.2D). Rainfall soon effected the intimate contact
with substrates that seeds need to germinate. A small subset of supports
accounted for most of the year-old survivors, which totaled less than 4% of
the more than 6000 seeds sown each spring between 1978 and 1981 (Table
6.11). Trees with few or no spontaneously occurring epiphytes failed to
accommodate more than the occasional tested seed. Consistent success or
failure on speci® c parts of the most suitable trees indicated that hospitality
also varied on the best hosts, probably owing to ® ne-grained differences in
exposure to light and precipitation.
Taxodium distichum proved to be the most favorable tree of the tested
species for T. paucifolia, consistent with its heavy use by most of the other
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Demography
309
Figure 6.8. Size/age structure of colonies of Tillandsia paucifolia in the crowns of
dwarfed cypress trees in south Florida censused over three consecutive years. See
caption for Fig. 6.7 for descriptions of the nine size/age classes (after Benzing
1981a).
Cambridge Books Online © Cambridge University Press, 2009
Table 6.11. The fate of 6000 seeds of Tillandsia paucifolia attached to the bark of diverse trees in south Florida after
one year
Phorophyte(s)
Number of
patterns
exposed
Number of
patterns
shaded
Number of
seeds
tested
Number of
seedlings
produced
Sanibel Island live oak forest
Quercus virginiana
Forestiera segregata
Bursera simaruba
Myrsine guianensis
0
0
0
2
5
3
1
2
500
300
100
400
0
0
0
6 (on 2 exposed trunks)
Sanibel Island mixed mangrove forest
Avicennia germinans
Conocarpus erecta
Ficus aurea
Rhizophora mangle
0
0
0
0
3
4
1
5
300
400
100
500
0
0
0
0
Avicennia germinans
Bursera simaruba
Conocarpus erecta
Ficus aurea
Rhizophora mangle
4
2
3
0
0
2
1
2
1
5
600
300
500
100
500
57 (on 2 exposed trunks)
0
11 (on 1 exposed trunk)
0
0
Bursera simaruba
Forestiera segregata
1
4
0
0
100
400
0
1
Taxodium distichum
9
0
900
110 (on 8 trunks)
Habitat
Sanibel Island mixed mangrove/
shell mound community
Sanibel Island coastal strand
shrub community
Dwarfed cypress forest on mainland
Source: After Benzing (1978b).
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311
Demography
Table 6.12. Percent germination of Tillandsia paucifolia seeds after
14 weeks under various misting regimens while attached to cut limbs of four
supports. Each sample group comprised 100 seeds
Misting regimen (30-min application)
Support
One/day One/2 days One/4 days One/6 days
Bursera simaruba
Conocarpus erecta
Rhizophora mangle
Taxodium distichum
32
33
22
23
35
17
24
21
25
21
26
18
7
6
20
9
Source: After Benzing (1990).
local bromeliads and epiphytic orchids (Table 6.11). Conversely, Ficus
aurea failed to nurture even one of the hundreds of seeds glued to its
smooth, stable bark over the four-year survey, perhaps for the same reason
that extracts of this tree inhibited germination of the orchid Encyclia tampensis in another study (Frei and Dodson 1972). Bursera simaruba, at best
an occasional substrate for Florida Bromeliaceae, and then only in cracks
and knotholes, regularly shed bark in small fragments, often with test subjects attached (Fig. 7.7F). Both Bursera and Ficus retain considerable
foliage most winters in Florida, rendering their crowns darker and therefore even less suitable for heliophilic Tillandsia paucifolia than those of fully
deciduous cypress. Controls affixed to cedar lathe and maintained under a
daily greenhouse mist regimen germinated at .90% during each of the four
years.
Tillandsia paucifolia seeds performed much as they had in situ while
attached to 6± 9 cm30.5 m sections of limbs following the technique utilized for securement to trees in Florida. Examined supports included
Taxodium, two occasional phorophytes (Rhizophora mangle and
Conocarpus erecta) and Bursera simaruba. Timers activated a misting
system for 30 min every 1, 2, 4 and 6 days, after which bark surfaces bearing
seeds air-dried within 3± 4 h and even sooner on sunny days. Between 6 and
35% of the 100 seeds representing each treatment germinated within 14
days (Table 6.12). Except for those on Rhizophora, which experienced fairly
consistent success, seeds performed best under the three wettest regimens.
Growth following germination also measures performance, and dryness
depressed epiphyte vigor on all four of the tested phorophytes. Subjects
irrigated just once every sixth day grew to only 10± 20% the size of those
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312
Reproduction and life history
Figure 6.9. Survivorship among four cohorts of Tillandsia paucifolia seedlings that
had germinated while glued to the bark of Taxodium distichum in south Florida
(after Benzing 1990).
individuals subjected to the two wettest treatments. Seedlings misted every
fourth day grew somewhat faster, but only at about half the rate exhibited
by subjects moistened each or every other day. Persistent seed coats and
intertwining coma hairs precluded more precise quanti® cation of seedling
size (Fig. 6.5G).
Survivorship
Two techniques served to document the life history of T. paucifolia in
Florida: continued surveillance of the year-old survivors of the seed germination exercise, and censuses of naturally established colonies occupying
other Taxodium distichum specimens in the same region (Benzing 1978b,
1981a). Results from one site in the Big Cypress National Preserve exemplify those for the entire sample (Fig. 6.9). Each spring from 1978 through
1981, 480 seeds had been sown on the trunks or large limbs of the same 10
trees. Revisits the following year revealed survivors in every cohort,
although 1979 brought the greatest success (Fig. 6.5E). Here, as at all the
other sites that witnessed some germinations, survival increased dramatically following heavy mortality during the ® rst few years of life. Dried
remains de® ed determinations of causes, which were probably drought,
frost or pathogens. Other seedlings simply vanished. No plants ¯ owered
during the experiment, although several eight-year-olds appeared close to
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Demography
313
maturity on the last visit. Uneven growth, presumably related to site quality
and competition among survivors in the same test patch, caused the sizes
of equal-aged plants to differ several fold.
Tillandsia paucifolia anchored on randomly felled, 85± 200-year-old
dwarfed cypress trees in a single, mixed Pinus/Taxodium forest provided the
life table data illustrated in Fig. 6.8. Values recorded for each year represent
plants distributed among 10± 15 cypress crowns harvested during each of
three consecutive winters. Mean numbers of residents per tree differed
among years in part because epiphyte density varied systematically across
the sampled forest. However, apportionments among the age/size classes
remained fairly constant. Phorophyte age determined by growth rings
failed to predict the demographic structures of the resident colonies of bromeliads.
Categories A (de® nite ® rst-year seedlings) and H± I (adults), more agediverse groups, usually contained fewer individuals than those between A
and H (Fig. 6.8). When numbers exceeded 10 per phorophyte (Table 6.13;
tree number 6), most young of the year clustered within a meter or so of a
putative maternal parent ± a plant that had fruited the previous season.
However, the presence of a plant (or plants) with a spent infructescence in
a crown one winter did not assure the occurrence of yearlings there the
next. During the 1979/80 and 1980/81 seasons, 99 of 116 new recruits on 20
trees possibly originated from one or more post-fruiting adults sharing the
same support. Those 17 others must have been fugitives, up to ® ve on a
single tree, that arrived from parents in other crowns.
Two trees that harbored fruiting individuals in 1978 or 1979 supported
no one-year-old seedlings the next season, whereas other trees with the
same history bore 1± 36 such juveniles. Plant structure that indicates how
many fruits had been produced on an infructescence deteriorates too
quickly to estimate the size of a seed source, which in the area studied could
be just one capsule per plant to about 20. The largest specimens harvested
for the survey were ripening up to 12 capsules, with less than three as the
average. During 1981, the only year that seeds were counted, 11 fruiting
specimens yielded 15 capsules containing in all about 1500 seeds.
Category B juveniles, second-season young perhaps augmented by the
occasional slow-growing third-year seedling, remained aggregated and
numerically diminished compared with those of category A. Little clustering remained among specimens large enough to qualify for category C.
Here, larger numbers and more uniform occurrences among hosting
crowns re¯ ected additional convergence by plant size involving parts of
four to ® ve, perhaps even more, successive cohorts. Reduced numbers of
Cambridge Books Online © Cambridge University Press, 2009
Table 6.13. Age structure of colonies of Tillandsia paucifolia on 10 dwarfed Taxodium distichum trees determined in
January 1980
Age/size
category (mm)
A 0± 3 (young of the year)
B 4± 5
C 6± 10
D 11± 15
E 16± 20
F 21± 30
G 31± 50
H 501
Nonfruiting adults
Fruiting adultsb
Total juveniles
Total adults
Total epiphytes
Host age (years)
Host number
1
2
3
3
16
29
10
7
7
9
1
1
2
82
3
85
Ð
4a
32
25
14
3
3
3
3
3
2
87
5
92
75
2
5
10
4
5
5
7
1
0
2
39
2
41
49
4
0a
18
43
12
4
7
7
4
1
1
92
2
97
117
5
6
0
2
21
8
3
9
5
0
0
1
48
1
49
Ð
36a
3
36
3
2
6
7
4
4
0
94
4
98
67
7
8
9
10
Mean6standard error
1
18
15
12
5
9
4
4
4
0
66
4
70
131
5
7
35
21
7
10
13
2
2
4
102
6
108
65
5
8
21
34
22
18
15
0
0
2
125
2
127
140
0
72
43
13
7
8
3
0
0
1
149
1
150
160
5.66 3.4
18.1 6 6.71
27.8 6 3.61
13.1 6 2.81
6.5 6 1.8
8.2 6 1.3
7.3 6 1.3
2.16 0.4
1.560.5
1.560.4
83.46 12.6
3.0 6 0.5
91.76 10.5
Source: After Benzing (1981a).
Notes: aTree bore one or more fruiting epiphytes the year previous to census. bIncludes both seedling adults and asexual adults in fruit.
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Demography
315
individuals overall, and additional dispersion through categories above C,
re¯ ected age-related, accelerated growth in addition to continuing attrition.
Category C' s numerical superiority could, of course, signal extraordinary
reproductive success between 1970 and 1975.
Trees examined in the winters of 1979/80 and 1980/81 supported on
average 2.8 adults, including 1.3 in fruit. Fourteen of the 26 specimens
bearing capsules showed no evidence of prior reproduction. The remaining 12 bore vestiges of spent ramets suggesting that mortality, while
highest in young plants, continues to be substantial thereafter. Because
about one out of every four fruiting subjects had not reproduced before,
life expectancy following maturation appeared to average about three more
seasons.
Bennett (1986a) reported 4± 16% attrition, often caused by detachment,
among individuals comprising populations of Guzmania monostachia and
three Catopsis species in Taxodium/hardwood forest in south Florida.
Losses for Catopsis berteroniana approached 30% for the full year, enough
theoretically to require complete replacement in three to four times that
interval should all the individuals be actuarial equivalents. In fact, most of
the casualties had not fruited. Clearly, some exceptionally long-lived fraction of the local colony constituted the effective population, or parents in
adjacent habitats were supplementing the local seed supply.
Hietz (1997) conducted a two-year study of site and age-related mortality among Catopsis and Tillandsia populations in humid montane forest in
Mexico. His ® ndings suggest that certain aspects of substrates in¯ uence the
probability of survival to reproduction. Consistent with ® ndings for the
other Bromeliaceae studied, survivorship increases with plant size.
Individuals less than 2 cm in length experienced 0.33 survivorship, while
that number for plants longer than 15 cm had diminished to 0.06. Mortality
caused by factors other than branch fall, the leading cause of death,
increased with branch diameter, possibly re¯ ecting reduced access to light
toward the center of occupied crowns. Perhaps growth to maturity requires
that seeds germinate on twigs sturdy enough to support the resulting adult,
but not so thick as to virtually assure local environments that kill attached
bromeliads before they can reproduce.
Although slow-growing, Tillandsia paucifolia colonizes dwarfed cypress
fairly rapidly, after which populations mostly accrete from adults anchored
in the same crowns. Upward limits on plant densities may exist, but if so
their nature remains obscure. Conceivably, most of the unoccupied substrate that outwardly seems comparable to utilized bark in the crown of a
dwarfed cypress tree in south Florida is in fact hostile as the germination
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316
Reproduction and life history
tests suggested. Or perhaps disturbance, periodic freezes and ® res in
addition to modest reproductive power hold numbers well below carrying
capacities, as Benzing (1981b) suggested by imputing operation of a
lottery-type mechanism.
Findings on T. paucifolia in Florida underscore why so few additional
arboreal plants share the canopies of dry, tropical American forests with
Type Five Bromeliaceae. Most members of this family, like vascular epiphytes in general, simply lack the necessary stress-tolerance to survive even
on the most accommodating substrates there. Colonists of these sites obviously possess exceptional hardiness, but drought still probably kills more
seedlings than any other agency, with resistance increasing markedly with
body mass. Conversely, disturbance exacts a more random toll because substrates of all ages and conditions, including those near failure, intercept
seeds and then end the lives of all the epiphytes they eventually carry to the
ground.
Tillandsia paucifolia further illustrates what may be exceptional behavior
for a perennial xerophyte. According to data collected during the 1978± 81
seasons, rates of establishment are modest, but consistent compared with
some similarly slow-growing desert ¯ ora. For example, certain Agave
species recruit seedlings less than one year in 10 (e.g., Turner et al. 1969),
as do some cacti. However, once a juvenile reaches threshold size, a feat
contingent on close proximity to a nurse plant, life usually continues to
maturity. Other bromeliads (e.g., Vriesea neoglutinosa and Neoregelia
cruenta in certain Brazilian restingas) may more closely parallel these terrestrials (McWilliams 1974), as does Puya dasylirioides and Andean P.
clava-herculis (see below). Grubb et al. (1963) observed that 70± 80% of the
arboreal bromeliads in humid montane sites in Ecuador were immature,
while percentages in much drier forest fell well below these values.
McWilliams (1974) noted similar disparities along moisture gradients in
southeastern Brazil.
Results from Augspurger' s (1985) multiyear survey of Puya dasylirioides
and the information on Tillandsia paucifolia provide opportunity to
compare the consequences of polycarpy for a terrestrial vs. an epiphytic
bromeliad. More signi® cantly, these two species illustrate certain variations
on that life cycle speci® c to widely different circumstances, and, presumably, associated constraints on plant success. Rather than cypress tree
crowns in seasonal, subtropical forest, Puya dasylirioides inhabits sphagnum bogs, and, less frequently, rocky slopes at 2100± 3000 m in Costa Rica' s
highest mountains of the Talamanca range. Although both species produce
axillary offshoots from determinant ramets and incur greatest mortality
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Demography
317
Figure 6.10. Numbers of ¯ owering individuals within a single population of Puya
dasylirioides in Costa Rica over eight consecutive years (after Augspurger 1985).
during the ® rst year of life, they differ in important aspects of recruitment
and survivorship and the reproductive performances of genets.
Unlike the 7± 10 years a Tillandsia paucifolia specimen needs to mature,
seedling shoots of P. dasylirioides ¯ ower on average after 36 years, and do
so with near certainty once a plant survives through the 12 seasons required
to achieve or exceed the minimum shoot diameter of about 11 cm (Fig.
6.11). Populations also behave differently. Rather than the relatively steady
¯ owering exhibited by colonies of Tillandsia paucifolia in Florida, Puya
dasylirioides ¯ owered less regularly, 38± 323 plants per year, each specimen
bearing 50± 1224 capsules (Fig. 6.10). Rosettes that became sexual over a
range of sizes (rosettes 20± 70 cm wide), and seed crops that increased exponentially with that metric, largely accounted for the uneven fecundity
among fruiting individuals (Fig. 6.11).
Most telling of the features that distinguish the reproductive behavior of
these two bromeliads is the timing of branching relative to ¯ owering.
Contrary to the pattern seen in Tillandsia paucifolia and most of the other
bromeliads native to the forest canopy (Fig. 6.7), Puya dasylirioides produces ramets earlier, before rosettes reach 10 cm, about one-half the
minimum diameter required to bolt. However, many individuals, especially
those on rocky substrates, either fail to branch, or overtopped ramets die
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Reproduction and life history
Figure 6.11. Probability of survival of Puya dasylirioides plants during a four-year
period relative to rosette diameter at the beginning of that interval. Note that mortality approaches zero after shoot diameter reaches 11± 20 cm. Black bars indicate
plants that were already large enough to ¯ ower when the study was initiated (after
Augspurger 1985).
rendering the genet de facto monocarpic. On ® rst consideration, exceptionally high juvenile mortality and far less vulnerable adults suggest that polycarpy rather than monocarpy constitutes the superior reproductive strategy
for this species. However, some additional plant characteristics that in¯ uence seed production also need to be considered.
Augspurger speculated that P. dasylirioides combines certain advantages
of both mechanisms to match local growing conditions. Its long-lived
ramets produce the massive seed crops that only an extended life cycle
permits on the infertile, often sodden, cold substrates these plants utilize.
By also branching precociously, the average genet is more likely to produce
the requisite large seed crop than could a more typically polycarpic bromeliad constrained by the same harsh growing conditions. For example, if
Tillandsia paucifolia were to operate under the same environmental con-
Cambridge Books Online © Cambridge University Press, 2009
Demography
319
straints, fecundity would fall because its renewal meristems remain
dormant until the parent module bolts. Ramets produced by Puya dasylirioides provide different service that requires earlier appearance; they act as
replacements for failed meristems rather than devices to permit the successful genet to produce repeated modest crops of seeds over successive
seasons. After reaching threshold size, surviving shoots eliminate the
weaker ramets, which at this point no longer serve a purpose anyway.
One interesting question remains unanswered. Ramet production
appeared to be site-speci® c. Perhaps this tendency indicates polymorphism
or plasticity to match growing conditions, particularly substrates, that
impose different rates of mortality on this bromeliad across its heterogeneous montane habitats. Precocious branching is the appropriate response
where seedling shoots often die before becoming too large to allow ¯ ushed
axillary buds opportunity to survive long enough to ¯ ower instead.
The same logic offered to explain the reproductive biology of P. dasylirioides may explain the early production of tiny offshoots by predominantly
monocarpic Bromeliaceae native to rocky substrates (e.g., lithophytic
Alcantarea regina, Tillandsia rauhii, T. clavigrea, T. krukoffiana; Figs. 1.2C,
2.11B).
Catastrophic mortality
Certain members of Cryptanthus, Dyckia and Encholirium native to the
`campos rupestres' of southeastern Brazil, Ayensua and Brocchinia melanacra of similar habitats in the Guayanan highlands, Hechtia in Mexico, and
some Andean Puya, among others, resist ® re with thick mantles of persistent, insulating leaf bases (Figs. 2.2G, 6.12C± E, 14.3B). Termite carton regularly provides additional shielding in some regions (Fig. 8.1E). None of
the arboreal types possess similar accouterments, with devastating consequences in certain formerly less ® re-prone habitats. Today, for example,
little evidence remains of Catopsis berteroniana and the four to ® ve
Tillandsia species that densely colonized cypress forest in southwest Florida
prior to the installation of a drainage grid designed to lower the water table.
Plant collectors bear some responsibility, but careless smokers, deliberate
arson and the US Army Corps of Engineers assured the ® nal, devastating
outcome.
Findings by Rocha et al. (1996) and Alves et al. (1996) in Brazil underscore the vulnerability, at least over the short term, of terrestrial
Bromeliaceae native to generally ® re-free ecosystems. Only about 0.1%
of the shoots of Vriesea neoglutinosa comprising dense colonies
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Reproduction and life history
Figure 6.12. Fire and Bromeliaceae. (A) Colony of Neoglaziovia variegata following
® re in Bahia State, Brazil. (B) Caatinga, a ® re-prone community that hosts bromeliads in Minas Gerais State, Brazil. (C) Unidenti® ed Encholirium sp. that survived
® re at the same site illustrated in B. (D) Hechtia schottii displaying how ® re burns
away the dead leaves without killing the thick stem in Yucatán State, Mexico. (E)
Unidenti® ed Encholirium sp. following ® re in Minas Gerais State, Brazil.
(12493 ramets ha21) in a 210 ha patch of restinga surrounded by Atlantic
Forest appeared to be alive following a burn set by local farmers. Fifteen
months later, regeneration had elevated the number of viable shoots to 3483
ha21, about a 28% recovery (Alves et al. 1996). No mention was made of
the tank occupants (arthropods) whose numbers in the same bromeliads
scorched by ® re had been reduced about 67%.
Many Aechmea bromeliifolia and A. phanerophlebia specimens are seriously injured or killed by ground ® res that may be more common today in
certain campos rupestres sites (personal observation). Patchy distributions
that locate plants away from the dead grasses and other ¯ ammable phytomass scattered through these thinly vegetated sites further suggest recurrent
burns. Figure 6.5B illustrates how seedlings of Bromeliaceae and certain
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Demography
321
other taxa take advantage of the insulation and perhaps protected supplies
of moisture provided by rocks in Brazil' s campos rupestres.
Bromeliads through much of Mesoamerica probably experience catastrophic storms more often than killing ® res. Between 1871 and 1964, 0± 11
hurricanes per year crossed the Caribbean (Walker 1991), sometimes
in¯ icting damage visible for decades. Studies underway in Puerto Rico and
elsewhere aim to document succession following several recent events, but
plans target woody rather than epiphytic ¯ ora. Information for
Bromeliaceae consists largely of an account of the fate of a small sample
of T. paucifolia in the Everglades National Park plus observations on some
relatives on nearby taller cypress, and populations elsewhere in Florida
(Lowman and Linnerooth 1995). Craighead (1963) considered hurricanes
an important threat to that state' s epiphytes after witnessing storms like
Hurricane Donna in 1960 that killed an estimated 90% of the bromeliads
at certain coastal sites. Conversely, T. usneoides may owe its unusually
extensive range through Mesoamerica largely to the powerful winds generated by these massive tropical disturbances.
Hurricane Andrew, a Class Four storm that crossed extreme south
Florida in August 1992, in¯ icted considerable damage on local
Bromeliaceae. One impacted colony of Tillandsia paucifolia contained ,75
mapped plants anchored on 28 dwarfed cypress trees located about 40 km
inside the eastern border of the Everglades National Park. Each epiphyte
was identi® ed by a metal tag either secured around a nearby branch or
nailed to the trunk. All of these plants belonged to age/size class H (prefruiting adults) or fruiting adults and by then had experienced attrition
from the initial sample of 100 individuals. The third annual visit in
December 1992 to record mortality and reproduction revealed no uprooted
hosts, but many broken limbs and smaller axes. Only 40 plants or their
anchorages could be relocated. Of the 18 surviving bromeliads, eight had
been fruiting at the time and of these only four continued to bear one or
more ripening capsules (Fig. 6.13B).
Larger (,8± 10 m) Taxodium distichum specimens comprising a cypress
ª domeº community on deeper, organic soil near the site just described sustained greater damage than the more dispersed, better-anchored trees
bearing the tagged epiphytes. Many trunks stood askew, but still supported
viable Tillandsia fasciculata, T. balbisiana and T.3smalliana (Fig. 6.13A).
Here as well, stiff foliage remained largely intact despite winds that
exceeded 240 km h21 at a coastal monitoring site some tens of kilometers
to the east. Shoots of about 10, thinner-leafed, phytotelm Catopsis berteroniana comprising a colony anchored on tall shrubs approximately 15 km
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Reproduction and life history
Figure 6.13. Hurricane damage in south Florida. (A) Damage caused by Hurricane
Andrew in August 1993. Note that many clumps of Tillandsia fasciculata remain
intact in the crowns of still upright Taxodium distichum. (B) Damage, including
aborted capsules, incurred by a tagged Tillandsia paucifolia specimen still anchored
on a dwarfed Taxodium distichum tree near the cypress `head' illustrated in A.
east of the cypress sites incurred extensive damage, and several moribund
specimens dangled upside down on broken twigs. However, here too survivors can probably rebuild the population.
Oberbauer et al. (1996) also assessed the damage in¯ icted on Florida
Bromeliaceae by Hurricane Andrew. Demographic surveys of the epiphytes, including ® ve species of Tillandsia, residing in three cypress dome forests
were conducted about 10 months after the storm. Several factors, including
the type of substrate and the identity of the epiphyte, particularly its rooting
characteristics and size, determined survival. Mortality also varied among
domes, with the largest stands offering the greatest protection to resident
arboreal ¯ ora. Tillandsia balbisiana and T. usneoides proved most vulnerable, but still lost relatively few members of their comparatively dense populations. Preference for smaller twigs in the ® rst instance, and the absence of
a root system in the second, probably contributed to these outcomes.
Post-storm densities (all ages) for the other three species (T. paucifolia, T.
recurvata, T. utriculata) sometimes exceeded those recorded before
Andrew' s arrival (different transects were used). Young plants, possibly
encouraged by the additional light that penetrated the damaged canopy,
supposedly accounted for the difference. However, failure to distinguish
between newly germinated and surviving seedlings in the assessments of
affected populations lessens opportunity to appraise Overbauer et al.' s
results and conclusions.
Loope et al. (1994) also surveyed vegetation along the path of Hurricane
Andrew, and noted that the vascular epiphytes incurred greater mortality
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Asexual reproduction
323
than plants of any other habit. Up to 90% of the population had succumbed at the most impacted sites, but even here enough stock remained
for recovery. Surviving bromeliads appeared to be more susceptible to sun
scalding than co-occurring Orchidaceae. Canopies opened by high wind
will both exacerbate the effects of frost and favor those species that require
high exposure (e.g., Catopsis berteroniana, many Tillandsia species).
Mounting evidence suggests that while powerful hurricanes sometimes
fell entire stands of trees, especially on ridge lines and along marine coasts,
recovery begins immediately, mostly by trunk sprouts (Walker 1991). If representative, observations on several species in south Florida indicate a
similar dynamic for epiphytic Bromeliaceae ± that populations mostly regenerate from survivors, largely obviating needs for immigrants or seed banks.
Asexual reproduction
Although Bromeliaceae probably arose from ancestors equipped with the
same modular design featured by most extant lineages (e.g., Figs. 2.2D, 2.3,
6.7), propensities to branch range from nil for the few monocarps to prodigious (e.g., Abromeitiella, some saxicolous Tillandsia; Fig. 2.20). Relative
emphasis on asexual vs. sexual reproduction among the iteroparous types
re¯ ects genetic program and environment. Certain Aechmea magdalenae
populations may rarely ¯ ower because indigenous farmers selected exceptionally proli® c, subsexual genotypes to promote ® ber production. Excess
shade suppresses sexual reproduction more than vegetative growth in relatively heliophilic genotypes like Catopsis berteroniana. Likewise, Bromelia
humilis seldom ¯ owers, and most of its ramets abort if located in certain
overexposed Venezuelan coastal habitats (Lee et al. 1989). Several saxicoles
(e.g., Aechmea wittmackiana, Quesnelia testudo, Vriesea philippo-coburgii)
remain predominantly asexual everywhere, perhaps for the same reasons
imputed earlier as adaptive behavior for certain rock-dwelling Tillandsia.
Patterns vary within species. Recall that Tillandsia utriculata is monocarpic
in Florida, but iteroparous in Mexico. Tillandsia secunda produces
offshoots on infructescences and from leaf axils in northern Ecuador, but
farther south in the same country relies exclusively on seeds.
Seedling shoots of all but the monocarps typically produce one or more
ramets, usually after ¯ owering, each of which replaces itself in the same
fashion and so on ad in® nitum (Figs. 2.3, 2.11, 6.14). Stands of aggressively
vegetative species like Deuterocohnia haumanii cover hundreds of hectares
of semiarid Argentinian habitat possibly with genets up to centuries old.
Asexual activity imposes considerable structure on populations but, except
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Reproduction and life history
Figure 6.14. Five patterns of asexual reproduction (branching) among
Bromeliaceae. (1) Monocarpic/monopodial; (2) precocious basal: `grass' offshoots
only; (3) midregion axillary ramet(s) that develop following ¯ oral induction; (4)
combined features of 2 and 3; (5) axillary ramet(s) in upper region only following
¯ oral induction; (6) midregion axillary offshoots develop as plantlets propagate
from spent in¯ orescence.
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Asexual reproduction
325
for Aechmea magdalenae on Barro Colorado island and those several
Mexican relatives also subjected to genetic analysis, without much documentation. Stolon length and number appear to be especially decisive (Fig.
2.11). Those of Pseudananas sagenarius grow several meters, while
Abromeitiella illustrates the opposite arrangement required for the cushion
habit so common in severe alpine habitats (Fig. 2.20). Phenotypic plasticity further in¯ uences the shapes and sizes of genets, but to what degree
remains undetermined.
Ramets characteristic of Bromeliaceae fall into three categories distinguished by size relative to the parent shoot, site of origin along the subtending axis, and the timing of development (Figs. 2.11, 6.14). Tiny, almost
grass-like offshoots initiated long before the parent ¯ owers describe many
Tillandsia and Vriesea species (Fig. 2.11B). Ramets whose appearance is
delayed develop more robustly, usually around the time the in¯ orescence
emerges (Fig. 2.11A). Adventive offshoots characterize a far smaller
number of mostly self-incompatible taxa, speci® cally those capable of producing such plantlets in lieu of fruits (e.g., some populations of Tillandsia
paucifolia and several Orthophytum species; Fig. 2.11A).
Tillandsia species that proliferate from the in¯ orescence often scramble
over the ground, and sometimes grow into low shrubs, as does facultatively
epiphytic T. ¯ exuosa native to semiarid coastal strand habitats in Venezuela
(Fig. 2.11A). Two varieties of Tillandsia latifolia dominate vast expanses of
treeless Peruvian coastal desert according to a somewhat different arrangement. Tillandsia latifolia var. major forms relatively large rosettes, alone or
in small clusters, scattered across loose sand. Proliferative in¯ orescences
produced by its smaller relative, T. latifolia var. minor, bend forward under
their own weight to produce successive rows of progeny oriented into the
on-shore stream of life-sustaining, mist-laden sea air. Tillandsia paleacea
marches up-wind in similar fashion, unassisted by the in¯ orescence, but
leaving behind the same trails of lifeless, desiccated shoots.
Ramets of many Cryptanthus species readily disarticulate where they
constrict at the base. Those of C. acaulis detach during dry weather as
shrinking tissues and recurving foliage create sufficient tension. Poorly
developed root systems and somewhat spherical shape may combine to
foster tumbleweed-like mobility that helps disperse the abscised offspring.
Several members of Orthophytum (e.g., O. benzingii) may rely on axillary
in¯ orescences that regularly terminate as plantlets to colonize patches of
soil on typically rocky substrates like those illustrated in Fig. 7.1. Elongate,
initially upright shoots tend to bend or twist downward reminiscent of stoloniferous Rubus and similar plants notable for spreading clonal growth.
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Reproduction and life history
Final comments
Many aspects of bromeliad reproduction match important aspects of environments like the stability and resource richness of their diverse, often
unusual substrates. Vigorous ramets and comparatively modest seed production often accompany occurrences on rocks and stable soils like those
that support many of the saxicoles and Aechmea magdalenae respectively.
The generally more ephemeral and widely dispersed anchorages of the epiphytes oblige greater plant mobility than ramets provide, so seed production predominates and genets remain relatively compact. Malthusian
coefficients (r), viz. expressions of the mathematical function that describes
unconstrained population growth, provide more precise indicators of the
selective pressures that shape life history and plant architecture in situ.
Values for r vary among populations; so does l (realized growth rate)
among identical populations in different circumstances. Many plant qualities in¯ uence r, including seed size and reproductive allocation. Numerous
additional factors affected by environment, such as the probability of fruit
set and the fate of progeny, in turn establish l below r. Bromeliaceae vary
substantially on many of the plant-based factors, one of the major exceptions being reproductive schedule, which for the vast majority of species is
iteroparous. Another explanation beyond the descriptive one provided
earlier to explain this bias reveals more precisely why polycarpy greatly
exceeds the incidence of monocarpy through the family.
If the members of two populations share the same inherent features that
in¯ uence r except for time required to mature, the more precocious population compared with that slower to fruit will potentially grow faster even
though individuals in the second case can become larger and invest more
biomass in seeds (Cole 1954; Stearns 1976). Likewise, populations of
monocarps potentially expand faster than those of otherwise identical
plants programmed for sequential reproductive efforts because the polycarp must retain signi® cant reserves to continue the genet. Environment
comes into play in these comparisons as well. Time is needed to produce
seeds from basic resources, but the interval (juvenile stage) required to
accomplish this transformation varies with the organism and its circumstances. Habits (e.g., roots present or absent), photosynthetic pathway as it
affects Amax and water balance, and the availability of key resources, among
other factors, also affect outcomes by in¯ uencing rates at which raw materials like CO2 and moisture are acquired and converted to phytomass and
eventually offspring.
Two species help illustrate why reproductive schedule is strongly biased
toward iteroparity among the bromeliads. Florida Tillandsia utriculata rou-
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Final comments
327
tinely sets self-seed, and its phytotelm shoots collect enough moisture and
litter to support the obligatory massive seed crops (.10000) to sustain populations as a monocarp. Polycarpic Tillandsia paucifolia co-occurs with T.
utriculata, but subsists on a more modest resource base consistent with the
greater stress-tolerance required for Type Five status. Similarly exhaustive
fruiting would disadvantage T. paucifolia even if reproduction continued to
occur in about one-half to one-third of the 15± 20 years T. utriculata
requires to ¯ ower. Seed crops would remain modest, probably less than
1000 units (in up to 6± 8 capsules), and far below what is needed to maintain populations such as those monitored in Florida.
Much more than 15± 20 years would be needed for Tillandsia paucifolia
(no phytotelma) to marshal the reserves a tank bromeliad like T. utriculata
(phytotelm present) commits to its single massive seed crop. Recall that
attrition, while highest in the ® rst few years of life, continues after maturity. Dislodgements and other lethal events related to the relatively ephemeral nature of bark would probably doom just about any population of
epiphytes whose members needed, as do some of the terrestrial monocarps,
decades to mature (e.g., Puya dasylirioides).
Schaffer and Gadgil' s (1975) model demonstrates the relative advantages
of semilaparous (monocarpic) vs. iteroparous reproduction by otherwise
identical bromeliads. Equation 6.1 expresses the rate lm at which a population of monocarpic (m) individuals ± here exempli® ed by T. utriculata ±
multiplies:
lm 5CBm.
(6.1)
The notation C enters the probability that the average seed will survive to
reproduce; B is the mean number of seeds ripened annually by each population.
For polycarpic T. paucifolia, the corresponding l is determined by
Equation 6.2.
lp 5CBp 1P.
(6.2)
Here, P represents the probability that an adult will survive from one reproductive season to the next to potentially achieve multiple seed crops. Again,
B denotes the size of the population' s annual seed crop. Because seeds
succeed with equal frequency in this comparison, C has the same value in
both cases. Equating rate expressions 6.1 and 6.2 and dividing through by
C produces Equation 6.3:
P
Bm 5Bp 1 .
C
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(6.3)
328
Reproduction and life history
According to Schaffer and Gagdil, in order for the population of monocarps to multiply as fast as another assemblage representing an otherwise
identical polycarp, Bm must exceed Bp. Performance in Florida indicates
how much larger seed crops would have to become to accommodate such
an adjustment by T. paucifolia. Few juveniles survive to fruiting there (C5
,0.001, whereas P is probably .0.7). A mature specimen ripens between
100 and 300 seeds (1± 3 capsules) each reproductive season, whereas
Bennett' s ® gure for T. utriculata tops 13000 for its single, suicidal, reproductive effort. Should circumstances change such that adult survivorship
diminishes ± that is, if multiple fruiting threatens the viability of the population (P becomes smaller) more than the failure of juveniles ± the bene® ts
of monocarpy, and hence the likelihood of its evolution, increase. Single
bouts of seed production become sustainable only if P/C falls to what
among Bromeliaceae must be an extraordinarily small value.
Several plant characteristics, including seed weight ± about 25% higher
for T. utriculata than for T. paucifolia, vitiate our hypothetical comparison
of these two bromeliads. A better-provisioned embryo potentially improves
survivorship, in this case granting T. utriculata corresponding greater facility (suitability) for monocarpy. Mobility may further compromise our
model according to Bennett' s (1991) discovery that T. utriculata seeds
possess unusually long comas. Evidence on hand points to the sizable
resource base and related capacity to produce large crops of relatively
expensive, mobile seeds as requisites for monocarpy in Tillandsia; superior
ability to counter agencies that depress C, principally aridity, seems less
likely to affect reproductive success as much. Tillandsia utriculata also
exceeds T. paucifolia in shade-tolerance and probably range of acceptable
substrates.
Values for P and B shift most dramatically where extensive clonal growth
mitigates the need for abundant, sexually produced offspring. Widely available, durable substrates encourage spreading, iterative growth most of all
(e.g., wetland Typha and Spartina). Numerous small, vagile seeds characterize much of this ¯ ora, but they do little to help maintain the established
population. Some Bromeliaceae ® t this pattern as illustrated by saxicolous
vs. arboreal Tillandsia, particularly the strongly asexual, caulescent types.
Certain Aechmea, Bromelia, Neoglaziovia, Neoregelia and Quesnelia of
rocky, coastal and other expansive and stable habitats also exhibit life histories and architectures that most closely approach the cat-tail type, and
probably for the same reasons.
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7
Ecology
Considerations of the relationships between Bromeliaceae and climate and
substratum emerge repeatedly in the chapters devoted to plant structure,
physiology and reproduction. Nevertheless, many aspects of ecology either
go unmentioned or warrant greater attention in a monograph that claims
adaptive radiation as its central theme. This chapter and the following one
address this de® ciency by revisiting the diverse and often demanding
growing conditions experienced by the bromeliads through tropical
America. It also raises the less familiar issue of how hosting ecosystems
owe many of their important attributes to the presence of these often keystone species. Chapter 8 highlights many of the most intimate associates of
the bromeliads, namely their pathogens and predators, and especially the
mutualists.
Several facts in addition to our focus on evolution oblige the emphasis
on ecology. First, dense populations of epiphytic Bromeliaceae and companion ¯ ora demonstrably in¯ uence the structure, economy and carrying
capacity of many Neotropical forests. The terrestrials in turn sometimes
constitute much of the understory, and where trees are scattered or absent
they may dominate entire ecosystems. A number of saxicoles achieve near
monoculture on precipitous outcrops (Figs. 1.2C, 7.1). Finally, tankforming and bulb-producing Bromeliaceae engage in bene® cial exchanges
with a variety of nonpollinating and/or seed-dispersing invertebrates and
higher animals. Services rendered to the extensive fauna that use these
plants surely exceed in kind, if not also in abundance, those provided by
members of just about any of the other families of herbs present in the
same communities.
We begin by considering how climates and substrates in¯ uence the distributions of Bromeliaceae in space and time. Readers should consult
Chapters 4 and 5 for details about carbon, water and ion balance mechanisms (ecophysiology), because all of these phenomena mirror growing
329
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Ecology
Figure 7.1. Bromeliaceae on rocky substrates. (A) Tillandsia recurvata growing as an
epiphyte on a lithophytic shrub while nearby Tillandsia kurt-horstii is anchored just
as exclusively on the surrounding rock in south Bahia State, Brazil. (B) Unidenti® ed
Encholirium sp. featured in E dislodged to expose its extensive super® cial root
system. (C) Tillandsia tenuifolia forming a characteristic debris-collecting colony on
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Frost-tolerance
331
conditions in situ. Next, the bromeliads are treated as components of communities, with an examination of how they affect co-occurring vegetation
and interact with neighboring fauna. Our review concludes with effects on
integrative processes in ecosystems, primarily mineral cycling and energetics. Once again the epiphytes receive top billing, but only because less is
known about the terrestrials. For the moment, cultivated Ananas comosus
and related Bromelia humilis, plus a scattering of additional, soil-rooted
species, must represent this more broadly varied of the two ecologically distinct groups of bromeliads.
Frost-tolerance
Bromeliaceae range higher into montane habitats ± to above 4000 m, and
farther poleward ± than members of several other sizable, predominantly
tropical families (e.g., Arecaceae). However, relatively few populations, just
a handful including members of Tillandsia, Greigia, Chilean Ochagavia and
closely related Fascicularia, Puya (Fig. 14.2C) and a scattering of other
Pitcairnioideae, regularly experience subfreezing temperatures. Tolerance
for more protracted frost at higher latitudes is even less common. More precisely, geographic ranges, plant morphology and mostly undescribed
ecophysiology divide frost-tolerant Bromeliaceae into two categories.
Several species of Puya, and similarly long-lived `giant rosette' herbs in
several other families (e.g., Asteraceae, Lobeliaceae), comprise a convergent ¯ ora native to tropical alpine habitats around the globe (e.g., also
Africa, Hawaii). Frost and intense UV-B-enriched radiation oblige congested, highly re¯ ective foliage often invested with a dense indumentum of
woolly trichomes (Fig. 7.2). Sunrise ends the nightly cooling cycle, which if
much extended would overwhelm the well-insulated but otherwise vulnerable shoot meristem. Small size increases risk to the extent that only the rare
seedling survives beyond the ® rst year or two of life. Miller and Silander
(1991) reported that virtually every specimen of large-bodied Ecuadorian
Puya clava-herculis to reach a certain modest size eventually ¯ owers, an
achievement that requires a nurse plant, usually a tussock grass rather than
a shrub or high cushion or mat-forming type.
Figure 7.1. (cont.)
the side of a granite outcrop in Bahia State, Brazil. (D) Alcantarea sp. on a granite
outcrop in Rio de Janeiro State, Brazil. (E) A near monoculture of a lithophytic
Encholirium sp. in Bahia State, Brazil. (F) Orthophytum sp. on granite in northern
Minas Gerais State, Brazil. (G) Seedlings of lithophytic Tillandsia araujei and an
unidenti® ed Vriesea sp. illustrating the rough texture of this highly stable medium.
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Ecology
Figure 7.2. Trichome development and the relative condensations of the in¯ orescences of four Puya species along an elevational gradient in Ecuador. Puya aequatorialis experiences a mean annual temperature of 16.5 °C at 1980 m while P.
clava-herculis at 3962 m experiences 6.6 °C (® gure assembled from data provided by
Miller 1986).
Litter provided by companion ¯ ora further promotes survival among
Puya clava-herculis juveniles by insulating the soil enough to retard the formation of the ice crystals that injure delicate roots. Taller vegetation
excludes this same bromeliad at lower elevations, although conditionally
depending on ® re, which enhances its competitive performance. More sensitive Puya species respond less favorably to the same challenge. For
example, few P. raimondii specimens survive to reproduce today owing to
the increasingly common custom of setting a® re the massive skirts of spent
foliage before seeds can ripen.
None of the alpine bromeliads has received as much attention as some
similarly stress-adapted herbs in several other families. Presumably the
same growing conditions and matching plant tolerances account for the
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Frost-tolerance
333
Figure 7.3. Coupling of the temperatures of ¯ owers with that of air for Puya hamata
and Puya aequatorialis in early July after subjects representing the second species
had been relocated to the paramo habitat of higher-altitude Puya hamata (after
Miller 1986).
high-elevation, tropical distributions of all of the giant rosette species.
Information on the water relations of Espeletia (Asteraceae) and Puya
clava-herculis appears in Chapter 4. Miller (1986) demonstrated the importance of the shape and bulk of the in¯ orescence and the investing trichomes
for thermal regulation among four Puya species native to different elevations in Ecuador (Figs. 7.3, 7.4). Lowermost Puya aequatorialis var. aequatorialis (1900± 2100 m) produces a tall, spreading in¯ orescence bearing no
pubescence, whereas P. hamata and P. clava-herculis (.3400 m) feature
much more condensed and insulated arrangements (Fig. 7.2). Dense layers
of woolly light brown to white scales cover the ¯ oral bracts, almost obscuring the ¯ ower buds and developing capsules. Puya aff. vestita, consistent
with its mid-elevational (3200 m) range, exhibits in¯ orescence and trichome
development between these two extremes. Costs to plants estimated by
dividing the dry weight of the indumentum by that of the supporting ¯ oral
bract ranged from 0 to 57.8%, indicating the likelihood of substantial plant
bene® t for the most heavily endowed species.
Measurements in situ demonstrated that the two Puya species with the
thickest cylindrical spikes and densest pubescence maintained their ¯ ower
buds up to 2.4 °C warmer than adjacent night air. Additionally, thermal
equilibration after sundown took 4± 9 times longer for these high-altitude
types compared with relatives from lower elevations (Figs. 7.3, 7.4).
Daytime readings that also exceeded ambient indicated capacity for the
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Ecology
Figure 7.4. Exponential heat decay curves and time constants for ¯ owers of four
Puya species. Time constants were determined where the heat decay curves crossed
1/e5T1 20.632 (T1 2T2). This is the time required for a 63% decrease in the total
difference between organism (T1) and air temperature (T2). See Miller (1986) for
additional details.
rapid heat gain that probably favors pollen and ovule development.
Differential success between capsules on illuminated vs. shaded sides of the
same in¯ orescences (mean seed number 301.9 vs. 225.1 respectively) indicated close thermal tolerances and the importance of exposure for high-elevation P. clava-herculis.
Bromeliaceae with extratropical distributions occur in both hemispheres,
but unlike the giant rosette types, none differs architecturally from related
taxa or their own populations native to warmer habitats. Hardiness has
emerged repeatedly in different parts of the family and at widely scattered
locations. Ochagavia extends poleward to 35.5° on the Chilean mainland
and the San Fernandez islands where temperatures sometimes fall to
several degrees below zero. However, Tillandsia usneoides exceeds all contenders by a substantial margin: northernmost populations reach the 38th
parallel along the Atlantic coast of the USA, and even stronger marine
in¯ uences allow a 6° deeper penetration into central Chile. Sensitivity to the
same degrees of frost that some Puya and other bromeliads must tolerate
for only a few hours at a time in tropical alpine habitats precludes success
in all but the mildest parts of temperate zones. Still, Spanish moss occasionally freezes solid in its coldest North American habitats.
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Frost-tolerance
335
Exceptional rather than routine events probably act most decisively to set
the geographic limits of extratropical Bromeliaceae. Freezes sufficient to
boost coffee prices are fairly common in southeastern Brazil where several
large genera (e.g., Billbergia) reach farthest poleward. Few records describe
performances in situ, but cultivated materials suggest major differences
among species. For example, Wurthman (1984) reported that Vriesea (e.g.,
V. carinata, V. corcovadensis, V. guttata) tolerate frost better than members
of the same genus from the deeper tropics in southern Mexico, Central
America, and northern South America. A quick glance at the range of
Vriesea carinata mapped in Fig. 7.5 suggests why. Distribution south
through coastal Santa Catarina State takes this popular ornamental species
into latitudes comparable to those in central Florida. Jenkins (1999) summarized the literature on frost-tolerance and cold sensitivity among
Bromeliaceae, and concluded that neither altitude nor latitude in home
ranges consistently predict plant responses in culture.
Brazil' s `campos de altitude' (high montane grasslands) subject indigenous Bromeliaceae to substantial freezes during winter inland from the
Atlantic coast far north of the southernmost penetration of the family.
Fernseea itatiaiae on Pico Itatiania (2787 m in São Paulo State) tolerates at
least 26 °C, but lacks the characteristic compact morphology of similarly
stress-tolerant members of Puya. Plants at substantially lower elevations
even farther north cool enough now and then to incur visible leaf burn
(Leme and Marigo 1993).
Occasional frosts damage the shoots of the large rosettes of Alcantarea
spp. that grow fully exposed to heat loss on rocks near Teresopolis at elevations somewhat below 1000 m (Leme, personal communication).
Comparable dynamics prevail at similar elevations hundreds of kilometers
farther north in Minas Gerais and Espirito Santo states. Largely Bolivian
Abromeitiella (5 Deuterocohnia) probably also tolerate potentially lethal
temperatures, and together with the taxa just mentioned and others like
them constitute a much larger collection of frost-tolerant bromeliad ¯ ora
than present in North America (Fig. 7.6). However, more is known about
the effects of low temperatures on Bromeliaceae of the southeastern United
States.
All of Florida' s native bromeliads experience at least occasional freezes,
and some of the outcomes are recorded. Hall' s (1958) brief account
describes how several Tillandsia species fared during an unusually cold spell
during 12 and 13 December 1957. Minimum temperatures that night
remained below zero for several hours across all but the southernmost tip
of the state. Mortality varied according to the region, circumstances at
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Ecology
Figure 7.5. Distributions of four Brazilian Vriesea species reveal why some South
American Bromeliaceae exhibit extraordinary cold-tolerance in cultivation. Certain
Tillandsia species and members of Bromelioideae (e.g., Fascicularia) and
Pitcairnioideae (e.g., Deuterocohnia) range even farther poleward as indicated on
the map of the continent.
speci® c sites, and the identity of the bromeliad. Again, geographic distributions often predicted outcomes. For example, Tillandsia usneoides and T.
setacea near Jacksonville survived unscathed and T. recurvata incurred only
minor damage fully exposed in nearby habitat.
Populations with more pronounced tropical affinities (e.g., T. utriculata,
T. fasciculata) often fared worse hundreds of kilometers south. However,
results elsewhere were more capricious, for instance the death of an entire
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Figure 7.6. Distribution of eight of Florida' s Bromeliaceae based on herbarium
vouchers. Note that Tillandsia bartramii alone exhibits a predominantly northern
occurrence in the state. Four of these species are restricted to the lowest three tiers
of counties.
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Ecology
colony of T. setacea near Sebring, which is some 300 km below
Jacksonville. Co-occurring species sometimes performed differently. Near
Palm Beach where temperatures remained below freezing for several hours,
T. flexuosa died to the last specimen, while a small population of T. polystachia, a natural hybrid (T.3smallii) with a comparable range in that state,
survived largely intact.
Delaney' s (1994) report from the Archbold Biological Station in
Florida' s central pinelands describes how in 1983 one of the worst freezes
on record killed almost all of the local bromeliads and orchids beyond scattered individuals located along permanent waterways. A similar event just
six years later nearly eliminated the survivors, but also provided an opportunity to observe recovery from what must be normal, although not necessarily as frequent, setbacks for sensitive ¯ ora in central Florida. Today, the
few remaining butter¯ y orchids (Encyclia tampensis) persist in refuges near
deep impoundments that provide supplemental humidity and heat. At the
same time, three formerly abundant bromeliads, Tillandsia setacea, T. simulata and T. variabilis, are rebuilding populations elsewhere in Highland
County. However, recent experience suggests an uncertain future if current
land use practice continues. Long-time residents blame forest clearing and
extensive arti® cial drainage for what appear to be increasingly severe
droughts and devastating winter kills.
Seed dispersal can restore a contracted range, or foster expansion into
new territory as conditions, including frost, permit. However, distinguishing an expanding from a shrinking population requires analysis. Occasional
colonies of Tillandsia fasciculata in southern Georgia, hundreds of kilometers north of their nearest counterparts in Florida, pose this question. Are
these outliers remnants of a formerly more contiguous population that
existed during the warmer mid-Holocene, or infrequent progeny wafted
northward by tropical storms? Allozymes might reveal evidence of parentage ± perhaps polymorphism suggesting broader genetic bases than one or
a few founders per site could provide. Breeding systems, ¯ oral advertisements and pollinators provide additional opportunities for critical analysis.
Aspects of climate other than frost probably also in¯ uence range boundaries, particularly for certain Tillandsioideae sensitive to high humidity.
Moisture and temperature acting together help shape the distribution of
one exceptionally mobile species. Edward McWilliams (personal communication) has gathered substantial evidence suggesting that the northern
and eastern range limits of Tillandsia recurvata in Texas have shifted over
the last several decades. According to experiments, rainfall during the
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coldest months, through effects on survivorship in marginal habitats, seems
to determine range most decisively. For example, chilling damaged moistened more than surface-dry plants during runs conducted in growth chambers.
Tillandsia recurvata is the subject of another experiment farther east in
even more humid territory on the campus of Louisiana State University at
Baton Rouge. First reported there in 1971, it now infests 36 woody endemic
and exotic species over about 40 ha of managed landscape (Holcomb 1995).
Migration has been slow, with descendants located at most about 1.2 km
from the site of the ® rst record, probably on or near the contaminated
nursery stock that accounted for the introduction. Humidity seems to be
slowing additional expansion at the moment, perhaps by inhibiting dispersal. Matted comas often persist on spent in¯ orescences, and many of the
seeds that do escape from capsules move no further than the trees that
support their maternal parents.
Gilmartin (1973) demonstrated how cool temperatures favor certain
Bromeliaceae by mitigating drought. More than 300 species occur in
Ecuador, many as epiphytes at proscribed elevations in the Andes.
Seventeen taxa distribute across both the eastern and western slopes, and
do so according to growing conditions that oblige different elevations on
the two exposures. Habitats receiving maximum precipitation occur
between 800 and 1200 m on the eastern and 1200 and 1600 m on the western
slopes of the Ecuadorian Andes. Most importantly, less than 5 cm of rain
falls per month for at least four successive months on the Paci® c side, while
no month is equally arid to the east. Consequently, trans-Andean species
(e.g., Tillandsia cernua, T. confinis, T. emergens) almost always occur at
lower elevations, often more than 1000 m lower, on the Amazonian than on
the Paci® c slopes where the accompanying cooler temperatures diminish
the evaporative power of dry-season air.
Distribution in forests
Host specificity
The typical epiphytic bromeliad anchors on a number of kinds of trees like
most arboreal ¯ ora. Even inanimate objects, including telephone wires,
accommodate certain Type Five Tillandsioideae (Fig. 1.3A). Several of the
smaller Catopsis species occasionally do the same, somehow maintaining
water-® lled shoots upright. Those few Bromeliaceae reported to utilize just
a single species of tree tend to occupy narrow geographic ranges, or if more
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Ecology
broadly distributed reside in low-diversity woodlands (e.g., Pinus/Quercus
forests in Central America and Mexico). Figure 1.3B illustrates one of the
exceptions, in this case Billbergia porteana rooted on the palm that provides
most of its substrates through parts of Bahia State, Brazil. Elsewhere, for
example in caatinga (Fig. 1.4B), the same plant roots on diverse, mostly
broad-leafed trees.
Valdivia (1977) recorded the distributions of 153 vascular epiphytes,
including 33 bromeliads, on 45 woody taxa in east central Mexico. No bromeliad rooted exclusively on a single kind of tree, nor did the crowns of
every support utilized by another local epiphyte also accommodate
members of this family. Hospitality varied, with one tree species harboring
up to 107 different epiphytes, including many bromeliads. Conversely,
Acacia cornigera, a myrmecophyte aggressively defended by its resident
populations of Pseudomyrmex sp. against other insects and encroaching
vines, supported no arboreal ¯ ora. Perhaps the ants remove seedlings here
much as certain Crematogaster species preen the Leptospermum specimens
that support their nests in Malaysia (Weir and Kiew 1986). A reversed relationship, in which the ants quartered in orchids and bromeliads defend
some Mexican phorophytes against leaf-harvesting ants and a folivorous
beetle, is described in the next chapter.
Garcia-Franco and Peters (1987) reported nonrandom use of available
trees by six Tillandsia species in four habitats along an altitudinal gradient
in Chiapas State, Mexico. Individuals aggregated on certain parts of the
crowns (trunks and large, medium and smallest branches) of acceptable
species, leaving the others largely unoccupied. Hietz and Hietz-Seifert
(1995a) used nearest-neighbor analysis in Vera Cruz State, Mexico to demonstrate clustering by several bromeliads whose seeds often succeed close
to parents. The same authors (1995b) noted that tree identity had `practically no in¯ uence' on which epiphytes (66 species of which 25 were bromeliads) grew in speci® c crowns among six sites arrayed between 720 and 2370
m. Fontoura (1995) questioned whether phylogenetic relationships among
co-occurring trees paralleled usage by an assemblage of Atlantic Forest
Bromeliaceae richer in Bromelioideae. She mapped every adult present
through the crowns of 122 specimens representing 46 species in 20 families.
Twenty, 10310 m plots that totaled 0.2 ha contained bromeliads belonging to ® ve genera. Only 17% of the surveyed supports (.2.5 cm diameter
at breast height) hosted one or more of these epiphytes, and occurrences
indeed paralleled family affiliations.
Myrtaceous ¯ ora supported the largest number of species; local
Bromeliaceae also overutilized Rubiaceae, Melastomataceae and
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Monimiaceae according to the relative availability of member trees large
enough to be included in the survey. Girth (age) usually failed to predict
epiphyte loads, contrary to the observations made by Yeaton and
Gladstone (1982) and Ibisch (1996) in Costa Rica and Bolivia respectively.
A more evenly apportioned array of trees would have increased the statistical rigor of Fontoura' s inquiry, but no special effort was required to identify the most pronounced associations between woody and epiphytic ¯ ora
anyway. For example, the lone Coussopoa microcarpa specimen (Moraceae)
included in the quadrats supported bromeliads belonging to all ® ve genera
represented at the site.
Undetermined characteristics of the censused bromeliads promoted
unevenness in another dimension. Local Billbergia species, and to a lesser
extent those belonging to Quesnelia, proved relatively `selective' , whereas
co-occurring tillandsias rooted too diffusely through the canopy to discern
patterns if they existed. Billbergia species grew almost exclusively on
Alchornea triplinervia. Surveyed Vriesea species ranged most widely among
anchorages, and because they shared so many trees with the other taxa also
contributed inordinately to the generally gregarious nature of the local bromeliad ¯ ora.
Fontoura' s study also demonstrated how phylogenetic constraints
affecting ecophysiology can in¯ uence how bromeliads partition shared
habitat. Nidularium populations consistently grew in deep shade on the
lower sections of tree trunks in the fashion characteristic of this genus
through its relatively con® ned range in southeastern Brazil. Billbergia also
preferred the understory, but pronounced heliophiles elsewhere (e.g., B.
porteana; Fig. 1.3B) occupy drier, better-illuminated sites. Vriesea and
Tillandsia species included in the survey mostly colonized the upper
canopy, but relatives tolerate shade equal to that experienced by Nidularium
through diverse habitats across tropical America. Brazilian Tillandsia and
Vriesea belong to much larger clades that probably incorporate substantially more ecological variety than is present in either Billbergia or
Nidularium.
Three species of Catopsis and four more populations representing
Tillandsia and Guzmania monostachia utilized a variety of trees irrespective
of several characteristics that affect crown opacity in hardwood/Taxodium
forest in south Florida (Bennett 1984, 1986a, 1987). Instead, the number of
stems representing each support, often Fraxinus caroliniana, most consistently predicted epiphyte abundance. Stem thickness had no discernible
effect on recruitment. Two additional phenomena came to light during
Bennett' s investigation. Members of acceptable tree species often bore no
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bromeliads, while those with colonists usually supported multiple individuals reminiscent of Fontoura' s conclusion about gregariousness in Brazil.
Second, apparent and realized niches were distinguished for the ® rst time
for bromeliads. Speci® cally, some of the subjects (e.g., Guzmania monostachia, Tillandsia fasciculata) owed their presence in the study plots to mass
effect, i.e., they grow but rarely reproduce there.
All three of these studies demonstrate that many bromeliads recruit
anchorages according to a variety of often subtle, but probably widely
shared, tree characteristics. Conversely, other Bromeliaceae, sometimes
species with similar habits, partition anchorages that seem equally accessible to the seeds of all potential users. For example, Aechmea bracteata
grows abundantly on several kinds of phorophytes in semievergreen forest
in the Sian Ka' an Reserve in the Yucatán (Olmsted and Dejean 1987; Fig.
8.1B). Tillandsia balbisiana, a wider-ranging species that roots on more
than a dozen tree and shrub species just in south Florida, occurred at even
higher frequency at the surveyed Mexican site, but only in the crowns of
Bucida spinosa, a locally common tree invariably free of Aechmea bracteata.
Closely related Tillandsia dasyliriifolia shared several types of supports
with Aechmea bracteata, and also densely infested local Bucida crowns.
Dejean and Olmsted (1997) looked more closely at Aechmea bracteata in
the inundated forests and adjacent woodlands of Sian Ka' an to determine
why it colonizes some kinds of trees but not others. First, only 10.3% of the
individuals representing just ® ve of the 13 species available to intercept
seeds supported one or more individuals of this epiphyte. Utilization was
even lower on hammocks and nearby semievergreen forests. Overall, only
27 (35%) of the woody species surveyed hosted A. bracteata, presumably
because they lack certain characteristics, perhaps the necessary architecture
and/or suitable bark.
Of the 145 genets of A. bracteata encountered in the three types of forest,
more than 70% rooted where a large branch forked or a sizable limb joined
the trunk. Most of the rest of the sample perched on nearly horizontal
branches or at the base of trunks. Dejean and Olmsted concluded that
Bucida spinosa is well suited by its smooth, thin twigs to intercept comose
seeds (Tillandsioideae), but not those produced by baccate Aechmea bracteata (Fig. 3.6H,J). However, failure to encounter even one specimen on
103 trees suggests additional, more decisive deterrents.
Bromeliads and co-occurring epiphytes sometimes partition common
habitats, as four species of Tillandsia, including T. balbisiana and T. dasyliriifolia, and Aechmea bracteata plus some Orchidaceae demonstrated at a
second study site near Cancun, Mexico (Zimmerman and Olmsted 1992).
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In all, 10 species of orchids, along with the bromeliads, exhibited the usual
interchangeable use of the local woody ¯ ora by utilizing 15 of the 19 kinds
of potential supports. Although these 15 tree species tended to be either
poor or superior substrates for members of both families, the bromeliads
(except Aechmea bracteata) mostly rooted on axes less than 5 cm in diameter. Conversely, the orchids congregated exclusively on stouter stock.
Hietz (1997) encountered the same pattern involving several species each of
Catopsis and Tillandsia vs. several orchid species in a more humid Mexican
montane forest. Still another report (Rudolph et al. 1998) documented that
Tillandsia complanata occupied branches of all ages and the orchid
Epidendrum marsupiale only twigs 3 cm thick or less provided by the same
phorophytes in an Ecuadorian rainforest.
Decisive factors: bark quality and the nature of the relationship
Tests have helped demonstrate how epiphytic Bromeliaceae fail to use every
substrate within dispersal range. Benzing (1978b) glued the seeds of
Tillandsia paucifolia to a variety of trees that support or exclude this species
in south Florida (Fig. 6.2D). Germination was also tested in the greenhouse using sections of branches cut from four of the same phorophytes
(Table 6.12). Results in both instances paralleled those determined for the
same bromeliad in situ. Physical characteristics of the barks, particularly
stability and wettability, appeared to be most in¯ uential.
Contrary to ® ndings on the co-occurring orchid Encyclia tampensis (Frei
and Dodson 1972), phytotoxicity (allelopathy) had no measurable effects
on host suitability for Tillandsia paucifolia. Seeds germinated on all four
kinds of tested trees if adequate misting was provided in the greenhouse.
Exceptionally smooth bark that readily sheds seeds and precipitation probably explains why Ficus aurea remains almost epiphyte-free (axenous) in
south Florida. Figures 6.2D and 7.7F illustrate why certain physical attributes of the barks of Bursera simaruba and Taxodium distichum help
differentiate the ® rst species as an infrequent phorophyte and the second
tree as one of the leading substrates for Bromeliaceae in this state.
Few of the many factors and circumstances that affect epiphyte/tree pairings probably apply broadly enough to warrant generalizations. Parasitism
and the need for a fungus to germinate may explain the speci® city reported
for the exceptional mistletoe and orchid respectively (Benzing 1990).
Conversely, the much reduced, primarily mechanical root systems that preclude comparably intimate interactions between tree and epiphyte more
likely grant the relatively shoot-dependent bromeliads unusual latitude.
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Ecology
Figure 7.7. Bromeliads and substrates. (A) Tillandsia tenuifolia as an epiphyte in Rio
de Janeiro State, Brazil. (B) Tillandsia tenuifolia on rock about 10 m from the plant
shown in A. (C) Quercus virginiana in poor condition densely colonized by
Tillandsia usneoides in central Florida. (F) Dwarfed Quercus virginiana supporting
abundant Tillandsia recurvata in coastal strand habitat about 10 km north of
Naples, south Florida. (E) Robust Quercus virginiana almost free of epiphytic
Bromeliaceae in central Florida. (F) Exfoliating bark of Bursera simaruba with a
single young Tillandsia recurvata plant attached.
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Hietz and Hietz-Seifert (1995b) cited this possibility to explain why bromeliads exceed local orchids in the proportional use of Pinus in certain habitats in Vera Cruz State, Mexico. But whatever the underlying mechanisms,
the hospitality of a speci® c substrate for a designated epiphyte is best
viewed as conditional rather than the all-or-nothing phenomenon so often
implied in the literature.
Even the heavily infested phorophyte probably fails to support colonists
on every surface exposed to dispersing seeds. Moreover, epiphyte loads shift
among phorophytes of the same identity depending on location as if hospitality depends on site-speci® c variables, particularly humidity and light.
Age-related factors also in¯ uence the utility of bark, as does the size of the
seed supply. Rhizophora mangle in Florida supports no canopy ¯ ora where
other kinds of trees do. Yet the same or related bromeliads thrive in its
crowns elsewhere, for example at the other side of the Gulf of Mexico along
the Yucatán peninsula (e.g., Tillandsia brachycaulos, T. streptophylla; Fig.
1.2H).
Occupied vs. adjacent, barren microsites on the same phorophytes
warrant closer scrutiny to determine whether Rhizophora and some other
trees only sporadically host epiphytes because local seed rains seldom
reveal the few potential anchorages that exist in what are largely uninhabitable crowns. Conceivably, only the areas represented by older or appropriately oriented bark, water courses or colonies of lichens or bryophytes
provide acceptable seed beds. Bennett (1986a, 1987) reported that several
Bromeliaceae concentrated on bark embellished with mosses in the Florida
swamp mentioned above. Layers of humus and the nonvascular ¯ ora
responsible for its production also seem to sustain the seedlings of several
Bromelioideae in southeastern Brazil (Fig. 6.5A). Ordering among species
in the same successional sequence may re¯ ect different requirements for
unaltered vs. conditioned bark as described below. Similar dynamics may
apply to certain saxicoles (Figs. 6.5F, 9.12).
Once again, Tillandsia paucifolia helps explain epiphyte distribution, in
this instance why a Type Five bromeliad occupies so little of the substrate
present in the forests it inhabits in southern Florida. Seedlings resulting
from the germination tests not only survived lengthy drought during the
greenhouse runs just described, they actually required it. Within weeks
more frequently irrigated subjects died, apparently from suffocation or
overgrowth by microbes. Mist applied for half an hour once every 1± 2 days
promoted the highest rates of germination and subsequent growth (Table
6.12), indicating that the regenerative niche for this species is quite
arid. Another similarly drought-tolerant relative exhibited an even more
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Ecology
narrowly moisture-de® ned distribution in certain Mexican habitats than T.
paucifolia does in Florida.
Tillandsia recurvata colonizes but one host in parts of Baja California,
Mexico, in this case Idras, and then only on western exposures in what is
generally low-growing scrub forest and desert (Barry 1953). Heavy nightly
fogs moving on-shore off the nearby Paci® c Ocean account for the nonrandom distributions of this trichome-dependent bromeliad. Little rain falls
to encourage germination on the other exposures, essentially none during
exceptionally dry years. Stature in addition to bark quality likely promote
® delity to this single support. Mature Idras extend well above the co-occurring shrubs, thus favoring the conversion of mist into a life-sustaining moisture supply. Surfaces especially well suited to intercept seeds and condense
aerosols may further enhance host quality, a possibility ripe for testing with
real and arti® cial substrates.
Aspects of seed dispersal and the stems in the paths of wind-born propagules may exceed the hospitality of bark as primary determinants of
where many Tillandsioideae occur. Speci® c crown shapes and certain contours of trunks, limbs and twigs probably favor or discourage seed impaction and retention (Table 6.6). Con® gurations that cause wind streams to
eddy or reduce the velocity of suspended seeds, or cause them to wobble or
spin, may account for the heavier utilizations of certain trees by members
of this subfamily compared with other potential targets located in the same
currents. `Snag effects' plausibly explain the disproportionate occurrence of
Tillandsia flexuosa on Bumelia celastrina on Big Pine Key in south Florida
(H. Luther, personal communication).
Involvement of seed dispersers
Diverse fauna also in¯ uence where epiphytic Bromelioideae grow, but more
is known about how certain of the other ¯ eshy-fruited plants disperse
(Chapter 6). Several strangling ® gs congregate in the crowns of speci® c
kinds of trees on Panamanian Barro Colorado island in part because abundant stem spines (e.g., Hura crepitans) or other surface features provide
secure anchorages for seeds carried there by frugivorous birds (Todzia
1986). Platypodium elegans crowns remain mostly uncolonized despite
apparently hospitable bark, at least in part because its wind-dispersed seeds
attract no birds or bats seeking variety following earlier meals of ripe ® gs.
None of the local berry-producing bromeliads were mentioned. Bats that
roost by day and pass seeds among the dead leaves suspended below the
crowns of palms may account for the narrow occurrence of Billbergia porteana illustrated in Fig. 1.3B.
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Nest-garden ¯ ora, including the bromeliads (Madison 1979; Davidson
1988), present an even more complicated pattern to unravel. Here, ants
choose the phorophyte, and by also creating the rooting medium simultaneously reduce their own and the epiphyte' s dependence on the tree.
Complex animal needs affect the choice of phorophyte; Davidson and
Epstein (1989) report preferences for Peruvian trees with extra¯ oral nectaries (e.g., Inga), suitability for Homoptera (e.g., Calyptranthes), spiny surfaces that prevent the ascent of predatory ants (e.g., Tococa), or aromatic
oils. The same supports growing in deep shade or weakened by disease
remain largely nest-free, presumably because insufficient resources exist in
their crowns to satisfy the high caloric and additional extraordinary
demands of gardening (carton-producing) ants.
Ants regularly cultivate several Aechmea, Araeococcus, Neoregelia and
Streptocalyx (now Aechmea) species along with members of about 10 additional families in certain lowland forests (Fig. 8.1C). Several nonbromeliads constitute the most frequent nest-users at Cocha Cashu, Peru, where
more than three-quarters of all the surveyed cartons supported one or
more of these plant species. Restriction to ant-provided substrates often
exceeded 95% of the hundreds of sampled gardens. A less common
Neoregelia sp. and Streptocalyx longifolius rooted in 1.8 and 3.2% respectively of more than 800 examined nests.
An impressive array of fragrances and diverse food rewards promote the
dispersal of different ant-garden ¯ ora. Seeds of 9 of the 10 taxa tested,
including the two bromeliads, contained volatile methyl-6-methylsalicylate
(6-MMS). Aechmea longifolius, along with seven other species, further
encouraged ant carriage with benzothiazole (Davidson and Epstein 1989;
Seidel et al. 1990). Arti® cial seeds impregnated with 6-MMS attracted considerable attention from nest-building Camponotus femoratus, but elicited
little interest from nongardening congeners in the same habitats. Ule (1906)
and Madison (1979) proposed pupal mimicry as a possible incentive for
myrmecochory among a guild of Amazonian nest-garden ¯ ora, including
Aechmea mertensii, that share similarly suggestive seed sizes and shapes.
Nest size, exposure to sunlight, characteristics of the local soils, and ant
identity all in¯ uence garden ¯ oristics, complexity and vigor in western
Amazonia (Davidson 1988). Anthurium gracile occurred above statistical
expectation on small nests, whereas Codonanthe uleana uniformly occupied
cartons regardless of size. Every one of the relatively common ant-nest
garden species except Neoregelia sp. more often co-occurred with other
guild members than grew alone. Lower densities of plants on deteriorating
substrates, and their absence on all but ant-provided media, indicated
near obligacy for many of the participating plants. Phytotelm bromeliads,
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Ecology
probably because they impound moist, nutrient-rich debris in leaf axils,
respond least adversely to the carton erosion that invariably follows abandonment by the ants. Additionally, nests occupied exclusively by bromeliads compared with those hosting diverse ¯ ora more often occurred on trees
rooted in relatively impoverished soil.
Ant identity and behavior distinguished these systems even further. The
simplest gardens were usually tended by taxa (e.g., Azteca, Hypoclinea)
with solitary rather than multiple queens. Davidson' s suggestion that trees
on low-quality substrates lack capacity to produce the substantial quantities of food that polygynous ants need to sustain their more elaborate
nests and gardens warrants testing. Quite possibly, the bromeliad-centered
arrangements she noted may not constitute gardens in the described sense
at all, but simply represent carton embellishments constructed to enlarge
the plant-provided chamber a foundress chose to establish her colony.
Bromeliaceae and other arboreal ¯ ora can suppress phorophyte vigor
and probably also shorten the lives of trees through mechanisms discussed
below, but do they ever reduce ® tness enough to promote the evolution of
axeny? Some of the plant characteristics that determine whether a tree is
also a phorophyte must be heritable, hence amenable to natural selection.
However, axeny sometimes accompanies other, unrelated conditions.
Pioneers (e.g., Cecropia) typically host few, if any, bromeliads or other epiphytes, most likely because they maintain smooth barks and grow too fast.
Heavy loads of epiphytes require decades to develop even in everwet forests.
However, longer-lived, potentially more vulnerable forest dominants also
support little or no canopy ¯ ora, and these are the trees that could shed epiphytes to advantage.
Role of light and nutrients
Arboreal Bromeliaceae obtain nutrients from diverse media, some richer and
more continuously available (e.g., decaying litter) than others (e.g., precipitation; Fig. 5.1). Evidence from several Tillandsia species suggests that the
identity and condition of the phorophyte can be important for the bromeliad, and perhaps especially so for the type unassisted by impoundments or
access to earth soil. Certain trees leak ions or more readily intercept nutrientcharged aerosols than others (Tukey 1970). Epiphyte welfare is further sitedependent to the extent that the chemistry of washes changes while coursing
through the canopy. Concentrations of some dissolved plant nutrients tend
to fall (e.g., N), while the abundances of others (e.g., K) rise. Additionally,
well-provisioned compared with de® cient organs often yield richer leachates.
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Spanish moss ranges widely through the more humid, relatively frost-free
parts of the southeastern United States. Another set of constraints in¯ uences its distribution locally. Schlesinger and Marks (1977) cited nutrient
supply as one of the more decisive reasons why only some of the many
accessible trees become heavily used. Assays indicated that certain dense
colonies of this exceptionally proli® c bromeliad on Florida cypress bene® t
from relatively fertile washes compared with less vigorous colonies located
in the crowns of nearby Pinus. They also noted that Tillandsia usneoides
overoccurs in certain kinds of mixed hardwood communities in southern
Georgia and Florida.
Principal components analyses of the concentrations of nine elements in
foliage obtained from 24 locations grouped all but one collection by origin
from one of the three sampled types of forest. Certain soil-born elements
(e.g., P) in¯ uenced the ordinations more than others (e.g., Mg, Na) that primarily enter the canopy from the atmosphere. Performances in growth
chambers demonstrated that supplemental P enhanced plant vigor, while
additional Mg did not. Loose bark was assigned minor responsibility for
the relatively poor development of T. usneoides on Pinus. Adults showed no
effects in tests for allelopathy, although seedlings might have responded
differently to the same prepared leachates.
Contrary to Spanish moss, less shade-tolerant T. paucifolia reaches peak
densities in Florida on trees that produce unusually dilute canopy washes.
Unmatched abundances of this epiphyte infest the crowns of scrub cypress
dwarfed in part because the underlying soils are so thin and sandy (Figs.
1.4H, 7.8, 7.9). Media that deny trees adequate supplies of required ions in
turn probably explain why the T. paucifolia anchored there remain so small,
yet occur in such high numbers. Better-nourished, and consequently more
densely foliated, trees rooted in deeper media in Florida produce more ionrich bark and stem ¯ ow, but sustain many fewer, albeit individually larger
and better-provisioned, bromeliads (Benzing and Renfrow 1971a; Benzing
and Davidson 1979; Figs. 7.8, 7.9; Table 5.1).
Scarce supplies of N, P and K depress the vigor of T. paucifolia on
dwarfed cypress, whereas plants accumulate enough Mg and a number of
the additional essential elements to avoid similar de® ciencies at all of the
seven sites surveyed (Figs. 7.8, 7.9). Nevertheless, shortages of key ions,
although growth-retarding at the depressed levels provided by dwarfed
cypress, constrain this bromeliad less as a reproducing population than the
denser shade cast by the same host located on higher-quality soils.
Presumably these smaller bromeliads collectively produce more seeds than
the colonies of the same epiphyte in denser forests, even though the more
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Ecology
Figure 7.8. Relationship between P concentration (% dry weight) in mature (fullsized) ramets of Tillandsia paucifolia in south Florida growing on diverse kinds of
trees (r50.63, P .0.001; after Benzing and Renfrow 1971a).
Figure 7.9. Relationship between Mg concentration (% dry weight) in mature (fullsized) ramets of Tillandsia paucifolia in south Florida growing on diverse kinds of
trees (r50.13; after Benzing and Renfrow 1971a).
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scattered plants at the latter sites individually produce larger numbers of
capsules.
Martin et al. (1985, 1986) con® rmed shade-tolerance for Spanish moss
growing in a North Carolina forest by examining plants in situ and in the
laboratory. However, several ® ndings remain puzzling. Samples grown at
7± 15% of full sunlight (100± 200 mmol m22 s21 photosynthetically active
radiation (PAR) at midday) differed little from fully irradiated (1500±
1600 mmol m22 s21) controls in some of the features that usually indicate
adaptation to low light in land plants. Members of the former group contained more chlorophyll in foliage by weight, but chlorophyll a/b ratios
remained undifferentiated. High photosynthetic photon ¯ ux density
(PPFD) promoted starch accumulation but had little effect on chloroplast
structure, internode length, leaf size, stomatal density, or the morphology
of the trichome shields or guard cells. Nocturnal acidi® cation, a reasonable
index of daily photosynthesis for a CAM plant, measured about 60% of
that recorded for fully irradiated greenhouse subjects.
In the ® nal analysis Martin et al. (1986) concluded that Spanish moss
acclimates across diverse exposures without substantial morphological or
physiological adjustment. Fully conditioned by growth in the forest understory, a full day of about 10 mol m22 PAR saturates photosynthetic capacity (Amax). Finally, fertility appears to compare more closely with exposure
as a determinant of site quality for T. usneoides than for more heliophilic
T. paucifolia.
Vertical stratification
Schimper (1884, 1888, 1898) speculated that uneven responses to light and
moisture supply explain why Neotropical epiphytes stratify in dense forests.
More recent reports cite this pattern for Bromeliaceae, and a substantial literature deals with underlying mechanisms (Chapter 4). Bennett (1987)
determined that Catopsis berteroniana, C. floribunda, C. nutans and
Guzmania monostachia occur at different heights above ground in swamp
forest in southern Florida (Fig. 7.10). Catopsis berteroniana regularly experienced the fullest exposures, while Guzmania monostachia seems to require
more light through much of the rest of its extensive range in middle and
northern South America. The two other Catopsis species also tolerate substantial shade at this study site.
All four of Bennett' s subjects possess broad-leafed, phytotelm shoots,
suggesting that distinct physiology and other qualities of foliage account
for their capacity to partition shared habitats. Extraordinary costs related
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Ecology
Figure 7.10. Vertical distribution of four bromeliads in a swamp forest in south
Florida showing the range, standard error and mean elevation for each species (after
Bennett 1987).
to the heavily wax-covered, re¯ ective shoot and additional aspects of carnivory may oblige heliophily in Catopsis berteroniana (Fig. 5.3A).
Conversely, deeper green leaves accord with the darker microsites occupied
by its two relatives. Catopsis nutans alone displays a monolayered canopy
that probably further enhances light capture in low-energy environments
(Fig. 4.28). The atypical shade-tolerance of Guzmania monostachia in
southern Florida may be a legacy of those sporadic freezes mentioned
earlier if they favored genotypes able to avoid frost injury by growing in the
heat-trapping forest understory.
Pittendrigh (1948) surveyed the Bromeliaceae of Trinidad to determine
how the availability of moisture and light permit its members to partition
everwet forests of the northern mountains and range across the island' s ® ve
progressively drier life zones farther south (Figs. 4.15, 7.11). He found that
species segregate through three strata in communities dense enough to
feature steep gradients of humidity and PPFD (Fig. 7.11). Pittendrigh' s socalled `exposure' bromeliads occupied the uppermost perches at these
humid locations; some of the same species also grew through the entire canopies of certain more sparsely foliated seasonal woodlands. Considerable
succulence and dense indumenta or large impoundments combined with
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Figure 7.11. Schematic diagram illustrating the vertical strati® cation of
Bromeliaceae in wet montane forest in northern Trinidad according to Pittendrigh
(1948). Three ecophysiological types are recognized based on differences in shade
and moisture-tolerance and related shoot architecture.
sparser covers of absorbing trichomes characterized these most heliophilic
taxa (Figs. 2.4, 2.8).
Pittendrigh' s `sun' group, most of which feature broader, relatively
shallow phytotelm shoots, inhabit intermediate heights in dense humid
forest, and elsewhere tend to experience the same moderate PPFD. His
`shade-tolerant' populations congregate even lower in humid forest. They
also exceed all other Trinidad Bromeliaceae for thin foliage and sensitivity
to drought in part because shallow phytotelma more effectively impound
litter than moisture (Fig. 2.4A± D). No effort was made to determine
whether any of these epiphytes utilized speci® c kinds of trees more often
than others.
Pittendrigh' s survey inspired investigations designed to detect aspects of
carbon and water balance that underlie his three light-related categories
(e.g., Benzing and Renfrow 1971b; Griffiths and Smith 1983; Smith et al.
1985, 1986; Griffiths et al. 1986; Lüttge et al. 1986a). A guiding question
concerned why members of Group Three range more widely through dense
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Ecology
humid forest than upper or middle canopy specialists. Pittendrigh' s claim
that shade-tolerant Bromeliaceae would occur in full sun if less sensitive to
drought re¯ ected his conviction that these species, like their extinct terrestrial antecedents, are fundamentally heliophilic. Subsequent data would
con® rm that the shade-tolerant bromeliads require abundant moisture, but
contrary to his views about ecophysiology unchanged from earlier times
spent in exposed habitats on the ground, extant forms readily photosaturate and achieve high quantum yields in shade-light (Martin 1994; Fig. 4.7).
Shade-tolerant Tillandsioideae (all of Pittendrigh' s designates in
Trinidad belong to this subfamily) can perform like sciophytes and acclimate to higher PPFD, but they never escape the limited capacity to conserve moisture imposed by mesomorphic foliage equipped for C3
photosynthesis. Pittendrigh noted that `shade-tolerant' types ¯ ourish in full
sun if a nearby stream or comparable source of humidity lowers evaporative demand in adjacent air. Anthocyanins synthesized to screen the mesophyll of highly exposed specimens constitute the most conspicuous
adjustment to high exposure under these conditions. Guzmania monostachia responds to potentially injurious PPFD by adjusting leaf structure,
chemistry and physiology (Maxwell et al. 1992, 1994, 1995; Figs. 4.24± 4.27;
Table 4.6).
Photosynthetic pathways tend to predict ecophysiological performances
and related growing conditions, but perhaps less reliably among
Bromeliaceae than in some other ¯ ora (Chapter 4). Consistent with patterns elsewhere, Pitcairnioideae and Tillandsioideae native to the lower
canopy and forest understory typically exhibit C3 photosynthesis (Table
4.1). CAM types provide a less consistent picture. Most Bromelioideae
native to dark, humid forests ® x CO2 primarily at night, although not necessarily in the manner displayed by similarly equipped taxa native to more
exposed and drier habitats or to gain the same bene® ts.
Aechmea aripensis, A. downsiana and A. fendleri possess large phytotelmata and inhabit some of Trinidad' s wettest northern montane habitats, yet
they employ CAM (Griffiths and Smith 1983). Terrestrial and CAMequipped Bromelia humilis, and several Ananas species, including a number
of feral selections of cultivated A. comosus (Medina et al. 1986), grow more
vigorously in partial than in full exposure. Soil-rooted Aechmea magdalenae spreads by ramets to form dense colonies (.1 large rosette m22) in
heavy shade (,5% full sunlight) in moist Panamanian forest (Brokaw 1983;
P® tsch and Smith 1988), further obscuring the advantages of CAM for
some Bromeliaceae.
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Perhaps some obscure plant advantage granted by CAM explains what
only appears to be an ecological paradox in Trinidad' s Bromeliaceae.
Possibly only those rare, but decisively, dry years account for the existence
of this water-conserving mechanism in populations native to what are generally wet zones. Alternatively, considerable latitude may characterize processes as fundamental to niche de® nition even as carbon and water balance
in the climatically permissive humid tropical forest. Suboptimal strategies
characterize many other plants in the sense that many populations operate
closer to marginal than to ideal growing conditions.
Relegations of populations of bromeliads to suboptimal habitats may be
common. Peculiarities of dispersal, a local pathogen, some competitor, or
in the case of certain CAM bromeliads in northern Trinidad, a trait unrelated to energy, water or nitrogen relations, may account for what appear
to be poorly matched plants and growing conditions. Introduced ¯ ora that
exploit alien more broadly than native habitats (e.g., Schinus terebinthifolius in south Florida) provide impressive examples in other families. So far,
no bromeliad, despite widespread use in managed landscapes, has escaped
to naturalize far beyond its home range to demonstrate comparable behavior (exceptions may include Billbergia pyramidalis, a Dyckia species, and
Portea petropolitana in parts of Florida, as well as Fascicularia pitcairniifolia on the Isles of Scilly and in parts of western France (Nelson and Zizka
1997); Chapter 15).
Bromeliads native to Brazil' s Atlantic Forest also segregate into discrete
exposure classes, although perhaps not as precisely as those Pittendrigh
noted in Trinidad. Veloso (1952) and Veloso and Klein (1957) determined
that of 54 species observed at diverse sites, 20 are heliophilic, 13 others
moderately tolerant of shade and dryness, and the remaining 21 taxa
mostly root on the bases of trees in dense shade. Reitz (1959) recognized
four strata in the tallest forests in Santa Catarina State, each populated by
generally nonoverlapping assemblages of species.
Tank-producing Nidularium innocentii var. paxianum and N. procerum
var. procerum dominated the lowest part of the canopy and sometimes
densely enough to appreciably humidify the understory. Vriesea incurvata,
V. ensiformis, V. carinata and additional, somewhat more drought-tolerant
species anchored on tree trunks from 2 to about 8 m off the ground. Species
Reitz labeled `indifferent' , i.e., moderately shade and drought-tolerant
types, constitute the third and most numerous and taxonomically varied
(e.g., Aechmea nudicaulis, Canistrum lindenii, Vriesea jonghei, Wittrockia
superba) of his four groups. Bromeliads restricted to the upper canopy (e.g.,
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Ecology
Vriesea rodigasiana, Tillandsia spp.) require the highest exposures and
endure greater aridity than the others. Curiously, several of these heliophiles (e.g., Vriesea rodigasiana) possess lightly trichomed, water-impounding foliage about as thin and broad as that of relatives relegated to deep
shade. Presumably, distinct water relations and capacities to harmlessly dissipate excess irradiance underlie the disparate ecology.
Epiphytic Bromeliaceae, particularly dry-growing Tillandsioideae, often
show little indication that they partition shared canopies. For example,
Tillandsia caerulea, T. didisticha, T. latifolia var. divaricata, T. floribunda, T.
straminea and Vriesea espinosae seem to anchor interchangeably through
the crowns of primarily legume hosts in thorn forest in Loja Province,
Ecuador (H. Luther, personal communication). Tillandsia paucifolia, T.
balbisiana and T. recurvata behave similarly on dwarfed cypress (Fig. 1.4H)
in southern Florida, while T. fasciculata, owing to its greater mass, never
reaches maturity unless supported by an axis stout enough to bear considerable weight.
Bromeliaceae differentiated by photosynthetic pathway often occur in
overlapping arrays on shared trees in wetter forests than those two just
mentioned, demonstrating once again (Chapter 4) the failure of these
multidimensional syndromes to narrowly proscribe growing conditions.
Zotz (1997a) examined the distributions of Guzmania monostachia,
Tillandsia fasciculata and Werauhia sanguinolenta on Annona glabra in
Panama. All three species possess phytotelm shoots (but utilize different
photosynthetic pathways: C3± CAM, CAM, C3 respectively), which could
explain why they tended to share space except that Werauhia sanguinolenta
more than the other two species concentrated in the upper, presumably
driest, most exposed parts of sampled crowns. Zotz also demonstrated that
substrates suitable for adults served as well for the more drought-vulnerable seedling stage. Then again, perhaps adjacency to Lake Gatun precludes
environmental gradients, which at drier sites might affect distributions
more decisively.
Light and humidity gradients partition resident bromeliads to different
degrees in dense forests. Failure to segregate as extensively in one region as
in another sometimes re¯ ects the absence of certain kinds of stock. For
example, seven bromeliads, six probably drought-vulnerable types
equipped with phytotelm shoots, and ant-house Tillandsia bulbosa concentrated around mid-level at three locations in wet Guayanan lowland forest
(Ter Steege and Cornelissen 1989). Deepest shade excluded the entire
family, much as Gentry and Dodson (1987) reported for pre-montane rainforest at Rio Palenque, Ecuador, where eight aroids, four dicots, eleven
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357
orchids and seven ferns accounted for all of the local, compact sciophytes.
Abundant secondary hemiepiphytes representing Araceae, Cyclanthaceae
and the ferns share this same darkest space.
Failure of all of the many bromeliads perched higher in the canopy to
also colonize the deepest portion of the same two forests in Guayana and
Ecuador seems odd considering the situation farther south (e.g., Veloso
1952; Reitz 1959). Figure 1.3D illustrates Cryptanthus bromelioides
growing on rocks and earth soil in mature Brazilian Atlantic rainforest.
Members of Lymania, Nidularium and Neoregelia, among additional
genera largely restricted to or endemic to southeastern Brazil, also demonstrate equivalent shade-tolerance. Were subfamily Bromelioideae to range
northward in greater force, the family might be far better represented
(ignoring Pitcairnia) in the understory north of the Equator.
Uneven occurrences of the major taxa making up Bromeliaceae in¯ uence the family' s role and importance in communities in different parts of
tropical America to the extent that certain lineages possess propensities for
shade-tolerance in addition to other important attributes like epiphytism
(Table 1.3). Bromelioideae and Tillandsioideae contribute about equally to
the arboreal and lithophytic ¯ oras of the Atlantic forests of Brazil (e.g.,
Veloso and Klein 1957), while Tillandsioideae predominate farther west
and north.
Tillandsioideae, speci® cally Catopsis, Guzmania, Tillandsia and Vriesea,
accounted for 20 of the 22 epiphytes censused in lower montane rainforest
at Monteverde, Costa Rica (Ingram et al. 1996). Pitcairnia contributed the
two additional arboreal species. Guzmania and Pitcairnia reach exceptionally high diversities in the everwet montane forests of the Colombian
Chocó, the second genus almost entirely as terrestrials and hemiepiphytes.
Bias toward Tillandsioideae remains strong at humid locations through
Ecuador, Panama and into Mexico. Pitcairnioideae, particularly Puya,
along with Tillandsia, predominate at high Andean elevations.
Pitcairnioideae account for much of the substantial bromeliad ¯ ora of the
Guayanan Shield, mostly as terrestrials adapted to infertile, moist substrates.
Kelly (1985) demonstrated the exceptional ecoversatility of at least the
occasional bromeliad during his study of a 26± 28-m-tall Jamaican lower
montane rainforest. Nine orchids, ® ve bromeliads, three ferns and one
Anthurium constituted the compact (nonvining) vascular ¯ ora growing at
least 12 m above the ground. A similarly mixed assemblage of seven
orchids, two bromeliads, three ferns, two dicots and the same Anthurium
occupied the mid-canopy (4± 12 m). Below 4 m resided three ferns and
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Ecology
phytotelm Hohenbergia pendulaflora, which anchored as well on all but the
highest branches. This large-bodied bromeliad also colonized 79.2% of the
surveyed trees, more than any of the local compact epiphytes. Numerous
hemiepiphytes grew through the same canopy, but as climbers equipped
with heterophyllous foliage and adventitious roots these plants may be
especially well suited to grow across environmental boundaries that de® ne
accessible space for the more compact arboreal ¯ ora. Vining Pitcairnia may
share this extraordinary opportunity for functional specialization along a
single genet (Fig. 2.2C).
Additional patterns
Exposure, moisture and nutrient supplies, the behaviors of dispersers,
and aspects of substrates in¯ uence local distributions of epiphytic
Bromeliaceae. Plant-based agencies operate as well. Tillandsia paucifolia
demonstrated that propensity to establish near the sources of seeds contributes to its gregariousness in cypress forests in southern Florida (Benzing
1978b, 1981a; Table 6.13). Kernan and Fowler (1995) determined that disturbance and growth requirements combine to order in space members of
a guild of arboreal, relatively shade-tolerant Araceae and Bromeliaceae
(Aechmea pubescens, Tillandsia anceps, Vriesea heliconioides, Vriesea sp.) in
humid (5000 mm year21), primary, pre-montane forest in the Corcovado
Basin on the Osa peninsula of southwestern Costa Rica.
Tree falls and lesser disturbances at Kernan and Fowler' s study site force
a rotation involving all seven epiphytes, but participation is uneven. Each
of ® ve successional stages was mapped to determine its representation
within the forest mosaic. Mature forest (recovery stage four) was further
divided into forest interior and edge, the latter being the 5 m zone bordering any of the three recovery stages. Measurements obtained with a
forester' s cruising prism indicated the amount of bark surface available to
epiphytes between 0 and 15 m off the ground within each of the ® ve types
of space (Kernan 1994). Observed utilizations (numbers of plants present)
and those expected on the basis of available substrate provided the residuals required to determine the relative dependencies of the seven epiphytes
on speci® c stages of the forest cycle.
Few adult bromeliads inhabited early or mid-recovery forest. More individuals were present by the late-recovery stage, and numbers peaked in fully
mature habitat. However, guild members on average were 1.333 more
abundant than expected in the early stage, 1.283 more common in midrecovery, 4.043 that number in the late-recovery stage and only 0.483 as
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frequent as predicted by available substrates in mature forest. Of the individuals anchored in mature forest, 1.353 the expected number occurred in
edge space, while just 0.513 as many plants occupied interior regions as the
bark present there could theoretically support.
Combinations of species differed across the successional mosaic, suggesting that guild members vary in their responses to growing conditions
that change during the forest cycle. Gaps favored the bromeliads compared
with the aroids, i.e., all the bromeliads exhibited relatively large positive
residuals in mature forest. All three aroids exhibited the same, although
somewhat muted, pattern. Generally, low densities (total epiphytes)
through the forest indicated little likelihood of substantial interspeci® c
competition, and accordingly, no need for ecological differentiation to
allow the seven populations to co-occur.
Nonuniform capacities to colonize young trees in gaps and persist
through canopy closure could explain the uneven occurrences of the three
aroids and four bromeliads among age-graded habitats. Distinct responses
(Vriesea heliconioides least and Philodendron saggitifolia most shade-tolerant) to closed canopy revealed light and possibly drought as key determinants of guild structure. Additional factors attending forest regeneration,
including shifts in the relative availabilities of speci® c kinds of trees and
bark exposures, might also in¯ uence outcomes at Corcovado.
Interpretation was further complicated by the need to rely on adults to
infer the behaviors of what in effect are unidenti® able juveniles.
Conceivably, the regenerative niches of these epiphytes overlap more than
the adults suggest by their distributions. Differential growth and mortality
and varied capacities to establish on young vs. older substrates could
account for the observed ordering of guild members through the forest
mosaic. On the other hand, recall that Zotz' s (1997a) survey in semievergreen forest in Panama indicated that the same kinds of microsites served
the seedlings and adults of three bromeliads about equally well.
Kernan and Fowler (1995) looked more closely at the substrates these
seven epiphytes utilize at Corcovado National Park for signs of differential
use irrespective of tree identity. Several characteristics of the epiphytes, speci® cally seed and root morphology, could also affect plant distributions.
Vriesea heliconioides, for example, produces relatively short organs and
accordingly, clings less securely to the same thick axes that the other guild
members surround with roots. Height above ground, inclination relative to
gravity, surface texture, and many additional characteristics further
differentiated the local barks as potential seed beds. Reliance on frugivores
to disperse essentially unappendaged seeds (Aechmea pubescens) vs. wind
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Ecology
currents (Tillandsia and Vriesea) probably also in¯ uences which of the
many local substrates best accommodate speci® c bromeliads.
Although the amount of bark surface arrayed between 0 and 15 m above
ground was relatively constant across all the sampled sites, the entire guild
except for Aechmea pubescens and Anthurium hacumense grew most abundantly at about 5 m elevation. Trunks and branches with diameters between
5 and 20 cm also occurred at about the same frequency through the understory, but all seven epiphytes tended to congregate on axes less than 10 cm
thick. Thinner (,5 cm) supports were most favored by Araceae, while the
bromeliads, particularly Vriesea heliconioides, rooted on relatively robust
substrates (5± 20 cm). Among the bromeliads, V. heliconioides rooted more
often than predicted on horizontal and Tillandsia anceps on vertical surfaces. Fewer than expected numbers of epiphytes anchored on axes inclined
between 50 and 90°. Bark texture sometimes unexpectedly biased occurrences (e.g., Vriesea heliconioides over-represented on smooth compared
with rougher surfaces).
Kernan and Fowler imputed mechanisms that foster coexistence and
persistence to explain their ® ndings. Coexistence supposedly requires
frequency-dependent negative-feedback regulation mediated by heterogeneous bark surfaces and corresponding capacities among guild members
to colonize speci® c types of surfaces. Disturbance, including lethal
drought during El Niño events in addition to the more continuous background of tree falls, provides the basis for a frequency-independent persistence mechanism (frequency-independent mortality) that prevents the
local extirpation of those guild members most vulnerable to competitive
exclusion. However, no such mechanism is likely to operate at the study site
until populations expand substantially beyond their current low abundances.
Additional investigators have sought evidence that co-occurring bromeliads interact to structure communities, and that co-occurring species
belong to ecologically de® ned groups (guilds). Hazen (1966) conducted a
computer-assisted analysis to determine if spacing along the branches of
trees supporting dense colonies of mostly Guzmania monostachia and
Tillandsia leiboldiana at a site in Costa Rica indicated competition. No
pattern was found. Catling et al. (1986) and Catling and Lefkovitch (1989)
used statistical techniques to circumscribe what they considered natural
assemblages containing bromeliads, orchids and ferns on cultivated Citrus
in Belize, as discussed below.
Pittendrigh' s (1948) discovery that Bromeliaceae of Trinidad' s northern
wet montane forests belong to three ecologically distinct groups inspired
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Figure 7.12. Hypothetical phorophyte illustrating the common pattern of epiphyte
occurrence through tree crowns in humid forest (after Johansson 1975). Epiphytes
are differentiated according to the nature of the substrates and other growing conditions they require (after Benzing 1990).
additional research. Several investigators applied his paradigm to other
members of the same family elsewhere (e.g., Veloso 1952), or they sought
parallels in other arboreal ¯ ora. For example, Johansson (1975) recognized
® ve life zones, each distinguished by its resident orchids, in West African
trees, three at different depths in the crown, plus one on the upper
and another on the lower trunk (Fig. 7.12). Species sometimes occupied
adjacent zones, but usually no more than two. Presumably, drought
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Ecology
challenges survival on the outermost twigs, whereas insufficient light probably limits epiphyte success deeper in the canopy. Gentry and Dodson
(1987) and Catling et al. (1986) noted similar apportionments of bromeliads, ferns and orchids (mid-canopy most species-rich) in Ecuador and
Central America respectively. Greater niche overlap recorded for Tillandsia
imperialis and additional nonbromeliads by Hietz and Hietz-Seifert (1995c)
probably re¯ ected wetter conditions in the Mexican cloud forests they surveyed.
Bromeliaceae in addition to Tillandsia recurvata in Baja California
(Barry 1953) sometimes occur asymmetrically around vertically oriented
stems. Yeaton and Gladstone (1982) noted no over-represented compass
orientations on sampled trees, contrary to Bennett' s (1984, 1986a) ® ndings
on three Catopsis species and Guzmania monostachia in south Florida
where eastern exposure for G. monostachia and northern sides of trunks for
Catopsis nutans hosted the fewest plants. Tillandsia pruinosa occurred
above expectation on the east sides of supports in a second survey (Bennett
1984), whereas T. flexuosa about as often faced east or west.
Although frost helps establish the northern extensions of much of
Florida' s ¯ ora, it seems less likely to account for the more ® nely resolved
distributions of resident epiphytes. Coldest winds generally blow from the
northwest, but the small-diametered axes (,2 cm) that supported many of
Bennett' s bromeliads offer little protection in any quadrant. Exposure to
precipitation, sun and the other agencies that affect water balance more
likely impose site-speci® c mortality, especially for seedlings, which in
Florida begin life at least eight months before the lowest temperatures and
driest months of the year. Distributions in tree crowns might also re¯ ect
movements of the wind currents that deliver comose seeds.
Roles in succession
Colonization and revegetation of new and denuded, established substrates
respectively tends to be orderly and predictable. Several reports indicate
that Bromeliaceae participate in succession in the forest canopy, and community structure sometimes suggests similar dynamics occur on the
ground. Particularly impressive are the bromeliad-rich restingas of Brazil
(Fig. 7.13C± E). Many of these systems resemble the dune sequences of the
Great Lakes of North America that prompted some of the initial insights
on the mechanisms responsible for plant succession. Claims concerning
arboreal Bromeliaceae come from side-by-side observations rather than
time-course analyses, in part because succession in tree crowns proceeds so
slowly. Similar change involving the lithophytes probably takes even longer.
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Roles in succession
363
Figure 7.13. Bromeliaceae in restinga. (A) Tillandsia stricta growing beneath a nurse
shrub suggesting its need to establish on bark prior to anchorage on soil. (B)
Unidenti® ed Hohenbergia sp. perched just above the high waterline in a seasonally
inundated swale in Bahia State, Brazil. (C) Aechmea nudicaulis in restinga in Rio de
Janeiro State, Brazil. Shaded compared with fuller-exposed ramets tend to be
greener and the foliage more spreading. (D) Shrub island with an understory and
apron of Neoregelia cruenta in Rio de Janeiro State, Brazil. (E) Neoregelia cruenta
around another restinga island.
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Ecology
Figure 7.14. Colonization of Alnus acuminata trees in Bolivia by bromeliads, ferns
and orchids relative to the thickness and presumed age of the supporting stems.
Note that some bromeliads and orchids established on the youngest exposures.
Delayed arrival by participating ferns (and Ericaceae and Piperaceae which are not
shown) indicated that many of the local epiphytes require conditioned substrates.
Whereas bromeliad diversity soon leveled off, additions of orchids continued until
more than twice the number of species comprised this contingent (after Ibisch
1996).
Ibisch (1996) reported that certain bromeliads (e.g., Tillandsia adpressa)
and orchids rapidly establish on 1± 2-year-old horizontal branches and
freshly exposed sites on the older axes of Alnus acuminata in some Bolivian
montane rainforests (Fig. 7.14). Growth rings indicated that the later-arriving epiphytes (e.g., ferns, Ericaceae) displace some of these pioneers. Axes
supported 6± 8-year-old ¯ owering bromeliads by year 10. After another
5± 10 years, large tank bromeliads and cushion-forming orchids dominated
what had become densely occupied surfaces. Mature communities prevail
after 20± 25 years. Ericaceae, ferns and Peperomia require site preparation
by nonvascular plants, bromeliads and orchids.
Freiberg (1996) compared the relative contributions of 77 local epiphytes, including ® ve Bromeliaceae, to arboreal ¯ ora supported by mature
specimens of three species of canopy-emergent trees in a Costa Rican moist
forest. Epiphyte cover on Hura crepitans, Cebia peltandra and Couratari
stellata was 51, 58 and 81% respectively. Values (18.0, 13.7, 18.6%) just for
Vriesea amazonica, which occupied more space than any of the other participating species, indicated that Bromeliaceae were dominant and persis-
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Roles in succession
365
tent. Precisely when this exceptionally proli® c tank-forming bromeliad
arrives in a maturing tree crown may in turn in¯ uence how extensively the
less substrate-neutral ¯ ora representing families like Rubiaceae and
Orchidaceae also become part of these suspended communities.
Bromeliads depend less on site conditioning than many other arboreal
plants, but pioneer status in canopies and on rocks requires con® rmation
of the type provided by Ibisch (1996). Competence probably varies with the
subject, the mesophytic forms and particularly members of Bromelioideae
(Fig. 6.5A,F) requiring more accommodating media than the totally trichome-dependent, xerophytic species, as noted above for Tillandsia paucifolia (Fig. 6.5E). Ant-dispersed Bromeliaceae utilize more complex
substrates, often obligately. As such, the nest-garden types represent a
subset of epiphytes and accordingly, deserve separate recognition, as do the
phytotelm forms that create habitat for ¯ ora and fauna, including many
more kinds of ants than create seed beds for the epiphytes.
Yeaton and Gladstone (1982) sought evidence that a mixed arboreal
¯ ora containing several bromeliads interacts while colonizing the crowns of
Crescentia alata in Guanacaste Province, Costa Rica. The trees in question
formed a small, unevenly aged plantation within 100 m of dry, deciduous
thorn forest inhabited by the same collection of epiphytes, including the
several unidenti® ed Tillandsia species. None of the bromeliads arrived ® rst
on young bark, contrary to the situation recorded in Bolivian montane
forest and perhaps also on remnant trees following forest clearing at a
Mexican site (Hietz-Seifert et al. 1996). Of the nine epiphytes present, up
to seven occupied a tree simultaneously, speci® cally the largest and presumably the oldest specimen at the study site. Orchids increased in relative
abundance as the supports grew larger except for Encyclia cordigera whose
dominance on young trees subsequently diminished. No resident consistently rooted at speci® c heights off the ground or in any other way distinguished itself by anchorage on Crescentia. The orchids tended to be their
own nearest neighbors and only Brassalvola nodosa associated with a
second species, Encyclia cordigera. Weberocereus glaber, a humiphic cactus,
alone required older trees, probably because its seedlings need a more thoroughly conditioned, moisture-retaining bark.
Although slower to appear on new substrates, the bromeliads equaled
the orchids as colonizers of unmodi® ed bark. Except for the single cactus,
seed mobility and plant fecundity probably in¯ uenced arrival time most.
Hundreds of thousands of microsperms ripen in a single orchid capsule,
assuring a far denser seed rain than possible for any of the bromeliads
(100± 300 seeds per capsule typical for Tillandsia) or the cactus. The heavier,
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Ecology
plumose Tillandsia seed and need to attract frugivores by Weberocereus
may further delay the appearance of the nonorchids. Much apparently hospitable bark that nonetheless remained largely free of attached plants, even
on older trees, further indicated little opportunity for interactions among
co-occurring epiphytes.
Certain epiphytic bromeliads co-occur with other arboreal ¯ ora regularly enough to indicate substantial ecological similarity. Catling and
Lefkovitch (1989) identi® ed four regular associations of epiphytes located
between 0.3 and 5 m above ground in a 2 ha plot of Guatemalan cloud
forest. Age (thickness) of the substrates predicted compositions that
ranged from two to ® ve species. Of the two types of groups, one early and
one later in developing, the former contained fewer ferns and orchids.
Participants in the more diverse associations that included two unidenti® ed
Tillandsia species were larger and engaged in more seasonal than continuous ¯ owering. Complete life histories might distinguish the identities of
these plants as pioneers or later arrivals, and reveal any rules that govern
how these groups assemble.
The ant-nest sequence
Ant-dispersed Bromeliaceae warrant separate mention, as do their relatives
that produce habitable cavities for other plants and animals. At least some
garden-tending ants cultivate plants selectively, planting the seeds of preferred species while removing the adventive seedlings of others. Plant competition further determines garden composition later. Davidson and
Epstein (1989) reported how a series of more light-demanding `nest parasites' replace pioneering Peperomia macrostachya at a site in Amazonian
Peru. A similar assemblage of slower-growing aroids, bromeliads and
woody epiphytes eventually eliminates more precocious and heliophilic
Codonanthe uleana in the same region. Fewer of these later arrivals offer
ant food, and some of them reduce nest quality for the ants by clogging
carton galleries with roots (e.g., Aechmea angustifolia in Ecuador; Fig.
8.1C).
Bromeliads as substrates for flora
Communities that resemble those assembled by ants on cartons develop in
association with certain phytotelm bromeliads (e.g., Aechmea in Ecuador).
A variety of aroids, ferns, gesneriads (e.g., Columnea) and peperomias, and
even an occasional Clusia or Ficus (Fig. 1.2D), sometimes nearly obscure
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Roles in succession
367
the hosting epiphyte. If succession or ants or any other seed dispersers help
nurture these communities, their involvements remain undocumented.
Hietz and Hietz-Seifert (1995a) made no mention of assisting fauna in their
report that epiphytic Tillandsia punctulata serves as a nurse plant for
Peperomia in Vera Cruz State, Mexico. Less diverse plants colonize the
shoots of bird' s-nest Anthurium and the many ferns that also impound
litter, but hold less moisture than phytotelm Bromeliaceae.
Nonbromeliads also serve as nuclei for ant-garden development, but
later arrivals, including a bromeliad, can end up sharing space or even eliminate the pioneer. Epidendrum immatophyllum provides the inducement
Azteca sp. needs to initiate nest-building at a site in Belize (Catling 1995).
Its massive, foundress-attracting root system dominated the smaller, presumably younger carton on Citrus. Nest size and garden diversity, including the appearance of eventually codominant Aechmea tillandsioides var.
kienastii, proceed apace. In all, one or more of 13 vascular taxa rooted in
282 of 288 scored cartons. However, this bromeliad, Coryanthes speciosum,
Codonanthe macrodenia and Polypodium polypodioides, in addition to
Epidendrum immatophyllum, occupied at least 10% of all the sampled
cartons, the bromeliad and orchid closer to 55%. Epidendrum immatophyllum most often occurred without companion ¯ ora. Despite its unmatched
frequency in nest gardens, of the ® ve participants this orchid most often
(5.5%) also grew elsewhere. Aechmea tillandsioides var. kienastii exceeded
statistical expectation in its use of local cartons, and contributed more to
total plant cover on larger nests secured to older, thicker limbs.
Certain terrestrial Bromeliaceae also provide co-occurring ¯ ora scarce
resources ± water in some cases and drier substrates in at least one other situation. Philodendron leal-acostae counters drought in Bahia State, Brazil
by extending its roots into the moist leaf axils of adjacent terrestrial
Bromeliaceae (Mayo and Barroso 1979). Contact occurred often enough to
prompt its discoverers to suggest that the relationship `could be essential'
to the aroid. Scarano et al. (1997) identi® ed several large phytotelm
Bromelioideae that act as nurse plants for three Clusiaceae that contribute
to the woody overstory in freshwater swamps of the Atlantic Forest of
southeastern Brazil. A shrubby Erythroxylon owes its dominance in some
Brazilian restingas to the accommodating shoots of terrestrial Neoregelia
cruenta. Several carnivorous Utricularia spend entire life cycles con® ned to
the aquatic microcosms provided by certain Bromeliaceae (Fig. 8.4B).
Phytotelm bromeliads promote biotic change by producing broadly
hospitable ecospace and providing other resources for additional life
forms, both animals and plants. Sometimes the same qualities responsible
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Ecology
for self-sufficiency and utility for other biota restrict distributions to robust
anchorages (e.g., massive species of Alcantarea and Tillandsia). Heavy
specimens that lose their grip on stouter supports may create the opportunity pioneer epiphytes require to recolonize surfaces formerly closed to
their propagules by the presence of established vegetation (Ibisch 1996).
Perhaps timing distinguishes plant succession on bark vs. soil most of all.
Phorophytes die and, prior to that, shed branches, twigs and bark (selfprune, exfoliate), causing substrates to cycle faster than is characteristic for
many terrestrial settings, especially rocky exposures. Disturbance of this
magnitude probably selects for traits that shorten the life cycle of the barkuser within the limits set by difficult growing conditions. Aridity, by impeding photosynthesis, simultaneously constrains opportunity for succession
and the evolution of abbreviated life histories; it may also limit plant capacity to saturate living space or achieve the more structured organization
exhibited by communities characteristic of more durable substrates. Bark
and twig specialists, especially the Type Five bromeliads, because they
require years to reach ¯ owering size, probably escape density-related mortality more often than their faster-growing relatives dependent on richer
resource bases.
Nevertheless, something other than drought limits the abundances of at
least some dry-growing Tillandsia species. For example, colonies of T. paucifolia exhibited similar demographics and dispersions on 50± 200-year-old
trees (Figs. 1.4H, 6.8). Much more of the space in these same crowns
appeared equally habitable yet remained unoccupied, suggesting little
opportunity for interference among co-occurring populations, much as
Kernan and Fowler (1995) discovered in wetter Costa Rican forest. If, in
fact, community status requires interaction among co-occurring ¯ ora, as
does plant succession, then assemblages comprised of bromeliads, like
wide-ranging and stress-tolerant T. paucifolia, may not qualify.
In summary, parallels and differences characterize succession as textbooks describe this process for terrestrial ¯ ora compared with similar
dynamics in the forest canopy involving epiphytic bromeliads. Progressions
in both situations begin with the arrival of relatively stress-tolerant recruits
capable of growing unaccompanied, and diversi® cation continues once
conditions also suit previously excluded, more exacting vegetation.
Superior fecundity and mobility and equivalent stress-tolerance allow
certain species of orchids to accompany or precede the bromeliads. But
whether bromeliads initiate a sequence or join it later, plant size and architecture often assure eventual dominance, especially on relatively harsh substrates.
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Influences of shoot form on bromeliad distribution
369
Influences of shoot form on bromeliad distribution
Shoot morphology and the nature of the foliar indumentum determine
whether a bromeliad can access nutrients in substrates like litter and prey
(Chapter 5). Likewise, shoot form in¯ uences suitability of the phytotelm
types for speci® c climates, especially conditions of humidity and irradiance.
A tubular shoot (e.g., Billbergia porteana; Fig. 2.4K) formed by upright,
tightly overlapped leaves reduces exposure to direct-beam PPFD, and the
resulting deep phytotelm provides substantial insulation for impounded
moisture. At the same time, this arrangement curtails capacity to intercept
litter and precipitation compared with the ¯ at, spreading rosette characteristic of the more shade-adapted species (Fig. 2.4H). Additional con® gurations that ® t neither of these models require different explanations. For
example, the vase-like shoots of Aechmea bracteata allow precipitation and
humus to collect in the bases of moderately aged leaves and house ants in
a central, totally enclosed chamber (Fig. 2.4G). No arrangement is absolutely ® xed of course, as Tillandsia utriculata illustrates under high and low
exposures (Fig. 4.23B,C).
Sugden (1981) demonstrated how wind speed, exposure and humidity
sort a collection of co-occurring bromeliads by shoot architecture. At issue
were eight Tillandsioideae growing along a minor ridge-valley sequence on
the Serrania de Macuria in northern Colombia. Rugged topography and
constant wind direction maintain canopy height between about 1 and 10 m.
Moisture arrives solely as mist for all but about two months during the year.
Figure 7.15 illustrates the order these bromeliads follow as they distribute
by ecotolerance across two adjacent ridges beginning with the relatively
cloud-free leeward slope on the right to ridge top and beyond.
Heliophilic Guzmania monostachia, semibulbous Vriesea heterandra and
a few succulent Tillandsia bulbosa specimens that feature onion-like shoots
regularly utilized by ant colonies at drier, warmer sites grow at the lowest
elevations in the thinnest canopies (Figs. 7.15, 8.5). Approaching the
summit, the ® rst and last species virtually disappear, replaced by more
hygrophilic taxa with lax, soft rosettes and shallow tanks (Guzmania lingulata, G. sanguinea and Vriesea splendens) that reach maximum densities at
or near ridge top. More generally distributed V. heterandra also becomes
commoner in the especially thick ridge-margin forest.
Greater cloud ¯ ux, denser and taller canopies, and coalesced rain drops
carried over from the next windward ridge combine to create wetter conditions along sheltered ridge margins compared with the leeward slopes.
Epiphytes on windward inclines intercept the most moisture of all, but
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Ecology
Figure 7.15. Shoot architecture and occurrence of eight bromeliads along a ridgevalley system in a northern Colombian cloud forest (after Sugden 1981).
during drier periods the same air currents impose high evaporative
demand. Bromeliads with the shallowest tanks (¯ attest rosettes) rarely
grow here. Scattered individuals of V. heterandra, which is easily identi® ed
by its upright, rigid leaves and capacious reservoir, occur instead. Taller
trees in the gully below support delicate, shade-tolerant Guzmania lingulata
and G. sanguinea. Guzmania monostachia begins to reappear and Vriesea
heterandra continues as a fairly common epiphyte. Although cloud contact
diminishes at this point, a dense canopy and relatively still air substantially
reduce drought-stress.
Similar morphology over extensive ranges indicates that none of these
eight bromeliads underwent gross structural change to accommodate conditions speci® c to the Serrania de Macuria ridge system. Selection operating at the Colombian site simply arrayed pre-adapted types to match the
multiple local microclimates. Another bromeliad ¯ ora exhibits the same
general pattern in the central cordillera of Costa Rica (Burt-Utley and
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Influences of shoot form on bromeliad distribution
371
Utley 1980). In this instance, strong winds sweeping up from the Atlantic
coastal plain permit only the most xeromorphic of the local stock, those
species with modest phytotelmata and dense indumenta (e.g., Vriesea incurvata, V. chontalensis, Tillandsia adpressa var. tonduziana) to occupy the
most demanding exposures. Residents with deeper tanks and softer, more
glabrous foliage grow on the less breezy, leeward sides of trees or hills in
patches of sheltering forest (e.g., Werauhia attenuata, Vriesea comata).
Reliance on leaves to secure the resources that most plants acquire with
roots further assures that the size and shape of the shoot inordinately in¯ uence geographic distributions for many Bromeliaceae. Form and function
at this scale affect species through a much wider range of growing conditions than those prevailing in the mountains of northern Colombia and
Costa Rica. Figure 7.16 plots four models representing Bromeliaceae
equipped with carnivorous, humus-based, tubular (vertebrate-fed?) and
myrmecotrophic shoots according to their putative capacities to maintain
adequate ion, water and carbon balance along gradients of light, moisture
and litter supply.
The carnivorous habit, here exempli® ed by terrestrial Brocchinia reducta
(Fig. 2.4F), requires intense PPFD and a liberal supply of moisture to compensate for the self-shade cast by tight, overlapping leaves and the costs of
the fragrances and abundant leaf coating needed to lure and trap prey
(Givnish et al. 1984; Chapter 5). Next by niche breadth come the tubular
species represented by Billbergia porteana (Fig. 2.4K). Although similar in
shape to the carnivores, these plants lack the costly lures and thick,
powdery cuticle Brocchinia reducta and Catopsis berteroniana employ to
capture prey.
Nidularium burchellii intercepts more direct-beam sunlight than plants
faithful to any of the other three models, but its monolayered, relatively
drought-sensitive foliage and shallow leaf bases restrict occurrence to
humid, usually understory habitats. Demand for litter as a nutrient source
further mandates anchorages deep in Atlantic rainforest along with numerous comparably vulnerable relatives (e.g., many Canistrum, Nidularium and
Wittrockia species). Ant-fed, ant-house types (model four) provide the
greatest ¯ exibility of all (Fig. 8.5A). Dry leaf base chambers attract plantfeeding ants and leaf succulence serves in lieu of a phytotelma. Mostly nonoverlapping leaf blades and transparent, immobile and appressed
(light-focusing?) trichome shields (Fig. 4.23F) permit survival to the low
ends of light gradients.
This admittedly facile speculation on comparative functional morphology barely begins to unravel the complex, niche-de® ning interplay that
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372
Ecology
prevails between moisture, nutrient and energy supplies and the architecturally mandated growing requirements that encumber speci® c bromeliads.
For example, no consideration is assigned to differences in the longevities
of shoots that affect mineral-use efficiency, hence nutritional requirements.
And no weight was granted to photosynthetic pathway despite signi® cant
consequences for carbon and water budgets. Inherent differences in plant
vigor and related needs for nutrients like N were also ignored.
Should a root system provide more than mechanical support, the inferences depicted in Fig. 7.16 become even more tenuous. Economic models
purported to predict where (what kind of environment) speci® c plants
should achieve highest performance must incorporate external and inherent constraints on growth and reproduction. Moreover, a fuller understanding of how shoot form in¯ uences shade and drought-tolerance and
the utility of certain substrates as soil substitutes will yield additional
insights on plant adaptation and evolution. Probably no other radiation
within the boundaries of a single family equals that of Bromeliaceae for
variety or extremes in the types of habitats colonized, the kinds of substrates utilized, and the manner in which resources are captured and
retained.
Effects of epiphytic bromeliads on trees
The case for parasitism
Textbooks routinely dismiss the autotrophic epiphytes as unimportant to
hosts, and they say nothing about the roles these plants might play within
communities and ecosystems. Abercrombie et al. (1970) de® ne the epiphyte
in their Dictionary of Biology simply as `a plant attached to another plant,
not growing parasitically upon it but merely using it for support' .
Commensalism is the standard explanation except when heavy infestations
shade out foliage or break overburdened branches. Casual observers
throughout tropical America continue to believe that bromeliads, particularly Tillandsia usneoides (Fig. 7.7C) and T. recurvata (Fig. 7.7D), parasitize trees. Accumulating data and some thoughts about how the
nonhaustorial epiphytes obtain nutrients suggest that these claims lack
merit, but raise interesting issues of another sort.
Frequent occurrences on dead branches and rocks, and even the occasional telephone wire, demonstrate the dispensability of a living host for
epiphytic Bromeliaceae (Fig. 1.3A). Self-sufficiency is further indicated by
roots, which although they enter crevices in bark, never penetrate function-
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Effects of epiphytic bromeliads on trees
373
Figure 7.16. Two graphic models that use economic considerations to predict the
occurrence of shoot-dependent (holdfast roots only) bromeliads relative to the
availability of light and moisture and litter and ant products as sources of nutrients.
ing vasculature. In fact, roots of the species most often considered parasites
lack signi® cant absorptive capacity or the adult (e.g., T. usneoides, T. capillaris, T. duratii; Fig. 2.10L) rarely, if ever, produces them. In the ® nal analysis, claims for parasitism by direct or indirect (epiparasitism) mechanisms
lack substance. Still, appearances call for an explanation.
Billings (1904) commented on the premature decline of trees supporting
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Ecology
Spanish moss in the southeastern United States (Fig. 7.7C), but he ventured no further than to say that experiments conducted over many years
would probably be necessary to identify the cause. A pervasive condition
involving arboreal ¯ ora and some data on distributions in tree crowns
provide a glimpse of what seems to take place between at least some epiphytic Bromeliaceae and their hosts. Knowledge of tree architecture and
ontogeny aid interpretations of some of the more provocative observations.
Despite morphology that precludes bromeliad parasitism, trees densely
colonized by essentially rootless Tillandsia sometimes show distress seemingly imposed by these epiphytes. Heavily encumbered Quercus virginiana
in parts of central Florida tend to feature fewer and smaller leaves than
usual and inordinately large numbers of dead and dying twigs and larger
branches. Figure 7.7C illustrates a live oak festooned with T. usneoides and
scattered T. recurvata colonies, whereas Fig. 7.7E shows the much denser
crown of a relatively epiphyte-free live oak about 300 m distant. Did the
bromeliads on the ® rst oak arrive after or before it began to deteriorate? If
before, then how might the bromeliads contribute to this decline?
Landscapers in central Florida continue to use herbicides to remove
Tillandsia recurvata and T. usneoides from shade and orchard trees to
reduce what Ruinen (1953) labeled `epiphytosis' . Treated phorophytes
usually escape injury, and, more revealing to us, they often produce fuller
crowns within a season or two. Several more authors reported similar signs
of distress in trees supporting abundant orchids (e.g., Cook 1926;
Johansson 1977). The offending ¯ ora in these cases supposedly acted by
girdling and epiparasitism respectively. Epiphytic Bromeliaceae are only
occasionally mycorrhizal (Chapter 5), and examination of T. recurvata on
a variety of hosts in Florida revealed no girdling roots (Benzing and
Seemann 1978).
Epiphytes often aggregate on dead branches, supposedly illustrating parasitic cause and effect. `Shootless' African Microcoelia (Orchidaceae)
served as Johansson' s (1977) example; Tillandsia recurvata exhibits the
same association in Florida (Benzing 1979). Approximately 80% of the
mature ballmoss colonies scored through the middle to lower parts of
crowns of 10 mature live oaks with normal-appearing foliage occurred on
slender twigs (,5 mm). The remaining adults anchored on larger branches
and trunks. Fully 70% of those smaller axes that supported mature bromeliads were dead, but so were many others free of epiphytes. Here at least, tree
development provided a more convincing explanation for the overoccurrence of ballmoss on lifeless twigs than parasitism.
Trees, despite their larger size, like many herbs exhibit determinate
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Effects of epiphytic bromeliads on trees
375
Figure 7.17. The progression of events during phorophyte ontogeny that can
produce the illusion of parasitism by resident epiphytes. The crown area enclosed
in dashed lines represents the self-shaded region where branches will normally die
whether or not epiphytes are anchored there (after Benzing 1979).
growth. Beginning with a single trunk, the crown expands in programmed
fashion after which it dies, usually in stages. In fact, for much of the life
cycle new branches arise while many of the older ones succumb. Three
factors determine how long each component (stem) of the crown survives:
its place in space and time within the ontogenetic sequence, the model-speci® c form of the species (Hallé et al. 1978), and local circumstances that
affect the plant' s ability to conform to its architectural model.
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Ecology
Crown growth begins with the formation of a number of primary lateral
axes (Fig. 7.17). Years later all or most of the lowest members have died
and fallen away, leaving those above to proliferate. Surviving second-order
axes undergo a third rami® cation and so on as the crown continues to
enlarge. Repeated subdivisions, usually no more than ® ve or six in all, yield
a sequence of progressively smaller branch complexes arrayed in patterns
dictated by the developmental programs associated with the more than 20
currently recognized tree models (Hallé et al. 1978).
At some point, the crown periphery where most of the remaining active
meristems occur reaches maximum size and lapses into a kind of dynamic
equilibrium. Over additional seasons, terminal shoots elongate slowly
while generating leaves and reproductive organs, much as herbs (e.g.,
Solidago) regenerate from perennial bases each year in an old ® eld community in the central United States. For a time, new branchlets replace those
lost through attrition and the outline and density of the crown remain little
changed. However, wholesale senescence eventually ensues and new meristems no longer replace those spent, and the crown begins to thin.
Eventually, whole branches die, and ® nally wind, pathogens or predators
dispatch the entire plant.
Viewed ontogenetically, a tree constitutes an ordered mosaic of semiautonomous parts, each programmed for a ® nite life span. Every component of the crown falls into one of a series of distinct and successive, but
temporally overlapping, populations of shoots. Major axes ± the trunk and
its ® rst-order branches ± live longest according to a simple rule: whatever
their size, each component must remain autotrophic, the larger ones
through the vitality of attached, higher-order shoots. Death follows exposure below the light compensation intensity of attached foliage whether
through self-shading or overgrowth by competing ¯ ora. Relatively determinant lateral shoots that serve primarily to provide photosynthate for
expanding leaders fall away as the crown expands. Displacement inward
insures that the durability of such anchorages for epiphytes typically falls
well short of the life of the whole tree (Fig. 7.17). Whether growth proceeds
normally or not, plants attached to these axes assume the appearance of
parasites, i.e., they appear to have starved the stems that now can provide
only mechanical support.
If one of the branches making up a tree crown remains exposed longer
than usual as the model unfolds, the life of that axis is prolonged, and
accordingly, the likelihood of its colonization by epiphytes increases. At
some point, this exceptional shoot dies, but only after similarly programmed parts of the same crown fall away on schedule. The longer oppor-
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Effects of epiphytic bromeliads on trees
377
tunity for autotrophy is extended, the more abundant and larger the
affected epiphytes become. In essence, as the durability of the exceptional
branch increases, so does the chance that the epiphytes located there will
appear responsible for its postponed death.
Little is known about the light requirements or life histories of the bromeliads that mimic parasites. Most of them probably need several years to
mature and additional time to become robust adults. Assuming at least
moderate vulnerability to the shade and rain shadows cast by heavy foliage,
the highest densities of the largest specimens should occur on those substrates most conducive to photosynthesis. Such sites concentrate near, but
not at, the center of the crown, exactly where several studies (e.g.,
Johansson 1975; Catling et al. 1986) documented the highest abundances
of epiphytes (Fig. 7.12). Substrates closer to the trunk become shaded too
quickly during tree ontogeny to support comparable densities of epiphytes,
while perches at the crown margin subject attached plants to greater evaporative demand and more intense light (Fig. 7.17).
So it seems that the overoccurrences of epiphytes on dead and dying
branches need not signal parasitism. More likely, these associations occur
because the branches involved are relics granted extended life by extraordinary exposure or, if smaller, like those dead oak twigs bearing adult T.
recurvata in Florida, simply died after a normal, brief life span.
Mechanisms unrelated to nutrition
Bromeliads sometimes injure the trees they utilize in ways that have nothing
to do with mineral nutrition. Holcomb (1995) reported that the naturalized
population of Tillandsia recurvata mentioned earlier is killing the lower
branches of crape myrtle trees. Growth ceases after clumps of the epiphyte
encircle the tips of affected shoots. Calver et al. (1983) attributed the rapid
spread of Tillandsia aeranthos and T. recurvata in and around La Plata,
Argentina to allelopathy. Infested conifers and broad-leafed trees alike lose
vigor and leaf area, which probably bene® ts these heliophiles much as the
stressed canopies of cypress favor dense colonies of T. paucifolia in south
Florida. No evidence was provided for the existence of the alleged inhibitor beyond demonstrating the phytotoxicity of unfractionated leachates in
crude bioassays.
Results of another assay using similarly prepared extracts of T. recurvata
and tobacco callus were negative (Holcomb 1995). Disease is another possibility. Fungi (e.g., Rhizoctonia spp.) harbored in the protocorms and roots
of certain orchids become pathogenic in more susceptible ¯ ora (Hadley
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Ecology
1982). Those vesicular-arbuscular mycorrhizal fungi reported in certain
arboreal Bromeliaceae and described in Chapter 5 should pose no problems for hosts, but additional, unidenti® ed mycelia infecting some of the
same roots and those of other epiphytes may attack adjacent stems.
Large branches occasionally break under the weight of attached bromeliads, and possibly smaller shoots succumb to constricted vasculature. If
orchid roots indeed girdled those Citrus branches that Cook (1926)
inspected in Puerto Rico, then Bromeliaceae with wiry holdfasts should
pose an even greater threat to similarly vulnerable hosts. In any case, dismissal of this possibility requires more than one set of observations on ballmoss in Florida.
Competition for light can be a problem for the heavily infested tree, for
example those previously described live oaks and cypress in the southeastern United States (Fig. 7.7C,D). Leguminous Cercidium praecox may be
exceptionally vulnerable owing to its reliance on green bark while lea¯ ess
during extended dry seasons in central Mexico. Montaña et al. (1997)
employed a multinomial model to demonstrate that dense colonization by
Tillandsia recurvata reduces the vitality of this small tree branch by branch.
Speci® cally, heavily shaded axes produced fewer lateral shoots than less
encumbered branches in the same crowns, yielding a pattern similar to that
just described for associations involving this same bromeliad and Quercus
virginiana in Florida.
Curiously, trees that support massive trusses of Spanish moss and high
densities of Tillandsia recurvata colonies sometimes exhibit considerable
die-back and not just the loss of those small, subordinate branches mentioned in the discussion of tree architecture and ontogeny. Undersized,
chlorotic foliage further suggests a systemic rather than a localized cause.
Benzing and Seemann (1978) coined the term `nutritional piracy' to
describe a proposed mechanism.
Nutritional piracy
A tree need not be a host to parasites to nourish plants anchored in its
crown. Arboreal Bromeliaceae possess several options that grant them
noninvasive access to the nutrient capital present in living supports. In each
case, the epiphyte ipso facto functions as an indirect parasite, or what might
be more descriptively labeled a nutrient pirate. Rather than invading xylem
or phloem, the resident bromeliad in effect pirates nutrients as they ¯ ux
between the tree and its rooting medium during routine biogeochemical
cycling. Simply put, essential ions pass from phorophytes to associated
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Effects of epiphytic bromeliads on trees
379
Figure 7.18. Schematic representation of input of nutrients from the atmosphere
and mineral cycling in a tropical humid forest depicting the pirating activities of resident epiphytes.
arboreal ¯ ora as part of a pervasive ecosystem-level process, effectively rendering mechanically dependent ¯ ora parasites of a remote kind.
Elements like K and P, unless immobilized in wood or some other similarly inert, relatively durable tissue, move through a tree rather rapidly,
returning to the soil within months to a few years. Litter delivers nutrients
to the understory for subsequent release by mineralization; precipitation
leaches additional quantities, especially of K, directly from living tissues.
Returned to the root zone by either route, recapture and redeployment
follow (Fig. 7.18). Porous, infertile substrates oblige efficient recycling to
retain sufficient nutrient capital within the ecosystem, much of which at any
time resides in phytomass (Jordan 1985). Failure to recycle scarce ions shed
in litter and leachates could stress trees on impoverished sites, perhaps as
much as if they supported substantial masses of parasites.
`Parasitism' describes associations that involve direct transfers; nutrients
¯ ow from one individual comprising the combination into the other.
Mistletoes and the root parasites penetrate host vasculature with haustoria,
whereas the epiparasites (e.g., Monotropa) employ a fungus, obviating the
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Ecology
need for plant-to-plant union. Lacking invasive organs and probably the
appropriate fungi, the epiphytic bromeliad functions neither as a parasite
of either type nor as a competitor for nutrients in soil, the most extensive
plant-accessible source in a forest. Nevertheless, phorophytes lose essential
ions to resident epiphytes to the extent that this strategically positioned
¯ ora taps the cycle that permits long-lived vegetation to remain adequately
nourished through extended life spans.
Nonimpounding Bromeliaceae extract ions from rainfall, leachates and
dry deposition, whereas those with phytotelm shoots also utilize litter,
which incidentally usually falls through the canopy rather than augmenting the suspended, soil-like substrates so essential to the more drought-sensitive epiphytes (e.g., arboreal bryophytes; Nadkarni and Matelson 1991).
Moreover, slow growth, long life and modest litter production (no leaf
abscission) combine to insure that the nutrients co-opted by epiphytic vegetation remain sequestered above ground unavailable to the tree for
extended periods. So it seems that capacity to scavenge ions from canopy
¯ uids and shed phytomass, durable foliage, and a propitious site in the biogeochemical cycle place arboreal Bromeliaceae in an extraordinary position to in¯ uence the welfare of trees and affect broader community-wide
phenomena that also involve plant nutrients.
Data from two sites in Florida demonstrate the magnitude of the pirating activities of local Bromeliaceae and perhaps the consequent effects on
the growth of co-occurring Quercus virginiana (Benzing and Seemann
1978; Fig. 7.7C,E). Crowns of the oak trees located several kilometers
north of Naples in coastal strand vegetation supported dense Spanish moss
and ballmoss populations and scattered individuals of Tillandsia balbisiana, T. fasciculata and T. utriculata (Fig. 7.7D). Fruticose lichens,
poikilohydrous Selaginella arenicola and scattered forbs provided a sparse,
patchy cover over impoverished, acidic, sandy soil (Table 7.1). Sampling
demonstrated de® ciencies in the trees dependent on these relatively sterile
media.
Tillandsia biomass contained 35± 57% of the total N, P and K present in
the crowns (foliage, subtending twigs, and attached bromeliads) of two representative oaks at the more impoverished of the two sampled locations.
Oak leaf chemistry also con® rmed the relatively oligotrophic quality of this
habitat for epiphytes compared with that supporting more vigorous phorophytes near Tampa, Florida (Table 7.2). These data pose several worthwhile questions: how much dwar® ng would prevail today among the
woody ¯ ora at the coastal strand site had no bromeliads been present
during its development? Would Quercus virginiana be more robust, i.e.,
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Table 7.1. Soil fertility data (mean ppm and standard error) and pH (mean and standard error) for two sites in Florida
Site 1: Dwarfed oak
Site 2: Vigorous oak
Available Ca
Exchangeable K
Available Mg
Total N
Available P
pH
3226221
4776124
23.360.8
54.565.7
41.863.41
63.3610.8
227064281
939262234
12.760.3
25.867.8
5.0360.16
4.8260.27
Source: After Benzing and Seemann (1978).
Table 7.2. Mineral nutrient concentrations in leaves of dwarfed and vigorous oaks (Quercus virginiana) and the shoots of
their respective Tillandsia usneoides colonists
% dry weight
Leaves from canopies of dwarfed oaks
Leaves from canopies of vigorous oaks
Shoots of T. usneoides on dwarfed oaks
Shoots of T. usneoides on vigorous oaks
ppm
N
P
K
Ca
Mg
Na
Mn
Fe
B
Cu
Zn
1.43
1.88
0.95
1.19
0.236
0.286
0.140
0.133
0.826
0.846
0.463
0.520
0.752
0.629
0.700
0.587
0.205
0.234
0.197
0.153
0.051
0.043
0.130
0.130
128.1
204.7
57.3
114.0
145.5
116.0
471.3
457.3
20.0
21.2
16.3
17.0
13.8
16.2
10.3
10.0
37.0 1.30
38.2 1.36
27.0 1.66
57.0 1.40
Source: After Benzing and Seemann (1978).
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382
Ecology
better nourished, in the epiphyte-free system? How much of the nutrient
capital currently sequestered in the local bromeliads would instead be supporting growth elsewhere in the ecosystem, for example the terrestrial
herbs?
Bromeliaceae may also signi® cantly in¯ uence how key nutrients are
apportioned in more typical (fertile) ecosystems. For example, Nadkarni
(1984) reported relatively nutrient-rich throughfall (Ca, K, Mg, N, P
enrichments) beneath Clusia alata branches bearing heavy growths of epiphytes, including bromeliads, in a Costa Rican cloud forest using pair-wise
tests. Contrary to the wetter months, dry-season rainfall lost ionic strength
while moving over the same phytomass. Extrapolations to whole systems
will require ® ner-grained sampling because forests and even individual tree
crowns constitute successional mosaics. Limbs that support colonies of epiphytes younger or older than those sampled by Nadkarni probably gain or
lose solutes accordingly, as do entire ecosystems depending on their state
of maturity.
Effects of bromeliad nutrition on forests
Epiphytic Bromeliaceae may not be parasitic, but they capture nutrients
that otherwise would be available to supporting trees for an initial interval
(following arrival from the atmosphere) or for second or more successive
terms of service (recycling ions). Consequences for phorophytes and ecosystems vary depending on the context. Determining factors range from the
abundance and maturity of the resident arboreal ¯ ora (not just
Bromeliaceae) to the fertility of the local soils. Expanding populations of
epiphytes accumulate nutrients, but later they probably reach equilibrium,
matching gains with losses, i.e., they act more like charged capacitors than
sinks as at Nadkarni' s Costa Rican site. A second issue concerns nutrient
use. Does the N and P sequestered in epiphyte biomass support enough
photosynthesis to compensate for the diminished outputs by hosts and
other plants deprived of these same resources? Would, in fact, nutrient
capital sequestered in epiphyte tissue be deployed elsewhere in the ecosystem had arboreal ¯ ora failed to colonize the site?
Few inventories of tropical forests identify the contributions that resident epiphytes make to standing phytomass, or to total nutrient capital;
none of them report contributions to overall forest productivity (e.g.,
Fittkau and Klinge 1973; Edwards and Grubb 1977; Golley et al. 1978;
Tanner 1980; Grubb and Edwards 1982). Vascular epiphytes never account
for more than a few percent of the total above-ground phytomass, too little
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Effects of bromeliad nutrition on forests
383
at ® rst glance to imagine substantial in¯ uences. However, perspectives
change when the contribution of the epiphytes, which are predominantly
green tissue, is compared in terms of impacts on the energy budgets of
hosting ecosystems.
Edwards and Grubb (1977) determined that the resident epiphytes
weighed about half as much as the rest of the foliage comprising the canopy
of a New Guinea lower montane rainforest, and Tanner (1977) obtained
values up to 35% in bromeliad-rich, montane Jamaican sites. Combined
nonvascular and vascular epiphytes also accounted for much of the green
phytomass in a Costa Rican el® n forest (Nadkarni 1984). Moreover, this
compartment contained up to 45% of the totals of several key elements
present in tree leaves and epiphytes combined. Contributions of the epiphytes to whole-system photosynthesis probably also vary depending on
growing conditions, particularly water supply.
Bromeliads and the other epiphytes affect forest productivity and
mineral-use efficiency (MUE) according to local climate through its effects
on energy returns from investments in green tissues. Trees, owing to the relatively continuous supply of moisture in soil, probably outperform associated arboreal ¯ ora on leaf area and weight bases in all but the wettest
locations. The same relationship probably applies for N and P committed
to support photosynthesis. Better adapted for drought, the epiphytes
should achieve higher water-use efficiency, but lower instantaneous returns
on committed nutrients. C3-type compared with CAM foliage, including
that produced by some Bromeliaceae (Table 5.5), contains more concentrated N, and usually supports higher rates of light-saturated photosynthesis (Larcher 1980). However, leaf life span, which is usually longer for CAM
plants, grants greater parity relative to integrated MUE (Chapter 4).
Table 5.5 compares photosynthesis on a leaf area basis for mixed epiphytic plants, including Vriesea platynema, anchored on the lower trunk of
a single Psidium specimen in a seasonal, lower montane forest in northern
Venezuela. Water-balance mechanisms and moisture sources accompany
each entry. The tree performed best on an instantaneous basis in terms of
photosynthetic rate and N and P-use efficiency, but the well-watered C3 epiphytes followed close behind. However, integrated values would have
reduced the disparities because some of the foliage sampled abscises
(Microgramma lycopodioides) or becomes sufficiently moisture-stressed to
curtail carbon gain during dry weather.
Note that only one of the epiphytes exhibited net photosynthesis prior
to irrigation. Vriesea platynema remained inactive until recharged, its
sizable phytotelmata having dried out before the run. Adams and Martin
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Ecology
(1986a) reported similar behavior in Tillandsia deppeana during comparisons of drought-tolerance between adults and juveniles (Fig. 4.9). Both sets
of data help explain the absence of Type Three and Four bromeliads in
strongly seasonal habitats. Species equipped with phytotelma require at
least 1500 mm precipitation year21 in Jamaica (Laessle 1961), and
Gilmartin (1973) recorded a similar relationship in Ecuador.
A sizable mass of vegetation suspended in a forest canopy, particularly
if dominated by phytotelm Bromeliaceae, traps substantial nutrient capital
and promotes important, less recognized biological variety as described in
the next chapter. Those Venezuelan epiphytes on the guava tree, for
example, clearly augmented biodiversity by expanding the list of local
species, but more importantly they increased the variety of important
goods and services (e.g., food and habitat) for other canopy-based biota.
Arboreal ¯ oras incorporating the highest variety, those typically native to
pre-montane to mid-montane forests, probably augment supporting ecosystems the most.
Conceivably, the complex, multilayered systems (sensu Pittendrigh 1948)
that these plants help elaborate utilize resources more efficiently (e.g., calories unit N21 time21), or increase productivity and N2 ® xation beyond
levels possible in their absence. Conversely, the far less diverse bromeliad
¯ oras, mostly Tillandsia species, that nevertheless sometimes densely populate certain drier forests, probably favor different outcomes. Here, diversion of scarce ions co-opted from trees to support the more modest
photosynthetic outputs of Type Five Bromeliaceae more likely diminish
system-wide productivity and reduce instantaneous mineral-use efficiency.
Terrestrial Bromeliaceae
Substrates receive inordinate emphasis in the literature devoted to bromeliad ecology. Authors often allude to a subject' s epiphytic or terrestrial status
as if capacity to root on one or the other kind of medium indicates fundamentally distinct biology. Not so: arboreal and soil-based species frequently share similar life histories, architecture and ecophysiology.
Moreover, additional Bromeliaceae root interchangeably on trees and on
the ground. We turn under this ® nal heading to the taxonomic correlates of
these two life styles, followed by some thoughts about mechanisms insofar
as they differentiate, or in the case of the facultative types fail to distinguish,
populations with terrestrial from those with arboreal habits. Substrates
further subdivide ground-based Bromeliaceae according to anchorage on
soil or rock, and within the ® rst group by the type of habitat (e.g., restinga,
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Terrestrial Bromeliaceae
385
alpine). Lithophytes differ in their relationship to supporting media
depending on the functions of roots vs. shoots.
Bromeliads constitute such a conspicuous presence in the canopies of so
many Neotropical forests that the terrestrials, fully half of the nearly 3000
species, often go unmentioned in texts except for the familiar pineapple.
Conversations about other important family characteristics frequently
re¯ ect the same bias. For example, published descriptions of the phytotelm
shoot and absorbing trichome often allude to importance in aerial environments, ignoring comparable bene® ts for large numbers of identically
equipped relatives that root in soil or on rock. Systematics suggest that
success in tree crowns is recent, and probably required features that
emerged in terrestrial stock and continue to serve those descendants still
growing on the ground.
At least 90% of the arboreal bromeliads belong to fewer than one-third
of the approximately 60 genera. Except for several comparably sized collections of species in Pitcairnioideae (e.g., Puya, Pitcairnia, Navia), epiphytism pervades the largest groups of closely related populations (e.g.,
Tillandsia/Vriesea complex), some showing signs of continuing rapid evolution (e.g., Tillandsia, several subgenera; Chapter 9). Rocky outcrops
accommodate additional species in the same alliances indicating similarity
between epiphytism and saxicoly. Some of the epiphytes also have close,
soil-rooted relatives, especially in Bromelioideae, the subfamily in which
substrate use is most ¯ uid. Overall, Bromeliaceae offer unparalleled opportunity to identify aspects of fruits, seeds and dispersal vs. those of plant
form and ecophysiology that most powerfully dictate matches between
plants and rooting media.
Plant features that favor the use of unconventional substrates emerged
repeatedly as Bromeliaceae colonized diverse, often demanding habitats
(Figs. 9.24, 9.25). Extant Tillandsioideae exhibit the most pervasive dependence on bark and rocks. Some rupicolous Alcantarea andVriesea suggest
the likely ancestral habit with shoots that more closely resemble those
of certain unspecialized terrestrials (e.g., Fig. 2.2F; Chapter 9).
Unfortunately, plant bene® ts (natural selection) responsible for the origins
and the timings of the appearances of CAM, phytotelm architecture and
absorbing trichomes, and the other modi® cations that enable unusual
ecology, remain unresolved despite considerable inquiry and spirited dialogue (e.g., Pittendrigh 1948; Medina 1974; Benzing et al. 1985; Gilmartin
and Brown 1986).
Members of the largest bromelioid genera (e.g., Aechmea, Billbergia),
along with species assigned to many of the smaller ones (e.g., Araeococcus,
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386
Ecology
Acanthostachys), seldom root on the ground. Additional clades feature less
consistent habits, and many members utilize bark and rocks interchangeably (e.g., Nidularium, Quesnelia); occasional epiphytes stand out in otherwise terrestrial taxa such as Fascicularia (e.g., F. bicolor). Still other fairly
sizable assemblages (Cryptanthus, Greigia) never root above ground, at
most scrambling over low rocks as rhizomatous clone-formers.
Requirements for moisture among members of the strictly earth-bound
taxa run the gamut from low to high (e.g., Cryptanthus), and scattered
species (e.g., certain Greigia, Puya species) routinely tolerate standing water
or saturated soils as discussed below. Except for parts of Tillandsia and
Alcantarea, which favor rocky substrata, Tillandsioideae grow as epiphytes.
Primarily ground-based Pitcairnioideae includes the occasional hemiepiphyte (Fig. 2.12B) and some true epiphytes, but quite often species of both
descriptions qualify for facultative status, as described below. Exceptional
members (e.g., Navia tenaculata, Pitcairnia heterophylla) occasionally root
on trunks and large branches in humid forests, but most of the membership colonize rock as do many species in several other genera. Hechtia,
Navia and Puya mostly grow as lithophytes, or rupestrals, or root on
impoverished wet or arid soils, quite possibly as did family ancestors (Fig.
7.1). One of the Guayanan endemics exhibits diversity that mirrors much
of the ecological variety expressed across the entire family. Brocchinia tatei
closely resembles phytotelm Tillandsioideae, and requires similar humid
conditions as an epiphyte or saxicole (Fig. 1.2B).
Other members of this enigmatic genus survive periodic partial inundation in hyperseasonal savannas (e.g., B. prismatica), or achieve the shoot
morphology necessary to house ant colonies (B. acuminata; Fig. 2.2E) or
capture prey (e.g., B. reducta; Fig. 2.4F), or they grow on unembellished
rock without bene® t of impoundments (e.g., B. maguirei). Brocchinia
micrantha simulates some Puya species at lower altitudes as a giant, palmlike terrestrial. An undescribed saxicole ranks among the smallest of all
bromeliads (Holst, personal communication) Finally, B. acuminata
assumes a near vining habit in deep forest like some of the more caulescent
Pitcairnia and Guzmania (Fig. 2.2E). Conspicuously absent are members
equivalent to the succulent xerophytes (e.g., Hechtia, Dyckia) and the essentially rootless, wholly trichome-dependent Type Five Tillandsioideae.
Facultative types
Certain members of all three subfamilies, but mostly Tillandsioideae and
Bromelioideae (e.g., Nidularium, Quesnelia) root on bark and soil. These
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Terrestrial Bromeliaceae
387
facultative types occur in greatest numbers in cool, humid, montane forests,
particularly those featuring thick, sodden mats of bryophytes, lichens and
vascular plants in the canopy and covering the ground (Fig. 1.2B). Another,
smaller group of dry-land inhabitants, primarily members of Tillandsia,
succeed about as well on bare rock or arid soils as on nearby shrubs and
cacti. Adjacent aerial and terrestrial substrates elsewhere support more distinct ¯ oras probably re¯ ecting their more disparate qualities relative to root
aeration and moisture supply. A smaller number of additional taxa (e.g.,
predominantly terrestrial Bromelia and Ananas) exhibit less, but still
enough, ¯ exibility to qualify as accidental or occasional epiphytes.
Occasional populations responding to local conditions constitute still
another category along the terrestrial/arboreal continuum. Zimmerman
and Olmsted (1992) reported that Tillandsia dasyliriifolia grows on bark
and then soil as plants mature at certain seasonally inundated forest sites in
Yucatán State, Mexico (Fig. 6.5C). Juveniles consistently occurred on small
twigs, mostly axes less than 5 cm in diameter. Older, much more massive
adults with sizable phytotelmata consistently ¯ owered on the ground,
apparently re-established there after falling from overburdened, weak
perches. This wide-ranging species grows exclusively on bark in many
upland habitats.
Inundation during the wet season probably eliminates all of the relatively
moisture-sensitive seedlings of T. dasyliriifolia except those attached to a
host, whereas larger plants tolerate the same annual ¯ ooding. Less explicable is the failure of this proli® c bromeliad to colonize thicker supports
capable of bearing its full adult weight. Wide-ranging Tillandsia stricta
sometimes performs similarly, forming almost con¯ uent carpets on the
sand beneath certain shrubs forming restinga `islands' northeast of Rio de
Janeiro, Brazil (Fig. 7.13D). Phytotelm bromeliads displaced from canopies at the same sites usually die because they fail to maintain the upright
orientation necessary to intercept adequate moisture and sunlight.
Mechanisms responsible for arboreal compared with terrestrial status in
the facultative bromeliad remain obscure, having so far attracted little
interest. Obligate and facultative epiphytes alike readily complete life cycles
in ordinary pots containing appropriate soils. Various Tillandsioideae,
especially the dry-growing species, whether epiphytic or lithophytic,
present the greatest challenge to horticulture. Most of these bromeliads
respond poorly to excess moisture, including the mesic types as seedlings.
Subjects with well-developed phytotelma (e.g., Catopsis, Guzmania, most
Vriesea species) tolerate high humidity better than those with denser
layers of trichomes (Table 4.8). So far, nothing de® nitive from greenhouse
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Ecology
experience or nature indicates which plant characteristics dictate rooting
media more than others, or why versatility differs among often closely
related taxa.
Observations in situ, including those just mentioned on T. dasyliriifolia
and T. stricta, plus a single experiment provide some grounds for speculation on the basis of obligate epiphytism. Older plants of routinely arboreal
species once dislodged from the canopy may survive if litter, or some other
kind of porous material, prevents undue contact with soil that remains
moist longer than nearby bark. At one extreme, the heavily trichomed
Tillandsia specimen perishes within a few months regardless of the type of
underlying medium, probably because these plants so readily suffocate in
the humid conditions beneath compared with within the canopy (Fig. 4.11;
Table 4.8). Bromelioideae generally fare better on alternative media. Light
poses an additional threat, as does altered orientation. Loosened epiphytes
that remain suspended upside down or accompany a toppled support to the
ground also usually die. Bleached foliage, especially among downed cloud
forest bromeliads, testi® es to the devastation imposed by abruptly elevated
exposure (Fig. 4.23A).
Matelson et al. (1993) documented the fates of dislodged epiphytes,
including 23 Type Four Tillandsioideae, some of which had fallen in gaps
and others below closed canopy in lower montane rainforest at
Monteverde, Costa Rica. They re-examined each shoot or cluster of
attached ramets monthly for a year and once again on day 637. Mortality
continued unabated for specimens assigned to all eight of the categories
established for members of six angiosperm families, the pteridophytes and
nonvascular ¯ ora. One year later, only 27% of the vascular types remained
alive and just 7% survived two full seasons. Bromeliads lived longer in gaps
than in deep shade, probably because exposures in the ® rst instance more
closely duplicated the drier conditions of the canopy. Excess humidity,
insufficient aeration, or diseases encouraged by both agencies probably
accounted for most of the deaths, although predation cannot be discounted. Jaramillo and Cavelier (1998) attributed lower rates of ¯ owering
among fallen compared with epiphytic specimens of Tillandsia turneri
(Type Four) they surveyed in a Colombian montane forest to the relative
inhospitability of soil. Amorim de Freitas and Scarano (1998) compared
the incidence of epiphytic vs. terrestrial specimens of Nidularium innocentii and N. procerum in a 0.25 ha plot of lowland Atlantic Forest in Rio de
Janeiro State, Brazil that included habitats differentiated by hydroperiod
(soils continuously, seasonally or never ¯ ooded; Fig. 7.13B) and exposure
to sun. They also harvested ramets from terrestrial specimens for attach-
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Terrestrial Bromeliaceae
389
ment to trees that were already supporting these same relatively shade-tolerant phytotelm bromeliads.
Soil-rooted ramets greatly outnumbered those secured to bark, and N.
procerum occurred exclusively in permanently ¯ ooded and N. innocentii
only in periodically inundated sites, perhaps re¯ ecting differences in photosynthetic pathway (C3 vs. CAM) and prevailing degrees of shade (Scarano
et al. 1999). No seedlings occurred on soil or bark, suggesting that sexual
reproduction is rare or limited to favorable years for these populations.
Moreover, the few epiphytic specimens (,2% of the totals for both species)
owed their epiphytic status to growth up trunks from older stock that had
established on the ground. Severed ramets arti® cally attached to trees
rooted, grew and ¯ owered; however, every new shoot produced during the
three-year experiment inexplicably failed to orient upright, and, lacking
capacity to impound water, eventually died.
Amorim de Freitas and Scarano concluded that space for attachment
(less for bark than for soil), lack of competitors, and `rosette stability'
accounted for the tendency of the studied populations to colonize continuously ¯ ooded to seasonally wet sites rather than the drier locations.
Presumably, conditions where these two versatile (e.g., range from 0 to
1300 m) bromeliads regularly occur as trunk epiphytes differ enough to
favor that habit over terrestrialism. Amorim de Freitas and Scarano' s ® ndings point the way for additional questions including designs for observations and experiments that could employ these two bromeliads for more
de® nitive inquiry into the basis of facultative epiphytism.
Exclusively arboreal and soil-rooted species often coexist, but the former
usually prevail in dense forest. Terrestrial bromeliads achieve highest cover
values in woodlands with lower, more transparent canopies, for example in
restingas and deciduous forests (Fig. 7.13C± E). Several other genera
exhibit proclivities to grow either as low epiphytes or as terrestrials in heavy
shade (e.g., Disteganthus, Nidularium, many Pitcairnia, Ronnbergia).
Aechmea magdalenae, which was discussed at some length in Chapter 4,
ranks among the most proli® c (by branching) of the deep forest terrestrials. On Panamanian Barro Colorado island, this spiny, up to 2-m-tall plant
occurs densely enough to almost completely suppress forest regeneration
(Brokaw 1983). Large rodents, and possibly peccaries prior to their elimination from the island, probably helped contain the spread of this vigorous
clone-former.
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Ecology
Ecological variety
Terrestrial Bromeliaceae accommodate diverse growing conditions that
often include substantial drought and, less frequently, ® re (Figs. 2.2G,
6.12). Opportunity for extended life cycles on durable substrates like the
Precambrian outcrops (inselbergs) of the Brazilian Shield (Fig. 1.4A) and
the nightly freezes characteristic of tropical alpine habitats explain certain
other peculiarities of land-based Bromeliaceae. Cool, semiarid conditions
favor still other terrestrials (e.g., Ochagavia and Fascicularia in Chile), as do
boggy substrates at high elevations (e.g., some Brocchinia, and Puya, and
most Greigia). Stands of Brocchinia tatei specimens over 1 m tall dominate
many hectares of windswept, oligotrophic mires on the ¯ anks and summits
of numerous Guayanan tepuis (Fig. 1.2B).
Certain lithophytic bromeliads rank among the most tenacious of all
vascular ¯ ora. Species representing all three subfamilies manage to exploit
sheer rock, sometimes virtually unaccompanied by additional higher
plants. Figures 1.2C and 7.1G illustrate Alcantarea regina and Tillandsia
araujei growing almost alone on a granite dome a few kilometers north of
the city of Rio de Janeiro, Brazil. Figure 7.1E shows an unidenti® ed
Encholirium sp. anchored on a somewhat less precipitous, but equally
barren, igneous outcrop in southern Bahia State. Figure 7.1G illustrating
immature Tillandsia araujei, and another, unidenti® ed Tillandsioideae, also
reveals the coarsely textured surface that assists the securement of seeds
and adhesive roots. Success on these substrates requires the attached plant
to either accumulate a soil-like medium, or rely totally on episodic contact
with precipitation for moisture and nutrients.
Rupestrals
Pitcairnioideae and Bromelioideae have radiated extensively on rocky soils
distributed from Mexico to Argentina. Speciation among the rupestrals has
been especially pronounced on the ancient substrates derived from South
America' s two oldest geological formations. The better known of the two
corresponding bromeliad ¯ oras occupies the upland (to 2000 m) rocky ® eld
habitats called `campos rupestres' located over the Brazilian Shield, mostly
in the states of Minas Gerais and Bahia. Endemics abound, many displaying adaptations peculiar to the growing conditions that characterize these
thinly vegetated (except for the gallery forests) but ¯ oristically mature
regions.
Shoots of rupestral Dyckia, Hohenbergia and Orthophytum, among
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Terrestrial Bromeliaceae
391
others, exhibit striking convergence as if multiple, co-occurring lineages
adopted a limited number of acceptable architectures. Homoplasy includes
additional families, for example Eriocaulaceae (e.g., Paepalanthus bromelioides), that closely resemble co-occurring thin-leafed, phytotelm
Tillandsioideae. Similar leaf morphology and shoot form further complicate the already substantial taxonomic challenge for students of Dyckia
and Encholirium. Tendencies of some of the local nonsucculent bromeliads
(e.g., Alcantarea hatscbachii, A. duarteana) to produce narrow, upright
foliage incapable of impounding reservoirs comparable to those of the
more typical mesic tillandsioids may re¯ ect long histories of competition
for light in these same grassland communities (Chapter 9).
Thin, stony soils overlying predominantly quartzitic bedrock (Figs.
1.2A,E, 1.4C) and seasonal climate also fostered the exceptional endemism,
including many Bromeliaceae (e.g., Cryptanthus leopoldo-horstii,
Neoregelia diamantinensis, Vriesea oligantha), characteristic of the semiarid highlands (the Chapada Dimontina) of south central Brazil. Many of
the campos rupestres plants in this region exhibit qualities suggestive of
evolutionary stasis comparable to that of Bromeliaceae con® ned to the
Guayanan sand savannas and ¯ at-top mountains far to the north where
South America exposes that other part of its ancient granitic core.
Numerous nonbromeliads of the campos rupestres add to the area' s
botanical novelty, and reveal its extraordinary growing conditions and
perhaps island-like insularity as indicated by the presence of woody representatives of typically nonarborescent families (e.g., Asteraceae,
Eriocaulaceae, Velloziaceae). One especially powerful force probably
accounts disproportionately for the unusual structure of much of the native
¯ ora.
Ground ® res fed by sparse fuel punctuate dry seasons that extend
through early to late winter (May/June to August). Frequent restriction of
many local Bromeliaceae to cracks and depressions in the ubiquitous
exposed bedrock testi® es to the protection this arrangement affords seedlings and probably many adults (Figs. 6.5B, 7.1F). Relatively thick, sometimes bulbous stems bearing persistent coriaceous foliage increase
heat-tolerance for those species more routinely exposed to ¯ ames (e.g.,
Cottendorfia florida, Cryptanthus schwackeanus, Dyckia dissitiflora,
Encholirium spp.; Figs. 2.2G, 6.12C± E). Similar morphology characterizes
additional Pitcairnioideae at other locations, for example in the Guayanan
highlands where monotypic Ayensua uaipanensis resembles ® re-tolerant
Vellozia enough to account for its former assignment to that family.
Less insulated Tillandsia (e.g., lithophytic populations of T. arhiza and
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Ecology
closely related T. streptocarpa) occur exclusively on naked rock beyond the
reach of ® re, while the ubiquitous local termite cartons protect other bromeliads nestled amid ¯ ammable grasses and forbs (Fig. 8.1E). Burns may
induce ¯ owering in some Pitcairnioideae as occurs for certain orchids and
some other herbaceous perennials in other ® re-prone communities (Leme
and Marigo 1993). Although the rupestral bromeliads of northern South
America and southeastern Brazil represent different parts of the family (no
species and few genera overlap), they share too many structural characteristics to imagine anything other than parallel ecological histories.
Aquatics
Although Bromeliaceae concentrate more in arid than in humid habitats, a
substantial number of the terrestrials constitute wetland ¯ ora, by virtue of
either propensities for occurrences in seepages or media subject to seasonal
inundation (Figs. 1.4G, 7.13B). Epiphytes native to pluvial mossy forests like
those of Colombia' s Chocó also qualify as hydrophytic because rooting
media, whether suspended or on the ground, usually exist at or near ® eld
capacity. Several reportedly rheophytic Guzmania and Pitcairnia species
unequivocally qualify as aquatics. Modi® cations for immersion in swift,
¯ owing water include ® rmly rooted, long slender shoots and lax, linear foliage.
Guzmania acorifolia, true to its name, looks more like a slender-bodied, emergent aroid than a typical bromeliad along the Nembi River of Colombia.
None of the rheophytes has been examined for features that promote photosynthesis in submerged foliage, or resist shear in turbulent water.
Many more taxa exhibit riverine-type ecology, and resemble typical
members of their genera. Pepinia punicea regularly inhabits rocky streamside sites in southern Mexico and Belize. Occasional populations tolerate
brief submergence, while others occur well above the high water mark. A
white-¯ owered form of the unusually polymorphic Pitcairnia flammea
grows more as an amphibious than a submerged aquatic along the low
banks of mountain streams near Teresopolis, Brazil (Fig. 1.4G).
Additional bromeliads with no obvious adaptations for ¯ ood-tolerance
experience partial inundation for months each year in coastal swales and
swamp forests as described below.
Lithophytes
Lithophytic Bromeliaceae exhibit considerable variety in the ways they
meet basic needs despite anchorage on demanding to essentially unyielding
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393
substrates. Exposed outcrops free of deep ® ssures or pockets of soil deter
all but those populations capable of amassing soil substitutes (Figs. 1.2C,
2.4), or subsisting on the moisture and ions that foliar trichomes scavenge
during transitory contacts with precipitation and related washes (Fig.
4.23E). Some of these same true lithophytes share space with their simulators on more highly weathered or fractured facies that provide more continuous supplies of moisture and nutrients to ¯ ora equipped with extensive
absorptive roots (e.g., Navia, Pitcairnia).
Capacity to rely on foliage rather than roots for absorption accounts for
the inordinate contribution Bromeliaceae make to the lithophytic ¯ ora of
tropical America. Propensity for saxicoly and the often hyperdispersed
nature of rocky habitat in turn explain much of the narrow endemism that
distinguishes this family (Fig. 1.4A). Dozens of Tillandsioideae (e.g.,
Tillandsia neglecta, T. thiekenii, T. sucrei) grow exclusively on rock, some
restricted to one or a few formations in Minas Gerais and contiguous states
in southeastern Brazil. Additional Andean populations, particularly in
Peru, also cling to rock, and like their relatives on the inselbergs of Brazil,
enough divergence has occurred to justify recognition of dozens of narrowly insular species (e.g., T. ecarinata).
Certain Type One succulents (e.g., Hechtia, Dyckia, Encholirium; Fig.
2.2A,B) native to rocky outcrops fall somewhere between the true lithophytes and their simulators. Water-storing shoots recharge during the wet
season through shallow, highly branched root systems rather than absorptive foliage (Fig. 7.1B,E). Members of several predominantly soil-based
genera (e.g., Bromelia) tap leaf axils, and perhaps also deep-seated supplies
in fractured rock. Beyond the requisite dispersal mechanisms and capacity
to establish on precipitous surfaces, the simulators, and probably many of
the intermediate forms, possess no obvious additional qualities for saxicoly,
and indeed many of them grow about as well in soil or have fully terrestrial
close relatives (e.g., many Pitcairnia).
Lithophytic bromeliads evolved repeatedly where suitable substrates and
appropriate stock permitted. Taxa like Tillandsia calcicola, which is
endemic to the limestone outcrops of western Jamaica' s Cockpit Country,
represent recent derivatives from wider-ranging stock, probably something
similar to typical T. fasciculata. Additional rock-dwelling relatives of this
same robust, mostly epiphytic bromeliad occur scattered through
Mesoamerica. Tillandsia utriculata provides a parallel through much of the
Caribbean into Mexico.
Extensive rocky habitat in Mexico, the Andes, southeastern Brazil and
the Guayanan highlands fostered far greater radiations in Bromeliaceae
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Ecology
than occurred in Jamaica, some of these events accounting for more than
100 surviving lineages. Guayanan Pitcairnioideae provide the best example,
apparently because extended time, deeply dissected topography, and
geology combined to create exceptionally propitious conditions for vicariance. Some 140 of the approximately 750 species comprising this subfamily and seven of the genera occur exclusively in the Guayanan highlands,
many con® ned to narrow ranges.
A shield of proterozoic igneous and metamorphic rock (granites, porpyries, gneisses and schists) overlain by up to 3000 m of weathered sandstone
known as the Roraima Formation underlies the `Pantepui' where much of
Pitcairnioideae apparently differentiated and remains as an admixture of
relic and more advanced lineages. Local species representing the other subfamilies (e.g., Aechmea brevicollis, Catopsis berteroniana, Tillandsia complanata) generally range well beyond this region. Low, dome-shaped, lava
intrusions known as `lajas' and the much taller ¯ at-topped, steep-sided
`tepuis' occur nonuniformly across the Pantepui (Fig. 9.1). Their summits,
routinely shrouded by clouds, support uniquely oligotrophic and boggy
vegetation on acidic, highly degraded quartzites and sandstones (Fig. 1.2B).
Carnivorous plants occur in variety equaled only on the similarly ancient
and impoverished soils of southwestern Australia (Givnish et al. 1984).
Brocchinia reducta and B. acuminata rank among the most widespread
of the Guayanan endemics, ranging through low and high savannas and up
on to some of the table mountains. The balance of Brocchinia (e.g., B.
cowanii, B. bernardii, B. cryptantha) and members of the other specialized
pitcairnioid genera of the region exhibit much greater insularity, sometimes
inhabiting only one or a cluster of tepuis (e.g., Steyerbromelia and
Brewcaria on Duida and neighboring Marahuaca, Ayensua unipanensis on
Auyan Tepui and nearby Uaipan Tepui). Numerous of the approximately
90 described Navia species (e.g., N. saxicola on Cerro Yapacana) grow on
just one of these steep-sided formations where they often co-mingle on
thin, azonal soil or shear rock with various Brocchinia, Connellia and
Lindmania.
Like epiphytism, saxicoly remains poorly understood. Few lineages in
other families match the most stress-tolerant bromeliads and orchids for
capacity to cling to impenetrable rock, and of those that do, few provide
equal opportunity to study underlying mechanisms. Populations of Vriesea
ensiformis in the state of Santa Catarina, Brazil grow on rocky outcrops,
trees, cacti and even soil, as does Vriesea cereicola in central Peru. However,
the typical bromeliad remains faithful to a single kind of substratum. For
example, an assemblage of dry-growing Tillandsia (e.g., T. brachyphylla, T.
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395
grazielae, T. reclinata) native to southeastern Brazil anchor on rocks, but
never the trees that also lie within range of their wind-dispersed seeds. What
could account for this variety of behaviors?
Redeployment of absorptive function from roots to foliage has not rendered these bromeliads indifferent to supporting media as an agent of
Darwinian selection. But how rock vs. bark has in¯ uenced evolution
remains unclear. Related epiphytes and saxicoles share what seem to be
comparably specialized mechanisms for carbon, mineral and water
balance, so something else must relegate speci® c populations to one or the
other medium. Potentially decisive features, including succulence, CAM,
absorbing trichomes and primarily mechanical roots, characterize all drygrowing Tillandsia. The phytotelm forms share another combination of
structure and function irrespective of the rooting medium. However, body
plan and certain aspects of reproduction among the ® rst group of species
more closely match the type of substrate.
Type Five Tillandsia obliged to root on rock routinely exhibit more pronounced caulescence and ¯ ower less frequently than their epiphytic relatives (Fig. 2.10M,N; Chapter 6). Roots develop sparingly, and although
individually quite long usually branch less than those employed to grip the
more ephemeral surfaces provided by bark. Even stoloniferous Tillandsia
usneoides ® ts expectations if its rocky perches at certain Andean locations
account for body form more than the trees utilized in the vast majority of
its other modern habitats. Conversely, most of the consistently epiphytic
Tillandsia species feature relatively compact shoots, root more profusely,
and generate short ramets after regular, often annual, ¯ owering. Not surprisingly, the weightiest Tillandsioideae, those with the largest phytotelma
(e.g., Alcantarea imperialis, Tillandsia grandis), also colonize rocks, as do
most of the other monocarps because these plants require so many years to
amass the resources needed to produce the single, necessarily large crop of
seeds (Fig. 1.2C).
Life on loosely consolidated media also seems to favor caulescence, but
the effect on root development has been different. Tillandsia latifolia, T.
purpurea and T. paleacea native to the treeless coastal deserts of Peru
produce extensive polsters comprised of thousands of elongated ramets,
many initiated on spent in¯ orescences by T. latifolia var. vivipara. Roots are
few, perhaps re¯ ecting relaxed requirements for conventional anchorage, or
the impossibility of securement on such unstable media. The occasional
epiphyte, like Tillandsia duratii, exhibits a similarly vestigial root system, in
this instance perhaps because foliage that tightly curls around nearby
objects provides adequate suspension (Fig. 2.10L).
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Ecology
Bennett (1991) demonstrated that demography differentiates several
species of Tillandsia according to the substratum. Exclusively saxicolous T.
sphaerocephala features a lower seedling to adult ratio than facultative T.
ionochroma and several other, consistently arboreal taxa (Chapter 6).
Additionally, more branching and less ¯ owering characterized the cliffdwellers compared with the epiphytes. Populations of T. ionochroma
differed by the type of anchorage, although less so than the wholly epiphytic compared with epilithic species. Bennett concluded that the durability of rock for plant anchorage encourages asexual reproduction
(persistence of established genets) over recruitment by seeds. Conversely,
greater fecundity and mobility better match the epiphytes with their
shorter-lived substrates. High reproductive power leading to frequent
recruitment ® gures prominently in the intermediate disturbance model
Benzing (1981b) cited to explain the co-occurrence of Tillandsia species on
many of the same substrates in Florida.
Tillandsia streptocarpa and closely related T. arhiza exhibit two suggestive combinations of architectures and substrates in Minas Gerais State,
Brazil. Populations of the ® rst species grow as either lithophytes or epiphytes, or root on both trees and rocks at a single location. The only colony of
Tillandsia arhiza encountered occupied exclusively rocky exposures just
outside the city of Diamontina. None of the hundreds of unusually robust
individuals showed signs of ever fruiting. Tillandsia streptocarpa, in contrast, bore capsules at numerous sites, and typically from ramets with many
fewer leafy nodes. Tillandsia arhiza appears to be a lithophytic derivative of
wider-ranging T. streptocarpa, differing from it in aspects of vegetative
form and reproduction that again appear to re¯ ect the durability of rock
compared with bark.
Lithic facies of diverse types support Bromeliaceae, and none of these
that by virtue of toxic constituents (e.g., ultrama® cs) might exclude colonists reportedly does so. Texture, exposure and fracturing/weathering probably in¯ uence hospitality most. Bark varies in many more dimensions that
potentially affect plant ® tness, and indeed account for niche partitionment
by narrowly de® ned (twig, knothole, humus and other kinds of substrate
specialists; Fig. 7.12) orchids (Benzing 1990). Rocks may differ in important, still unrecognized ways for use by lithophytic Bromeliaceae. Tillandsia
tectorum densely colonizes fewer than all the strata exposed at some
Peruvian locations, but elevation and associated fog belts may in¯ uence
occurrence more than local geology (Luther, personal observation).
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397
Restingas
Bromeliaceae occur at exceptionally high densities in certain strand communities along marine coasts, especially in the relatively well-studied
`restingas' of southeastern Brazil (Figs. 1.4E, 7.13C± E). Restinga ¯ ora
exhibit characteristic zonation beginning with wind-sculpted to prostrate,
salt-tolerant vegetation (e.g., Clusiaceae, Arecaceae) just above highest
tides. Progressively taller shrubs and trees, including distinctive vegetation
`islands' , extend up to several kilometers inland (Fig. 7.13D). Shallow
brackish lagoons separate successive ridges at many locations, and some of
the higher depressions ¯ ood with fresh water, converting resident
Bromeliaceae (e.g., Aechmea bromeliifolia) into emergent aquatics for
weeks to months each wet season (Fig. 7.13B).
Predominantly terrestrial taxa representing Aechmea, Billbergia,
Bromelia, Hohenbergia, Neoregelia and Quesnelia constitute much of the
restinga understory. Aprons dominated by one or two species often extend
outward for several meters across open sand. Shoots change from spreading to more tubular as full sun replaces shade (Fig. 7.13C). Several
Tillandsia and Vriesea species grow as epiphytes and terrestrials, and in that
order if they require a nurse shrub until large enough to survive on the
ground (e.g., Tillandsia stricta; Fig. 7.13A). Bromeliads that range inland
to higher elevations in Atlantic Forest and beyond outnumber the endemics (e.g., Neoregelia cruenta), consistent with recent stocking from older
(pre-Holocene) formations.
Bromeliaceae of the restinga of Rio de Janeiro State distribute across the
beach ridge system according to qualities of the substrate that probably
re¯ ect stability and age, and plant exposure to wind and sun and perhaps
salt spray (Fig. 1.4E). Occasional natives like Neoregelia cruenta populate
the entire system, maintaining high densities in scattered colonies by
switching from terrestrial to epiphytic habits as open area near the beach
gives way to more continuous woody cover inland (Lacerda and Hay 1982).
About 30 km northeast of the city of Rio de Janeiro in the coastal sand
dune ecosystem known as the Barra de Marica, Dyckia pseudococcinea
occupies open, relatively ¯ at habitat dominated by forbs and low shrubs
several hundred meters behind the forward sand ridges. Scattered Aechmea
nudicaulis, Neoregelia cruenta and Vriesea neoglutinosa co-occur, but
become more abundant seaward as nonvegetated substrate expands.
Tillandsia stricta follows a less continuous distribution, reaching highest
densities on the ground beneath the nurse shrubs required for its establishment (Fig. 7.13A).
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Ecology
Densely branched shrubs (e.g., Clusia spp.) account for most of the
restinga biomass at the Barra de Marica. These same species probably help
enrich and consolidate the sandy soil for more demanding vegetation.
Aechmea nudicaulis, Neoregelia cruenta and Vriesea neoglutinosa form most
of the fringing aprons (Fig. 7.13C± E). Like Bromelia humilis described
below in coastal Venezuela, shade promotes greener in addition to more lax
foliage. Unscreened irradiance appears to severely stress the ramets that
represent extensions of genets that began life under the more equable conditions provided by taller vegetation. Continued proliferation despite the
more severe conditions imposed by open habitat indicates either substantial translocation of photosynthate among attached ramets or greater
capacity for photosynthesis in full sun than demonstrated by Bromelia
humilis in Venezuela (Lee et al. 1989).
Island remnants in the form of senescing and dead shrubs, columnar
cacti, and stranded bromeliads suggest age or storm-related regenerative
cycles perhaps comparable to the mangrove dynamics along storm tracks
in the Caribbean. Skeletons of woody ¯ ora and interspersed, equally rotresistant stolons of bromeliads mark the loci of former restinga islands.
Bromeliad importance measured by biomass and cover values peaks
around mid-cycle. According to Hay et al. (1981) and Lacerda and Hay
(1982), Neoregelia cruenta and co-occurring phytotelm bromeliads add
substantial amounts of organic matter to underlying soil, heightening its
fertility and cation exchange capacity.
Speci® cally, soil sampled from beneath N. cruenta colonies vs. a few
meters distant in open habitat tested at 1.15 vs. 0.39% for soil organic
matter and 3.96 vs. 0.77 for meq 100 g21 soil for cation exchange capacity.
Soil reaction compared more closely (pH 5.3 vs. 5.4). A relatively spreading shoot also assures N. cruenta importance as a recruitment site for
certain shrubs (Fialho 1990), and a source of fresh water for fauna during
droughts (Fig. 8.4D). Frogs that frequent these and the more tubular, moist
refuges provided by co-occurring Bromeliaceae probably lack alternatives
during the dry season (Fig. 8.4).
Coastal Bromeliaceae range northward from the restingas of Brazil into
Mexico to reappear along Florida' s increasingly urbanized southwest coast
and on through the Bahamian islands. Species, subfamilies and plant habits
shift en route. Bromelia maintains a more or less continuous presence in
strand communities northward into Mexico, but no further. Predominantly
terrestrial Bromelioideae prevail in the southern hemisphere giving way
completely to epiphytic Tillandsioideae north of the Caribbean. Tillandsia
contributes virtually everywhere, and accounts for all of the up to seven
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399
species that represent the family in the nearly extirpated coastal landscapes
located between Naples and Tampa Bay (Fig. 7.7D). Local Tillandsia balbisiana, T. fasciculata and T. utriculata occasionally grow on sandy soils in
the fashion of T. stricta in Brazil. Tillandsia dasyliriifolia growing as a low
epiphyte represents Bromeliaceae along the coast north of Merida
(Yucatán State), Mexico. Closely related T. utriculata occupies the same
kind of microsite in south Florida.
Of the seven species of Bromeliaceae native to the west coast of Florida,
Tillandsia recurvata reaches densities great enough at some locations to
almost obscure the foliage of low-growing Quercus virginiana (Benzing and
Seemann 1978; Fig. 7.7D). Night fogs that regularly move on-shore
through the drier winter months probably encourage this extraordinary
abundance. Paci® c coast Bromeliaceae, except for the dense populations of
several Tillandsia species that grow nearly unaccompanied by other vascular ¯ ora through parts of the Atacama region of Chile and similarly hyperarid regions of Peru, remain poorly documented (Chapter 9). Recall that
Tillandsia recurvata survives exclusively on fog water at similar latitudes in
Baja California (Barry 1953).
Alpine species
Alpine, as distinct from montane, Bromeliaceae range from Mexico to
Argentina, Bolivia and Chile, but diversity peaks in the northern and
central Andes. One subfamily, and primarily Puya, accounts for most of the
family' s representation above 3000 m. As the tallest plants in many of these
stark, thinly vegetated landscapes, members of this genus often attract
inordinate attention from local vertebrates, particularly birds (Fig. 14.2C).
Perches, shelters, nesting sites and, during anthesis, abundant nectar assure
high importance to these demanding animals. Suitability for cool, dry sites
permits several of the largest puyas to dominate some of the highest communities in South America.
A moderate number of tillandsias, some additional Pitcairnioideae and
fewer Bromelioideae co-occur with alpine Puya, but except for Greigia
these bromeliads represent exceptions within clades with more fundamental affinities for warmer habitats. If tolerances for drought, frost and high
irradiance existed in the ancestors of Puya, they probably intensi® ed as
northwestern South America began its on-going orogeny. Whatever the
case, Puya almost certainly underwent much of its diversi® cation during
the past 3± 5 million years in concert with and probably in response to the
combined effects of substantial climate change and mountain-building.
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Ecology
Current distributions and paleoclimatology suggest that much of the
impetus for speciation leading to approximately 185 species was provided
by mean temperatures that oscillated through the Plio-Pleistocene, repeatedly expanding and contracting paramo and subparamo habitats and fragmenting the ranges of resident ¯ ora.
Taxon-speci® c structure and function suggest characteristics that
differentially in¯ uenced the magnitudes of alpine radiations, and continue
to affect the vulnerabilities of surviving lineages. Dry fruits that release
seeds poorly designed for wind carriage probably help explain the exceptional endemism in Puya (Figs. 3.9, 9.2). Fires set by farmers threaten a
number of taxa represented today by scattered small populations. Puya
compacta, P. nutans and P. sodiroana, among others, persist as isolated
stands, each composed of fewer than 50 individuals occupying a handful
of paramo habitats in just one of the 11 discrete centers of diversity arrayed
from Colombia to Chile (Fig. 9.2; Varadarajan 1990). Relatively few lineages (e.g., P. floccosa) occur in two or more of these regions. Puya dasylirioides ranks among the more exceptional taxa as an outlier with a disjunct
range that reaches central Costa Rica. The other alpine bromeliads (more
southerly Abromeitiella, now Deuterocohnia) require further study to determine how closely their histories parallel the pattern illustrated by Puya.
Bromelia humilis: a case study of terrestrialism
Cultivated Ananas comosus excepted, the most extensive literature on the
ecophysiology of a terrestrial bromeliad concerns closely related Bromelia
humilis. This robust plant ranges through low to moderate elevation
(,1500 m), humid to semiarid habitats across the southern Caribbean,
including the Windward Islands and the ¯ oristically mature coastal communities situated along the northern rim of South America. Pittendrigh
(1948) used this heavily armed, stress-tolerant species to exemplify Type
Two, the tank-root type, in his four-part system designed to showcase the
major adaptive modes expressed among the Bromeliaceae of Trinidad
(Table 4.2).
Wet humus impounded among the shallow leaf axils of tank-root
Bromeliaceae supposedly satis® es much of the plant' s needs for moisture
and nutrients. Although Pittendrigh inferred much information about bromeliad ecology and physiology from gross form, in this instance he probably overemphasized the importance of apogeotropic roots. Foliar
trichomes located on the leaf bases of Ananas comosus exhibit ultrastructure consistent with absorptive function (Sakai and Sanford 1979), and
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401
these same appendages probably provide similar service for all of the other
Type Two species. Little to no rooting into substrates further underscores
the importance of tanks, and opportunity for sensitive species to avoid salt
on saline soils as described below.
Lee et al. (1989) investigated Bromelia humilis in alluvial plain and beach
habitats near the mouths of the Tocuyo and Tucurere rivers in northwest
Venezuela. Previously thought to be a salt-tolerant, mangrove-style landbuilder here, its distribution and generalized ecology indicate a secondary
role in community dynamics. Salt-avoidance associated with and perhaps
promoted by versatile shoot form and function foster different performances along steep gradients of exposure, fertility and salinity. Plants
extensively occupied both realized (specimens fruitful) and apparent (specimens subreproductive) niches at the study sites. Qualities manifested in
favorable ecospace suggested parallels with highly productive CAM plants
in other families (Nobel 1991). However, B. humilis failed to turn in comparable performances in Venezuela.
Bromelia humilis illustrates some noteworthy inconsistencies between
structure and function. Its unusually well-ventilated mesophyll (mean
intercellular space 9.7% vs. 2.8± 4.9% for many other CAM taxa) seems
unnecessary for a plant capable of only modest rates of photosynthesis.
Substantial succulence and high leaf area indices combined with rosulate
form further suggest equivalence with more vigorous Ananas comosus and
Agave deserti (Nobel 1991). Ecology also fails to accord with ® ndings
obtained from individual plants (e.g., Lee et al. 1989). Impenetrable thickets, created by nearly monospeci® c, con¯ uent understories of B. humilis
along the Caribbean coast below Rancho Grande, Venezuela, clearly document this sturdy xerophyte' s capacity to dominate open habitats. However,
such stands could represent many seasons of slow growth and demonstrate
the advantages of ® re-retardant foliage bearing ¯ esh-rending armature
over less protected ¯ ora rather than the results of high vigor.
Records from Venezuela demonstrate how moderate compared with full
insolation promotes growth and DH1 and elevates chlorophyll and N concentrations in B. humilis. Photoinhibition experienced by plants subjected
to high exposures required several hours to dissipate in shade, even among
individuals acclimated to full sun. Such plants had developed more
compact shoots, and possessed xeromorphic foliage well provisioned with
the xanthophyll-cycle intermediates that help prevent photodamage in
overexposed leaves (Figs. 4.24± 4.27).
Leaves subjected to unscreened irradiance also senesced sooner (one
year) than foliage produced by the deepest green specimens protected by
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Ecology
Table 7.3. Some distinguishing characteristics of the foliage of three
phenotypes of Bromelia humilis encountered in a coastal habitat in
northern Venezuela. All measurements except for pigments (season
unspecified) were recorded during the dry season
Shaded
Net CO2 uptake
22.2
(mmol m22 day21)
DH1 calculated as
173
malate (mol m23)
CO2 recycling
56.0
(as % of CO2 ® xed)
Respiration
(mmol h21 g21 fresh weight)
5.4
Succulence (kg m22)
0.98
Dry weight/fresh weight
0.186
ratio
Total chlorophyll
204.9
(mg g21 fresh weight)
Carotenoid/chlorophyll
0.31
ratio
Cell sap p (MPa)
1.14 (dawn)
1.05 (dusk)
Xylem tension (MPa)
0.54 (dawn)
0.49 (dusk)
N content (% dry weight)
0.68 (dawn)
0.62 (dusk)
Exposed green
Exposed yellow
43.4
205
7.2
160
37.6
5.6
1.21
0.186
74.0
0.46
87.0
6.2
1.18
0.219
55.8
0.91
1.17 (dawn)
1.06 (dawn)
0.86 (dusk)
0.94 (dusk)
0.59 (dawn)
0.62 (dawn)
0.47 (dusk)
0.57 (dusk)
0.08 (dawn)a
0.05 (dusk)a
Source: After Lee et al. (1989).
Note: aOne set of values for pooled green and yellow exposed plants.
taller shrubs. Individuals in full sun expressed two additional phenotypes
marked by bright yellow or light green leaves and corresponding chemical
compositions. Other symptoms of stress, including diminished CO2 consumption and greater reliance on recycled (respired) carbon rather than
carbon from the atmosphere to supply CAM, paralleled chlorosis (Table
7.3). Failure of all but an occasional sun-bleached specimen to ¯ ower or
produce a ramet demonstrated how severely overexposure depressed
® tness.
Photosynthesis inhibited by strong light that also hastens leaf turnover
denies Bromelia humilis the vigor necessary for land-building in the estuarine setting Lee et al. (1989) investigated in coastal Venezuela. Instead,
other, more proli® c, sun and possibly salt-tolerant vegetation traps most of
the sediments destined to form island basements. Presumably the bromeli-
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403
ads situated in full sun at the study sites had either grown out from under
the taller woody vegetation that dominated the islands, or arrived as
detached shoots from the same, more favorable habitat.
Rather than classing it as a pioneer, Lee et al. (1989) declared B. humilis
a subordinate species that requires shade to achieve its modest importance
in communities dominated by taller ¯ ora. Moisture and N supply, and
perhaps high temperature, but not salinity affect its vegetative vigor and
® tness. Roots supposedly avoid salt by invading the leaf axils rather than
the underlying tidal muds. Low chlorine levels in foliage indicated that rainfall either ¯ ushes the upright shoots often enough, or the trichomes and
roots exclude any contaminating sea salts.
Conditions most favorable for B. humilis at the coastal sites differ from
those conducive to higher yields from some other CAM plants. Wellwatered and fertilized, an Agave and an Opuntia species achieved Amax in
near to full sun as do numerous other desert succulents (Nobel 1991). Some
pineapple varieties also outperformed Bromelia humilis in undiminished
sunlight, proof that nothing inherent to their shared architecture or family
affiliation precludes vigorous photosynthesis. Ecotypes may account for
certain inconsistencies in the literature, for example a report that drought
more than overexposure suppressed growth in a second, nonsaline forest
site (Medina et al. 1986). However, severe climate imposes multiple stresses,
and in Venezuela complicated attempts to identify reasons for speci® c plant
performances (Chapter 4). High exposure heightens water de® cits and
raises leaf temperatures in addition to damaging the light-harvesting apparatus.
Nitrogen plays a complex and still poorly understood role in carbon
balance according to performances recorded for Bromelia humilis and
similar bromeliads, in terms of both its availability in situ and its fate following absorption. In addition to B. humilis, three Ananas species, including feral populations of A. comosus in northern Venezuela (Fetene et al.
1990; Fetene and Lüttge 1991; Medina et al. 1991b) and Panamanian
Aechmea magdalenae (P® tsch and Smith 1988), produce more N-rich
foliage capable of higher rates of net photosynthesis in shade than in full
sun (Figs. 4.5, 4.6). Medina et al. (1986) suggested that moisture-stress
exacerbated by intense insolation and infertile soil (less impoverished in
forests) accounted for the diminished yields recorded for unshaded subjects.
Instead, overexposure may assure relatively low N content in stressed
foliage, and accordingly, lower photosynthetic capacity independent of the
environmental supply. Half or more of the total N in a typical green cell
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Ecology
supports photosynthesis as a constituent of the necessary enzymes, cytochromes, pigments and coupling factors, all of which accumulate in speci® c
proportions in¯ uenced by N nutrition and exposure. Many relatives exhibit
similar tendencies to bleach (e.g., Fig. 4.26) that elevated anthocyanins
often mask in full sun. Many more Bromeliaceae than currently recognized
may respond similarly to high PPFD, possibly re¯ ecting underlying mechanisms that promote highest performance in diffuse light (Chapter 4).
Many of the data on interactions among temperature, exposure, moisture and nutrient supply as they affect bromeliad CAM come from
Venezuelan Ananas ananassoides, A. comosus and A. paraguazensis and
Bromelia humilis. Medina et al. (1991a,b, 1993), who collected much of this
information, concluded that Ananas originated in humid, lowland understory sites in northern South America where it remains most diverse.
Although fundamentally suited for understory habitats, capacity to
produce relatively drought-adapted foliage, i.e., greater xeromorphy and
increased reliance on CAM, improves performance under higher exposures, although more for some species than for others (A. ananassoides vs.
A. paraguazensis).
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Relationships with fauna
Vascular plants literally energize every major land-based ecosystem. They
also furnish co-occurring biota additional resources and services unrelated
to nutrition. Bromeliaceae stand out on this second count by providing an
extraordinary array of bene® ts to a diverse, incompletely inventoried fauna
(e.g., Figs. 8.1± 8.4) and even some ¯ ora (Fig. 8.4B). For example, many of
the phytotelm types achieve keystone status more as animal habitat than as
food (Fig. 2.4). These primarily arboreal bromeliads also lend a distinctive
visual aspect to forests throughout the Americas while they contribute
inordinately to the often exceptional biocomplexity of the same speciesrich communities (Fig. 1.4F).
Visits to bromeliads by animals to collect pollen, nectar and fruit are considered in Chapter 6; carnivory, mycorrhizae, symbiotic diazotrophs, and
certain aspects of ant-house and ant-gardened mutualisms receive due
treatment in Chapters 4 and 5. Conversely, enemies and the ants that deter
predators for many Bromeliaceae have largely gone unmentioned. Evidence
of how extensively family members serve still another set of organisms,
many of which occupy and release nutrients from litter impounded in phytotelmata, consists mostly of checklists of surveyed taxa. As we shall see,
even this preliminary literature indicates that the bromeliads in¯ uence
events in many Neotropical ecosystems far beyond what relatively small
body size and usually modest contributions to aggregate phytomass would
predict.
Predators and pathogens
No comprehensive records of herbivores or pathogens exist for
Bromeliaceae, nor does the available information suggest extraordinary
susceptibility. If anything, immunity to certain wide-ranging plant-users
405
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406
Relationships with fauna
like the leaf-cutting ants and larger grazers may be relatively well developed. Bromeliads regularly sustain damage in situ, but usually no more
than scattered necrotic spots and some chewed holes in leaves and reproductive organs (Figs. 8.1F, 8.2). Massive defoliation rarely occurs, perhaps
owing in part to the presence of strong defenses obliged by relatively unfavorable architecture. Because bromeliads are essentially stemless plants
with even less opportunity to store reserves in often vestigial root systems,
severe herbivory probably compromises regenerative capacity more for
them than for most woody plants and many other herbs.
Scattered reports indicate that Bromeliaceae possess potential chemical
deterrents, and may be exceptionally well provisioned with these compounds. Chedier and Kaplan (1996) demonstrated seasonal, perhaps
drought-related, ¯ uctuations in the amounts of waxes, condensed tannins,
and total phenols present in the foliage of Nidularium procerum, N. innocentii and Quesnelia quesneliana. Triterpenoids and steroids occur in
Florida Spanish moss (Atallah and Nicholas 1971) and several other tillandsias (Arslanian et al. 1986). Hegnauer (1963) reported a steroid fraction with oestrogenous activity in the cuticles of several Tillandsioideae.
Williams (1978) encountered ¯ avonoids in uncommon variety, but mostly
of unknown signi® cance, distributed among species representing all three
subfamilies (Chapter 9).
Sclerophylly, trichomes and succulence probably also reduce the palatability and nutritional quality of much bromeliad foliage compared with
nearby, often shorter-lived, softer forage, for example the trees hosting the
epiphytes. On the other hand, certain bromeliads attract devastating attention from animals immune to most counter-measures. Large carnivores,
and particularly primates seeking prey in overlapping leaf bases of the phytotelm types, in¯ ict damage that neither chemicals nor most of the mechanical impediments available to the bromeliads can discourage.
What can be said at this time about predation pressure on Bromeliaceae
vs. other ¯ ora? Annual rates of leaf consumption for a variety of kinds of
tropical evergreen forests range into the low double digits. Now and then,
a few trees experience losses equivalent to most of their canopy (Lowman
1995). The same observer and others (Lowman et al. 1996) reported depredations caused by an unseen dietary specialist ± up to 25% (mean leaf area
missing 10.4%) ± of the foliage of a small colony of Peruvian Aechmea
nallyi. Only once have I witnessed a more severe event. On that occasion,
an unusually abundant grasshopper had grazed at least 25% of the leaf area
serving the adults of a Guzmania monostachia population located in the
lower canopy of a swamp forest in southern Florida. Two years later new
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Predators and pathogens
407
Figure 8.1. Associations between ants and termites and Bromeliaceae. (A)
Lithophytic Aechmea phanerophlebia in Minas Gerais State, Brazil with an associated termite trail (arrow). (B) Aechmea bracteata in Yucatán State, Mexico with a
termite carton partially exposed on the shoot (arrow). (C) Ant-nest garden dominated by Aechmea angustifolia in Ecuador. Lower portion cut open to expose abundance of roots. (D) Shoot of Aechmea phanerophlebia in Minas Gerais State, Brazil
cut open to reveal ant carton. (E) Lithophytic Encholirium sp. in Minas Gerais State,
Brazil associated with termite carton. (F) Colony of lithophytic Aechmea phanerophlebia in Minas Gerais State, Brazil showing insect damage despite the ants that
inhabit most shoots. (G) Dyckia specimen uprooted in Minas Gerais State, Brazil
to expose a cluster of associated termites (arrow).
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Relationships with fauna
ramets had fully restored the colony to its usual condition. Several additional bromeliads may be exceptionally susceptible to herbivory, for
example wide-ranging Aechmea bromeliifolia in Bahia and Minas Gerais
states in southeastern Brazil (personal observation).
Equally severe events sometimes impact reproductive organs, but how
often remains unclear and difficult to determine because damage to seeds
is often cryptic. Garcia-Franco and Rico-Gray (1991) reported heavy predation on the in¯ orescences of Tillandsia deppeana in a deciduous forest
near Xalapa, Vera Cruz, Mexico, enough to preclude seed production by
some individuals. Elsewhere, capsules of tillandsias often exhibit little or no
insect damage (e.g., T. balbisiana in southern Florida; personal observation).
Unlike those voracious orthopterans in Florida, many of the invertebrate fauna that attack Bromeliaceae are relatively oligophagous, some
exclusive to a few genera and occasionally a single species. Documentation
includes the specialized behavior of Dynastor napolean, a butter¯ y native
to southeastern Brazil. Larvae neatly trim and roll up the tip of each partially eaten leaf as if to confuse its own searching predators. A moth combines bromeliad tissue in an otherwise unexpected diet. The usually solitary
Castine phalanis that survives its cannibalistic brood mates bores into the
center of the hosting shoot, ultimately destroying it.
Strymon basilides, another lepidopteran, feeds on developing bromeliad
¯ owers and fruits, sometimes in sufficient numbers to abort the entire in¯ orescence and occasionally challenge pineapple culture in Brazil.
Beutelspacher (1972) and DeVries (1997) cite a variety of Tillandsioideae
as hosts for the larvae of Riodinidae butter¯ ies (see also Chapter 12).
Figure 8.2B illustrates the characteristic burrows of a leaf miner exclusive
to the leaves of Aechmea bromeliifolia and an unidenti® ed Hohenbergia in
southern Bahia State, Brazil in December 1996 (personal observation).
Stranger still, the crab Metasesarma rubripes crops the ¯ owers of several
bromeliads in some coastal habitats in southeastern Brazil (Fischer et al.
1997).
Less conspicuous invertebrates also attack Bromeliaceae. Members of
the symphylid genus Hanseniella cause problems for pineapple farmers in
northern Australia (Paroz 1981). Symptoms include a characteristic
witches' broom-type branching following destruction of the root tip. Many
of the standard greenhouse-inhabiting Homoptera thrive on a variety of
bromeliads, and a constellation of scale insects (e.g., Diaspis bromeliae,
Hemiberlesia palmae, Saissetta hemisphaerica), and mealy bugs (e.g.,
Pseudococcus brevipes, Rhizoecus falcifer) can kill untreated specimens. The
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409
Figure 8.2. Herbivores and Bromeliaceae. (A) Bromelia sp. in Minas Gerais State,
Brazil showing the impact of an unidenti® ed trichome-grazer. (B) Characteristic
damage caused by a leaf miner on Hohenbergia sp. in Bahia State, Brazil. (C) Insect
damage to spikelets of an unidenti® ed Hohenbergia sp. in Bahia State, Brazil. (D)
Aphids on the buds of a cultivated Dyckia sp. (E) Extra¯ oral nectar on the calyx of
the same Dyckia sp. featured in D.
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Relationships with fauna
Table 8.1. Partial list of pests that were not currently present or widely
distributed in the United States intercepted on imported bromeliads by the
United States Department of Agriculture Plant Quarantine Division
inspectors during 1965–67
Plant pest
Acutaspis tingi McKenzie
Acutaspis umbonifera (Newstead)
Arphnus melanotylus Ashlock
Asterolecanium epidendri (Bouche)
Atta mexicana (F. Smith)
Cimolus vitticeps Stal
Crophinus costatus (Distant)
Dendrocoris variegatus Nelson
Diabrotica porracea Harold
Dysdercus mimulus Hussey
Dysmicoccus probrevipes (Morrison)
Exptochiomera albomaculata (Distant)
Helicina zephyrina Duclos
Melanaspis odontoglossi (Cockerell)
Metamasius hemipterus hemipterus
(Linnaeus)
Metriona trisignata Boheman
Mimosestes dominicanus (Jekel)
Mormidea collaris Dallas
Ochrimnus vittiscutis (Stal)
Ogdoecosta biannularis (Boheman)
Oplomus rutilus Dallas
Paroecantus aztecus Saussure
Procyrta intectus (Fowler)
Statira denticulata Champion
Tnethecoris distinctus Hsiao & Sailer
Xenochalepus omogerus (Crotch)
Family
Country of origin
Diaspididae
Diaspididae
Lygaeidae
Coccidae
Formicidae
Coreidae
Lygaeidae
Pentatomidae
Chrysomelidae
Pyrrhocoridae
Pseudococcida
Lygaeidae
Helicinidae
Diaspididae
Curculionidae
Mexico
El Salvador
Honduras
Costa Rica
Colombia
Mexico
Mexico
Mexico
Honduras
Mexico
Mexico
Mexico
Mexico
Jamaica
Jamaica
Chrysomelidae
Bruchidae
Pentatomidae
Lygaeidae
Chrysomelidae
Pentatomidae
Gryllidae
Membracidae
Lagriidae
Miridae
Chrysomelidae
Guatemala
Mexico
Mexico
Guatemala
Mexico
Honduras
Mexico
Guatemala
Honduras
Mexico
Honduras
Source: From Davidson (1969).
nematode Tylenchocriconema alleni uses its piercing proboscis to feed on
the mesophyll of young leaves while sheltered in the phytotelmata of
Tillandsia flabellata (Lehman 1987). A mollusk apparently favors the trichome shields that densely invest the abaxial surfaces of the foliage of an
unidenti® ed Bromelia in Minas Gerais State, Brazil (Fig. 8.2A). A more
nitrogen-de® cient forage is hard to imagine.
On balance, patterns of predation indicate diverse fauna, and preferences for speci® c organs and tissues in addition to narrow host ranges.
Table 8.1 lists some known pests recorded on imported specimens; Table 8.2
itemizes tank inhabitants, many of which cannot be bromeliad feeders,
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Predators and pathogens
Table 8.2. Invertebrate taxa present in the tanks of bromeliads and on the
forest floor at Rancho Grande, Venezuela
Acari, Mesostigmata
Acari, Orbatei
Acari, Prostigmata
Acari, Trombidiidae
Araneida
Blattodea
Carabidae
Carabidae, larvae
Catopidae
Chelonethida
Chilopoda
Coccinellidae
Coleoptera, phytophagous larvae
Collembola
Curculionidae
Dascyllidae, adults
Dascyllidae, larvae
Dermaptera
Diplopoda
Diplura, Campodeidae
Diplura, Japygidae
Diptera Brachycera larvae
Diptera, Drosophilidae
Diptera, Nematocera larvae
Dytiscidae, larvae
Enchytraeidae
Formicidae
Gastropoda
Glossoscolecidae
Glossoscolecidae, cocoons
Gryllidae
Hemiptera
Hirudinea
Histeridae
Liodidae
Lucanidae
Nitidulidae
Oniscoidea
Pedipalpida
Phalangida
Pselaphidae
Psocoptera
Ptilidae
Scydmaenidae
Staphylinidae
Symphyla
Bromeliad
Forest ¯ oor
4
0
0
0
12
15
4
0
0
0
13
2
3
2
0
0
66
0
68
0
0
1
0
37
1
0
456
2
12
14
1
29
4
0
0
0
0
57
0
1
2
0
3
0
5
0
7
4
2
1
17
4
1
1
5
7
24
0
10
2
1
1
0
3
46
3
6
4
2
1
0
2
64
1
0
2
2
8
0
2
4
1
1
32
2
3
23
1
1
15
26
11
Source: From M. C. Paoletti, personal communication; see also Paoletti et al.
(1991).
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412
Relationships with fauna
recorded in situ. One migrant that fails to show up on the ® rst list warrants
special note.
A predator from Mexico is raising serious concern in Florida (Frank and
Thomas 1994). Initial sightings occurred in Broward County in 1989, but
USDA inspection records suggest that Metamasium callizona (Coleoptera)
arrived at least a decade earlier, presumably aboard a shipment of horticultural stock from Mexico. Additional members of this weevil genus feed on
Ananas and other bromeliads in tropical America, whereas more oligophagous M. callizona exhibits greater partiality for Tillandsia, particularly T.
utriculata in the state of Vera Cruz, its type locality. The same behavior is
expressed in the newly established population, and densities of affected T.
utriculata in some parts of Florida now exceed those Frank recorded in
Mexico.
Gravid females chose relatively mature shoots equipped with a caudex at
least 2 cm in diameter. Younger specimens are either too small to provide
sufficient food, or they fail to protect the developing larvae. Small species
may be wholly ignored for the same reason, but not so large specimens of
Catopsis and Guzmania that have already come under attack in Florida
(Frank and Thomas 1994). Slits made in the leaf bases prepare the host for
egg-laying. Larvae require 8± 10 weeks to feed, after which pupation occurs
over 18± 24 additional days. Florida' s strictly monocarpic T. utriculata may
fare worse than its counterpart in Mexico where longer contact with this
insect may account in part for the regular production of ramets (see
Chapter 7 for additional reasons). In fact, infestations of T. utriculata and
T. fasciculata had become severe enough by 1996 to prompt listings among
Florida' s official endangered ¯ ora.
Metamasium callizona continues to spread into central and southwestern
Florida. As of September 1996, con® rmed reports included 10 counties.
Although members of at least 12 more genera can be infected (Frank and
Thomas 1994), collections of cultivated Bromeliaceae have so far remained
mostly beetle-free, sometimes even where nearby trees host native
Tillandsia utriculata harboring con® rmed infestations. Attempts are underway to introduce a parasitoid of Metamasium callizona to Florida. An
undescribed Admontia sp. (Diptera) looks promising, but so far has proven
difficult to rear in sufficient numbers to conduct the federally mandated,
pre-release determination of its host range (Cave 1997).
Bromeliads also support a number of dis® guring, usually sublethal, rusts
(Lineham 1987) and additional, potentially devastating fungi. Commercial
growers rely on spray programs that incorporate broad-spectrum fungicides to head off additional problems. For example, Puccinia tillandsiae
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Predators and pathogens
413
grows on Tillandsia punctulata, and this same microbe parasitizes at least
three relatives in Florida and Mexico. Puccinia pitcairniae attacks two and
maybe more Pitcairnia species, and Uredo nidulaari infects Nidularium longiflorum. Helminthosporium rostratum acts as a leaf pathogen on Aechmea
fasciata (Marlatt and Krauss 1974), which is the most widely marketed of
the ornamental bromeliads. Phytophthora causes sufficient heart rot to
require chemical control in some pineapple plantations.
Anthropogenic in¯ uences may be intensifying certain natural challenges
to some wild populations. Fusarium infects a number of bromeliads, including pineapple, and the same or another member of this genus may have contributed to the massive die-off of Tillandsia usneoides through much of
central Florida during the early 1970s. Air pollution is probably slowing
recovery in parts of that state, and could be contributing to on-going
declines elsewhere (e.g., New Orleans area). Effluents from the large concentration of petrochemical facilities, possibly exacerbated by microbes
and other agencies, may explain the almost total extirpation of Spanish
moss to the west along the Gulf coast and north into the Big Thicket
National Preserve (Chapter 5).
Bromeliad viruses other than those that oblige meristeming to obtain
uninfected pineapple stock receive no mention in technical print.
Undoubtedly, many more, if not all, Bromeliaceae host these agents, but so
far horticulturists seem mostly unconcerned. A rather lively and still unresolved debate (e.g., Mason 1976) once swirled around the presumed viral
involvement in some of the more common leaf variegations, particularly
the longitudinal striping that accounts for the popularity of numerous cultigens (e.g., Aechmea fasciata), and occurs sporadically through populations of certain wild types (e.g., Guzmania monostachia in Florida).
Alternating horizontal bands of lighter and more deeply chlorophyllous
tissue (e.g., Vriesea fosteriana, V. hieroglyphica) comprise another category
of leaf ornamentations (Figs. 2.14G, 2.17B). These stable patterns may
promote plant bene® ts by enhancing the hospitality of phytotelmata, and
accordingly, the effectiveness of phytotelm architecture for plant nutrition,
although other services are possible (Chapter 4). Less regularly distributed
spots of variable dimensions and colors elsewhere (e.g., many Billbergia
species; Fig. 2.14H) more closely resemble viral lesions. Small patches of
chlorotic tissue on Billbergia lietzei and B. saundersii foliage, among other
taxa, sometimes become suggestively necrotic.
Undoubtedly, the enemies of the bromeliads far exceed those mentioned
in this brief account. Today, we know too little about this subject to even
attempt to address broad questions such as relative vulnerabilities to
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Relationships with fauna
different kinds of pathogens and herbivores, and the nature and
effectiveness of the corresponding plant defenses. A better test of the
uniqueness of Bromeliaceae relative to use by predators and pathogens
requires comparisons with other families (e.g., Agavaceae) of monocots
that share similar habits and propensities for stressful habitats.
Mutualisms
Bromeliad-users beyond the herbivores and pathogens differ in degrees of
dependence and the kinds of bene® ts received from and provided to their
hosts. Most intimate are those fauna obliged to spend at least part of their
life cycle associated with Bromeliaceae, sometimes speci® c taxa. A second,
less dependent type need bromeliads for shelter or to feed, but not to reproduce. Still less plant-dependent are the facultative users. If aquatic, these
organisms also inhabit phytotelmata provided by other vegetation; if birds
they can nest elsewhere. Least bromeliad-dependent are the casual visitors,
a group that includes the pollinators and seed dispersers, all of which forage
for the same products and services across broad ¯ oras. We begin with the
mammals and work down the phylogenetic scale to the exceptionally
important ants and ® nally the litter-processing communities that develop
in bromeliad phytotelmata.
Mammals
Several monkeys, marmosets and tamarinds regularly dismember vegetation to locate food in forest canopies. Several epiphytic Bromeliaceae are
important enough for these animals to warrant special consideration in
rescue efforts. For example, Leontopithecus rosalia, the golden lion tamarind of Brazil' s Atlantic coast forest, forages widely among the local phytotelm species to support its omnivorous diet. Several arboreal relatives
also possess exceptionally long ® ngers, adapted perhaps to provide unusual
access to desirable articles positioned among tightly overlapping leaf bases
(E. Leme, personal communication).
Cages provisioned with bromeliads collected from the same forests set
aside as preserves in Rio de Janeiro State help condition reared animals for
successful foraging following release (personal observation). Callithrix
geoffroyi, the white-faced marmoset, uses Bromeliaceae in much the same
way in Espirito Santo State (Leme and Marigo 1993). Other mammals that
help regulate populations by eating the meristematic center of the shoot
and dispersing seeds of the bromelioids include tree opossums and squir-
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Mutualisms
415
rels, and other arboreal rodents (e.g., Fischer and Araujo 1995; Fig. 6.6).
Freeze and Oppenheimer (1981) report that a number of monkeys feed on
young in¯ orescences and destroy plants by eating the center of the shoot.
Birds
Nadkarni and Matelson (1989) recorded close ties between avifauna at
Monteverde, Costa Rica and arboreal ¯ ora in both primary lower montane
cloud forest and the epiphytes inhabiting the isolated trees left standing in
cleared pastures. Bromeliaceae received more visits than even co-occurring
Ericaceae, Gesneriaceae, Loranthaceae and Marcgraviaceae, which also
offered especially attractive nectar or fruit, but fewer reasons overall for
birds to spend time there. Bryophytes stood out as well, providing nesting
material, and, judging by bird behavior, food, presumably sheltered invertebrates.
Overall, 15% of the visits to tree crowns by 81 bird taxa recorded during
289 h of observations involved some type of epiphyte use. Perching
occurred in 67% of all the encounters with canopy ¯ ora; feeding in 48%;
vocalizing in 22%; and the gathering of nest materials, drinking and
bathing in 2%. Nine bird species, including hummingbirds, ¯ ycatchers and
the common bush tanager, paid some attention to epiphytes, often bromeliads, during more than half of their time in the canopy. Those users that
showed the greatest interest rarely or never visited isolated trees despite the
usually dense colonies of resident epiphytes high light favors on such supports (Fig. 1.4F). Birds with broader foraging patterns appeared about as
often in dense forest as in degraded habitat.
Sillett (1994) looked more closely at epiphyte use by eight insectivorous
birds at a series of Costa Rican sites located between 2800 and 3100 m in
the Cordillera de Talamanca. Tree crowns at these altitudes support the
heavy loads of bryophytes characteristic of upper montane wet tropical
forests, while phytotelm Tillandsioideae constitute most of the less abundant local vascular epiphytes. Feeding behaviors among the eight subjects
varied along a continuum, with some species tied to a speci® c kind of substrate and others to certain prey that by distribution obliged wider
searches through the canopy. All of these birds spent at least one-third of
their time seeking food among the epiphytes, two (Margarornis rubiginosus, Pseudocolaptes lawrencii) more so than the others. Pseudocolaptes lawrencii devoted 74% of its time during Sillett' s observations to tank
bromeliads, moving from plant to plant pulling out and tossing aside
impounded debris to expose cockroaches and other invertebrates.
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Relationships with fauna
Troglodytes ochraceus alone worked the humus around the bases of these
plants (37% of observations).
Pizo (1994) surveyed the associations between birds and arboreal
Bromeliaceae during several visits to Atlantic Forest at 600± 850 m in the
Paranapiacaba mountains of São Paulo State, Brazil. Twenty-three species
provided one or more kinds of resources, many identical to those Nadkarni
and Matelson enumerated in Costa Rica, but selectivity often changed with
the location. Eight birds foraged only through the understory (,10 m), six
others consistently remained above this zone (10± 25 m), and 10 less fastidious species utilized Bromeliaceae throughout the forest. Cacicus haemorrhous (the red-rumped cacique) and Platypsaris rufus constructed nests
largely of Tillandsia usneoides, while Thraupis cyanoptera and T. ornata
used a variety of materials to raise young exclusively in the space located
between a phytotelm shoot and the adjacent tree trunk. Epiphytes belonging to other families provided lesser services and accounted for fewer bird
visits. Remsen (1985) also indicated that bromeliads are inordinately
important to the organization of bird communities in the high forest of
Bolivia.
Brazilian Rhopornis ardesiaca may be the most plant-dependent of the
birds observed using bromeliads so far (Leme and Marigo 1993). Large
clumps of terrestrials that harbor abundant arthropods and provide favorable nesting sites accounted for most of its time in the liana forests of the
southern part of Bahia State. Geranospiza caevulescens, the crane hawk,
owes its common name to an extraordinary anatomical feature that facilitates bromeliad use (Bokermann 1978). This bird ranges from Mexico to
Argentina aided in its searches for frogs and other tank fauna by long legs
equipped with exceptionally mobile tarsal joints.
Bromeliads sometimes belong to mixed assemblages of plants that share
the same pollinators. Stiles (1978) described the phenology over four years
of such a guild of ornithophilous plants in lowland humid forest at Finca
La Selva, Costa Rica (Fig. 6.3). More than 40 participating taxa ¯ owered
more or less sequentially to produce a near continuous supply of nectar for
the local hummingbirds. Such arrangements could be coincidental, evolved
in situ via character displacement, or established by ecological sortings of
suitable genotypes among those already available (Chapter 6).
Some of the bromeliads responded to weather in a way that promoted
the welfare of local pollinators during drought. Rather than producing less
nectar during the driest of the four years like the rest of the guild, Aechmea
nudicaulis ¯ owered more profusely. In effect, the more stress-tolerant, if
not stress-stimulated, taxa together maintained a relatively perturbation-
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417
Figure 8.3. Syncope antenori, a tadpole of a bromeliad-adapted frog from Peru
(redrawn from Krügel and Richter 1995).
resistant food source capable of sustaining a needed population of resident
pollinators. Fischer and Araujo (1995) describe arrangements in coastal
Brazil where sympatric Bromelioideae offer ripe fruit according to schedules that manipulate fauna to disperse seeds (Fig. 6.6).
Anurans
Plant-compatible morphology and reproductive strategy characterize the
more bromeliad-dependent vertebrates and invertebrates. Bromeliocolous
anurans conform by exhibiting one of two patterns: they produce either
sedentary or free-swimming larvae. Gastrotheca fissipes incubates young on
its back until legs develop. Tadpoles of several of the free-foraging species
exhibit exceptionally slender bodies to negotiate the cramped quarters
imposed by closely overlapped leaf bases (Rivero 1984, 1989). Other shapes
exist to counter the effects of stagnation and limited food supplies. Larvae
of Jamaican Hyla brunnea feature laterally narrow tails compared with
nonbromeliocolous relatives, purportedly to encourage gas exchange in
media largely stripped of oxygen by the decaying remains of its egg masses
(Nobel 1929; Fig. 8.3). Vestigial mouths and guts accompany dependence
on vitelli in lieu of feeding. Reproductive efforts and nursery volumes
match, with fewer than 20 eggs per clutch in the more extreme species.
Breeding space provided by Bromeliaceae varies in importance with the
location. Fully seven of Puerto Rico' s 18 natives regularly use one or more
phytotelm species to reproduce. Three members of Eleuthrodactylus,
including E. jasperi, which is just 20 mm long and the only live-bearer in
the western hemisphere, exhibit complete plant dependence. Billbergia
zebrina of Brazil' s cerrado, and a less frequent epiphyte or lithophyte elsewhere, provides unusually favorable shelter for Hyla venulosa. Sticky latexlike secretions from its head allow this animal to block off the narrow
phytotelma and further frustrate pursuers and avoid desiccation during the
dry season.
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Aparasphenodon brunoi and similar frogs employ a bony cranial carapace
to put a variety of Brazilian Bromeliaceae to similar use. Protruding eyes
retract into the oral cavity when danger threatens. Figure 8.4E,F illustrates
a mature specimen of one of these animals resting in the central tank of an
unidenti® ed Hohenbergia in Bahia State. Removed and placed on one of
the leaf blades, this frog exhibited remarkable strength in its unusually
short limbs while repeatedly trying to crawl back to its original refuge
rather than jump on to nearby vegetation.
The Costa Rican `poison arrow frog' Dendrobates pumilio demonstrates
one of the most elaborate behaviors recorded for a bromeliad-user (Young
1979). Although terrestrial most of its life, this brilliantly colored animal
relies on exceptionally complex behavior and impressive powers of navigation to reproduce exclusively in the phytotelmata of epiphytic
Bromeliaceae. One by one, tadpoles hatched on the ground dutifully climb
aboard their mother' s back for carriage to one of a series of nursery plants.
Each deposit consists of a single larva and an unfertilized egg provided as
food. Rearing involves repeated visits to the same leaf axils and additional
sacri® cial eggs. The mother' s persistence is exceeded only by her uncanny
ability to relocate each developing offspring.
Peixoto (1977) documented visits by and breeding strategies of 26 hylid
species representing eight genera in Atlantic Forest. Some patterns of
reproduction (e.g., Gastrotheca fissilis) accord with constraints imposed by
small volumes of water at breeding sites. Life cycles in other cases incorporate longer juvenile stages and corresponding requirements for extensive
foraging and larger phytotelmata. Larval characteristics beyond the outsized tails that aid gas exchange include a depressed body, unusual dentition, and the absence of papillae on the anterior part of the upper lip.
An undetermined number of frogs center their entire existence on
Bromeliaceae, and at least a few of them remain faithful to a single plant
(Abendroth 1971). Fritziana goeldii routinely breeds in Aechmea and
Billbergia shoots in the Organ mountains of southeastern Brazil, where its
larvae require just a few days to develop limbs. Tubular types (e.g., Aechmea
nudicaulis, Billbergia vittata) rather than species with more spreading,
shallow shoots (e.g., many local Vriesea species) attract the heaviest use.
Several adults may spend the entire day virtually motionless in as many leaf
axils in the same shoot. Each evening they depart to forage through the surrounding canopy. Less is known about the lizards (e.g., Abronia) and
snakes (e.g., Bothrops schlegeli) that often visit bromeliads. None of these
reptiles appears to be modi® ed for bromeliad use, nor do they spend as
much time there as the more desiccation-prone amphibians.
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Mutualisms
419
Figure 8.4. Biota in bromeliad tanks. (A) Unidenti® ed frog hiding by day in the leaf
base of an unidenti® ed Billbergia sp. in Rio de Janeiro State, Brazil. (B) Trapbearing rhizomes of Utricularia humboldtii in the tank of Brocchinia tatei on Cerro
Neblina, Venezuela. (C) Damsel¯ y recently emerged from the phytotelmata of an
unidenti® ed Aechmea sp. in Espirito Santo State, Brazil. (D) Method used to
remove the biota residing in the phytotelmata of Bromeliaceae. (E) Unidenti® ed
frog in Bahia State, Brazil using its bony cranial plate to block off the central tank
of an unidenti® ed Hohenbergia sp. specimen. (F) The same frog featured in E.
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Relationships with fauna
Salamanders
Some salamanders rival the bromeliocolous frogs for dependence on phytotelmata, and here too plant shape matches the body form and reproductive biology of the animal. In fact, Bromeliaceae appear to have played a
decisive role in the history of this group of unusually drought-vulnerable
vertebrates. Distributions leave little doubt that bromeliad-provided cavities ® lled with moist, decomposing debris and abundant invertebrates
helped this fundamentally Laurasian group make its single substantial
incursion into the tropics (Wake 1987). About 80% of the more than 140
species in 11 genera of plethodontids occur in Mesoamerica and northwest
South America where many of these animals remain con® ned with their
supporting montane bromeliads to narrow altitudinal ranges.
Diversity peaks in mid-elevation (750± 2500 m) cloud forest, most
notably in Costa Rica. One transect extending from near sea level to 4000
m in southern Mexico yielded 15, mostly discrete, salamander populations,
many exclusive to large Tillandsia and Vriesea shoots. Plethodontidae
equipped to utilize Bromeliaceae differ from their more northerly counterparts by direct development (no larval stage) and exceptional drought-tolerance, in addition to the narrower distributions.
Salamanders most often reported in bromeliad shoots belong to
Dendrotriton, Nototriton and Chiropterotriton. Behaviors and life cycles
distinguish these animals from those adapted to other substrates, but
perhaps somewhat less so than some of the frogs. Nevertheless, shapes
appropriate for negotiating the narrow spaces between overlapping leaf
bases stand out at a glance. Adults typically possess small (,50 mm in
length) trunks equipped with long prehensile tails, elongate limbs with
widely separated digits, and frontally directed eyes.
Phylogenetic studies indicate substantial homoplasy in those features
associated with bromeliad use, possibly related to a limited number of
niches for these animals in tropical America. Relatives that prefer
suspended mats of mosses, higher plants with other shapes, and debris
instead of phytotelma possess shorter appendages and trunks similar to
those of the land-based forms. Little is known about the behavior and
mobility of the bromeliad-dependent species. Gregariousness increases
during dry weather; on one occasion up to 34 Dendrotriton xolocalcae specimens occupied a single bromeliad (Wake 1987). As many as one in two of
the larger shoots sampled housed at least one salamander.
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421
Invertebrates
Bromeliaceae probably ranks highest in importance among the nonwoody
families that promote the welfare of canopy-based fauna in tropical
America, if only because so many of its members provide such extensive
shelter from predators, drought, wind and torrential rains. Arboreal bromeliads also elevate carrying capacities simply by humidifying the canopy
atmosphere and expanding and elaborating its surface (i.e., increasing its
`fractile universe' ). Numbers of individuals and biomass identify the invertebrates as the major bene® ciaries. Phytotelm bromeliads, among other
suspended ¯ ora, and the humus they impound promote conditions so
broadly equable that earthworms and diverse other desiccation-prone soil
fauna sometimes ascend trunks to visit or, if capable of reproducing there,
to permanently reside above ground.
In effect, soil-dwelling invertebrates representing numerous phyla, along
with their often closely related, exclusively arboreal counterparts, utilize
substantial portions of the forest canopy as an extension of what temperate biologists tend to consider habitat con® ned to the ground. Of all of
these animals, the ants, owing to their abundance, social organization and
diverse activities and diets, in¯ uence the greatest variety of events above
and below the soil surface. Not surprisingly, more is known about the associations of these insects with bromeliads than about any of the many other
relationships except those involving mosquitoes.
Ants and bromeliads
Bromeliads that encourage prolonged contact with useful invertebrates fall
into four nonexclusive categories, the ® rst three of which involve ants.
Participating plants can be considered ant-guarded, ant-gardened, antfed/ant-house providers, or the phytotelm types. Relationships of the
second and possibly the third kinds also promote plant dispersal. A few
preliminary remarks about ant biology prior to, and some additional comments after, describing these interactions will help explain why Formicidae
alone among the insects engage in so many kinds of mutualistic, nonpollination relationships with Bromeliaceae.
Eusociality and often broad diets grant the ants unparalleled ecological
versatility and propensities to interact with vegetation in complex and
diverse ways. Some of these partnerships exhibit sufficient intimacy to
suggest coevolution. Arboreal ants native to the lowland humid forests
of tropical America achieve remarkable densities despite possession of
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powerful, piercing mandibles, high mobility (and accompanying energy
requirements), and additional indications that prey rather than plant products constitute the primary nutritional base. Sometimes, ant abundance
simply becomes too high and the masses of their bodies too great to impute
strict carnivorous diets. In fact, vegetation, including many of the bromeliads, and diverse Formicidae associate more closely in some food webs than
either mouth parts, behavior or trophic pyramids would predict, and for
two reasons.
Ants that farm Homoptera (Fig. 8.2D) do so to access phloem sap which
is one of the richest and most easily digested of the edible plant products.
While these arrangements can impose signi® cant burdens on supporting
¯ ora, net bene® t accrues to the host if the ants tending its aphids or scale
insects also deter enough additional, more voracious herbivores. Many
woody ¯ ora and some Bromeliaceae utilize similarly pugnacious, but less
destructive, guards with rewards of extra¯ oral nectar or solid food on
stems, leaves and developing ¯ owers and fruits (Fig. 8.2E). Less common,
but no less revealing of the value ants represent as plant resources, are the
myrmecodomatia produced to encourage nesting by potential defenders,
and for the epiphytes, surrogates for diminished root systems (Fig. 8.5).
Ant-guarded species
A signi® cant number of the diverse epiphytic ¯ ora that routinely root in ant
cartons produce extra¯ oral nectar or pearl bodies (lipid-rich, particulate
food). However, no reports (e.g., Madison 1979) that describe these rewards
mention a bromeliad, although important products may be seasonal and so
far overlooked. Ants densely covered the young in¯ orescence of Aechmea
angustifolia specimens that dominated large nests at Rio Palenque,
Ecuador, but I was unable to get close enough during the brief opportunity
to determine why. Some terrestrial, nonmyrmecophytic bromeliads de® nitely protect vulnerable organs with seasonally provided ant food elaborated speci® cally for that purpose.
Galetto and Bernardello (1992) examined 20 Argentinian bromeliads in
two genera and discovered that nearly half, speci® cally eight Dyckia species
and a Deuterocohnia, attract ants with secretions vented on the abaxial surfaces of the sepals. Sugar was abundant, but contrary to most extra¯ oral
nectars a single constituent, in this case sucrose, accounted for .97% of the
total. Relatively high concentrations of amino acids (121± 975 mg ml21)
accorded more with ant guards than pollinators as the targeted fauna.
Nectaries in all nine cases belonged to the `formless' type and secreted
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Ants and bromeliads
423
Figure 8.5. Four species of Tillandsia offering different amounts of space for nesting
ants in the Sian Ka' an Biosphere Reserve (Quintana Roo State, Mexico). Section
indicates how much of the lower shoot is available for occupancy. Percent values
indicate frequencies that sampled plants housed ant colonies (after Dejean et al.
1995).
sugary product through adjacent stomata rather than through special ducts
like those featured in their much more elaborate and productive counterparts located in the gynoecial septa (Fig. 3.4I). Organs occurred more or
less randomly, with one to ® ve droplets appearing on a single perianth
member (Fig. 8.2E). Broader surveys will almost certainly reveal additional
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Relationships with fauna
ant-guarded relatives with similar arrangements. Koptur' s (1992) discovery
of ants feeding on nectar presented on the primary bracts of an immature
in¯ orescence of Tillandsia balbisiana in south Florida may document a pervasive phenomenon.
Ant-nest garden species
Descriptions of the gardens cultivated by carton-constructing ants appear
elsewhere in this volume with regard to establishment, succession, plant
nutrition and reproduction (Chapters 5 and 6; Fig. 8.1C). Nest-garden
Bromeliaceae mostly belong to Bromelioideae, with just an occasional,
possibly accidental, tillandsioid listed in enumerations of the plants that
engage in these mutualisms. Werauhia gladioliflora roots in carton in southeastern Ecuador now and then (H. Luther, personal communication) as
does Tillandsia fasciculata in Belize (Catling 1995).
Features of the participating ants and the plants may militate against
nest-garden status for members of Tillandsioideae. Dry fruits and plumose
seeds generally offer no incentives for myrmecochory, although cartonassociated Dischidia species (Asclepiadaceae) prove that wind and ant carriage sometimes occur sequentially in the Old World tropics (Benzing
1990). Shoots that exceed roots as absorptive organs probably further predisposed Tillandsioideae to ant-house over ant-garden mutualisms.
Warm, humid forests composed of many small trees on fertile soil
support the highest densities of Neotropical nest gardens. For example, 34
discrete cartons, each sustaining a sizable ¯ ora tended by thousands of
ants, occurred on a single 10 310 m plot in an Amazonian caatinga
(Madison 1979), many inhabited by Aechmea mertensii, A. brevicollis and
A. longifolius. Aechmea angustifolia predominates among ant-cultivated
bromeliads at Rio Palenque, Ecuador (Fig. 8.1C); Aechmea tillandsioides
var. kienastii achieves comparable status in parts of Central America and
in Trinidad (Pittendrigh 1948; Catling 1995, 1997). Aechmea tillandsioides
warrants special mention for its exceptional attractiveness to ants even in
the greenhouse. Interest in its infructescence, perhaps primarily as a site for
farmed Homoptera, sometimes culminates in the production of protective
cartons that cover many of the junctions between adjacent ¯ oral bracts
(Rivero and Barard 1983).
Pittendrigh noted in his classic study of bromeliad ecology (Pittendrigh
1948) that Citrus trees in a northern Trinidad grove each supported 3± 10
discrete ant-nest gardens, many occupied by Aechmea mertensii. Ant-nest
gardens associated with a discrete colony, or fragments of larger, polygy-
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Ants and bromeliads
425
nous populations of Camponotus femoratus, occurred on 16± 39% of the
trees in ® ve Peruvian sites supporting different kinds of forest (Davidson
1988). Highest densities characterized seasonally ¯ ooded, open communities. Exposed microsites receive the greatest attention from ants either
because the host trees there produce relatively abundant ant food ± a possibility explored more fully below (Kleinfeldt 1978; Davidson and Epstein
1989) ± or because the ants avoid locations too wet or cool to raise their
brood.
Nest-garden builders include members of Anochetus, Azteca,
Camponotus, Crematogaster and Dolichoderus. All of these ants probably
consume substantial honeydew to obtain the energy needed to construct
extensive cartons. Even so, nest occupancy is often shared (parabiotic; a
poorly understood phenomenon), with up to three species partitioning
common living space. Extremely aggressive Camponotus femoratus and
much smaller Crematogaster linata parabiotica usually share Amazonian
gardens in eastern Peru (Davidson 1988). Both species contribute to nest
construction. The latter builds the characteristically thin layers of carton
over runways, nest sites in crevices, and long-term food sources such as
extra¯ oral nectaries and Homoptera colonies. The former enlarges some of
these shelters with decaying leaves and other detritus improving the site for
roots. Any third species is usually smaller still (e.g., Solenopsis spp.) and
likely parasitic on its larger-bodied house mates (Wheeler 1921, 1942).
Camponotus femoratus alone accounted for the thousands of seeds encountered in the Peruvian nests it occupied with Crematogaster linata parabiotica.
Densities and behaviors better indicate the importance of the nest-gardening ants than does the abundance of their constructions. Ants known
to create nest gardens dominated the arboreal fauna at Tambopata, Peru
(Wilson 1987). Individual tree crowns fogged with insecticide in four types
of lowland forest yielded impressive numbers of taxa ± 43 species representing 26 genera in one sample alone, more than the entire ant fauna native to
the British Isles! Crematogaster linata parabiotica, here the nest companion
of Camponotus femoratus and Monacid debilis, occurred in almost half of
the 513 samples. Wilson attributed the great success of the ant-nest garden
species at Tambopata to their ability to produce capacious nests aided by
symbiotic epiphytes, including several nest-dependent bromeliads.
Catling' s (1995) inquiries on ant-nest gardens in the Stann Creek District
(tropical moist forest) of Belize merit special attention because he
addressed some new questions and a bromeliad ranked as one of the major
players. Citrus orchard was chosen for the survey because of its simplicity
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Relationships with fauna
compared with wild-type forest. Catling addressed three issues: the ® delity
of nest-garden taxa to ant carton, plant succession on that substrate, and
the possible in¯ uences of the nest-builder, which was an unidenti® ed
Azteca species, on the distributions of the recognized ant-dependent and
other local arboreal ¯ ora.
A total of 288 nests located in the crowns of 73 trees comprised one set
of samples. Five of the twelve (of which three were bromeliads) local nestgarden species infrequently (,5%) or never rooted on any other than antprovided substrates. Of these ® ve populations, just two, the orchid
Epidendrum immatophyllum and Aechmea tillandsioides var. kienastii, occupied more (,60%) of the censused gardens than the others (,40%).
Although entirely con® ned to cartons, A. tillandsioides var. kienastii
seemed to require site preparation by Epidendrum immatophyllum, or more
speci® cally its extensive root system, for establishment. Later, as the ant
nest expands (ages), the frequency of the orchid' s presence and its contribution to total plant cover on a carton decrease relative to that of the bromeliad. Several other nest-garden species (e.g., Coryanthes speciosa and
Codonanthe macrodenia) exhibited similar patterns of occurrence apparently also related to requirements for speci® c exposures. Like Epidendrum
immatophyllum, they yielded space to the bromeliad as shared nests grew.
Five sites provided the circumstances Catling needed to pursue the third
question ± whether Azteca sp. in¯ uences the distribution of arboreal ¯ ora
in the sampled orchards. Eighty trees with and 175 more without ant nests
supported one or more of the surveyed epiphytes. Yates chi-square and
analysis of variance indicated higher plant diversity in the crowns of antoccupied trees, but only because ® ve of the commonest epiphytes rooted
exclusively in nest gardens. Ants appeared to in¯ uence the welfare of only
two of the remaining 27 epiphytes. Ionopsis satyrioides and I. utricularioides, both short-cycled twig orchids, occurred less commonly in crowns
with compared with those without resident ant colonies. Catling made no
attempt to determine whether these ants, like some others that inhabit the
shoots of several Mexican bromeliads (e.g., Aechmea bracteata), reduce
herbivory on the tree or for the associated epiphytes (Dejean et al. 1992).
Except possibly for the two twig orchids, this Azteca species, unlike an
arboreal Crematogaster species in Malaysia (Weir and Kiew 1986), does not
remove epiphytes from the trees that support its nests.
Ant-fed, ant-house species
Ant-fed, ant-house Bromeliaceae outnumber those that root in cartons.
Moreover, the variety of zoobionts involved is also greater in accordance
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Ants and bromeliads
427
with the greater complexity and higher costs of the second form of myrmecotrophy for the ants and possibly the plants (Benzing 1991; Figs. 2.2E,
8.5). Farming involves elaborate social behavior in addition to carton construction, which in turn oblige relatively rich diets. Many of the same fauna
that nest in myrmecodomatia just as readily accept hollow twigs, cavities
under loose bark, or rolled-up dead leaves in addition to the plant organs
apparently evolved to attract them. However, enticements vary, and no
records suggest that any of the bromeliads equals certain other ant-house
¯ ora (e.g., Myrmecodia; Eshbaugh 1987; Davidson and Epstein 1989; Jebb
1991) for specialization for ant use. Nor do they associate as regularly with
speci® c zoobionts. On the other hand, more species of bromeliads than
members of any other family may pro® t by accommodating nesting ants.
Genera (e.g., Hoya, Hydnophytum) with recognized myrmecotrophic
members typically contain few species, or if larger include only the exceptional population unequivocally modi® ed to host nesting ants (Huxley
1980). Bromeliaceae follow suit. Conspicuously ant-adapted Tillandsia
bulbosa, T. butzii, T. caput-medusae, T. seleriana and some similarly con® gured relatives (Fig. 8.5) constitute but a small fraction of this largest of all
the bromeliad genera. Many additional Bromelioideae and Tillandsioideae
and at least one Pitcairnioideae (Brocchinia acuminata; Fig. 2.2E) also
house ant colonies, but at unknown frequencies and with undetermined
consequences for plant welfare.
Several bromelioids (e.g., Aechmea brassicoides, A. bracteata, A. setigera,
A. melinonii; Fig. 2.4G,L) possess unusual, bulbous phytotelm shoots in
which ants often raise brood. Figure 8.1D illustrates predominantly lithophytic Aechmea phanerophlebia in Minas Gerais State, Brazil partially dissected to expose pupae and adults among the upright leaves. Virtually all
of the Amazonian Bromelioideae harbor ant colonies along with
impounded moisture in much the same fashion, perhaps re¯ ecting high
densities of ants that render dry nest space an especially scarce and heavily
exploited commodity. Dejean and Olmsted (1997) identi® ed four kinds of
living space provided by the older ramets of Mexican Aechmea bracteata
(Figs. 2.4G, 8.1B).
Young specimens of Aechmea bracteata develop water-® lled leaf axils
® rst, after which the possibilities for housing multiply. Flowering is preceded by production of a single inrolled leaf whose amphora-like shape
excludes precipitation and probably most falling litter (Fig. 2.4G). Dead,
post-fruiting ramets open up still another kind of space until plants that
bear shoots representing every stage of development offer a variety of
kinds of chambers to fauna with different needs for moisture, food and
securement. Bases of the outermost foliage of mature, living shoots
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Relationships with fauna
intercept some precipitation but soon dry out. Better-insulated, somewhat
younger leaves within the shoot maintain deeper, more permanent phytotelmata. Chambers created by still younger and upright organs sequester
small amounts of moisture and debris, and the central cavity remains completely dry.
Fine-grained distributions within forests suggest that the ant-fed, anthouse bromeliads are constrained less by energy requirements than are
their nest-dwelling relatives. Tillandsia bulbosa and T. butzii sometimes
reproduce in considerable shade, equipped in part for dark habitats by ¯ at,
rigid trichome shields that, uncharacteristically for a Type Five bromeliad,
transmit instead of scatter photons whether wet or dry (Benzing et al. 1978;
Fig. 4.23F,G). These same appendages also shed rather than imbibe moisture, reducing the threat of suffocation which excludes the more typical
Type Five Tillandsioideae from overly humid ecospace (Fig. 4.11; Table
4.8).
Questions worth pursuing about these myrmecotrophic bromeliads
concern possible parallels with more specialized, better-known systems.
For example, do plant vigor and certain qualities of the microsite in¯ uence
which species of ants occupy speci® c bromeliads, and whether certain occupants provide better protection or more abundant plant nutrients than
others? Jebb (1991) reported 19 ant species belonging to 14 genera nesting
in Papua New Guinea Hydnophytinae. Weaker-growing specimens in
shade harbored the greatest diversity of mostly timid ants, whereas betterexposed specimens usually supported comparatively aggressive
Iridomyrmex species. Different ant behaviors and plant bene® ts may also
provide multiple options and mediate site-speci® c outcomes in tropical
America. Seventeen species of ants representing 11 genera in four subfamilies utilized the leaf base chambers of Tillandsia bulbosa in Quintana Roo
State, Mexico (Olmsted and Dejean 1987). No mention was made of any
correlations between plant exposure and occupancy by speci® c symbionts.
Rates of occupancy indicate importance to the ants and plants that
engage in myrmecotrophic relationships, and accordingly, considerable
impetus for certain ¯ ora to evolve myrmecodomatia and other enticements
for ants. Well over half of the Tillandsia butzii and T. caput-medusae specimens observed in Mexico and Costa Rica contained brood (Benzing
1970a), and the pseudobulbs of every Schomburgkia tibicinis specimen cut
open by Rico-Gray and Thien (1989) housed an active colony. No bromeliads produce seeds equipped with recognized elaiosomes, nor do any of the
ant-fed species supply an alternative source of nutrients dedicated to symbiotic fauna. However, pulp that adheres to the seeds of myrmecotrophic
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Ants and bromeliads
429
Bromelioideae may still bene® t the ants that nest in these species or cultivate them in cartons as discussed below.
Sometimes a phorophyte bene® ts by hosting as few as one ant-house bromeliad. Occupied trees in seasonally inundated and more elevated semievergreen woodland in the Sian Ka' an Biosphere Reserve in Quintana Roo
State, Mexico exhibited little damage attributable to the local leaf-cutting
ants (Atta spp.) compared with uncolonized conspeci® cs in the same forests
(Dejean et al. 1992). Atta cephalotes more heavily cropped Bursera simaruba trees free of ant-inhabited Aechmea bracteata or Schomburgkia tibicinis specimens, enough in some instances to reduce the total leaf area by
more than half. Hypoclinea bispinosa most often occupied these epiphytes,
but additional, less common ants (e.g., Azteca sp., Neoponera villosa) also
probably deter leaf cutters. Other colonies relegated to dead branches in
crowns devoid of bromeliads and orchids provided similar protection to
trees representing seven species, not including Bursera simaruba.
Additional myrmecotrophs, especially Tillandsia balbisiana, T. bulbosa,
and T. streptophylla, also appeared to be protecting their supports against
the potentially devastating attacks of a common chrysomelid beetle. Much
of the canopy of one phorophyte appeared to owe its undamaged condition to a colony of a small, unidenti® ed ant housed in the shoot of a single
bromeliad. Outcomes were impressive enough to prompt Dejean et al.
(1992) to propose the use of transplanted ant-inhabited epiphytes to
protect orchards that can be more attractive to leaf cutters than the average
tree in mixed forest. At the same time they cautioned against the possibility that ant-tended Homoptera on the same bromeliads and orchids might
spread pathogens (e.g., viruses).
Aechmea bracteata warrants special note among the ant-assisted
Mexican epiphytes for its similarity to Aechmea phanerophlebia, particularly the vase-shaped shoot (Figs. 2.4G, 8.1D), and the exceptional opportunity offered to symbionts by the four kinds of living space. Diverse, often
aggressive, ants number among the usual occupants (Dejean et al. 1995;
Dejean and Olmsted 1997). Surveyed plants mostly sheltered ant colonies,
some comprised of thousands of workers. Pachycondyla villosa and
Hypoclinea bispinosa predominated, but six other species in four more
genera occasionally also quartered there. An even richer ant fauna inhabited the spaces among the outer, dead leaves of 97% of the dissected plants.
Bene® ts to trees gained from the presence of ants that discourage herbivores as destructive as the leaf cutters would exceed just about any imaginable liability imposed by the presence of the few epiphytes necessary to
make this service possible.
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Dejean and Olmsted (1997) documented succession and related partitionment of Aechmea bracteata by fauna on the Yucatán peninsula. In all,
91.5% of 248 plants harbored one or more species of ants, and many additional symbionts were also present. Larvae of Odonata and Diptera occupied green shoots only, whereas the other large invertebrates there were
phytophagous (e.g., caterpillars, Tettigonidae). Dead post-fruiting ramets
supported mostly detritivores (e.g., Ascaridea, Diplopoda, Isopoda,
Thysanura, Collembola termites, Coleoptera) and their predators (e.g.,
Aranea, Phalangidae, Chilopoda, certain ants). Occupancy varied with the
type of habitat (three were surveyed), especially among the ants. Ants also
segregated among the spaces provided by the epiphyte according to body
size, diet, competitiveness and tolerances for neighbors.
Central cavities in green ramets usually sheltered relatively large aggressive ants (mostly Pachycondyla villosa at ® rst and then Dolichoderus bispinosus as plants aged). Azteca spp. and Dolichoderus spp. built carton
partitions there, and Pachycondyla villosa put rough plant debris to the
same use. Fewer species of ants (14 vs. 16) occupied the narrower, older leaf
bases and did so less consistently (31.3 vs. 91.5%). Inhabitants also tended
to be smaller (e.g., Monomorium ebeninum). Somewhat fewer ants (21 vs. 25
species) occupied dry ramets, but these included some fungus-cultivating
types (e.g., Cyphomyrmex minutus) that apparently use scraps provided by
other ants to grow mycelia. Predators specialized for speci® c prey (e.g.,
Leptogeny spp. for isopods, Odontomachus bruneus for termites) were also
present, along with many generalists (e.g., Crematogaster sp., Tetramorium
simillinum, Wasmania auropunctata). Certain species tended to co-occur
(e.g., Monomorium ebeninum and Camponotus abdominalis), and did so
intimately enough to suggest parabiosis comparable to that seen in certain
ant gardens (e.g., Wheeler 1921; Davidson 1988).
Dejean (1990) uncovered intriguing evidence that chemotaxis and molecular imprinting operate during the selection of either Aechmea bracteata or
Schomburgkia tibicinis by Pachycondyla villosa in the Sian Ka' an Biosphere
Reserve, Mexico. Experiments involved batches of workers and winged
females reared in vessels provisioned with leaf tissue harvested from either
of these two sympatric epiphytes. Females obliged to imprint on one or the
other host as larvae, upon maturation sought nesting sites in tubes containing tissue of the same bromeliad or orchid. Animals raised in the absence
of reference plants attempted to found colonies irrespective of the kind of
leaf tissue they encountered in the arti® cial myrmecodomatia.
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Evolution of ant/plant associations
In addition to ¯ exible diets and sociality, potential year-round activity and
the division of labor between reproductive and sterile (worker) castes
insured that the ants above all other insects would evolve the most specialized and multifaceted associations with plants (Davidson and Epstein
1989). At this point, we still know too little about the life histories and the
other biological phenomena that underlie ant/plant mutualisms to infer
how the many kinds of partnerships arose. But no single explanation could
suffice for every example anyway, even among the myrmecophytic bromeliads. Almost certainly, different circumstances and pathways account for
the diverse combinations of participants and the varied materials and services exchanged as consequences of these intimacies.
Substantial homoplasy characterizes the ways that ants and plants utilize
one another, but partnerships seldom exhibit the taxonomic speci® city that
often signals prolonged interdependence. Davidson and McKey (1993) cite
frequent shifts among the ants and the ¯ ora predisposed, or already modi® ed, to support them to explain the unexpectedly low incidence of coevolution and cocladogenesis among pairs of interacting ants and plants.
Outcomes for the individual ant-house epiphyte can be conditional,
ranging from positive to negative depending on the behavior of its zoobionts (e.g., do they farm Homoptera but simultaneously deter more costly
predators?). More remote variables, like the quality of the microsite, also
in¯ uence the net effects of symbiotic ants on plant welfare (Davidson and
Epstein 1989).
Several facts concerning ants and plants should guide the formulation of
hypotheses that address the less obvious aspects of myrmecophytism, especially origins and selective advantages. For example, nest-garden and anthouse status almost certainly evolved repeatedly among Bromeliaceae, and
probably also within some of its genera, but not with equal frequency
through the family. Members of Bromelioideae and perhaps a few
Tillandsioideae root in cartons, while populations representing all three
subfamilies engage in ant-house arrangements. Because bromeliads are
small, slow-growing herbs unable to offer high caloric rewards, the ants that
inhabit them tend to be opportunistic nesters, thus relatively indifferent to
host identity. Whereas the simple presence of an ant colony assures nutrients for the ant-house bromeliad and the occupant of a nest garden, protection from herbivores is not ipso facto an accompanying plant bene® t.
Ant/plant mutualisms succeed in part because much of the challenge to
the long-term viability of the insect colony, and accordingly the bene® ts
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Relationships with fauna
provided to associated ¯ ora, is countered by an ample supply of replaceable workers. Thus the inclusive group, most importantly its defended
queen(s), achieves considerable immunity from predators and potentially a
long life ± often as long as, or longer than, that of the plants they utilize
and nurture. Evolutionary access to this kind of mutualism probably
depended on a variety of predisposing ant and plant characteristics, some
obvious and others more difficult to recognize.
Ancestors of the ant-house bromeliads probably also produced cavities
among imbricated leaf bases, as do all but Type One, Two and some Type
Five species; antecedents of the nest-garden types likely offered attractive
seeds, although not necessarily typical myrmecochores with edible appendages (Chapter 6). Rooting media sufficiently impoverished to assure that
ant-provided nutrients would enhance growth were probably also necessary
to promote ant-house status involving elaborate myrmecodomatia and
abundant, plant-provided ant food. The same stock had less to gain from
adopting ant dispersal as discussed below. Evidence provided by plant
morphology and chemistry, ant behavior and the obligatory nature of some
of the alliances, particularly the nest-garden systems, suggests diffuse coevolution between certain Formicidae and the bromeliads they feed and
sometimes protect. Tighter alliances, i.e., species-speci® c combinations, are
improbable, and more so for the ants than for the plants.
Camponotus femoratus, one of the commonest Amazonian ant-nest
garden builders and a member of a fundamentally arboreal genus, seldom
if ever occurs unaccompanied by cultivated plants. But which members of
the co-occurring nest-garden ¯ ora it chooses seems to make no difference
(Davidson 1988). Securement of a nest by roots, and the elimination of
excess moisture by transpiration (Yu 1994), may occur irrespective of the
makeup of the garden. Less ¯ exibility characterizes the other side of the
relationship; certain nest ¯ ora, including some bromeliads, root nowhere
but on cartons.
Facultative combinations suggest beginnings for ant-house status ± for
example those between a variety of bromeliads lacking elaborate modi® cations to accommodate brood and primitive Formicidae with nonspeci® c
housing needs (e.g., Pachycondyla and Odontomachus). Frequent associations between opportunistic, docile occupants and only marginally bulbous
tillandsias indicate broad proclivity among arboreal species to utilize plant
cavities. For example, mostly feral ants occupied 10± 15% of the Tillandsia
paucifolia shoots surveyed in Florida (Fig. 6.7; Benzing and Renfrow
1971a). A group of structurally distinct relatives illustrates an even more
persuasive sequence in Quintana Roo State, Mexico.
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Evolution of ant/plant associations
433
Olmsted and Dejean (1987) listed ® ve co-occurring bromeliads (four of
the ® ve are illustrated in Fig. 8.5) in order of water-tightness and the
volumes of space comprising the bulb chambers (numbers in parentheses
denote frequency of ant occupancy): Tillandsia flexuosa (0%); T. baileyi
(30%); T. balbisiana (42%); T. bulbosa (41%); and T. streptophylla (53%).
Aechmea bracteata, A. phanerophlebia (Figs. 2.4G, 8.1D) and those numerous, similarly constructed, largely Amazonian (e.g., A. bromeliifolia),
water-impounding and ant-accommodating Bromelioideae constitute end
products of a similar evolutionary progression based on the same fundamental rosulate architecture, mutual bene® ts, and environmental context
(Fig. 2.4).
Ants offer myrmecophytic Bromeliaceae up to three direct services; how
many apply in each case is difficult to determine. Corresponding plant
requirements also range from one to three depending on the nature of the
interaction and the environment; speci® c enhancements probably also vary
somewhat among individuals comprising a population, especially those
bromeliads engaged in the ant-house syndrome as already discussed. Only
the nest-garden forms require ant assistance for seed dispersal. Whether the
two other services (feeding and protection) follow must be demonstrated.
Ant-house and nest-garden bromeliads seem to perform well enough in
conventional culture, in effect growing at normal rates without assisting
ants.
De® nitive tests for predator deterrence should be less challenging than
attempts to demonstrate any peculiarity of nutrition resulting from longterm association with ant-provided substrates. Massive defoliation following removal of especially pugnacious ants demonstrated the primary
bene® t of myrmecophytism for the bullthorn acacias (Janzen 1966). Antnest gardens could also be fumigated, and the bromeliads hosting ant colonies similarly deprived of any ant-mediated protection from herbivores.
Recall that Yu (1994; Chapter 4) noted the physical collapse of cartons
after clipping eliminated the capacity of associated ¯ ora to dissipate excess
moisture by transpiration.
Myrmecochory enhances bromeliad ® tness in the forest canopy to the
extent that the ants also provide the required rooting medium. Likewise,
¯ ora that root more pervasively should be poorly positioned to bene® t from
the attentions of seed-dispersing ants. Compared with the nest-garden
types, bromeliads that provide ant housing and anchor on bark can broadcast their offspring more widely owing to the less exacting nature of their
mutualists, none of which produce extensive cartons (rooting media). Not
surprisingly, Formicidae that colonize cavities through the forest canopy,
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Relationships with fauna
including those provided by a variety of nonmyrmecophytic plants, usually
ignored the seeds of several ant-nest epiphytes during feeding trials in Peru
(Davidson et al. 1990).
The existence of so many ecologically similar, ant-assisted and nonmyrmecophytic Bromeliaceae raises questions about the value of ant services.
Why, for example, are so few species taking advantage of the pervasive
availability of potential mutualists? Recall that close relatives of many of
the ant-house bromeliads typically co-occur (Chapters 5 and 7). Major
differences in vigor or fecundity, hence nutritional requirements, appear
unlikely to distinguish members of the two groups. Conceivably, closed
rather than open leaf axils enhance plant success for other reasons, perhaps
by increasing drought-tolerance. Then again, closer inspection of the ants
that regularly exploit these cavities might reveal as yet unnoticed services
such as the removal of mites or fungal spores. We could just as reasonably
question why only a dozen or so phytotelm Bromeliaceae beyond Aechmea
bracteata combine ant occupancy with capacity to process impounded
litter for nutrients (Fig. 2.4G).
More attention should be devoted to the ants that engage in long-term
mutualisms with bromeliads. Diet, aggressiveness, vigorous colony growth,
carton manufacture, and propensities to disperse seeds probably predisposed a subset of arboreal ants to nest in or cultivate certain bromeliads
and the other nest-garden ¯ ora (Davidson and Epstein 1989). However,
none of these attributes represents more than embellishments of more pervasive conditions. Characteristics that determine whether a given species
farms Bromeliaceae on carton or more casually adopts interfoliar cavities
to raise young are probably based on social organization and physiology
that foster suitability for manipulation by ¯ ora.
Experiments performed by Orivel et al. (1998) demonstrated that nest
gardening may constitute a more fundamental feature of Formicidae than
previously assumed; certainly it is not exclusive to the primarily arboreal
taxa (Dolichoderinae, Formicinae, Myrmicinae) characterized by welldifferentiated caste structure, polygyny and colonies served by large
numbers of exceptionally aggressive foragers. Pachycondyla goeldii and
Odontomachus mayi (Ponerinae), two relatively primitive species (monogynous, monomorphic worker caste, relatively small colonies) thought to be
no more than opportunistic occupants of abandoned gardens (Davidson
1988; Davidson and Epstein 1989), in fact harvested provided Aechmea
mertensii and Anthurium gracile seeds and planted them in carton constructed by the same ants at a site in French Guiana. Nest gardens resulted.
Tests designed to demonstrate preferences for the seeds of these two epi-
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Evolution of ant/plant associations
435
phytes over those of a variety of other species that never root in carton
proved inconclusive.
As the consummate chemical communicators, some of the more
advanced ants may require precursors from plants to produce certain pheromones or other bioactive compounds. Possibly the same end products
occur in both the ants and associated ¯ ora. Either way, the stage would be
set for a plant to exploit the susceptible ant. Discovery that the seeds and
sometimes the fruits of 10 nest-garden species native to Peruvian
Amazonia contain high concentrations of the same aromatic compounds
raises a number of questions that bear on the nature and origins of the nestgarden phenomenon (Davidson and Epstein 1989; Davidson et al. 1990;
Seidel et al. 1990). The most likely candidate for chemical cueing for myrmecochory is methyl-6-methylsalicylate (6-MMS), a tenaciously held constituent that potentially in¯ uences ant and plant success after the seed
separates from the rest of the fruit.
Seeds of Aechmea longifolius continued to read positive for bioactive aromatics after repeated washing with pentane. Especially provocative was the
discovery that the mandibular glands of male Camponotus femoratus
contain the same compounds, most notably 6-MMS, as the seeds of the
tested ant-garden ¯ ora, and that these components were probably endogenous rather than plant-derived. At least two of the ® ve compounds exhibit
fungistatic activity indicating potential to protect brood. Interestingly,
Camponotus lacks metapleural glands, which in some other taxa produce
useful antiseptic secretions.
Chemicals associated with seeds that today help maintain sterile cartons
might have acted earlier to counter pathogens among the abundant micro¯ ora present in the moist humus that many epiphytes utilize for roots.
Prolonged occupancy of a carton by its builders may oblige the use of some
external source of an inhibitory compound, perhaps impregnated seeds, to
avoid brood-destroying fungi. An alternative hypothesis posits mimicry as
the mechanism that moves seeds from one ant-provided substrate to the
next. Seed size and color suggested to Ule (1906) and Madison (1979) that
physical resemblance helps disperse some of the Amazonian bromeliads.
Volatile chemicals may enhance this relationship or even mediate the deception unaided by visual or nutritional cues (Davidson and Epstein 1989;
Davidson et al. 1990; Seidel et al. 1990). Insects that parasitize ant colonies
gain entrance by manipulating ant behavior with fragrances so why not
plants, including the nest-garden bromeliads?
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Relationships with fauna
Termites
Two additional groups of social insects associate with the bromeliads, one
quite unexpectedly, the other more casually although perhaps to advantage
if the adjacent plants also harbor colonies of pugnacious ants. Wasps often
nest near vegetated cartons in Ecuador, where together with the ants they
pose an exceptionally formidable challenge to marauding vertebrates,
including curious biologists. Stranger still, termites often seek out established bromeliads, both on the ground and in trees (Fig. 8.1A,B,E). Termite
nests and covered trails typically support no rooted ¯ ora, consistent with
the termite diets and the hardness of their cartons (soil and partially
digested wood) compared with those manufactured by ants.
Thorne et al. (1996) noted that many of the trees on Guana island in the
British West Indies supported covered trails engineered by Nasutitermes
acajutlae leading to the leaf axils of large Tillandsia utriculata specimens.
Younger plants not yet able to impound precipitation escaped attention.
Covered pathways mapped on 97% of 115 trees intersected at least one
adult bromeliad. Tunnel-building occurred at night, and progressed from
the epiphyte to the ground rather than the reverse, apparently because the
plant offered a superior supply of the moisture required to construct
carton. Bene® ts to the termites are obvious, but not so those for the plant.
Also unclear was the consistency of the association from year to year.
Rainfall during the 24 months preceding Thorne et al.' s observations had
been unusually light on Guana island, and the resulting aridity perhaps
sufficient to force the local termites to seek unusual sources. Moisture is an
especially scarce commodity where precipitation quickly percolates into the
porous limestone beneath the island' s shallow soils. Although Nasutitermes
acajutlae exceeds many of its relatives for water economy, diminished populations indicated considerable vulnerability to extreme drought. Revisits
during wetter seasons and observations elsewhere would help settle the
issue of regularity, as would closer inspection of the bromeliads on the
question of plant welfare. While thirsty insects probably consume little of
the hundreds of milliliters of moisture impounded in a typical shoot,
termite earthworks may pose a greater threat as occasional trails were moist
up to 30± 35 cm beyond the contacted shoots. Other termite constructions
covered rather than drew water from leaf axils, possibly insulating the
supply for these plants.
Unidenti® ed termites also regularly associate with terrestrial and lithophytic Bromeliaceae and other low-growing ¯ ora in the campos rupestres
habitats of Minas Gerais State in southeastern Brazil. Figure 8.1A illus-
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Phytotelm bromeliads
437
trates Aechmea phanerophlebia anchored to rock below which a termite trail
extends to the ground. Mounds of inhabited carton occurred more commonly around soil-rooted Dyckia and Encholirium specimens (Fig.
8.1D,G), among other local perennial herbs (e.g., Velloziaceae).
Circumstances here also suggested opportunistic behavior effected by termites seeking the structural strength offered by an established plant, or, in
the case of the spiny-leafed Pitcairnioideae, perhaps a deterrent to local
ant-eaters.
Bene® ts for Bromeliaceae could include nutrients and moisture on relatively rocky, well-drained soils, or insulation against the ® res that regularly
sweep across these hyperseasonal habitats. Conversely, vulnerability could
be high where litter rather than wood-feeding species are involved. Termites
were abundant among the bases of the shoots of an unidenti® ed Alcantarea
population growing on otherwise bare rock in Bahia State, Brazil (personal
observation). Depending on diet, these insects could either help dislodge
these unusually heavy, long-lived plants, or reduce the threat of pathogens
by preventing the accumulation of too much dead leaf tissue.
Dejean and Olmsted (1997) provide the most detailed account of how
termites interact with a bromeliad, in this case with Aechmea bracteata
(Fig. 8.1B). Populations native to inundated forests, and to lesser extents
nearby upland sites in certain areas of the north coast of the Yucatán
peninsula, afford termites, in addition to the ants already mentioned, space
to raise brood in living and spent shoots. Green ramets sheltered only
Nasutitermes sp., while the dead ones no longer capable of retaining water
housed several Rhinotermitinae and Nasutitermitinae, perhaps to access
edible leaf tissue as much as to obtain dry nesting space. Nasutitermes sp.
even outcompetes certain ants for the use of this large epiphyte, but plants
are shared with some other taxa, and at a price. Carnivorous species (e.g.,
Anochetus emarginatus, Odontomachus bruneus) routinely cohabit with
Nasutitermes sp. in different parts of the same bromeliads, where they probably treat the termite workers as a ready source of ant food.
Phytotelm bromeliads
Bromeliaceae provide high-quality living space in the form of impounded
humus and moisture for diverse biota. Volumes per unit area range from
substantial at locations humid enough to support high densities of phytotelm species (Figs. 1.2C, 2.4) to negligible where aridity mandates water
storage in succulent foliage rather than open reservoirs. Arthropods also
hide and forage among the enclosed dry leaf axils of certain Type Five
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Relationships with fauna
Tillandsioideae (Fig. 8.5), but the contributions these plants make to the
carrying capacities of habitats must be minor. Fish (1983) probably identi® ed the upper end of the range of potential impacts with his calculated
50000 l of moisture suspended per hectare based on the densities of resident Bromeliaceae that Sugden and Robins (1979) reported in a Colombian
cloud forest.
One tank bromeliad can provide expansive and varied accommodations
for aquatic and terrestrial biota; a mature Glomeropitcairnia erectiflora
specimen, for example, offers both a central reservoir that impounds several
liters of water and, for the more desiccation-resistant organisms, equal or
greater volumes of progressively drier debris packed among older, no
longer water-tight leaf axils. Brocchinia micrantha produces even more of
the same kinds of ecospace, and maintains them longer as a giant terrestrial in eastern Venezuela and Guayana. Lithophytic, Brazilian Alcantarea
regina currently holds the record for water-tight volume, at 45 liters (Zahl
1975; Fig. 1.2C).
Theoretical considerations
Picado (1911, 1913) envisioned phytotelm Bromeliaceae as the physical
basis for a fragmented, aerial swamp distributed through the humid forests
of tropical America and occupied by abundant fauna seeking shelter,
breeding space and food. Extensive biota and no putrefaction despite substantial impounded litter persuaded Picado to conduct noteworthy experiments designed to demonstrate how plants and their symbionts interact to
mutual advantage. While not carnivorous as he suspected, the tested bromeliads nevertheless depend on phytotelmata for moisture and nutritive
ions through a mechanism labeled animal-assisted saprophytism (Chapter
5). Resident biota in turn bene® t from several services provided by the
hosting plant.
Cool conditions may have accounted for Picado' s failure to detect putrefaction because unpleasant odors sometimes reveal substantial anaerobiosis at warmer sites (e.g., Aechmea nudicaulis, Neoregelia cruenta in restinga;
Fig. 7.13C,E). Conversely, subsequent study (e.g., Laessle 1961; Maguire
1971; Frank and Lounibos 1987; Paoletti et al. 1991) would corroborate his
observations that bromeliad phytotelmata favor exceptionally diverse and
densely packed biota. Frank and Lounibos (1987) addressed Picado' s speculations concerning phytotelmata as swamp analogs according to island
biogeographic theory (MacArthur and Wilson 1967).
Biota determine whether a phytotelm bromeliad acts more like a swamp
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Phytotelm bromeliads
439
or an island (Frank and Lounibos 1987). Colonizers of phytotelmata
swamps should arrive at the earliest opportunity and more or less as complete assemblages comparable to those occupying similar kinds of ecospace
nearby. True symbionts, as opposed to the casual visitor, would be plantcavity specialists. Once established, the resulting tank-based communities
should exhibit high diversity and relatively stable composition. Were phytotelmata island the better descriptor, residents would tend to arrive
according to their vagility, with the most mobile forms appearing ® rst.
Intense interactions and con® ned spaces would promote signi® cant species
turnover and limit biodiversity.
Various arthropods, including a number of mosquitoes and some ostracods, identify phytotelm bromeliads as islands by colonizing them more or
less exclusively. However, many more lower organisms (e.g., algae, rotifers,
other small crustaceans) arrive passively, and also occupy a variety of other
types of nearby wet habitats. The specialists distribute unevenly among
bromeliad shoots according on one hand to their requirements and on the
other to certain site-speci® c qualities of the plants, particularly exposure
and whether litter or algae form the trophic base for the community. In
essence, bromeliads represent swamp fragments and islands depending on
the identity of the user and certain local circumstances that in¯ uence living
conditions in water-® lled plant cavities.
Resident microflora, flora and invertebrates
Numerous surveys (e.g., Picado 1911, 1913; Laessle 1961; Maguire 1971;
Fish 1976; Frank 1983; Paoletti et al. 1991; Table 8.2) document the broad
hospitality of the bromeliad shoot for micro¯ ora, invertebrates and even
some vascular plants ± namely, carnivorous Utricularia humboldtii in
Brocchinia tatei (Fig. 8.4B) on Cerro Neblina, Venezuela and Utricularia
reniformis and U. nelumbifolia in several Brazilian Alcantarea and Vriesea
species and Brocchinia micrantha in Guayana. These last two bladderworts
discriminate among certain Vriesea species in southeast Brazil. For
example, Utricularia nelumbifolia regularly inhabits the shoots of intermixed populations of Vriesea crassa and V. atra anchored on the steep
¯ anks of at least one granitic dome near Rio de Janeiro, but not those of
co-occurring Alcantarea imperialis. Utricularia reniformis colonizes various
Tillandsioideae and nearby wet, moss-covered rocks. The aquatic moss
Philaphyllum tenuifolium reportedly ¯ ourishes in the shoots of an unidenti® ed Vriesea or Alcantarea at Alto da Serra, São Paulo, Brazil (Hoehne
1951).
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Relationships with fauna
Bermudes and Benzing (1991) encountered Chlorophyta in addition to
those cyanobacteria described in Chapter 5 in the Ecuadorian bromeliads
they examined. Numerous algae, mostly diatoms, turned up in additional
surveys (e.g., Lyra 1971). Still other reports (e.g., Laessle 1961) list protozoans and fungi, but no bromeliads have been screened for microbial activities important to N cycling, beyond the presence of nitrogenase (Table
5.12), or to the mineralization of impounded plant debris. Janetzky and
Vareschi (1993) noted correlation between the litter present and bacterial
counts in the phytotelmata maintained by several Jamaican bromeliads.
Laessle (1961) recovered 60 kinds of invertebrates from the shoots of
bromeliads in Jamaica; Picado (1913) encountered 130 in Costa Rica.
Frank (1983) reported that about half of the 470 identi® ed arthropod
species collected in bromeliad phytotelmata were mosquitoes. Some 400
species in 15 genera representing at least 20% of those residing in the
Neotropics breed there at least occasionally (Fish 1983). Total fauna far
exceed these numbers even ignoring the microinvertebrates. A recent survey
of several Venezuelan Bromeliaceae revealed an impressive array of taxa
(Paoletti et al. 1991; Table 8.2), some new to science. Among the tank-residing macroinvertebrates (.3.0 mm), no fewer than 80 collections represented as many undescribed species. Preliminary examinations further
indicated the possibility of at least three new genera. Oliveira et al. (1994)
provided data that for the ® rst time included apportionments of biomass
among the fauna sampled in bromeliad shoots (Fig. 8.6).
Phytotelm bromeliads pose signi® cant public health hazards in parts of
tropical America. Tank-dwelling arthropods include blood-feeding midges
(e.g., Ceratopogonidae), horse¯ ies and mosquitoes known to carry yellow
and dengue fevers, certain strains of equine encephalitis, some ® larial
worms, and a variety of lesser diseases (e.g., Klein 1967; Zavortink 1973).
Several Anopheles species (e.g., A. homunculus, A. neivai) capable of transmitting malaria favor phytotelmata for egg-laying, and continue to encourage tree cutting and heavy herbicide use to eliminate the offending
bromeliads in parts of Amazonian Brazil (Reitz 1983). Linkage between
malaria and bromeliads received intense study during the Second World
War in Trinidad where natives like Aechmea aquilega supported Anopheles
bellator (Pittendrigh 1946, 1948). Occasional relationships bring commercial bene® ts, for instance to the owners of some Central American cacao
plantations where midges (Ceratopogonidae and Ceridomyiidae) that
Privat (1979) considered important for fruit set by this self-incompatible
crop use the local bromeliads to reproduce.
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Phytotelm bromeliads
441
Figure 8.6. Biomass of invertebrates (.2.0 mm) and vertebrates present in the phytotelmata of Neoregelia cruenta in a Brazilian restinga (modi® ed from Oliveira et
al. 1994).
Community dynamics
Activities within and around the bromeliad phytotelma remain too poorly
studied to justify more than a few tentative remarks. Those few reports that
exceed mere checklists of inhabitants mostly deal with the biology of a few
frogs and a somewhat larger number of invertebrates, primarily mosquitoes, particularly species of Wyeomyia, the chemistry of the impounded
¯ uids, and the structure of the included food webs. More is known about
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442
Relationships with fauna
certain aspects of tree holes and the water-retaining ¯ oral bracts of
Heliconia (e.g., Maguire 1971).
Naeem (1990) demonstrated how litter in¯ uences the structure of communities in certain aquatic systems. Bromeliads with their unusually large,
structurally more varied and enduring shoots probably harbor correspondingly more complex microcosms (Chapter 5). Laessle (1961) demonstrated
that local conditions and plant shape and size determine whether a
bromeliad-based community builds upon autotrophic or heterotrophic
foundations in Jamaica. Exposed, spreading rosettes sometimes supported
considerable algae; Ecuadorian specimens tested by Bermudes and Benzing
(1991) also hosted cyanobacteria judging by assays for nitrogenase (Table
5.12). At shadier sites, trophic pyramids build on accumulated litter
(Laessle 1961; Frank 1983).
Biota in the catchments provided by Neoregelia cruenta and Aechmea
nudicaulis (Figs. 8.7, 8.8) in a Brazilian restinga con® rmed and expanded
the list of characteristics that differentiate phytotelmata located in the sun
vs. the shade (beyond and under shrubs). Temperatures that exceeded 36 °C
appeared to exclude some shade-dependent fauna from exposed shoots
(Oliveira et al. 1994). Odonata preferred sun, while exceptionally tolerant
Ostracoda ¯ ourished in both settings. Colonizations of cleaned tanks and
to lesser degrees glass vessels varied by taxon, being particularly rapid for
Ostracoda and Diptera (mosquitoes). Some strictly aquatic forms like the
ostracod Elpidum bromeliarium travel among plants by clamping on the
skin of migrating frogs (L. C. S. Lopez, personal communication).
Tank fauna also varied depending on the shape of the shoot in comparisons of funnelform Aechmea nudicaulis and more spreading Neoregelia
cruenta (Oliveira et al. 1994; Fig. 8.7). Subjects grow intermixed through a
restinga near Rio de Janeiro where the adults of both species impounded
about 80 ml of water either in one central, deep tank (Aechmea nudicaulis)
or in several shallower, more exposed leaf axils. Phytotelmata maintained
by Aechmea nudicaulis remained relatively full through the dry season compared with those of Neoregelia cruenta, which shrank to a few percent of
capacity. Associated fauna also varied, with the ostracods predominating
in the shoots of Aechmea nudicaulis, and some copepods assuming that
status in Neoregelia cruenta. Rotifers and insect larvae exhibited more even
apportionments between the two hosts.
Miller (1971) noted that three groups of Diptera (Cullidae,
Ceratopogonidae, Chironomidae) partitioned the bromeliad ¯ ora on St
John and Anegada in the Caribbean Virgin Islands according to moisture
supply, although the mosquitoes, occasionally predatory types, occupied
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443
Figure 8.7. Recolonization of the phytotelmata of Aechmea nudicaulis and
Neoregelia cruenta by copepods, ostracods and Culicidae during winter and
summer in a Brazilian restinga. Recollections occurred at 4± 16-day intervals after
the initial census (modi® ed from Madeira et al. 1995).
some of the sampled plants. Cullidae predominated in the shoots of
montane Aechmea lingulata, which remain continuously water-® lled on St
John. Along the considerably drier coast of Anegada, Tillandsia utriculata
hosted fewer mosquito larvae, and instead harbored abundant ceratopogonid midges. At lower elevations on St John where humidity usually
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Relationships with fauna
Figure 8.8. Data for copepods only for the plants considered in Fig. 8.7.
registers somewhere between the other two collection sites, representatives
of all three families colonized the same plants, although midges of both
taxa dominated. Apparently these insects tolerate drier shoots, faring less
well as the length of the rainy season increases.
Fidelity and adaptation
Dependence on phytotelmata varies among the users. Lower forms (e.g.,
algae, protozoans, rotifers), compared with many of the higher organisms
reported in bromeliad shoots, occupy a variety of other kinds of cavities.
Conversely, Laessle (1961) reported three ostracods (Metacypris) as bromeliad endemics. Reitz (1956) imputed obligatory status to related
Elpidium bromeliarum, which inhabits numerous bromeliads native to
Santa Catarina State, Brazil in addition to the two restinga species investigated by Lopez et al. (1993).
Mosquitoes rely on sophisticated behavior, small size and keen senses to
use bromeliads. Some species favor plants that belong to a single genus (e.g.,
Frank and Curtis 1981a,b), while others exploit more diverse ¯ ora, including nonbromeliads. For example, Frank and O' Meara (1985) demonstrated
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445
that ovipositing Wyeomyia vanduzeei preferred Tillandsia utriculata over
Catopsis berteroniana in Florida. Wyeomyia mitchellii was less in¯ uenced
by plant identity than by aspects of the macrohabitat, judging by the
greater numbers of eggs and larvae in shaded compared with fully exposed
shoots.
Several Costa Rican bromeliads consistently failed to support the same
Paramecium species that reach substantial densities in nearby Heliconia
bracts. Germer (1982) and Frank and Lounibos (1987) reported the same
outcome for algae comparing water-® lled beakers and Billbergia pyramidalis shoots during an experiment in Florida. In the ® rst instance, runs
employing untreated plants and others emptied and re® lled with clean
water, and arti® cial microcosms concocted with ® ltered and un® ltered tank
¯ uids, failed to yield conclusive results. Toxins offer one possibility, but
higher losses in un® ltered tank water and untreated shoots suggested a
greater role for predators.
Some gravid tree hole-users cue on chemical and physical traits that
relate less to the identity of the tree than to the probable duration of a
cavity' s moisture supply (Bradshaw and Holzapel 1984). Wyeomyia smithii
seeks relatively young Sarracenia purpurea leaves for egg-laying by following a food stimulus (Bradshaw 1983). Signals emanating from both the phytotelmata and the containing shoot seem to prompt bromeliad utilization.
Frank (1985, 1986) used colored receptacles to demonstrate that Wyeomyia
vanduzeei prefers dark green targets, while W. mitchellii favored the deep red
type.
Anopheles aegypti consistently choose the darkest containers when
offered the same set of options augmented with additional vessels in several
lighter colors. Preferences for sunny vs. shaded phytotelmata could explain
these results as mosquitoes vary substantially on this basis, some assiduously avoiding exposed spaces where plants exhibit brighter silhouettes.
Signals that indicate plant maturity and health provide additional useful
information, especially to insects with extended larval stages. The presence
of an in¯ orescence or necrotic foliage reveals shoot age and condition
respectively and accordingly, the likelihood of holding water long enough
to complete larval development (Frank 1985, 1986).
Discrimination also occurs in space, sometimes over distances measured
in centimeters (Frank and Curtis 1977b). Lateral, as opposed to central,
tanks attracted more egg-laying in some trials, perhaps because heavy rain
disturbs the contents of the younger leaf bases more than the older ones
displaced below and therefore better insulated by overhanging foliage. Egg
rafts laid by Wyeomyia vanduzeei proved vulnerable to washout from
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Relationships with fauna
Figure 8.9. Colonization of arti® cial bromeliads by Diptera. Animals present were
counted every 30 days (after Krügel 1993).
Tillandsia utriculata shoots in Florida compared with larvae or pupae.
Should losses be great enough, compensatory egg-laying seems likely to
evolve.
Seventy-four mature Guzmania weberbaueri specimens interspersed
among 96 ersatz bromeliads (funeral vases) for 13 months in Peruvian
Amazonia attracted 26 species of ¯ atworms, nematodes, annelids, insects
and vertebrates representing about 2800 individuals (Krügel 1993; Fig.
8.9). Monthly counts proved too infrequent to fully document colonization. Two Culex species predominated among the immigrants, with nematodes constituting the second best represented taxon. If selective, the
mosquitoes tended to favor the bromeliads. Odonata and Salatoria, the top
invertebrate predators, consistently avoided the wide-mouthed, 250 cm3
grave vases. Microhydid Syncope antenori proved less fastidious by using
real and simulated phytotelmata at about the same rate for egg-laying.
Nematodes apparently arrived by migrating up from the ground. Neither
copepods nor ostracods colonized either type of vessel, although both
groups usually appear in the checklists of bromeliad fauna.
Following discovery of a suitable medium, some bromeliad-users bring
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Phytotelm bromeliads
447
Figure 8.10. Total number (eggs, larvae, pupae) of Wyeomyia vanduzeei and
Wyeomyia medioalbipes demonstrating relationships between numbers of immature mosquitoes present and the size of the hosting phytotelmata of Tillandsia utriculata in south Florida (after Frank et al. 1977).
additional adaptive behavior into play. Gravid Wyeomyia vanduzeei and W.
medioalbipes gauge the relative utility of phytotelmata provided by Florida
Tillandsia utriculata according to shoot volume (Frank and Curtis 1977a;
Frank et al. 1977; Figs. 8.10, 8.11). Numbers of eggs laid through the
season tracked tank size rather than the amounts of impounded organic
debris available for feeding. Values for larvae also increased with ¯ uid
volume, and those inhabiting the more heavily populated shoots matured
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Relationships with fauna
Figure 8.11. Number of instar II Wyeomyia vanduzeei relative to impoundment
capacity of Tillandsia utriculata in south Florida (after Frank et al. 1977).
slower than their counterparts at lower densities elsewhere. In effect,
uncharacterized, density-dependent cues help regulate populations by
moderating larval demands for ® nite, plant-provided resources. Life cycles
match substrates in a second, time-related dimension. Progress from egg to
pupae requires at least two weeks rather than the mere 4± 5 days for species
adapted to ¯ ood waters and similarly ephemeral breeding media.
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449
Apparently, bromeliad shoots rank among the more durable of the many
kinds of breeding sites utilized by Neotropical Culicidae (Frank 1983).
Coevolution probably played no more than a minor role in shaping the
relationships between phytotelm Bromeliaceae and the mutualistic invertebrates they accommodate. When change did occur, it was mostly asymmetrical as in ¯ owers that mimic their pollinators or certain food sources of
those animals (Orchidaceae). Dependent fauna changed more in the interaction with the bromeliad shoot and the affected characters involved body
form, life cycle and behavior. Ant-house Bromeliaceae represent exceptions
to this rule assuming that the bulbous shoot (Fig. 8.5) indeed re¯ ects a
response to plant-feeding by ants, yet none of these animals possesses features evolved primarily to assist plant nutrition.
A third party like Toxorhynchites haemorrhoidalis can exaggerate the
impact of plant form on certain co-occurring tank occupants. Larvae of
this predatory mosquito heavily cropped other immature dipterans inhabiting the same single, deep pool provided by the tubular shoot of
Venezuelan Aechmea nudicaulis (Frank et al. 1984; Lounibos et al. 1987;
Fig. 7.13C). Aechmea aquilega harboring this same relatively immobile
insect provided safer refuge to potential prey simply by offering multiple,
relatively isolated leaf axils. Vulnerability to foraging birds or reptiles could
follow quite different, bromeliad-speci® c patterns.
Morphology suggests that bromeliads have in¯ uenced the evolution of
fauna representing diverse taxa. Several dragon¯ ies (Calvert and Calvert
1917), crane ¯ ies (Alexander 1912) and syrphids (Knab 1912) bene® t from
body shapes that long histories of tank use could explain. The damsel¯ y
Leptogrion perlongum needs its unusually long abdomen to oviposit in the
water sequestered deep in bromeliad shoots (Fig. 8.4C). Pronounced ¯ attening favors penetration and greater mobility among appressed leaf bases
for some bromeliad-inhabiting lumbricoids and isopods (M. G. Paoletti,
personal communication). Certain earthworms may be exceptionally well
adapted by a variety of characteristics to live in and around epiphytic bromeliads, as indicated below.
Land-dwelling species of Aratus and Metopaulias represent notable
exceptions within the predominantly marine crab family Grapsidae by possessing unusually long, slender legs and narrow carapaces. Both modi® cations favor arboreal life generally and, for several species, movements in
and around the bromeliad shoots used for shelter and reproduction
(Laessle 1961; Read 1969; Abele and Means 1977). McWilliams (1969)
encountered Sesarma miersii among the leaf bases of a variety of
Bromelioideae at two sites in the state of São Paulo, Brazil, although
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Relationships with fauna
Table 8.3. Effects of conditioning by egg-laying Metopaulias depressus on
conditions in bromeliad leaf axils in Jamaica
Unconditioned
tanks
Conditioned tanks
Dissolved O2
pH
Ca21
Declines to as
little as 15%
at night
Median value 4.8
1 mg in 240 ml leaf axil
(average-sized nursery)
Usually
remains
above 35%
Median value 6.8
3.12 mg in leaf axils of
about the same volume
Source: After Diesel and Schuh (1993)
inhabited plants occurred near brackish water suggesting transitory rather
than long-term occupancy. Metopaulias depressus removes damsel¯ y
nymphs to protect its larvae in some Jamaican bromeliads, a behavior that
presumably required extended tank use to evolve (Diesel 1992).
Metopaulias depressus takes parental care well beyond the protection and
feeding of progeny by also mitigating the harsh physicochemical conditions
that so often prevail in bromeliad phytotelmata. Diesel and Schuh (1993)
con® rmed that unmanipulated media in the axils of Jamaican bromeliads
tend to be too acidic, anoxic and Ca-depleted to meet the needs of young
crabs before they begin to feed and become less vulnerable to such unfavorable limnology. Attending adults remedy all three de® ciencies by removing
litter, which promotes oxygenation, and by adding fragments of snail shells
preparatory to egg-laying. Calcium ions released from the gastropod
remains promote carbonate buffering and facilitate chitin synthesis at
molting. Table 8.3 illustrates the contrast between unmodi® ed leaf axils
and those conditioned by adult crabs. Molecular systematics indicates that
M. depressus and the other six arboreal crabs of Jamaica share a common
ancestor that lived no more than four million years ago (Schubart et al.
1998). Bromeliaceae probably played a key role in this radiation.
Plant-provided benefits to resident fauna
Much of the phytotelm bromeliads' impact on associated biota depends on
conditions in the impoundments located among its overlapping leaf bases.
Destruction awaits prey lured by fragrances and color to the lubricated,
steep-walled phytotelma of Brocchinia reducta (Fig. 2.4F). Although frogs
and some arthropods thrive in the ¯ uids accumulated by this carnivore,
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Phytotelm bromeliads
451
phytotelm Bromeliaceae that depend on litter rather than prey support a
much more extensive biota. However, experiments using arti® cial vessels
provisioned with the same contents as nearby bromeliad shoots indicate
that some colonists discriminate among different kinds of plant cavities
(e.g., Krügel 1993).
What makes the space produced by the shoot of a humus-based bromeliad so accommodating for such a variety of associates, yet apparently inimical to some others? With sufficient time, any catchment ® lled with moisture
and litter will attract some occupants, but not those that respond to or
require additional, plant-speci® c characteristics. Perhaps the bromeliad
embellishes the already rich mix of resources in its phytotelma with oxygen
from adjacent leaf tissue, while simultaneously discouraging certain other
biota. Observations conducted in situ indicate multiple in¯ uences dictated
by the bromeliad and others by its immediate environment.
Laessle' s (1961) observations in Jamaica on some 75 specimens representing species of Aechmea, Hohenbergia, Guzmania, Tillandsia, and
Vriesea revealed that the angle of the leaf axil in¯ uenced the welfare of resident fauna through its effect on the chemistry of the impounded ¯ uids.
Water surface to volume ratios (e.g., higher in the relatively lax shoots of
Aechmea paniculigera than in the more upright Vriesea species; Fig.
2.4A± D) and within a rosette (greater in older than younger leaves) generally correlated with higher O2 and lower CO2. Acidity, O2, and CO2 often
¯ uctuated from day to night although unevenly. Diurnal oscillations varied
among the leaf bases in a single shoot (Table 8.4), and from one rosette to
another, with the most pronounced changes occurring in the most exposed
plants. Concentrations of both gases usually re¯ ected the kinds and
numbers of organisms present rather than any identi® able features of the
hosting plant.
Janetzky and Vareschi (1993), working in Jamaica on some of the same
species examined by Laessle, recorded similar diurnal ¯ uctuations in O2
and higher readings in the phytotelma of exposed compared with shaded
specimens (Aechmea paniculigera and Hohenbergia sp.). They also noted
that O2 concentrations diminished from the surface downward (Fig. 8.12).
Low O2 tensions and muted ¯ uctuations characterized tanks containing the
most detritus. Bacteria counts paralleled the modest values recorded for the
better-known black water systems that likewise owe their chemical peculiarities to degrading vegetation. High concentrations of dissolved N and
P underscored the value of the phytotelma for plant nutrition (Fig. 8.13).
Krügel (1993) working with terrestrial Guzmania weberbaueri in Peruvian
Amazonia also reported how pH varied with plant exposure and tank
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Relationships with fauna
Table 8.4. Water chemistry in seven leaf axils of a single Aechmea
paniculigera shoot. This specimen was growing in full sunlight. Leaf axil
number 7 was uppermost and received the most light. Leaf axil number 1
was the oldest on the shoot that still held water. Daytime readings were
taken between 09.45 hours and 11.30 hours and those after dark between
20.30 hours and 22.30 hours
CO2 (ppm)
O2 (ppm)
pH
Leaf axil
Day
Night
Day
Night
Day
Night
1 (oldest leaf)
2
3
4
5
6
7 (central tank)
12.0
5.5
4.0
6.0
9.0
8.0
11.0
12.0
12.0
21.0
16.0
16.0
18.0
44.0
0.5
6.6
6.0
7.6
5.6
5.4
7.8
1.6
1.4
1.6
2.6
1.6
1.6
0.4
5.4
6.3
6.7
5.8
5.6
5.2
4.9
5.2
6.7
6.8
5.9
5.3
5.2
4.7
Source: After Laessle (1961).
contents, perhaps in the second instance re¯ ecting respiration by resident
saprophytes.
Still another study conducted on immature Aechmea bracteata under
controlled conditions provided a record of change in the ¯ uids sequestered
in the central and one lateral cavity of a phytotelm bromeliad (Benzing et
al. 1972). Cleaned leaf axils of one set of specimens were re® lled with distilled water only; those of another group also contained rotting leaf debris,
green algae or damsel¯ y nymphs. Small glass beakers treated identically
served as controls. Photon ¯ ux density equaled about 12% of full sunlight
during the 12-h photoperiods.
The results, some of which are depicted in Fig. 8.14, indicate that the resident organisms in¯ uenced the chemistry of impounded water most of all.
Illuminated or darkened, plant chambers and beakers ® lled with distilled
water never exceeded 60% O2 saturation. During the same runs, CO2
became more concentrated in the tanks, probably because some of the epiphyllae remained despite judicious cleaning. Simultaneously high CO2 and
low O2 required the presence of animals or decomposing biomass. Only
illuminated algae elevated O2 to saturation. Fluids remained almost continuously acidic, sometimes more so at night than during the day whether or
not other materials were present or the exposure was high or low; beakers
containing illuminated algae alone produced pH readings near 7.0.
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Phytotelm bromeliads
453
Figure 8.12. Oxygen saturation (%) in bromeliad phytotelmata in Jamaica. (A) Sunexposed specimen with algae. (B) Shaded specimen with litter. Measurements were
taken at different depths in the morning, at midday and in the evening (after
Janetzky and Vareschi 1993).
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Relationships with fauna
Figure 8.13. Concentration of total phosphorus present in 16 phytotelmata of
Aechmea paniculigera in Jamaica (after Janetzky and Vareschi 1993).
Substantial evidence indicates that the bromeliad does not actively in¯ uence the abundance or diversity of the fauna that use its phytotelma.
Oxygen and CO2 exchanges between water-® lled leaf axils and the atmosphere proceed as if the same contents resided in comparable arti® cial receptacles. Shoot size and shape and environment to the degree that
photosynthetic photon ¯ ux density (PPFD) in¯ uences sun vs. shade
morphology (Fig. 4.23B,C) largely determine the volume and con® guration of plant-created habitat and consequently the kinds and quantities of
the resources likely to accumulate there. Characteristics like leaf coloration
in¯ uence carrying capacity for certain residents to the extent that they
reduce predation (Figs. 2.14G, 2.17B). The availability of potential stock
sometimes also shapes the composition of the bromeliad-based community. For example, despite substantial native Odonata, none of the local
species uses bromeliads to reproduce in Florida (Frank 1983).
Virtually nothing is known about the optical properties of the bromeliad
shoot beyond those concerned with photosynthesis (Chapter 4). Closer
inspection might con® rm the presence of some other leaf functions. For
example, do the darkly pigmented leaf bases of certain species (e.g., Vriesea
erythrodactylon; Fig. 2.18D) help hide like-colored residents? Might the
uneven distributions of chlorophyll and anthocyanins of some relatives
(e.g., V. fosteriana; Fig. 2.14G) blur the outlines of lighter-colored prey?
Padro Nauum (personal communication) examined about 100 plants each
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Phytotelm bromeliads
455
Figure 8.14. Diurnal ¯ uctuations in the concentration of dissolved CO2 in the
central tank of juvenile Aechmea bracteata and beakers containing the same materials (after Benzing et al. 1972).
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Relationships with fauna
of a variegated and a concolorous form of an Aechmea hybrid being propagated for sale in his nursery near Rio de Janeiro. A single unidenti® ed
species of frog, one per plant, inhabited about 10% of the former and none
of the latter specimens. However, the same fertilization used to promote
leaf color also caused the variegated plants to develop a more compact and
perhaps more alluring shoot. Several other growers in Brazil also report
that bromeliocolous frogs prefer plants with variegated foliage. Sharp
spines and compact shapes appear to promote plant use as well.
Certain ornamentations may persuade fauna to pursue other kinds of
relationships with Bromeliaceae. Conspicuously marked shoots of some
taxa (e.g., red leaf tips on a number of Neoregelia species; Figs. 2.13F,
2.18A) could parallel those of the Neotropical gesneriads (e.g., Dalbergia)
whose orange and red-blotched foliage supposedly reminds the local pollinators of their presence between ¯ owering seasons. However, many of the
most impressively variegated bromeliads (e.g., Vriesea fosteriana and V.
hieroglyphica; Fig. 2.14G) ¯ ower at night, attract bats, and subsequently
ripen dry fruits and seeds. Whether or not these ornamentations affect
plant/animal relationships, they certainly impact photosynthesis (Benzing
and Friedman 1981). Transitory coloration associated with pollen and seed
dispersal is discussed in Chapter 6.
Litter processing
Those detritivores that Paoletti et al. (1991) reported at higher densities in
the shoots of certain Bromeliaceae than in subjacent soils contribute to a
process crucial for plant success (Fig. 8.15). In less than the 2± 3-year lifetime of the typical ramet, resident biota transform impounded litter into
® ne-textured, humic soil. Psidium sp. foliage enclosed in nylon mesh bags,
and incubated for just three months in the axils of Aechmea filicaulis and
Vriesea splendens in the same cloud forest in northern Venezuela, lost
21± 27% of its initial weight, as did a second set of samples buried in the
ground beneath the host trees (Paoletti et al. 1991). Surveys (e.g., Naeem
1990) conducted on larger-scale, better-known aquatic systems suggest how
most phytotelm bromeliads rely on processors housed in leaf axils to accomplish this transformation and extract nutrients from intercepted litter.
Three groups of organisms assist one another when feeding on the litter
that constitutes the trophic base for heterotrophic forest stream communities (e.g., Cummins et al. 1989). Microbes, particularly hypomycetes and
saprophytic bacteria, initiate the breakdown process by chemically altering
structural polymers and weakening the integrity of waterlogged foliage and
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Phytotelm bromeliads
457
Figure 8.15. Densities of extractable microfauna in contents of epiphytic bromeliad
shoots, suspended humus, and in rotten wood and soil/litter on the ground. The wet
site is cloud forest located along a ridge line (~1000 m) at Rancho Grande, northern Venezuela; the dry site is in seasonal woodland several hundred meters over the
leeward side of the same ridge (based on data collected by Paoletti et al. 1991).
wood. A second group of arthropods known as the `shredders' (primarily
amphipods, isopods, caddis¯ y, may¯ y, midge, and certain Diptera and
beetle larva) produce even ® ner fragments (mostly feces and uningested
fragments ,1 mm) from the bioconditioned, larger particles. A third group
of mostly ® lter-feeding microinvertebrate `collectors' that includes many
mosquito larvae subsist on the resulting particulates.
Breakdown rates vary with the source. Especially recalcitrant foliage
incubated in mesh bags lost less than 0.01% of its initial dry weight per day;
more labile (digestible) foliage disappeared at .0.15% per day (Cummins
et al. 1989). Unfortunately, checklists of invertebrates enumerated in the
surveys of bromeliad shoots lack the resolution reported for the betterstudied lotic ecosystems. However, judging by the numerous nonpredatory
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Relationships with fauna
Cullidae and direct litter feeders reported in bromeliad tanks, saprophytes
and shredders probably operate there as well.
The time required to mobilize plant nutrients in the phytomass
impounded in a bromeliad shoot appears to vary according to the element,
characteristics of the source, and a host of environmental circumstances,
most notably the identities of the processors. Climate also plays a crucial
role; leaf axils dry out for months each year among the relatively drygrowing forms (e.g., Tillandsia flexuosa in south Florida), but others
remain ® lled permanently like those of Guzmania weberbaueri monitored
by Krügel (1993) in Amazonian Peru. Clearly, possession of phytotelm
architecture does not guarantee continuous as opposed to pulse-supplied
status for the bromeliad with a strictly mechanical root system (Chapters 4
and 5; Zotz and Thomas 1999).
Guzmania monostachia growing in a Florida swamp forest indicated that
at least the ramets of this bromeliad at one site cycle too quickly to permit
plant access to large fractions of the more refractory elements sequestered
in impounded litter (Table 5.8). Humus collected from its leaf bases contained substantially more Kjeldahl N than K compared with the usual concentrations of these elements in mature, living tree foliage (between 1:1 and
1:2). Phosphorus merits special attention as an element that often occurs in
even shorter supply for tropical forest ¯ ora.
Agencies beyond the life span of the hosting ramet help determine how
much of the nutrient capital delivered in impounded litter ends up supporting plant growth instead of other organisms residing in the same phytotelmata or exits the system altogether. An emigrating detritivore deprives the
plant of the nutrients incorporated in its body, as does the animal taken by
a visiting predator. However, fauna that spend even part of their lives using
the bromeliad release useful nutrients during that interval. Impact on the
balance sheet just happens to be less favorable for the plant when the animal
is removed before what would have been its more timely voluntary departure. Resident predators contribute somewhat differently to plant nutrition
depending on their diets and foraging patterns.
In addition to the frogs, centipedes, scorpions and other relatively mobile
carnivores that associate with bromeliads, additional, more obscure and
slower movers also import nutrients for plant use. Gastropods that hide by
day in the moist cavities provided by the phytotelm bromeliad emerge at
dusk to feed on nearby vegetation. Those cyanobacteria noted in
Ecuadorian bromeliads (Bermudes and Benzing 1991) bene® t the system as
scavengers of another type. Conversely, denitri® ers and certain other mediators of the N cycle might diminish the fertility of a phytotelmata. Heavy
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Bromeliads and the definition of soil
459
rains almost certainly affect the ledger by washing out nutrients before the
bromeliad can absorb them (Table 5.15).
A ® nal point concerns global change. Tropical forests generate nitrogen
oxides that molecule for molecule exceed CO2 many fold as radiatively
active (greenhouse) gases. Resident Bromeliaceae probably represent too
small a component of such systems to warrant concern as major contributors, but if present, important processes might be more practically studied
in these relatively self-contained microcosms than on broader scales.
Phytotelm bromeliads are de® nitely useful for surveillance. Monitoring
could determine whether changes in the atmosphere or local climate are
altering the phytotelm community in ways that portend impacts with
broader consequences (Lugo and Scatina 1992).
Enhancing the utility of these microcosms as biosensors is the exceptional vulnerability of the hosting bromeliads, particularly the epiphytes..
Canopy-anchored ¯ ora in general react with unusual sensitivity to humidity, PPFD and temperature along both horizontal and vertical gradients ±
sometimes within the same tree crown (Figs. 7.11, 7.12, 7.15). Aspects of
carbon and water relations (e.g., CAM) obliged by relatively harsh substrates and frequent drought in arboreal habitats reduce niche breadth for
many epiphytic plants (Benzing 1998; Chapter 4). Moisture impounded in
leaf bases moderates climate somewhat for the phytotelm bromeliad, but
judging by the narrow altitudinal distributions of many of the montane
species, not substantially so. Indumenta that in¯ uence gas exchange
differently depending on the moisture regimen further reduce the ecotolerances of Type Five bromeliads (Fig. 4.11).
Bromeliads and the definition of soil
Temperate zone ecologists tend to de® ne soil in rather parochial terms
because so often they fail to appreciate how similar media build up in the
canopies of humid tropical forests. By physical and biological characteristics, these suspended substrates represent arboreal extensions of the upper,
organic horizons of the `earth soil' located below (Nadkarni 1981, 1984;
Lavelle and Kohlmann 1984; Paoletti et al. 1991). Both resources contain
abundant plant nutrients, and support active roots originating from the
supporting trees and their epiphytes. Important soil phenomena like N2 ® xation and mineralization also characterize both compartments. Shared
biota, including an undetermined number of fauna that move between
them, make the case for a continuum even stronger.
Litter-feeding arthropods abundantly inhabit suspended humus, and
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Relationships with fauna
some groups occur at even greater densities in the shoots of epiphytic
Bromeliaceae. Palacio-Vargas (1982), working with mites from 22 families
in a Mexican forest, observed certain species exclusively in the canopy,
others only in earth soil, and a third group seemingly at home at both locations. Shoots of an unidenti® ed Tillandsia harbored 18 Collembola taxa,
some only during the wet season. Thirteen more species never left the
ground. Factors underlying the greater tolerances of the bromeliad-inhabiting populations were not obvious, and no attempts were made to identify
them.
Paoletti et al.' s (1991) survey in northern Venezuela demonstrated that
the diversity of soil-type invertebrates in bromeliad shoots can equal, and
sometimes exceed, that in subjacent earth soil (Fig. 8.15). Moreover, detritivores and scavengers occurred in about the same proportions in both
compartments, with only slightly higher values for predators on the
ground. Density peaked in the canopy, sometimes reaching 10-fold those
values recorded for comparable volumes of earth soil. In essence, the local
bromeliads represented `hot spots' of invertebrate diversity and abundance.
Plentiful detritus and high humidity at both locations probably account for
the similarities between these two communities.
Similar media on the ground and in the canopy raise questions about resident fauna, and whether Bromeliaceae sometimes in¯ uenced the evolutionary histories of some of these symbionts. Speci® cally, how many of the
detritivores that inhabit suspended soils or bromeliad shoots acquired
dietary, life cycle or other de® ning characteristics above ground? More fundamentally, what kinds of features distinguish related arboreal and terrestrial biota differentiated for life in one kind of space exclusive of the other?
Are any of the similarities convergent, or do fauna share certain features
through common origins?
Geology and paleoclimate undoubtedly in¯ uenced the amount of
exchange that occurred between the residents of these two compartments.
Long before the late Tertiary, humid tropical conditions prevailed more
widely than today. How much of this history is re¯ ected in extant taxa?
How many of these populations span the two compartments and routinely
migrate between them? To what extent do the bromeliads help blur the distinctions between canopy and earth soils today, and have they in¯ uenced
those characteristics that differentiate the more substrate-speci® c fauna?
Fragoso and Rojas-Fernández' s (1996) study of earthworms illustrates just
one of the many possibilities.
Fragoso and Rojas-Fernández encountered four species of earthworms
in the shoots of Androlepis skinneri and Aechmea mexicana in the canopies
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Figure 8.16. Abundance of the earthworm Eutrigaster sporadonephra in epiphytic
Aechmea mexicana and Androlepis skinneri in tropical rainforest in southeastern
Mexico (after Fragoso and Rojas-Fernández 1996).
of seasonal rainforest in southern Mexico. Of these, only Eutrigaster sporadonephra was absent on the ground except for the occasional individual
located in a large rotten log. Both bromeliads were used unevenly, with scattered shoots accounting for inordinate numbers of worms in accordance
with the capacity of these detritivores to migrate in search of mates and
superior habitat (Fig. 8.16). Large bromeliads probably attract the most
animals because they contain litter that remains continuously moist.
Unlike most of the earthworms native to tropical forests and savannas,
which tend to reproduce only during the wet season, Eutrigaster sporadonephra does so continuously, perhaps aided by the everwet conditions
afforded by phytotelm bromeliads. Similar densities of animals during the
rainy and dry seasons further indicated that arboreal Bromeliaceae provide
permanent refuges rather than temporary heavens during dry weather as
reported for the arthropod fauna of some Tillandsia species in central
Mexico (Murillo et al. 1983).
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Fragoso and Rojas-Fernández proposed two, somewhat overlapping
hypotheses to explain the near complete restriction of Eutrigaster to arboreal bromeliads in southern Mexico. As epigeic species (residents of the
upper layers of soil), members of this genus mostly occupy continuously
humid habitats where the well-aerated, moist space these animals require is
always available on the ground. Seasonal habitats present problems because
litter tends to accumulate during the driest months when these worms can
least use it, while wetter periods see much of that forage disappearing.
However, the bromeliad shoot provides moisture and food on a more
dependable schedule, and hence constitutes a superior resource that the
worms prefer over soil in marginally humid habitats.
The second hypothesis factors in two additional provisos: recent arrival
in North America across the current land bridge with South America and
litter-dependence as a phylogenetic constraint. Eutrigaster has clear
Gondwanian affinities, and north of Costa Rica most of its terrestrial representatives inhabit cool pine± oak forests where they thrive in the soil litter
layer like all of the other epigeic earthworms. Below about 1000 m, populations consistently inhabit bromeliad tanks or large rotten logs, as if
obliged to do so by conditions that routinely render the understory too
hostile (dry) for such vulnerable detritivores. This pattern suggests that
Eutrigaster spp. dispersed northward over the last 3± 4 million years
through cool montane forests, and subsequently invaded lowland communities by way of the bromeliads that provide substrates resembling those on
the ground at higher elevations. Finally, Eutrigaster sporadonephra remains
a bromeliad specialist in tropical Mexican forest by virtue of its basic
epigeic nature that to date has precluded accommodation to seasonal
drought.
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9
History and evolution
D. H. B ENZ ING, G. B ROWN AN D R. TERRY
Although evolution is the theme that ties this volume together, until now
adaptive aspects of phenotype such as CAM, the phytotelm shoot and the
absorbing trichome have dominated discussions. Times, places and why
these features emerged during Bromeliaceae radiation have received far less
attention. At this point, we switch emphasis to beginnings and circumstances that in¯ uenced the adoption of those characteristics that de® ne
much of the family as exceptional for adaptive novelty and importance in
communities. Fossils, ontogeny, phytogeography, paleoclimate, cytogenetics and the structure of the genome provide insight on the geologic history
and phylogeny of Bromeliaceae and point out directions for additional
inquiry.
Phylogenetic analysis informed by the molecular structure of key segments of DNA and a fuller understanding of the morphology and adaptive biology of representative species will eventually reveal the identities
and dates of the major evolutionary events responsible for the distinctness
of the more advanced Bromeliaceae among Magnoliophyta. Conditions in
primordial habitat(s) head the list of enduring questions: were these sites
dark and humid like the forest understory or exposed and dry? More fundamentally, did scarcities of mineral nutrients or drought play the more
decisive roles in the evolution of the foliar indumentum and phytotelm
shoot? Heterochrony has also ® gured prominently in speculations about
bromeliad radiation, but without much thought given to the incentives
(plant bene® ts) responsible for this process.
A framework that arrays extant lineages in evolutionary space and geologic time (cladogram) will also resolve long-standing disagreements about
taxonomy. For example, should Brocchinia in one instance, and Catopsis
and Glomeropitcairnia in another, remain aligned within two of the three
currently recognized subfamilies (sensu Smith and Downs 1974, 1977,
463
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1979)? On another note, just a handful of characters, many of questionable
value, distinguish the core bromelioid genera (e.g., Aechmea, Neoregelia,
Nidularium). Similar problems prevail in Pitcairnioideae (e.g., the boundary between Pitcairnia and Puya and the likely arti® cial nature of Navia)
and Tillandsioideae (e.g., how many genera should be recognized within
Vriesea and Tillandsia?). More broadly, should the three subfamilies of
Smith and Downs be replaced by a larger number of taxa of similarly high
rank?
Presumably, taxonomic revisions consistent with cladograms constructed with data from multiple DNA sequences will more accurately demonstrate evolutionary relationships within Bromeliaceae than are depicted
in any of the existing systems. Likewise, these frameworks should reveal
which one of the several candidates already proposed is indeed the sister
group of the family, and point out where the bromeliads belong within
Liliopsida. More immediate to our goal, an evolutionary taxonomy will
permit meaningful organization of the information on plant structure,
function and related ecology summarized in the preceding eight chapters.
Fossils
Fragments of foliage, one ¯ ower and some pollen comprise the reported
geologic record for Bromeliaceae (e.g., Gómez 1972; Smith and Downs
1974). Some of these assignments cannot be taken seriously. Poorly preserved leaves described as Bromelia tenuifolia from the Dakota Formation
in Kansas constitute one of the two described New World macrofossils, and
venation suggests closer affinity to the cycads. Four more binomials were
established for organs discovered in Europe. Among these,
Bromeliaceophyllum rhenanthum and B. oligovaenicum from Upper
Oligocene (,20 million years ) brown coal deposits in Germany lack the
distinctive epidermal features needed to con® rm family affiliation.
Bromelianthus heuflerianus from the Eocene (,40 million years ) of Italy
bears four rather than three-merous ¯ owers (an occasional condition in
Dyckia), and it belongs to a poorly preserved ¯ ora containing additional
remains no more persuasively assigned to Orchidaceae (Schmid and
Schmid 1977).
Gómez (1972) described foliage with more convincing morphology from
36 million-year-old sediments in the San Ramon region of Alajuela
Province, Costa Rica. Karatophyllum bromelioides bears marginal spines
and prominent impressions of peltate trichomes. However, microfossils
offer the greatest opportunity to track Bromeliaceae through geologic time
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465
because most of the family' s lowland members grow in the forest canopy,
or, if terrestrial, occupy nonsedimentary environments. A. Graham (personal communication) reported two types of Tillandsia-like pollen from the
late Eocene Gatuncillo formation of Panama. Authorities familiar with
extant material should examine his ® ndings and also seek signs of
Bromeliaceae in the growing number of samples coming on-line from other
Neotropical sites.
An exceptionally poor fossil record combined with the almost complete
restriction of ,2700 species, many with wind-dispersed or endozoochoric
seeds, to tropical America argues for a youthful Bromeliaceae. Quite likely
the family became distinguishable during the early mid-Tertiary ± sometime between 40 and 65 million years . But if this is true, then we face the
question of why Pitcairnia feliciana exists as the sole transatlantic vicariant
(Fig. 1.1). Pitcairnia glaziovii with similar ¯ owers occurs at about the same
latitude in eastern Brazil (Leme and Marigo 1993). However, foliage with
pronounced armature (Fig. 2.12E) and a generally xeromorphic character
suggests closer affinities between P. feliciana and certain Caribbean populations.
More vexing than questions about relationships among extant
Bromeliaceae is why, if just a single member colonized Africa, does it
belong to one of the more ill equipped of the .50 genera to travel so far?
Additionally, why did this event take so long to occur, and then happen just
once, or at least involve just one lineage? Perhaps dispersability was less
decisive in shaping family insularity than some other aspects of natural
history. Infrequent naturalizations (Chapter 7; Nelson and Zizka 1997)
despite widespread use in anthropogenic landscapes suggest that
Bromeliaceae generally lack the invasiveness of many other plants. In any
case, molecular systematics could help determine whether Atlantic sea¯ oor spreading stranded P. feliciana, or con® rm the more probable explanation that this taxon holds the family record for what appears to be a rare
accomplishment, namely colonization across a wide oceanic barrier.
Phytogeography
Plant distributions often suggest where evolutionary radiations occurred,
and which conditions of land form and geologic history and soil and
climate favored speci® c events. Explanations for why one clade proliferated
more or less than others in a given region require additional information
on reproductive biology and ecology (e.g., the types of breeding systems
present, predisposition for cladogenesis via possession of propitious
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History and evolution
features like CAM in arid regions). Smith (1934a) recognized three centers
of what he called `family development' and some secondary sites where a
genus or a cluster of allied genera supposedly achieved current diversities
and distinguishing characteristics.
Tillandsioideae, and to a lesser extent Pitcairnioideae, exhibit highest
densities of genera and species, including some of their reputedly more
primitive lineages, in the geologically young northern Andes (Tables 1.3,
1.4). Dozens of closely related and often ecologically similar members of
Guzmania, Pitcairnia and Tillandsia, among other lineages, co-occur in the
everwet, low montane forests of southwestern Colombia and northern
Ecuador. Bromelioideae demonstrate comparable clustering through
similar and drier ecosystems in southeastern Brazil, mostly on soils derived
from some of South America' s oldest rocks (e.g., Fig. 1.4C). More genera
of Pitcairnioideae occur in the Guayanan highlands than in any other
region, although species more densely pack considerably smaller areas elsewhere (e.g., Pitcairnia in Colombia and Ecuador).
Pitcairnioideae
Although some 275 pitcairnioid species and nearly half of the genera reside
in the Guayanan highlands, six nowhere else, little evidence besides the
molecular data that place Brocchinia at the base of Bromeliaceae indicates
that Andean habitats were stocked from this direction (Steyermark et al.
1995; Terry et al. 1997a; Fig. 9.1). Most Pitcairnioideae endemic to these
ancient, highly weathered substrates resemble evolutionary relics (e.g.,
Brewcaria, Connellia). The larger taxa (e.g., Navia) also show signs of protracted stasis, but additionally much recent, low-level radiation fostered by
impoverished substrates and deeply dissected topography within a Tertiary
refugium (see below). Distinct populations sometimes occupy one or a few
isolated tepuis as if the products of infrequent seed dispersals among
widely scattered land islands. Puya suggest that little exchange has occurred
in the opposite direction. Those few species with Guayanan representatives
number among the few wide-ranging types (e.g., P. floccosa). Local
Bromelioideae (e.g., Aechmea nudicaulis, A. tillandsioides) and
Tillandsioideae (e.g., Vriesea platynema, Tillandsia complanata) mostly
also occur well beyond the Guayanan Shield.
Other Pitcairnioideae exceed the Guayanan endemics for ¯ oral specialization (e.g., dioecious Hechtia), and a larger number of species at least
match them for lithophytism, leaf succulence and the presence of CAM
(Table 4.2). Predominantly Mexican Hechtia far to the north, and
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467
Figure 9.1. Distribution of tepuis and additional highland habitats at lower elevations across the Guayanan Shield. The Rio Caura separates the eastern from the
western regions.
Encholirium, Dyckia and allied, smaller genera in southeastern Brazil and
Bolivia (e.g., Abromeitiella, now Deuterocohnia), constitute secondary radiations far from what Smith (1934a) presumed to be the primary ancestral
habitats. Similar structure and frequent interfertility within Dyckia and
Encholirium suggest recent speciation encouraged by conditions peculiar to
certain elevated habitats (e.g., campos rupestres; Fig 1.4C; Chapter 7) and
¯ uctuating Plio-Pleistocene climates that displaced and fragmented life
zones. Pitcairnia range most widely among the genera owing to an
unmatched ability to accommodate hot, humid climates and shade and
perhaps disperse long distances via rivers. Less varied Puya feature a more
generalized ¯ ower, and the genus' s mostly well-differentiated 185 or so
species usually occupy cool, arid to boggy habitats.
Puya illustrate evidence of vicariance about as persuasively as any bromeliad genus. Adjectives that describe the dispositions of the genus' s
species in addition to Andean include widely disjunct and narrowly
endemic. Varadarajan (1990) proposed 11 centers of diversity, each containing 5± 40 species arrayed from northern Colombia to north central
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History and evolution
Figure 9.2. Geographic locations of centers of diversity of Puya (after Varadarajan
1990).
Argentina (Fig. 9.2). Moderate to high-elevation habitat (800± 5000 m)
applies in all but one instance. Exceptional center number 11 nestles in
central Chile and features mostly coastal desert habitats except for some
sites in the adjacent highlands that rise to approximately 2000 m. About
75% of the Puya species occur in one or more of these 11 locations.
Monophyletic clusters of taxa, like the seven-member P. tuberosa
complex, typically occupy widely separated ranges in several of
Varadarajan' s diversity centers. Sympatric species tend to be paraphyletic
or polyphyletic, i.e., represent different radiations within the genus. Related
arrays of species also indicate that thermal constraints limited vertical speciation unevenly. A large group of allied lineages native to paramo lack
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469
close relatives at lower elevations, whereas the ancestors of species that
reside in puna habitats, primarily in Peru, Bolivia and Argentina, also
spawned descendants adapted for cool, tropical sites. Elevation separates
members of several pairs of sister species within this second group (e.g., P.
harmsii, 3000± 3600 m vs. P. lilloi, 800± 2000 m; P. weberbaueri, 2800±
4000 m vs. P. lasiopoda, 500± 2300 m). Additional information on Puya
radiation can be found in Chapter 7.
Varadarajan and Gilmartin (1988a) concluded from plant geography
and cladograms based primarily on morphological characters that
sufficient divergence and coherence among groups of taxa exist to warrant
recognition of three tribes among the genera of Pitcairnioideae (including
Pepinia, sensu Smith and Downs 1974; Fig. 9.3). Brocchinia was resolved at
the base of the entire assemblage as a `distinct lineage that diverged early
in the evolution of the subfamily' . Although arguably the most ecologically
and morphologically diverse of all the bromeliad genera, the exceptional
mix of characters responsible for this distinction occurs among fewer than
20 species all of which range exclusively through habitats associated with
the Guayanan Shield (Fig. 9.1).
Varadarajan and Gilmartin offered no comment on the suggested close
relationship of Brocchinia to Tillandsioideae (Benzing et al. 1985).
Pitcairnieae and Puyeae share several apomorphies along with novel suites
of identifying features. Only Puyeae ® ts Smith' s (1934a) proposed Andean
and pitcairnioid origin for Bromeliaceae as described later. Molecular data
derived from the chloroplast gene ndhF also place family origin in the
Guayanan region as indicated above and described in greater detail below.
According to Varadarajan and Gilmartin (1988a), all three pitcairnioid
tribes differentiated in the Guayanan highlands where Brocchinia and much
of Pitcairnieae (Ayensua, Connellia, Lindmania, Navia, Steyerbromelia) and
Brewcaria of Puyeae remain con® ned today. Later, deteriorating global
climate and Andean orogeny would foster conditions that promoted continued evolution among stocks of Pitcairnieae and Puyeae that had
migrated westward. Although many lineages would result according to the
pattern described for evolving Puya, ¯ owers and fruits would not diverge
enough to warrant recognition of more than a few additional genera.
Speciation at lower elevations produced the densest concentrations of
closely allied populations, for example about 50 Pitcairnia species in
Ecuador alone.
Current distributions suggest that much smaller (,30 spp.) Fosterella
radiated to accommodate mostly drier, low to mid-elevation (,2000 m)
habitats arrayed through west central South America (Ibisch et al. 1997).
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History and evolution
Figure 9.3. A 149-step cladogram based on morphological data that resolves the
major groups of genera in Pitcairnioideae into three groups. A± O represent hypothetical extinct ancestors of extant genera (after Varadarajan and Gilmartin
1988a).
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471
Diversity in this instance peaks in inter-Andean valleys centered in southern Peru where about half of the genus resides. The remaining species
occupy similarly modest, but usually nonoverlapping ranges. Central
American F. penduliflora constitutes the major outlier some 2000 km north
of its nearest relatives. Relatively uniform, primarily entomophilous
¯ owers further differentiate Fosterella from Pitcairnia/Pepinia (Fig.
3.4D,F± H,K± M). Failure to adopt a comparably plastic shoot architecture
probably also accounts for the disparate sizes of these two groups. Seed
characteristics that affect dispersability and capacity to accommodate seasonal or continuous supplies of moisture differ less.
More genera (Deuterocohnia, Dyckia, Encholirium, Hechtia, Puya) represent Puyeae than Pitcairnieae beyond the proposed source area in the
Guayanan highlands. Ancestors migrating from northern South America
positioned Hechtia farthest poleward in the northern hemisphere, largely in
Mexico. Similar differentiations in the central Andes produced several
more genera, some narrowly endemic (Abromeitiella, now Deuterocohnia)
and others (Encholirium, Deuterocohnia, Dyckia) more dispersed and even
farther removed from ancestral habitats in southeastern Brazil and adjacent northeastern Argentina.
Some taxa, like Abromeitiella, probably arrived via the Andean cordilleras already equipped by ecophysiology and a miniaturized Puya-like habit
for windswept high altitudes and membership among the cushion ¯ ora of
that region (Fig. 2.20). Amazonia perhaps provided a second corridor for
the migration of lowland types, especially if drier, cooler intervals beginning during the late Tertiary indeed periodically favored savanna over dense
forest. Pitcairnia sensu lato, which includes over 250 species in sites from
Mexico to Argentina, represents the product of the largest of the radiations
in Pitcairnioideae. Paradoxically, relatively few of these populations contribute to the massive bromeliad ¯ ora of southeastern Brazil, whereas
Dyckia and Encholirium radiated extensively there.
Brocchinia
Brocchinia warrants special consideration among Pitcairnioideae owing to
its phylogenetic isolation and geographic con® nement to one of South
America' s two oldest land surfaces. Extensive data on distribution,
morphology, physiology and ecology for what until recently was one of the
least-studied bromeliad lineages now provide unmatched opportunity to
reconstruct the history of a clade that in important respects parallels the
radiation of the entire family (Givnish et al. 1997). Speci® cally, members of
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History and evolution
Brocchinia possess the same two characteristics (the absorptive trichome
and phytotelm shoot) that fostered far more extensive ecological revolutions (more resultant species and adaptive strategies) in Bromelioideae and
Tillandsioideae. Epiphytism also occurs in at least two Brocchinia species,
aided there, as in the other arboreal Bromeliaceae, by one or both of these
same two adaptations.
Crucial to the following analysis of Brocchinia is the chloroplast DNA
(cpDNA) restriction site map that provides a historic framework to order
the pertinent information on Brocchinia structure, function and ecology
(Fig. 9.4). Fundamental to Givnish et al.' s (1997) scheme is the putative
existence of four monophyletic segregates within the genus minus B.
serrata, which probably constitutes a monotypic genus (Holst, personal
communication; Fig. 9.5). Future additions (including an undescribed population of ,5 cm adults and reassignment of Ayensua; Holst, personal
communication) to Brocchinia and more DNA sequence data could alter
this pattern somewhat.
Geographic/geologic information germane to bromeliad evolution
beyond the legendary con® nement of certain Brocchinia to one or a few of
the isolated, ancient, Guayanan sandstone towers includes the conditions
of rooting media (Fig. 9.1). Tepuis that rise above about 800 m subject the
vegetation growing on their summits to cool wet climates, which along with
base-poor parent rock assure impoverished, acid soils. However, the tepuis
located in the east, primarily in the Gran Sabana of Venezuela and adjacent Guayana, differ from those farther west in being horizontally bedded,
and consequently more deeply weathered and infertile, and thus especially
conducive to the evolution of specialized modes of plant nutrition.
Accordingly, Brocchinia includes members capable of supplementing
meager supplies in soil with key ions from prey, nests of plant-feeding ants,
and detritus impounded in phytotelm shoots that may also host substantial
colonies of N2-® xing cyanobacteria (Givnish et al. 1984; Figs. 1.2B, 2.2E,
2.4F). The other species, in fact more than half of the total, continue to rely
on root systems and soil (Figs. 1.2B, 5.3D), as do certain members of
Fosterella, which judged by the restriction site data is the genus closest to
Brocchinia.
Considerable data suggest that the stock antecedent to Brocchinia ranged
through what today is southwestern Venezuela and adjacent parts of
Colombia and Brazil that lie over the same Precambrian basement (Fig.
9.1). However, habitats were lower and growth was unassisted by unusual
ecophysiology, including carnivory. Instead, architecture paralleled that of
the least specialized of the modern descendants (e.g., root/shoot ratios
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Phytogeography
473
Figure 9.4. Resolution of four clades of Brocchinia species according to cpDNA
restriction site data (after Givnish et al. 1997).
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History and evolution
Figure 9.5. Reconstruction of ecological evolution in Brocchinia in relation to the
presence of phytotelm shoot (gray shaded bars), key landscape of eastern/central
tepuis (bar), and rise to ecological dominance and widespread geographic distribution (dashed rectangle). Uncertainty as to whether the phytotelm shoot arose independently in B. paniculata and the ancestor of the micrantha/reducta clade, or in
their common ancestor, is indicated by a lighter shade of gray. Three out of four
species equipped with specialized mechanisms to capture nutrients also exhibit ecological dominance and widespread geographic distribution (after Givnish et al.
1997).
comparable to those of many other rhizomatous monocots, no phytotelma). Trichomes may have possessed absorption capacity based on the
evidence and according to the logic described below.
Subsequent radiations, four in all according to the restriction site map
(Figs. 9.4, 9.5), took several directions ± in three cases toward specialized
nutrition to compensate for infertile soil. Presumably the clade represented
exclusively by B. prismatica and the entire B. melanacra cluster (also B.
amazonica, B. cowanii, B. maguirei, B. paniculata and B. vestita), except for
tall, palm-like and tank-forming B. paniculata, diverged less from the antecedent architecture than members of the clades represented by B. micrantha and B. reducta. Several conditions, including the associated phytotelm
and arborescent morphologies, evolved repeatedly, and then less frequently
disappeared (e.g., low-statured B. steyermarkii; Fig. 9.5).
The more ecologically conservative, saxicolous/rupestral Brocchinia
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Phytogeography
475
species (e.g., B. delicatula) tend to occupy restricted ranges, often at low elevations, perhaps con® ned there by competition with many other plants,
including some Pitcairnioideae (e.g., Navia), adapted to the same climates
and rocky substrates. Gigantism in B. micrantha and B. paniculata and
some populations of B. tatei stands in stark contrast to the miniaturization
illustrated by otherwise unspecialized B. cataractarum, B. delicatula and
especially the undescribed population just mentioned. Myrmecophily, as
well as carnivory and the other modes of soil-free nutrition facilitated by
phytotelm shoots, apparently emerged after antecedents penetrated higher
elevations where temperatures and rainfall selected for the predisposing
shoot architecture, viz. impoundments such as those featured by B. reducta
(Figs. 2.4F, 9.5). Nutrient-poor substrates, especially in the east, would
promote the evolution of dense indumenta comprised of large absorbing
trichomes to complement the shoot morphology associated with carnivory
and ant-feeding in Brocchinia (Chapter 5; Figs. 2.5A± D, 5.2E± G).
Following establishment of capacity to access supplemental sources of
ions, Brocchinia acuminata, B. hechtioides, B. reducta and B. tatei probably
colonized additional tepuis, and the most versatile species (B. acuminata,
B. reducta) also migrated to lower elevations across the Pantui to become
the most wide-ranging members of the genus. Epiphytism (facultative)
would also require wet forest as it still does (B. hitchcockii, B. tatei) and the
¯ ared shoot with channeled foliage suited to utilize impounded litter (Fig.
1.2B). Gigantism was probably encouraged by competition for light in
forest gaps, a challenge similarly addressed by many palms with their tall
unbranched shoots equipped with spreading crowns of relatively inexpensive pseudobranches. Brocchinia melanacra demonstrates that the occasional relative without a tank may also occupy a broad range, in this case
across much of the region occupied by the genus, possibly aided at some
locations by structure that promotes immunity to wild ® re.
Little imagination is required to visualize the likely origin of the phytotelm shoot assuming some rosulate stock, or the importance of abundant
rainfall to allow such a device to replace absorptive roots. Speculation
about plausible pathways to an epidermal trichome that mediates nutrition
from a foliar phytotelmata requires some thought about plant surfaces.
Epidermal appendages perform many tasks across Tracheophyta, including Bromeliaceae, depending on location on the plant, morphology, density
and physiology (Table 2.1). Moreover, functions within lineages shift as
other phenomena that impact the plant also change. Somewhere in the
history of Brocchinia, ancestors, like certain extant lineages (e.g., B. maguirei), possessed trichomes that provided service other than absorption.
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However, if that other function required living cells, then absorption was
an additional option, which as adopted in the state prevailing in
Tillandsioideae and specialized Brocchinia obscures evidence of the preceding service.
Many plant trichomes, including those with multiseriate, capitate organization (including Navia glandulosa; Fig. 2.5K), perform tasks that require
living cells. Secretion tops the list, the products including digestive enzymes
(some carnivores) and excess salt (some halophytes), but far more often
lubricating mucilages and toxic metabolites and adhesives to repel or neutralize small-bodied predators. Additionally, these activities usually peak
on young, relatively vulnerable surfaces (organs), consistent with visibly
precocious trichome maturation (e.g., recall the Syringa shoot tip illustrated in most introductory botany texts). Later, these organs often atrophy
as need diminishes, not unlike the sequence reported for Brocchinia reducta
(Givnish et al. 1984; Fig. 5.2E± G). On older parts of blades, well above the
phytotelmata, the absorptive hairs of this carnivore shrivel, but left intact
could provide no further nutritional bene® t anyway (Fig. 5.3C).
More importantly, cells comprising the secretory trichome necessarily
possess porous walls that perforce permit diffusable substances to penetrate
in addition to exit the leaf symplast. Should appendages with these characteristics also occur where shoot architecture promotes contact with nutrient-charged ¯ uids and rooting media are impoverished, evolutionary
opportunity and economic impetus exist to improve plant nutrition by
drawing on this alternative source. Absorptive scales among Bromeliaceae,
including certain Brocchinia, may have followed such a route, and quite
plausibly beginning before rather than after the phytotelm shoot evolved.
Almost certainly pitfall carnivory accounts for the extraordinarily high
densities of unusually large trichomes present on the foliage of B. reducta
compared with its myrmecotrophic and nonimpounding relatives (B.
reducta has 11.8% of adaxial leaf area occupied by trichomes, B. acuminata 6.7%, B. prismatica 3.8%, B. steyermarkii 0.4%; Givnish et al. 1997; Fig.
5.3E,F). However, absorptive capacity may have preceded the use of prey
and plant-feeding ants and quite possibly even the presence of a phytotelma (Table 9.1).
Why do certain nonimpounders (e.g., B. prismatica, B. vestita; Fig. 5.3D)
possess trichomes capable of accumulating solutes when the architecture of
the associated shoot affords the plant no obvious opportunity to exploit
this capacity for signi® cant nutritional bene® t (Table 9.1)? Two possibilities
come to mind. First, B. steyermarkii and certain other Brocchinia species
with similarly conventional architecture retain absorptive trichomes
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Table 9.1. Trichome area, density and affinity for 3H-leucine in relation to
ecological habit in Brocchinia
Species
Density
(mm22)
Leaf surface
occupied by
trichome
stalks (%)
Carnivores
B. reducta
B. hechtioides
194
236
11.8
5.9
Heavy
Moderate
Myrmecophyte
B. acuminata
88
6.7
Heavy
Tank epiphyte
(humus-based)
B. tatei
141
3.8
Little to none
Impounding tree
(humus-based)
B. micrantha
32
1.8
Little to none
Nonimpounding
terrestrials
B. prismatica
B. steyermarkii
B. cowanii
B. maguirei
B. melanacra
141
32
18
56
32
3.8
0.4
0.8
1.4
0.6
Heavy
Heavy
Not tested
Light
Not tested
Ecological habit
Labeling with
3
H-leucine
Source: Data for all but trichome function after Givnish et al. (1997).
despite the loss of tanks formerly present in ancestors (Givnish et al. 1997;
Fig. 9.5). Second, trichomes displayed by these bromeliads play no signi® cant role in plant nutrition now, nor did they do so at some earlier time.
Perhaps the foliar trichomes of Brocchinia prismatica and B. steyermarkii accumulate 3H-leucine and presumably additional solutes simply
because they happen to develop at a propitious location on the plant.
Possibly these trichomes soon die, their capacity to reduce thermal loads,
photoinhibition and transpiration unimpaired, if not enhanced, by this secondary condition, as for many other Pitcairnioideae (Fig. 2.8D). However,
while immature (and alive), near the basal meristem that produced them,
these appendages can absorb simple metabolites like amino acids that in
situ would never accumulate in sufficient quantities in leaf axils to promote
plant welfare. In effect, the assay with tritiated leucine revealed an artifact
± a phenomenon without ecological signi® cance for these plants. According
to the second possibility, this sort of activity would become important as
ancestors gave rise to increasingly leaf-dependent Bromeliaceae, speci® cally certain nutritionally specialized Brocchinia, phytotelm Bromelioideae,
and especially Tillandsioideae.
Typical monocots, by virtue of the way their leaves develop, are better
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disposed than the typical dicot to evolve modes of trichome-assisted, tankbased nutrition. However, just two Brocchinia and one Catopsis species
among Liliopsida have exploited this potential to the extent of evolving
carnivory. Members of additional families (e.g., Commelinaceae, Liliaceae,
Rapateaceae) parallel many more of the bromeliads in maintaining substantial supplies of moisture and detritus in in¯ ated leaf axils (i.e., they too
produce phytotelma and perhaps utilize litter as a source of nutrients).
Astelia species (Liliaceae) reputedly also possess absorbing trichomes with
peltate organization (Oliver 1930). Occurrences on substrates as impoverished as those supporting many Brocchinia might have promoted nutritional specializations in one or more of these nonbromeliad lineages as
well. Clearly, much work needs to be done to reconstruct trichome evolution in Bromeliaceae, including a more comprehensive survey of the structure and function of those organs serving primitive and more advanced
lineages in Brocchinia.
Bromelioideae
Bromelioideae concentrate in Brazil, particularly in the southeast, where a
majority of the ,800 species occur, many nowhere else (Leme 1997; Table
1.4). Rugged topography, diverse climates and ancient granitic and other
kinds of substrates suited for saxicolous and rupestral habits have favored
substantial divergence, often involving localized populations (e.g.,
Cryptanthus; Fig. 11.1). Atlantic Forest and the adjacent drier habitats have
been especially conducive to expansion, and they remain the homes of
entire genera (e.g., Canistrum, Cryptanthus, Nidularium, Orthophytum,
Quesnelia). Much larger Neoregelia (.90 species) exhibit the same insularity except for Amazonian subgenus Hylaeaicum (e.g., N. myrmecophila, N.
longisepala), which Ramírez (1994; Chapter 10) considers more closely
allied to Aechmea subgenus Lamprococcus.
Other genera (e.g., Aechmea, Billbergia) extend through much of frostfree America, but more often owing to the high mobilities of a few exceptional species (e.g., Aechmea nudicaulis) than to massive migrations or
secondary expansions remote from the center of subfamily diversity.
Terrestrial Bromelia (,50 spp.) probably owes its exceptional dispersal
among bromelioid genera to drought-tolerance and adaptation for low,
often coastal habitats. Ancestors that would initiate sizable (e.g., Greigia)
or smaller (e.g., Disteganthus, Fascicularia, Ochagavia) genera did migrate
west and northward, while some possible returnees (e.g., Hohenbergia,
Ronnbergia) modestly augmented diversity in ancestral territory. However,
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poorly resolved taxonomy complicates attempts to track the migrations of
Bromelioideae.
Several bromelioid genera exhibit geographic disjunctions that suggest
erroneous systematics rather than ancient or more recent long-range dispersals. Hohenbergia (,40 spp.), for example, occurs about evenly divided
between southeastern Brazil (subgenus Hohenbergia) and Mesoamerica
(subgenus Wittmackiopsis). More than a dozen members grow exclusively
in Jamaica, mostly on isolated, modest elevations in the western part of the
island. At least one more species also ranges into the mountains of Cuba.
Ronnbergia, a genus otherwise con® ned to northwestern South and Central
America where it probably originated, contains two southern outliers of
dubious taxonomic assignment in Bahia State in Brazil. Araeococcus and
Streptocalyx exhibit similar dispositions, and the Brazilian and perhaps all
the members of the latter genus probably belong to Aechmea (Smith and
Kress 1989; Smith and Spencer 1992).
Smith' s (1934a, 1962) suggested Amazonian beginning for
Bromelioideae accords with the high incidence of taxa in similarly warm,
humid habitats farther south, but little else. Whether or not he is correct,
conditions in Brazil' s southern coastal states, particularly Rio de Janeiro,
have promoted far more speciation and ecological variety. Several clades
(e.g., Neoregelia subgenus Neoregelia, Nidularium) populate Atlantic
Forest with numerous, little-differentiated and interfertile, often understory
species. Many members of Cryptanthus, Encholirium, Orthophytum and
Dyckia exhibit similar insularity as members of nearby rupestral ® eld communities. In fact, circumstances through this part of South America favor
unmatched bromeliad diversity ± in all, about 40% of the species representing three-quarters of the genera. Endemism involving all three subfamilies
further indicates how conducive conditions in the grasslands and rupiculous ® elds of Bahia, Minas Gerais and adjacent states have been for family
expansion.
Floras located on still other kinds of sites (e.g., campos do altitudes,
restingas and campinas, the white sand communities of the Amazon Basin)
contain far fewer, but sometimes locally abundant, species (e.g., Aechmea
nudicaulis, Neoregelia cruenta; Fig. 7.13C,E), many recruited from nearby,
¯ oristically older and more biodiverse forests. Closely related, if not ancestral, populations continue to inhabit some of these woodlands. Migrations
purportedly also explain the ranges and composition of Brazil' s southernmost bromeliad ¯ ora.
Topography, plant distributions and endemism persuaded Winkler
(1980) that numerous Bromelioideae representing Aechmea, Billbergia,
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Canistrum, Nidularium and Wittrockia accompanied members of Dyckia,
Tillandsia and Vriesea to colonize, or more likely repopulate, Rio Grande
do Sul State. Another set of Tillandsioideae with Andean affinities (representatives of subgenera Anoplophytum, Diaphoranthema, Phytarrhiza)
invaded southeastern Brazil from the west, whereas still other Tillandsia
and Vriesea species arrived through Winkler' s `coastal gate' , in effect the
maritime corridor that extends more or less southwest to northeast along
the Atlantic coast. Some of these arrivals probably date from the early
Holocene shortly after rebounding global temperature diminished the
threat of frost.
Few Bromelioideae (e.g., Fernseea, Greigia) occupy habitats as cool as
those supporting more extensively montane Pitcairnioideae (e.g., Puya)
and Tillandsioideae (Tillandsia, Vriesea), perhaps re¯ ecting conditions
experienced by ancestors in the Andes compared with those prevailing in
the lower, older topography of eastern South America and Amazonia.
Rossi et al. (1997) noted this differentiation in Costa Rica where native epiphytic Bromelioideae (Aechmea) compared with more diverse
Tillandsioideae, mostly inhabits lowland, moist habitats.
Bromeliad xerophytism exhibits a similar pattern. Despite near complete
reliance on CAM, Bromelioideae, except for the more succulent types (e.g.,
certain Bromelia, Neoglaziovia) may fall short for drought-tolerance compared with numerous species of Hechtia, Dyckia, Puya, additional
Pitcairnioideae and many Type Five Tillandsia. Conversely, no other part
of the family except certain Tillandsia so often colonizes rocks and tolerates salinity. Finally, several Bromelioideae (e.g., some Cryptanthus;
Neoglaziovia) and more Pitcairnioideae (e.g., certain Dyckia and
Encholirium; Figs. 2.2G, 6.12A,C± E) of the campos rupestres and similar
hyperseasonal ecosystems endure ® re better than any Tillandsioideae.
Tillandsioideae
Tillandsioideae range more widely than members of either of the other two
subfamilies (Fig. 1.1). Tillandsia usneoides holds the record for area colonized and long-range dispersal except for Pitcairnia feliciana on the second
count. Racinaea insularis grows exclusively on the oceanic Galapagos
Islands, and a small population of T. usneoides may be native to Bermuda.
Relatives such as Tillandsia fasciculata and T. paucifolia (members of predominantly Mesoamerican subgenus Tillandsia) that occur on many of the
Caribbean islands and deep into South America (e.g., T. juncea in southeastern Brazil) further underscore the mobility of the comose seed, and
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suggest that Bromeliaceae indeed emerged later than most of the other
sizable, primarily tropical angiosperm families.
Smith (1934a) chose Tillandsia to make his most detailed case that geographic distributions indicate the ages of clades still young enough to
qualify as genera, or monophyletic groups of component species (e.g., subgenera, sections). The total area occupied by such an alliance divided by the
smallest area necessary to include parts of the ranges of every component
population yields its so-called `cohesion ratio' . Use of the cohesion ratio to
reconstruct plant history requires a rather ® xed notion of how clades evolve
and eventually disappear (see Wiley (1988) for an update on centers of
origin and biogeography theory).
Basically, as a clade matures, the area occupied by its expanding membership presumably enlarges, and accordingly, so does the accompanying
cohesion ratio. Barring extinctions, this number increases as new populations continue to emerge farther from the center of origin, and the ranges
of the older ones remain static or contract. However, other dynamics
produce similar patterns. At issue here is Smith' s contention that biogeography re¯ ects the evolutionary history of certain bromeliad taxa more or
less independent of their environments and certain biological properties of
the constituent populations.
Clades expand to different sizes, and then erode at uneven rates for
poorly understood reasons, but the causes are numerous, interactive and
involve the inherent properties of the plants considered and their growing
conditions. Likewise, dispersability, ecotolerances and the distributions of
favorable habitat surely affect the dimensions of the areas populations
occupy through time. Small size (few species) may signal a relatively youthful clade ± an incipient radiation ± or extended stasis, just as a con® ned
range could re¯ ect recent origin, sedentary propagules, stringent requirements for growth or impending extirpation.
Glomeropitcairnia contains just two species, and exhibits no evidence of
ever having exceeded its current narrow range in the Lesser Antilles and a
few sites in adjacent northeastern Venezuela. However, novel ¯ oral, fruit,
seed and trichome morphology and the cpDNA data described below
suggest relictual status (no close extant relatives) whether or not the taxon
was ever larger. Greater similarity to core Tillandsioideae or some other
component of Bromeliaceae would accord with more recent origin.
Findings during the past decade that indicate probable paraphylesis for
several genera, including Tillandsia and some of its segregates (entire subgenera to inclusive clusters of species), further challenge Smith' s use of phytogeography to help reconstruct the evolutionary history of Bromeliaceae.
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Cohesion ratios can be useful to formulate questions about evolutionary
history and in¯ uential plant characteristics. For example, the least common
overlap for Tillandsia subgenus Diaphoranthema constitutes only a tiny
fraction of the total area occupied, primarily because T. usneoides and T.
recurvata range so widely, the ® rst species probably because of its tendency
to release buoyant fragments (Fig. 7.7C). Abundant self-set seeds and
extraordinary capacity to grow on diverse substrates may underlie the
nearly as expansive distribution of T. recurvata. However, a number of
close relatives with similar ecology and propensity for autogamy remain
quite insular, probably for reasons related to additional aspects of life
history peculiar to these populations.
Overall, the genera of Tillandsioideae probably exhibit less cohesion
than those of Pitcairnioideae in part because they produce wind-carried
rather than unappendaged seeds. Total and the least common areas for
Puya converge most in the southern Andes, reputedly because its members
share greater genetic identities there (Smith 1934a). However, differences in
the availability of habitats that can support groups of related species (e.g.,
expansive, cold plateau farther south) may be more in¯ uential.
Plant influences on geographic range
Ecotolerance and other aspects of plant biology affect the phytogeography
of certain Bromeliaceae. Compared with fundamentally cool-growing
clades like Puya, most members of Pitcairnia utilize more pervasive, warm
and humid ecospace that also features numerous seed-transporting waterways. Seed morphology and overoccurrence along streams further suggest
that hydrochory in¯ uenced dispersal by members of this genus. Climate
affects the distributions of many Tillandsioideae through constraints
related to plant architecture in addition to ecophysiology. Considerable
predominantly soft-leafed, tank-dependent Tillandsioideae occupy con® ned ranges in montane regions consistent with their relatively stringent
requirements for high humidity and perhaps moderate temperatures
(Chapter 4; Rossi et al. 1997).
Conversely, Type Five Tillandsia occur at high to low altitudes under
widely varying humidities. The lowland natives (e.g., T. balbisiana, T. schiedeana), which tolerate severe evaporative demand, range more broadly, in
part again because this kind of habitat occurs so extensively through tropical America. Species achieve high densities locally in both hot and cold
deserts, for example in Mexican thorn forests and in higher (.2000 m)
Andean sites. Cloud-dependent types (e.g., T. tectorum), although often
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common in favorable sites, exhibit greater insularity consistent with the vertically compressed (cloud zones) and horizontally dissected nature of their
montane habitats.
Excessive warmth and seasonal drought probably explain the relative
poverty of Amazonian Bromeliaceae compared with the adjacent highlands, but causes may vary with the taxon. Simple explanations such as the
absence of the cool nights supposedly necessary to foster vigorous CAM
lack currency (e.g., McWilliams 1974; Chapter 4). CAM characterizes
extensive Bromelioideae native to equally tropical sites elsewhere (e.g.,
Atlantic Forest). Similarly, CAM-equipped Tillandsia range from sea level
to above 3000 m in sites arrayed from Mexico to Argentina.
Conditions in the drier and most bromeliad-de® cient parts of Amazonia
(central and eastern regions) favor neither phytotelm (C3) nor driergrowing Tillandsioideae. Not many Bromelioideae or Pitcairnioideae occur
here either. Equally pronounced dry seasons at higher (cooler) elevations
to the west constrain the family far less, and certain Tillandsioideae
(Guzmania) and Pitcairnioideae (Puya, Pitcairnia) achieve unparalleled
diversities in pluvial Andean habitats adjacent to western Amazonia.
Perhaps Amazonia limits the possibilities for Bromeliaceae, and especially Tillandsioideae, more than most other regions inhabited by the
family because it offers fewer combinations of acceptable growing conditions. Most of the local bromelioids are epiphytes, and many possess
bulbous shoots that feature a well-protected phytotelmata and accommodate ant colonies in the drier recesses of the younger foliage (Fig. 2.4G).
Other species root in arboreal ant nests (e.g., Aechmea mertensii,
Neoregelia myrmecophila; Fig. 8.1C). Abundant moisture and heat during
the wettest months probably exclude Type Five Tillandsia for reasons
described in Chapter 4. Finally, monotonously low, compared with the
more dissected Andean and Guayanan, topography further militates
against diverse arboreal ¯ oras, but this constraint overlaps with the previous one.
A recent assessment (Ibisch et al. 1996) of Peruvian Bromeliaceae and
co-occurring families addresses three of the same questions just considered, namely: has epiphytism inordinately favored speciation; what can
phytogeography tell us about the evolutionary history of a clade and
whether characteristics of the membership in¯ uenced its size and range;
and why are the Amazonian bromeliads so few and similar in adaptive
type? Ibisch et al. concluded that epiphytism does not promote extraordinary rates of speciation (`abnormal evolutionary activity' ), at least not in
Peru. They also noted that epiphytes sometimes contribute substantial
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History and evolution
Figure 9.6. Occurrence of species representing different habits in dry, moist and wet
Ecuadorian forest (after Gentry and Dodson 1987).
diversity to local ¯ oras (up to 35%), but importance to species richness
diminishes as spatial scale increases.
Ibisch et al.' s conclusion about arboreal vs. terrestrial habits and speciation rests on evidence from plant geography, speci® cally that the obligate
bromeliaceous epiphytes of Peru (28.8% of the 452 species) range more
widely than the terrestrials (true also for Araceae, Orchidaceae and
Piperaceae). Endemism (i.e., con® nement of a species within the political
boundaries of Peru) is just 10.1% for the epiphytes of Bromeliaceae and
19.7% for those of Tillandsia, the largest of the Peruvian genera representing this family. Corresponding ® gures for the terrestrials are 76.6 and
87.5%. Because the authors equated insularity with evolutionary youth
(reminiscent of the logic behind the cohesion ratio), lineages with terrestrial habits were deemed more recently derived on average than those of the
related epiphytes.
Ibisch et al. consider the epiphytes to possess greater `ecophysiological
plasticity' and accordingly, less propensity to speciate in response to
growing conditions that diverge as ranges expand. Related terrestrials, they
say, instead `tend to ® ner niche-tuning' , which involves more `genetic separation and subsequent speciation' . In fact, regional patterns of epiphyte
diversity, including Bromeliaceae, show arboreal ¯ ora to be far more sensitive to climate than co-occurring soil-rooted shrubs, vines and trees
(Gentry and Dodson 1987; Benzing 1990; Fig. 9.6).
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Figure 9.7. Map of Peru indicating major life zones and associated diversities of
vascular epiphytes. Bromeliaceae represent about 8.5% of Peruvian epiphytes and
concentrate in lower montane rainforest as do their counterparts in Orchidaceae,
Araceae and Peperomia which constitute 78.0, 5.2 and 5.0% of the arboreal species
respectively (after Ibisch et al. 1996).
Conceivably, epiphytic Bromeliaceae exhibit relatively low endemism in
Peru because most of them reside (many sympatrically) in the everwet,
lower montane life zone that continues unbroken along the eastern slopes
of the Andes into Ecuador and Colombia at its north end and into Bolivia
to the south (Fig. 9.7). Species/area curves that demonstrate decreasing
importance to overall species richness for the epiphytes relative to the
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History and evolution
Figure 9.8. Generalized species/area curves of epiphytes and terrestrials in epiphyterich forest based on observations in Peru. Arboreal ¯ ora lose relative importance as
the size of the area considered increases (after Ibisch et al. 1996).
terrestrials accord with differences in average plant size and the related tendency for arboreal ¯ ora to occur at higher densities than soil-rooted types
(Fig. 9.8).
Rather than habit-speci® c differences in `ecological plasticity' , other
plant characteristics and statistics biased by Puya and the inordinate occurrence of lithophytic Tillandsioideae in Andean habitats may further
account for Ibisch et al.' s conclusion about plant habits and patterns of speciation. Seed mobility more plausibly affects phytogeography and varies
greatly among Bromeliaceae, and especially among the natives of Peru.
Peruvian Puya (73 wholly terrestrial species) exhibits 89% endemism, which
is not surprising given its frequent co-occurrence with only one to a few
closely related species and immobile seeds compared with those of anemochorous Tillandsioideae and largely zoochorous Bromelioideae. High
endemism in Puya is also consistent with the same elevational trend
expressed by two (Orchidaceae, Piperaceae) of the other three families they
surveyed. Insularity should increase as habitats become more alpine and,
ipso facto, dissected by deep valleys.
Bromelioideae differ in mobility and exhibit high insularity in another
part of South America. Strictly Brazilian and unfailingly terrestrial
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Orthophytum and Cryptanthus (Fig. 1.3D) bear relatively dry fruits (Fig.
3.6E) compared with predominantly arboreal and wider-ranging relatives
(e.g., Aechmea, Billbergia; Fig. 3.6C,D,G). Much the same can be said of
certain Tillandsioideae even though the entire subfamily disperses via
comose seeds. Exclusively lithophytic Alcantarea produce less airworthy
propagules than largely epiphytic Vriesea and Guzmania, probably re¯ ecting ranges that often include but one island-like inselberg (Fig. 1.4A).
Bennett (1992c; Table 6.6) demonstrated similar differences among seeds
that co-vary with bark or rock as the substrate among members of a group
of Tillandsia species.
Compared with the typical terrestrial bromeliad, the epiphytes indeed
may be less fastidious about substrates (recall the low host speci® city
described in Chapter 7), as Ibisch et al. suggest. Moreover, Amazonian
Bromeliaceae may range widely (and remain depauperate) in part because
alternating hot, dry weather and hyperhumidity characterize vast regions
also largely free of topographic barriers to plant dispersal. Hyperdispersed
populations probably assured that competition would not appreciably
in¯ uence the number of Amazonian bromeliads despite their considerable
similarity (e.g., frequent shared dependence on phytotelmata and plantfeeding ants). Speci® cally, plant interference would not promote character
displacement leading to speciation. For whatever reason, a much underutilized (empty) living space has not fostered the species-rich arboreal ¯ ora
that a lottery-type mechanism may favor (Benzing 1981b) elsewhere,
including those communities in adjacent regions (e.g., Peru, Colombia)
characterized by continuously humid montane habitat (and often many,
ecologically similar, populations).
In our view, inquiry on the importance of plant habit to speciation in
Bromeliaceae should be pursued by ® rst determining how many members
of the largest groups of related, ecologically mixed species are epiphytic or
terrestrial. A second step requires determinations of the degrees of interrelatedness of the arboreal and soil-dependent populations within these
groups. Recent, active speciation should yield clusters of genetically similar
descendants, and a slower version of the same process, the opposite
outcome. Essential to this kind of assessment is a reliable measure of evolutionary (genetic) identity, probably an index based on multiple DNA
sequences. Current taxonomic boundaries are not reliable indicators of
relationship, and phytogeography alone lacks the power to reconstruct phylogeny, and hence determine whether the size of a constellation of species
parallels its age.
Ibisch et al. speak of combining taxonomic, ¯ oristic and life-form
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History and evolution
analysis to investigate the relationship between propensity to speciate and
plant habit ± in this case epiphytism vs. terrestrialism. We applaud this suggestion and emphasize the importance of also recognizing the many additional plant characteristics and aspects of habitats (e.g., extent, continuity
in time and space, amenability to partitionment by epiphytes) that affect the
geographic distributions of ¯ ora. Answers to questions as fundamental as
the contribution of one habit over another to the expansion of a clade and
its range require an approach commensurate with the complexity of the
phenomenon under scrutiny.
Chromosomes, hybridization and polyploidy
Bromeliaceae have experienced some polyploidy, probably including one
particularly notable event, and timing suggests that consequences for evolution were greater early rather than more recently during family history
(Brown and Gilmartin 1986, 1989a). Unlike the grasses, Rosaceae and the
other families that immediately come to mind as exemplary of extensive
polyploidy and hybridization, the bromeliads possess a relatively constant
high base number. Here and there a cluster of species exhibits twice and
occasionally threefold this number of chromosomes. Ananas comosus is
triploid. However, counts exist for only about 1 in 10 binomials, and sampling has been uneven.
No reports exist for a substantial portion of the smaller and mediumsized genera, several of which (e.g., Brocchinia, Fascicularia, Greigia,
Navia) combine other characteristics that suggest considerable distance
from the genera that constitute the cores of their respective subfamilies
(sensu Smith and Downs 1974). Tillandsioideae and Bromelioideae distinguish Bromeliaceae among ¯ owering plants less by polyploidy than by their
displays of heteromorphic karyotypes (Fig. 9.9) and discordant counts in
root tips vs. microsporocytes. Small chromosomes, aneuploidy (e.g.,
Tillandsia complanata, n520 or 22) and occasionally phenotypically
undifferentiated polyploid races further impede attempts to reconstruct the
origin of the bromeliad karyotype and identify possible incidences of reticulate evolution.
Lowest common denominator derivatives (e.g., base number of 2n516,
x58) inspired early hypotheses concerning base chromosome numbers in
Bromeliaceae (Billings 1904; Lindschau 1933; Weiss 1965; Marchant 1967;
Sharma and Ghosh 1971; McWilliams 1974). Brown and Gilmartin
(1989a) modeled karyotype evolution using phylogenetic evidence that
favored the then popular notion that Bromeliaceae and Velloziaceae (x58)
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489
Figure 9.9. Microsporocyte from Vriesea schwackeana demonstrating bimodal
karyotype.
are sister taxa (e.g., Huber 1977; Dahlgren and Rasmussen 1983; Dahlgren
et al. 1985; Gilmartin and Brown 1987; Ranker et al. 1990). Their scheme,
which also accords with Dahlgren' s Bromelii¯ orae, imputes the origin of a
dibasic x517 lineage via hybridization between x58 and x59 parents, followed by a second cross with another x58 lineage to yield x525 (Fig.
9.10).
However, ® ndings from rbcL sequences (Clark et al. 1993; Duvall et al.
1993) that identify Rapateaceae as the sister family for Bromeliaceae
contradict Brown and Gilmartin' s model. Unfortunately, only one count
(2n522), for African Maschalocephalus, represents Rapateaceae in the literature. Moreover, the occurrence of the other 15 genera in South America
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Figure 9.10. Proposed model for chromosome base number evolution in
Bromeliales. The extant base number n525 is synapomorphic for Bromeliaceae and
derived by hybridization and polyploidy involving a paleodiploid (n58) and paleotetraploid (n517). The dibasic paleotetraploid developed from hybridization and
polyploidy involving paleodiploids n58 and n59 (after Brown and Gilmartin
1989a).
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491
renders Sharma and Ghosh' s (1971) consequent assignment of x511 for
the entire family especially tenuous.
Although chromosome numbers suggest identity between Cryptanthus,
the only bromeliad genus with x517, and the ancient paleotetraploid,
descending aneuploidy offers a second, and according to Brown and
Gilmartin (1989a), Brown and Palací (1997) and the ndhF data, more plausible explanation. Higher than expected amounts of nuclear DNA in cells
with only 34 chromosomes (e.g., C. acaulis, C. beuckeri) also suggest aneuploidy, i.e., condensations of formerly discrete chromosomes (Ramírez
1996; Chapter 11). Less dramatic reduction beginning with the x525 condition occurs elsewhere (e.g., Aechmea tillandsioides, n521; Tillandsia
umbellata, n518; T. leiboldiana, n519). Brown and Gilmartin further considered Cryptanthus too specialized for paleotetraploidy by virtue of its
polygamous breeding system (subgenus Cryptanthus only), which has no
equivalent elsewhere in Bromeliaceae. They also cited interfertility between
Cryptanthus beuckeri and C. bahianus and Billbergia nutans as additional
evidence of a more contemporary than relictual status. Comprehensive
sampling of Cryptanthus and closely allied Orthophytum, which lack a
single chromosome count, might help reveal how the number 25 originated
and its relationship to 17.
Arti® cially produced, and probably also the natural, hybrids in
Tillandsioideae outnumber those in the other two subfamilies even though
many Bromelioideae also exhibit interspeci® c fertility (Table 6.2). Most of
these intermediates appear to be diploids. Two species of Bromelia, and one
each in Ananas, Nidularium and Pseudananas, reportedly possess duplicated sets of chromosomes (Brown and Gilmartin 1986). Polyploids also
exist in Dyckia and Fosterella, and one Guzmania specimen yielded a suspiciously high chromosome count. Tillandsia, especially subgenus
Diaphoranthema, which includes the most miniaturized (heterochronic)
species in the genus, tops the list of exceptions. Of the 20 populations examined, 12 produced tetraploid ® gures, and another (T. capillaris; Till 1992a;
Chapter 13) a hexaploid number. Only eight taxa remain diploid and
diminutive Tillandsia loliacea includes diploid and tetraploid races.
Polyploidy also accompanies ¯ oral morphology that promotes autogamy through much of subgenus Diaphoranthema. Flowers of Tillandsia
capillaris f. hieronymi fail to open, yet fruits usually result (Gilmartin and
Brown 1985). Several relatives approach this condition. Till (1992a)
reported additional cases of cleistogamy (e.g., T. angulosa, T. castellanii, T.
landbeckii subsp. landbeckii) and autogamy sometimes associated with
larger, fragrant ¯ owers (e.g., T. myosura, T. virescens). Facultative apomixis
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History and evolution
and routine inbreeding, combined with polyploidy and variable karyotypes
(4n584± 96) may underlie the exceptional polymorphism exhibited by
members of the T. capillaris complex, and perhaps also their site-speci® c
propensities to root exclusively on bark or rock.
Miniaturization associated with paedomorphosis probably obliged
autogamy as Diaphoranthema radiated and plants became too small to
support ¯ owers large enough to attract most pollinators (Till 1992a;
Chapter 6). Conceivably, cleistogamy is conserving gene combinations well
suited for the stringent growing conditions encountered by vascular epiphytes and saxicoles of such vulnerable sizes. Cleistogamy, unusual architecture fostered by heterochrony and polyploidy all affected evolution, but
how in this instance and whether synergistically remains unclear. Closer
examinations of the breeding systems and cytology of subgenus
Diaphoranthema and less specialized and probably paraphyletic
Phytarrhiza should be informative.
Bimodal karyotypes exceed the incidence of polyploidy in Bromeliaceae,
and exceptionally small chromosomes characterize the entire family (Fig.
9.9). Palací (1991) discovered an even more unusual condition among populations comprising the Tillandsia friesii complex (subgenus
Anoplophytum). These plants possess chromosomes graded into four
classes: relatively large ones, those of medium size with a satellite at the end
of one arm, others of similar proportions but with no satellites, and a ® nal
category for the small, `dot-like' members. However, claims (e.g.,
McWilliams 1974) that the heteromorphic karyotype consistently cooccurs with extraordinary morphology and propensities for unusual substrates (absent in Pitcairnioideae, maximal in Tillandsioideae) lack
foundation.
Also perplexing are the lower counts obtained from root tips compared
with pollen mother cells from the same epiphytes and lithophytes.
According to Brown and Gilmartin (1986), the primarily mechanical root
may tolerate levels of aneuploidy unsustainable in organs required to
perform more exacting physiological functions. Certainly the sclerenchymatous nature of the roots of Tillandsioideae and some Bromelioideae
make counting difficult enough to favor false readings (Fig. 2.15).
Karyotypic asymmetry is no less real, but whether its association with specialized structure and function indicates importance as a mechanism to
perpetuate speci® c genotypes for demanding habitats requires con® rmation.
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Ancestral habitats
A. F. W. Schimper' s (1884, 1888, 1898) declaration that the vascular epiphytes evolved from stocks native to the understories of humid tropical forests
continues to provoke conversation and inquiry. Pittendrigh (1948) rejected
this judgment for the bromeliads following extensive observations in
Trinidad. He reported instead that arboreal Bromelioideae and
Tillandsioideae arose from more light-demanding, arid-land ancestors.
Colonization of the lower canopy by Tillandsioideae supposedly occurred
from the top down as the well-developed indumentum still featured by the
presumed plesiomorphic Type Five Tillandsia (Fig. 2.8C,E) diminished to
what today serves Type Four bromeliads (Fig. 2.8B). At the same time, progressively in¯ ated leaf axils provided the continuous supply necessary to
meet the growing demand for water obliged by increasingly more droughtsensitive and shade-adapted foliage (Fig. 1.2G).
Pittendrigh proposed that Bromelioideae changed less during the same
transition. Most of its epiphytic members supposedly remain impressively
stress-tolerant, and they anchor on arid and sun-exposed substrates in tree
crowns much as ancestors did and some modern forms continue to do on
the ground (Fig. 1.3E). Many arboreal and terrestrial types, like the majority of Tillandsioideae, also rely on phytotelmata, in this case elaborated
from the smaller impoundments featured by antecedents with more conventional Type Two architecture (Fig. 2.14A,B). Terrestrial Bromelia
humilis and relatives with comparable morphology (Type Two; Table 4.2),
Pittendrigh reported, exemplify the primitive bauplan. Life in the canopy
was also presaged by the presence of foliar trichomes, that, if as competent
as those of Ananas comosus (Sakai and Sanford 1979), already supplemented the nutritive ions and moisture that ancestors and some extant
members of this subfamily still obtain from soil (Fig. 1.3E).
According to Pittendrigh, the argument that Tillandsioideae colonized
drier parts of the forest canopy ® rst and wetter sites later rests on two
points. First, Tillandsia retains what taxonomists consider the least specialized of the ¯ owers present in the subfamily (Smith and Downs 1977).
Second, most dry-growing Tillandsioideae belong to this same genus. In
essence, ¯ oral morphology and several vegetative characteristics that affect
water relations supposedly evolved in concert. Like Tietze (1906),
Pittendrigh also considered the foliar trichome unlikely to have replaced
the root as the primary absorptive organ under humid conditions, (i.e., in
Schimper' s understory habitats). Findings since 1948 have persuaded
several subsequent authors to take opposing views on the evolutionary
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status of bromeliad xerophytism and the origins of speci® c features related
to water balance like the phytotelm shoot and absorbing scale.
Pittendrigh' s decision to extrapolate the ecology of ancestors from that
of extant descendants drew less criticism ® ve decades ago than it should
today. Also troublesome is the evidentiary basis of his judgment about
optimum conditions for speci® c taxa, viz. plant distributions relative to
prevailing growing conditions in lieu of the more immediate measures of
plant performance possible today. As it turns out, several of Pittendrigh' s
shade-tolerant but supposedly heliophilic subjects, and certain other thinleafed Tillandsioideae, exhibit low light compensation and saturation
intensities (e.g., Benzing and Renfrow 1971b; Smith 1989; Fig. 4.7),
although not as low as those recorded for some other understory plants
considered shade specialists. Moreover, much vegetation, including
Bromeliaceae, acclimates across steep light gradients, and closely related
genotypes often thrive under widely divergent exposures.
Several authorities since Pittendrigh have also adopted rigid notions
about the ecological consequences of speci® c plant characteristics, and
how rapidly some of these features can evolve (e.g., Ortlieb and Winkler
1977; Smith 1989; Fig. 9.11). Recent ® ndings on the ecophysiology of
diverse tropical ¯ ora exemplify the ® rst problem. Certain extant CAM
plants, including several Bromeliaceae, tolerate unexpectedly deep shade
(e.g., Aechmea magdalenae; Figs. 4.4, 4.5) in humid habitats, and Type Two
Ananas and Bromelia so often perform best in the forest understory that
Medina et al. (1986, 1991a) concluded that they probably originated there.
On the second issue, mixed responses among a collection of Ananas
comosus cultigens observed by the same investigators illustrated how selection by indigenous farmers has altered light relations among closely allied
genotypes. Guzmania monostachia with its facultative CAM and sun and
shade phenotypes illustrates similar ecophysiological variety of natural
origin (Table 4.6; Chapter 4).
Current ecophysiology may reveal fundamentals that constrained evolutionary options for clusters of closely related lineages (e.g., occurrence of
all Nidularium in dark, moist habitats). But do the bromeliads collectively
exhibit sufficiently consistent light relations to justify conclusions about
conditions in ancestral habitats? Fully one-third of the bromelioid genera
(e.g., Disteganthus, Lymania, Ronnbergia, Nidularium) contain a preponderance of species largely relegated to the forest understory; many more
(e.g., Aechmea, Bromelia, Canistrum, Cryptanthus) exhibit mixed tolerances for exposure. Conceivably, deeper understanding of the structure of
the photosynthetic apparatus will help reconstruct the historic responses of
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Figure 9.11. Postulated phylogenetic relationships within Bromeliaceae based in part on the taxonomic distribution of CAM and C3
photosynthesis at the level of genera. According to this scheme, the epiphytic habit and CAM arose more than once. A progressive loss
of CAM is indicated for Bromelioideae (after Smith 1989).
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History and evolution
individual lineages to light, just as the capacity to sequence DNA already
provides a way to quantify relationships among genes of interest (and indirectly the plants that possess them).
More can be said about ¯ exibility among closely related genotypes.
Within Tillandsioideae, Tillandsia excels for ecological versatility; its phytotelm forms, especially those with discolorous and sparsely trichomed
leaves displayed in minimally overlapping arrays (e.g., T. monadelpha), rank
among the most shade-tolerant of all the bromeliads. Close relatives (same
subgenus) occupy desert and lithic habitats that subject resident ¯ ora to
undiminished sunlight (e.g., Brazilian T. kurt-horstii; Fig. 4.23D,E). Quite
likely, options for the descendants of early Bromeliaceae exceeded those
articulated by Pittendrigh enough to allow dark and moist and brighter and
drier sites in the canopy and on the ground to be colonized by close relatives.
Pittendrigh' s notion about concerted evolution fails to recognize that
¯ oral characters need not change synchronously with those that dictate
vegetative function, nor does reproductive morphology always parallel
phylogenetic relationship (e.g., Benzing and Renfrow 1971c; Brown and
Terry 1992; Till 1992a). Mosaic evolution applies as much to Bromeliaceae
as to the rest of the tracheophytes. No less problematic is the issue of which
growing conditions fostered speci® c kinds of evolutionary change.
Selection by an agency other than drought, or if by drought then by a mechanism involving heterochrony, may explain why the foliar trichome
achieved certain attributes central to plant survival. However, Tietze and
Pittendrigh' s notion about xerophytic ancestry and why the bromeliad trichome became a root analog represents just one of several possibilities, and
not necessarily the most compelling one.
Medina (1974) chose a more pervasive plant condition on which to base
his version of bromeliad ancestry. Antecedents were supposedly similar to
certain extant Guayanan Pitcairnioideae (e.g., Brocchinia, Navia) native to
humid, sunny, and hence relatively permissive, habitats. Exceptional
drought-tolerance, assisted by CAM, like that expressed by modern
Dyckia, Hechtia, many Tillandsia and most Bromelioideae, came later as
evolving lineages entered drier zones, including the forest canopy.
Tillandsioideae supposedly adopted its tolerance for diverse growing conditions along two routes that began with a common semixerophytic stock
at or around the time epiphytism emerged. Thin-leafed, shade-growing
types capable of high quantum yields at low photosynthetic photon ¯ ux
density (PPFD) and poorly suited to resist desiccation represent one end
point (Fig. 4.7). The other progression, which would culminate in Type Five
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497
Tillandsioideae, evolved to accommodate the dryness and exposure experienced in tree crowns and on rocks and desert soils (Fig. 2.1).
Smith (1989) associated himself with Medina, likewise rejecting
Schimper' s hypothesized ancestral habitats in the forest understory. He
offered no comment about Benzing and Renfrow' s (1971b,c) evidence that
several of Pittendrigh' s shade-tolerant bromeliads perform well in lowenergy environments, and, more importantly, provide no persuasive evidence of earlier accommodations to higher PPFD. Smith' s scheme (Fig.
9.11) imputes monophyly for the family, a common mesophytic (C3) stock,
and the multiple origins of CAM suggested by Medina. It aligns
Bromelioideae and Pitcairnioideae as sister taxa that shared a C3-type
ancestor after Tillandsioideae branched off the same lineage.
Smith and Medina joined Pittendrigh and Tietze in citing aridity to
explain the absorptive capacity of the more specialized bromeliad trichome. Foliar indumenta serving Type Five Tillandsioideae probably do
possess unparalleled capacity among homiohydrous ¯ ora to mediate water
balance in the absence of absorptive roots (Figs. 4.20, 4.21). Moreover,
impact on water relations is so striking that it obscures the trichome' s less
conspicuous role in mineral nutrition, and accordingly, perhaps why this
organ became a root substitute in the ® rst place. If the growing conditions
experienced today by the Guayanan bromeliads Medina considered similar
to family ancestors also prevailed in ancestral habitats, services provided by
the foliar indumentum may have been less comprehensive then than now.
Quite possibly the multifunctional trichome of dry-growing
Tillandsioideae owes its debut as a replacement for the absorptive root to
needs equivalent to those provided for carnivorous Brocchinia reducta,
which involve mineral nutrition more than water balance. This species regularly grows in humid habitats, often rooting in seasonally water-saturated
soils. If the trichome of ancestral Tillandsioideae (perhaps the stock for
Brocchinia as well) was similar in evolutionary grade to that of B. reducta,
drought would encourage its further elaboration to provide the greater
variety of services Type Five Tillandsioideae require of the foliar indumentum. A third scenario, involving heterochrony, explains how conditions in
humid forest could bring about the same outcome. If nothing else,
Brocchinia illustrates how rapidly the structure and function of the bromeliad trichome can shift as ecology, shoot architecture and nutritional mode
change (Fig. 2.5A,B,G± J).
According to Smith (1989), Schimper' s ideas also fail to explain the ecological history of Tillandsioideae because no members with mesic shoots
and soil roots routinely reside in the understory of the humid tropical
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forest, at least not in Trinidad. But elsewhere they do. Numerous caulescent
forms without overlapping leaf bases (e.g., Tillandsia insignis, Guzmania
caricifolia, G. graminifolia, and additional species assigned to Guzmania
subgenus Sodiroa) inhabit cloud forest where their roots interchangeably
anchor shoots to soil and bark. Relatives native to more demanding sites
provide no better support for the Tietze/Pittendrigh hypothesis considering
that they deviate even more than the mesic forms from the profusely rooted
monocotyledonous stereotype (Fig. 2.20). Members of several bromelioid
genera (e.g., Aechmea, Ronnbergia; Figs. 2.2F, 2.4E) native to similarly
moist habitats exhibit equally generalized monocot architecture.
Many more taxa illustrate how readily colonists from the understory can
move to the forest canopy, or as lithophytes also become independent of
soil. Tillandsioideae native to the rupestral ® elds of southeastern Brazil
support Medina' s proposed parallel between the evolution of Brocchinia
and more extensively epiphytic Tillandsioideae. Alcantarea farneyi, A. hatscbachii and A. duarteana native to the stony grasslands of Minas Gerais and
neighboring Bahia states, along with Brocchinia on comparably ancient terrestrial media, suggest how readily mesic lineages can exchange arboreal
and lithic for more conventional terrestrial substrates (Figs. 1.2B, 1.4C).
These three Alcantarea species resemble the grass-like pitcairnias more
than their phytotelm relatives; they also impound no more moisture or
debris in leaf bases than Pittendrigh' s Type Two Bromelioideae. By contrast, Alcantarea edmundoi, A. imperialis and A. regina, among others,
possess massive shoots that accumulate many liters of material at maturity
(Figs. 1.2C, 7.1D). Recall that Brocchinia also includes savanna endemics
without appreciable interfoliar chambers (e.g., B. prismatica, B. vestita; Fig.
5.3D) and others (B. tatei; Fig. 1.2B) with phytotelma rivaling those of
hundreds of utriculate-leafed species assigned to the other two subfamilies
(Fig. 2.4). Clearly the evolutionary distance separating a widely occurring
monocot architecture from the arrangement that allows many
Bromeliaceae to create a soil substitute is modest.
Narrow-leafed members of Brocchinia and the previously mentioned
species of Alcantarea with the same architecture may owe their shared
upright stature to the conditions Medina (1974) envisioned for his ancestral Bromeliaceae. Graminoids and the other herbs with upright, narrow
foliage responsible for the shallow, but dense, canopies of grasslands
overtop co-occurring ¯ ora equipped with relatively ¯ at rosettes. The rosulate bromeliad competing for light in such communities may well have
responded by evolving similar upright leaves, and consequently, modest
impoundment capacity. But even if true, is this condition in Brocchinia and
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499
Tillandsioideae and also certain Bromelioideae basic or derived (Fig.
2.4E)? Then again, perhaps emphasis on the characteristics of the adult is
misplaced ± at least so far as explaining the relationship between Type Four
and Type Five Tillandsioideae is concerned.
The evolutionary pathway suggested by two heterophyllous members of
Tillandsioideae also presumes a mesic stock, and perhaps epiphytism prior
to the emergence of the more stress-tolerant, neotenic forms (Fig. 2.1). This
pathway also imputes the existence of an ancestor that was already reliant
on absorptive foliage and a phytotelma in place of a root system that had
formerly provided access to soil. Contrary to several other authorities (e.g.,
Schulz 1930; Tomlinson 1970; Benzing et al. 1985), Medina (1974) rejected
heterochrony to explain the xeromorphic character of the seedlings of phytotelm Tillandsioideae. Instead, these features were dismissed as vestigial,
simply recapitulations consistent with antecedents that were generally more
xeromorphic than their descendants.
Findings reported by Adams and Martin (1986a), Reinert and Meirelles
(1993) and Zotz and Andrade (1997) challenge Medina' s hypothesis that
juveniles and adults of soft-leafed taxa share important aspects of water
balance because they experience the same climate. His view ignores certain
size vs. form-related determinants of ecoperformance that change during
ontogeny (Figs. 4.9, 4.17). Speci® cally, it overlooks the coupling of plant
morphology, especially surface to volume ratio, and rates of CO2 and H2O
exchange. Adams and Martin and Reinert and Meirelles based their interpretation of heterophylly on current plant function vis-à-vis prevailing
growing conditions. They chose not to assign relictual status to form that
appears to grant the juvenile greater drought-tolerance than if it were constructed more like the adult.
Tested seedlings of heterophyllic Tillandsia deppeana desiccated more
slowly and continued to photosynthesize longer without irrigation than the
adults in accordance with expectation based on needs in native habitats
(Fig. 4.9). Tanks sustain the mature specimen through dry weather, whereas
the juvenile routinely faces drought unassisted by access to a comparable
reservoir. Episodes beyond a few rainless days challenge water balance until
the seedling, being effectively rootless, achieves capacity to impound substantial moisture, a process that requires many months to years. Until then,
the phytotelm bromeliad necessarily operates in the Type Five mode, surviving as its more stress-tolerant relatives do by virtue of their specialized
indumentum and underlying water-storage tissues. Reinert and Meirelles
(1993) projected the same kind of performance for Vriesea geniculata for
the same reasons.
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History and evolution
According to the hypothesis involving heterochrony, the trichome of
Tillandsioideae initially became a root analog to serve the relatively vulnerable seedling more than the better-supplied adult. That event in turn set the
stage for the neotenic derivation of more broadly drought-tolerant (Type
Five) descendants (Fig. 2.1). Conceivably, an ancestor already equipped
with absorbing scales to complement its other features as a semixerophyte
could have produced multiple epiphytic stock that, as Medina envisioned,
subsequently radiated into both more humid and drier parts of the canopy.
Absorptive function may also have appeared without great immediate consequence in the manner described above for Brocchinia. Whatever the
pathway, the trichome shield would evolve its most elaborate form when
environments favored an indumentum, that in addition to absorbing water
and essential ions slows transpiration and scatters excess photons off dry
leaf surfaces.
Whatever the nature of the early bromeliads or their habitats, much
homoplasy involving bauplan, important aspects of organs like the foliar
trichome, and ecophysiology in¯ uenced the dimensions and directions of
the ensuing radiation. CAM, xeromorphy and phytotelm shoots all
emerged repeatedly, and occasionally derived conditions returned to
former states. Such a reversal appears to have allowed Nidularium to penetrate exceptionally dark, moist habitats in Atlantic rainforest as terrestrials
and trunk epiphytes. Presumably, C3 Greigia evolved from comparable
ancestry to accommodate cooler, moister montane habitats. Brocchinia features a set of homoplasies that involve the same characters that have been
most instrumental for the success of Bromeliaceae in diverse, often
demanding habitats, especially the forest canopy (Fig. 9.5). Of all the
genera, this one comes closest to paralleling the adaptive history of the
entire family.
Heterochrony
Heterochrony was just invoked to suggest how dry-growing (Type Five)
Tillandsioideae evolved from stocks comparable in form and function to
extant lineages characterized by phytotelma and thin, sparsely trichomed
foliage (Type Four; Fig. 2.1). Miniaturization distinguishes members of
these two evolutionary grades as does architectural abbreviation in a
manner consistent with similar phenomena in many other groups of plants
and animals (Hanken and Wake 1993). Presumably bene® ts related to
anchorage on bark and rock as opposed to more resource-rich soil favored
this transition in Bromeliaceae.
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501
Before moving on to greater detail, we need to consider how heterochrony can alter plant form and function enough to propel a lineage from
one adaptive zone or evolutionary grade to another. Examples elsewhere
indicate that Bromeliaceae ® t a familiar pattern on this basis, although
among paedomorphic ¯ ora the combination of affected plant characteristics is quite novel. Moreover, change ranges from nonexistent in some
members of the family to revolutionary for others.
Genes expressed early during ontogeny are better timed to affect the phenotype of the adult than those expressed later. Re-program a morphogenetic cascade and the shapes, numbers and relationships among organs
may shift with potential consequences for function, life history and ultimately ecology. Organ redundancy may occur, for example the leaves on a
shoot may increase or diminish in number, or fail to develop altogether as
when thalloid Lemnaceae emerged from some aroid-like stock. Here, as in
Tillandsioideae, miniaturization paralleled the emergence of a simpler
bauplan. Also like Type Five Tillandsioideae, the duckweeds occupy specialized environments ill suited for larger plants equipped with conventionally organized shoot and root systems. Several invertebrate phyla (e.g.,
Gnathostomulida, Loricifera) exhibit comparable reductions and structural reorganizations to accommodate life within the interstitial spaces of
suitably textured soils (Hanken and Wake 1993).
Comparative morphologists recognized the interconnectedness of
ontogeny, evolution and phylogeny more than a century ago, and since then
have employed this paradigm to reconstruct evolution, primarily morphological change. Heterochrony explains the polarities of certain graded character states among related organisms, ranging from ® ne details such as
ovary position or ¯ ower type (e.g., cleistogamous vs. chasmogamous
¯ owers of certain Impatiens spp.) to the total transformation of a bauplan
as in the duckweeds. Bromeliaceae include a more complete array of transitional forms than Lemnaceae, and these survivors demonstrate how the
numbers, shapes and sizes of body parts, and ultimately the design of the
entire organism, evolved as the rates and timing of discrete morphogenetic
events changed. By de® nition, heterochrony includes developmental and
phylogenetic components. However, like all Darwinian processes, effects on
® tness in¯ uence magnitude and direction.
Edwardo Morren, the Belgian horticulturist, formally recognized heteroblasty, if not heterochrony, when he described Tillandsia heterophylla more
than a century ago. Subsequent authors noted similar distinctions between
the early and later life stages of additional Type Four Tillandsioideae (e.g.,
Schulz 1930; Tomlinson 1970). Seedlings representing many of the
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History and evolution
Figure 9.12. An unidenti® ed Nidularium sp. seedling growing on rock in Rio de
Janeiro State, Brazil. Were adult foliage also present, heterophylly would be apparent.
phytotelm species remain relatively succulent and compact for several years
until adult foliage emerges. Bromelioideae may provide a more muted and
so far less-studied parallel. Some of its most extraordinary members, like
heterophyllic Neoregelia abendrothae, produce shoots comprised at ® rst of
narrow leaves and later of others with water-tight, in¯ ated axils and
broader, channeled blades (Fig. 2.2D). Figure 9.12 illustrates the seedling
of an unidenti® ed Nidularium growing on a mossy rock in a Brazilian wet
forest. Note that this plant lacks the capacity to impound water like the
adult. Nevertheless, the ® liform leaves already possess the serrated margins
characteristic of its subfamily.
Schulz (1930) commented on the relatively xeromorphic character of the
seedlings of certain Type Four Tillandsioideae. More detailed studies using
Tillandsia deppeana (Adams and Martin 1986a,b,c) and Vriesea geniculata
(Reinert and Meirelles 1993) con® rmed his impressions and further dem-
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503
onstrated correlated shifts in water relations as described above and in
Chapter 4. Features of the epidermis that affect gas exchange and energy
balance also change as the shoot matures and develops foliar impoundments (Table 4.7). Brie¯ y, trichomes of the juveniles more densely (80% for
saxicolous Vriesea geniculata) invest the blades and possess broader shields
than those of the adults. Densities of stomata also increase over the blade,
but not the leaf base, as plants age. On the other hand, CO2 exchange and
D values indicated life-long dependence on C3 photosynthesis.
Of the two routes to juvenilization (paedomorphosis), neoteny rather
than progenesis ® ts Tillandsioideae. Both pathways require that vegetative
ontogeny be decoupled from sexual maturation, but in different ways.
Neoteny prevails when the adult of the derived genotype more closely
resembles the juvenile than the adult stage of the evolutionary antecedent.
Relatively few nodes need to develop before the neotenic, determinate
shoot ¯ owers (e.g., Tillandsia usneoides; Fig. 2.1). Consequently, reproduction is precocious in terms of development, if not also in real time. Whether
or not life cycling speeds up, less biomass need be invested in vegetative
tissue prior to ¯ owering than was possible when shoots and root systems
were more elaborate. Precocious sexuality marks the progenic descendant,
for example the specimen that ¯ owers from one or more, formerly sterile
(pre-reproductive) nodes.
Some Type Five Tillandsia deviate from the abbreviated bauplan exempli® ed by Spanish moss and a number of its relatives and initiate ¯ owers at
the tips of shoots comprised of dozens of leafy nodes (e.g., T. bryoides; Fig.
2.1). However, miniaturization prevails, and few roots develop as above.
Mexican and Central American Tillandsia xerographica demonstrates how
still other Type Five Tillandsioideae lack the gross structural characteristics of the neotenic forms, yet exhibit similar tolerances and capacities
attributable to an indumentum and ecophysiology comparable to their
more diminutive relatives. Despite its relatively large size, broad succulent
foliage bearing con¯ uent layers of absorbing trichomes and relatively large,
if primarily mechanical, root system, this epiphyte typically inhabits dry
scrub forests with more than a dozen markedly heterochronic members of
the same genus. Tillandsia duratii further demonstrates that Tillandsioideae
can tolerate exceptionally stressful habitats unassisted by the revolutionary
morphological reduction (except for the loss of roots) fostered by neoteny
(Fig. 2.10L).
Heterochrony in¯ uences reproductive capacity depending on how it
affects certain aspects of plant organization and related performance, and
whether the impact is measured in the affected individual or in its inclusive
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population. If the neotenic plant matures in less time than its predecessor,
then a population of such plants, if otherwise equal (e.g., same seed size,
Amax) to that of the ancestor, should expand faster owing to an enhanced
Malthusian coefficient (Chapter 6; Benzing 1978a). Conversely, the same
change reduces the reproductive power of the individual genet to the degree
that precocity reduces the amount of photosynthetic tissue available to
ripen seeds. However, the absorbing trichome relaxes this trade-off for
Tillandsioideae compared with ¯ ora without a similar root analog, i.e., an
equally multifunctional shoot.
Theoretically, a population of Type Five compared with Type Four
Tillandsioideae could grow faster if all factors in addition to body plan that
also in¯ uence fecundity were equal because its members devote proportionally more resources to reproduction at the expense of vegetative tissue.
However, Amax is substantially lower in the CAM-equipped Type Five bromeliad, and for this reason neoteny provided ancestors a mechanism to
enter an adaptive zone colonized by few other families (Benzing 1978a). In
effect, exposure to drought on relatively ephemeral substrates (bark), that
respectively constrain photosynthesis and heighten plant mortality, magni® ed the bene® ts of heterochrony (in this case resource-use efficiency for
reproduction) as Tillandsioideae radiated from humid to drier parts of the
forest canopy.
Neoteny and tillandsioid radiation
Extraordinary stress-tolerance and an economical bauplan only partly
explain why Tillandsia (sensu Smith and Downs 1977) ranges so broadly,
and perhaps why it contains so many, often ecologically similar species.
Several bursts of speciation occurred in different parts of tropical America,
each under somewhat similar circumstances. Common potentials fostered
by close relationships assured parallel evolutionary responses (homoplasy)
to the same environmental challenges in widely scattered regions.
Subgenus Tillandsia represents one of the most proli® c of these radiations. Resultant lineages in this case remain overwhelmingly Mexican with
sizable numbers of additional species distributed through adjacent
Mesoamerica (Chapter 6). A few populations range beyond northern
South America (e.g., T. juncea into southeastern Brazil). Gardner (1982,
1986a,b) provided insights on how pollinators and substrates (bark vs.
rock) probably in¯ uenced speciation in special cases. However, relatives distributed primarily below the Equator better illustrate how geography,
climate and various features of ancestors, including capacity to undergo
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505
neoteny, helped Tillandsia, broadly de® ned, achieve its impressive size and
exceptional vegetative structure and function.
Much of Tillandsia (e.g., subgenera Allardtia, Pseudalcantarea,
Pseudocatopsis) shows little evidence of paedomorphosis. Instead, these
plants retain the bauplan that incorporates determinant, leafy modules
(ramets) produced in seriatum by sympodial branching (Fig. 2.3A).
Subgenus Tillandsia exhibits a greater range of architectures, whereas the
remaining three, largely South American subgenera, viz. Anoplophytum,
Diaphoranthema and Phytarrhiza, illustrate structural simpli® cation and
reductions in size unmatched elsewhere in the family. Homoplasy, which is
common within groups of paedomorphically miniaturized fauna and ¯ ora
(Hanken and Wake 1993), also makes an impressive showing in this part of
Tillandsia.
Subgenera Phytarrhiza and Diaphoranthema probably constitute a clade
positioned close to, or perhaps inclusive of, Allardtia and Anoplophytum.
Evidence includes phytogeography, which for both subgenera accords with
climate change during the late Pleistocene (Smith 1934a; Till 1992a). If
Phytarrhiza and Diaphoranthema represent evolutionary grades rather
than clades, then the more advanced of the two architectures emerged
repeatedly. Lineages in Phytarrhiza considered closest to certain
Diaphoranthema (e.g., T. streptocarpa) feature relatively large, polystichous
shoots and sizable in¯ orescences with several to many, often fragrant, chasmogamous ¯ owers (Fig. 3.3I). Those of Diaphoranthema possess fewer,
often distichously arranged leaves on more miniaturized axes. One to
several, often autogamous ¯ owers per shoot typify the most diminutive
Diaphoranthema (Figs. 2.1, 3.3C).
Compared with Diaphoranthema, species of Phytarrhiza generally
occupy warmer, moister sites, and those with the broadest distributions
show considerable polymorphism (e.g., T. streptocarpa). Conversely,
members of the ® rst subgenus tend to resemble microspecies by phenotype
and range (Till 1992a). Structurally uniform populations mostly occupy
con® ned areas in the southern Andes to central Argentina (except T. recurvata and T. usneoides) and often set self-seed. Interestingly, the few, similarly insular Phytarrhiza (e.g., T. reichenbachii, T. peiranoi) of northern
Argentina remain well north of many of the Diaphoranthema species (e.g.,
T. pedicellata, T. erecta, T. aizoides).
Till' s claim that the cooler, drier conditions under which many
Diaphoranthema grow impede photosynthesis too much to allow the more
massive-bodied Type Five members of Phytarrhiza to mature often enough
to sustain populations is consistent with the views expressed here on the
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Table 9.2. Character polarities in Tillandsia subgenera Phytarrhiza and
Diaphoranthema
Ancestral
Derived
Roots well developed
Roots strongly reduced or absent
Leaves in a rosette
Leaves on more elongate stem
Leaves wide and ¯ at, not succulent
Leaves narrow and terete, succulent
Leaves polystichous
Leaves distichous
Scape of in¯ orescence well developed
Scape of in¯ orescence abbreviated or
lacking
In¯ orescence compound, many¯ owered
In¯ orescence simple, few to one-¯ owered
Floral bracts glabrous outside
Floral bracts densely lepidote outside
Sepals glabrous, free, obtuse
Sepals lepidote, especially posteriorly
(5adaxially) connate, acute
Petals conspicuous, blades enlarged
Petals inconspicuous, blades narrowed
Style and ® laments rather long, stigma
and anthers reaching the throat of
the corolla or exserted
Style and ® laments strongly abbreviated,
stigma and anthers deeply included in
the corolla
Flowers without fragrance
Flowers fragrant
Source: After Till (1992a).
advantages of heterochrony in Tillandsioideae. If our hypothesis is correct,
neoteny combined with ¯ oral biology that maximizes fecundity provided
ancestral forms the opportunity to colonize isolated, arid montane habitats
and set the stage for what Till (1992a,b) considered to be at least six episodes of speciation leading to as many monophyletic clusters of four to
seven species in Diaphoranthema. Origins for these six lineages supposedly
lie in subgenus Phytarrhiza, and the `ancestral' and `derived' characters
listed in Table 9.2 describe their parallel evolutionary histories.
Tillandsia usneoides demonstrates how neoteny granted exceptional ecological latitude to a single lineage (Tomlinson 1970). Rather than sharing
the compact, juvenilized morphology displayed by most other
Diaphoranthema, Spanish moss continued to evolve, perhaps under the
impetus of two powerful advantages. Plant characteristics that foster these
dual bene® ts include much elongated internodes, ageotropism and
sufficiently suppressed apical dominance to allow every leaf to subtend a
developed branch (Figs. 2.1, 2.10E). Resultant capacity to fragment in turn
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Neoteny and tillandsioid radiation
507
set the stage for dispersal that no other Bromeliaceae would match. Genets
that expand to form thick trusses of delicate pendant shoots further
promote success to the extent that self-shade and the humid air trapped
within ameliorate the harsher conditions that prevail outside (Fig. 7.7C).
Information on chromosome numbers, reproductive biology and alpha
systematics places modest-sized (,30 spp.) Diaphoranthema among the
better-known subgenera of Tillandsia. Nevertheless, major questions
remain unanswered, for instance why this and related clades speciated so
proli® cally in the southern Andes. As luck would have it, data are available
for some primarily Argentinian populations in Anoplophytum (34 species),
that third subgenus which remains largely con® ned to southern South
America.
Palací (1991) determined that 10 populations representing four species in
Anoplophytum (T. alberi, T. friesii, T. muhriae, T. zecheri var. cafayatensis)
and numerous members of subgenus Diaphoranthema exhibit similar structural, geographic and demographic attributes, especially in the province of
Salta, Argentina and adjacent Bolivia. In short, it appears that these
Anoplophytum and the codistributed species of the Phytarrhiza/
Diaphoranthema complex shared comparable histories while genus
Tillandsia underwent multiple radiations around the margins of its range
in the southern Andes and points eastward, primarily on the inselbergs of
southeastern Brazil.
Relatively large size and polystichous leafy shoots suggest that neoteny
contributed little to the evolution of Anoplophytum. Expansion also
occurred without deviation from the basic diploid (n525) condition.
Floral biology remains little studied, although several species produce conspicuous, fragrant ¯ owers (e.g., T. xiphioides), and bright red to pink ¯ oral
bracts indicate ornithophily for many others (e.g., T. aeranthos, T. stricta,
T. tenuifolia). Plants (T. alberi, T. friesii, T. muhriae, T. zecheri var. cafayatensis) that Palací (1991) examined occur at high altitudes (mostly
.2500 m), often as widely dispersed populations (across .500 km on a
north/south axis) in extreme northwest Argentina and just over the border
into neighboring Bolivia. All four taxa share similar morphology. Proteins
encoded by 14 loci revealed comparatively minor genetic differentiation,
perhaps due to mobile seeds or trap-lining pollinators.
Genetic diversity observed in T. friesii (P533.8%) exceeded that
recorded for epiphytic T. ionantha (subgenus Tillandsia) and T. recurvata
(Soltis et al. 1987), but more closely approached values obtained for terrestrial Aechmea magdalenae (Murawski and Hamrick 1990) in Panama
(Chapter 6). A Gst reading of 0.228 indicated considerable outcrossing, as
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History and evolution
did the relatively high proportions of polymorphic loci, average number of
alleles per locus, and observed heterozygosity. Isozymes indicated just two
copies per locus. Conversely, close genetic identities characterized all of the
comparisons involving T. alberi, T. muhriae and T. zecheri var. cafayatensis,
values high enough to warrant combining three populations under T.
cafayatensis, which in turn Palací considered closely related to, but not conspeci® c with, T. friesii. Occurrence of only about one-fourth of the measured, total genetic variation among, compared with within, its disjunct
populations, owing partly to autogamy and insularity, accords with Palací' s
decision to recognize forms rather than species.
In summary, segregates comprising Palací' s group of closely allied populations of lithophytic Anoplophytum exhibited genetic identity values
ranging between 0.96 and 0.99, too close to unity to recognize species.
Narrow distributions, including occasional restrictions to a single gorge
over similarly extensive north/south ranges, also describe many related,
well-de® ned species of Diaphoranthema and Anoplophytum that once probably also possessed little-differentiated gene pools like those recorded for
the T. friesii complex.
Palací' s data and much additional information suggest that fragmented
habitats and founder events encouraged the recent massive radiation of
Tillandsia in subtropical South America. Inherent factors were also important. Mobile seeds, frost and drought-tolerance (annual rainfall often
below 300 mm), neoteny in some lineages, and capacity to maintain small
populations through autogamous reproduction also rank high among
the factors that helped Tillandsia, especially the membership of
Diaphoranthema, achieve its current status in southern South America.
Before leaving the subjects of adaptation, radiation and heterochrony,
mention is due Gilmartin' s (1983) and Gilmartin and Brown' s (1986)
attempt to infer the phylogenetic juxtapositions of mesophytism and xerophytism in Tillandsioideae, particularly in Tillandsia subgenus Phytarrhiza.
Arguably, heightened stress-tolerance and reproductive power fostered by
neoteny combined with dissected topography and oscillating climate
favored radiation among dry-growing Tillandsioideae in many parts of
tropical America. But how often and where in the subfamily did these transitions occur, and was change consistent in direction? Except for large clusters of species within the Tillandsia/Vriesea complex, mesophytism
pervades Tillandsioideae. The apparent youth and the mix of mesophytic
and xerophytic taxa in these two genera present extraordinary opportunity
to determine the evolutionary polarities of climate-sensitive characters.
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509
Al su
ca bg
nt .
ar
ea
Historic relationships between mesophytism and xerophytism
Figure 9.13. Evolutionary tree illustrating the relationships of the seven Tillandsia
subgenera and two of Vriesea (sensu Smith and Downs 1977) based on the Wagner
unrooted tree method (after Gilmartin 1983).
Historic relationships between mesophytism and xerophytism in
Tillandsioideae
Gilmartin (1983) and Gilmartin and Brown (1986) employed phenetic
(overall resemblance) and phylogenetic (cladistics) approaches to infer historic alignments among the mesophytic, semixerophytic and xerophytic
habits exempli® ed by members of Tillandsia and Vriesea. They also constructed phenograms and phylogenetic trees for the major segregates of
Tillandsia and 36 of the species assigned to subgenus Phytarrhiza. Of the
seven subgenera of Tillandsia and the two comprising Vriesea according to
Smith and Downs (1977), all but Anoplophytum and Diaphoranthema (both
Tillandsia) include xeric and semixeric or mesic members according to leaf
succulence, the development of the indumentum and the identity of the
primary source of moisture (e.g., atmosphere vs. phytotelmata).
Categories of drought-tolerance/sensitivity were limited to just these
three degrees by the absence of adequate ecophysiological data. Weather
records provided additional resolution. Gilmartin' s (1973) xerophytes experience annual rainfall between 300 and 1000 mm in Ecuador, whereas
semixeric types require at least 1000 mm year21. Species labeled mesic
occupy even more humid (.2000 mm) zones where no less than 4% of the
annual input occurs during the driest month. Fifteen characters considered
unrelated to water relations provided the basis for the decisions about phylogeny.
Unrooted Wagner networks (Fig. 9.13) placed Diaphoranthema,
Phytarrhiza and Pseudocatopsis near one end of the network in agreement
with some earlier suppositions about intrageneric relationships (e.g., Smith
1934a). Anoplophytum emerged on the same terminal branch at a point just
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History and evolution
Figure 9.14. Evolutionary tree for subgenera of Tillandsia and Vriesea based on the
character compatibility method (after Gilmartin 1983).
below these same three taxa. Subgenera Allardtia and Tillandsia lie at the
other end of the network. Every branch except those leading to
Anoplophytum and Diaphoranthema respectively includes both mesic and
xeric species. The same analysis without Vriesea produced a tree with
similar topology.
Figure 9.14 illustrates the results of a character compatibility analysis
supported by a seven-character clique. Wholly mesic subgenus Allardtia at
the base of the tree subtends three main lateral branches: Vriesea (both subgenera), Tillandsia with Pseudalcantarea, and the remaining four subgenera. Overall resemblance based on 15 characters separated the two
subgenera of Vriesea, whereas most similar were subgenera Allardtia and
Tillandsia and Diaphoranthema and Anoplophytum. Without Vriesea, alignments changed as obliged by the hierarchical nature of the algorithm; the
absence of that genus altered resemblance values among the remaining
taxa.
A 43-character matrix yielded the phenogram reproduced in Fig. 9.15
that purportedly depicts relationships among 36 species of subgenus
Phytarrhiza. Six mesic types from Ecuador and northern Peru form Group
One, while ® ve of the semixeric taxa constitute Group Two. Nine semixeric
species with simple in¯ orescences clustered with T. straminea to yield
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Historic relationships between mesophytism and xerophytism
511
Figure 9.15. Phenogram resulting from cluster analysis (UPGMA of Sokal' s
average distance) of species of Tillandsia subgenus Phytarrhiza. Roman numerals
designate clusters. Habits are coded: m, mesic; s, semixeric; x, xeric (after Gilmartin
1983).
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History and evolution
Figure 9.16. Evolutionary tree of the species of Tillandsia subgenus Phytarrhiza
based on the Wagner network method. Habits are coded: m, mesic; s, semixeric; x,
xeric (after Gilmartin 1983).
Group Three. Fourteen xerophytic taxa with relatively southern distributions make up Group Four. At the bottom, more massive-bodied and mesic
T. dyeriana joins the larger cluster representing the entire subgenus.
The Wagner network aligns the same 36 species somewhat differently
(Fig. 9.16). Six semixeric Ecuadorian members of Group Three share a
branch with xeric T. cacticola, T. straminea and T. schunkei above the ® ve
semixeric Ecuadorian taxa with simple in¯ orescences comprising Group
Two. Species of both groups qualify for Type Five status and produce
spikes mostly exceeding 2 cm in width except for the three lineages that
share the same branch with Group Three. At the center of the network lie
® ve, fully mesic species with mostly compounded in¯ orescences and broad
leaves (Group One, and T. dodsonii of Group Three, and T. dyeriana).
Group Four resides on the two left-hand branches and shows paedomorphosis, including simple spikes and the expected association with pronounced xeromorphism. Lineages with mesic vs. xeric habits never occupy
the same branch anywhere in the network.
Gilmartin and Brown' s (1986) second set of analyses concentrated on
two closely related Tillandsia subgenera that contain a particularly propitious array of mesophytes and xerophytes to determine the relationships of
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Historic relationships between mesophytism and xerophytism
513
drought-tolerance and vulnerability. Unlike exclusively xerophytic and
highly neotenic Diaphoranthema, Phytarrhiza encompasses the entire range
of bauplans and related water-balance mechanisms. Habits include those
characterized by thin-leafed, sparsely trichomed, phytotelm shoots supported by relatively substantial root systems (e.g., T. dyeriana, T. wagneriana), to the more miniaturized and stress-tolerant types illustrated by T.
caerulea and T. paleacea. Semixeric taxa like T. cornuta and T. dodsonii,
which impound at most modest amounts of moisture to supplement that
stored in semisucculent foliage, bridge these extremes.
Gilmartin and Brown (1986) used 11 `alliances' , three represented by
individual species and eight more putatively monophyletic clusters of up to
eight species, to resolve relationships among mesic, semixeric and xeric
habits in Tillandsia subgenus Phytarrhiza. Flowers provided most of the 15
ecophysiologically neutral characters used to reconstruct an unbiased phylogeny. However, several of these choices, including trichome type
(expanded or minute shield; Fig. 2.8B,C,E), stem length, presence or
absence of roots, ¯ oral bracts with or without trichomes, and leaf shape
(thin and ¯ at or terete) may be more predictive of drought performance
than the authors assumed.
Two sets of equal-length trees incorporating 24 character state changes
indicated paraphylesis for Diaphoranthema and Phytarrhiza consistent with
Till' s (1992b) conclusion, and sister taxon status for Pseudocatopsis and
Phytarrhiza, or some subset of its member species. Tree topology further
indicated that changes from character states considered plesiomorphic to
apomorphic prior to the analysis outnumbered the reversals. For example,
stems usually shifted from short to longer, much as apparently occurred as
populations comprising several Tillandsia species adopted rock as the
exclusive substrate (Fig. 2.10M,N). Consistent with radiations involving
miniaturization elsewhere (Hanken and Wake 1993), trees here also
depicted repeated, parallel changes, mostly from mesic to xeric and mesic
to semixeric, but never semixeric to xeric habits.
Gilmartin (1983) envisioned a montane, moist forest origin for all of the
subgenera of Tillandsia except Anoplophytum and Diaphoranthema, which
she believed descended from semixeric or more xeric antecedents within, or
closely allied to, one of the other segregates, probably Phytarrhiza or
Pseudocatopsis. Smith (1934a) proposed that Diaphoranthema arose from
stock embedded in Phytarrhiza because both subgenera exhibit the greatest densities of species near the south Andean junction of Argentina,
Bolivia and Paraguay.
Oscillating arid and pluvial conditions through the Plio-Pleistocene
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History and evolution
supposedly explain the existence of so many species, both dry-growing and
more drought-sensitive types (e.g., Prance 1973, 1982). Speci® cally, during
arid phases the stress-tolerant forms migrated into newly expanded dry
habitat, while the correspondingly contracted and fragmented populations
of their mesic relatives differentiated in moist refugia. Periodic warming
reversed this pattern, replacing moist with dry refuges that encouraged
divergence among lineages con® ned by ecophysiology to arid landscapes.
Relegation of the more drought-tolerant populations to the tips of the
branches of phylogenetic trees accords with derived status for xerophytism.
Precisely how global change affected radiation within Tillandsioideae
and shaped the current distributions of dry and wetter-growing taxa
remains obscure, particularly in light of the controversy about the impacts
of Pleistocene refugia and Andean orogeny (Gentry 1982) on Neotropical
phytodiversity. Aridi® cation de® nitely triggered cladogenesis in some other
families at other locations over the past 3± 5 million years. For example, predominantly southwest African Mesembryanthemaceae expanded to
,2000 species mostly in developing xeroscapes (Ihlenfeldt 1994), while
Bromeliaceae apparently proliferated on the other side of the Atlantic
Ocean. Heterochrony, including miniaturization and reduced numbers of
leaves, marked this Old World event as it did the expansion of
Tillandsioideae.
Chloroplast DNA data described below that challenge Smith and
Downs' s Tillandsioideae as a clade also disagree with Gilmartin and
Brown' s phylogenetic trees. Nevertheless, the latter two investigators' decision to consider paleoclimate in the attempt to relate the mesophytic,
semixerophytic and xerophytic habits in this subfamily recognizes the signi® cance of past selection to interpretations of current plant adaptations
and geographic distributions. Reconstructing the circumstances responsible for a major radiation is no less worthwhile than determining the relationships among the lineages spawned by that event. Shifting climate since
the Miocene surely affected ¯ ora across tropical America and perhaps
certain Bromeliaceae more than most other vegetation. The substantial literature on ecophysiology reviewed in Chapter 4 indicates how affected lineages probably responded.
Tillandsia native to extreme western Peru (primarily subgenus
Anoplophytum) must rank among the most heavily impacted by shifting
Plio-Pleistocene climate of the indigenous ¯ ora. Natives today occupy
cold-air, rain-shadow deserts maintained by the interactions of geologic,
marine and meteorological in¯ uences. During all but El Niño events, cold,
offshore currents virtually eliminate winter precipitation that would other-
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515
wise arrive on-shore from the Paci® c Ocean. Much of the rest of the year,
the eastern slopes of the Andes, which began to rise above relatively modest
heights only a few million years ago, desiccate ascending air moving along
the tropical interconvergence zone during its southerly migration each
summer.
Few vascular plants beyond some dew-dependent Tillandsia occupy the
Atacama west of the deeply eroded coastal range. Substantial canyons
(,1000 m) that dissect these mountains date from the Miocene when much
more rainfall arrived across a then less obstructed eastern approach and
over a warmer ocean from the opposite direction during the winter. Drier
conditions developed during the Pliocene through the Pleistocene, but not
continuously or synchronously with those hypothesized changes in the
Amazon Basin (Damuth and Fairbridge 1970) which dominate the secondary literature purporting to describe the effects of past climate on plant
evolution and biodiversity.
Information on paleoclimate must be applied more precisely than it has
been so far to reconstruct the adaptive histories of surviving Bromeliaceae.
For example, Pleistocene glaciations supposedly brought cooler, drier times
and much reduced forests east of the Andes, but quite different conditions
probably prevailed west of that barrier. Climates reversed during the much
shorter interglacials. Damuth and Fairbridge (1970) and Arroyo et al.
(1988), among others, proposed that a low-pressure focus over Antarctica
moved northward to the west of South America during the glacials to
enhance humidity in the Atacama region. A weaker Humboldt current that
no longer penetrated as far north further assured moister air masses over
that region during winter.
Plant responses to modern ecophysiological challenges (e.g., see Table
4.8) help identify some of the past events that shaped current geographic
ranges. Torrential rainfall during El Niño events periodically kill off much
of the spectacular near monocultures of soil-bound Tillandsia that occupy
extensive areas of treeless Atacama desert. Presumably, more prolonged
episodes of comparable humidity during earlier times similarly impacted
populations equipped with the same dense, hydrophilic indumenta (Figs.
2.8C,E, 4.11). Paleoclimate has alternately favored different ecophysiological types at given locations according to their vulnerability to drought or
excess moisture. Populations probably expanded and contracted, and
perhaps fragmented and speciated, according to prevailing humidity and
the availability of speci® c substrates. Pluvial phases must have devastated
Type Five Bromeliaceae except where topography lessened rainfall, or bark
and rock maintained an adequate supply of arid microsites (Tables 4.8,
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History and evolution
4.9). Conversely, dependence on phytotelmata and poorly insulated foliage
imperiled Type Four Tillandsioideae during the dry phases, and indeed no
members of this group currently inhabit the Atacama region.
Taxonomy: traditional characters
Successive monographers emphasized different characters to systematize
Bromeliaceae into genera and higher taxa. One to a few attributes of sometimes doubtful utility, like the presence or absence of petal scales, typically
distinguish putative clades (e.g., Tillandsia from Vriesea, Cryptanthus from
Orthophytum and Navia from Brewcaria). No consensus developed on
which parts of the plant body most reliably indicate evolutionary relationships. For example, the in¯ orescence ® gures prominently in Baker' s (1889)
treatment of Bromeliaceae, while Mez (1934± 35) favored ¯ oral characters
and pollen morphology. Smith and Downs (1974, 1977, 1979) assigned substantial weight to the petal scales that Brown and Terry' s (1992) developmental studies suggest represent recently derived, unstable features, at least
among Tillandsioideae (Fig. 3.1B). Numbers highlight the problem: Baker
(1889) recognized 19 genera, while Harms (1930) described 34. Smith and
Downs (1974, 1977, 1979) accommodated a substantially larger number of
species in just 27 genera. Today the number exceeds 55 (Luther and Sieff
1996) and promises to keep growing.
Several taxa remain especially problematic. For example, Mez (1896) initially treated Glomeropitcairnia as a subgenus of Pitcairnia, and later (1935)
granted its two species tribal status (Glomeropitcairniaeae) in
Tillandsioideae. Several features both distinguish and obscure the affinities
of this likely relictual clade, most conspicuously its semi-inferior ovary,
seed with apical and basal appendages, the many-celled trichome stalk, and
unusual mode of capsule dehiscence. Gilmartin et al. (1989) attributed the
co-occurrence of an apomorphic ovary position and plesiomorphic seed
and trichome morphology to mosaic evolution. Seed structure seems to
place Glomeropitcairnia somewhere between Pitcairnioideae and
Tillandsioideae, and indeed, Smith and Downs (1974) considered its reproductive morphology derived from something more like conditions in
certain Pitcairnioideae. Nucleic acid sequences also suggest outlier status,
but closer to core Tillandsioideae than Pitcairnioideae as we will see.
Bromelioideae contains the largest number of questionable genera owing
to its greater ¯ oral variety and the frequent reliance of authorities on
poorly studied taxonomic characters. De® nitions changed with each
monographer. For example, Quesnelia according to Baker (1889) included
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517
species that Smith and Downs (1979) segregated into Aechmea, Andrea,
Ronnbergia and even Pitcairnia! Harms (1930) and Mez (1934± 35) maintained discordant views on several additional taxa, especially Bromelia and
Streptocalyx. Smith and Kress (1989) elevated or resurrected all of the
Aechmea subgenera to full-blown genera. Comparisons of the systems of
Baker, Mez, and Smith and Downs indicate how markedly disagreements
about a few characters have affected bromeliad taxonomy. Moreover,
authorities continue to employ petal scales, sepal and in¯ orescence
morphology to reshuffle species with no end in sight.
Authors will serve the interests of science and bromeliad enthusiasts by
defferring further revisions until judgments can bene® t from more data
obtained with the most powerful analyses currently available. Two decisions
(e.g., Smith and Kress 1989; Smith and Spencer 1992) exemplify the ongoing churning of an already cluttered nomenclature. Both initiatives
employed the same traditional characters to revisit long-standing problems.
More importantly, neither proposal was informed by the emerging molecular and better-resolved traditional data. The restoration of Aechmea subgenus Chevaliera to generic status and the re-establishment of monotypic
Deinacanthon from Bromelia shed no new light on bromeliad phylogeny.
Problematic taxa surely need more attention, but formal revision should
wait until a fuller understanding of bromeliad history justi® es such action.
Chemical systematics
Secondary metabolites
Systematists working with chemicals rather than morphology operate
closer to the genome, and accordingly, should be able to avoid some of the
ambiguities inherent to higher-level biological complexity. However, classes
of compounds differ in their proximity to the basis of relationship, which
is genetic information encrypted in the structure of DNA. Time and cost
also vary. Relative ease of isolation and identi® cation assured that the ¯ avonoids would become useful before the more conservative, complex and
character-rich proteins and nucleic acids.
While not immediate gene products nor immune to homoplasy, the ¯ avonoids and other convenient `secondary' metabolites can provide estimates
of relationships among closely allied taxa, characterize patterns of gene
¯ ow, and help identify the parents of hybrids. Ashtakala (1975) reported
substantial similarity between the ¯ avonoids, anthocyanins and phenolic
acid derivatives extracted from the foliage of one member each of Aechmea
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and Billbergia. Subjects were distinguished primarily by the presence of
7-apiosylglucoside in Aechmea glomerata and 6-hydroxyapiginin glycoside
in Billbergia vittata. Subsequent investigations (e.g., Scogin and Freeman
1984) revealed a variety of additional constituents, some for the ® rst time,
in samples representing diverse genera, including Bromelia, Puya and
Tillandsia. Scogin (1985) also identi® ed some novel anthocyanins in the
corollas of Puya. None of these investigators devoted much attention to
biological functions or implications for plant systematics.
Williams' s (1978) survey exceeds all the others devoted so far to the secondary metabolites of Bromeliaceae. Her inventory, compiled from 61
species representing all three subfamilies, lists a remarkably wide collection
of ¯ avonoid types including ¯ avones, ¯ avonols, C-glycosylated ¯ avones
and 6-oxygenated ¯ avones and ¯ avonols. Such immense chemical diversity
and the extra hydroxylation or methylation at C-6 of the ¯ avones and ¯ avonols suggests uniqueness and exceptional phylogenetic isolation for
Bromeliaceae among Liliopsida.
Flavonols (present in 43% of the species) and ¯ avones (just 13% of the
total) occurred widely through the samples, whereas members of only one
or two subfamilies produced constituents representing the less pervasive
classes of related products. For example, 6-hydroxy¯ avones characterized
Pitcairnioideae and Tillandsioideae, but only certain members of the
second taxon yielded patuletin, gossypetin and methylated 6-hydroxymyricetin derivatives. Several genera demonstrated novel ¯ avonoid pro® les (e.g., Pitcairnia, Tillandsia). A new ¯ avonol, 6,39,59-trimethoxy
-3,5,7-49-tetrahydroxy¯ avone, occurred as the 3-glucoside in Tillandsia
usneoides, and Alcantarea regina contained the exceptional glycoside patuletin 3-rhamnoside. Williams' s ® ndings run counter to traditional views
about evolutionary grades in Bromeliaceae in the sense that the molecular
complexity noted increases beginning with Bromelioideae through
Pitcairnioideae to Tillandsioideae.
Macromolecules
Nucleic acids constitute the richest source of chemical characters for evolutionary analysis. Phylogenies based on DNA structure indicate where,
and ± depending on the reliability of the referenced `molecular clock' ±
when, speciations occurred within clades. Overlain with data on structure,
function and ecology, family trees can reveal the same kinds of information
about speci® c plant adaptations (e.g., Brocchinia as treated above; Fig. 9.5).
Moreover, DNA ampli® cation using polymerase chain reaction (PCR)
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519
technology grants access to nucleotide sequences without jeopardizing rare
biota. It also obviates the need to clone DNA fragments of interest, a laborious process that previously made molecular systematics much more
expensive. In effect, tools originally developed to probe the workings of
cells are no less crucial to the reconstruction of a comprehensive
Bromeliaceae genealogy.
Several features of the DNA molecule account for its extraordinary
utility to address questions about systematics and evolution. First, nucleotide sequences provide an essentially inexhaustible source of relatively
unambiguous characters to reconstruct phylogenies de novo and test congruence with hypotheses implicit in traditional taxonomies. Genealogies
inferred from DNA structure in turn provide frameworks to identify
change in individual and suites of plant characteristics through geologic
time, and determine the sequence of important evolutionary events like the
emergences of absorbing trichomes and phytotelmata. Molecular data typically take one of three forms: maps of restriction sites, extensive nucleotide sequences, and substitutions (insertions and deletions) and inversions
of segments of DNA.
Commercially available endonucleases hydrolyze nucleic acid molecules
at speci® c sites (nucleotide sequences), after which gel electrophoresis
resolves the resulting fragments according to size and net charge. The ultimate product, a map locating the restriction sites along intact molecules,
for example the circular chromosome of the chloroplast (cpDNA), provides a basis to compare the relatedness of genotypes (Fig. 9.17). More
extensive nucleotide sequencing yields correspondingly larger numbers of
characters.
The capacity of speci® c molecular data to differentiate genotypes with
given degrees of identity depends on the genome (chloroplast, nuclear or
mitochondrial) under study and the speci® c locus targeted. The highly conserved chloroplast gene rbcL (ribulose bisphosphate carboxylase large
subunit), for example, yields insights on relationships among families
within orders of ¯ owering plants. Comparisons involving more closely
related organisms, those distinguished by less molecular divergence overall,
require a more variable locus such as parts of the ndhF plastid gene
described below.
Most of the molecular data utilized so far by plant systematists, and
without exception employed to compare bromeliads, come from cpDNA,
which has the following general characteristics (Fig. 9.17). A typical
chloroplast contains 20± 200 copies of a covalently closed, double-stranded
chromosome that, unlike nuclear DNA, lacks associated structural protein
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History and evolution
Figure 9.17. Structural aspects of the chloroplast genome from Nicotiana tabacum
(tobacco). Inverted repeats are indicated by bold regions along the circle. Large and
small single-copy regions are delimited by the inverted repeats. Genes listed on the
outside and inside of the circle are encoded on the A strand and B strand respectively. Split genes are indicated by asterisks (modi® ed from Grierson and Covey
1988).
(histones), and also differs in the ratios of nucleotides present and the
absence of 5-methyl cytosine. Plastid genomes present in most angiosperms
resemble each other in size, conformation, structure and gene content.
Mostly, they range from 120 to 160 kilobases (kb) and consist of three
parts: (1) the asymmetrically positioned, duplicate sequences of approximately 25 kb each, known as the inverted repeats, (2) a unique, single-copy
sequence usually varying from 20 to 30 kb in size, and (3) another, larger
single-copy region of 75± 100 kb.
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521
Figure 9.18. Consensus tree of nine equally parsimonious trees resulting from the
restriction site study of Ranker et al. (1990). Length522 steps; consistency index5
0.86. Numbers along branches refer to characters (mutations) supporting that clade
or taxon. Asterisks indicate homoplasious steps (modi® ed from Ranker et al. 1990).
Chloroplast genomes of higher plants typically contain about 120
densely aligned genes whose products fall into two categories, viz. (1) those
that function in chloroplast protein synthesis, including ribosomal and
transfer RNAs, ribosomal proteins, elongation and initiation factors, and
RNA polymerase subunits, and (2) those loci involved with photosynthesis, e.g., rbcL, thylakoid polypeptide components of photosystems I and II,
proteins of the cytochrome b/f complex, and components of the ATP synthase complex. Chloroplast genes exhibit some prokaryotic features (e.g.,
they possess `bacterial' transcription initiation sequences, i.e., transcription
and translation are concurrent), consistent with the endosymbiotic theory
of eukaryotic cell origin.
Relationships among subfamilies and Bromeliaceae within Liliopsida
Ranker et al. (1990) published the ® rst DNA-based phylogeny for
Bromeliaceae using 16 endonucleases and 10 species ± ® ve Tillandsioideae,
three Pitcairnioideae and two Bromelioideae ± to compare cpDNA restriction site polymorphism (Fig. 9.18). The resulting maps revealed colinearity
between the bromeliad chloroplast genome and those for the majority of
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History and evolution
other land ¯ ora. Genome sizes ranged from 150.6 to 152.9 kb, of which the
inverted repeat accounted for approximately 21.9 kb. Eleven restriction site
mutations and one 1.8 kb length mutation distinguished the bromeliad subfamilies and sometimes members within a subfamily. Most mutations
mapped to that part of the large single-copy region adjacent to one of the
inverted repeats where much variability characterizes the chloroplast
genome.
Parsimony analysis produced a consensus tree comprised of 22 steps
with a consistency index (CI) of 0.86 (Fig. 9.18). That tree prompted three
assertions. First, Tillandsioideae, excluding Glomeropitcairnia, occupies
the basal position in the family. Second, Bromelioideae and Pitcairnioideae
are sister groups and the latter may be paraphyletic. Third,
Glomeropitcairnia lies beyond the balance of Tillandsioideae and possibly
warrants higher taxonomic status as either a separate tribe or subfamily.
Small sample size ± just 10 bromeliads and only 12 phylogenetically informative characters ± and the absence of several key genera (e.g., Brocchinia,
Catopsis) in the analysis precluded broader conclusions.
Clark et al. (1993) used the rbcL gene to assess familial, ordinal and
superordinal relationships among Bromeliaceae and additional monocots
that taxonomists often associate in phylogenies. Sequences obtained from
members of 20 families, seven species in the case of Bromeliaceae, including all three of its subfamilies, were considered (Fig. 9.19). Three conclusions emerged. First, Bromelii¯ orae sensu Dahlgren et al. (1985), which
encompasses Bromeliales, Velloziales, Philydrales, Haemodorales,
Pontederiales and Typhales, is paraphyletic. Conversely, Bromelii¯ orae,
Zingiberi¯ orae and Commelini¯ orae (sensu Dahlgren et al. 1985) comprise
a clade. Third, Bromeliaceae share a closer relationship with Rapateaceae
than with Velloziaceae.
Smith (1934a) turned to phytogeography to support his case for sistergroup relationship between Bromeliaceae and Rapateaceae, while the
results of other studies using morphological characters (e.g., Huber 1977;
Gilmartin and Brown 1987) favor Velloziaceae in that position. Clark and
Clegg (1990) also used rbcL sequences and two methods of data analysis to
try to resolve subfamily relationships in Bromeliaceae. Maximum likelihood analysis supported Bromelioideae and Tillandsioideae respectively as
basal in the family, while parsimony analysis resolved Pitcairnioideae in
this position.
Terry et al. (1997a) investigated phylogeny among the major taxa of
Bromeliaceae using the chloroplast gene ndhF to test hypotheses about
relationships and the evolution of several characters, including some that
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523
Figure 9.19. Family-level relationships within the Bromelii¯ orae/Commelini¯ orae/
Zingiberi¯ orae complex according to unrooted parsimony analysis of a 52-taxon
data set of monocots. The strict consensus of 198 trees generated by Fitch analysis;
length51665 (modi® ed from Clark et al. 1993).
played pivotal roles in family radiation. The gene ndhF consists of approximately 2200 base pairs and encodes a chlororespiratory peptide. Its rate of
change approaches twice that of relatively conservative rbcL. Variable positions among the tested bromeliads occur most abundantly in the 39 half of
the gene, with 55% of all mutations located in the 39-most 41% of the
sequence region (Fig. 9.20). Of 308 unstable positions, 71 (or 23%)
proved informative. Phylogenetic analysis of ndhF sequences produced 120
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History and evolution
Figure 9.20. Map of the chloroplast gene ndhF from Vriesea espinosae with the relative position of priming sites indicated. Coding strand (forward) and complementary (reverse) primers are given above and below the line respectively. Numbers
indicate the 59-most position of the primer relative to the start (position 1 on the
coding strand) in tobacco. Primer sequences are shown.
most-parsimonious trees of 406 steps (CI50.58). Figure 9.21 presents the
resulting majority-rule consensus tree.
Intergeneric divergence values based on rbcL sequences are lower in
Bromeliaceae than for most other families of ¯ owering plants, ranging
from 2.5% for Billbergia macrolepis vs. Vriesea malzinei and Orthophytum
gurkenii vs. Tillandsia complanata to 0.1% for Neoregelia pineliana vs.
Nidularium selloanum. Relatively high genetic identities combined with the
extraordinarily broad interfertilities among some family members accord
with recent, rapid evolution and fossils no older than the mid-Tertiary. The
same plastid gene also provides insight on a broader relationship, viz. a
maximum divergence value of 8.1 between Araeococcus pectinatus and
Stegolepis hitchcockii (Rapateaceae). Still, the identity of the sister group
should be considered unresolved, and the position of Bromeliaceae within
Liliopsida uncertain (Simpson 1988; Duvall et al. 1993; Davis 1995).
Restriction site data for diverse monocot families indicate that a clade
containing Typhaceae exceeds Rapateaceae as the contender for sistergroup status, although Catopsis nutans provided the single reading for
Bromeliaceae (Davis 1995). Timing is equally obscure at this juncture.
Synonymous substitutions that distinguish Bromeliaceae and Rapateaceae
and published mutation rates for ndhF (Wolf 1991) suggest shared ancestry
only about 41 million years ago. A common Eocene stock does match the
primarily Neotropical distributions of both families and those other signs
of relative youth for Bromeliaceae. However, substitution rates in ndhF vary
among families, rendering this gene unreliable to calibrate evolution.
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525
Figure 9.21. The majority-rule consensus tree for the ndhF subfamily analysis. The
number of supporting character state transformations is given below the branch.
Trees are rooted with Stegolepis (Rapateaceae).
Relationships among the bromeliad subfamilies suggested by the ndhF
gene largely agree with those based on Ranker et al.' s (1990) restriction site
data. Both studies reconcile with close affinity between Bromelioideae and
Pitcairnioideae and place Tillandsioideae nearer the base of the family.
Chloroplast DNA sequences further support Pitcairnioideae (sensu Smith
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History and evolution
and Downs 1974) as a paraphyletic grade within which a monophyletic
Bromelioideae arose. Sampling differences probably account for the major
disagreements between these two studies, namely the dissimilar placements
of Brocchinia (omitted from the Ranker et al. study) and Glomeropitcairnia,
in the resulting trees. The ndhF-derived subfamily phylogeny resolves
Brocchinia at the base of Bromeliaceae, well removed from the remainder
of Pitcairnioideae, a locus consistent with the exceptional morphology and
ecophysiology described above, and its recognition by Varadarajan and
Gilmartin (1988a) as a monogeneric tribe within Pitcairnioideae.
Brocchinia' s relegation to a remote, somewhat parallel position relative
to the main bromeliad radiation (Fig. 9.21) raises crucial questions about
family history considering the varied form and diverse ecophysiology
expressed among members of this remarkable genus. Recall that here too,
combinations of phytotelm and nonimpounding shoots and absorbing trichomes underlie capacity to use a variety of substrates for anchorage and
nutrition. Occasional epiphytism (B. tatei, B. hitchcockii) heightens importance for historical perspectives even more given the same habit in occasional Rapateaceae (Epiphyton) and the much higher incidence of this life
style through Bromelioideae and especially Tillandsioideae, with which
Brocchinia shares several ecologically decisive characters (e.g., C3 photosynthesis, phytotelma, absorptive trichomes with radial construction, Fig.
2.5B,H,I).
Perhaps the common ancestor for Bromeliaceae and Rapateaceae, or
whatever other lineage turns out to be the sister group, shared a tendency
to anchor in tree crowns or was already strongly epiphytic and more comparable to tank-equipped Brocchinia and Tillandsioideae than members of
the other two subfamilies. Inspection of Rapateaceae for absorbing trichomes and other features (several members also produce phytotelma) that
underlie arborealism in Bromeliaceae might prove rewarding. However,
some additional conditions will be needed to fully reconstruct the adaptive
history of Bromeliaceae.
Characters grounded in the structure of DNA should eventually provide
the framework needed to polarize those aspects of the bromeliads (e.g.,
phytotelm shoots, CAM) important to adaptive radiation. However, discordance within and between these two kinds of data may oblige assessments of molecular homoplasy and dissections of phenotypes into
components with discrete genetic foundations. In the ® rst instance, uneven
rates of change among the referenced DNA sequences and differences
between these and the tempo at which the characters of interest evolved
may complicate attempts to assign dates to ecologically decisive events. No
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Relationships among subfamilies and Bromeliaceae within Liliopsida
527
less troublesome, the daunting complexity of certain key characters relative
to others (e.g., shoot architecture vs. seeds appendaged or not) militates
against determinations of how synchronously these features and the plant
performances they in¯ uence changed over time. Neotenic Tillandsia illustrates this second problem.
Within subgenus Diaphoranthema, the most miniaturized and shootdependent populations may be leafy and polystichous (e.g., T. bryoides),
fewer leafed and distichous (e.g., T. usneoides), or leafy and distichous (e.g.,
T. capillaris; Fig. 2.1). Heterochrony has not progressed uniformly or
affected certain aspects of development evenly despite the close phylogenetic relationships. All three bauplans incorporate combinations of two
states of each of the same two characters (phyllotaxis and shoot length or,
better yet, number of leafy nodes). Speci® cally, organogenesis was altered
in different ways depending on the lineage and perhaps its environment,
while descendants in every case have become quite small.
Our point is this: the power of a DNA-based phylogeny to impute when
speci® c states of speci® c characters arose and track the assembly and fates
of character suites over geologic time is real and will improve with the
number of nucleotide sequences used to construct the necessary genealogy
(Givnish et al. 1997). However, phenotype must also be understood in
sufficient detail to determine how and when associated performances (e.g.,
degrees of drought-resistance, capacity for soil-free existence) emerged
during bromeliad history. In the case of Tillandsia subgenus
Diaphoranthema, does each of the diverse architectures illustrated by one
or more of its extant lineages represent a response to a distinct kind of
selection or equally acceptable accommodations to life under similar conditions (Fig. 2.1)? Conceivably, discrete components of a common, juvenilized development program were decoupled and reassociated to produce
speci® c architectures that enhance ® tness under different sets of constraints
on plant success (e.g., different kinds of substrates).
Tillandsioideae
Figure 9.22 presents the strict consensus phylogeny based on 48 mostparsimonious trees of 367 steps that Terry et al. (1997b) obtained using
ndhF sequences. Consistent with the broader survey, it supports a monophyletic Tillandsioideae comprised of ® ve primary lineages, viz. Catopsis,
Glomeropitcairnia, a clade containing representatives of Vriesea subgenus
Vriesea, section Xiphion, Vriesea splendens (subgenus Vriesea section
Vriesea) and members of section Xiphion and others assigned to Vriesea
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History and evolution
Figure 9.22. The strict consensus tree resulting from the ndhF study of phylogenetic
relationships in Tillandsioideae. Numbers above the branches are bootstrap values,
while those below (or in parentheses) are decay values. Trees are rooted with
Stegolepis (Rapateaceae). Subfamilial, subgeneric and sectional designations
accord with Smith and Downs (1974, 1977, 1979).
subgenus Vriesea plus the sampled Guzmania and Tillandsia species. Few of
the generic relationships proposed by Gilmartin et al. (1989) receive
support except for the sister-group relationship between some elements of
Tillandsia and Vriesea. By presuming monophyly for Smith and Downs' s
(1977) genera, these authors precluded assessments of paraphyly in
Tillandsioideae assuring that their ® ndings would differ from those of
Terry et al.
ndhF structure places Catopsis and Glomeropitcairnia within
Tillandsioideae, but suggests early divergences, perhaps before those line-
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529
ages (Guzmania, Mezobromelia, Tillandsia and Vriesea) forming the subfamily core differentiated. Substantial isolation for Catopsis seems even
more likely in light of seed structure that differs from that of the other
Tillandsioideae (Palací 1997). Of the six genera recognized by Smith and
Downs (1977), Tillandsia and Vriesea emerge as paraphyletic, Catopsis is
monophyletic according to ndhf, while the status of Glomeropitcairnia and
Mezobromelia remain uncertain pending a larger sample. The strict consensus tree is uninformative regarding the monophyly of Guzmania, while the
majority-rule tree suggests that some of its members lie closer to elements
of Tillandsia than to congeners (Fig. 9.23).
The ndhF gene also corroborates sister-group status for Tillandsia subgenera Pseudocatopsis and Phytarrhiza, although its mapped sequences do
not support monophyly for the latter taxon as suggested by Gilmartin and
Brown (1986). Sampling was inadequate to address the same issue for either
Phytarrhiza or Diaphoranthema. However, ndhF data suggest that some
component of Anoplophytum is the sister group to Diaphoranthema (Terry
et al. 1997b). A shared, xeric habit parallels the close relationship between
Tillandsia subgenera Anoplophytum and Diaphoranthema. Gilmartin
(1983) proposed some relatively xeric element positioned within the groups
represented by subgenera Phytarrhiza or Pseudocatopsis as ancestral to
Anoplophytum and Diaphoranthema.
Most treatments of Tillandsia imply close relationship between subgenera Allardtia and Anoplophytum. Smith and Downs (1977) distinguished
these two taxa using relative stamen length and the presence of plicate ® laments (Fig. 6.1C). Evans and Brown (1989a) examined plication in species
representing subgenera Anoplophytum, Allardtia and Tillandsia and
rejected its utility to circumscribe Allardtia. Distribution of this condition
also persuaded them to question the legitimacy of Allardtia. Subgenus
Allardtia probably also includes components of subgenera Anoplophytum
and Tillandsia and some species previously assigned to Vriesea.
Parsimony analysis of the ndhF sequences resolves a group of nested
relationships between Tillandsia complanata, T. geminiflora and T. bergeri
that denote close phylogenetic affinities for their subgenera (Allardtia and
Anoplophytum). Moreover, subgenera Allardtia and Anoplophytum emerge
as paraphyletic (Fig. 9.22). Too little information exists at this time to determine whether any of the lineages comprising these two taxa share a most
recent common ancestor, and if so, what characters might circumscribe
such a clade. Tillandsia bergeri (subgenus Anoplophytum) exhibits variable
® lament plication and shares a most recent common ancestor with T. tricholepis (subgenus Diaphoranthema) in the ndhF-based phylogeny.
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History and evolution
Figure 9.23. The majority-rule consensus tree from the ndhF study of relationships
in Tillandsioideae showing other compatible groupings. Generic and subgeneric
grouping are as in Fig. 9.22.
Plication characterizes the stamen ® laments of T. geminiflora (Smith and
Downs 1977), but not T. secunda.
ndhF sequences also resolve a well-supported monophyletic group at the
base of Tillandsioideae, exclusive of Catopsis and Glomeropitcairnia, consisting solely of members of Vriesea section Xiphion (Smith and Downs
1977; Fig. 9.22). Most taxonomies recognize the distinctness of the xiphion
vrieseas owing to their usually dull-colored, nocturnal ¯ owers with
included sexual appendages (Fig. 3.5E). Utley (1983) proposed the theco-
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Relationships among subfamilies and Bromeliaceae within Liliopsida
531
phylloid vrieseas as a subgroup notable for secund in¯ orescences bearing
enlarged primary, mostly green bracts subtending ¯ owers with asymmetrically positioned stamens like those of Vriesea atra (Fig. 3.5E). Of those
species traditionally assigned to Vriesea section Xiphion included in the
ndhF analysis, only V. malzinei conclusively emerged elsewhere in the phylogeny, in this case as the sister group of Tillandsia funckiana. Signi® cantly,
of the 65 Vriesea species examined, only two, including Vriesea malzinei,
possess the simple-erect type stigma (Brown and Gilmartin 1989a; Fig.
3.1C). No member of Vriesea section Xiphion inspected so far exhibits this
morphology.
Other notable associations depicted in the ndhF trees include close
affinity between Tillandsia and Guzmania (Figs. 9.22, 9.23). Should this
assignment be correct, the frequently disparaged petal appendage (Fig.
3.1B; Chapter 3) would regain some lost currency as one of the more useful
among the traditional characters to separate Guzmania, Mezobromelia,
Tillandsia and Vriesea. According to the ndhF-derived phylogeny, this
sometimes labile ¯ oral structure (Brown and Terry 1992) distinguishes
Guzmania and Tillandsia from the other genera with only occasional exceptions (e.g., Vriesea espinosae, V. malzinei). Additionally, conglutinate petal
claws and polystichous in¯ orescences would become important to
differentiate clades (e.g., Guzmania from Tillandsia and possibly
Mezobromelia from some components of Vriesea).
Recognition of additional genera seems assured, but revisions should
not be published before supplementing the ndhF ® ndings with sequences
from other parts of the genome and additional information on certain
aspects of reproductive structure. None of the ® ve subgeneric or sectional
circumscriptions examined (i.e., those for which more than one taxon was
examined) quali® es as a clade, a view variously expressed by other authorities who analyzed the group using more traditional characters (e.g.,
Gilmartin 1983; Utley 1983; Gardner 1986b; Gilmartin and Brown 1986;
Evans and Brown 1989a).
Figure 9.24 illustrates the ® rst attempt to use molecular data to determine growing conditions in ancestral habitats relative to the distributions
of related, adaptive features in extant lineages. All of the taxa compared for
ndhF sequences were scored as mesic, semixeric, or xeric types and mapped
over the molecular phylogeny depicted in Fig. 9.23. Again, plant habits, this
time often corroborated by ® eld notes on local climate, provided the basis
for assigning ecostatus. Note that mesic lineages comprise most of the
clades near the base of the subfamily, while some Tillandsia and Vriesea
species characterized by semixeric or xeric pro® les occur distally.
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History and evolution
Figure 9.24. The mapping of water-balance status over the ndhF majority-rule consensus tree for Tillandsioideae. All unresolved nodes are treated as hard polytomies
in determining tree length. The equivocal scorings near the base of the family and
extending to the base of Tillandsioideae re¯ ect uncertainty with respect to mesic or
semixeric scorings. The equivocal scoring of the node supporting some Guzmania,
Tillandsia and Vriesea re¯ ects uncertainty with respect to mesic, semixeric, or xeric
status.
Distributions of lineages representing both habits through the tree demonstrate homoplasy, although change consistently proceeded from less to
greater drought-tolerance much as Benzing and Renfrow (1971b,c),
Gilmartin (1983) and Gilmartin and Brown (1986), and Schimper before
them, proposed for Tillandsioideae.
A second overlay addresses the origin of epiphytism as indicated by the
distributions of the necessary habits, namely the putative phylogenetic
ordering of Pittendrigh' s four ecological/structural types. Figure 9.25 illustrates how the bromeliads with these characteristics distribute across the
ndhF-based phylogeny. Phytotelm forms (Type Three here) appear in every
subfamily, almost certainly independently, and provided the self-sufficiency
required to anchor on more impoverished media like bark and rock. The
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533
Figure 9.25. The mapping of Pittendrigh' s (1948) four ecological types over the
majority-rule consensus tree (Fig. 9.23) for the ndhF gene.
nonimpounding, essentially rootless and trichome-dependent habit exists
only in Tillandsioideae where it probably evolved repeatedly, possibly via
heterochrony as just described.
However, a broader, more fundamental propensity for epiphytism pervades the family. Some Pitcairnia illustrate this condition by rooting in the
canopy unassisted by either absorbing trichomes or foliar impoundments.
Unfortunately, molecular phylogenies lack the capacity to track epiphytism
when this condition occurs embedded in predominantly terrestrial lineages
and unassociated with the features that permit the more specialized forms
to grow in the more arid parts of the canopy habitat. Figure 9.26 illustrates
three plausible relationships between lineages equipped with Types One,
Two and Three habits, all of which, along with Type Four, must be considered evolutionary grades rather than successive stages in a single historical
progression.
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534
History and evolution
Figure 9.26. Three different hypotheses addressing the evolution of Type III
Bromelioideae from Type II ancestors using Pittendrigh' s (1948) four types. (A)
Type II Ananas are more closely related to Type III Bromelioideae than to other
congeners. (B) Ananas is ancestrally Type II. The cross-hatched branch designates
the evolution of the Type II ecological type from a Type I progenitor. The Type II
ancestor subsequently gives rise to epiphytic Bromelioideae in one direction and to
Type I and Type II Ananas in the other. This hypothesis predicts that the distribution of ecological types in Ananas will exist along phylogenetic lines (i.e., the Type
I condition will be synapomorphic in Ananas). (C) The ancestor of Type III
Bromelioideae and Ananas is polymorphic (a population consisting of Type I and
Type II ecological types). The cross-hatched branch designates the origination of
the polymorphic condition from a monomorphic (Type I) progenitor. This ancestor gives rise to polymorphic populations in both directions. In one descendant population, Type II give rise to Type III descendants. Type I and Type II ecological
types persist in the lineage that ultimately gives rise to Ananas. This hypothesis predicts that the distribution of ecological types in Ananas will not necessarily exist
along phylogenetic lines (i.e., polymorphism is symplesiomorphic in Ananas).
Triangles designate cladogenesis within lineages.
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Relationships among subfamilies and Bromeliaceae within Liliopsida
535
Figure 9.27. The mapping of ovary position over the majority-rule consensus tree
for the ndhF gene.
The ndhF phylogeny also imputes homoplasy for a variety of morphological characters often used as taxonomic landmarks, such as ovary position and seed morphology. Events affecting different organs sometimes
occurred in tandem. For example, several lineages characterized by shifting
ovary position also adopted different fruit types, or seed morphology
(appendaged vs. unappendaged), or both. The derivation of Bromelioideae
from within Pitcairnioideae was accompanied by changes in each of these
characters, all apparently occurring along a single branch, suggesting signi® cant character linkage. Assuming the same probability of change for
each of the plant features mapped along any branch in the subfamily
majority-rule tree (Figs. 9.27± 9.29), the probability that all of them
occurred on a single axis by chance is less than 1%, according to the concentrated changes test of Maddison and Maddison (1992).
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536
History and evolution
Figure 9.28. The mapping of fruit type over the majority-rule consensus tree for the
ndhF gene.
Bromelioideae
Data derived from the ndhF gene also provide the ® rst explicit phylogenetic
hypothesis for Bromelioideae built on DNA sequences, and in this case
rooted on genera representing Pitcairnioideae as the sister taxon (Fig.
9.30). Unfortunately, several facts reduce the value of this tree for sweeping conclusions about intrafamilial relationships. First, only 15 of the 29
genera account for the results, and some interesting outliers (e.g., Greigia,
Fascicularia) are absent. Moreover, just one species (Aechmea haltonii of
subgenus Podaechmea) represents the largest and most controversial of the
bromelioid genera. Finally, Bromelioideae clearly exceeds Tillandsioideae,
and possibly also Pitcairnioideae, for varied reproductive morphology.
Nevertheless, Fig. 9.30 illustrates several noteworthy features, most
importantly the resolution of three major clades based on the strict consensus of 136 shortest trees of 157 steps. An unresolved core group contains
11 genera. Among its component taxa, Nidularium, Neoregelia and
Wittrockia probably relate more closely to one another than to any of the
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Relationships among subfamilies and Bromeliaceae within Liliopsida
537
Figure 9.29. The mapping of seed morphology over the majority-rule consensus tree
for the ndhF gene.
other core genera. However, affinities among members of these three taxa,
most of which possess nidulate in¯ orescences (Fig. 3.2A), remain obscure
(Leme 1997), as are the relationships between the entire, apparently monophyletic assemblage and the other core Bromelioideae. Leme (1998a,b) is
currently reorganizing the nidularoid complex employing more characters
± still all morphological ± to ® t a taxonomy expanded to include at least two
new genera (Canistropsis, Edmundoa).
Ananas, Cryptanthus and Orthophytum form still another unresolved
clade positioned basal to the core. Weaker evidence also supports Ananas
as the sister taxon to core Bromelioideae and Cryptanthus and
Orthophytum as sister taxa and basal to the Ananas-core Bromelioideae
clade. Bromelia and Puya form the third and basalmost clade, also unresolved, in the strict consensus tree. Removing Puya (not shown) results in
a strict consensus (120 trees, 142 steps) with identical topology. Puya is an
especially pivotal taxon because of its potential to reveal how the features that distinguish Bromelioideae among bromeliads arose from less
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538
History and evolution
Figure 9.30. A strict consensus of 136 shortest trees of 157 steps for Bromelioideae
based on the ndhF gene and rooted with sister taxon sequences (Dyckia and
Encholirium). Three major clades are identi® ed. An unresolved core group of 11
genera includes Nidularium, Neoregelia and Wittrockia that appear to be more
closely related to one another than to any of the other eight genera.
specialized conditions that continue to characterize Pitcairnioideae (e.g.,
inferior ovary modi® ed for zoochory from a dry capsule).
Pitcairnioideae
Several studies utilizing DNA structure to infer bromeliad phylogeny have
included one or more pitcairnioid species (e.g., Givnish et al. 1997; Terry et
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Relationships among subfamilies and Bromeliaceae within Liliopsida
539
al. 1997a,b). Seed and ¯ ower morphology and additional traditional characters drawn from other reproductive and some vegetative organs have
received more attention in attempts to identify relationships within
Pitcairnioideae (e.g., Varadarajan and Gilmartin 1988a,b). Just one report
deals comprehensively with this subfamily and uses molecular characters ±
although in this case less to address bromeliad taxonomy than to investigate historical shifts in ecophysiology, a goal especially well designed to
target ecophysiologically diverse Bromeliaceae.
Crayn et al. (1999) examined 36 species in 11 pitcairnioid genera to help
determine patterns of change leading from C3 to CAM metabolism in a
clade chosen because these two syndromes occur among closely related lineages (Chapter 4), sometimes even among members of the same genus.
Successful pursuit of questions of this nature requires knowledge of phylogeny as does any attempt to cast an adaptive radiation in geologic time
and evolutionary space. Speci® cally, Crayn et al. sought to determine
whether Pitcairnioideae is monophyletic, and likewise its component
genera, and the evolutionary juxtapositions of these same lineages. An 851nucleotide sequence located near the rapidly evolving 59 end of the matK
locus (1520 base pairs) in the chloroplast genome provided the characters
needed to construct a molecular phylogeny. While their ® ndings fell short
of those required to determine how often and where in the subfamily CAM
types emerged from C3 stock, the data are sufficient to support or contradict certain existing hypotheses in addition to providing some new insights
including directions for further inquiry.
Four of the 10 genera represented in the survey by more than one species
(Brocchinia, Fosterella, Pepinia and Puya) exhibited sequence homologies
consistent with monophyly. Conversely, Navia (two species from morphologically distinct parts of the genus; N. arida and N. phelpsiae) failed to form
a clade. Additionally, Hechtia (four species assessed) may be arti® cial, and
Deuterocohnia meziana fell nearer to closely allied Dyckia and Encholirium
than the other members of its genus also used for the comparisons.
Pitcairnia heterophylla failed to cluster with the other ® ve congeners analyzed, and Pepinia, although similar in vegetative structure and ecology to
many pitcairnias, may not have arisen from within this genus. Givnish et al.
(1997) determined that Brocchinia serrata probably belongs in another
genus, a ® nding which when juxtaposed to the Crayn et al. revelations illustrates how choice and number of samples can in¯ uence answers to questions about phylogeny.
matK sequence homologies among the sampled Pitcairnioideae also
shed light on the broader issues of where Bromeliaceae belongs within
Liliopsida, how its subfamilies relate, and what the genetic divergences
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540
History and evolution
among species may tell us about the age of the family and how recently its
component lineages multiplied. Of the 851 sequence positions examined,
171 or 38% varied just within Bromeliaceae (the analysis also included one
member each of Ananas, Guzmania, Tillandsia and Vriesea), and 72 (8%)
of these sites were cladistically informative. More interesting, maximum
pairwise divergence was just 5.45% between Fosterella penduliflora and
Guzmania monostachia. Similar ® ndings by other investigators using other
genomic loci (e.g., Terry et al. 1997a,b and the ndhF locus) indicate that the
unusually close intrafamilial relationships among bromeliads indicated by
this measure are family rather than gene speci® c. Low mutation rates may
account for these extraordinarily low values compared with those separating the members of other groups of ¯ owering plants; however, they could
also signal rapid speciation. The second possibility, especially if it accompanied recent emergence of family-distinguishing characters, would also
explain the nearly exclusive Neotropical distribution of Bromeliaceae and
the absence of a credible pre-Eocene family record.
Final comments
Despite much continuing ambiguity, consensus is developing on several
points concerning origins, status among the monocots, and the phylogenetic juxtapositions of the higher bromeliad taxa. Bromeliaceae is relatively
isolated within Liliopsida and probably monophyletic as are
Tillandsioideae and Bromeliaceae. Tillandsioideae seems to have branched
off from the rest of the family early in its history leaving Pitcairnioideae and
Bromelioideae more closely related. Brocchinia, or most of its recognized
species, possesses an extraordinary mix of distinguishing characteristics,
unique enough perhaps to justify subfamily status. Features responsible for
the exceptional stress-tolerance and unparalleled capacity to utilize unconventional substrates (e.g., CAM, phytotelma, absorbing trichomes) exhibited by so many Bromeliaceae are sufficiently homoplasious to seriously
challenge attempts at systematic inference.
Still equivocal are the closest relatives of Bromeliaceae, which when identi® ed should allow polarization of important characters and recognition of
evolutionary directions. Examined genomic sequences identify Rapataceae
as the likely sister group of Bromeliaceae, but other candidates exist, and
some of those suggested (e.g., aquatic Mayacaceae; Givnish et al. 1998) by
their own unusual ecophysiology greatly expand the potential selective
pressures that set in motion the modi® cations of structure and function
that underlie current bromeliad success in so many, often demanding hab-
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Final comments
541
itats, and permit the more specialized lineages to deploy carnivory and
trophic myrmecophytism and serve as major resources for extensive forest
canopy biota.
Securement of a sufficiently resolved phylogeny will require analysis of
additional parts of the genome chosen to match rates of evolution with the
hierarchical levels of the taxa being compared. Sampling must also include
more lineages, especially those in problematic groups or apparently rooted
near the base of the family tree (e.g., Brocchinia and other Guayanan
Pitcairnioideae, Catopsis, Glomeropitcairnia) and the putative bromeliad
relatives. Progress has been uneven and the work yet to do is no less so.
Clearly, Bromelioideae presently holds the record for being least known of
the bromeliad subfamilies on many counts. Although several apomorphies
(e.g., berry fruits, gelatinous outer ovular integument) de® ne this clade
among Bromeliaceae, its members encompass considerable, poorly characterized ecological diversity and perhaps more varied vegetative and reproductive organs than present in either of the other two (three?) subfamilies.
Success is also contingent on improved understanding of higher levels of
plant structure and function and especially development. Heterochrony
warrants greater attention than it has been accorded so far ± more species
compared as seedlings and adults relative to morphology and ecophysiology. Additionally, morphometric analysis could more precisely indicate
how faithfully adult architecture matches certain stages of the developmental programs of putative ancestral types. The litany could go much farther.
In fact, progress toward a truly comprehensive synthesis of bromeliad
history is contingent on further advances in virtually all of the subjects considered in the nine chapters just concluded.
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Part three
Special topics
10
Neoregelia subgenus Hylaeaicum
I. RAMÍREZ
Neoregelia, with about 100 species (Luther and Sieff 1996), belongs to subfamily Bromelioideae, and consists of two subgenera with largely nonoverlapping ranges: Neoregelia with about 90 species and subgenus Hylaeaicum
with 10 species. Subgenus Neoregelia is confined to eastern Brazil except for
one species each in northern Venezuela (N. cathcartii) and Amazonian Peru
(N. johnsoniae). Subgenus Hylaeaicum is entirely Amazonian in parts of
Colombia, Venezuela, Peru, Ecuador and Brazil.
Neoregelia is distinguished from the other bromelioid genera with
nidular inflorescences (Canistrum, Nidularium and Wittrockia) by its asymmetric sepals and lack of petal appendages (Leme 1998a,b). However, more
recent studies (Ramírez 1991, 1994) have determined that petal appendages
occur in members of subgenus Hylaeaicum, and Leme (1997) reported
these same organs in subgenus Neoregelia (N. carolinae), indicating need to
re-evaluate the taxonomic utility of this character.
Taxonomic problems
Nidularium eleutheropetalum and N. myrmecophilum were successively
assigned to different sections of Nidularium, and the genera Karatas and
Aregelia until in 1890 Lindman placed them in genus Regelia, which he
created by elevating the status of Nidularium subgenus Regelia Lemaire. In
1891 Kuntze had proposed the name Aregelia as a nomen novum for
Nidularium, so that its typification must be identical to that of Nidularium.
Therefore Mez’s decision to use Aregelia for a genus segregated from typical
Nidularium is invalid.
Genus Regelia was named after the German botanist A. von Regel, who
served as superintendent of the Imperial Botanic Gardens in St Petersburg,
Russia. Because the name Regelia had already been assigned to three
545
546
Neoregelia subgenus Hylaeaicum
species of Myrtaceae, Smith (1934b) created the name Neoregelia, considering Regelia Lindman and Aregelia Mez, 1896 non Kuntze, 1891, to be
synonyms. Smith and Downs (1979) combined Nidularium subgenus
Regelia, Karatas section Regelia, and Aregelia subgenus Eu-Aregelia under
Neoregelia.
Subgenus Hylaeaicum is distinguished from subgenus Neoregelia by its
pedicellate flowers, but this delimitation is problematic. My investigation
indicates that additional features including position, length and origin of
the stolons, bract phyllotaxis (distichous vs. spiral), degree of connation
of the sepals, presence of petal scales, and stigma shape also help circumscribe the two subgenera.
Smith (1967) erected Neoregelia subgenus Amazonicae, citing Nidularium
eleutheropetalum as the type, to include those species of Neoregelia with
free petals and a distinct pedicel and restriction to Amazonia. In 1976
Smith resurrected the name Hylaeaicum proposed by Ule in 1907 for
Nidularium eleutheropetalum and N. myrmecophilum. Smith and Downs
(1979) placed Nidularium subgenus Hylaeaicum Ule and Aregelia subgenus
Hylaeaicum (Ule) Mez in synonymy with Neoregelia subgenus Hylaeaicum.
Moreover, they noted that Neoregelia aculeatosepala alone possesses a distinct pedicel, eliminating one of the best taxonomic markers for subgenus
Neoregelia. More recently, Leme (1997) transferred N. aculeatosepala to
Aechmea (A. aculeatosepala) based on the presence of erect petals, serrate
sepals, apically obtuse-cucculate, triporate pollen, creased leaves between
sheath and blade, and an unbroken crescent or a V-shaped fold clearly
visible on the abaxial surface. Also characteristic is the fleshier fruit containing an abundant, sweet gelatinous matrix.
Ramírez’s (1991, 1994) studies on vegetative and floral morphology
suggest that subgenera Neoregelia and Hylaeaicum may not be closely
related and that Neoregelia is polyphyletic or paraphyletic. H. A. Luther
(personal communication) has indicated that subgenus Hylaeaicum may
share ancestry with members of Aechmea subgenus Aechmea. Leme (1997)
also considers Hylaeaicum distinct from subgenus Neoregelia and closer to
Aechmea and Canistrum (because of the bluish fruits). I believe that subgenus Hylaeaicum could be related to Aechmea subgenus Lamprococcus, with
which it shares petal scales, apical placentation, stoloniferous habit, and
Amazonian distribution. Similarities, especially the nidulate inflorescence,
with subgenus Neoregelia are probably homoplasious. The systematics of
the bromelioid genera with nidulate inflorescences warrant further study to
determine whether this condition evolved more than once within
Bromelioideae. Molecular data will be especially informative.
Vegetative morphology
547
Ecology and geographic distribution
Species of subgenus Hylaeaicum mostly inhabit Amazonian rainforests
except for a few members that range through pre-montane rain or cloud
forests on the eastern slopes of the Andes. About 80% of the species occur
between 50 and 600 m. Neoregelia aculeatosepala alone inhabits cloud
forests above 1000 m, consistent with Leme’s decision (1997) to transfer it
to Aechmea. Distributions suggest that subgenus Hylaeaicum originated in
Amazonian Peru and Ecuador.
Species of Hylaeaicum belong to Pittendrigh’s (1948) ecological Type
Two (Table 4.2), although epiphytism prevails except for the occasional terrestrial or humicolous population on well-drained soil. Finer details of
shoot architecture follow two patterns. Shoots in one case feature inflated
leaf sheaths forming a ‘multitank’ (sensu Benzing 1980) that impounds
water and litter. Trichomes occur sparsely over the leaf sheath surfaces, and
most species attract nesting ants (Davidson 1988; personal observation and
notes on herbarium labels).
Members of the second group inhabit rain or cloud forests at moderately
high elevations (800–1600 m). Here, the leaf sheaths form small impoundments that hold almost no water (‘single tank’ sensu Benzing 1980), and the
leaves are thinner and covered by a dense mantle of trichomes distinct from
those of the first group. Members are always stoloniferous epiphytes.
Cytology
Published counts for Neoregelia match the basic chromosome number (2n
550) of the family (N. spectabilis, N. concentrica, N. cyanea and two
unidentified species; Marchant 1967). Only one number exists for
Hylaeaicum (Ramírez 1991; Neoregelia peruviana, 2n550).
Vegetative morphology
Leaf sheaths that vary in morphology and disposition cover the often long
stolons. Typically nidulate inflorescences are usually surrounded by
brightly colored young leaves. Most species form colonies of several to
many ramets (up to 300–400 for N. pendula var. pendula and N. tarapotoensis), suspended from branches or the trunks of trees, or over rocks or cliffs.
Species endemic to Andean foothill forests in Ecuador and Peru tend to
form compact, small ramets. Stolons are exceptionally slender and elongate
(e.g., N. tarapotoensis). Natives of lowland rainforests tend to form larger
548
Neoregelia subgenus Hylaeaicum
funnelform shoots with the foliar sheaths abruptly broadened to form a
large phytotelma. Colonies usually consist of a few ramets interconnected
by relatively short, stout stolons.
Leaf blades are narrow-triangular or ligulate, rarely whip-like, and the
margins spiny; color is mostly green, but some red forms of N. eleutheropetala occur in Colombia (Leticia) and Ecuador (Morona-Santiago).
Particularly ornamental stock are growing at the Marie Selby Botanical
Gardens in Florida, preparatory to flowering for identification.
Trichomes
The structure of the trichomes on the leaf sheath suggests the presence of
two groups of species in the subgenus (Fig. 2.6). Group One, which I
describe as the ‘pliable type’, mostly includes species native to low elevations. Shields are radial, containing eight, usually quadrangular ring cells
that sometimes feature irregular shapes and asymmetrical arrangements.
Wings are scarcely developed in N. eleutheropetala, N. leviana, N. myrmecophila, N. rosea and N. stolonifera, but well defined in N. wurdackii.
Densities vary without discernible patterns.
The second group, my ‘rigid type’, mostly includes species from the
Andean foothills. Trichomes lack shields with the degree of organization
just described. Instead, component cells differ in size and shape. Abundant
trichomes on both leaf surfaces produce a highly reflective indumentum
(e.g., N. peruviana, which forms small rosettes throughout its range in Peru
at 250–550 m).
Inflorescences
Members of subgenus Hylaeaicum produce terminal, usually simple inflorescences on determinate shoots (Chapter 2; Fig. 3.5B). Some species
undergo additional branching on the periphery of spent inflorescences,
resulting in multiseason fruiting by the same ramet (e.g., both varieties of
N. eleutheropetala, N. myrmecophila and probably N. leviana, N. margaretae; Leme 1997).
Species of Neoregelia subgenus Hylaeaicum advertise by developing colorful foliage (Fig. 2.13F) at anthesis, specifically: bright red, dark red or
dark pink (e.g., N. margaretae, N. rosea, N. pendula var. brevifolia, N. eleutheropetala var. bicolor, N. myrmecophila), purple (e.g., N. leviana, N. stolonifera, N. pendula var. pendula) or green inner leaves (e.g., N.
eleutheropetala var. eleutheropetala, N. mooreana, N. peruviana, N. tarapotoensis). Sometimes the whole ramet or just the inner leaves become red
Reproductive biology
549
depending on exposure (N. eleutheropetala; H. Luther, personal communication).
Floral morphology
Certain members of subgenus Hylaeaicum possess petal scales that occur
in two forms (Ramírez 1994). The scale apex is either acute or fimbriate, or
comprised of finger-like projections (only N. pendula var. brevifolia of all
the species studied).
Species of subgenus Neoregelia studied by Brown and Gilmartin (1989b)
possessed conduplicate-spiral stigmas (Figs. 3.1C, 12.1). Mez (1934–35)
reported densely capitulate, contorted stigmas for Hylaeaicum, Canistrum
and Nidularium. Three stigma architectures (Brown and Gilmartin 1989b)
have been reported for subgenus Hylaeaicum (Ramírez 1994). The simpleerect type was observed in Neoregelia leviana, N. myrmecophila, and N.
pendula var. brevifolia, and the conduplicate-spiral form in N. tarapotoensis, N. mooreana, and N. margaretae. Neoregelia stolonifera and N. eleutheropetala var. eleutheropetala exhibit convolute-blade morphology (but see
Leme (1997) who failed to record this condition among these species).
Stigma type does not parallel other taxonomic characters within subgenus
Hylaeaicum.
Reproductive biology
Flowers bear white petals and green sepals except for N. pendula var. brevifolia, which has white sepals and N. eleutheropetala var. bicolor with its redtinged sepals and floral bracts. Anthesis usually occurs in early morning,
and flowers remain open for one or rarely two days. Stamens lie close to the
stigma, and both are included, although the stigma lies 1–2 mm below
the stamens in some species. Spreading corollas typically protrude above
the characteristic flat inflorescence.
High fruit set in closed greenhouses suggests that most of the taxa (7 out
of 10 studied) are either autogamous or agamospermous, in contrast to
subgenus Neoregelia where allogamy prevails (Smith and Downs 1979).
Close contact between stamens and stigma in most subgenus Hylaeaicum
species accords with autogamy.
Number of offshoots per parent ramet varies with the species. One is
typical for many populations (e.g., both varieties of N. eleutheropetala), but
N. pendula var. brevifolia regularly produces five.
Neoregelia subgenus Hylaeaicum illustrates at least three distinct architectures, each associated with a specific pattern of sympodial branching.
550
Neoregelia subgenus Hylaeaicum
The first model features small ramets, one to five in number, derived from
each parent ramet. Pendulous ramets hang by long, slender, wiry stolons
covered by polystichous, spineless, usually dry, brown bracts (e.g., N.
pendula, N. tarapotoensis, N. peruviana). Ranges are narrow and confined
to the eastern slopes of the Ecuadorian and Peruvian Andes. The second
model is characterized by somewhat pendulous, short, stout stolons
covered by mostly green, rarely brown, spiny, polystichous or distichous
bracts (e.g., N. stolonifera, N. mooreana, N. eleutheropetala and N. myrmecophila). Each parent ramet of Neoregelia stolonifera produces a pair of
offshoots on straight, elongate, but stout stolons leading to an expanding
regular, dichotomous arrangement. The third model features ramets that
branch just once and remain connected by short, stout stolons covered by
strongly distichous, green, spiny sheaths bearing small, but conspicuous,
rigid and pungent foliar lamina. Interconnected ramets are slightly pendulous to scandent (e.g., N. margaretae, N. leviana, N. wurdackii and N. rosea).
Ramets of some cultivated species wither after one or two years, and may
serve as seed beds for undispersed progeny (e.g., N. leviana).
Like many other Bromelioideae, morphology and fruit color and leaf
display suggest that members of subgenus Hylaeaicum rely on birds to disperse. Inner leaves are tinged with bright red, pink or purple, and the sepals
become blue or violet. Ovaries are typically white or green, and the fruit
protrudes above the infructescence heightening its visibility (Fig. 3.6F).
Ripe berries readily detach.
Davidson (1988) reported dispersal by ants for N. eleutheropetala whose
seeds contain attractive monoterpenes and aromatics (Seidel et al. 1990;
Chapter 6). Methyl-6-methylsalicylate, one of these monoterpenes, is
present in the mandibular glands of Camponotus femoratus, consistent with
Ule’s (1906) hypothesis that nest-garden Bromelioideae promote seed carriage by mimicking ant brood (Davidson 1988).
Continuing taxonomic problems
Clearly the affinities of members of Neoregelia subgenus Hylaeaicum
remain poorly resolved, and will remain so without additional inquiry.
Closer scrutiny of morphology would help, but molecular data are essential not only to identify where subgenus Hylaeaicum belongs in its subfamily, but also to sort out the relationships of large, artificial bromelioid
genera like Aechmea. At this point, we can say with fair confidence that the
10 members of subgenus Hylaeaicum do not belong in genus Neoregelia,
but whether assignment to some other genus or a new one is warranted
remains less certain.
11
Cryptanthus
I. RAMÍREZ
Cryptanthus (Bromelioideae) is endemic to southeastern Brazil, strictly terrestrial, and ranges from Paraíba to Rio de Janeiro states, with one species
in Goiás State. Its 41 species inhabit wet forests, restingas, caatingas and
campos rupestres, occurring from sea level to about 2000 m. This genus
differs from all others in the family by its consistently low chromosome
number (n517) and often andromonoecious flowers with simple-erect
stigmas (Fig. 3.1C).
Ramírez (1996) recently supported the case for the recognition of two
subgenera proposed by Mez (1896) with geographical, morphological and
ecological data. Characters that distinguish the two taxa are summarized
in Table 11.1.
Members of subgenus Cryptanthus are subdivided into five sections,
members of which occur in Rio de Janeiro, Espirito Santo, Minas Gerais,
Bahia, Sergipe, Pernambuco, Paraíba and Goiás states (Fig. 11.1). Leaves
of some of these species possess a mid-longitudinal region thickened by a
succulent, many-layered hypodermis. Reproduction tends to occur primarily by stolons capable of expanding individual genets to form large colonies
(Figs. 2.11C,D, 2.18C).
Members of subgenus Hoplocryptanthus occur in Espirito Santo State,
except for four species native to Minas Gerais. Fruit set is more common in
this group compared with subgenus Cryptanthus (evident on herbarium
collections and among cultivated plants).
Ramírez (1996) tested Brown and Gilmartin’s (1989a) hypothesized
chromosome number evolution and related implications for phylogenetic
relationships within Bromeliaceae (Chapter 9). Brown and Gilmartin proposed that the low number of chromosomes in Cryptanthus (n517 or 18)
could have originated by descending aneuploidy or constitutes the ancient
tetraploid condition according to the scheme illustrated in Fig. 9.10.
Determinations of nuclear DNA content for species with n517 or 18
551
552
Cryptanthus
Table 11.1. Characters that distinguish the two subgenera of Cryptanthus
Characteristic
Habit
Breeding system
Flower fragrance
Corolla shape
Petal blade shape
Stigma lobes
Pollen surface
Seed number
Seed size
Habitat
Elevation
Subgenus Cryptanthus
Subgenus Hoplocryptanthus
Mostly acaulate
Andromonoecy
Usually absent
Open, reflexed petals
Oblong or narrow elliptic
Spreading
Reticulate
Relatively low (c. 8)
Relatively large
Restingas, caatingas
lowland rainforest
0–700 m
Mostly caulescent
Hermaphroditism
Usually present
Campanulate or flat
Orbicular or wide elliptic
Connate
Smooth or finely reticulate
Relatively high (c. 40)
Relatively small
High-altitude grasslands,
montane forests
800–2000 m
(Cryptanthus) and others characterized by n525 (other Bromelioideae)
using flow cytometry accorded with descending aneuploidy (Ramírez
1996).
Additional studies on seeds (Gross 1988a) and septal nectaries (Böhme
1988) support primitiveness for Cryptanthus, but the presence of andromonoecy, fragrant flowers, a simple-erect stigma and CAM metabolism (e.g.,
Medina 1990) suggest otherwise. Should Brown and Gilmartin’s (1989a)
proposal that the low chromosome number in Cryptanthus reflects ancient
tetraploid status (hypothesis two) be accepted, the genus should be elevated
to subfamily status (Cryptanthoideae).
I propose retention of Cryptanthus in Bromelioideae as an exceptionally
derived genus with Orthophytum as its sister group according to cladistic
analysis (Ramírez, in preparation) and some DNA sequence data (Terry et
al. 1997a). Additional molecular data should help confirm Cryptanthus as
a clade within Bromelioideae.
Cryptanthus
553
Figure 11.1. Distributions of the two subgenera of Cryptanthus. w, subgenus
Cryptanthus; d, subgenus Hoplocryptanthus.
12
Tillandsioideae
W. T I L L
Tillandsioideae are mostly rosulate herbs characterized by entire leaf
margins, radially organized peltate trichomes (Fig. 2.7), usually superior
(or nearly so) ovaries, and three-parted capsules that contain plumoseappendaged seeds (Fig. 3.6J; Wittmack 1888; Baker 1889; Mez 1894, 1896,
1934–35; Harms 1930; Smith and Downs 1977; Rauh 1990). Stigma
morphology varies more than in the other two subfamilies, with at least five
different types present (Brown and Gilmartin 1989b; Gortan 1991; Figs.
3.1C, 12.1). Pollen morphology is similarly variable (Fig. 12.2). Grains are
predominantly sulcate with a distal germination region, and represent the
diffuse sulcus, insulae-type, operculum-type and Vriesea imperialis-type
(Halbritter 1992). Catopsis is exceptional with its simple sulcus, while
inaperturate pollen occurs in some Guzmania species. This subfamily comprises the genera Alcantarea (16 spp.), Catopsis (21 spp.), Glomeropitcairnia
(2 spp.), Guzmania (176 spp.), Mezobromelia (9 spp.), Racinaea (56 spp.),
Tillandsia (551 spp.), Vriesea (187 spp.) and Werauhia (73 spp.) (Smith and
Downs 1977; Utley 1983; Till 1984, 1992b, 1995; Kiff 1991; Grant 1993a,b,
1994a,b, 1995a,b; Spencer and Smith 1993; Luther and Sieff 1996; Till et al.
1997).
According to Smith and Downs (1977), Spencer and Smith (1993) and
Grant (1995a), the genera, subgenera and sections of Tillandsioideae can
be distinguished using the following key:
1
Ovary only half superior; seeds equally plumose-appendaged at both
ends; flowers polystichous; petals free, bearing two scales at base
.................................................................................Glomeropitcairnia
1* Ovary nearly or quite superior; seeds plumose at the base or apex or
largely on the base and only slightly on the apex; petals free or conglutinated, naked or with basal scales ......................................................2
555
556
Tillandsioideae
Figure 12.1. Stigmas of selected Tillandsioideae (courtesy of Gunter Gortan). All
scale bars50.5 mm. (A) Catopsis nutans, simple-erect. (B) Guzmania sanguinea,
convolute-blade. (C) Tillandsia bergeri, simple-erect. (D) T. lindenii, coralliform,
view from above. (E) T. lindenii, view from below. (F) T. castellanii, simple-erect. (G)
Tillandsia 3 polita, conduplicate-spiral. (H) Vriesea simplex (section Vriesea), convolute-blade. (I) Werauhia gigantea, cupulate.
Tillandsioideae
2
557
Appendage of the seed largely apical, folded at maturity; sepals strongly
asymmetric in most species; ovules with an apical tuft of cellular
strands; flowers in at least slightly more than two ranks, unisexual in
some species; leaves usually cretaceous-coated ........................Catopsis
2* Appendage of the seed wholly or largely basal, straight at maturity;
sepals symmetric or if asymmetric, then the ovules unappendaged and
obtuse; flowers always hermaphroditic................................................3
3 Petal claws conglutinated into a tube, equaling the sepals or rarely the
petals entirely included in the sepals; spikes mostly with polystichous
organization; ovules cylindric, obtuse; seed coma usually of various
shades of brown .................................................................................4
3* Petal claws free or with a very short tube exceeded by the sepals; flowers
distichous in most species; ovules usually with an apical appendage;
seed coma usually white......................................................................5
4
Petal claws naked ..................................................................Guzmania
4* Petal claws bearing scales on the inside...........................Mezobromelia
5
Petals bearing scales on the inside.......................................................6
5* Petals naked........................................................................................9
6
Stamens exserted and stigma of the conduplicate-spiral type morphology; ovules appendaged .........................Tillandsia subgenus Tillandsia
6* If stamens exserted then the stigma not of the conduplicate-spiral type
morphology ........................................................................................7
7
Seed with the apical appendage divided into a short coma; petals linear,
usually 10–15 times longer than wide, soon flaccid and drooping; ovules
appendaged .........................................................................Alcantarea
7* Seed with the apical appendage minute and undivided; petals shorter,
elliptical, only 5–10 times longer than wide, firm and remaining more
or less erect after anthesis ...................................................................8
8 Flowers with brilliant coloration in most species, bright yellow, orange
or red, rarely dulled to white, light yellow or light orange; the adaxial
petal pair arranged basally with respect to the abaxial; petal appendages tongue-shaped; stigma usually with the convolute-blade type
558
Tillandsioideae
morphology; ovules appendaged ...............................................Vriesea
a Stamens included; floral bracts mostly dull green or brownish
................................................................................section Xiphion
a* Stamens exserted; floral bracts mostly brightly colored with red,
orange or yellow ......................................................section Vriesea
8* Flowers generally dull in color, white, greenish white, light green, yellowish green, yellow or light orange; the adaxial petal pair arranged apically with respect to the abaxial; petal appendages dactyloid with 1–5
fingers of varying length; stigma with the cupulate type morphology;
ovules not or barely appendaged............................................Werauhia
a Inflorescence simple or compound; when compound, the inflorescence is classically bipinnate or tripinnate, and the lateral branches
exceed the primary bracts .....................................section Werauhia
a* Inflorescence compound, though appearing to be simple in some
species (a pair of flowers indicates a reduced lateral branch), those
that appear simple have only pedicellate flowers; lateral branches
usually shorter than, but in some species exceeding, the subtending
primary bracts..........................................................section Jutleya
9 Sepals asymmetric, free or nearly so, broadest near the apex, not over
12 mm long; ovules obtuse .....................................................Racinaea
9* Sepals symmetric or if slightly asymmetric, then ovate or lanceolate and
broadest below the middle, free or variously connate, usually longer
than 12 mm ...........................................................................Tillandsia
a Stamens included in the corolla, equaling the petals or shorter
......................................................................................................b
a* Stamens exserted from the corolla, exceeding the petals ................e
b Style slender, much longer than the ovary; filaments from equaling
the claw to equaling the entire petal ..............................................c
b* Style short and stout; stamens deeply included in the corolla........d
c Stamens exceeding the claw of the petal; filaments straight; ovules
usually appendaged............................................subgenus Allardtia
c* Stamens about equaling the claw of the petal; filaments
strongly plicate in many species; ovules appendaged or obtuse
..................................................................subgenus Anoplophytum
d Petal blades broad, conspicuous; leaf blades flat or terete, green
or cinereous-lepidote, petal color mainly blue-violet; ovules
obtuse (mesic members) or short appendaged (xeric members)
......................................................................subgenus Phytarrhiza
Anatomy and morphology
559
d* Petal blades narrow, inconspicuous; leaf blades terete, densely
cinereous-lepidote, petal color mainly yellowish or brown; ovules
short appendaged...................................subgenus Diaphoranthema
e Petals erect at anthesis or nearly so, relatively firm; leaf blades narrowly triangular in most species; ovules distinctly appendaged
.........................................................................subgenus Tillandsia
e* Petals subspreading at anthesis and rapidly becoming flaccid; leaf
blades lingulate to narrowly triangular, ample; ovules appendaged
or obtuse ................................................subgenus Pseudalcantarea
Anatomy and morphology
Roots
Roots are usually present, simple or branched, and often reduced to holdfasts (Tomlinson 1969; Downs 1974) that sometimes secrete a ‘brown
mastic’ (Schimper 1884; Wittmack 1888) or gum-like (Chodat and Visher
1916; Rauh 1990) substance. According to Brighigna et al. (1990), the
adhering roots secrete lipo-polysaccharides and bear unicellular hairs.
Adult Tillandsia usneoides usually lacks roots. Generally, the extent of
rooting is inversely related to trichome density, leaf succulence and
impoundment capacity (Benzing 1980). Roots occasionally develop on
inflorescences (Tomlinson 1969), especially in certain tillandsias (e.g., T.
latifolia, T. secunda, T. somnians).
The primary root, if present, is quite short and covered by an endostome
cap (Downs 1974; Gross 1988a,b). A crown of root hairs develops in a few
species (e.g., Vriesea fosteriana; Gross 1988b). Adventitious roots appear
early, and unlike the primary root bear typical caps (Fig. 2.15) and possess
a thin rhizodermis. Roots of the more mesic species produce hairs. The
hypodermis (5exodermis of Tomlinson 1969) consists of a multiseriate
layer of suberized cells (Schimper 1884; Tomlinson 1969). The outermost
cortical layers immediately within the hypodermis form a wide sclerotic cylinder which can be more peripheral (e.g., Tillandsia baileyi, T. geminiflora,
Vriesea fenestralis), or central as in Catopsis morreniana, Guzmania monostachia, G. nicaraguensis, G. zahnii, Tillandsia aeranthos, T. cyanea and T.
tricolor (Strehl and Winkler 1983). The central cortex is parenchymatic and
sometimes starch-filled with the inner cortex lacunose. The endodermis is
uniseriate and composed of uniformly thickened cells (Tillandsia, Vriesea;
Meyer 1940). Pericycles are one or two-layered and thin-walled, rarely with
tertiary thickenings in some Tillandsia species (Meyer 1940). The primary
560
Tillandsioideae
vascular system is an exarch protostele (Downs 1974) with the number of
arches reduced in the epiphytes (Meyer 1940). Roots originate in the meristematic layer (pericambium5pericycle) between the stem cortex and
central cylinder (Tomlinson 1969) and remain within the cortex of the stem
for some distance before emerging (Schindler 1957; Tomlinson 1969; Rauh
1990; Chapter 2; Fig. 2.15). Intracauline roots strengthen the stem
(Borchert 1966), and may largely displace the cortical parenchyma
(Tomlinson 1969). Vascular tissue tends to be reduced in roots specialized
for anchorage on bark and rock (Harms 1930). Phloem is reduced more
than the xylem tissue in the most stress-tolerant Tillandsia species (Downs
1974). Vessel element perforations are occasionally simple, but usually scalariform (Cheadle 1955; Goldberg 1989; Fig. 2.21).
Stems
Leafy stems are usually short, the foliage congested, and growth is typically
negatively geotropic (Fig. 2.10). Less often shoots are more caulescent, but
the leaves are just as densely packed (Fig. 2.1). Growth of the elongated
types can be ageotropic (Tomlinson 1969). A small group of reduced
Tillandsia species exhibits distichous phyllotaxis (mainly subgenera
Diaphoranthema and Phytarrhiza; T. albertiana). Stolons equipped with
scale leaves are produced by several species (e.g., Tillandsia juncea, T. espinosa). Stolons, rhizomes and leafy stems exhibit similar anatomy.
Stems are consistently differentiated into a cortex and a central cylinder
(Fig. 2.15; Boresch 1908; Meyer 1929; Tomlinson 1969; Downs 1974).
Vascular cambia are absent, but a periderm (cork tissue) may develop from
secondary meristematic layers in older parts of stems and around leaf scars
and wounds (Tomlinson 1969; Chapter 2). A thin cuticle covers a uniform
epidermis made up of cells containing a prominent silica body (Fig. 4.23I).
Stomata are absent and the peltate hairs are restricted to regions immediately above the leaf insertions (Tomlinson 1969). The cortex is narrow and
tends to become lignified and further rigidified by leaf traces and intercauline roots (Fig. 2.15; Tomlinson 1969; Downs 1974; Benzing 1980). Gum
and mucilage occur throughout the stem interior.
Shoots, and occasionally the entire plant, are mostly determinant with
apical meristems finishing growth by producing an inflorescence (Fig. 2.3).
The exceptional monocarpic species (e.g., Tillandsia makoyana) fruit
without producing axillary ramets. Most species produce successive determinate shoots by sympodial branching (Rauh 1990; Fig. 2.3A). Occasional
individuals (depending on the population) of some of the monocarpic
species produce ramets (e.g., Tillandsia utriculata).
Anatomy and morphology
561
Inflorescence axes
The inflorescence is usually elevated above the leaves on a stem that bears
bracts or less reduced leaf-like appendages (bracts); rarely the entire structure is sessile or multiple (e.g., Tillandsia complanata, T. multicaulis). Most
axes are straight or flexuose (rarely sinuose), terete or angled, or rarely
excavated. Cortex and central cylinder are clearly differentiated. Vascular
bundles are more regularly distributed through cross-sections than in leafy
stems. The two types of inflorescences are distinguished by bundles that are
either isolated and scattered, with those near the periphery narrower, but
surrounded by more massive fibrous sheaths compared with the others
occupying the central region (e.g., Guzmania), or the bundles at the periphery of the central cylinder are embedded in a sclerotic cylinder that delimits the cortex, while those deeper in the axis possess a complete fibrous
sheath (e.g., Catopsis, Tillandsia, Vriesea). Several species of Vriesea
possess vascular bundles without sclerenchyma sheaths. Species less easily
assigned to either type occur in Tillandsia subgenera Anoplophytum,
Diaphoranthema and Tillandsia, and Guzmania (Tomlinson 1969).
Trichomes densely invest some inflorescences, especially those of the xerophytes.
Leaves
Leaves are always entire, and, except for the most reduced forms, usually
differentiated into a sheath and a blade (e.g., Fig. 2.7I). An intercalary meristem located just above the base generates the blade (Benzing 1980).
Distinct midribs are absent. Leaves of seedlings and juveniles are narrowly
triangular to filiform with typically an acute (Tillandsia) or rounded
(Vriesea) apex, while adults tend to produce more lingulate foliage.
Heterophylly can be pronounced (Mez 1896; Harms 1930; Smith and
Downs 1977; Adams and Martin 1986a,b,c; Fig. 4.9). The foliage of mesic
taxa is thin and the mesophyll made up of relatively small, densely cytoplasmic cells. Blades are well developed and green or cyanic. Sheaths typically contain enough tannins to impart dark color (Tomlinson 1969).
Trichomes are often restricted to the adaxial surfaces of the sheaths of the
phytotelm forms. Foliage of the xerophytic species is thickened by the presence of considerable colorless water storage tissue (Horres 1995) and large,
green vacuolate cells equipped for CAM photosynthesis (Fig. 2.10). Blades
are often narrowed above the pale sheaths. The indumentum of these drygrowing taxa is more or less confluent and uniform over the entire leaf
(Type Five). Rarely, spirally inrolled leaves provide holdfast (e.g., Tillandsia
562
Tillandsioideae
duratii; Fig. 2.10L). Bulbs (composed of succulent leaf bases) characterize
a few species (e.g., T. andreana, T. fuchsii). Pseudobulbs (composed of
thinner, inflated leaf bases) with cavities between adjacent leaf bases sometimes harbor ant colonies (Benzing 1970a; Longino 1986; Eshbaugh 1987;
Fig. 8.5).
Leaf anatomy varies greatly depending in large part on the habit of the
subject (Chapter 2). Xeromorphy consisting of thickened cuticles and epidermal cell walls and large vacuolate CAM-type cells sometimes combined
with water-storing hypodermal layers characterize many succulent
Tillandsia and a few Vriesea species. The more mesophytic types possess
thinner foliage with the mesophyll differentiated into a central chlorenchyma between relatively thin hypodermal tissues. Cuticles are thin and
smooth (Harms 1930) or granular in Tillandsia ionantha (Tomlinson 1969)
or folded in Tillandsia hamaleana and Werauhia gladioliflora (Barthlott and
Ehler 1977), and sometimes augmented by epicuticular waxes (Catopsis,
Fig. 5.3A; Guzmania, Tillandsia; Tomlinson 1969; Barthlott and Ehler
1977; Frölich and Barthlott 1988) that at least sometimes contain a steroid
fraction with oestrogenous activity (Hegnauer 1963).
Tillandsioid trichomes (Fig. 2.7) consist of two foot cells, a uniseriate
stalk dominated by the distal dome cell, and a shield comprised of a central
disk and a peripheral wing with the component cells regularly arranged
according to the formula 418132 in Catopsis, Glomeropitcairnia,
Guzmania, Tillandsia subgenera Allardtia and Vriesea and genus Werauhia,
418164 in Glomeropitcairnia, Guzmania, Tillandsia subgenus Phytarrhiza
(mesic), Vriesea and Werauhia, 418116132 in Catopsis and Guzmania,
4 18132164 in Catopsis, 418116164 in Tillandsia and Vriesea section
Xiphion, and 418116132164 in Guzmania and Tillandsia subgenus
Tillandsia (Tomlinson 1969; Strehl and Winkler 1981). These numbers
demonstrate that Glomeropitcairnia exhibits the most structurally elaborate
trichomes, while some Guzmania and Tillandsia subgenus Tillandsia
produce the simplest appendages (Chapter 2). Stomata are restricted to
abaxial surfaces (except in Catopsis berteroniana) and occur along the intercostae. Simple, unspecialized stomata with guard cells located at about the
same level as the surrounding epidermal cells occur in Catopsis and
Glomeropitcairnia (Fig. 2.17A). Stomata with modified substomatal cells
(lobes extend from their polar ends) and sunken guard cells characterize
Guzmania, Tillandsia and Vriesea. Guard cells have supposedly lost their
mobility and foliar conductivity is now controlled by substomatal cells
(Downs 1974), but functional guard cells continue to serve Tillandsia usneoides (Martin and Peters 1984; Chapters 2 and 4). Each unspecialized epi-
Anatomy and morphology
563
dermal cell contains a prominent silica body as in the stem (Tomlinson
1969; Huber 1991; Fig. 4.23I).
The hypodermis is derived from the mesophyll, and is usually adaxially
differentiated into a peripheral mechanical region (sclerenchyma) and an
inner water-storage layer of colorless thin-walled cells (Tomlinson 1969;
Fig. 2.10). According to Saunders (1964, cited in Downs 1974), in
Tillandsia malzinei the entire mesophyll contains chloroplasts, whereas
Tillandsia anceps and Guzmania lingulata possess chlorenchyma embedded
within water-storage tissue. The adaxial hypodermis occupies much of the
leaf interior of some of the xerophytes. A typical palisade layer is absent
(Downs 1974; Tillandsia usneoides; Fig. 2.10A). Intercostal chlorenchyma
of the thinner-leafed forms sometimes contains large air lacunae
(Tomlinson 1969). Vascular bundles (Fig. 2.17A) are always embedded in
chlorenchyma, and their bulk relative to that of the rest of the leaf
decreases with increasing xeromorphism. Most Tillandsioideae lack extrafascicular strands; bands of sclerenchyma have been reported in Guzmania
and Vriesea just below the epidermis where they remain distinct from the
veins (Tomlinson 1969). The inner boundary of the bundle sheath is represented by a distinct ligno-suberized layer, independently surrounding and
thus separating the xylem from the phloem. Walls may be thickened (e.g.,
Catopsis, Guzmania, Tillandsia) to an extent exclusive to Tillandsioideae.
Vascular tissues are uniform throughout the family (Tomlinson 1969), and
consist of bundle sheath fibers, water-vascular tissue containing tracheids
and vessel elements (Cheadle 1955), and sieve tube elements with companion cells (Fig. 2.21). Smaller veins contain narrower tracheal elements,
especially among xeromorphic Tillandsia (Tomlinson 1969).
Flavonols (Arslanian et al. 1986), triterpenes and steroids (Atallah and
Nicholas 1971) characterize the leaves of Tillandsia purpurea and T. usneoides. The hypodermis contains p-coumaric acid and a ligninic substance
composed of p-oxy-benzyl residues (Hegnauer 1963), ferulic acid and sinapine acid (Hegnauer 1986). Flavonoids (aglycones, e.g., 6-hydroxykaempferol 3,6,7,49-tetramethyl ether, cirsilineol and jaceosidin from
Tillandsia utriculata), flavonols (e.g., gossypetin from Catopsis, patuletin
from Tillandsia and Vriesea, 6,39,59-trimethoxy-3,5,7,49-tetrahydroxyflavone and 6-hydroxy-myricetinmethylester from Tillandsia) and flavones
(e.g., apigenin, 6-hydroxy-luteolin, luteolin, scutellarein and 3,6,39,59tetramethoxy-5,7,49-trihydroxyflavon) have been isolated from leaves
(Ulubelen and Mabry 1982; Hegnauer 1986). Flavonoids have been
reported in leaf and stem exudates of Tillandsia usneoides (Wollenweber
1990; Wollenweber and Mann 1992) which suggest that chemotypes exist
564
Tillandsioideae
in this species. The putatively isolated position of Bromeliaceae within
Liliopsida accords with its flavonoid spectrum (Williams 1978; Chapter 9).
Little is known about Tillandsioideae as substrates for phytophagous
insects (Chapter 8). DeVries (1997) mentions some members as hosts for
Riodinidae butterflies: Guzmania and Werauhia for Napaea eucharila,
Werauhia for N. theages theages, and Werauhia for Hermathena candida.
According to Beutelspacher (1972), caterpillars of Caria domitianus domitianus feed on Tillandsia.
Inflorescences
Inflorescences are usually compound (up to several orders), more rarely
simple or even single-flowered (Gschneidner 1989; Rauh 1990; Fig. 3.3).
Pedicellate flowers are typical for panicles (e.g., Guzmania diffusa); branch
reduction results in racemes (e.g., Tillandsia ixioides). Sessile flowers are
common on compound spike-racemes (e.g., Tillandsia multiflora, Catopsis
spp.). Branch reduction in this type of inflorescence leads to simple spikes
(e.g., Tillandsia incurva) or strobils (e.g., Guzmania nicaraguensis).
Abbreviation of the main axis of the spike-raceme yields a digitate inflorescence (e.g., Tillandsia fasciculata) or a head (e.g., Tillandsia capitata,
Guzmania glomerata). Condensation of the lateral branches to head-panicles or head-racemes occurs in the subfamily (e.g., Glomeropitcairnia). A
special situation prevails in Tillandsia complanata and T. multicaulis where
these heads represent compound stipitate spikes that are perfoliated to simulate several lateral inflorescences. A compound inflorescence with manyflowered branches is considered ancestral in Tillandsia (Gschneidner 1989),
and probably for the whole subfamily.
Branching in compound inflorescences is axillary and the expanded
display often showy (e.g., several Guzmania and Vriesea species, Tillandsia
subgenus Anoplophytum in part; Napp-Zinn et al. 1978). Primary bracts
and lateral axes often bear an adossate prophyll and one to several basal
sterile bracts. Accessory shoots originating from the same primary bract as
in the pitcairnioid Cottendorfia florida occur in Racinaea commixa (Till,
unpublished). The subterminal flower is always much reduced and sterile.
Flowers are distichously (especially in Alcantarea, Racinaea, Tillandsia,
Vriesea and Werauhia) or spirally arranged (especially in Catopsis,
Glomeropitcairnia, Guzmania and Mezobromelia).
Anatomy and morphology
565
Flowers
Tillandsioid flowers are always trimerous, pentacyclic and heterochlamydeous, with contorted aestivation. Opening usually occurs acropetally along
an axis, and protandry is common (Melchior 1964). Dioecism is restricted
to one taxon (Catopsis subgenus Tridynandra). They can be pedicellate or
sessile, and symmetry is radial or rarely zygomorphic (e.g., Tillandsia argentea, T. funckiana, T. paraensis, Werauhia). Flowers are sometimes secund
(e.g., Alcantarea, Mezobromelia, Racinaea, Tillandsia secunda, Vriesea,
Werauhia; Fig. 3.3E). Diverse fragrances attract bats (Vogel 1969; Rauh
1990), butterflies, moths and other visitors (Till 1984, 1992b; Gardner
1986a; Rauh 1990; Chapter 6). Lures include triterpenes like citronellol,
geraniol and nerol (Hegnauer 1963). Many ornithophilous Tillandsia and
Vriesea species lack scents (Gardner 1986a; Arizmendi and Ornelas 1990).
Sepals overlap with the left margins, and are symmetric except for a few
taxa (e.g., Catopsis, Racinaea). Calyx members remain separate or become
variously connated. Most are greenish or pale, with brightly pigmented
organs, especially in Guzmania and Vriesea, being the most notable exceptions. Adaxial members are often keeled. Sepals rarely exceed the petals
(e.g., Guzmania musaica) and are membranaceous, especially toward the
margin; more rarely they are coriaceous and firm (e.g., Alcantarea, Vriesea
and Werauhia). Raphides occur in sepals more often than elsewhere in the
flower.
Petals are usually free or conglutinated into a short (Vriesea) or longer
(Guzmania, Mezobromelia) tube (Fig. 6.1A). They overlap with the right
margins, and are free or conglutinated. Most are concolorous (in the apical
part), rarely bicolored (predominantly in Vriesea). Shapes tend to be lingulate with no distinction between the claw and the blade. Blades can be quite
expanded (e.g., Tillandsia subgenus Phytarrhiza), the margins usually entire
to rarely crenulate (e.g., Vriesea heterandra). Two basal scales of diverse
sizes and shapes (Brown and Terry 1992) distinguish the corollas of
Alcantarea, Glomeropitcairnia, Mezobromelia, Tillandsia subgenus
Tillandsia, Vriesea and Werauhia from those of the rest of the subfamily
(Fig. 3.1B). Petal scales become visible just prior to the expansion of the
corolla (Brown and Terry 1992; Chapter 3). Folded cuticula sculptures
characterize Tillandsia hamaleana and Werauhia gladioliflora (Barthlott
and Ehler 1977). Raphide-containing idioblasts have been reported in the
petal scales of Werauhia tarmaensis (Rauh 1983b).
Stamens occur in two series (diplostemonous) of equal or unequal
566
Tillandsioideae
length, but are usually shorter than the corolla except for Tillandsia subgenus Tillandsia and Vriesea section Vriesea where they exceed the petals
(Fig. 6.1A,B). Filaments are flat or elliptic in cross-section, thin or succulent, erect or twisted and seldom plicated (e.g., Tillandsia subgenus
Anoplophytum; Fig. 6.1A–C), linear to triangular, free or very rarely
connate to a tube (e.g., Tillandsia monadelpha). Those of Guzmania and
Mezobromelia are agglutinated to the petals. The inner series of stamens in
Catopsis is connate with the petals for about half of the length of the filaments (e.g., Catopsis sessiliflora). The plication of the filaments in
Tillandsia subgenus Anoplophytum becomes visible during or soon after
anthesis (Evans and Brown 1989a). Anthers are usually elongated, stiff or
versatile, usually yellow, more rarely whitish, orange or blackish with the
attachment of the filaments basifixed or dorsifixed. The connective is
usually elongated into a short apical hump that in Werauhia is massive.
Pollen examined as acetolyzed or fresh material with the light microscope (Erdtman and Praglowski 1974; Wanderly 1984) or dried samples
examined with the scanning electron microscope (Ehler and Schill 1973;
Wanderly 1984) failed to reveal important features of the apertures. Fresh
pollen fixed in glutaraldehyde proved more informative (Halbritter 1988,
1992, 1995).
Tillandsioid pollen grains (Fig. 12.2) are 20–60 mm long and usually
sulcate (e.g., Catopsis), or exhibit a distal germination area (all other
genera, except Alcantarea where the aperture margin is solid). Several
Guzmania species produce inaperturate grains (Halbritter 1988, 1992).
Catopsis is distinguished from all the other tillandsioid genera by its entire
sulcus margin (Halbritter 1988, 1992), which resembles that of Hechtia and
Puya (Pitcairnioideae). Mature pollen grains are two-celled at release, containing a fusiform generative cell and a vegetative cell with a deeply lobed
nucleus. Raphides and crystals occur in some pollen grains (Kugler 1942;
Halbritter 1988).
Microsporogenesis has been described for Racinaea pallidoflavens (Hess
1991). None of the organelles de-differentiates during meiosis. Plastids are
amoeboid, exhibit complex internal structure, and gradually begin to accumulate polysaccharides from meiotic prophase I onward. These observations contradict reports (Vijayaraghavan and Bhatia 1985) for other taxa.
Mitochondria and dictyosome structure is typical, but the endoplasmic
reticulum (ER) is extensive and stains poorly using standard methods.
Ribosomes associate with the ER, or sometimes occur in dense clusters as
cytoplasmic polyribosomes (Hess 1991).
The gynoecium is superior except in Glomeropitcairnia where the pistil is
Anatomy and morphology
567
Figure 12.2. Pollen grains of selected Tillandsioideae (courtesy of Heidelmarie
Halritter). All scale bars510 mm. (A) Tillandsia straminea, distally and equatorially illustrating sulcus covered by operculum. (B) T. bryoides, distally illustrating
pronounced reticulum of subgenus Diaphoranthema. (C) T. fasciculata, distally
illustrating the diffuse sulcus with irregularly ruptured exine characteristic of subgenus Tillandsia. (D) Vriesea bituminosa (section Xiphion), distally illustrating
sulcus covered by solitary exine elements. (E) Guzmania monostachia, inaperturate
pollen. (F) Catopsis sessiliflora, distally illustrating simple furrow and sharply cut
aperture margins.
568
Tillandsioideae
about half inferior if its ovule-bearing region is considered basal. Were the
septal nectaries included, all tillandsioid gynoecia would be partly inferior
(Fig. 3.1A; Cecchi Fiordi and Palandri 1982; Böhme 1988; Ueno 1989).
Septal nectaries lead into a horizontal channel at the inner base of the perianth (Böhme 1988; Fig. 3.1A). Nectar channels of Catopsis arise directly
from above the middle of the septal nectary, while in Guzmania,
Mezobromelia, Tillandsia and Vriesea they originate near the top of this
glandular tissue. Copious sucrose-rich nectar (Bernardello et al. 1991) is
produced by most tillandsioids.
Ovules are attached in several rows along the entire length of the ovary
cavity (Fig. 3.1A), or only in the basal half (Goldberg 1989). Ovules are
bitegmic, crassinucellar and anatropous, and contain an embryo sac with
three small antipodial cells. Endosperm is helobial (Billings 1904;
Schürhoff 1926; Johri et al. 1992), at first free nuclear and later cellular
(Goldberg 1989). The embryo is lateral to the endosperm or rarely embedded within it (Fig. 3.7). According to Martin (1946), the tillandsioid
embryo belongs to the ‘Linear group’. The endosperm is copious, but
reduced in Tillandsia usneoides (Martin 1946), and starchy (Huber 1991).
Polyembryony has been observed in Tillandsia subgenus Diaphoranthema
(Subils 1973; Fig. 3.6K) and subgenus Tillandsia (Suessenguth 1921).
At anthesis the outer integument is shorter than the inner one, but it
elongates after anthesis to form the typical tillandsioid seed appendage
(coma) as pseudohairs develop by longitudinal splitting of the outer and
the central tissue layer of the outer integument (Figs. 3.6J, 3.7). A chalazal
appendage produced from the funicle is also present in many genera (Gross
1988a). Contrary to the above, in Catopsis multicellular strands grow from
individual epidermal projections of the chalaza to form a folded coma
(Gross 1988a; Palací 1997). Glomeropitcairnia seeds possess a pappiform
coma at both ends (Smith and Downs 1977). Comas vary from pure white
(most Tillandsia species) to ochraceous and brown (many Vriesea and
Guzmania species).
The asymplicate zone of the gynoecium forms the style and stigma, while
the septal nectaries are formed by the symplicate zone. Styles are elongated
in most cases, and vary from shorter to longer than the anthers, and when
reduced remain short (e.g., Tillandsia subgenus Diaphoranthema). The
three carpels are fully connate or rarely free in the apical region (at the transition into the stigma lobes). Stigma morphology (Figs. 3.1C, 12.1) is
diverse within Tillandsioideae and all of the recognized types – conduplicate-spiral, convolute-blade, coralliform, cupulate and simple-erect (Brown
and Gilmartin 1984, 1988, 1989b; Schill et al. 1988; Gortan 1991; Fig. 3.1C)
Phytogeography and evolution
569
– are represented. Stigma lobe margins are usually papillate (e.g., ‘low to
medium papillae in wet stigmas’ in Vriesea; Heslop-Harrison and Shivanna
1977), Glomeropitcairnia included (Till et al. 1997). Werauhia with cupulate
stigmas lacks stigma papillae.
Tillandsioid capsules are septicidal and of diverse shapes and sizes.
Those of Guzmania, Mezobromelia, Racinaea and Tillandsia are usually
more cylindric compared with the relatively conical fruits of Alcantarea,
Vriesea and Werauhia and the ovoid Catopsis capsule. Dehiscence is apical
in the semi-inferior ovaries of Glomeropitcairnia (Smith and Downs 1977).
The pericarp is uniform (e.g., several Vriesea and Werauhia spp.) or divided
into a stramineous exocarp and a dark castaneous, smooth and lustrous
endocarp (e.g., Tillandsia). Fruits require several weeks to a year to mature.
Phytogeography and evolution
Tillandsioideae range more widely than either of the other two bromeliad
subfamilies. Tillandsia pedicellata extends to 44° latitude in central
Argentina (Smith 1934a; Till 1984), and Tillandsia usneoides occurs northward to latitude 37° in the eastern United States (Garth 1964). Distribution
maps (Smith and Downs 1977) indicate that the centers of greatest diversity lie in the northern Andes and the Antilles, with several secondary
centers defined by subgenera of Tillandsia in Mexico and South America
(Chapter 9). Glomeropitcairnia is restricted to the Lesser Antilles and
northeasternmost Venezuela, while Mezobromelia extends from the northern Andes to the Guayanas and the Greater Antilles. All of the taxa considered that have been cited as ancestral (e.g., Glomeropitcairnia, Catopsis,
Tillandsia subgenera Allardtia and Pseudalcantarea; Ranker et al. 1990;
Winkler 1990; Beaman and Judd 1996; Terry et al. 1997a) occur in the
Antilles, which represent the remnants of the most recent land bridge
between the two American subcontinents. Secondary centers of species
richness are located in Central America (e.g., Werauhia) and southeastern
Brazil (e.g., Alcantarea, Tillandsia subgenus Anoplophytum, part of
Vriesea). The joining of the two American subcontinents to produce a
Middle American land bridge during the Pliocene probably encouraged
speciation, as did immigrations during Pleistocene interglacials (Smith
1962). The massive radiation of Tillandsioideae in northern Peru to
Colombia probably began or was accelerated by the uplift of the Andes
during the Pliocene and more recent times (Gentry 1982). Alternating episodes of warmer and wetter and colder and drier climate in this region
shifted the elevations of life zones (Lauer 1986), prompting speciation,
570
Tillandsioideae
particularly in montane taxa such as Guzmania and Puya (Pitcairnioideae;
Fig. 9.2; Chapter 9). Amazonian refuges (Prance 1973, 1982) primarily
affected lowland flora and probably had less impact on Bromeliaceae,
including Tillandsioideae, which in South America is most diverse at higher
elevations. The geologically ancient Guayanan highlands, while the home
of many primitive pitcairnioid lineages, is lightly populated with
Tillandsioideae, and its influence on evolution in this subfamily remains
little understood (Chapter 9).
Contrary to Pittendrigh (1948) who postulated evolution of mesophytes
from xerophytic ancestors, more recent authors see the same progression
headed in the opposite direction (e.g., Benzing and Renfrow 1971b,c;
Benzing 1980; Benzing et al. 1985; Adams and Martin 1986c; Medina 1990;
Winkler 1990; Chapter 9). Read this way, the tillandsioid precursor was
mesophytic, possessed absorbing roots, broad, thin foliage, moderate-sized
leaf impoundments and foliar trichomes with narrow shields.
Inflorescences were probably compound and spirostichous throughout.
Flowers were relatively unspecialized and equipped with a polypetalous
perianth and a superior ovary. Derived lines are progressively heterochronic
and xeromorphic (Benzing and Renfrow 1971b,c; Fig. 2.1); Pittendrigh
(1948) considered these same traits plesiomorphic. Very likely none of the
extant tillandsioids is ancestral, and extant Tillandsioideae represent intermediate or end points in a massive radiation characterized by much mosaic
evolution.
Guzmania is entirely mesic, but its flowers with conglutinated petals,
agglutinated filaments and tendencies to autogamy appear to be substantially derived. Catopsis is distinguished from the rest of Tillandsioideae by
foliar trichomes with cells arranged in the sequence 418132, unspecialized stomata that may also occur on the adaxial leaf surface (e.g., Catopsis
berteroniana), sometimes imperfect flowers, or an entire sulcus margin in
pollen grains (Halbritter 1988, 1992), a nectar channel that arises directly
from above the middle of the septal nectary (Böhme 1988) and a folded
seed coma comprised of unicellular hairs of chalazal origin (Gross 1988a;
Palací 1997). Harms (1930) was sufficiently impressed by these characters
to recognize Catopsis as tribe Catopsideae. However, Terry and Brown
(1991) and Terry et al. (1997b) discovered that all of the tillandsioids except
Glomeropitcairnia share a common set of chloroplast DNA restriction
sites, a finding consistent with Ranker et al.’s (1990) belief that
Glomeropitcairnia lies outside core Tillandsioideae. A more recent study
using the plastid locus ndhF (Terry et al. 1997b; Chapter 9) places
Glomeropitcairnia within Tillandsioideae with the notion that it quickly
Phytogeography and evolution
571
diverged from the rest of the subfamily. Vriesea possesses petal scales whose
development is terminal during ontogeny (Brown and Terry 1992; Chapter
3). Although most of this genus is mesic, flower morphology suggests relatively advanced status. Tillandsia exhibits the least specialized flowers, but
its Type Five members possess exceptionally derived vegetative structure
and function. The mesophytic phytotelm types probably more closely parallel the subfamily ancestors in overall character (Chapters 4 and 9).
Brown and Gilmartin (1986, 1989a), Brown and Palací (1997) and Till
(1984) reported a nearly consistent basic chromosome number of x525 for
Tillandsioideae. Such uniformity offers little insight on phylogeny save for
the polyploid nature of Tillandsia subgenus Diaphoranthema, a clade also
marked by pronounced neoteny and extreme xerophytism (Till 1992b;
Chapter 9).
Cladistic analyses (Gilmartin 1983; Gilmartin and Brown 1987;
Gilmartin et al. 1989; Ranker et al. 1990) have been conducted for several
taxa, but with only partially satisfactory results owing to insufficient data.
Glomeropitcairnia consistently occupied a position well removed from the
rest of the subfamily in contrast to the results of Terry et al. (1997a,b), and
xerophytism almost certainly evolved several times within the
Tillandsia/Vriesea complex (Chapter 9). Gilmartin et al.’s (1989) trees place
Tillandsia and Vriesea in a basal position within Tillandsioideae and
support the opinion of Benzing (1980). Tillandsioideae appears to be
monophyletic (Ranker et al. 1990) having perhaps originated from some
pitcairnioid-like stock (Gilmartin and Brown 1987); however, Ranker et al.
(1990) state that ‘Pitcairnioideae are not basal in the family’, a view supported by Terry et al. (1997a,b).
13
Tillandsia and Racinaea
W. T I L L
Spencer and Smith’s (1993) recognition of genus Racinaea (formerly subgenus Pseudocatopsis of Tillandsia) reflects growing appreciation that
Tillandsia sensu Smith and Downs (1977), along with Vriesea, constitute a
large complex of closely related species needing major taxonomic reorganization. This chapter deals with Racinaea and the remaining six subgenera
of Tillandsia, many of which are likely to be redefined along with similarly
paraphyletic Vriesea.
Racinaea comprises 56 mainly epiphytic species; Tillandsia includes
about 550 species of terrestrial, epiphytic or lithophytic herbs of highly variable architecture ranging from phytotelm forms more than 1 m in diameter (e.g., T. grandis) to dwarf, moss-like epiphytes (e.g., T. bryoides) of
c. 3 cm height (Fig. 2.1). Mesophytic taxa are usually rosulate, or possess
more elongate stems if saxicoles (e.g., T. australis). Type Five species (the
atmospherics) are more often leafy caulescent (e.g., T. cauligera), and lack
substantial interfoliar impoundments (Fig. 2.4). Phyllotaxis is spiral or
rarely distichous (e.g., T. capillaris), and the leaves are lingulate (e.g., T. fendleri) to narrowly triangular (e.g., T. fasciculata) or linear (e.g., T. setacea),
green or densely cinereously lepidote with centrally symmetric scales.
Blades are flat and thin (e.g., R. seemannii) or succulent (e.g., T. aizoides).
Scapes tend to be distinct and equipped with foliaceous bracts that may
decrease in size and shape toward the top of the scape (e.g., T. polystachia),
or abruptly change to vaginiform bracts (e.g., T. fuchsii).
Inflorescences are usually compounded to form a panicle (e.g., T.
marnier-lapostollei), a raceme (e.g., T. ixioides), a spike-raceme of distichous (e.g., T. clavigera) or polystichous spikes (e.g., T. spiraliflora), a digitate inflorescence (e.g., T. carlsoniae), a head (e.g., T. capitata), a simple
distichous (e.g., T. xiphioides) or a simple polystichous spike (e.g., T. stricta)
or rarely a single flower (e.g., T. albertiana; Fig. 3.3L). The inflorescence of
573
574
Tillandsia and Racinaea
T. complanata and T. multicaulis is perfoliated and apparently multiple
from the axils of several leaves. Adossate prophylls may be absent.
Offshoots sometimes develop on the inflorescences (e.g., T. aizoides, T.
denudata var. vivipara, T. flexuosa, T. latifolia, T. mima var. chiletensis, T.
paucifolia subsp. schubertii, T. propagulifera, T. pyramidata, T. secunda var.
vivipara, T. somnians, T. utriculata subsp. utriculata; Fig. 2.11A). Floral
bracts are usually conspicuous, rarely minute (e.g., R. tetrantha var. tetrantha). Flowers tend to be short pedicellate, more rarely sessile, bisexual,
usually odorless, or more rarely strongly fragrant. Raphide sacs occur in all
the floral parts. Sepals are convolute, symmetric or nearly so in Tillandsia,
but asymmetric in Racinaea, all free or equally joined, or just the adaxial
pair highly connate. Petals are lingulate to spathulate, free, usually without
basal appendages except for a group of xeric species formerly included in
Vriesea section Vriesea (Grant 1993b, 1994b), usually uniformly violet,
blue, yellow, white, green or red distally. Petal blades can be two-colored
(e.g., T. cacticola, T. punctulata, T. purpurea, T. tectorum, and some of those
xeric species previously assigned to Vriesea section Vriesea; Fig. 6.1B).
Stamens are arranged in two series of equal or unequal lengths and free
from the petals and from each other except where rarely connate into a filament tube (e.g., T. monadelpha, T. narthecioides). Anthers are included in
or exserted from the corolla. Filaments are usually straight, rarely plicated
(e.g., subgenera Allardtia and Anoplophytum in part; Fig. 6.1C) or twisted
(e.g., some species of subgenus Tillandsia), flat to somewhat succulent (e.g.,
Racinaea) and linear to narrowly triangular. Anthers are elongated to subglobose, yellow, orange or blackish, versatile, dorsifixed or basifixed. Pollen
is usually yellow to whitish, but orange in subgenera Diaphoranthema,
Phytarrhiza and Racinaea. Exines are reticulate to foveolate and the aperture diffuse and of the island-type, Vriesea imperialis-type or operculumtype (Halbritter 1988, 1992). Ovaries are superior except for the septal
nectaries, and ovoid to conical. Styles are usually elongated, rarely strongly
abbreviated (e.g., Tillandsia subgenus Diaphoranthema, Racinaea), usually
colored like the ovary or the filaments and included in or exserted from the
corolla. Stigma lobes are conduplicate-spiral or simple-erect in subgenus
Phytarrhiza. Coralliform lobes have been reported (Brown and Gilmartin
1989b; Figs. 3.1C, 12.1). However, it should be stressed that the kind of
simple-erect stigma in subgenus Allardtia differs from that in subgenus
Diaphoranthema, which more closely resembles a reduction of the coralliform type characteristic of T. narthecioides. Ovules are numerous and
usually caudate. Fruits are septicidal capsules usually divided into a stramineous exocarp and a castaneous endocarp and longer in the epiphytic
Evolution
575
compared with the epilithic species. Seeds are fusiform, the plumose,
usually white coma is developed at the micropylar end and is straight, the
stick-hairs often breaking off at the exostom to form a second ‘parachute’
(Gross 1988a; Fig. 3.6J). The chalaza is usually elongated to a tongue-like
projection (except for Racinaea, mesic members of subgenus Phytarrhiza,
and some members of subgenus Anoplophytum), but is not further developed during seed maturation.
Evolution
Schimper (1888) Mez (1896) and Smith (1934a), to mention only a few
authorities, considered the mesic tillandsias (including Racinaea) ancestral
to the more xerophytic types. However, Pittendrigh (1948) cited ecological
traits as evidence that evolution progressed in the opposite direction, i.e.,
that Tillandsioideae or perhaps Bromeliaceae as a whole had a dry-land,
terrestrial ancestry. Recent ecophysiological studies (Benzing and Renfrow
1971b,c; Benzing 1978a; Benzing et al. 1978; Benzing and Ott 1981; Adams
and Martin 1986b,c; Winkler 1986; Medina 1990, Ranker et al. 1990;
Chapter 9) support the first view. Mesomorphy pervades Tillandsia subgenera Allardtia, Phytarrhiza, Pseudalcantarea and Tillandsia, and genus
Racinaea. Vegetative architecture suggests that heterochrony played a
major role during the emergence of drought-tolerance in subgenera
Anoplophytum, Diaphoranthema and Phytarrhiza.
Studies of stigma form and development provide additional insights on
evolution in Tillandsia (Brown and Gilmartin 1988, 1989b; Schill et al.
1988; Gortan 1991). Mesophytic Phytarrhiza exhibit highly specialized
coralliform stigmas in most cases, and Racinaea contains several taxa with
simple-erect organs that further indicate derived status. Moreover,
members of Racinaea possess floral characteristics much too distinct to be
basic for genus Tillandsia. The remaining three subgenera, Allardtia,
Pseudalcantarea and Tillandsia, appear to be relatively closely related. Only
Pseudalcantarea is exclusively mesophytic, and its flowers are equipped
with simple-erect to conduplicate-spiral stigmas (Beaman and Judd 1996).
Also noteworthy are its flaccid and drooping petals that attract nocturnal
pollinators.
The conduplicate-spiral stigma (Fig. 3.1C) occurs in all three subfamilies, and predominates in subgenera Allardtia and Tillandsia, a distribution
that prompted Brown and Gilmartin (1988) to consider this morphology
basic to all the others. Additionally, this stigma type seems to have evolved
repeatedly in the family, perhaps to accommodate bird pollination.
576
Tillandsia and Racinaea
Subgenus Tillandsia is predominantly semi- to fully xerophytic. Flowers
exhibit pronounced adaptation for birds; stigmas are almost exclusively
conduplicate-spiral. Members of Allardtia are mostly mesophytic, and
their similarly unspecialized flowers can remain largely closed apparently
to promote self-pollination. Stigmas are mainly conduplicate-spiral, but
the simple-erect type occurs in at least one-third of the membership.
Vegetative and floral morphology point to a single prototype for all three
subgenera (Allardtia, Pseudalcantarea and Tillandsia) with mesic, but not
necessarily phytotelm, foliage and unspecialized allogamous flowers. Its
distribution was probably Andean. An antecedent of this description
would most closely conform to subgenus Allardtia, but almost certainly the
current concepts (circumscriptions) of several Tillandsia subgenera, including Allardtia, are inaccurate.
No fossils can be unequivocally assigned to Tillandsia or even to
Tillandsioideae, and too little is known about the paleoclimatology and
forest refuges of tropical America to draw conclusions about effects on bromeliad evolution (Chapter 9). However, Graham (1997) mentions three
paleophysiographic provinces which coincide with taxa of Tillandsioideae
or even of Tillandsia: central Mexico through northern Central America
with Tillandsia subgenus Tillandsia, southern Central America with
Werauhia, and northern South America with Tillandsia subgenus Allardtia,
Mezobromelia and the xeric members of Vriesea section Vriesea that Grant
(1993b) reassigned to Tillandsia subgenus Tillandsia.
Winkler (1986) turned to the foliar epidermis to explain the evolution of
Tillandsia. Essential to his scheme was a presumed progressive decrease in
the ratio of stomata to trichomes and paleogeographic data from Weyl
(1964; Chapter 2). Winkler considered subgenus Allardtia the most primitive clade within Tillandsia. More recently (Winkler 1990) he substituted
subgenus Pseudalcantarea as the basic taxon (a view shared in part by
Beaman and Judd 1996), although reasons for Winkler’s rejection of subgenus Allardtia were simply the disjunct distribution in Central America
and the Antilles and the pronounced positive ratio of stomata to trichomes
that also occurs in subgenus Tillandsia. He drew the following conclusions:
‘In the grey species with narrow leaves, radiating evolution took place in
Central America and in the southern Andean parts of South America. The
species with broad green foliage show the strongest speciation in Ecuador,
Colombia and Peru. A special center of highest species diversity is
Ecuador. Evolution of species of the genus Tillandsia took place with
ancestors from the Andean region probably at the beginning of the
Evolution
577
Tertiary. In the outer Andean South America region, evolution is mainly
influenced by refugia of forests during the Pleistocene, whereas in Central
America and in the Caribbean region continental island formation since
the early Tertiary is of overriding importance’. It must be emphasized,
however, that epidermal characteristics even when combined with his
paleogeographic interpretations seem inadequate to reconstruct the evolution of a genus as complex as Tillandsia.
Cytological data discussed in Chapter 9 indicate a generic base number
of n525. A few dysploids exist (Brown and Gilmartin 1989a), for example
T. complanata from Costa Rica with n522, T. leiboldiana from Mexico with
n519, T. scaligera from Ecuador with n52512210 fragments, and T.
polystachia from Colombia with n5251B-chromosomes. Counts are still
too scarce to justify phylogenetic interpretations. Polyploidy appears to be
extensive in subgenus Diaphoranthema (Till 1984), and perhaps helps
explain the pronounced heterochrony and the strong tendencies for autogamy and cleistogamy (e.g., T. angulosa, T. castellanii, T. erecta and T.
retorta) through this assemblage (Till 1992b).
Autogamy, cleistogamy and polyploidy characterize many founder populations and island floras. Autogamous, polyploid species of subgenus
Diaphoranthema behave like founders in certain arid regions characterized
by scattered suitable habitat (Till 1992b), and scarce pollinators. However,
cleistogamic species also occur in subgenus Allardtia unaccompanied by a
single demonstrated case of polyploidy (e.g., T. huarazensis, T. selleana, T.
walteri).
Little is known about the breeding systems and genetic structures of
Tillandsia populations except for the allozymic comparison (Soltis et al.
1987; Chapter 6) of allogamous T. ionantha (subgenus Tillandsia) and
autogamous T. recurvata (subgenus Diaphoranthema). Predicted patterns
prevailed: fewer alleles overall and more individual heterozygosity in the
outcrosser and more alleles per locus, but less variation, among near neighbors in T. recurvata. Benzing (1978a) linked the incidence of autogamy and
high seed set with extreme epiphytism. Till’s (1984, 1992b) results, which
demonstrated frequent autogamy and polyploidy in subgenus
Diaphoranthema and the success of many of its members in colonizing
extreme habitats, accord with his proposition.
Clearly relationships within Tillandsia remain obscure, and very likely
closely related Tillandsia and Vriesea are paraphyletic. Recent revisions are
available for subgenera Phytarrhiza (Gilmartin and Brown 1986),
Diaphoranthema (Till 1984, 1989a,b. 1991, 1992a), Tillandsia (Gardner
578
Tillandsia and Racinaea
1982, 1986b) and Pseudalcantarea (Beaman and Judd 1996) and for
Racinaea (Spencer and Smith 1993), but not for subgenera Allardtia and
Anoplophytum. Vriesea has been partly revised by Grant (1995a,b), and its
xeric members of section Vriesea transferred to Tillandsia subgenus
Tillandsia (Grant 1993b, 1994b).
Subgeneric treatments of Tillandsia
Tillandsia is currently divided into six subgenera (Smith and Downs 1977)
and the recently segregated Racinaea (the former subgenus Pseudocatopsis
of Tillandsia; Spencer and Smith 1993). Species nomenclature follows
Grant (1993b, 1994b), Kiff (1991) and Spencer and Smith (1993).
Subgenus Allardtia (,200 species)
Phyllotaxis in this group is spiral except for distichous T. albertiana, and
flowers are usually odorless, but intensively fragrant in T. diaguitensis, T.
xiphioides and T. yuncharaensis. Sepals tend to be symmetric, or rarely
asymmetric, and ovate or lanceolate, free or connate, and the adaxial
members usually carinated. Petals normally exhibit hues of lilac or violet,
but rarely they are white, crimson, yellow or green. Blades are usually distinct yet form a tubular corolla. Petal tips typically spread, and the corolla
throat is open in allogamous forms, or rarely the petal tips are cucullate and
incurved and the corolla throat is then closed in supposed autogamous
forms (Fig. 3.3). Stamens are always included within the corolla, equaling
the petals or slightly shorter; the anthers are yellow or cream, the pollen
grains heterogeneous, 30–45 mm long, ellipsoidic and equipped with diffuse
apertures such as those of the island-type or Vriesea imperialis-type. Exines
are reticulate or foveolate (Halbritter 1988; Fig. 12.2). Filaments are
usually straight, but plicated in T. cardenasii, T. cauligera, T. churinensis, T.
cochabambae, T. latifolia, T. muhrii, T. pseudocardenasii, T. pseudomacbrideana, T. pseudomicans, T. tectorum, T. truxillana and T. zecheri (Fig. 6.1C).
Styles are slender, much longer than the ovary, and included within the
corolla except for T. secunda (Gilmartin 1972), which might be misplaced
here. Stigma lobes are conduplicate-spiral or simple-erect (Schill et al. 1988;
Brown and Gilmartin 1989b; Gortan 1991; Fig. 12.1). Ovules are usually
appendaged at the chalaza, the resulting seeds usually conforming to the
‘wagneriana’ and ‘incarnata’ types, or less often to the ‘juncea’, ‘utriculata’,
‘funckiana’ or ‘cotagaitensis’ types (Gross 1988a,b).
Subgeneric treatments of Tillandsia
579
Geographic distribution. Mainly Andean and Mesoamerican, Greater
Antilles, and southeastern Venezuela.
The transfers of T. duidae to Vriesea, of T. undulatobracteata to Guzmania,
and of T. hutchisonii to Mezobromelia demonstrate that many species are
imperfectly known, and without doubt additional taxa will be reassigned
to other subgenera or even genera. The distinction between subgenera
Allardtia and Anoplophytum is weak, and their separation may not be justified, at least not as proposed by Smith and Downs (1977). The Andean
group of Anoplophytum (as classified in Smith and Downs 1977) is here
included in subgenus Allardtia (e.g., T. friesii, T. lorentziana, and T. xiphioides alliances).
Subgenus Anoplophytum (,60 species)
Phyllotaxis is spiral and flowers are odorless. Sepals are symmetric or
nearly so, free or connate and the adaxial members usually carinate. Petals
are erect and form a tubular corolla that is most often blue, rose or white,
rarely yellow or green. Blades are usually distinct with spreading tips. Petal
blades are enlarged in T. sucrei. Stamens are included within the corolla,
about equaling the petal claw; the anthers are linear, yellow or cream.
Pollen grains are 25–45 mm long, subglobose and equipped with apertures
of the operculum-type or island-type, but intermediate conditions are
common (Fig. 12.2). Less often the apertures are diffuse and in T. geminiflora belong to the Vriesea imperialis-type. Exines are reticulate to foveolate
or rarely nearly smooth (Halbritter 1988). Filaments tend to be plicate, but
straight in T. candida, T. eltoniana and T. ixioides. Styles are slender and
longer than the ovary and more or less included within the corolla. The
stigmas are simple-erect (Schill et al. 1988; Brown and Gilmartin 1989b;
Gortan 1991; Figs. 3.1C, 12.1). Ovules are obtuse or short appendaged at
the chalaza. Seeds belong to the ‘cotagaitensis’ type (Gross 1988a).
Geographic distribution. Eastern and southern Brazil, T. gardneri and T.
tenuifolia extending into northern South America and the Antilles.
Tillandsia pohliana reaches Peru, while T. ixioides, T. jucunda and T.
tenuifolia extend into Bolivia, Argentina and Uruguay.
Anoplophytum in Smith and Downs (1977) comprises two morphological
groups. The Andean group (T. arequitae, T. argentina, T. bagua-grandensis,
T. bermejoensis, T. buchlohii, T. camargoensis, T. caulescens, T. chiletensis,
580
Tillandsia and Racinaea
T. colganii, T. comarapaensis, T. diaguitensis, T. didisticha, T. dorotheae, T.
friesii, T. geissei, T. genseri, T. guelzii (including T. pucaraensis), T. hasei, T.
koehresiana, T. lorentziana, T. lotteae, T. muhriae (including T. alberi and T.
guasamayensis), T. oropezana, T. pfeufferi, T. ramellae, T. vernicosa, T.
walter-richteri, T. xiphioides and T. yuncharaensis) consists of strongly xeromorphic species that almost always possess dense, distichously flowered
spikes. Corollas are usually white or less often pale violet or blue-violet,
rarely rose. Only T. lotteae and T. xiphioides var. lutea have yellow-green or
yellow petals respectively. This group is transferred to subgenus Allardtia in
the present treatment.
Anoplophytum is here restricted to the Brazilian group (the second one),
which contains T. aeranthos, T. araujei, T. bergeri, T. brachyphylla, T. burlemarxii, T. candida, T. carminea, T. chapeuensis, T. eltoniana, T. gardneri, T.
geminiflora, T. globosa, T. grazielae, T. heubergeri, T. horstii, T. ixioides, T.
jucunda, T. kautskyi, T. leonamiana, T. milagrensis, T. montana, T. neglecta,
T. nuptialis, T. organensis, T. pohliana, T. polzii, T. pseudomontana, T. reclinata, T. recurvifolia, T. roseiflora, T. seideliana, T. sprengeliana, T. stricta, T.
sucrei, T. tenuifolia, T. thiekenii and T. toropiensis. This assemblage contains
both pronounced xeromorphic and rather mesomorphic species.
Inflorescences are compounded of distichous spikes, or are polystichously
flowered, and dark rose or blue petals prevail. White petals are less frequent
(e.g., T. araujei) as are yellow (e.g., T. ixioides) and green corollas (e.g., T.
jucunda, depending on the variety). Tillandsia esseriana and T. linearis are
assigned to subgenus Phytarrhiza.
The length of the stamens relative to the petal claw and the plication of
the filaments have been used to separate subgenera Allardtia and
Anoplophytum (Smith and Downs 1977). Filament plication, however,
occurs late in ontogeny (Evans and Brown 1989a), and may be inappropriate for distinguishing subgenera. In the cases of T. candida vs. T. tenuifolia,
and T. chiletensis vs. T. lorentziana, this single characteristic would assign
members of each pair to different subgenera despite the obvious close relationships. Quite likely subgenera Allardtia and Anoplophytum constitute a
clade (except for several misplaced species), and Anoplophytum is the
morphologically more specialized of the two groups.
Subgenus Phytarrhiza (37 species – 19 mesophytic, 18 xerophytic)
Phyllotaxis is spiral or rarely distichous in some xerophytic species and
flowers are odorless or fragrant. Sepals are symmetric or nearly so, free or
shallowly connate, the adaxial ones usually ecarinate or only slightly carinate; more rarely they are distinctly carinate. Petal blades are broad, con-
Subgeneric treatments of Tillandsia
581
spicuous and form a flat ‘disc’, and only the claws form a tube. Petal color
is usually blue or white in the mesophytic species, but yellowish in T. triglochinoides and occasionally T. monadelpha. Blue prevails in the xerophytic taxa, the exceptions being white in T. peiranoi and T. streptocarpa,
yellow in T. aurea, T. crocata, occasional T. duratii and T. streptocarpa,
brown with yellow in T. humilis, or cream with purple tips in T. cacticola,
T. purpurea and T. straminea. Stamens are shorter than the petal claw,
equaling to exceeding the pistil; filaments are straight and usually free, but
half connate in T. monadelpha. Anthers are orange at least in the xeromorphic species, and contain rather uniform, subglobose, about 20 mm-long
pollen grains. Apertures are usually rather wide and of the operculum-type,
although transitions occur to diffuse sulci and the island-type (Halbritter
1988; Fig. 12.2). Exines are reticulate. Styles are short and stout and deeply
included within the corolla. Stigmas are conduplicate-spiral in xerophytic
or coralliform in mesophytic species and in xeric T. humilis, or simple-erect
in T. duratii and T. reichenbachii (Schill et al. 1988; Brown and Gilmartin
1989b; Gortan 1991; Fig. 3.1). Ovules are obtuse and slender in mesic
members vs. short appendaged at the chalaza and of ovoid shape in the
xeric species. Seeds belong to the ‘narthecioides’ and ‘wagneriana’ types in
mesic members vs. to the ‘mauryana’, ‘incarnata’, ‘cotagaitensis’ and ‘bryoides’ types in the xeric species (Gross 1988a).
Geographic distribution. A group of mesophytic taxa occurs in central
Andean to northern South American ranges with a few species extending
into Guatemala and Belize. The other group, largely a xerophytic
assemblage, extends from the southern Andes to northeastern and
southern Brazil.
Subgenus Phytarrhiza is clearly distinct from the first two subgenera, but
resembles subgenus Diaphoranthema particularly by floral characteristics.
Distinctions between the mesic and xeric species of Phytarrhiza exceed
those between xeric Phytarrhiza and Diaphoranthema. Gilmartin and
Brown (1986) suggested that Phytarrhiza as currently defined is paraphyletic. Tillandsia esseriana and T. linearis, formerly assigned to subgenus
Anoplophytum (Smith and Downs 1977), are better placed here.
Subgenus Diaphoranthema (,30 species)
Phyllotaxis is spiral or distichous and flowers are odorless or fragrant.
Sepals are symmetric, free, or adaxially connate and more or less carinate.
Petals are lingulate, the claws forming a tubular corolla. Blades are usually
582
Tillandsia and Racinaea
narrow and inconspicuous with tips that curve or roll outward leaving the
corolla throat open. Sometimes the petal tips are cucullate and the corolla
throat is completely closed (e.g., T. retorta). Petal color is usually yellow to
brownish, occasionally dark brown-violet to dark coffee-brown, or rarely
violet. That of T. usneoides is typically green. Stamens are shorter than the
petal claw, deeply included within the corolla and equal to slightly exceeding the style; filaments are straight and free. Anthers are linear and orange,
the pollen grains within uniform, subglobose, and 15–20 mm long and
equipped with narrow apertures that vary between the diffuse sulcus and
the island-type (Halbritter 1988). Exines are pronounced reticulate with
free columellae and copious pollenkitt. Styles are short, stout and bear
simple-erect stigmas (Schill et al. 1988; Brown and Gilmartin 1989b;
Gortan 1991). The tips of the lobes of the ‘simple-erect’ stigmas of this subgenus are often emarginate. Stigma form in Diaphoranthema seems to be
reduced from the coralliform condition. Ovules are short appendaged at
the chalaza to obtuse. Seeds belong to the ‘cotagaitensis’ and ‘bryoides’
types (Gross 1988a).
Geographic distribution. Mainly south Andean extending to northeastern
Brazil and Uruguay. Two wide-ranging species, T. recurvata and T.
usneoides, range through Mesoamerica and the Antilles into the southern
United States.
Subgenus Diaphoranthema may be monophyletic (Gilmartin and Brown
1986), although it differs from subgenus Phytarrhiza primarily by generally
reduced habits and frequent distichous phyllotaxis. The boundary between
these two taxa is as weak as that between subgenera Allardtia and
Anoplophytum. In fact, Diaphoranthema exhibits evidence of neotenic derivation from Phytarrhiza-like stock. Moreover, mesophytic and xerophytic
Phytarrhiza may constitute natural groups (e.g., the stigma, ovule and seed
types differ). If so, the second of the two should probably be united with
subgenus Diaphoranthema.
Subgenus Tillandsia (,200 species)
Phyllotaxis is spiral, with T. pentasticha exhibiting just five orthostiches.
Flowers are odorless, their sepals symmetric, free to adaxially connate, and
usually adaxially carinate. Petals are naked, except in the xeric species formerly assigned to Vriesea section Vriesea (Grant 1993b, 1994b) where two
basal appendages occur. Tubular actinomorphic corollas prevail with only
Subgeneric treatments of Tillandsia
583
the tips of the petals curved outward if at all (yet sometimes enough to
produce zygomorphy; Fig. 6.1A). Color is usually violet or lavender, rarely
green, yellow, white, rose or red. Petals are rarely constricted at the height
of the style base (e.g., T. fuchsii). Stamens in two series of equal or unequal
lengths surpass the corolla; filaments are straight or spirally twisted, but
never plicated, flat and widest near the base or slightly succulent and widest
near the top. Anthers are linear to ellipsoidic and yellow to dark brown.
Pollen grains are yellow, rarely cream and uniformly about 1.5–2.0 times as
long (45–70 mm) as wide. Apertures are diffuse and occasionally exhibit
transitions toward the island-type (Halbritter 1988). Exines are reticulate
with usually different sizes of meshes, and they feature abundant free columellae. Styles are elongated and usually exceed the anthers. Stigmas are
conduplicate-spiral or rarely simple-erect (e.g., T. imperialis, T. plagiotropica; Schill et al. 1988; Brown and Gilmartin 1989b; Gortan 1991). Ovules
are distinctly appendaged at the chalaza. Seeds mostly belong to the ‘juncea’
type, with the ‘narthecioides’, ‘wagneriana’, ‘utriculata’, ‘funckiana’ or ‘mauryana’ types accounting for the rest of the membership (Gross 1988a).
Geographic distribution. Mesoamerica to northern South America
extending into the southern United States and the Antilles. A few species
range into Bolivia and coastal Brazil. The xeric species formerly included
in Vriesea section Vriesea are centered in the northern Andes.
Gardner (1986b) divided this subgenus into five groups and Group One
into eight subgroups according to floral structure (Fig. 6.1A). Although
preliminary and informal, her work indicates that additional alignments
are possible in some subgenera. Gardner also reassigned several species
with included anthers and style to subgenus Tillandsia (e.g., Group Five
with T. atroviridipetala, T. ignesiae, T. lepidosepala, T. mauryana, T. plumosa
and T. tortilis) mostly from subgenus Allardtia (Smith and Downs 1977).
However, stigma morphology among species of Group Five just mentioned
conforms to the convolute-blade type (Figs. 3.1C, 12.1). These species are
therefore provisionally treated here as a distinct group within subgenus
Allardtia. Gardner’s Group Four, to which only T. didisticha and T. filifolia
belong, seems intermediate between subgenera Tillandsia and Allardtia,
but the diagnostic floral characteristics may be convergent.
Of special interest are a number of large, broad-leafed species native to
northern Peru (T. carnosa, T. ecarinata, T. ferreyrae, T. lymanii, T. platyphylla, T. rauhii, T. spiraliflora and T. teres). Stamens and styles in these
cases are only slightly exserted, if at all, and inflorescences are large and
584
Tillandsia and Racinaea
extensively branched. Habits are terrestrial or lithophytic and distributions
occur within the region containing the highest density of Tillandsia species.
Of these eight species, only T. spiraliflora had been assigned to Group Two
and T. rauhii to Group Three. The remaining six are of ‘incertae sedis’
(Gardner 1986b). Vegetative morphology and floral structure suggest that
these species may be similar to the ancestors of both subgenus Allardtia and
Tillandsia.
Subgenus Pseudalcantarea (5 species)
Phyllotaxis is spiral, and no flower fragrances have been reported. Flowers
are arcuate and slightly zygomorphic and completely to almost sessile.
Sepals are symmetric or nearly so, slightly connate, ecarinate, or the adaxial
ones are carinate in T. baliophylla. Sepals, petals, filaments and the base of
the ovary fuse together to form a hypanthium (Beaman and Judd 1996).
Petals are erect, but become flaccid and droop at or following anthesis (T.
heterophylla), white or pale green, rarely green, and equipped with narrow
blades. Stamens exceed the petals (except in T. heterophylla); the versatile
anthers reach 13 mm in length. Styles exceed the petals (except in T. heterophylla), and stigmas are simple-erect to conduplicate-spiral (Brown and
Gilmartin 1989b; Beaman and Judd 1996). Ovules are long (T. grandis, T.
paniculata) or short (T. baliophylla, T. heterophylla and T. viridiflora) and
appendaged at the chalaza. Seeds belong to the ‘wagneriana’ and ‘viridiflora’ types (Gross 1988a,b).
Geographic distribution. From the Gulf region of Mexico to Nicaragua (T.
grandis, T. heterophylla and T. viridiflora), and Hispaniola (T. baliophylla,
T. paniculata).
Subgenus Pseudalcantarea constitutes a relatively little-studied group that
Winkler (1990) considered ancestral to genus Tillandsia. Smith and Downs
(1977) assigned Tillandsia heterophylla to subgenus Allardtia, but the
uniquely flaccid and drooping petals suggest closer relationship to subgenus Pseudalcantarea in spite of the included stamens. Beaman and Judd
(1996) transferred T. grandis and T. paniculata to subgenus Tillandsia. They
further concluded from cladistic analysis that T. baliophylla and T. viridiflora, which they retained in subgenus Pseudalcantarea, may represent a
basal clade within Tillandsia.
Racinaea
585
Racinaea (56 species)
Members are mesic to semixeric herbs with spiral phyllotaxis.
Inflorescences are usually bi- to quadripinnate, rarely simple bearing
usually small, often fragrant flowers. Floral bracts are usually small and
dull-colored, and rarely large and/or bright (e.g., R. multiflora, R. pendulispica, R. seemannii, R. tetrantha, R. undulifolia). Pedicels are strongly succulent, causing the flowers to appear sessile. Sepals are strongly asymmetric,
free or nearly so, broadest near the apex, not exceeding 12 mm with the
adaxial ones ecarinate to carinate. Petals are lingulate, equaling or exceeding the sepals, broadest near the base, often succulent, and with tips that
often curve outward. Corollas are campanulate, white to cream or yellow,
the petals conglutinated in R. tetrantha. Stamens are shorter than the petals
and the often succulent, but apically thin, filaments are arranged in two
series of equal length. During early anthesis, the succulent filaments are
stiff and prevent the anthers from contacting the stigma. Later, the filaments begin to soften and bend inward until the anthers contact the stigma
(facultative self-pollination). Anthers are ovoid and yellow or orange.
Pollen grains are subglobose, 15–25 mm long, with apertures that conform
to the diffuse or the operculum-type. Exines are reticulate to foveolate
(Halbritter 1988; Fig. 12.2). Styles are short, surpassed by the anthers, and
equipped with conduplicate-spiral or simple-erect stigmas (Schill et al.
1988; Brown and Gilmartin 1989b; Gortan 1991). Ovules are obtuse. Seeds
belong to the ‘narthecioides’, ‘viridiflora’ and ‘juncea’ types (Gross 1988a,b).
Geographic distribution. Mainly Andean, but extending into Mesoamerica
and southeastern Venezuela. A few species occur in the Antilles and
southeastern Brazil. Most species inhabit montane rain and cloud forests.
Racinaea, the former subgenus Pseudocatopsis of Tillandsia, is readily distinguishable from the remaining Tillandsia subgenera by its small campanulate flowers that resemble those of Catopsis, and its strongly asymmetric
sepals. These distinctions have been deemed sufficient by Spencer and
Smith (1993) to warrant generic status.
14
Ethnobotany of Bromeliaceae
B. B E NNE T T
Beyond its numerous, valuable ornamentals, Bromeliaceae contains relatively few widely used species, pineapple and Spanish moss being the two
notable exceptions. Pineapple, Ananas comosus, ranks among the most
popular of the tropical fruits (Cobley 1976). Spanish moss (Tillandsia usneoides) was once an important source of low-grade ® ber in the southeastern
United States, with annual production of up to 5000 tons. This wideranging species also has important medicinal uses in several regions, and
an undocumented amount of material continues to sell for ¯ oral arrangements in the United States.
Hortus Third (L. H. Bailey Hortorium 1976) describes nearly 250 selections distributed among 30 genera. Hybrids, some between members of
different genera, substantially augment the hundreds of species in cultivation. Although ¯ owers tend to be small and ephemeral, unusual vegetative
forms, ornamented leaves (e.g., Figs. 2.17B, 2.18B) and brightly pigmented
¯ oral bracts assure horticultural interest. Red, orange or yellow in¯ orescences of the many bird-pollinated bromeliads often signal from impressive
distances. Sizes ranging from diminutive Spanish moss to giant Puya raimondii further entice hobbyists, and shade-tolerance suits many taxa for
indoor cultivation. Frequent capacity to grow on a variety of substrates,
including drift wood, cork slabs and fern roots, further enhances the popularity of bromeliads.
Bromeliaceae ® gure prominently in several additional contexts including
cameo appearances in Star Trek movies and Star Trek: The Next
Generation. Tillandsia usneoides and other epiphytic bromeliads adorn the
sets of Tarzan movies, belying the ® lms' purported African setting. Recent
appearances include Medicine Man, where Sean Connery' s character ® nally
identi® es Tillandsia punctulata, or rather the ants nesting within, as the
source of a cancer cure. The family reaches its cultural zenith in the coastal
587
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588
Ethnobotany of Bromeliaceae
plain of the southeastern United States. Spanish moss, together with live
oaks and magnolias, is a quintessential botanical symbol of the old
American South.
Yet Bromeliaceae is much more than a source of pineapples, house plants
and ® bers for traditional cultures, a fact I began to appreciate in the highlands of southern Peru. Bromeliads are signi® cant elements of the mostly
treeless landscape above 3000 m (Bennett 1988, 1990, 1991). Resident
Quechua distinguish folk taxa of Bromeliaceae, some of which provide
fuel, animal forage, medicine and ritual ornamentation. Children make
whistles from bromeliad leaves, and their parents decorate weddings and
funerals with certain species. The discovery of folk usage and nomenclature
has continued in my work with the Shuar, Quichua and Chachi in Ecuador
and the Seminole in Florida. Each of these indigenous peoples has a folk
taxonomy tailored for local Bromeliaceae. While not essential for survival,
members of this family furnish food, ® ber and inspiration for folklore for
many traditional Neotropical cultures.
Below, I discuss indigenous taxonomy, nonhorticultural uses and indigenous management of Bromeliaceae based on data from my ® eld notes
and publications (Bennett 1986b, 1990, 1992a, 1995, 1997a,b, Bennett et
al. 1999) and other relevant literature. This review identi® es the most
widely used species, and describes the range of derived products and applications.
Folk taxonomy of Bromeliaceae
Designations include such contrasts as attractive/ugly, friendly/hostile,
edible/poisonous. Although members of modern societies make these distinctions daily, classi® cation is even more important for indigenous people,
and it extends beyond simple dichotomies. The Tzeltal ethnobotanical
study of Berlin et al. (1974) presents the most comprehensive analysis of
bromeliad folk classi® cation. The Tzeltal ?ecÈ' refers to members of several
bromeliad genera, including Aechmea, Catopsis, Pitcairnia, Tillandsia and
Vriesea. The Tzeltal name for Tillandsia usneoides is ?icib, which is unrelated linguistically to ?ecÈ' . A similar pattern occurs in Huastec and
Quichua nomenclature. K' ok' om is the Huastec name for Aechmea bracteata and several Tillandsia species, but k' uthay is used for T. usneoides
(Alcorn 1984). Hicundo is the Quechua term for most Tillandsioideae,
while qaka sunka refers to T. usneoides and other diminutive saxicoles
(Bennett 1990). The Seminole in Florida differ in their classi® cation.
Ashome, a generic name for epiphyte, refers speci® cally to T. usneoides. T.
Cambridge Books Online © Cambridge University Press, 2009
Uses of Bromeliaceae
589
Table 14.1. Common indigenous names for the
pineapple (Ananas comosus) in northwest South
America
Group
Chachi
Cofan
Quichua
Quechua
Tikuna
Shuar
Common name
Source
chilla
chiviya
chihuilla
chihuy
chi-ná
chiu
Bennett, ® eld notes
Borman 1976
Orr and Wrisely 1981
Soukup 1970
Schultes and Raffauf 1990
Bennett et al. 1999
fasciculata, T. utriculata and other large arboreal bromeliads are called
ashome chobe, the latter term meaning large (Bennett 1997a,b).
Pineapple is the most widely used bromeliad, and many of its common
names in northwestern South America are related linguistically (Table
14.1). Among the indigenous names are chilla (Chachi), chiviya (Cofan),
chihuilla (Quichua), chihuy (Quechua), chiu (Shuar) and chi-ná (Tikuna)
(Soukup 1970; Borman 1976; Orr and Wrisely 1981; Schultes and Raffauf
1990; Bennett 1992a). Piñuela, a name derived from the Spanish word for
pineapple (piña), is commonly applied to bromeliads in Central America
and parts of South America.
Huicunto and cognates commonly denote epiphytic and certain terrestrial bromeliads through the Andes and western Amazonia. Related names
including huicundo, huiccontoi, huacontoi, huaycontoy, guicundo and
hicundo (Soukup 1970; Joyal 1987; Bennett 1990) are employed as far south
as Chile and Argentina. Achupalla is also used commonly, but more often
for terrestrial species. The Shuar name for epiphytic and some terrestrial
bromeliads is kuish (Bennett et al. 1999).
Uses of Bromeliaceae
Nine, nonexclusive categories of plant uses apply to Bromeliaceae (® ber,
food, forage, fuel, medicine, ornamental, ritual/mythical, miscellaneous,
commercial; based on Bennett et al. 1999). These categories re¯ ect local
applications and perceptions, and may not always coincide with Western
notions of utility. For example, indigenous people consider fruits eaten by
monkeys, or trees inhabited by spirits, to be useful species.
The ® ber category includes bromeliads that provide clothing, thread,
rope and paper. Food and forage groups contain plants consumed by
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590
Ethnobotany of Bromeliaceae
humans and animals, respectively. This category also accounts for plants
used to prepare foods and beverages. Fuel types provide material suitable
for cooking and heating ® res. The medical category is self-explanatory.
Indigenous and rural peoples also cultivate plants simply for their aesthetic
value, whereas ritual/mythical ¯ ora have a place in shamanistic or religious
ceremonies. The miscellaneous category encompasses all other applications, including those associated with hunting, ® shing, personal matters
and crafts. Commercial plants are those valued outside the local community.
Useful bromeliads are listed in Table 14.2. At least 90 species have nonhorticultural utility. Many possess medicinal properties, and two are poisonous. Other species yield fuel, despite the absence of woody tissues. The
ornamental, ritual/mythical, food and medicine categories exceed the
others in size (Table 14.3). No bromeliad provides material for construction
although ® ber extracted from the foliage of several species may be used for
lashing. No dye plants have been reported.
Fiber
At least 13 species yield useful ® ber. Indeed, it and foods are the principal
products derived from Bromeliaceae. Aechmea magdalenae, Ananas
comosus, Neoglaziovia variegata and Tillandsia usneoides top the list for
importance. Indigenous people weave hammocks from Aechmea bracteata,
A. magdalenae and Ananas comosus ® ber (Brücher 1989; Bennett 1992b).
Hammocks are more comfortable than beds in the lowland tropics, and
portability makes them ideal for nomadic life.
Quichua women in lowland Ecuador fashion hammocks from Aechmea
magdalenae ® ber by ® rst removing the spines from leaf margins. Leaves are
then rubbed across the thigh or against a post to loosen the ® bers. Leaves
tied to a smooth log are scraped in turn with a knife to remove all non® brous tissue prior to being soaked in water and then dried in the sun.
Women fashion a strong twine by rolling three ® bers across their thighs
with one hand while using the other to braid the loose ends (Fig. 14.1).
Suitability for hammocks and net bags (shigras) to carry fruit, food and
game is high (Fig. 14.2A).
Puya chilensis leaves yield a rot-resistant ® ber employed in ® shing nets
(Mabberley 1987). Bromelia laciniosa ® bers support a small industry in
Brazil (Benzing 1980). Bromeliad ® bers also yield string, twine, rope and
thread for sewing leather (Mabberley 1987). Philippine natives fashion a
® ne cloth from Ananas comosus ® bers. Brazilian Neoglaziovia variegata is
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Table 14.2. Bromeliad species utilized by humans, their distribution, sources of data, and human uses
Species
Aechmea bracteata (Sw.) Griseb.
Aechmea magdalenae (André) André ex Baker
Aechmea nudicaulis (L.) Griseb.
Aechmea tessmannii Harms
Aechmea tillandsioides (Mart. ex Schultes f.)
Baker
Aechmea zebrina L.B. Smith
Ananas ananassoides (Baker) L.B. Smith
Ananas bracteatus (Lindley) Schultes f. in
Roemer & Schultes
Ananas comosus (L.) Merr.
Ananas lucidus Miller
Ananas paraguazensis Camargo & L.B. Smith
Bromelia alsodes St. John
Bromelia chrysantha Jacq.
Bromelia hemisphaerica Lam.
Bromelia laciniosa Martius ex Schultes
in R. & S.
Bromelia nidus-puellae (André) André ex Mez
Bromelia pinguin L.
Bromelia plumieri (E. Morren) L.B. Smith
Bromelia serra Griseb.
Bromelia urbaniana (Mez) L.B. Smith
Catopsis hahnii Baker
Catopsis morreniana Mez
Catopsis sessili¯ ora (Ruíz & Pavón) Mez
Catopsis subulata L.B. Smith
Distributiona
Referenceb
Usesc
MEX to COL & VEN
MEX to VEN & ECU
MEX
ECU, COL, PER
MEX to BRA
2, 15
12, 16, 21, 27
11
x
26, x
FI, FO, ME
CM, FI, FO, MI
OR, RM
FR, OR
FR, OR
ECU, COL
BRA, ARG, PAR
COL, BRA, PAR, ARG
1, x
12
12
FR, ME, OR
FO
FO
Pantropical
WI, n SA to AB
COL to SUR & BRA
MEX to NIC
COL, VEN, TRI
MEX to COS
BRA
2, 3, 24, 25, 27, 29, 31
12
12
2, 36
24, 36
36
10
CM, FI, FO, ME, MI, RM
FI, FO
FO
FO, ME, OR
FO, ME
FO
CM, FI
COL
MEX, WI to GUI & ECU
MEX, WI to BRA & ECU
BOL, BRA, PAR, ARG
PAR, ARG
MEX
MEX
MEX, WI, to n SA & ECU
MEX
16
3, 12, 16, 21, 25, 26, 36
2, 12, 22, 24, 35
21
Ð
11
11
11
11
FI, FO, MI
CM, FI, FO, ME, MI
FI, FO, ME
FI, CM
FI
OR, RM
OR, RM
OR, RM
OR, RM
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Table 14.2. (cont.)
Species
Catopsis wangerinii Mez & Wercklé
Greigia sodiroana Mez
Greigia sphacelata (Ruíz & Pavón) Regel
Guzmania acuminata L.B. Smith
Guzmania eduardii André ex Mez
Guzmania melinonis Regel
Guzmania monostachia (L.) Rusby ex Mez
Guzmania musaica (Linden & André) Mez
Guzmania sanguinea (André) André ex Mez
Neoglaziovia variegata (Arruda) Mez
Pitcairnia angustifolia Aiton
Pitcairnia breedlovei L.B. Smith
Pitcairnia heterophylla Beer
Pitcairnia integrifolia Ker-Gawl.
Pitcairnia maidifolia (C. Morren) Decasine
in Planchon
Pitcairnia (Pepinia) pulchella Mez
Pitcairnia pungens H.B.K.
Pitcairnia spicata (Lam.) Mez
Pseudananas sagenarius (Arruda) Camargo
Puya chilensis Molina
Puya ferruginea (Ruíz & Pavón) L.B. Smith
Puya ¯ occosa (Linden) E. Morren ex Mez
Puya gigas André
Puya hamata L.B. Smith
Puya lasiopoda L.B. Smith
Distributiona
Referenceb
Usesc
MEX to PAN
ECU
CHI
COL, ECU
COL, ECU
n SA, AB to BOL
ECU
COL
COS, COL, ECU, TRI, TOB
BRA
LA
MEX
MEX to VEN & PER
VEN, TRI
HON to COL & SUR
11
36
21
x
6, 8
6, 7, 8, x
6, 7, 8, x
26
26
15, 21, 27
3
11
24
3
26
OR, RM
CM, FO
CM, FO
FR
FR, OR
FR, OR, MI
FR, ME, OR
OR
OR
CM, FI
ME
OR, RM
ME
ME
OR
ECU
COL to PER
MAR
ECU, BOL, BRA, PAR, ARG
CHI
ECU, PER, BOL
COS, COL, VEN & BRA
COL
COL, ECU, PER
PER
35
36
3
12
14, 21
17
35
26
10, 35
x
FR
ME
ME
FO
FI, ME
FR
ME
OR, MI
FO
FR
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Puya longistyla Mez
PER
Puya medica L.B. Smith
PER
Puya oxyantha Mez
PER
Puya pyramidata (R. & P.) Schultes in
PER
Roemer & Schultes
Puya raimondii Harms
BOL, PER
Puya sodiroana Mez
ECU
Puya weberbaueri Mez
PER, BOL
Puya sp.
PER
Streptocalyx (Aechmea) longifolius (Rudge) Baker COL to BRA & BOL
Tillandsia benthamiana Klotzsch ex Baker
MEX
Tillandsia bi¯ ora Ruíz & Pavón
COS to nw SA
Tillandsia capillaris Ruíz & Pavón
PER, BOL, CHI, ARG
Tillandsia carlsoniae L.B. Smith
MEX
Tillandsia chartacea L.B. Smith
COL, PER
Tillandsia complanata Benth.
GA, COS, BOL, BRA
Tillandsia dasyliriifolia L.B. Smith
MEX to CA
Tillandsia erubescens Schlect.
MEX
Tillandsia fasciculata Sw.
US, MEX, CA, WI to n SA
Tillandsia gilliesii Baker
PER, BOL, ARG
Tillandsia guatemalensis L.B. Smith
MEX to CA
Tillandsia incarnata H.B.K.
COL, ECU
Tillandsia ionochroma André ex Mez
ECU, PER
Tillandsia juncea (Ruíz & Pavón) Poiret
MEX, GA to BOL
Tillandsia lampropoda L.B. Smith
MEX to COS
Tillandsia maculata Ruíz & Pavón
ECU, PER
Tillandsia maxima Lillo & Hauman
BOL, ARG
Tillandsia orogenes Standley & L.O. Williams
MEX to NIC
Tillandsia oroyensis Mez
PER
Tillandsia ponderosa L.B. Smith
MEX, GUA, SAL
Tillandsia purpurea Ruíz & Pavón
ECU, PER
31
36
x
35
FU
ME
FR
FR
x
10, 35, 36
17, x
14, 31
x
35
5, 6, 7
5, 17
11
30
35
11
20
11, 36
33
11
26
5, 7
11
11
33
10
11
17
11
18
FR, FU
FO, FR, ME
FR, FU, RM
ME
FO
ME
OR, RM
ME, MI
OR, RM
FR
FO
OR, RM
FO
FR, OR, RM
RM
OR, RM
CM, OR, RM
FR, OR, MI, RM
OR, RM
OR, RM
RM
FO
OR, RM
FO
OR, RM
RM, MI
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Table 14.2. (cont.)
Species
Distributiona
Tillandsia recurvata (L.) L.
Tillandsia rodrigueziana Mez
Tillandsia rubella Baker
Tillandsia schiedeana Steudel
Tillandsia seleriana Mez
Tillandsia sphaerocephala Baker
Tillandsia streptophylla Scheid. ex Morren
Tillandsia usneoides (L.) L.
Tillandsia utriculata (L.) L.
Tillandsia violacea Baker
Tillandsia xiphioides Ker-Gawler
Tillandsia spp.
Vriesea werckleana Mez
Referenceb
US to ARG
MEX to NIC
ECU, PER, BOL
MEX to WI, COL, VEN
MEX to HON
PER, BOL, ARG
MEX to HON
US to ARG
5, 17, 22, 24, 25, 26
11
10
2
11
5, 7
10
2, 4, 5, 7, 9, 11, 13, 14, 17,
19, 23, 25, 31
US, WI, MEX to VEN
x
MEX, GUA
11
BOL, BRA, PAR, URU, ARG
34
PER, ECU
14, 28, 32, x
MEX to COS
11
Usesc
FO, FR, ME, OR
OR, RM
FO
ME
OR, RM
FR, OR, RM
FR
CM, FI, ME, OR,
RM, MI
FO
OR, RM
ME
FU, ME, OR, RM, CM
OR, RM
Notes: aCountries are shown by the ® rst three letters of their name. Geographical regions are shown by the following two-letter codes:
AB, Amazon Basin; CA, Central America; GA, Greater Antille; LA, Lesser Antilles; MAR, Martinique; SA, South America; SAL,
Salvador; WI, West Indies.
b
The numbers correspond to the following references: 1Alarcón 1988; 2Alcorn 1984; 3Ayensu 1981; 4Bennett 1986b; 5Bennett 1990;
6
Bennett 1992a; 7Bennett 1995; 8Bennett et al. 1999; 9R. B. Bennett 1954; 10Benzing 1980; 11Berlin et al. 1974; 12Brücher 1989; 13Burlage
1968; 14Chávez Velásquez 1977; 15Clark 1965; 16Duke 1986; 17Franquemont et al. 1990; 18Goodspeed 1961; 19Hayward 1947; 20Laferriere
et al. 1991; 21Mabberley 1987; 22McVaugh 1989; 23Moerman 1986; 24Morton 1981; 25Núñez Meléndez 1982; 26Pérez-Arbeláez 1956;
27
Purseglove 1972; 28Rowe 1963; 29Schultes and Raffauf 1990; 30Smith and Downs 1977; 31Soukup 1970; 32Steele 1964; 33Towle 1961;
34
Usher 1974; 35von Reis Altchul 1973; 36von Reis and Lipp 1982. x, unpublished notes.
c
CM, commercial; FI, ® ber; FO, food; FR, forage; FU, fuel; ME, medicine; MI, miscellaneous; OR, ornamental; RM, ritual/mythical.
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595
Table 14.3. Major use categories and
the number of species found in each
Use category
Number of species
Fiber
Food
Forage
Fuel
Medicine
Ornamental
Ritual/mythical
Miscellaneous
Commercial
13
25
21
4
25
37
30
10
10
one of the most important ® ber-producing bromeliads. Its leaves yield a
commercial-grade product, called caroá, suitable for manufacturing
cordage, coarse fabric, mats and reinforced paper. Each shoot bears about
30 leaves, but only two to four are suitable for processing at each harvest.
Fiber content is 12± 14% (Clark 1965; Mors and Rizzini 1966; Purseglove
1972).
Fibrous tissues from Tillandsia usneoides, speci® cally the heavily scleri® ed stele, once served as a horsehair substitute in upholstery and mattresses, and as packing material (Hayward 1947; R. B. Bennett 1954;
Pérez-Arbeláez 1956; B. C. Bennett 1986b; Mabberley 1987). Thirty-® ve
processing plants once operated in Florida alone (Jensen 1982).
Preparation was crude, but inexpensive. Fresh material, usually collected in
cypress swamps, was wetted, then placed in pits for 6± 8 months to allow
the soft tissues to rot away. Final processing occurred off-site where the
® bers were cleaned, sorted and baled (Jensen 1982). Native North
Americans weaved clothes from this rough material (Burlage 1968; Wilson
1989).
Food
Although Ananas comosus (pineapple) is by far the most widely utilized
bromeliad, at least 25 additional species provide edible fruits, leaves or meristems. The ® rst European record of the pineapple dates from Columbus' s
second voyage. In a letter describing his arrival on Guadeloupe on 4
November 1493, the explorer writes:
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Ethnobotany of Bromeliaceae
Figure 14.1. Bromeliad uses. (A) A Quijos Quichua woman extracting ® bers from
Aechmea magdalenae leaves. (B) A Quijos Quichua man combing Aechmea magdalenae ® bers and sitting on a hammock made from the plant.
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Uses of Bromeliaceae
597
Figure 14.2. Bromeliad uses (continued). (A) Shigra (cloth bag) made from Ananas
comosus ® bers. (B) In¯ orescence of Aechmea magdalenae. The mature infructescence is edible. (C) Puya raimondii growing in southern Peru. The leaf bases are collected for fuel. (D) Tillandsia usneoides and other Tillandsia species (in bucket)
being sold for Christmas decorations in Quito, Ecuador.
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Ethnobotany of Bromeliaceae
`There were some [fruits] like artichoke plants, but four times as tall, which gave a
fruit in the shape of a pine cone, twice as big, which fruit is excellent, and it can be
cut with a knife like a turnip and it seems to be wholesome.'
(Purseglove 1972)
Pineapple also impressed other European explorers. Oveido wrote in his
Historia General y Naturales de las Indias, of 1535, `[t]here are no other
fruits in the whole world to equal them for their beauty of appearance, delicate fragrance [and] excellent ¯ avor' (Purseglove 1972). As with other New
World domesticates, Spanish explorers carried pineapples to all corners of
the tropics. Today, we associate the fruit with Hawaii, but the Hawaiian
pineapple, like the Irish potato, originated in South America. Hawaii did
not receive its ® rst pineapples until the early 1800s.
Pineapple probably originated in the Paraná± Paraguay River drainage
system (Purseglove 1972). Indigenous peoples were already cultivating the
plant throughout the New World tropics by the time Columbus arrived.
Resemblance to a pine cone (piña in Spanish) prompted the English name
pineapple. Ananas is derived from the Tupí-Guraní language, an idiom still
spoken in Paraguay and southern Brazil. Ananas ananassoides, A. bracteatus, A. lucidus, A. paraguazensis and Pseudananas sagenarius, which also
yield edible fruits, are all possible ancestors of the pineapple (Brücher
1989). Certain species of Aechmea, Bromelia and Greigia also bear edible
fruits (Fig. 14.2B).
Today, pineapple ranks among the most widely cultivated tropical fruits,
growing best between 25° N and S latitude where rainfall ranges from 1000
to 1500 mm. However, crops can survive wherever annual precipitation falls
between 635 and 2500 mm and frost is absent (Purseglove 1972). Fruits are
often eaten fresh, but much of the commercial harvest is canned. A fermented beverage is made from pineapple fruits in Panama (Duke 1986) and
throughout much of Amazonia. Fermented and nonfermented drinks are
also made from Aechmea magdalenae, Bromelia alsodes, B. hemisphaerica,
B. nidus-puellae, B. pinguin and B. plumieri fruits (von Reis and Lipp 1982;
Alcorn 1984; Duke 1986; Mabberley 1987). Some indigenous Americans
consume bromeliad leaves and meristems. The tender leaf bases of Puya
hamata are eaten in salads and ground into ¯ our (von Reis Altchul 1973).
A sweet drink is concocted from young in¯ orescences and soft leaf tissues
in southern Ecuador (Benzing 1980). Leaf bases of P. sodiroana are edible,
and Tillandsia complanata leaves are used to wrap tamales (von Reis
Altchul 1973). The Pima of Mexico occasionally eat T. erubescens and T.
recurvata in¯ orescences, apparently attracted by the high sugar content
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Uses of Bromeliaceae
599
(Laferriere et al. 1991). Shoot apices of T. maxima and T. rubella are consumed in Bolivia and Argentina (Benzing 1980). Highland Quechua drink
water trapped in the phytotelmata of Tillandsia oroyensis (Franquemont et
al. 1990) much as the Seminole of southern Florida once used Tillandsia
utriculata (Bennett, ® eld notes).
Forage
At least 21 species produce forage suitable for domesticated or wild
animals. Monkeys eat the young in¯ orescences and drink water impounded
by numerous species including Aechmea tessmannii, A. tillandsioides, A.
zebrina, Guzmania acuminata, G. eduardii, G. melinonis and G. monostachia,
and many forest people in turn eat these primates (Fig. 14.3A). Hunting is
more successful where forest canopies host abundant phytotelm
Bromeliaceae. Other animals also depend on these plants and some of their
terrestrial relatives. Puya sodiroana is a `favorite food of bear' (von Reis
Altchul 1973; von Reis and Lipp 1982), probably the rare Andean spectacled bear (Tremarctos ornatus).
Dendrobatid frogs inhabit the tanks of some epiphytic bromeliads. Most
indigenous people tip poison darts with phytotoxins (often species of
Loganiaceae and Menispermaceae), but inhabitants of Colombia' s Chocó
use toxic skin secretions produced by these animals to arm blowgun darts.
One dendrobatid species is so potent that a single individual contains
enough poison to kill 100 people (Pennisi 1992). Knowledge of which bromeliads host frogs assures the hunter a continuous supply of curare substitutes.
Scores of other animals consume bromeliads given the opportunity.
Mules eat Pepinia pulchella leaves (von Reis Altchul 1973), and goats
consume Tillandsia recurvata shoots (Morton 1981). Native Andean people
collect the foliage of Puya ferruginea, P. pyramidata, P. sodiroana and P.
weberbaueri (von Reis Altchul 1973; Franquemont et al. 1990) and the
seeds of P. lasiopoda, P. oxyantha and P. weberbaueri (Fig. 14.4C; Bennett,
® eld notes) to help raise domesticated guinea pigs. Cattle, sheep and llamas
feed on bromeliads including Puya sodiroana, P. weberbaueri, Tillandsia
bi¯ ora, T. chartacea, T. fasciculata, T. ionochroma, T. sphaerocephala and T.
streptophylla among others (von Reis Altchul 1973; Smith and Downs
1977; Benzing 1980; von Reis and Lipp 1982; Bennett 1990; 1995; ® eld
notes; Franquemont et al. 1990).
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Ethnobotany of Bromeliaceae
Figure 14.3. Bromeliad uses (continued). (A) Bromeliads are one of the preferred
foods of the woolly monkey (Lagothrix lagothicha), shown here foraging for young
in¯ orescences in a patch of terrestrial specimens. (B) Leaf bases of Puya raimondii
collected for fuel in Peru.
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Uses of Bromeliaceae
601
Figure 14.4. Bromeliad uses (continued). (A) Tillandsia sphaerocephala, known as
aya huicunto in Quechua, is used as a funeral decoration in the highlands of Peru.
(B) Tillandsia ionochroma, known as huicunto in Quechua, is used as a wedding decoration in the highlands of Peru. (C) Puya weberbaueri seeds are collected for
guinea pig (cui) feed. (D) Huayruro, a young Quechua boy, with a whistle made
from a Tillandsia ionochroma leaf.
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Ethnobotany of Bromeliaceae
Fuel
Several species each in Tillandsia and Puya provide fuel in the high Andes
and coastal deserts of Peru and Ecuador (Bennett, ® eld notes; Rowe 1963;
Soukup 1970). Puya weberbaueri, a dominant species on valley slopes in the
southern Andes, assumes exceptional importance for this reason. Leaf
bases and stems burn long and hot. Villagers near Cuyo-Cuyo, Peru set ® res
to enhance the growth of this terrestrial bromeliad. Like Serenoa repens in
the southeastern United States, P. weberbaueri ¯ ourishes in the resulting
open habitat. Burning destroys foliage and eliminates competing species,
but the rhizomes survive. Fire also promotes rapid regrowth, which may be
more palatable to domesticated animals. Charred leaf bases are easier to
collect after their spiny leaves have been removed, and this material readily
ignites. The highland Quechua of southern Peru use the leaf bases of P. raimondii in similar fashion (Figs. 14.2C, 14.3B).
Medicine
At least 25 bromeliad species possess purported therapeutic properties, not
a surprising number considering that indigenous cultures tend to use larger
portions of local ¯ oras for medicines than for any other purpose (e.g.,
Bennett et al. 1999). Subfamily Bromelioideae contains the largest number
of medicinal species. The Huastecs of Mexico drink water drawn from the
phytotelmata of Aechmea bracteata to treat fever. The same ¯ uids are
employed for headaches, dizziness, eye trouble and upset stomachs caused
from `eating too many chiles' (Alcorn 1984). Lowland Quichua in Ecuador
allow children to inhale vapors from boiling A. zebrina leaves to relieve
insomnia (Alarcón 1988).
Ananas comosus has medical utility attributable to the presence of bromelain, a proteolytic enzyme similar to papain from Carica papaya.
Bromelain is currently marketed by William H. Rorer, Inc. under the name
Ananase to treat in¯ ammation and related pain. Topical applications also
promote wound healing (Physician' s Desk Reference 1984; Hensyl 1989).
Rural people apply pineapple juice for similar purposes (Núñez Meléndez
1982). A poultice of young leaves is applied to sprains (Ayensu 1981).
Pineapple is also used to treat jaundice, ulcers, intestinal ailments, sore
throats, urinary problems and dyspeptic ¯ atulence. Sweetened juice promotes digestion and prevents sea sickness according to some users in
Venezuela. Juice expressed from the vegetative buds is ingested to treat respiratory ailments, and that from unripe pineapples supposedly works as a
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Uses of Bromeliaceae
603
powerful abortifacient. Serotonin, a vasoconstrictor, further characterizes
this fruit. Antihelmintic (vermifuge), antiscorbutic (treatment for scurvy),
cholagogic (promotes ¯ ow of bile), decongestant, diaphoretic (causes perspiration), diuretic, ecbolic (smooth muscle stimulant), emmenagogic
(agent that increases menstrual ¯ ow), purgative and refrigerant (relieving
fever or producing cooling sensation) activities are also attributed to pineapple fruit (Soukup 1970; Ayensu 1981; Morton 1981; Alcorn 1984; Duke
1986; Schultes and Raffauf 1990; Bennett et al. 1999). Steroids from pineapple foliage possess oestrogenic activity.
Boiled, young Bromelia alsodes leaves serve as a poultice to treat trauma
and broken bones. Huastecs use the same plant to combat fungal infections
in domesticated animals (Alcorn 1984). Basal portions of B. chrysantha
leaves are used to disinfect wounds (von Reis and Lipp 1982), and a diuretic and vermifuge are prepared from its fruits (Morton 1981). Bromelia
nidus-puellae berries possess antiscorbutic properties (Duke 1986).
Bromelia pinguin, like pineapple, contains bromelain with effects similar to
that of Carica papaya for treating oedema, in¯ ammation, fever, coughs,
bronchitis, lung congestion, intestinal parasites and rheumatism (Ayensu
1981; Morton 1981; Núñez Meléndez 1982). Fruits are reported to be antiscorbutic and diuretic, and capable of causing blood to ¯ ow more freely to
relieve cramps (Duke 1986). Trichomes from Bromelia plumieri leaves are
applied to burns (von Reis Altchul 1973; Morton 1981).
Two pitcairnioid genera, Pitcairnia and Puya, contain several medicinal
species. The white foliar trichomes of Pitcairnia angustifolia and Pitcairnia
spicata are mixed with honey to treat thrush and to heal cut umbilical cords
(Ayensu 1981). An infusion of young Pitcairnia heterophylla leaves reportedly helps control dysentery (Morton 1981). Waxy powder (probably trichome shields) from the abaxial surfaces of Pitcairnia integrifolia leaves is
rubbed on venereal lesions in males (Ayensu 1981). An infusion made from
ground Pitcairnia pungens root is used for kidney and liver ailments, and
the cooked mixture works as a diuretic (von Reis and Lipp 1982).
A preparation from Puya chilensis is used as a hemostatic, and an extract
made from ¯ owers is applied to hernias (Chávez Velásquez 1977). A leaf
decoction of Puya ¯ occosa has purgative properties (von Reis Altchul
1973). Von Reis and Lipp (1982) note the treatment of pneumonia with a
stem decoction from the aptly named Puya medica. Some rural
Ecuadorians consume Puya sodiroana shoots to treat kidney ailments
(Benzing 1980). Peruvian highlanders alleviate throat in¯ ammation, earaches, nose bleeds and swellings with juice from the ¯ owers of an undetermined Puya (Soukup 1970; Chávez Velásquez 1977).
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Ethnobotany of Bromeliaceae
Tillandsioideae also include important medicinal species. The Chachi of
Ecuador treat earaches with juice from Guzmania monostachia in¯ orescences (Bennett, ® eld notes). An infusion of Tillandsia benthamiana mixed
with alcohol is taken each morning to cure anemia or kidney troubles (von
Reis Altchul 1973). Highland Quechua speakers in Peru treat coughs with
a medication derived from T. capillaris (Franquemont et al. 1990). One of
the more widely employed Tillandsioideae is T. recurvata; its utility includes
treatments of hemorrhoids, gallbladder afflictions and menstrual irregularities (Morton 1981; Núñez Meléndez 1982). The Huastecs drink a cold
water infusion of crushed T. schiedeana leaves, and apply the foliage to the
head to relieve fever and headaches (Alcorn 1984).
Tillandsia usneoides is the most widely distributed bromeliad, hence, not
surprisingly, the species with the most varied medicinal utility. Its uses
include treatments for coughs, fever, hemorrhoids, hernias, measles, mouth
sores, rheumatic arthritis, sores, and ailments of the lung, liver, kidney and
heart (Burlage 1968; Soukup 1970; Chávez Velásquez 1977; Núñez
Meléndez 1982; Alcorn 1984; Moerman 1986). The highland Quechua of
Peru treat dandruff with a rinse made from this plant (Bennett 1990).
Huastec women drink a decoction made from a handful of T. usneoides as
a contraceptive, but consider this practice dangerous (Alcorn 1984). A
decoction of Tillandsia xiphioides ¯ owers reportedly diminishes chest pain
(Usher 1974), and hot baths made from several Tillandsia species reduce
discomfort associated with neuritis (Steele 1964).
Ornamental and ritual/ mythical
Many of the bromeliads employed in religious festivals possess ornamental and ritual value. Columbus reported that some Native Americans hung
crowns of pineapple leaves over the entrances to their houses as a sign of
hospitality, a tradition that continues in Europe and North America.
Pineapple motifs are carved on doorways and gateposts as welcome signs
(Haughton 1978). Tzeltal speakers in Mexico suspend specimens of
Aechmea, Catopsis, Pitcairnia, Tillandsia and Vriesia on doorways of the
homes of religious officials and alongside religious shrines in their own
households (Berlin et al. 1974).
Immigrants from the sierra and indigenous Quichua place Aechmea tessmannii, A. tillandsioides and A. zebrina on trees around their lowland
Ecuadorian homes (Bennett, ® eld notes). The Ecuadorian Shuar do the
same with Guzmania eduardii, G. melinonis and G. monostachia (Bennett et
al., 1999). Huastecs decorate their ® esta sites with Bromelia alsodes (Alcorn
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Uses of Bromeliaceae
605
1984). Méluzin (1997, 1998) describes the uses of several Catopsis and
Tillandsia species by the Lenca of Honduras. She attributes utility for
maize-planting rituals to the resemblance between the immature in¯ orescences and young corn stalks and to the exceptional longevity of dislodged
epiphytes in dry environments such as an altar.
Several Tillandsia species serve contrasting purposes in southern Peru.
Highland Quechua speakers adorn wedding sites with Tillandsia bi¯ ora
and T. ionochroma (Bennett 1990). Both species are called huicunto in the
indigenous idiom, and display shiny red or green leaves. The Quechua place
ash-colored Tillandsia sphaerocephala shoots on caskets at funerals,
perhaps to signify death. Its Quechua name, aya huicunto, means death or
soul bromeliad (Fig. 14.4A,B). According to the archaeological record, the
funereal use of bromeliads is long-standing. Tillandsia gilliesii and T. maculata were used to wrap some Peruvian mummies (Towle 1961).
Tillandsia usneoides serves as a Christmas ornament throughout Latin
America (Fig. 14.2D), often in nativity scenes as the bed for the Christ
® gure (Berlin et al. 1974; Alcorn 1984; Bennett 1990, 1995; Franquemont
et al. 1990). Highland Quichua speakers sell T. usneoides, T. incarnata and
several other species during the Christmas season in Quito, Ecuador
(Bennett, ® eld notes; Fig. 14.2D). Tzeltal speakers hang T. usneoides on
doorways during celebrations (Berlin et al. 1974). Most important,
perhaps, is its cultural signi® cance in the southern United States: columnist
James Kilpatrick describes T. usneoides as `an indigenous, and indestructible part of the Southern character; it blurs, conceals, softens, wraps the
hard limbs of hard times in a fringed shawl' (Bell and Wilson 1989).
Miscellaneous
Additional uses ® t none of the categories described so far. For example,
Carib warriors in the West Indies produced an arrow poison from decaying
pineapple fruits (Haughton 1978). Llipta, a substance obtained from the
ash of many bromeliads, including dried Puya weberbaueri ¯ owers
(Franquemont et al. 1990), yields the alkalinity needed to release the active
constituents from chewed coca leaves (Erythroxylum coca). Living fences
constructed of Aechmea magdalenae, Ananas comosus, Bromelia niduspuellae, B. plumieri and Puya gigas protect gardens from animals, and
houses from marauders (Bennett, ® eld notes; Pérez-Arbeláez 1956; Morton
1981; Duke 1986). Any associated food or ® ber production constitutes a
bonus.
Quechua children make whistles from the leaves of Tillandsia ionochroma
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606
Ethnobotany of Bromeliaceae
(Fig. 14.4D; Bennett 1990, 1995). Huastecs use T. usneoides as nesting
material in chicken houses (Franquemont et al. 1990). Latin Americans
often erect a monument where someone has died along a trail or road. In
coastal Peru, mourners sometimes spell the deceased person' s name with
transplanted Tillandsia purpurea. Forlorn travelers used the same material
to inscribe `in® ernillo' (little hell) at one remote outpost (Goodspeed 1961).
The lowland Quichua of Ecuador practice the most beguiling use of a bromeliad. A tea prepared from the yellow ¯ owers of Guzmania melinonis supposedly contains a powerful aphrodisiac (Bennett, ® eld notes).
Commercial
At least 10 bromeliad species have commercial importance beyond horticulture (Table 14.3). Annual pineapple production exceeds 107 metric tons,
more than half of which came from Thailand (FAO Production Yearbook
for 1992 and 1993, cited in Simpson and Connor-Ogorzaly 1995). Local
industries rely on a wider range of taxa.
Tourists pay up to US$60 for quality hammocks and US$5 for shigras
made from Aechmea magdalenae and Ananas comosus ® ber by indigenous
people. Bromelia laciniosa, B. pinguin and B. plumieri also yield commercial
® bers, and the latter produces marketable fruit (Brücher 1989; McVaugh
1989). Greigia sodiroana fruits are sold in Ecuador. Bromelia serra provides
caraguata or chaguar ® ber used to manufacture sacks, cordage and, some
day perhaps, paper (Mabberley 1987). Neoglaziovia variegata forms the
basis of a substantial ® ber industry in Brazil, with 10 000 to 15000 tons of
® ber annually. Known as caroá, this material is well suited for nets, and
offers promise as a component of arti® cial silk (Clark 1965; Mabberley
1987).
Quichua speakers in Ecuador sell Tillandsia incarnata, T. usneoides and
other Tillandsia species for Christmas decorations for up to US$1 per plant
(Bennett, ® eld notes). A 4-oz bag of Spanish moss retails for US$3.29, but
no market remains for its ® bers in the United States.
Bromeliad phytotelmata sometimes harbor fauna more valuable than the
plant. John Daly discovered an anesthetic in a skin extract of the poison
dart frog Epipedobates tricolor (Pennisi 1992). Epibatidine, the active constituent, operates through a novel mechanism. Alkaloids from bromeliaddwelling frogs have much medical potential (Pennisi 1992).
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607
Indigenous management of bromeliads
Table 14.4. Commonly cultivated bromeliads and those with
commercial value
Species
Commercial value
Aechmea bracteata
Aechmea magdalenae
Ananas bracteatus
Ananas comosus
Bromelia laciniosa
Bromelia pinguin
Bromelia plumieri
Bromelia serra
Greigia sodiroana
Neoglaziovia variegata
Tillandsia incarnata
Tillandsia usneoides
x
x
x
x
x
x
x
x
x
x
x
Cultivated
Usesa
x
x
x
x
FI, FO, ME
FI, FO, MI
FO
FI, FO, ME, RM, MI
FI
FI, FO, ME
FI, FO, ME, MI
FO
FO
FI
OR, RM
FI, ME, OR, RM, MI
x
x
x
x
Note: aFor explanation of abbreviations, see Table 14.2.
Indigenous management of bromeliads
The distinction between cultivated and wild ¯ ora is often less pronounced
in tropical than in temperate latitudes. Likewise, boundaries between ® elds,
fallows and forests are relatively ambiguous. Useful plants, including bromeliads, may be planted, protected or collected in natural vegetation
(Bennett 1992b). Ananas comosus grows only as a cultigen in ® elds and
gardens, although it may persist in abandoned agricultural plots. Other
commonly cultivated bromeliads are listed in Table 14.4. Aechmea bracteata (Central America) and Ananas bracteatus (Paraguay) were farmed for
their edible fruits before Ananas comosus was introduced (Brücher 1989).
Some unimproved genotypes, such as Aechmea tillandsioides, receive little
care following transplantation. Many epiphytic ornamentals fall into this
subcategory.
A second management technique consists of preserving desired material
as forests and ® elds are converted for human use. Higher yields are encouraged by removing competitors, a practice often employed to maintain
Aechmea magdalenae in old fallows. Puya raimondii and P. weberbaueri are
not sown, but they are often spared when clearing occurs. Prescribed ® res
enhance plant utility as fuel in addition to eliminating weeds.
Some bromeliads are neither planted, nor are serious efforts made to conserve them. Tillandsia usneoides, a common saxicole and epiphyte in parts
of the Andes, is generally ignored except at Christmas. No protection seems
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608
Ethnobotany of Bromeliaceae
necessary to maintain supplies in much of South America. Overcollection
for ® ber and disease eliminated some populations, prompting attempts to
cultivate the survivors. Tillandsia streptophylla (Benzing 1980) and T. sphaerocephala (Bennett 1990, 1995) are dislodged from rock faces so animals
may eat them; harvest of the latter species is limited. Most individuals grow
on inaccessible rock faces and thus are naturally protected.
Humans have expanded the ranges of many useful bromeliads. Ananas
comosus occurred throughout tropical America and the Caribbean by the
time Europeans arrived (Brücher 1989). Aechmea magdalenae was introduced to Trinidad in 1924 (Williams 1951). Portea petropolitana has
recently naturalized in Hugh Taylor Birch State Recreation Area (Fort
Lauderdale, Florida). Billbergia pyramidalis and Dyckia brevifolia have
established elsewhere in the state (Wunderlin 1998). Indigenous cultures
and modern societies alike use many bromeliad species, and we must consider this fact when developing conservation strategies. Further linguistic
analyses and ethnobotanical study will identify additional bromeliads, and
determine the efficacy of applications in traditional medicine.
Cambridge Books Online © Cambridge University Press, 2009
15
Endangered Bromeliaceae
M. DIMMIT T
The rapid and accelerating destruction of the world’s tropical forests is
widely known. Less appreciated are two additional facts: half of the estimated 300 000 species of higher plants occur in these biomes, and epiphytes make up to half of the vascular floras of certain tropical forests
(Benzing 1990). Moreover, bromeliads comprise most of the biomass of
arboreal vegetation at many wet montane tropical American sites. Because
members of this family significantly influence important forest processes
and provide substrates and other resources for much canopy-based fauna,
their preservation is vital to broader conservation efforts. Terrestrial
Bromeliaceae, about half of the family, sometimes dominate communities
where climates are harsh (e.g., cool or hot and dry) or substrates (e.g., rock)
mandate unusual plant adaptations to obtain nutrients and water
(Chapters 4 and 5). Too little information is available in the literature on
the sizes and genetic structures of bromeliad populations to determine if
more than just a handful of taxa are truly endangered (Chapter 6), and thus
the following discussion draws heavily on unpublished observations and
findings on other taxa.
Bromeliads tend to be locally abundant if not as diverse as co-occurring,
ecologically similar flora such as Orchidaceae. Individual phorophytes or
rock faces routinely support hundreds to millions of adults. One of the
many populations of Tillandsia purpurea in the coastal desert of Peru (PanAmerican highway, kilometer 348 north) covered approximately six square
kilometers at a density of ,50 ramets per square meter to total some 300
million ramets (Dimmitt 1989a). Ranges of species vary from exceptionally
broad to as narrow as any reported for other vascular flora. Tillandsia
recurvata occurs discontinuously from the southern United States to southern Argentina, an area almost as great as that occupied by the entire family.
By contrast, T. albertiana, T. grazielae and T. sucrei, among other members
609
610
Endangered Bromeliaceae
of this same group of specialized xerophytes, inhabit one or a few known
localized sites. Greatest insularity involving the epiphytes occurs in northwest Central America and in the Andes where precipitous topography and
exceptionally favorable climate promote exuberant speciation.
Isolated granitic outcrops in southeastern Brazil and equally ancient
substrates in the Guayanan highlands have also encouraged radiations that
again reflect propensities for unusual rooting media in Bromeliaceae
(Chapter 9). About 38% of the bromeliad species described in Flora
Neotropica (Smith and Downs 1977) are known only from the type locality. The true figure is probably higher, because most of the several hundred
species described since Smith and Downs’s monograph was published
appear to be narrow endemics. Otherwise, they would have been discovered
sooner.
The purported rarity of some bromeliads may reflect accessibility to collectors more than true ranges. Several species first reported as highly insular
eventually turned up elsewhere (e.g., Tillandsia chiapensis in Mexico and T.
dexteri in Costa Rica). Despite the efforts of hundreds of amateur, commercial and scientific collectors willing to travel great distances through
remote and difficult terrain, the ranges of many species remain poorly
known.
Factors threatening bromeliad populations
Habitat destruction presents the greatest threat to endangered biota,
including vulnerable Bromeliaceae. Growing demand for food and natural
resources assure continued forest destruction throughout tropical America.
About 45% of all tropical forests are already gone (Koopowitz 1992), and
the figure for the Neotropics is ,19% (Koopowitz et al. 1994). About
38000 acres (15300 hectares) a day, or 22000 square miles (56 000 square
kilometers) per year, disappear in Latin America. Annual losses are estimated to be 4.6% in Paraguay and 3.9% in Costa Rica, and rates are
increasing almost everywhere (World Resources Institute 1986). More than
half of the forests in Costa Rica, Ecuador, El Salvador, Honduras and
Nicaragua have been replaced (Koopowitz et al. 1994). In Ecuador west of
the Andes, only 0.1% of the lowland tropical rainforest remains intact
(Gentry and Parker 1992). Unknown, but sizable, portions of the surviving
woodlands are severely degraded (Redford 1992).
Stochastic models indicate that mass extinction is well underway. More
than 5000 species of orchids (20% of the family) may be recently extirpated,
and about 50 more experience the same fate every year (Koopowitz 1992).
Factors threatening bromeliad populations
611
Bromeliads have fared better because proportionally more New World
tropical habitat remains relatively undisturbed. Assuming 15% current
deforestation and an annual clearing rate of 0.7–1.0%, the model indicates
that 150 species of Bromeliaceae (6% of the family) are already lost and
8–12 more members will disappear during each of the next few years (H.
Koopowitz and A. Thornhill unpublished data).
Habitat destruction probably accounts for a substantial portion of the
bromeliads lost to date. No specimens of Tillandsia klausii have been found
since its type locality in Chiapas, Mexico burned (H. Luther, personal communication). Losses short of extirpation are eroding genetic diversity in
some of the more widespread species. Agriculture has displaced entire populations of Guzmania blassii and Aechmea magdalenae in Costa Rica
(Skotak 1989). The northernmost population of Tillandsia exserta in
Sonora, Mexico, which differs from those farther south by its dense, silvery
indumentum, will soon be eliminated by resort development (personal
observation).
Natural events occasionally rival human activity for destructive power.
That Tillandsia purpurea population described above and many others in
the same Peruvian desert habitats nearly vanished during the El Niño year
of 1982 (P. Isley, personal communication), probably suffocated by the
several meters of precipitation that fell in this usually rainless region
(Chapters 4 and 9). Seedlings were evident in some localities during 1988,
however (P. Koide, personal communication).
Bromeliad populations have been depleted by collection and a variety of
other willful acts. Peruvians set fire to most of the inflorescences of Puya
raimondii before the seed can mature. Vriesea hieroglyphica and V. fosteriana have been nearly eliminated in nature to stock urban landscapes in
southeastern Brazil (Leme 1984; H. Luther, personal communication).
However, heavy utilization does not necessarily deplete populations. Each
year tens of thousands of Tillandsia tectorum and relatives with similar
silvery foliage end up simulating snow in Christmas displays in Ecuador (H.
Luther, personal communication). Despite heavy local consumption and
additional collection for sale, this species remains abundant.
Some authorities believe that commercial collectors are threatening
numerous bromeliad populations (Leme 1984; Read 1989; Rauh 1992), but
scientific confirmation is scarce. Importation records offer little help
because they generally fail to identify plant material beyond family.
At greatest potential risk are the xerophytic species, particularly
members of Tillandsia, because these plants grow more slowly than the
other desirable bromeliads. Long life cycles also increase incentive to collect
612
Endangered Bromeliaceae
wild specimens for direct sale. Market demand and regulations and enforcement prevailing in the countries of origin further determine which species
face high risk.
Amateur as opposed to commercial collectors are too few and the hobbyist market too small to create significant demand for any but the most
appealing of the insular species. Of the approximately 4000 people in the
United States who belong to bromeliad societies, most grow only the relatively common tillandsias (personal observations; H. Luther, personal
communication). About 200 ambitious Tillandsia collectors reside in
Germany, but of these only 15–20 individuals maintain rare taxa (R.
Ehlers, personal communication).
A growing mass market presents greater challenge than the hobbyist.
Several tillandsias have become popular as ephemeral decorations, especially in Europe where tens of millions of plants are purchased annually.
About half of the flower shops and 70% of the supermarket garden centers
in southwestern Germany offer one or more of these species (TRAFFIC
Germany 1988). Tillandsia species are also popular in parts of the United
States, for example southern California where nearly every garden store
and nursery stocks them. Import volume is telling in this instance. About
18 million plants (not all Tillandsia) were imported into the United States
in 1989 (estimated from TRAFFIC USA 1992; Table 15.3). Buyers in
Germany and the Netherlands imported a combined 120 000 kg consisting
of at least 13 million specimens in 1988 (TRAFFIC Europe, 1992;
http://www.traffic.org). These figures increase nearly every year.
Losses assure that the number of bromeliads collected greatly exceeds
that eventually sold. Schmidt (1992) estimated that only 7% of collected
Tillandsia plants remain exportable; weather, insects and unskilled collectors (the Indians who are usually hired to collect tend to mishandle the
plants) eliminate the others. Many specimens also die during shipping and
storage in dark warehouses.
Few Tillandsia species are traded extensively. The majority of the ,550
Tillandsia species listed by Kiff (1991) and the closely related vrieseas (hundreds more) are either phytotelm types such as T. ferreyrae and T. tetrantha
or less attractive nonimpounding forms (e.g., T. chaetophylla, T. schiedeana,
T. narthecioides). More than 200 taxa are available in the United States, but
fewer than 15 are regularly sold in lots of tens of thousands or more (P.
Isley, personal communication; Table 15.1). About 130 taxa are merchandized in the United Kingdom, but just eight dominate the market (Blakesley
and Powell 1992; Table 15.2). Likewise, 15 of the ,160 taxa available in
Germany comprise its mass market (TRAFFIC Germany 1988).
Factors threatening bromeliad populations
613
Table 15.1. Most heavily traded
Tillandsia species in the United States
T. aeranthos (all nursery-grown)
T. bergeri (all nursery-grown)
T. brachycaulos
T. bulbosa
T. butzii
T. caput-medusae
T. fuchsii (5argentea)
T. ionantha
T. juncea
T. kolbii (5ionantha scaposa)
T. magnusiana
T. tectorum (? not more than 15 000 per year)
T. tricolor
T. xerographica
Irresponsible collectors are jeopardizing the future of the occasional
undistinguished, but very rare, species. Tillandsia brachyphylla, T. grazielae
and several other taxa are known only from one rock outcrop in Brazil. A
major fraction of the population constituting the first species was taken in
1991 for sale in Germany where most of the plants died from neglect (H.
Luther, personal communication). Rock-climbing equipment was used to
obtain most of the known individuals of the second species.
Most of the bromeliads offered for sale originate from one of two
sources. Fifty-five percent of the bromeliads imported to the United States
in 1989 came from Europe, where they were presumably nursery-grown. All
but 5% of the rest originated in two countries: 27% from Guatemala (4.9
million plants) and 13% from Mexico (2.3 million plants; USDA-APHIS
data compiled by TRAFFIC USA 1992; Table 15.3). Seventy percent of
German bromeliad imports come from Guatemala and Mexico
(TRAFFIC Germany 1988).
Few reports indicate the ratios of imported to propagated plants. Large
nurseries in Guatemala produce an undetermined fraction of that country’s
exports, but Mexico has no comparable facilities. The largest Guatemalan
exporters claim that nearly all of their plants come from culture, although
at least occasionally these same growers receive large shipments of wild
material (W. Rauh, personal communication). Much of the Tillandsia stock
sold in southern California is propagated by two major local growers.
Nursery-grown Tillandsia are more attractive than collected material, but
production costs oblige higher prices.
614
Endangered Bromeliaceae
Table 15.2. Heavily traded
Tillandsia species in the United
Kingdom
T. argentea (5fuchsii)
T. baileyi (presumably pseudobaileyi)
T. brachycaulos
T. butzii
T. caput-medusae
T. ionantha (80% of total sales)
T. ionantha var. scaposa (5kolbii)
T. juncea
T. oaxacana
Source: From Blakesley and Powell
(1992).
Table 15.3. Imports of bromeliads to the United States in 1989a
Exporting country
Countries without
wild bromeliads
Mexico
Guatemala
Other Latin American
countries
Totals
Plants
imported
(millions)
Kilograms
imported
Est. plants
(50 plants kg21)
(millions)b
Total
plants
(millions)
2.114
154 600
7.73
9.84
1.112
1.386
0.455
22948
71041
9 868
1.15
3.55
0.49
2.26
4.94
0.95
5.067
258 457
12.92
17.99
Notes: aUSDA-APHIS data compiled by TRAFFIC USA (1992) and condensed
by author. bAn average weight of 20g was assumed, based on author’s
measurements of the smallest and commonest (T. ionantha at 10g) and the
heaviest (T. caput-medusae at 100 g) species in the trade.
Studies of the impacts of collectors should focus on Guatemala and
Mexico. If only 10% of all wild-collected Tillandsia specimens passed
muster for export, then 72 million plants were taken in these two countries
in 1989 alone, surely enough to represent sizable fractions of several relatively abundant taxa. Indeed, collectors have pushed the populations of
several Guatemalan tillandsias, particularly T. xerographica, close to
extinction (R. Ehlers and L. Kiff, personal communication).
The capacity of bromeliad populations to tolerate sustained commercial
collection remains controversial, but vulnerability surely varies among
In situ conservation
615
taxa. Resilience depends on density, range and potential to regenerate
impacted populations. Most of the heavily marketed species are locally
abundant, wide-ranging and supposedly amenable to sustained heavy
harvest (H. Luther and L. Kiff, personal communication); others disagree
(Read 1989; Rauh 1992). Many dry-growing tillandsias (e.g., T. stricta, T.
recurvifolia, T. streptophylla, T. bulbosa, T. caput-medusae) require on
average 4–6 years to flower from seed in cultivation, and for the exceptionally slow growing types (e.g., T. xiphioides, T. xerographica) this number
probably more closely approaches a full decade (Dimmitt 1984, 1990,
unpublished data). Presumably, poorer nutrition and less continuous water
supplies slow this process in situ.
In situ conservation
Expanding human numbers and activities virtually assure that all but the
most abundant and widely distributed bromeliads will eventually require
protection. Dim prospects for most of tropical America are apparent
almost everywhere (e.g., Ecuador west of the Andes). Parks and other
reserves often fail to protect resident taxa (Stuart 1992). Those Tillandsia
brachyphylla plants described above were stolen from a metropolitan park
in Rio de Janeiro. Losses also occur on a grander scale. For example, Costa
Rica’s logging laws lapsed in the late 1980s, and for six weeks protected
lands were extensively timbered (H. Luther, personal communication).
Illegal logging occurred in Mexico’s Lagos de Monte Azul National Park
during 1988 within view of the superintendent (D. Hadley, personal communication). Such corruption is common, but seldom reported for fear of
retaliation.
Government cooperation does not always guarantee security. Consider
Geohintonia mexicana, a monotypic genus published in 1992. Despite
immediate listing under CITES Appendix I and efforts by the government
to prevent illegal collecting and export, this cactus and sympatric Aztekium
hintonii were commercially available worldwide by 1996. This loss occurred
even though similar events had prompted the authors to withhold the type
locality from the taxonomic description.
Other losses occur without obvious causes. Tillandsia hirtzii is disappearing from its fragmenting Ecuadorian habitats (H. Luther, personal communication), and drought imposed by heightened air circulation and lower
humidity may explain why. Replacement of the formerly rich bromeliad
flora by a much smaller number of weedy species, including cleistogamous
Guzmania nicaraguensis, also suggests deterioration of the remaining
616
Endangered Bromeliaceae
forest. Seedlings of mesophytic bromeliads and orchids no longer inhabit
some of the isolated patches of tropical woodland in Chiapas, Mexico (R.
Ehlers, personal communication) and Ecuador (J. Kent and A. Hirtz, personal communication). Continuing recruitment of xerophytic tillandsias
often contraindicates depletion by collectors given the greater commercial
demand for these more stress-tolerant taxa. Animals also disappear from
dissected habitats at rates inversely proportional to the size of the fragments (Jones and Diamond 1976; Harris 1984).
Establishment of ecological reserves by private foundations provides
some basis for encouragement. The Jatun Sacha Ecological Reserve near
Tena, Ecuador has acquired several thousand hectares of primary forest
with funds from the debt swap program, Conservation International and
the Missouri Botanical Gardens, and a loan from The Nature Conservancy.
Visitors are encouraged to attend classes that emphasize the values of
forests and their products. An adjacent resort for ecotourists is intended to
generate funds to purchase and restore more land. The Los Cedros Project
of the Centro de Investigaciones de Bosques Tropicales is acquiring remnants of upland rainforest in northwestern Ecuador. The Sierra de Alamos,
a large block of deciduous tropical forest in southern Sonora, Mexico, was
designated an international biosphere reserve in 1997. Protecting these
private lands and public forests as development spreads and humans grow
more numerous may prove more difficult than the establishment of such
preserves, but success after the fact is no less crucial to preserve tropical biodiversity (Mlot 1989).
Ex situ conservation
Ex situ (off-site, in cultivation) compared with in situ conservation probably
offers greater promise for endangered Bromeliaceae, but only if priorities
change. Spectacular rescues of a few charismatic megafauna such as the
California condor, peregrine falcon and Arabian oryx attract most of the
public and private funds designated for endangered species. Meanwhile,
tens of thousands of less glamorous taxa approach extinction or disappear
unnoticed. At least 3000 Neotropical plant species have vanished since
1950, and about 100 more become extinct each year (Koopowitz et al.
1994).
Even developed countries tend to be indifferent to their endangered
biota. About 4400 threatened plant taxa occur in the United States, 800 of
which face extinction within a decade (Center for Plant Conservation,
1991; http://www.mobot.org/CPC). Only about 300 are protected by the
Ex situ conservation
617
Endangered Species Act (Federal Register, 15 March 1992), and many of
these listings were obliged by a lawsuit filed by a consortium of conservation agencies that finally overcame years of political resistance. The
Endangered Species Act itself, the only federal vehicle for the protection of
rare life forms, is challenged more vigorously at each reauthorization.
The Center for Plant Conservation (CPC) is devoted to ex situ conservation in the United States, and currently funds botanical gardens to maintain 549 rare taxa. Preservation of all listed flora will require several times
this much money.
Most biota reside in the developing world where governments are least
able to mount effective conservation efforts. The World Conservation
Monitoring Centre of the World Conservation Union (IUCN) lists 20000
species of threatened higher plants, and estimates that better information
from the tropics would triple this number (Heywood 1992). The
Arizona–Sonora Desert Museum has identified a score of narrowly
endemic species in Sonora, Mexico that remain little known to the international conservation community. The Botanic Gardens Conservation
International database of rare plants in conservatories indicates that
dozens of rare tropical taxa are maintained by five or fewer institutions.
Cultivated representatives of most taxa number only a few individuals
(Dimmitt 1989b). Mostly North American and European addresses mitigate against large frost-sensitive collections in the majority of botanical
gardens.
Ex situ bromeliad conservation efforts have also been inadequate. The
Marie Selby Botanical Gardens is one of a few institutions specializing in
epiphytes, and its bromeliad collection is one of the three best in the world,
with about 500 species comprising approximately 20% of the family.
Limited space and funds oblige this institution to restrict its holdings to
three to five clones for most taxa – too little genetic diversity to restore extirpated wild populations. Terrestrial bromeliads are even more poorly represented in botanic gardens and private collections.
If current ex situ conservation efforts are barely adequate to protect a few
thousand species, then the preservation of tens of thousands more within
the next few years seems unlikely. If a third of the world’s approximately
1500 botanic gardens would accept responsibility for 60000 rare taxa, and
if three replicates consisting of 10–50 genets of each taxon are needed for
security, then each garden would have to maintain 360 species totaling 3600
to 18 000 specimens. Such an effort would require resources unavailable to
most botanic gardens. Moreover, adequate public or private funding is
unlikely given the relatively low popularity of botanical gardens among
618
Endangered Bromeliaceae
public institutions. Finally, the basic strategy of most conservation programs – specifically, their emphasis on individual species – is critically
flawed (Hancocks 1994).
Botanic gardens have rarely been stable enough to maintain collections
for more than a few decades; ex situ conservation requires commitments
that simply do not exist. Less than half of the 776 gardens that responded
to a global survey (D. Rae, personal communication) rated conservation
among their top three priorities, and fewer than a third of the gardens in
the United States are working with endangered native plants (B. Ryder,
unpublished survey of 147 gardens). Collections typically change as staff
turns over (Skotak 1989; personal observation). While the bromeliad collection at Marie Selby is expanding, the aroid collection has diminished to
about a quarter of its former size (H. Luther, personal communication),
and a once extensive collection of epiphytic Peperomia species is now represented by fewer than two dozen species. Severe overcrowding is eliminating taxa from the superb bromeliad collection assembled by Warmer Rauh
at the University of Heidelberg (R. Ehlers, personal communication).
Unavoidable mishaps in addition to deliberate actions take their toll on
the best-maintained collections. The Arizona–Sonora Desert Museum lost
at least four nonendangered taxa when an irrigation system broke down,
and from disease and animal depredation despite provisions for comprehensive surveillance (Dimmitt, unpublished data). Hurricanes devastated
numerous botanic gardens and private collections in Florida and Hawaii in
1992; Fairchild Tropical Garden lost 70% of its famous palm collection.
Stable economies and governments exceed even the importance of
effective institutional stewardship for successful plant conservation.
During the Victorian era, English gardens contained over 200 species of
tropical rhododendrons (section Vireya). No more than 12 survived the
First World War (Adams 1981). Undoubtedly, many other cultivated plants
have been lost during wars, economic depressions and other social disruptions. Even labor strikes have exacted a significant toll (Adams 1981).
Recall also that botanic gardens are among the first public institutions to
experience budget cuts during hard times. Economic globalization
increases the chances that belt tightenings will be simultaneous and pervasive.
Endangered taxa could be inexpensively preserved at low temperature,
but at this point not without risk. Cryopreservation is still experimental,
and few taxa have been tested after long-term storage. Genetic drift characteristic of some seed banks may reduce opportunity to maintain viable
populations with this technology (Hamilton 1992).
Conservation laws and their implementation
619
Ex situ conservation will also benefit from contributions from commercial growers and private collectors, some of whom already deserve recognition for major successes. Ginkgo and the dawn redwood, for example, no
longer exist in nature, and we owe their continuance in cultivation to hobbyists. Similarly, a number of Somalian succulents such as Whitesloania
crassa (Asclepiadaceae) and Euphorbia horwoodii (Euphorbiaceae) are
probably extinct except for cultured stock obtained by collectors. Problems
pollinating wild types in cultivation sometimes hinder propagation; again,
it is often the dedicated amateur who develops the required techniques.
Botanical gardens and professionals should actively enlist amateurs to
assist conservation projects, perhaps even support collections, some of
which contain better-documented and maintained material than those
located at some of the most prestigious conservatories.
About 200 notable collections of bromeliads exist in the United States of
which perhaps two dozen are also well documented (H. Luther, personal
communication). Some of their owners also value diversity, and grow many
nonornamental taxa. Global treasures of such high rank could be tied into
a conservation network like those being created by the National Council for
the Conservation of Plants and Gardens (Great Britain) and the North
American Plant Preservation Council, and provisions made for long-term
care as recommended by the Bromeliad Society Code of Conduct (Dimmitt
1987). Other collectors should be encouraged to improve their documentation and join the same network.
Conservation laws and their implementation
CITES (Convention on International Trade in Endangered Species) is the
primary tool for regulating international trade in threatened biota (see
Akeroyd et al. (1994) for a concise summary). Good in theory, the administration of this treaty has created serious impediments for researchers and
conservationists (McMahon 1987; Skotak 1989; see Balistrieri (1993) for a
comprehensive analysis). Attempts by professionals and amateurs to
obtain export permits from most Latin American countries are routinely
thwarted, while unscrupulous business people easily bribe officials to
export large numbers of some of the rarest plants. Legitimate permits,
when obtainable, are too expensive (e.g., US$800 in Mexico in 1991) for
most graduate students and many other investigators.
Problems fostered by CITES and other protective regulations originate
from the highest diplomatic levels down to the practices of the individual
inspector. Germany and Austria proposed to list genus Tillandsia on
620
Endangered Bromeliaceae
Table 15.4. Bromeliad species listed in
Appendix II of CITES, 1992
Tillandsia harrisii
T. kammii
T. kautskyi
T. mauryana
T. sprengeliana
T. sucrei
T. xerographica
Appendix II of CITES at the 1992 convention in Japan; seven taxa were
eventually listed (Table 15.4). Appendix II requires the exporter to obtain
permits from the country of origin testifying that his or her collection did
not threaten the survival of any of the target species. Listing such a large
taxon in its entirety ignores the fact that 95% of Bromeliaceae need no protection.
Horticultural and scientific collection of living material must be encouraged to save endangered taxa. Impediments created by CITES and similar
statutes, however unintended, surely cause losses that could be avoided by
conducting salvage operations during forest clearing. CITES and many
national laws should be amended to ease problems for qualified collectors.
No international statute will protect plants like Vriesea hieroglyphica and
the other Brazilian species cited above from overcollection or destruction.
Although these bromeliads are mass propagated in nurseries elsewhere
(Mercier and Kerbauy 1992), wild material is less costly to obtain in Rio de
Janeiro. No less than national laws in concert with a strong conservation
ethic will mitigate pressures on local endangered flora. There is much work
to be done.
Name index
Abele, L. G. 449
Abendroth, A. 294, 418
Abercrombie, M. 372
Adams, M. 618
Adams, W. W. 57, 139, 141, 142, 154, 172,
182, 383, 499, 502, 561, 570, 575
Akeroyd, J. 619
Alarcón, R. 594, 602
Alcorn, J. B. 588, 594, 598, 602, 603, 604,
605
Alexander, C. P. 449
Allen, M. F. 210
Alves, M. A. 319, 320
Amorim de Freitas, C. 388, 389
Andrade, J. L. 146, 147, 149, 156, 157, 158,
499
Antibus, R. K. 207, 210, 211
Araujo, A. C. 272, 293, 296, 298, 415,
417
Arditti, J. 116
Arizmendi, M. C. 565
Arndt, U. 242
Arnold, F. 231
Arroyo, M. T. K. 515
Arslanian, R. L. 406, 563
Ashtakala, S. S. 517
Atallah, A. M. 406, 563
Augspurger, C. K. 281, 316, 318
Ayensu, E. S. 594, 602, 603
Aziz, T. 210
Bailey, L. H. 587
Baker, H. G. 265
Baker, J. G. 516, 517, 555
Baker, K. 123
Ball, E. 171, 173
Ballistrieri, C. A. 619
Barard, M. A. 424
Barroso, G. M. 367
Barry, D. 346, 362, 399
Barthlott, W. 562, 565
Bartholomew, D. P. 128
Bartioli, C. C. 242
Basham, Y. 212, 213
Baumert, K. 60, 151
Beach, J. H. 276
Beadle, D. 274
Beaman, R. S. 247, 256, 569, 575, 576, 578,
584
Bell, A. D. 38, 39, 41, 42
Bell, C. R. 605
Beltrano, J. 242
Bennett, B. C. 104, 245, 285, 303, 306, 308,
315, 328, 341, 345, 351, 352, 362, 487,
587, 588, 589, 590, 595, 599, 602, 603,
604, 605, 606, 607, 608
Bennett, R. B. 594
Berlin, B. 588, 594, 604, 605
Bermudes, D. 207, 210, 211, 212, 213, 241,
440, 442, 458
Bernardello, L. M. 80, 88, 246, 262, 264,
265, 267, 422, 568
Beutelspacher, C. R. 408, 564
Bhatia, K. 566
Biebl, R. 145, 149, 165, 168
Billings, F. H. 28, 60, 72, 99, 101, 107, 373,
488, 568
Black, C. C. 119
Blakesley, D. 612, 614
Böhme, S. 93, 97, 552, 568, 570
Bokermann, W. C. A. 416
Borchert, R. 560
Boresch, K. 560
Borland, A. M. 108, 124, 129
Borman, M. B. 589
Bradshaw, W. E. 223, 445
Brewbaker, J. C. 277
Brighigna, L. 49, 162, 163, 211, 229, 230,
559
Brokaw, N. V. L. 126, 245, 354, 389
657
658
Name index
Brown, G. K. 63, 79, 80, 92, 93, 94, 95, 96,
97, 238, 246, 350, 262, 267, 385, 436, 488,
489, 490, 491, 492, 496, 508, 509, 512,
513, 514, 516, 522, 529, 531, 532, 549,
551, 552, 555, 565, 566, 568, 570, 571,
574, 575, 577, 578, 579, 580, 581, 582,
583, 585
Brücher, H. 590, 594, 598, 606, 607, 608
Burlage, H. M. 594, 595, 604
Burt, K. 150, 162, 163, 164, 165, 166, 232,
234
Burt-Utley, K. 370
Bush, S. P. 276
Calasans, C. F. 241
Calderon, O. 272
Caldiz, D. O. 242
Calver, F. K. 377
Calvert, A. M. 449
Calvert, P. P. 449
Capen, R. G. 107, 241
Carcuccio, F. T. 241
Carnal, N. W. 119
Catling, P. M. 295, 360, 362, 366, 367, 377,
424, 425, 426
Cave, R. D. 412
Cavelier, J. 270, 388
Cecchi Fiordi, A. 93, 568
Chapin, F. S. 235
Chávez Velásquez, N. A. 594, 603, 604
Cheadle, V. I. 48, 50, 51, 52, 162, 560, 563
Chedier, L. M. 406
Chodat, R. 559
Clark, K. L. 202
Clark, L. G. 489, 522, 523
Clark, T. F. 594, 595, 606
Clark, W. D. 522
Clarkson, D. T. 201, 202
Clegg, M. T. 522
Cobley, L. S. 587
Cockburn, W. 63
Cole, L. C. 239, 326
Collins, J. L. 123
Conacher, A. J. 214
Connor, J. J. 198, 201, 242, 243
Connor-Ogorzaly, M. 606
Cook, M. T. 374, 378
Cornelissen, J. H. C. 356
Cote, F. X. 119
Coutinho, L. M. 12, 107
Covey, S. N. 520
Coxson, D. S. 202, 236
Craighead, F. E. 321
Crayn, D. M. 539
Cronquist, A. 3
Cummins, K. W. 223, 456, 457
Curtis, G. A. 444, 445, 447
Dahle, C. E. 149, 166
Dahlgren, R. 3, 489, 522
Daly, J. 606
Damuth, J. E. 515
Davidson, D. W. 48, 194, 198, 214, 252, 289,
295, 303, 306, 347, 348, 349, 366, 425,
427, 430, 431, 432, 434, 435, 547, 550
Davidson, E. H. 410, 412
Davis, G. L. 99
Davis, J. I. 524
De Santo, A. V. 167, 230
Deiler, F. G. 145, 146, 165, 167, 168
Dejean, A. 294, 342, 423, 426, 427, 428, 429,
430, 433, 437
Delaney, K. 338
DeVries, P. J. 408, 564
Diamond, J. M. 616
Diesel, R. 450
Dimmitt, M. A. 71, 176, 609, 615, 617, 618,
619
Dodson, C. H. 311, 343, 356, 362, 484
Dolzmann, P. 163, 229, 232
Downs, R. J. xi, 3, 11, 69, 70, 74, 79, 88, 92,
96, 98, 102, 247, 275, 299, 300, 301, 463,
464, 469, 488, 493, 504, 509, 514, 516,
517, 526, 528, 529, 530, 546, 549, 555,
559, 560, 561, 562, 563, 568, 569, 573,
579, 580, 581, 583, 584, 594, 599, 610
Duke, J. A. 594, 598, 603, 605
Duvall, M. R. 489, 524
Edwards, P. J. 382, 383
Ehler, N. 230, 562, 565, 566
Ehlers, R. 250, 612, 614, 616, 618
Ekern, P. C. 113, 119, 150, 162
Ellers, B. M. 175
Epstein, W. W. 214, 289, 295, 347, 366, 425,
427, 431, 434, 435
Erdtman, G. 566
Eshbaugh, W. H. 427, 562
Evans, T. M. 63, 92, 529, 531, 566, 580
Fahn, A. 264
Fairbridge, R. W. 515
Farquhar, C. D. 160
Fetene, M. 108, 129, 130, 131, 170, 177, 228,
403
Fialho, R. F. 296, 398
Field, C. 195
Fischer, E. A. 272, 293, 296, 298, 408, 415,
417
Fish, D. 218, 219, 226, 438, 439, 440
Fittkau, E. J. 382
Fogg, G. E. 213
Fontoura, T. 12, 340, 341, 342
Fowler, N. 358, 359, 360, 368
Fragoso, C. 460, 461, 462
Name index
Franco, A. C. 174
Frank, J. H. 219, 225, 412, 438, 439, 440,
442, 444, 445, 447, 448, 449, 454
Franquemont, C. 594, 599, 604, 605, 606
Freeman, C. E. 264, 265, 518
Freeze, C. H. 415
Frei, Sister J. K. 311, 343
Freiberg, M. 364
Friend, D. J. C. 129
Friedman, W. E. 4, 182, 185, 186, 456
Frölich, D. 562
Furch, K. 203
Gadgil, M. D. 327, 328
Galetto, L. 88, 422
Garcia-Franco, J. G. 286, 287, 296, 305,
340, 408
Gardner, C. S. 92, 246, 247, 248, 249, 250,
251, 252, 253, 254, 270, 276, 277, 307,
308, 504, 531, 565, 577, 583, 584
Garth, R. E. 168, 230, 569
Gentry, A. H. 271, 356, 362, 484, 514, 569,
610
Ghosh, I. 488, 491
Gilmartin, A. J. 80, 94, 95, 101, 104, 238,
250, 339, 384, 385, 469, 470, 488, 489,
490, 491, 492, 508, 509, 510, 511, 512,
513, 514, 516, 522, 528, 529, 531, 532,
539, 549, 551, 552, 555, 568, 571, 574,
575, 577, 578, 579, 581, 582, 583, 584, 585
Givnish, T. J. 43, 134, 213, 217, 218, 219,
220, 223, 231, 371, 394, 471, 472, 473,
474, 476, 477, 527, 538, 539, 540
Gladstone, D. E. 341, 362, 365
Goldberg, A. 560, 568
Goldstein, G. 147
Golley, F. B. 382
Gómez, L. D. 464
Gómez, M. A. 198
Gonzales, J. M. 220, 221
Goodspeed, T. H. 594, 606
Gorrez, D. D. 277
Gortan, G. 555, 556, 568, 575, 578, 579,
581, 582, 583, 585
Graham, A. 465, 576
Grant, J. R. 104, 255, 555, 574, 576, 578,
582
Grierson, D. 520
Griffiths, H. 108, 109, 119, 120, 121, 124,
129, 134, 149, 152, 154, 155, 169, 172,
173, 175, 198, 353, 354
Griffiths, N. M. 119
Gross, E. 73, 99, 101, 103, 288, 552, 559,
568, 570, 575, 578, 579, 581, 582, 583,
584, 585
Grubb, P. J. 316, 382, 383
Gschneidner, M. 564
659
Haberlandt, G. F. J. 12, 62, 163, 230
Hadley, G. 377, 615
Halbritter, H. 105, 555, 566, 570, 574, 578,
579, 581, 582, 583, 585
Hall, D. W. 226
Hallé, F. 19, 375, 376
Hallwachs, W. 68, 262
Hamilton, M. B. 618
Hamrick, J. L. 245, 246, 283, 284, 507
Hancocks, D. 618
Hanken, J. 500, 501, 505, 513
Harms, H. 46, 48, 516, 517, 560, 561, 562,
570
Harris, F. S. 136
Harris, J. A. 107, 168
Harris, L. D. 616
Haughton, C. S. 604, 605
Hay, J. D. 397, 398
Hayward, W. 594, 595
Hazen, W. E. 360
Hegnauer, R. 268, 406, 562, 563, 565
Hensyl, W. R. 602
Heslop-Harrison, Y. 569
Hess, M. 566
Heywood, V. H. 617
Hickey, L. J. 3, 4, 19
Hietz, P. 315, 340, 343, 345, 362, 367
Heitz-Siefert, U. 340, 345, 362, 365, 367
Hirtz, A. 616
Hoehne, F. C. 439
Hofstede, G. M. 207
Holcomb, G. E. 242, 339, 377
Holldobler, B. 214
Holst, B. K. 12, 75, 472
Holzapel, C. M. 445
Horres, R. 561
Huber, H. 489, 522, 563, 568
Huxley, C. R. 214, 215, 427
Ibisch, P. L. 341, 364, 365, 368, 469, 483,
484, 486, 487
Ihlenfeldt, H. D. 514
Isley, P. 611
Izquierdo, L. Y. 283
Jaffe, K. 220
Janetzsky, W. 217, 440, 451, 453, 454
Janos, D. P. 210
Janzen, D. H. 433
Jaramillo, M. A. 270, 388
Jebb, M. 427, 428,
Jenkins, D. W. 335
Jensen, A. S. 595
Joel, D. M. 222
Johansson, D. R. 361, 374, 377
Johow, F. 246, 261
Johri, B. M. 568
660
Name index
Jones, H. L. 616
Jordan, C. F. 379
Joyal, E. 589
Judd, W. S. 247, 256, 569, 575, 576, 578, 584
Junk, W. J. 203
Kaiser, W. M. 148
Kaplan, M. A. C. 406
Kato, M. 4
Kellman, M. 204
Kelly, D. L. 357
Kent, J. 616
Kerbauy, G. B. 620
Kernan, C. 358, 359, 360, 368
Kethley, J. B. 223
Kiew, R. 340, 462
Kiff, L. F. 555, 578, 612, 614, 615
Kilpatrick, J. 605
Klein, R. M. 335, 357, 440
Kleinfeldt, S. E. 425
Klinge, H. 382
Kluge, M. 143, 144
Knab, F. 449
Knauft, R. L. 116
Knudsen, J. T. 268
Kohlmann, B. 459
Koide, P. 611
Koniger, M. 128, 177
Koopowitz, H. 610, 611, 616
Koptur, S. 88, 214, 424
Krauss, B. H. 46, 48, 49, 54, 58, 60, 62, 70,
148, 150
Krauss, J. F. 413
Kress, W. J. 253, 282, 479, 517
Krügel, P. 417, 446, 451, 458
Kubisch, F. 270, 271
Kugler, H. 566
Kuntze, C. E. O. 545, 546
Lacerda, L. D. 397, 398
Laessle, A. M. 133, 225, 226, 384, 438, 439,
440, 442, 444, 449, 451, 452
Laferriere, J. E. 594, 599
Landolt, J. C. 211
Lange, O. L. 172
Larcher, W. 383
Lauer, W. 569
Lavelle, P. 459
Lee, D. W. 54, 67, 134, 174, 185, 323, 398,
401, 402, 403
Lefkovitch, L. P. 360, 366
Lehman, P. S. 410
Leme, E. 263, 286, 335, 392, 414, 416, 465,
478, 537, 545, 546, 547, 548, 549, 611
Lesica, P. 207, 210, 211
Levey, D. J. 289, 291
Lindman, C. A. M. 545, 546
Lindsbauer, K. 60, 62
Lindschau, M. 488
Lineham, T. U. 412
Linnerooth, W. 321
Lipp, F. J. 594, 598, 599, 603
Lobry De Bruyn, L. A. 214
Loeschen, V. S. 122, 148, 173
Long, S. P. 179, 228
Longino, J. T. 215, 562
Loope, L. 322
Lopez, L. C. S. 442, 444
Lounibos, L. P. 438, 439, 445, 449
Lowman, M. 321, 406
Lugo, A. E. 459
Luther, H. xi, 14, 54, 245, 247, 256, 260,
346, 356, 396, 424, 516, 545, 546, 549,
555, 611, 612, 613, 615, 618
Lüttge, U. 108, 115, 131, 132, 149, 152, 170,
171, 173, 174, 175, 197, 198, 353, 403
Lydon, J. 129
Lyra, L. T. 440
Mabberley, D. J. 590, 594, 598, 606
Mabry, T. J. 563
MacArthur, R. H. 438
McKey, D. 290, 291, 431
McMahon, L. 619
McVaugh, R. 594, 606
McWilliams, E. L. 52, 98, 104, 108, 133,
136, 277, 316, 338, 449, 483, 492
Maddison, D. R. 535
Maddison, W. P. 535
Madeira, J. A. 443
Madison, M. 98, 102, 213, 276, 295, 347,
422, 424, 435
Maguire, B. 438, 439, 442
Malm, O. 241
Mann, K. 563
Marchant, C. 448, 547
Marigo, L. C. 286, 335, 392, 414, 416, 465
Marks, P. L. 349
Marlatt, R. 413
Martin, A. C. 568
Martin, C. A. 144, 145, 160, 170
Martin, C. E. 11, 57, 62, 107, 109, 114, 115,
116, 118, 120, 124, 130, 134, 136, 139,
141, 142, 143, 144, 149, 154, 162, 166,
167, 169, 172, 175, 182, 230, 351, 354,
383, 499, 502, 561, 562, 570, 575
Martin, G. 68
Martinelli, G. 265, 266, 267, 271, 272, 273,
276, 277, 278
Martinez, J. D. 241, 243
Martinez del Rio, C. 289
Maschwitz, J. 214
Mason, L. 413
Mastalerz, J. 273
Name index
Mateson, T. J. 208, 380, 388, 415, 416
Maxwell, C. 109, 116, 119, 136, 137, 140,
159, 168, 169, 176, 177, 179, 180, 181,
183, 228, 354
Mayo, S. J. 367
Means, D. B. 449
Medina, E. 67, 68, 108, 109, 118, 123, 124,
125, 126, 128, 129, 131, 136, 156, 172,
176, 177, 228, 354, 385, 403, 404, 494,
496, 497, 498, 499, 500, 552, 570, 575
Meirelles, S. T. 57, 139, 141, 145, 499, 502
Melchior, H. 565
Méluzin, S. 605
Mercier, H. 237, 238, 620
Meyer, L. 559, 560
Mez, C. 12, 60, 76, 107, 163, 230, 246, 250,
307, 516, 517, 546, 549, 551, 555, 561, 575
Midgiey, J. J. 208, 209
Miller, A. C. 442
Miller, G. A. 331, 332, 333, 334
Mitchell, P. 267
Mlot, C. 616
Moerman, D. E. 594, 604
Moffat, A. S 202
Montaña, C. 378
Mooney, H. A. 195
Morren, E. 501
Mors, W. B. 595
Morton, J. F. 594, 599, 603, 604, 605
Murawski, D. A. 245, 246, 283, 284, 507
Murillo, R. 461
Nadkarni, N. M. 162, 201, 202, 207, 208,
232, 236, 380, 382, 383, 415, 416, 459
Naeem, S. 442, 456
Napp-Zinn, K. 564
Neales, T. F. 124, 128, 172
Nelson, E. C. 355, 465
Netolitzky, F. 102
Newman, E. I. 201
Newsham, K. K. 209
Nicholas, H. J. 406, 563
Nievola, C. C. 237
Nobel, G. K. 417
Nobel, P. S. 127, 147, 148, 163, 171, 228,
401
Nose, A. 124, 129
Núnez Meléñdez, E. 594, 602, 603, 604
Nyman, L. P. 233
Oberbauer, F. S. 322
Okahara, K. 223
Oliveira, M. G. N. 440, 441, 442
Oliver, W. R. B. 478
Olmsted, I. C. 294, 342, 387, 427, 428, 429,
430, 433, 437
O’Meara, G. F. 219, 444
661
Oppenheimer, J. R. 415
Orivel, J. 434
Ornelas, J. F. 565
Orr, C. 589
Ortiz-Crespo, F. I. 260
Ortlieb, U. 494
Ott, D. 62, 575
Oveido, 598
Owen, T. P. 20, 163, 230, 232, 233, 235
Palací, C. A. 79, 102, 278, 280, 491, 492,
507, 508, 529, 568, 570, 571
Palacio-Vargas, J. G. 460
Palandri, M. R. 93, 568
Paoletti, M. G. 14, 208, 210, 217, 411, 438,
439, 440, 449, 456, 457, 459, 460
Parker, T. 610
Paroz, P. R. 408
Peixoto, O. L. 418
Penfound, W. T. 144, 146, 165, 166, 167, 168
Pennisi, E. 599, 606
Percival, M. S. 264, 265
Pérez-Albeláez, E. 594, 595, 605
Peters, C. M. 62, 340, 562
Pfitsch, W. A. 108, 124, 126, 127, 354, 403
Picado, C. 14, 46, 166, 218, 235, 438, 439,
440
Pittendrigh, C. S. 12, 111, 113, 124, 134,
151, 210, 227, 235, 352, 353, 354, 355,
360, 384, 385, 400, 424, 440, 493, 494,
496, 497, 498, 532, 533, 534, 547, 570, 575
Pizo, M. A. 416
Plummer, G. L. 223
Poisson, M. J. 102
Powell, D. 612, 614
Praglowski, J. 566
Prance, G. T. 514, 570
Pridgeon, A. 165, 230, 234
Primack, R. B. 162, 232
Privat, F. 440
Puente, M. 212, 213
Purseglove, J. W. 594, 595, 598
Raack, J. 273
Rabatin, S. C. 210
Rae, D. 618
Raffauf, R. F. 589, 594, 603
Ramírez, I. 280, 281, 478, 491, 545, 546,
547, 549, 551, 552
Ranker, T. A. 3, 521, 525, 526, 569, 570,
571, 575
Rasmussen, F. N. 489
Rauh, W. 93, 280, 559, 560, 564, 565, 611,
613, 615, 618
Raven, J. A. 123, 240
Read, M. 611, 615
Read, R. W. 449
662
Name index
Redford, K. H. 610
Rees, W. E. 218
Regel, A. von 545
Reinert, F. 57, 119, 139, 141, 145, 499, 502
Reitz, P. R. 355, 357, 444
Reitz, R. 440
Remsen, J. V. 416
Renfrow, A. 47, 67, 109, 134, 141, 150, 151,
188, 193, 194, 198, 203, 204, 205, 216,
225, 233, 242, 303, 349, 350, 353, 432,
494, 496, 497, 532, 570, 575
Richter, P. 417
Rico-Gray, V. 286, 287, 305, 408, 428
Rivero, J. A. 417, 424
Rizzini, C. T. 595
Robins, R. J. 438
Robinson, H. 70
Robinson, J. W. 241
Rocha, C. F. D. 319
Roe, N. A. 218
Röhweder, O. 103
Rojas-Fernández, P. 460, 461, 462
Rossi, M. R. 480, 482
Rowe, J. H. 602
Rudolf, D. 343
Ruess, B. R. 175
Ruinen, J. 374
Ruschi, A. 246
Ryder, B. 618
Sakai, W. S. 74, 163, 227, 231, 400, 493
Sale, P. J. M. 124, 172
Sanford, W. G. 74, 163, 227, 231, 400, 493
Sanderson, J. 163
Sazima, I. 246, 258, 267, 268
Sazima, M. 256
Scarano, F. R. 367, 388, 389
Scatina, F. N. 459
Schaffer, W. M. 327, 328
Schill, R. 566, 568, 575, 578, 579, 581, 582,
583, 585
Schimper, A. F. W. 12, 111, 351, 493, 497,
532, 559, 575
Schindler, R. 560
Schlesinger, W. J. 349
Schmid, M. J. 464
Schmid, R. 464
Schmidt, A. K. 144
Schmidt, C. 612
Schmidt, J. 148
Schmidt, R. 93
Schmitt, A. K. 166, 167, 230
Schrimpff, E. 241
Schroeder, H. A. 243
Schubart, C. D. 450
Schuh, M. 450
Schulte, P. L. 148
Schultes, R. E. 589, 594, 603
Schulz, E. 137, 499, 501, 502
Schulze, E. D. 208
Schürhoff, P. N. 568
Scogin, R. 264, 265, 518
Seemann, J. 207, 374, 378, 380, 381, 399
Seidel, J. L. 289, 295, 347, 435, 550
Sengupta, B. 211
Schacklette, H. T. 198, 201, 242, 243
Sharkey, T. D. 160
Sharma, A. K. 488, 491
Sheline, J. R. 243
Shivanna, K. R. 569
Shubert, T. S. 242
Sideris, C. P. 148, 150
Sieber, J. 113, 162, 232
Siedow, J. N. 118, 144, 145, 160
Sieff, E. xi, 14, 247, 516, 545, 555
Silander, J. A. 331
Sillett, T. S. 415
Simpson, B. B. 606
Simpson, M. G. 524
Skotak, C. 611, 618, 619
Smith, A. P. 126, 127
Smith, J. A. C. 108, 109, 124, 129, 131, 134,
135, 138, 151, 152, 154, 155, 157, 168,
353, 354, 494, 495, 497
Smith, L. B. xi, 3, 11, 70, 74, 79, 92, 96, 98,
102, 247, 278, 403, 463, 464, 466, 467,
469, 479, 481, 482, 488, 493, 504, 505,
509, 514, 516, 517, 522, 525, 528, 529,
530, 546, 555, 561, 568, 569, 573, 575,
578, 579, 580, 581, 583, 584, 585, 594,
599, 610
Snow, B. K. 255, 290
Snow, D. W. 255, 290
Soltis, D. E. 253, 281, 507, 577
Soukup, J. 589, 594, 602, 603, 604
Spencer, M. A. 247, 479, 517, 555, 573, 578,
585
Stearns, S. C. 326
Steele, A. R. 594, 604
Stephenson, S. C. 211
Sternberg, L. 125
Stewart, G. R. 208, 209
Steyermark, J. A. 466
Stiles, E. W. 289
Stiles, F. G. 246, 265, 271, 272, 276, 299, 416
Stiles, K. C. 149, 169, 292
Stock, W. D. 208, 209
Stotz, D. F. 254
Strehl, T. 70, 559, 562
Strehl, V. T. 53, 242
Stuart, G. E. 615
Subils, R. 568
Suessenguth, K. 568
Sugden, A. M. 369, 370, 438
Name index
Sun, G. 3
Szidat, L. 99, 102, 103
Tanner, E. V. J. 382, 383
Taylor, D. W. 3, 4, 19, 149
Ter Steege, H. 356
Terry, R. G. 3, 79, 80, 96, 97, 463, 466, 496,
516, 522, 527, 528, 529, 531, 538, 540,
552, 569, 570, 571
Thien, L. B. 428
Thomas, V. 159, 412, 458
Thompson, J. N. 217, 222
Thomson, W. W. 163, 232, 233
Thorne, B. L. 436
Thornhill, A. 611
Tietze, M. 111, 493, 496, 497, 498
Till, W. 250, 491, 492, 496, 505, 506, 555,
564, 565, 569, 571, 573, 577
Ting, I. P. 115
Todzia, C. 346
Tollsten, L. 268
Tomlinson, P. B. 20, 24, 25, 26, 29, 32, 37,
39, 41, 42, 59, 60, 61, 62, 63, 145, 162,
238, 499, 501, 506, 559, 560, 561, 562,
563
Towle, M. A. 594, 605
Troughton, S. 109, 156
Tukey, H. B. 348
Turner, R. M. 316
Ueno, C. 97, 568
Ule, E. 295, 347, 435, 546, 550
Ulubelen, A. 563
Usher, G. 594, 604
Utley, J. F. 255, 267, 371, 530, 531, 555
Valdivia, P. E. 340
Van Sluys, M. 254
Vance, E. D. 207, 208, 236
Varadarajan, G. S. 68, 69, 93, 95, 97, 101,
104, 246, 262, 267, 400, 467, 468, 469,
470, 526, 539
Vareschi, E. 217, 440, 451, 453, 454
Vasak, V. 299
663
Veloso, H. P. 355, 357, 361
Vijayaraghavan, M. R. 566
Visher, W. 559
Vogel, S. 246, 253, 255, 565
Vogelman, T. C. 68
von Reis, S. 594, 598, 599, 603
von Reis Altchul, S. 594, 598, 599, 603, 604
Wake, D. B. 420, 500, 501, 505, 513
Walker, L. R. 321, 323
Wanderly, M. 566
Weir, J. S. 340, 426
Weiss, H. E. 488
Weyl, R. 576
Wheeler, W. M. 217, 218, 425, 430
Wherry, E. T. 107, 241
Wiley, E. O. 481
Williams, C. A. 406, 518, 564
Williams, R. O. 608
Wilson, E. O. 425, 438, 595, 605
Winchester, J. W. 243
Winkler, S. 70, 198, 479, 494, 559, 562, 569,
570, 575, 576, 584
Wittmack, L. 555, 559
Wolf, K. H. 524
Wollenweber, E. 563
Wright, J. S. 272
Wrisley, B. 589
Wülfinghoff, R. 270
Wunderlin, R. P. 608
Wurthmann, E. 335
Yeaton, R. I. 341, 362, 365
Young, A. M. 418
Yu, W. 432, 433
Zahl, P. A. 438
Zavortink, T. J. 440
Ziereis, H. 231
Zimmerman, J. K. 342, 387
Zizka, G. 355, 465
Zoller, W. H. 243
Zotz, G. 141, 146, 149, 156, 157, 158, 159,
356, 359, 458, 499
Subject index
Abscission (see Foliage; Water relations)
Acetylene 275
Africa 1, 331, 361, 465
Air quality monitors 61, 107, 187–188, 192,
201, 231, 240–244, 459
Air pollution (see also Global change) 188,
413
Alajuela Province 464
Algae 439–442, 444–445
Allelopathy 343, 349, 377
Allozymes 281–285, 338, 577
Alpine bromeliads (see also Andes) 6–8, 11,
41, 45, 73, 110, 131, 147–148, 331–334,
390, 399–400, 595, 600–601
Amazonia 241, 339, 347, 427, 435, 440, 446,
451, 458, 471, 479–480, 483, 485, 487,
515, 545–547, 598
Ancestral habitats (see also Heterochrony)
228, 493–500
Andes 6, 41, 43, 54, 218, 256, 301, 316, 319,
339, 357, 393, 395, 399–400, 466–471,
480–486, 505, 548, 550, 569, 577, 581,
585, 599, 602, 607, 610, 615
Animal-assisted saprophytism (see also
Mineral nutrition; Phytotelmata) 53,
184, 199, 223–227, 235, 438
Antarctica 515
Antilles 569, 582–583, 585
Anthocyanins 254
attract fauna 86, 89
enhance carbon gain 185–186
protect tank fauna 54–55, 413, 454–456
sunscreen 60, 134, 182, 404
Ants (see also Myrmecodomatium) 413,
421–435
ant gardens 86, 88, 53–54, 102, 113, 187,
189, 191, 199–200, 205, 208, 213–216,
222, 231, 235–236, 238, 276, 295, 347,
361, 407, 424–426, 432–435
ant guards 86, 340, 422–424, 433
ant-house bromeliads 21, 23, 53, 96, 187,
189, 199, 213–216, 218, 222, 231, 357,
369, 371, 407, 423, 474–477, 562
carton 206, 366–367, 407, 424–425
defense of trees hosting ant-house
bromeliads 340, 429
evolution of ant/plant associations
431–435
myrmecochory 102, 104, 200, 214, 223,
245, 289, 295–296, 347–348, 365–366,
433, 550
prey of Brocchinia reducta 220
removing bromeliads from trees 340
Apomixis 491
Aquatic Bromeliaceae 110, 388–389, 392, 397
Archbold Biological Station 338
Argentina 242, 262, 390, 399, 416, 468–471,
483, 505, 513, 579, 589, 599, 609
Arizona–Sonora Desert Museum 618
Aroids 48, 98, 205, 211, 357–360, 366, 367,
484
Asexual reproduction 30–34
from spent infructescences 30, 279, 323,
325, 574
types/locations of offshoots 324–325
Atacama 325, 395, 399, 515–516, 602, 609
Atlantic Forest 10, 255, 265, 271–273, 279,
320, 340, 355, 357, 367, 371, 388, 397,
416, 418, 478–479
“Atmospherics” 12
Australia 220, 408
Austria 619
Bahamas 398
Bahia State 7, 9–10, 320, 330–331, 340, 363,
367, 390, 408–409, 416, 419, 479, 551
Baja California 212, 246, 362, 399
Barra de Marica restinga 397–398
Barro Colorado island 159, 272, 283, 325,
389
665
666
Subject index
Belize 360, 367, 392, 424–425, 581
Benzothiazole 295, 347
Bermuda 480
Beta-hydroxyethyldrazine 275
Big Cypress National Preserve 308, 312
Big Pine Key 346
Big Thicket National Preserve 413
Biogeochemical cycling 378–384
Brazil 7, 9–10, 12, 14, 157, 178, 198, 208,
213, 218, 241, 254–257, 259, 265–266,
272–279, 284, 293, 296, 316, 319–321,
330–331, 335–336, 344, 363, 367,
387–392, 394–395, 398–399, 410, 416,
436, 456, 465–466, 478, 486, 504, 545,
569, 579, 582, 585, 598, 606
Brazilian Shield 390
Breeding systems 86, 245, 253, 276–280,
306, 338
allogamy 250, 253, 256, 282, 508, 549
andromonoecy 264, 491, 552
autogamy 86, 89, 97, 250, 265, 276–277,
283, 549, 577
cleistogamy 246, 250, 277, 491–492, 577,
615
dioecy 83, 85, 92–93, 95, 278–280
self-incompatibility 265, 276–277
protandry 276, 565
protogyny 252, 276
Bolivia 14, 335, 341, 399, 469, 485, 507, 513,
579, 583, 599
British West Indies 436–437
Bromelain 602
Bromeliad Society 619
Bryophytes 166, 345, 380, 414, 439
Caatinga 10, 226, 320, 551
Cacti 50, 98, 290–291, 316, 365, 395, 615
California 612–613, 616
Campos de altitude 335, 479
Campos rupestres 7, 10, 260, 299, 319–321,
351, 390–391, 436, 467, 479–480
Caribbean 321, 393, 398, 414
Virgin Islands 442–444, 577, 608
Carnivory 11, 23, 46–47, 59, 75, 133–134,
187–190, 199, 208, 217–226, 231, 233,
235, 367, 371, 373, 395, 438, 450,
474–478, 497
Brocchinia reducta 219–222
Catopsis berteroniana 218–219
identity of prey 220–221
Puya raimondii 218
Central America 278–280, 335, 340, 440,
569, 576, 607, 610
Cerrado 264–267
Cerro Neblina 7, 419, 439, 467
Chapada Dimontina 391
Chemical control of epiphytic Bromeliaceae
242
Chemical defenses 196, 406
Chiapas State 278, 340, 611, 616
Chile 6, 331, 334, 390, 399, 468, 589
Chloroplast
chlorophyll content in foliage relative to
exposure 140, 176, 181
chlorophyll fluorescence 107, 177–181
genome 1, 30, 519–521
ndhF gene 522–524
rbcL gene 522
structure relative to shade adaptation 177
Chóco 247, 356, 392, 599
Chromosomes 252, 263, 488–492, 507, 547,
551–552, 571, 577
aneuploidy/polyploidy 252–253, 282,
488–492, 552, 577
Cladogenesis 8, 248, 250
effects of climate 514–516
reticulate evolution 488–492
role of pollinators 246–264
role of substrates 306–308, 484–488
vicariance 366, 369–371, 383, 394,
399–400, 465–482
Clonal growth (see also Genetic structure of
populations) 283, 323, 389, 547–548, 551
Cloud forest 75, 182, 207, 438, 585
Cohesion ratio 481–482, 484
Colombia 12, 207, 247, 278, 356, 369–370,
388, 392, 396, 416, 438, 466–467, 485,
487
Commensalism 223
Competition, competitive exclusion,
concurrence 313, 359–360, 378, 380,
389, 391
Corcovado Basin 358–360
Corm-like rhizomes 47
Costa Rica 12, 69, 126, 201–202, 207–208,
210–211, 235, 262, 271–272, 276–278,
299, 316–319, 340, 358, 360, 364–365,
368, 370–371, 382, 388, 415–416, 418,
420, 445, 462, 480, 610, 615
Crassulacean acid metabolism (CAM) 6,
11–12, 45–46, 62–63, 65, 67, 108–109,
112–123, 227
adaptive response to stress 168–169
anatomy of CAM foliage 401
CAM cycling 115, 131, 136, 170
CO2 recycling/CAM idling 115, 117, 119,
122, 131, 169–174
evolution of CAM from C3 ancestry 115,
136, 494–500, 538–540
facultative CAM 121–122, 136–137, 156,
356
involvement in hydration 174–175
nature of reserves used to energize dark
acidification 173
performance of CAM vs. C3–CAM types
in situ 121, 228
Subject index
performance of C3 vs. CAM types in situ
120, 151–160, 354–355, 383, 389
relative to exposure to SO2 and O3 244
role of citric acid 174
temperature optima 120, 128–129,
170–171
Cuticle 149, 174, 190, 218–219, 224, 230,
352, 371
Cyanobacteria 211–213, 440, 442
Demography 245, 308–319, 368, 396
catastrophic mortality 319–323
recruitment 308–312, 316–317
survivorship 312–319, 368
Denitrification 458
Detritivores (see also Animal-assisted
saprophytism) 55, 207–208, 430
Dichogamy 276
2,4-dichlorophenoxyacetic acid 275
Distribution (in space) 465–466
Brocchinia 471–479
Bromelioideae 479–480
effects of climate 107–186, 482–485
influence of plant characteristics 151,
369–373, 482–488
in tree crowns 341, 361
other patterns for epiphytes 358–360
Pitcairnioideae 466–479
Puya 468
regional patterns 357
Tillandsioideae 480–482
vertical stratification in forests 341,
351–358, 360–362
Deuterium 125–126
Ecological types (Pittendrigh’s) 8–11,
227–228
comparisons with Benzing’s five types,
111–113
Type One 130–132
Type Two 123–130, 227–228
Type Three 132–133
Type Four 133–142
Type Five 143–145
Ecuador 7, 12, 205–206, 210–212, 316, 323,
331–334, 339, 343, 356–357, 364, 384,
407, 422, 424, 466, 484–487, 509–510,
547–548, 550, 590, 602, 606, 610,
615–616
El Niño 175, 360, 514–515
El Salvador 278–280, 610
Endangered bromeliads
conservation laws 619–620
Convention on International Trade in
Endangered Species (CITES)
619–620
Endangered Species Act 617
ex situ conservation 616–619
667
factors threatening populations 610–615,
620
in situ conservation 615–616
model for rate of extirpation 610–611
most heavily traded species 613–614
species listed in Appendix II of CITES
620
World Conservation Monitoring Center
of the World Conservation Union
(IUCN) 617
Epiparasitism 373, 379
Epiphytism 7–8, 14, 21, 28, 41, 43, 47, 49,
58, 63, 102, 384, 387–389
accidental types 387
bark vs. rock as substrates 305–308, 328,
344, 385, 395
effects on phorophytes 344, 372–382
facultative types 386–389
host specificity 339–351
inducement for speciation 482–488
life history of Tillandsia paucifolia
308–317
occurrence in family 385–386
partitionment of tree crowns 356–362,
365–366
relative to breeding system 276
role in succession 362–368
survival in hurricanes 321–323
vertical distribution in forests 341,
351–358
Epiphytosis 374
Eocene 464, 524
Espirito Santo State 7, 254, 335, 414, 419,
551
Ethylene 275
Europe 612, 617
Everglades National Park 321
Evolutionary relationships (see also
Ancestral habitats; Habits; Nectaries;
Trichomes)
Brocchinia 471–475
Bromeliaceae vs. other monocots 2,
522–527, 540
Bromelioideae 536–538
fruit types 536
habits among Bromeliaceae 42–48, 513
mesic vs. xeric habits in Tillandsioideae
509–516, 531–532, 570
ovary positions 535
Pitcairnioideae 538–540
Pittendrigh’s four ecological types
532–534
seed types 537
subfamilies within Bromeliaceae
521–527
Tillandsioideae 247, 257, 527–535,
575–578
trichomes 70–72, 77, 475–478, 493–500
668
Subject index
Fairchild Tropical Gardens 618
Fauna (see also Ants; Frugivores;
Pollination; Seed dispersal; Tables 8.1,
8.2)
amphipods 208, 457
Aranea 430
Ascaridea 430
bats 75, 88, 256, 260, 456
Chilopoda 430, 458
Coleoptera 208, 340, 429, 457
Collembolla 208, 430, 460
copepods 443–444
crabs 408, 449–450
detritivores 223, 226, 456–462
Diplopoda 430
Diptera (unspecified) 430, 446, 457
earthworms 421, 446, 449, 460–462
fauna in phytotelmata of Venezuelan
bromeliads 411
frogs 227, 296, 398, 417, 419, 446, 450,
456, 599, 606
guinea pig 288, 601
Homoptera 214–215, 223, 408–409, 422,
424, 429, 431
hummingbirds 252, 255–256, 261, 267,
415–416
isopods 208, 430, 449, 457
leaf miners 409
Lepidoptera 262, 408, 430, 564
lizards 418
marsupials 296, 415
mayflies 457
midges 440, 442–444, 457
mites 208, 460
mollusks 410, 458
mosquitoes 421, 439, 441–449, 458
nematodes 410
nonhummingbird birds 261, 265, 271,
284, 290, 399, 415
Odonata 419, 430, 442, 446, 449–450,
452, 454
Orthoptera 406
ostracods 439, 442, 444
peccaries 389
pests on imported bromeliads and
countries of origin 410
Phalangidae 430
primates 406, 414–415, 599–600
protozoa 444
rodents 228, 296, 389, 415, 601
rotifers 442–444
salamanders 420–421
Salatoria 446
scorpions 458
snakes 418
spectacled bear 218, 599
symphylids 408
syrphids 449
termites 214, 319, 407–408, 430, 436–437
Thysanura 430
wasps 221, 267
Ferns 166, 208, 211, 214, 357, 360, 364–367,
383
Fiber production 323
Fire: tolerance and effects 21, 43, 319–321,
390–392, 401, 475, 480, 600, 602, 611
Florida 7, 9–10, 12, 107, 195, 203, 207, 218,
241–243, 253, 259, 273–274, 278–279,
282, 285, 303, 307–318, 321–323, 326,
328, 335–338, 343–346, 349–356, 362,
377–382, 396, 408, 412, 424, 432,
447–448, 454, 588, 595, 599, 608, 618
Flowers and flowering (see also
Inflorescence; Nectaries; Pollination)
31, 47, 89–98, 249, 549
androecium 91–93, 94, 96–97, 249, 253,
529, 552, 566, 574
calyx 87, 90–91, 294–297
corolla (see also Flowers) 91, 97
evolution (see Cladogenesis)
fragrances 224, 251, 254–255, 263–264,
268, 552, 565, 574
Gardner’s five floral types in Tillandsia
subgenus Tillandsia 249, 251–254,
583–584
gynoecium 91, 94, 574
induction of flowering 272–276
petal scales 94, 96–98, 247, 262, 516, 545,
549, 565, 571, 574
phenology 267–276
Racinaea 585
rewards (see also Nectaries and nectar)
264–298
stigma morphology 80, 92, 94–96, 262,
556, 568, 574–576
synchronization 269–273, 280–281,
316–317
Tillandsia subgenus Allardtia 578
Tillandsia subgenus Anoplophytum 579
Tillandsia subgenus Diaphoranthema
581–582
Tillandsia subgenus Phytarrhiza 580–581
Tillandsia subgenus Pseudoalcantarea
584
Tillandsia subgenus Tillandsia 582–583
Foliage
absorptive function 49
deciduousness 31, 45, 52, 57, 59, 132, 160,
169
life history 58–59, 176
morphology/anatomy 29, 52–54, 59–75,
184, 561–564
optical properties 66–70
organization of mesophyll 65–70
Subject index
pigmentation 32–33, 35, 37–38, 54–56,
60, 182–186
Foraging for resources through differential
growth 36–42
Fossil bromeliads 1, 3, 5, 464–465, 576
France 355
French Guinea 434
Frost-hardiness 8, 13, 43, 110, 131, 147–148,
261, 316, 331–339, 352, 390
effects on geographic ranges 334–339, 362
Fruits
composition of fleshy types 291–292
fruit flags 86, 263
fruit set 268
phenology of ripening 293
structure 87–90, 98–105, 292
Frugivores 91, 136, 288–289, 293–299,
346–348, 359, 366
Fungi (see also Mycorrhizas) 88, 214, 377,
379–380, 430, 435
Galapagos Islands 480
Gallery forest 260, 390
Genetic structure of populations 253,
281–284, 507–508, 609
Germany 612–613, 619
Germination 49, 99, 104, 259, 294, 301, 311,
315, 345–346
Geologic history of Bromeliaceae (see also
Fossils) 463
Georgia 338
Geotropisms
roots 132, 400, 560
stems 560
Gesneriads 205, 366, 426, 456
Glaciation 515
Global change 107, 202, 459
Gnetophytes 4, 115
Goiás State 551
Gran Sabana 220, 222, 281
Great Lakes of North America 362
Guadeloupe 595
Guana Island 436
Guanacaste Province 365
Guatemala 198, 280, 366, 581, 613, 615
Guayanan Shield (Highlands), Guayana 6,
14, 190, 199, 219, 258, 260, 288, 319,
357, 386, 390–391, 393–394, 438–439,
466–478, 483, 570
Guttation 87
Habits, vegetative (see also Clonal growth;
Ecological types; Heterochrony) 19–35,
42–48, 133–134, 238–240
economic analysis 217, 301–305, 371–373
evolution 42–48, 513
organization for foraging 36–42
669
Haiti 203
Halophytes (salt-tolerance) 7, 197–198,
401–404
Hawaii 331, 598, 618
Hemiepiphyte 11, 30–31, 34, 45, 47, 353, 386
Herbivory/herbivores (see also Fauna) 28,
55, 70, 75, 88–89, 184, 215, 223,
405–414, 422, 429
Herkogamy 276
Heterochrony (see also Ancestral habitats)
6, 20, 24–25, 28, 43–46, 48, 57, 81, 83,
85, 89, 136–142, 238–240, 250,
238–239, 463, 492, 500–508, 527, 571
Heterophylly 6, 8, 21, 25, 31, 34, 44–45,
56–58, 136–142, 160, 358, 499, 501–502
Hispanola 584
Holocene 338, 397, 480
Homoplasy 67, 79, 85, 97, 102, 391, 500,
504–506, 514, 517, 526, 535, 571, 575
Honduras 204, 605
Honeydew 214, 425
Host decline (epiphytosis) 372–382
Host preferences for epiphytes 308–312,
339–351
effects of bark 343–346
effects of seed dispersers 346–348
roles of nutrients and light 348–351
Human disease 440
Humboldt current 515
Hurricanes 308, 321–323, 619
Hybridization 247–248, 252, 488–492, 587
Indigenous people 588–590
indigenous management 607–608
indigenous taxonomy 588–589
Indole acetic acid 275
Inflorescence/infructescence
anatomy of axis 561
development 88–89
frost-tolerance 332–334
organization 81–89, 257–259, 263–264,
267, 305, 548–549, 564
order of flowering 270–271
perennial types 303, 548
pseudanthium 81, 83
Inselberg 10, 286, 390, 393, 487, 507
Iteroparity 245–245, 250
Jamaica 107, 196, 357, 384, 393–394, 417,
440, 442, 450–454
Jatun Sacha Ecological Reserve 616
Jurassic 1
Kukenan-tepui 221
Lagos de Monte Azul National Park 615
Lake Gatun 356
670
Subject index
La Selva 207, 211, 416
Lichens 345
Life history analysis (see also Demography;
Reproductive allocation) 301–319
monocarpy vs. polycarpy 326–328
saxicoles vs. epiphytes 305–307, 328, 344,
492
Limonene 295
Lithophytes (see Saxicoles)
Loja Province 356
Louisiana 166, 242, 339, 413
Malaysia 340, 426
Malthusian coefficient 326, 504
Mangroves 7, 198, 345
Marie Selby Botanical Gardens 270, 548,
617–618
Mesoamerica 14, 253, 255–256, 285, 393,
420, 479, 583, 585
Methyl-5-substituted phenyl derivatives 295
Methyl-6-methylsalicylate (6-MMS) 295,
347, 435, 550
Mexico 7, 9, 14, 198, 250, 252–253, 264,
270, 276, 278, 283, 286, 296, 305–306,
315, 335, 340–342, 357, 365, 367, 378,
387, 390, 393, 398, 412, 420, 423, 427,
460–462, 471, 483, 584, 598, 604,
610–611, 613–614
Microbes 209–213, 223–224, 232, 235, 345,
439, 451–452, 456–458
Mimicry 222, 347, 376, 435, 550
Minas Gerais State 7, 279, 320, 331,
335–336, 390, 393, 396, 407–410, 427,
436, 479, 498, 551
Mineral nutrition (see also Ants) 64, 110, 160
absorption 193
additions of nutrients to soil 398
assistance from microbes 209–213
critical concentrations of nutrients 196
effects of epiphytes on the
biogeochemistry of hosting ecosystems
207, 223, 382–384
involving phytotelmata (see also Animalassisted saprophytism) 111–118, 189,
216–228
mineral-use efficiency (MUE) 128, 191,
195–197, 238, 383–384
mobilization from spent ramets 47–48
modes of nutrition in Brocchinia 472
myrmecotrophy (see also Ants) 230, 235,
238
nitrate reductase 237–238
nitrification 207
nitrogen as a tracer 208–209
nitrogen fixation (nitrogenase) 187, 200,
205, 208–209, 211–213, 226, 440, 442,
459
nitrogen in leaves relative to sun exposure
125, 228, 349–350, 401–404
nitrogen nutrition 58, 110, 116, 191,
195–196, 205, 208–209, 211–213, 226,
235–238, 385, 401
nitrogen-use efficiency (PPNUE) 128,
130–131, 195–197, 372
nutrients from the atmosphere 201–205,
208, 348–351, 377–384
nutrients in bark and arboreal rooting
media 205–207, 345, 380
nutrients in the phytotelma of Guzmania
monostachia 204
nutrients in terrestrial soils 380–382, 391,
394
nutrients in tissues 192–193, 195, 228,
232, 240–244, 348–350, 380
nutritional modes of Bromeliaceae 200
oligotrophs vs. eutrophs 8, 197, 199, 202,
244
plant architecture as it relates to nutrient
economy 238–240
seedling nutrition 236–238
supply vs. demand 188–197
uptake via roots vs. shoots 162, 232
Miocene 515
Mistletoes 291–291, 343
Molecular systematics 79
Molecular clocks 518
Monocarpy 24–25, 43, 47, 81, 88, 245, 250,
257, 259, 261, 276–277, 281, 285, 287,
308, 319, 323, 395, 412, 560
monocarpy vs. polycarpy (iteroparity)
316–319, 326–329
size of shoot at flowering 317–318
Monteverde 388, 415
Mosaic evolution 516
Mutualisms and other relationships (see
also Ants; Fauna; Mycorrhizas;
Phytotelmata; Pollination; Seed
dispersal)
ants 421–435
birds 415–417
frogs 417–419
mammals 414–415
salamanders 420
termites 436–437
to assist nutrition 223–227
Mycorrhizas 34, 209–211, 374
Myrmecochory (see Ants)
Myrmecodomatium 422
Myrmecotrophy (see Ants)
1-naphthalene acetic acid 275
Naturalization 355, 465
Nectaries and nectar (see also Ants;
Pollination) 97, 408
Subject index
evolution of the floral types 93
extrafloral nectaries 84, 86, 88, 224, 228,
233, 235–238, 408, 422–424
nectar composition 262, 264–267, 422, 568
timing of secretion 254–255
Neoteny (see Heterochrony)
Netherlands 612
Nicaragua 278
Nitrate reductase (see Mineral nutrition)
Nitrogen fixation (see Mineral nutrition)
North Carolina 612
Nutritional piracy 378–382
Ohio 273, 277
Orchids 48, 208, 211, 270, 323, 338,
341–343, 357, 360, 364–368, 374, 377,
396, 426, 428–429, 449, 485, 610
Organ mountains 255
Ortho-vanillyl alcohol 295
Osa peninsula 358
Osmoregulation, osmotic adjustment 107,
149, 157–158, 175
Ovules 92, 99–100, 104, 568, 574–575
Pacific Ocean 346
Paleoclimate 400, 460, 467, 513–516,
569–570, 576
Panama 126, 128, 156, 177, 203, 278, 280,
284, 354, 357, 359, 389, 507, 598
Pantepui 219, 394
Papua New Guinea 428
Parabiosis 430
Paraguay 513, 598, 607, 610
Paramo (see Alpine bromeliads; Andes)
Paraná State 336, 598
Pathogens (see also Human disease) 70, 132,
312, 376–377, 405–414, 429, 437
Parasitism 187, 343, 373–380, 435
Pearl bodies 422
Periderm 46
Peru 6, 12, 14, 174, 214, 295, 325, 347, 365,
393–396, 406, 416, 424, 435, 446, 451,
458, 469, 471, 483–488, 510, 514, 545,
547–548, 550, 569, 579, 583, 588,
600–601, 605, 611
Phloem 48, 50, 66, 378, 560, 609
Photoinhibition (see Photosynthesis)
Photoperiodism 28, 128, 272–276
Photorespiration (see Photosynthesis)
Photosynthesis (see also Anthocyanins;
Mineral nutrition; Water relations)
C4 pathway 55, 114, 117, 119–120, 122,
141, 184, 228
distribution of C3 and CAM taxa in
Bromeliaceae 108–109, 118
ecological correlates of the three
photosynthetic pathways 120–123
671
evolutionary considerations (see also
Ancestral habitats) 493–500
exposure to high light incl.
photoinhibition, photorespiration, and
photoprotection 66–70, 116–119, 150,
159, 168, 176–186, 228, 398, 401–404
light quality 67
optical properties of mesophyll 66–70
pathway relative to life stage 57, 136, 142
photosynthetic capacity relative to N
supply 170–172, 195
Pittendrigh’s three exposure types
352–354
quantum yields 133, 179, 185, 354, 497
relative to dispersal mode 298, 351–359,
401–404
sun and shade tolerances and
acclimatization 21, 52, 54, 64, 66–70,
72, 76, 123–130, 132, 134–137, 143,
154, 176–186, 228, 328, 351–358, 388
sun flecks 67, 116, 168, 185
Phyllotaxis (see also Habits) 25–28
Phylogenetic constraints 257
Phylogenies and cladograms
Brocchinia 473–474
Bromeliaceae relative to other monocots
523
Bromelioideae 538
CAM vs. C3 lineages in Bromeliaceae 495
fruit types in Bromeliaceae 536
ovary positions in Bromeliaceae 535
Pitcairnioideae 470
Pittendrigh’s four ecological types
533–534
seed morphology in Bromeliaceae 537
subfamilies within Bromeliaceae 521, 525
subgenera of Tillandsia/Vriesea 509–510
Tillandsia subgenus Phytarrhiza 511–512
Tillandsioideae 528, 530
xeric vs. mesic habits in Tillandsia
subgenus Phytarrhiza 511–512
xeric vs. mesic habits in Tillandsioideae
532
Phytogeography 1–4, 5, 12–14, 465–488,
609–610
Brocchinia 471–478
Bromelioideae 478–480
Pitcairnioideae 466–478
Racinaea 585
Tillandsia subgenus Allardtia 579
Tillandsia subgenus Anoplophytum 579
Tillandsia subgenus Diaphoranthema 582
Tillandsia subgenus Phytarrhiza 581
Tillandsia subgenus Pseudoalcantarea 584
Tillandsia subgenus Tillandsia 583
Tillandsioideae 480–482, 569–571,
576–577
672
Subject index
Phytotelmata 14, 19, 49, 53, 55–56, 67, 74,
90, 110, 122–123, 132–133, 149, 186,
220, 232, 354
adaptations and fidelities of residents
444–450
litter processing 207–208, 223, 456–459
nutrient supply for plant 113, 204,
219–229, 438
plant-provided benefits to symbiotic biota
450–456
protective (for symbionts) leaf color
54–55, 182–186, 413, 454–456
resource for mutualists 384, 439–459
shapes of impoundments 23
structure and dynamics of resident
communities 225–227, 441–450
substrates for flora 366–368
swamps or islands? 438–439
theoretical considerations 438–439
water chemistry 133, 451–456
water supply for plant 157–160, 172, 227,
383–384
Pleistocene 505, 515
Pliocene 515, 569
Plio-Pleistocene 400, 466, 513
Pollen 105, 289, 465, 555, 566–567, 570,
574
Pollination (see also Flowers) 55–57, 75,
244, 246–268
anemophily 91, 260
Bromelioideae 262–264
cantharophily 267
chiropterophily 83–84, 87, 96, 246–247,
254–256, 258–260, 263, 268, 565
entomophily 84, 86–87, 96, 246, 252,
254–255, 257, 260, 263
melittophily 91, 97, 253, 255, 258–259,
262, 267
ornithophily 84, 86, 88, 91, 96–97, 246,
248, 251, 254–255, 258, 260–262,
265–267, 587
phalaenophily 252, 258, 260–261, 268
Pitcairnioideae 257–262
psychophily 267
relative to phenology 268–276
sphingophily 91, 97, 253–254, 260,
267
Tillandsioideae 247–257
trap-liners 261, 284, 507
Pollution 231
Polyembryony 90, 99
Polyploidy (see Chromosomes)
Predators 376
Protocarnivores 217
Puerto Rico 10, 165, 211, 379, 417
Quintana Roo State 423, 428–429, 432
Rainforest 202, 357, 364, 388, 547, 610
Rancho Grande 210, 411, 457
Refugia 514, 570, 576–577
Reproductive allocation (see also Life
history analysis) 302, 305–306, 326
Respiration (dark) 173
Restinga 9, 199, 299, 316, 363, 367, 387,
438, 441–444, 551
Rheophytes (see also Aquatic Bromeliaceae)
392
Rio de Janeiro State 7, 9–10, 279, 331, 336,
344, 363, 387–389, 397, 414, 419, 551,
620
Rio Grande du Sol State 336, 480
Rio Palenque 196, 205–207, 211, 422, 424
Riverine bromeliads 392
Roots
absorptive function 34, 48–50, 70,
111–113, 137, 162, 237–238
development 35, 100, 237, 560
holdfasts 229
morphology and extent of evolutionary
reduction 33–35, 43–44, 48–50, 100,
229, 238–240, 343, 395, 559–560
tropisms 49, 132, 400
Roraima Formation 219, 394
Salta Province 507
San Fernandez Islands 334
San Louis Potosi State 250
Santa Catarina State 335–336, 355, 394, 444
São Paulo State 336, 416
Savannas 66, 199, 219, 386, 391, 461
Saxicoles 6–7, 8–9, 41, 49, 58, 63, 66, 102,
104, 250, 285–286, 288, 303–308, 323,
326, 329, 330, 478
Secondary metabolites 517–518, 562–564
Seed dispersal (see also Ants) 8, 55–56, 75,
91, 98, 103–104, 245, 264, 268–269,
284–299
ballistic 102, 289
bats 294, 296, 346
birds 289–299, 550
Bromelioideae 289–299
crabs 296
dispersal syndromes in Bromeliaceae 297
frogs 296
nonvolant mammals 102, 294–299
Pitcairnioideae 287–288
Tillandsioideae 284–287
water 104, 245, 288
wind 296, 346, 359–360, 362
Seedlings (see also Heterochrony) 28, 47–48,
57, 99–100, 132–133, 139, 159, 279,
287, 322, 345, 356, 362, 365, 387,
389–390, 499, 611, 616
Seeds 98–105
Subject index
development 99
elaiosomes 288, 294
evolution 79, 101–102, 104–105
germination 99, 104, 259, 289, 299–301
morphology 90, 98–105, 249, 284–299,
499, 568, 570
viability 299–301
Sergipe State 551
Serrania de Macuria 369–370
Sierra de Alamos 616
Sister group of Bromeliaceae 464, 489, 522,
524, 526
Soil (see also Mineral nutrition)
definition of suspended soils 459–462
terrestrial soils, fertility 381, 472–475
Sonora 611, 616
South America 256, 285, 335–336, 390–392,
399–400, 420, 469, 487, 489, 507–508,
515, 570, 576, 583, 589, 598
South Carolina 143
Stems
anatomy 46, 560
for water storage 147–148
Sian Ka’an Biosphere Reserve 342, 423
Stomata 59–64, 75–77, 132, 141, 143,
145–146, 153–155, 161–162, 168, 179,
231, 423, 560
humidity sensors 62, 155, 159–160, 172
types in Bromeliaceae 61–63
Succession
fauna in shoots of Aechmea bracteata 430
in forest canopy and restingas 358–368
on ant carton 365–366
substrates for other flora 365–368
Talamanca (Cordillera de) 316, 415
Tambopota 425
Taxonomy
Brocchinia 471–478
Bromelioideae 536–538
chemical systematics 517–540
Cryptanthus 552–553
current status of Bromeliaceae 11–12
Neoregelia subgenus Hylaeaicum
545–546, 550
Pitcairnioideae 538–540
plesiomorphic character states for
Bromeliaceae 5–6, 70
Tillandsia and Racinaea 573–575,
577–578
Tillandsioideae 527–535, 555–559
traditional characters 94, 516–517,
555–559
Tepuis (see Guayanan Shield)
Terrestrial Bromeliaceae (see also Alpine
bromeliade; Saxicoles) 384–404
facultative types 384–390
673
lithophytes 392–396
profile of Bromelia humilis 400–404
restinga inhabitants 397–399
rupestrals 390–392
Tertiary 5, 460, 465, 577
Texas 192, 241
Trichomes (see also Ancestral habitats;
Mineral nutrition; Water relations)
development 28, 72
effects on gas exchange 144, 153
evolution 70–72, 77, 475–478, 493–500
evolution of absorptive capacity 475–478
functional variety 39, 46, 64, 67, 72–73,
75, 111–114, 132, 162, 400–401
hydration from moist air 163, 165–168,
230
nutrient uptake 163, 189, 219, 230–235,
477
reflectance 150–151, 163–165, 176, 178,
230, 428, 501
roots vs. shoots 232
structure 6, 8, 11–12, 24–28, 33, 35–36,
38, 52, 63–64, 70–75, 229–230, 400,
549, 562, 570
thermal insulation 331–334
water absorption 162–166, 229–230
Trinidad 12, 17, 115, 132, 155, 175–176,
352–355, 360, 400, 424, 440, 498
Tropisms (see also Roots) 47
United Kingdom 612, 614
Uruguay 579, 582
USA 334–335, 349, 569, 582–583, 587–588,
606, 609, 612, 614, 616, 618
Uses of bromeliads 589–607
commercial 606–607
fiber 67, 590, 595–597
food 595–597
forage 599
fuel 600, 602
medicine 602–604
miscellaneous 605–606
ornamental and ritual and mythical 601,
604–605
UV-B radiation 6, 110, 219, 331
Vascular cambium 85
Venezuela 7, 12, 125, 128–130, 147–148,
176, 182, 196, 198, 208, 210, 213,
219–222, 278, 281, 323, 383–384, 398,
401–404, 438, 456, 460, 481, 545, 569,
585, 602
Vera Cruz State 340, 345, 367, 408, 412
Viruses 429
Water relations (see also CAM; Foliage)
elastic modulus 149
674
Subject index
Water relations (cont.)
fog dependence 178, 325, 346, 395, 399,
482–483, 515
hydraulic lift 175
optimization of use 160–162
poikilohydry 166
retention during drought 146, 149–150,
164–167
seedlings 245–246
storage (capacitance/succulence) 32, 36,
51–53, 65, 67, 76, 111, 114, 122,
145–151, 172–174
tracheary cells 46, 48, 50–52, 66, 162, 378,
560
transpiration 51, 61–63, 147
uptake/hydration 50, 61, 64, 162–168,
174–175
water-use efficiency (WUE, transpiration
ratio) 114–123, 132, 142, 161, 174, 228,
383
xylem tensions 138, 140, 147, 175, 402
Windward Islands 400
World Resources Institute 610
Xanthophyll cycle (see also Photosynthesis)
177–179, 181, 228, 401
Xeromorphy (see also Water relations) 58,
111, 145–151, 154, 176, 227, 401, 404,
562–563
Xylem (see Water relations)
Yucatán State 7, 59, 259, 278–281, 294,
319–320, 342, 345, 387, 399, 407, 430,
456
Taxon index
Abromeitiella (= Deuterocohnia) 42, 43, 47,
105, 323, 325, 335, 400, 467, 470, 471,
495
Abromeitiella (Deuterocohnia) lorentziana 41
Abronia 418
Acacia 215
A. cornigera 340
Acanthostachys 13, 65, 74, 98, 386
Acari 411
Acarina 221
Acetobacter diazotrophicus 213
Acutaspis tingii 410
A. umbonifera 410
Admontia 412
Aechmea 11, 13, 75, 81, 88, 92, 97, 101, 115,
198, 200, 211, 262, 263, 283, 284, 289,
291, 293, 294, 296, 297, 298, 299, 328,
347, 385, 397, 418, 419, 451, 456, 464,
478, 479, 480, 487, 494, 498, 517, 521,
525, 533, 535, 536, 537, 538, 546, 547,
550, 588, 598, 604
A. aculeatosepala 546
A. subgenus Aechmea 546
A. angustifolia 7, 87, 90, 101, 212, 295, 366,
407, 422, 424
A. aquilega 115, 120, 121, 125, 155, 172,
175, 440, 449
A. aripensis 155, 156, 354
A. bracteata 23, 27, 30, 53, 65, 71, 75, 82,
86, 90, 96, 102, 133, 153, 164, 200, 216,
218, 226, 232, 236, 263, 265, 291, 294,
342, 343, 369, 407, 426, 427, 429, 430,
433, 434, 437, 452, 455, 588, 590, 591,
602, 607
A. bracteatus 607
A. brassicoides 23, 427
A. brevicollis 23, 295, 394, 424
A. bromeliifolia 81, 90, 156, 320, 397, 408,
433
A. chantinii 33, 35, 73
A. subgenus Chevaliera 295, 517
A. coelestis 300, 301
A. dactylina 90, 102
A. distichantha 246, 265, 267, 298, 299
A. downsiana 354
A. fasciata 82, 86, 173, 263, 413
var. fasciata 266
A. fendleri 121, 173, 354
A. filicaulis 456
A. fulgens 82, 86, 91, 185, 273
A. gamosepala 293, 298, 299
A. glomerata 518
A. haltonii 536
A. kuntzeana 90
A. subgenus Lamprococcus 478, 546
A. lasseri 210
A. lingulata 120, 121, 263, 443
A. longifolius 347, 424, 435, 593
A. lueddemanniana 283
A. macavughii 283
A. magdalenae 32, 66, 90, 103, 107, 108,
124, 125, 127, 128, 156, 177, 246, 283,
284, 323, 325, 326, 354, 389, 403, 494,
507, 590, 591, 596, 597, 598, 605, 606,
607, 608, 611
A. marie-reginae 92, 278
A. meliononii 427
A. mertensii 102, 276, 295, 347, 424, 434,
483
A. mexicana 283, 284, 460, 461
A. miniata 185
A. nallyi 406
A. nudicaulis 9, 62, 120, 121, 129, 152, 155,
172, 173, 174, 175, 194, 198, 271, 272,
298, 299, 301, 355, 363, 397, 398, 416,
418, 438, 442, 443, 444, 449, 466, 478,
479, 591
var. aequalis 41
A. organensis 293, 298, 299
A. section Ortgiesia 85
675
676
Taxon index
A. paniculigera 451, 452, 454
A. pectinata 55, 81, 298
A. penduliflora 25, 292
A. phanerophlebia 215, 320, 407, 427, 429,
433, 437
A. subgenus Podaechmea 283, 536
A. pubescens 358, 359, 360
A. purpureoresea 263
A. recurvata 236
A. rosea 74
A. setigera 82, 427
A. tessmannii 591, 599, 604
A. tillandsioides 69, 81, 164, 276, 292, 295,
424, 466, 491, 591, 599, 604, 607
var. kienastii 367, 424, 426
A. tuitensis 283, 284
A. veitchii 23
A. warasii 273
A. wittmackiana 323
A. zebrina 212, 591, 599, 602, 604
Aectumea setigera 86
Aeromonas 211
Agavaceae 117, 127, 260, 414
Agave 228, 316, 403
Agave desertii 148, 171, 401
Alcantarea 13, 284, 286, 308, 331, 335, 368,
385, 386, 437, 439, 487, 498, 555, 557,
564, 565, 569
A. duarteana 391
A. edmundoi 498
A. farneyi 498
A. hatscbachii 391, 498
A. imperialis 31, 32, 281, 395, 439, 498
A. nevaresii 83, 286
A. regina 7, 88, 246, 265, 266, 270, 277, 301,
319, 390, 438, 498, 518
Alchornea triplinervia 341
Alloplectus 272
Aloe 119
Alnus acuminata 364
Amazilia fimbriata 255
Anabaena 213
Ananas 13, 49, 62, 75, 110, 113, 124, 125,
227, 228, 275, 294, 354, 387, 403, 404,
412, 491, 494, 525, 533, 534, 535, 536,
537, 538, 540
A. ananassoides 125, 128, 277, 404, 591, 598
A. bracteatus 90, 277, 591, 598, 607
A. comosus x, 9, 46, 60, 66, 68, 74, 107, 108,
119, 120, 124, 125, 128, 129, 148, 149,
150, 164, 172, 173, 210, 227, 228, 277,
331, 354, 385, 400, 401, 403, 404, 413,
488, 493, 494, 587, 589, 590, 591, 595,
598, 602, 605, 606, 607, 608
var. Brecheche 129
var. Spanish Red 129
A. lucidus 125, 591, 598
A. paraguazensis 125, 404, 591, 598
Andrea 517
Androlepis 13, 92, 105, 278
A. skinneri 92, 460, 461
Annona glabra 7, 356
Anochetus 425
A. emarginatus 437
Anopheles 440
A. aegypti 445
A. bellator 440
A. homunculus 440
A. neivai 440
Anthurium 290, 291, 357, 367
A. gracile 347, 434
A. hacumense 360
Aparasphenodon brunoi 418
Apis mellifera 267
Araceae 98, 214, 290, 295, 356, 358, 360,
484, 485
Araeococcus 13, 347, 385, 479, 525, 533,
535, 536, 537, 538
A. micranthus 90, 293
A. pectinatus 524
Aranea 221, 430
Araneida 411
Aratus 449
Arecaceae 331, 397, 523
Aregelia 545; see also Regelia
A. subgenus Eu-Aregelia 546
Arphnus melanotylus 410
Artibeus lituratus 256
Ascaridea 430
Asclepiadaceae 215, 424, 619
Astelia 478
Asteraceae 5, 147, 331, 333, 391
Asterolecanium epidendri 410
Atta 429
A. cephalotes 429
A. mexicana 410
Avicennia germinans 310
Ayensua 13, 69, 92, 105, 132, 319, 469, 470,
472
A. uaipanensis 59, 96, 246, 262, 391, 394
Azolla 213
Azteca 295, 348, 367, 425, 426, 429, 430
Aztekium hintonii 615
Bacillus 211
Billbergia 13, 33, 74, 75, 81, 86, 88, 115, 156,
262, 263, 273, 274, 276, 293, 294, 295,
335, 341, 385, 397, 413, 418, 419, 478,
479, 487, 518, 525, 533, 535, 536, 537,
538
B. amoena 82
var. amoena 265, 266, 271, 273, 274, 276
B. subgenus Billbergia 276
B. brasiliensis 25, 292
Taxon index
B. distachia var. distachia 274
B. elegans 88, 90, 102, 103, 294, 299
B. euphemiae var. euphemiae 274
B. subgenus Helicodia 276
B. horrida 246, 263
var. tigrina 274
B. lietzei 413
B. macrolepis 69, 524
B. nutans 97, 265, 274, 275, 491
B. porteana 9, 23, 39, 87, 88, 200, 226, 246,
340, 341, 346, 369, 371
B. pyramidalis 355, 445, 608
var. concolor 274
var. pyramidalis 271, 273, 276
B. robert-readii 263
B. rosea 103
B. sanderiana 48, 55
B. saundersii 413
var. debilis 274
B. vittata 274, 418, 518
B. zebrina 73, 294, 417
Blattodea 411
Bombus 267
Bothrops schlegeli 418
Brachycera 411
Brassalvola nodosa 365
Brewcaria 13, 95, 260, 394, 466, 469, 470,
516
B. reflexa 473
Brocchinia 11, 13, 24, 30, 39, 43, 44, 53, 70,
71, 73, 74, 75, 91, 94, 95, 101, 104, 105,
112, 113, 123, 132, 133, 199, 200, 220,
231, 281, 288, 390, 394, 463, 466, 469,
470, 471–8, 488, 495, 496, 497, 498,
500, 518, 522, 525, 526, 530, 533, 535,
536, 537, 539, 540, 541
B. acuminata 21, 53, 69, 71, 74, 105, 189,
200, 215, 234, 249, 257, 386, 394, 427,
473, 474, 475, 476, 477, 528, 532
B. amazonica 473, 474
B. bernardii 394
B. cataractacum 475
B. cowanii 394, 473, 474, 477
B. cryptantha 394
B. deliculata 249, 475
B. gilmartinii 473
B. hechtioides 39, 71, 219, 473, 474, 477
B. hitchcockii 475, 526
B. maguirei 473, 474, 475, 477
B. maguleri 249, 386
B. melanacra 59, 249, 319, 473, 474, 475, 477
B. micrantha 24, 33, 43, 49, 74, 125, 178,
231, 249, 281, 386, 438, 439, 473, 474,
475, 477
B. paniculata 43, 63, 473, 474, 475
B. prismatica 231, 386, 473, 474, 476, 477,
498
677
B. reducta 23, 24, 39, 59, 70, 71, 74, 105,
133, 134, 189, 190, 219, 220, 221, 222,
224, 231, 232, 235, 268, 371, 386, 394,
450, 473, 474, 475, 476, 477, 497
B. serrata 249, 472, 473, 539
B. steyermarkii 96, 262, 473, 474, 476, 477
B. tatei 7, 24, 101, 105, 213, 220, 231, 276,
281, 288, 386, 390, 419, 439, 473, 474,
475, 477, 498, 526
B. vestita 113, 190, 249, 473, 474, 476, 498
Bromelia 13, 25, 27, 28, 33, 34, 41, 47, 49,
54, 57, 59, 60, 63, 64, 65, 74, 75, 91, 98,
110, 113, 115, 124, 218, 227, 228, 293,
294, 328, 387, 393, 397, 398, 409, 410,
478, 480, 491, 494, 517, 518, 525, 528,
530, 532, 533, 534, 535, 536, 537, 538,
598
B. alsodes 591, 598, 603, 604
B. balansae 32, 164, 291, 292, 294
B. chrysantha 125, 591, 603
B. goeldiana 125
B. hemisphaerica 591, 598
B. humilis 62, 107, 108, 123, 124, 125, 129,
130, 131, 170, 171, 174, 176, 177, 198,
210, 228, 323, 331, 354, 398, 400–4, 493
B. karatas 194, 262
B. laciniosa 590, 591, 606, 607
B. nidus-puellae 591, 598, 603, 605
B. pinguin 68, 186, 262, 296, 591, 598, 603,
606, 607
B. plumieri 121, 172, 591, 598, 603, 605, 606,
607
B. serra 265, 591, 607
B. tenuifolia 464
Bromeliaceophyllum oligovaenicum 464
B. rhenanthum 464
B. urbaniana 591
Bromeliales 490, 522
Bromelianthus heuflerianus 464
Bromeliiflorae 522, 523
Bromelioideae 10, 12, 25, 28, 30, 39, 44, 47,
48, 49, 50, 53, 55, 56, 57, 62, 63, 66, 67,
71, 73, 74–5, 81, 82, 86, 91, 92, 94, 95,
96, 98, 101, 102–3, 105, 107, 108, 110,
111, 112, 113, 114, 118, 124, 150, 154,
164, 197, 200, 212, 231, 232, 234, 247,
262–84, 288, 289–328, 336, 340, 345,
346, 357, 365, 367, 385, 386, 388, 398,
399, 417, 424, 427, 429, 431, 433, 449,
466, 472, 477, 478–80, 483, 486, 488,
491, 492, 493, 495, 496, 497, 498, 499,
502, 516, 521, 522, 525, 526, 528, 533,
534, 535, 536, 537, 538, 540, 541, 545,
546, 550, 551, 552, 602
Bruchidae 410
Bucida spinosa 342
Bumelia celastrina 346
678
Taxon index
Bursera simaruba 310, 311, 343, 344, 429
Burseraceae 290
Cacicus haemorrhous 416
Cactaceae 98, 117, 127, 136, 291
Calathea 128
Callithrix geoffroyi 414
Calyptranthes 347
Campodeidae 411
Camponotus 425, 435
C. abdominalis 430
C. femoratus 295, 347, 425, 432, 435, 550
Canistropsis 537
Canistrum 13, 25, 74, 81, 85, 371, 478, 480,
494, 525, 533, 535, 536, 537, 538, 545,
546, 549
C. fosterianum 74
C. lindenii 92, 100, 355
Carabidae 411
Caria domitianus domitianus 564
Carica papaya 602, 603
Castine phalanis 408
Castnia eudesmia 261
Catopsidae 411, 570
Catopsis 11, 13, 34, 61, 79, 81, 85, 92, 93,
94, 95, 102, 103, 133, 135, 136, 198,
247, 254, 268, 278, 280, 284, 315, 339,
341, 343, 351, 357, 362, 387, 412, 463,
478, 495, 522, 527, 528, 529, 530, 541,
555, 557, 561, 562, 563, 564, 565, 566,
568, 569, 570, 585, 588, 605
C. berteroniana 59, 133, 134, 136, 164, 190,
200, 218, 219, 224, 278, 280, 285, 315,
319, 321, 323, 337, 351, 352, 371, 394,
445, 562, 570
C. compacta 280
C. delicatula 280
C. floribunda 29, 37, 93, 136, 148, 194, 280,
285, 351
C. hahnii 280, 591
C. juncifolia 280
C. mexicana 280
C. micrantha 280
C. minimiflora 280
C. montana 280, 525, 528, 530, 532, 533,
535, 536, 537
C. morreniana 136, 278, 280, 559, 591
C. nitida 136, 280
C. nutans 26, 27, 71, 72, 109, 134, 136, 150,
151, 152, 153, 165, 166, 186, 210, 234,
254, 278, 280, 285, 337, 351, 352, 362,
524, 556
C. paniculata 254, 280
C. pisiformis 93, 280
C. sessiliflora 83, 280, 566, 567, 591
C. subulata 280, 591
C. subgenus Tridynandra 565
C. wangerinii 278, 280, 592
C. wawranea 280, 525, 528, 530, 532, 533,
535, 536, 537
C. werckleana 280
Cebia peltandra 364
Cecropia 215, 348
Ceratophyllaceae 239
Ceratopogonidae 221, 440, 442
Cercidium praecox 378
Cerridomyiidae 440
Chalcicoidea 221
Chelonethida 441
Chilopoda 411, 430
Chironomidae 221, 442
Chiropterotriton 420
Chlorophyta 440
Chlorostilbon aureoventris 225, 267
Chrysomelidae 410
Cimolus vitticeps 410
Citrus 360, 367, 378, 424, 425
Cladosporium myrmecophilum 214
Clusia 174, 366, 398
C. alata 382
Clusiaceae 367, 397
Coccidae 410
Coccinellidae 411
Codonanthe 189
C. macrodenia 367, 426
C. uleana 347, 366
Collembola 221, 411, 430, 460
Coleoptera 221, 411, 412, 430
Colibri coruscans 261, 267
Columnea 272, 366
Commelinaceae 89, 478, 523
Commeliniflorae 522, 523
Connellia 13, 69, 95, 105, 260, 394, 466, 469,
470
C. smithiana 260
Conocarpus erecta 310, 311
Coprinus 88
Coreidae 410
Coryanthes speciosa 426
C. speciosum 367
Costaceae 523
Cottendorfia 13, 61, 63, 69, 70, 91, 92, 93,
95, 104, 257, 260, 278, 470, 495
C. florida 21, 47, 391, 564
Couratari stellata 364
Coussopoa microcarpa 341
Crematogaster 340, 425, 426, 430
C. linata 295
C. linata parabiotica 425
Crescentia alata 365
Crophinus costatus 410
Cryptanthoideae 552
Cryptanthus 8, 13, 30, 34, 35, 38, 47, 54, 73,
74, 75, 81, 86, 92, 95, 97, 98, 115, 235,
Taxon index
263, 278, 319, 325, 386, 478, 479, 480,
487, 491, 494, 516, 525, 533, 534, 535,
536, 537, 538, 551–3
C. acaulis 47, 164, 325, 491
C. bahianus 491
C. beuckeri 294, 491
C. bromelioides 9, 25, 90, 108, 357
C. correia-araujoi 82
C. subgenus Cryptanthus 93, 263, 294, 491,
551, 552, 553
C. exaltatus 264
C. subgenus Hoplocryptanthus 264, 294,
551, 552, 553
C. leopoldo-horstii 391
C. odoratissimus 264
C. pseudoscaposus 294
C. schwackeanus 391
Culex 446
Culicidae 221, 443, 449
Culicoidel 221
Cullidae 442, 458
Curaeus curaeus 261
Curculionidae 410, 411
Cyclanthaceae 357
Cyperaceae 235, 523
Cyphomyrmex minutus 430
Dalbergia 456
Dascyllidae 411
Deinacanthon 13, 517
Dendrobates pumilio 418
Dendrocoris variegatus 410
Dendrotriton 420
D. xolocalcae 420
Dermaptera 411
Deuterocohnia 13, 88, 105, 257, 267, 335,
400, 422, 467, 470, 471, 495
D. haumanii 267, 323
D. longipetala 96, 262, 264, 267
D. lorentziana (see Abromeitiella)
D. meziana 46, 84, 85, 539
D. schreiteri 93, 303
Diabrotica porracea 410
Diaspidae 410
Diaspsis bromeliae 408
Dieffenbachia 128
Dionea 224
Diplopoda 221, 411, 430
Diplura 411
Diptera 221, 411, 430, 442, 446, 457
Dischidia 424
Disteganthus 13, 54, 389, 478, 494
Dolichoderinae 434
Dolichoderus 425, 430
D. bispinosus 430
Drosera 219
679
Drosophilidae 411
Drynaria 214
Dyckia 7, 13, 21, 34, 45, 50, 53, 62, 73, 85,
88, 91, 93, 98, 101, 111, 113, 130, 176,
257, 260, 267, 319, 355, 386, 390, 391,
393, 407, 409, 422, 437, 464, 467, 470,
471, 479, 480, 491, 495, 496, 521, 525,
533, 535, 536, 537, 538, 539
D. brevifolia 53, 608
D. dissitiflora 391
D. ferox 264, 267
D. floribunda 84, 267
D. extevesii 21, 26
D. ferox 246
D. pseudococcinea 397
D. ragonesei 80, 93, 265, 267
D. velascana 265, 267
Dynastor napolean 408
Dysdercus mimulus 410
Dysmimococcus probrevipes 410
Edmundoa 537
Elpidum bromeliarium 442, 444
Eleuthrodactylus 417
E. jasperi 417
Encholirium 13, 45, 85, 130, 257, 259, 279,
319, 320, 330, 331, 390, 391, 393, 407,
437, 467, 470, 471, 479, 480, 495, 525,
533, 535, 536, 537, 538, 539
E. glaziovii 84, 246, 258, 260, 267, 268
Enchytraeidae 411
Encyclia cordigera 365
E. tampensis 198, 205, 311, 338, 343
Epipedobates tricolor 605
Epidendrum immatophyllum 367, 426
E. marsupiale 343
Epiphyton 526
Equisetum 187
Ericaceae 364, 415
Eriocaulaceae 391
Eriophorum vaginatum 235
Erythroxylon 367
E. ovalifolia 296
Erythoxylum coca 605
Espeletia 147, 333
Euphorbia horwoodii 619
Euphorbiaceae 619
Eurema diara 262
Eutrigaster sporadonephra 461, 462
Exptochiomera albomaculata 410
Fabaceae 147
Fagaceae 5
Fascicularia 13, 98, 264, 289, 331, 336, 386,
390, 478, 488, 536
F. bicolor 246, 386
F. pitcairniifolia 355
680
Taxon index
Fernseea 13, 264, 480
F. itatiaiae 335
Ferrocactus acanthoides 171
Ficus 366
F. aurea 310, 311, 343
Flagellariaceae 523
Forestiera segregata 310
Formicidae 221, 410, 411, 422, 432
Formicinae 434
Fosterella 13, 30, 42, 53, 58, 71, 73, 92, 94,
95, 101, 104, 105, 111, 130, 132, 257,
260, 469, 470, 472, 491, 525, 533, 535,
536, 537, 539
F. penduliflora 24, 52, 59, 84, 264, 471, 540
F. spectabilis 84, 260
Fraxinus caroliniana 341
Fritziana goeldii 418
Fusarium 413
Gastropoda 411
Gastrotheca fissilis 418
G. fissipes 417
Gecarcinus lateralis 296
Genlesia 219
Geohintonia mexicana 615
Geranospiza caevulescens 416
Gesneriaceae 184, 189, 214, 295, 415
Gigaspora 210
Ginkgo 619
Glomeropitcairnia 11, 13, 73, 79, 92, 95, 101,
247, 284, 463, 470, 481, 495, 516, 521,
522, 526, 527, 528, 529, 530, 532, 533,
535, 536, 537, 541, 555, 562, 564, 566,
568, 569, 570, 571
G. erectiflora 438
G. penduliflora 90, 104
Glomeropitcairniaeae 516, 525
Glomus tenue 210
Glossoscolecidae 411
Gnathostomulida 501
Gramineae 498
Grapsidae 449
Greigia 13, 34, 74, 82, 85, 115, 264, 294, 331,
390, 399, 478, 480, 488, 500, 536, 598
G. oaxacana 264
G. sodiroana 592, 606, 607
G. sphacelata 264, 592
Gryllidae 410, 411
guava 196
Guzmania 13, 54, 61, 81, 91, 94, 95, 103,
212, 247, 254, 256, 257, 258, 357, 386,
387, 392, 412, 451, 466, 483, 491, 495,
521, 525, 528, 529, 531, 532, 533, 535,
536, 537, 540, 555, 557, 561, 562, 563,
564, 565, 566, 568, 569, 570, 579
G. acorifolia 392
G. acuminata 592, 599
G. alcantareoides 256
G. berteroniana 211
G. bismarckii 184
G. blassii 611
G. caricifolia 498
G. coriostachys 256
G. cylindrica 370
G. diffusa 564
G. eduardii 592, 599, 604
G. fosteriana 256
G. globosa 83, 89
G. glomerata 564
G. kentii 257
G. lindenii 38
G. lingulata 52, 54, 38, 109, 134, 135, 150,
164, 184, 194, 369, 370, 563
var. minor 246
G. melinonis 212, 592, 599, 604, 606
G. monostachia 7, 65, 71, 107, 109, 116, 121,
122, 133, 136, 137, 140, 146, 149, 153,
156, 157, 158, 159, 168, 176, 177, 179,
180, 181, 182, 186, 195, 204, 216, 225,
228, 256, 271, 272, 277, 285, 315, 337,
341, 342, 351, 352, 354, 356, 360, 362,
369, 370, 406, 413, 458, 494, 528, 530,
532, 540, 559, 567, 592, 599, 604
G. mucronata 136, 256
G. musaica 565, 592
G. nicaraguensis 271, 528, 530, 532, 559,
564, 615
G. plicatifolia 528, 530, 532
G. rhonhofiana 528, 530, 532
G. sanguinea 64, 86, 136, 263, 369, 370, 528,
532, 556, 592
var. brevipedicellata 273
G. scherzeriana 272
G. subgenus Sodiroa 498
G. spectabilis 528, 530, 532
G. weberbaueri 446, 451, 458
G. wittmackii 83, 256, 528, 530, 532
G. zahnii 182, 184, 273, 559
Haemodoraceae 523
Haemodorales 522
Hanseniella 408
Hechtia 3, 13, 28, 45, 50, 53, 73, 85, 92, 95,
105, 111, 113, 130, 176, 218, 257, 260,
267, 278, 288, 319, 386, 393, 466, 470,
471, 480, 496, 521, 539, 566
H. carlsoniae 85
H. glomerata 173
H. scariosa 267
H. schottii 267, 280, 320
Heliamphora 190, 219, 220
H. hederodoxa 222
H. nutans 220, 221
H. tatei 220
Taxon index
Helicina zephyrina 410
Helicinidae 410
Heliconia 442, 445
Heliconiaceae 523
Helminthosporium rostratum 413
Hemiberlesia palmae 408
Hemiptera 411
Hermanthena candida 564
Hirudinae 411
Histeridae 411
Hohenbergia 7, 13, 55, 263, 363, 390, 397,
408, 409, 418, 419, 451, 478, 479, 525,
533, 536, 537, 538
H. blanchetti 246
H. subgenus Hohenbergia 479
H. pendulaflora 358
H. urbanianum 32
H. subgenus Wittmackiopsis 479
Hohenbergiopsis 13, 105
Homo sapiens 218
Homoptera 221, 223, 347, 408, 422, 425,
429, 431
Hoya 427
Hura crepitans 346, 364
Hydnophytum 427
Hyla brunnea 417
H. truncata 296
H. venulosa 417
Hymenoptera 221
Hypoclinea 348
H. bispinosa 429
Idras 346
Impatiens 501
Inga 347
Ionantha scaposa (see Tillandsia kolbii)
Ionopsis satyrioides 426
I. utricularioides 426
Iridomyrmex 428
Isoetes 116
Isopoda 430
Japygidae 411
Juglandaceae 5
Juncaceae 523
Kalanchoe 173
Karatas 545
K. section Regelia 546
Karatophyllum bromelioides 464
Lagothrix lagothicha 600
Lagriidae 410
Lauraceae 290
Lemnaceae 501
Lentibulariaceae 224
Leontopithecus rosalia 414
681
Lepidoptera 221
Leptogeny 430
Leptogrion perlongum 449
Leptospermum 340
Liliales 90
Liliopsida 3, 22, 34, 50, 52, 464, 478, 518,
521–7, 539, 540, 564
Lindmania 13, 69, 73, 92, 93, 257, 394, 469
L. guianensis 262
L. longipes 473
L. serrulata 24
L. wurdackii 24
Liodidae 411
Liquidambar styraciflua 286, 287
Lobeliaceae 331
Loganiaceae 599
Lonchophylla bokermanni 260
Loranthaceae 290, 291, 415
Loricifera 501
Lowiaceae 523
Lucanidae 411
Lupinus 147
Lygaeidae 410
Lymania 13, 357, 494, 525, 533, 535, 536,
537, 538
L. smithii 185
Magnoliophyta 4, 5, 8, 19, 75, 277, 463
Magnoliopsida 68
Marantaceae 523
Marcgraviaceae 415
Margarornis rubiginosus 415
Maschalocephalus 489
Mayacaceae 540
Melanapsis odontoglossi 410
Melastomataceae 215, 340
Membracidae 410
Menispermaceae 599
Mesostigmata 411
Metacypris 444
Metamasium callizona 412
Metamasius hemipterus hemipterus 410
Metasesarma rubripes 408
Metopaulias 449
M. depressus 450
Metriocnemus 221
Metriona trisignata 410
Mezobromelia 13, 94, 95, 254, 525, 528, 529,
530, 531, 532, 533, 535, 536, 537, 555,
557, 564, 565, 566, 568, 569, 576, 579
Microcoelia 374
Microgramma lycopodoides 196, 383
Mimosestes dominicanus 410
Miridae 410
Monacid debilis 425
Monimiaceae 341
Monomorium ebeninum 430
682
Taxon index
Monotropa 379
Moraceae 214, 295, 341
Mormidea collaris 410
Musaceae 523
Myrmecodia 427
Myrmicinae 434
Myrsine guianensis 310
Myrtaceae 546
Napea eucharila 564
N. theages theages 564
Nasutitermes 437
N. acajutlae 436
Nasutitermitinae 437
Navia 11, 13, 24, 61, 69, 70, 71, 73, 91, 101,
104, 105, 257, 260, 263, 287, 288, 385,
386, 393, 394, 464, 466, 469, 470, 475,
488, 495, 496, 516, 525, 533, 535, 536,
537, 539
N. arida 260, 539
N. caulescens 84
N. glandulifera 75
N. glandulosa 24, 39, 73, 476
N. igneosicola 539
N. jauaensis 260
N. lactea (see N. ocellata)
N. linearis 84
N. ocellata 263
N. phelpsiae 539
N. polyglomerata 84
N. saxicola 394
N. splendens 260, 473, 528, 532
N. tentaculata 386
Nematocera 411
Neoglaziovia 13, 66, 74, 124, 328, 480
N. variegata 108, 320, 590, 592, 606, 607
Neoponera villosa 429
Neoregelia 3, 13, 32, 33, 38, 42, 55, 56, 81,
82, 85, 87, 88, 89, 115, 200, 262, 263,
293, 294, 297, 305, 328, 347, 357, 397,
456, 464, 478, 525, 533, 535, 536, 537,
538, 545, 546, 547, 549, 550
N. abendrothae 21, 25, 502
N. aculeatosepala 546, 547
N. subgenus Amazonicae 546
N. ampullacea 81
N. carolinae 545
N. cathcartii 545
N. concentrica 294–5, 299, 547
N. cruenta 119, 296, 316, 363, 367, 397, 398,
438, 441, 442, 444, 479
N. cyanea 547
N. diamantinensis 391
N. eleutheropetala 85, 548, 549, 550
var. bicolor 548, 549
var. eleutheropetala 548, 549
N. subgenus Hylaeaicum 85, 97, 478, 545–50
N. lactea 56
N. leviana 548, 549, 550
N. longisepala 75, 478
N. macwilliamsii 56
N. margaretae 548, 549, 550
N. marmorata 266
N. mooreana 548, 549, 550
N. myrmecophila 85, 478, 483, 548, 549, 550
N. subgenus Neoregelia 479, 545, 546, 549
N. nivea 56
N. pascoalina 292
N. pauciflora 41, 74
N. pendula 550
var. brevifolia 548, 549
var. pendula 547, 548
N. peruviana 547, 548, 550
N. petropolitana 56
N. pineliana 524
N. rosea 548, 550
N. spectabilis 547
N. stolonifera 90, 292, 295, 548, 549, 550
N. tarapotoensis 547, 548, 549, 550
N. wurdackii 548, 550
Nepenthaceae 215
Nepenthes 223
Nicotiana tabacum 520
Nidularium 13, 47, 55, 57, 61, 74, 75, 81,
218, 262, 263, 293, 296, 298, 341, 357,
371, 386, 389, 464, 478, 479, 480, 491,
494, 500, 502, 525, 533, 535, 536, 537,
538, 545, 549
N. ambiguum 92
N. antoineanum 293, 298, 299
N. burchellii 23, 54, 67, 115, 185, 186, 371
N. eleutheropetalum 545, 546
N. fulgens 300
N. innocentii 108, 115, 156, 293, 298, 299,
388, 389, 406
var. paxianum 355
N. longiflorum 413
N. lymanioides 30, 34
N. myrmecophilum 545, 546
N. procerum 156, 246, 388, 389, 406
var. procerum 355
N. subgenus Regelia 545, 546
N. selloanum 524
Nitidulidae 411
Nototriton 420
Nymphaeaceae 89
Ochagavia 13, 98, 264, 331, 334, 390, 478
Ochrimnus vittiscutis 410
Odonata 430, 446
Odontomachus bruneus 430, 432, 437
O. mayi 434
Ogdoecosta biannularis 410
Oniscoidea 411
Taxon index
Oplomus rutilus 410
Opuntia 228, 403
O. ficus-idea 171
Orbatei 411
Orchidaceae 5, 198, 215, 295, 305, 323, 338,
340, 342, 343, 364, 365, 374, 377, 392,
394, 429, 430, 449, 464, 484, 485, 486
Orthophytum 13, 32, 47, 62, 74, 89, 95, 98,
115, 235, 264, 289, 325, 331, 390, 478,
479, 487, 491, 516, 521, 525, 533, 534,
535, 536, 537, 538, 552
O. benzingii 325
O. gurkenii 524
O. humile 26
O. saxicola 264
Ostracoda 442
Pachycondyla goeldii 434
P. villosa 429, 430, 432
Paepalanthus bromelioides 391
Pandanus 296
Papilio thoas 267
Paramecium 445
Paroecantus aztecus 410
Patagonia gigas 261
Pedipalpida 411
Pentatomidae 410
Peperomia 55, 115, 196, 364, 367, 484, 618
P. macrostachya 366
P. magnoliaefolia 148
Pepinia 13, 69, 71, 73, 98, 104, 288, 469,
470, 471, 525, 533, 536, 537, 539
P. aphelandrifora 69
P. corallina 69
P. fimbriatobracteata 88
P. pruinosa 84
P. pulchella 592, 599
P. punicea 288, 392
P. schultzei 69
Pereskia 136
Phaethornis idaliae 255
P. superciliosis 284
Phalangida 411
Phalangidae 430
Philander opossum 296
Philaphyllum tenuifolium 439
Philodendron leal-acostae 367
P. saggitifolia 359
Philydraceae 523
Philydrales 522
Phoebus 262
Phytophthora 413
pineapple (see Ananas comosus)
Pinus 313, 340, 345, 349
Piper 128
Piperaceae 214, 215, 295, 364, 484, 486
Pitcairnieae 469, 471
683
Pitcairnia 8, 14, 21, 25, 28, 31, 34, 42, 44,
47, 50, 51, 54, 56, 57, 58, 59, 64, 68,
69, 73, 84, 86, 91, 92, 96, 97, 98, 104,
105, 111, 130, 132, 148, 169, 231, 254,
257, 258, 262, 288, 300, 357, 358, 385,
386, 389, 392, 393, 413, 464, 466, 467,
469, 470, 471, 482, 483, 495, 516, 517,
518, 525, 533, 535, 536, 537, 588, 603,
604
P. albiflos 258
P. andraeana 45, 236
P. angustifolia 592, 603
P. aphelandriflora 288
P. arcuata 84, 88, 258
P. bakeri 84, 86
P. bifrons 132
P. breedlovei 592
P. brevicalycina 96, 97, 98, 246, 258, 262
P. bromeliifolia 194
P. brongniartiana 84
P. bulbosa 125
P. corallina 88, 96, 246, 258
P. feliciana 31, 45, 57, 288, 465, 480
P. fimbriato-bracteata 258
P. flammea 10, 84, 86, 100, 109, 110, 237,
238, 300, 392
var. flammea 266
var. pallida 258, 266
P. glaziovii 465
P. halophila 197
P. heterophylla 31, 45, 56, 57, 59, 93, 97, 98,
132, 145, 275, 288, 386, 539, 592, 603
P. integrifolia 108, 132, 197, 198, 592, 603
P. loki-schmidtiae 246, 258
P. macrochlamys 27, 153, 164
P. maidifolia 592
P. meridensis 96
P. nubigena 258
P. palmoides 258
P. pulverulenta 96
P. pungens 36, 69, 210, 592, 603
P. riparia 28, 31, 34, 41, 43, 45, 56
P. rubro-nigriflora 258
P. spicata 592, 603
P. tabuliformis 45, 57
P. trianae 36, 69
P. undulata 164
P. unilateralis 258
Pitcairnioideae 11, 25, 28, 30, 31, 34, 36, 39,
42, 44, 48, 52, 53, 62, 63, 67, 69, 70, 71,
73, 74, 75, 81, 84, 86, 88, 92, 93, 94, 95,
96, 98, 101, 104–5, 108, 111, 112, 115,
118, 132, 164, 200, 231, 234, 245, 247,
257–62, 263, 264, 267, 277, 287–8, 331,
336, 354, 357, 385, 386, 390, 391, 392,
393, 394, 399, 427, 437, 464, 466–78,
480, 482, 483, 492, 495, 496, 497, 516,
684
Taxon index
Pitcairnioideae (cont.)
518, 521, 522, 525, 526, 528, 533, 535,
536, 537, 538, 539, 540, 541, 566, 570,
571
Platanaceae 5
Platycerium 214
Platypodium elegans 346
Platypsaris rufus 416
Pleopeltis astrolepis 196
Plethodontidae 420
Poaceae 5, 85, 213, 523
Polypodiaceae 215
Polypodium polypodioides 367
Polytmus guainumbi 255
Ponerinae 434
Pontderiaceae 523
Pontederiales 522
Portea 14, 81
P. petropolitana 32, 66, 355
Procyrta intectus 410
Proechimys iheringi 296
Prostigmata 411
Pselaphidae 411
Pseudaechmea 14
Pseudananas 14, 34, 47, 74, 124, 491
P. sagenarius 292, 325, 592, 598
Pseudococcida 410
Pseudococcus brevipes 408
Pseudocolaptes lawrencii 415
Pseudomonas 211
P. stutzeri 212, 213
Pseudomyrmex 340
Psidium 196, 208, 383, 456
Psocoptera 411
Ptilidae 411
Puccinia pitcairniae 413
P. tillandsiae 413
Puya 6, 14, 25, 43, 45, 46, 62, 65, 69, 73, 96,
97, 101, 104, 122, 130, 131, 147, 148,
218, 257, 258, 260, 261, 265, 288, 299,
319, 331, 332, 333, 334, 335, 357, 385,
386, 390, 399, 400, 464, 466, 467, 468,
469, 470, 471, 480, 482, 483, 486, 495,
518, 521, 525, 530, 533, 535, 536, 537,
538, 539, 566, 570, 593, 602, 603
P. aequatorialis 261, 332, 333, 334, 528,
532
var. aequatorialis 333
P. alpestris 246
P. aristeguietae 96, 262
P. berteroniana 261, 300, 301
P. chilensis 261, 590, 592, 603
P. clava-herculis 316, 331, 332, 333, 334
P. compacta 400
P. copiapina 109, 131
P. dasylirioides 32, 281, 316, 317, 318, 319,
327, 400
P. ferruginea 101, 109, 246, 261, 592, 599
P. floccosa 98, 109, 131, 400, 466, 592, 603
P. gigas 592, 605
P. hamata 333, 334, 592, 598
P. harmsii 93, 469
P. hofstenii 96
P. lasiopoda 469, 592, 599
P. lilloi 469
P. longistyla 593
P. mariae 52
P. medica 593, 603
P. mirabilis 236, 261
P. nutans 400
P. oxyantha 593, 599
P. petropolitana 608
P. pusilla 31, 45
P. subgenus Puya 261
P. subgenus Puyopsis 261
P. pyramidata 593, 599
P. raimondii 25, 36, 45, 47, 88, 218, 276, 332,
587, 593, 597, 600, 602, 607, 611
P. sodiroana 400, 593, 598, 599, 603
P. spathacea 265, 267
P. tuberosa 43, 47, 468
P. venusta 261
P. aff. vestita 333, 334
P. weberbaueri 469, 593, 599, 601, 602, 605,
607
Puyeae 469, 471
Pyrrhocoridae 410
Quercus 340
Q. virginiana 207, 216, 310, 344, 374, 378,
380, 381, 399
Quesnelia 14, 57, 115, 262, 276, 296, 308,
328, 341, 386, 397, 478, 516, 525, 533,
535, 536, 537, 538
Q. arvensis 298, 299
Q. centralis 85
Q. humilis 293, 298, 299
Q. lateralis 85, 265, 266, 273
Q. liboniana 273
Q. quesneliana 156, 406
Q. testudo 292, 293, 298, 299, 308, 323
Racinaea 14, 247, 555, 558, 564, 565, 569,
573, 574, 585; see also Tillandsia
subgenus Pseudocatopsis
R. commixa 564
R. insularis 480
R. multiflora 585
R. pallidoflavens 566
R. pendulispica 585
R. seemannii 573, 585
R. tetrantha 585
var. tetrantha 574
R. undulifolia 585
Taxon index
Rahnella 211
Rapateaceae 478, 489, 522, 523, 524, 525,
526, 528
Regelia 545, 546; see also Aregelia
Restionaceae 523
Rhinotermitinae 437
Rhizobium 209
Rhizoctonia 377
Rhizoecus falcifer 408
Rhizophora mangle 7, 198, 310, 311, 345
Rhopornis ardesiaca 416
Riodinidae 408, 564
Ripsalis 290
Ronnbergia 14, 34, 54, 98, 102, 115, 184,
389, 478, 479, 494, 517, 525, 533, 535,
536, 537, 538
R. deleonii 54, 90, 289
R. ecuadoriana 21
R. explodens 289
R. petersii 39, 73, 102
Rosaceae 488
Roridula gorgonias 208
Rubiaceae 340, 365
Rubus 325
Runchmia 220
Saissetta hemisphaerica 408
Salatoria 446
Salix 284
Sappho sparganura 267
Sarraceniaceae 223
Sarracenia flava 220
S. purpurea 226, 445
Schinus terebinthifolius 355
Schomburgkia tibicinis 428, 429, 430
Sciaridae 221
Scutellospora 210
Scydmaenidae 411
Selaginella arenicola 380
Senecio medley-woodii 174
Serenoa repens 602
Sesarma miersii 449
Sobralia 270
Solenopsis 220, 221, 425
Solidago 376
Spanish moss (see Tillandsia usneoides)
Spartina 328
Sphagnum 202
Staphylinidae 411
Statira denticulata 410
Stegolepis 525, 528, 530, 532, 533, 535, 536,
537
S. hitchcockii 524
Stelis 196
Steyerbromelia 14, 260, 394, 469, 470
S. diffusa 231
Streliziaceae 523
685
Streptocalyx 74, 479, 517
S. longifolius 347, 424, 435, 593
Streptocarpus 88
Strymon basilides 408
Symphyla 411
Syncope antenori 446
Syringa 476
Tachyphonus coronatus 294
Taxodium distichum 205, 259, 308, 310,
311, 312, 313, 314, 315, 321, 322, 341,
343
Tetramorium simillinum 430
Tettigonidae 430
Theobroma 211
T. cacao 205
Thraupis cyanoptera 416
T. ornata 416
Thysanura 430
Tillandsia 8, 12, 14, 24, 34, 41, 46, 48, 57,
60, 63, 64, 67, 76, 79, 81, 88, 89, 92, 94,
95, 96, 100, 103, 104, 122, 148, 149,
162, 163, 166, 173, 198, 199, 211, 218,
230, 234, 239, 244, 247, 248, 250, 252,
254, 255, 256, 257, 258, 265, 268, 269,
270, 271, 283, 285, 305, 306, 315, 319,
322, 323, 325, 328, 331, 335, 336, 340,
341, 342, 343, 348, 356, 357, 360, 365,
366, 368, 374, 380, 384, 385, 386, 387,
388, 391, 394, 395, 396, 397, 398, 399,
412, 420, 423, 451, 460, 461, 464, 465,
466, 481, 482, 483, 484, 487, 491, 493,
495, 496, 503, 504, 505, 507, 508, 509,
510, 512, 513, 515, 516, 518, 525, 527,
528, 529, 531, 532, 533, 535, 536, 537,
540, 555, 558, 559, 560, 561, 562, 563,
564, 565, 568, 569, 571, 573–85, 588,
594, 597, 602, 604, 605, 606, 611, 612,
613, 614, 619
T. achyrostachys 150, 164, 252
T. acosta-solisii 511, 512
T. adpressa 364
T. adpressiflora 136
var. tonduziana 371
T. aequatorialis 249
T. aeranthos 242, 377, 507, 559, 580, 613
T. aizoides 268, 505, 573, 574
T. alberi 507, 508, 580
T. albertiana 83, 91, 270, 560, 573, 578,
609
T. subgenus Allardtia 92, 94, 248, 505, 509,
510, 528, 529, 558, 562, 569, 574, 575,
576, 577, 578–9, 580, 582, 583, 584
T. anceps 134, 358, 360, 370, 511, 512, 563
T. andreana 562
T. andrieuxii 250, 270
T. angulosa 491, 577
686
Taxon index
T. subgenus Anoplophytum 86, 92, 94, 254,
268, 480, 492, 505, 507, 508, 509, 510,
513, 514, 528, 529, 558, 561, 564, 566,
569, 574, 575, 578, 579–80, 581, 582
T. araujei 20, 25, 43, 331, 390, 580
T. arequitae 579
T. argentea 83, 246, 565, 614; see also T.
fuchsii
T. argentina 579
T. arhiza 391, 396, 511, 512
T. asplundii 212
T. atroviridipetala 583
T. aurea 511, 512, 581
T. australis 573
T. badensis 511, 512
T. bagua-grandensis 579
T. balbisiana 65, 86, 88, 122, 194, 210, 241,
242, 253, 279, 284, 321, 342, 356, 380,
399, 408, 424, 429, 433, 482
T. baileyi 198, 433, 559, 614
T. baliophylla 584
T. bartramii 210, 211, 337
T. benthamiana 593, 604
T. bergeri 528, 529, 530, 532, 556, 580, 613
T. bermejoensis 579
T. biflora 135, 306, 593, 599, 605
T. brachycaulos 86, 345, 613, 614
3 T. balbisiana 248
3 T. bulbosa 248
3 T. capitata 248
3 T. caput-medusae 248
3 T. foliosa 248
3 T. ionantha 248
3 T. mirabilis 248
T. brachyphylla 394, 580, 613, 615
T. bryoides 20, 26, 43, 62, 63, 238, 503, 527,
567, 573, 581, 582
T. buchlohii 579
T. bulbosa 26, 53, 64, 76, 144, 153, 178, 211,
277, 356, 369, 370, 423, 427, 428, 429,
433, 613, 615
T. burlemarxii 580
T. butzii 153, 218, 427, 428, 613, 614
T. cacticola 511, 512, 574, 581
T. caerulea 270, 356, 511, 512, 513
T. calcicola 393
T. camargoensis 579
T. candida 579, 580
T. capillaris 49, 250, 373, 491, 492, 527, 573,
593, 604
f. hieronymi 491
T. capitata 86, 182, 252, 564, 573
T. caput-medusae 71, 176, 189, 198, 215,
218, 277, 427, 428, 613, 614, 615
T. cardenasii 578
T. carlsoniae 270, 573, 593
T. carminea 580
T. carnosa 583
T. castellanii 90, 491, 556, 577
T. caulescens 579
T. cauligera 573, 578
T. cernua 339
T. chaetophylla 612
T. chapeuensis 580
T. chartacea 593, 599
T. chiapensis 610
T. chiletensis 579, 580
T. churinensis 578
T. circinnatoides 145, 211, 212
T. clavigrea 319, 573
T. cochabambae 578
T. colganii 580
T. comarapaensis 580
T. complanata 34, 85, 134, 135, 186, 270,
343, 394, 466, 488, 524, 528, 529, 530,
532, 561, 564, 574, 577, 593, 598
T. concolor 20, 65, 145, 252
T. confinis 339
T. cornuta 511, 512, 513
T. cotagaitensis 578, 579, 581, 582
T. crocata 26, 29, 71, 72, 250, 511, 512, 581
T. cyanea 83, 511, 512, 559
T. dasyliriifolia 198, 278, 279, 342, 387, 388,
399, 593
T. denudata var. vivipara 574
T. deppeana 57, 59, 137, 139, 141, 142, 151,
154, 182, 253, 254, 286, 287, 305, 384,
408, 499, 502
T. dexteri 610
T. diaguitensis 28, 578, 580
T. subgenus Diaphoranthema 28, 86, 94, 99,
136, 162, 238, 252, 253, 254, 268, 281,
480, 482, 491, 492, 505, 506, 507, 508,
509, 510, 513, 527, 528, 529, 559, 560,
561, 567, 568, 571, 574, 575, 577, 581–2
T. didisticha 356, 580, 583
T. dodsonii 87, 270, 511, 512, 513, 528, 530,
532
T. dorotheae 580
T. duidae 579
T. duratii 29, 49, 162, 246, 267, 373, 503,
511, 512, 561–2, 581
T. dyeriana 511, 512, 513
T. ecarinata 583
T. edithiae 33
T. elongata 121
T. eltoniana 579, 580
T. emergens 339
T. erecta 505, 577
T. erinata 393
T. erubescens 250, 270, 593, 598
T. espinosa 560
T. esseriana 580, 581
T. exserta 611
Taxon index
T. fasciculata xiii, 29, 146, 150, 151, 156,
157, 158, 159, 253, 285, 286, 295, 303,
307, 321, 322, 336, 337, 342, 356, 380,
393, 399, 412, 424, 480, 564, 567, 573,
589, 593, 599
3 T. foliosa 248
3 T. lieboldiana 248
T. fendleri 120, 134, 573
T. ferreyrae 583, 612
T. festucoides 198
T. filifolia 26, 145, 583
T. flabellata 167, 182, 410
3 T. tricolor
3 Vriesea incurvata 248
T. flexuosa 30, 73, 89, 198, 253, 325, 337,
338, 346, 362, 423, 433, 458, 574
T. floribunda 356
T. fraseri 528, 530, 532
T. friesii 492, 507, 508, 579, 580
T. fuchsii 562, 573, 583, 613
T. funckiana 26, 528, 530, 531, 532, 565,
578, 583
T. gardneri 145, 249, 579, 580
T. geissei 580
T. genseri 580
T. germiniflora 90, 528, 529, 530, 532, 559,
579, 580
T. gilliesii 593, 605
T. globosa 580
T. grandis 88, 270, 308, 395, 573, 584
T. grazielae 395, 580, 609, 613
T. guasamayensis 580
T. guatemalensis 593
T. guelzii 580
T. hamaleana 511, 512, 521, 562, 565
T. harrisii 620
T. hasei 580
T. heterophylla 59, 86, 136, 251, 254, 501,
584
T. heubergeri 580
T. hildae 26, 47, 73
T. hirtzii 615
T. horstii 580
T. huarazensis 577
T. humilis 511, 512, 581
T. hutchisonii 579
T. ignesiae 583
T. imperialis 81, 91, 253, 255, 281, 362,
583
T. incarnata 578, 581, 593, 605, 606, 607
T. incurva 564
T. insignis 498
T. ionochroma 285, 286, 303, 305, 306, 396,
593, 599, 601, 605
T. ionantha 20, 26, 27, 29, 47, 48, 65, 116,
149, 153, 166, 175, 253, 270, 281, 282,
283, 507, 562, 577, 613, 614
687
var. ionantha 49
3 T. schiedeana 248
var. scaposa 614
var. van-hyningii 49
var. zebrina 29
T. ixioides 564, 579, 580
T. jalisco-monticola 3 T. xerographica 248
T. jucunda 580
T. juncea 480, 504, 560, 578, 583, 585, 593,
613, 614
T. juncunda 579, 580
T. kammii 620
T. karwinskyana 26, 72, 76, 145, 150, 164,
178, 307
T. kautskyi 580, 620
T. kirchhoffiana 252
T. klausii 611
T. koehresiana 580
T. kolbii 613, 614
T. krukoffiana 248, 252, 319
T. kurt-horstii 178, 330, 496
T. lampropoda 593
T. landbeckii 491
T. latifolia 49, 325, 395, 559, 574, 578
var. divaricata 356
var. major 325
var. minor 325
var. vivipara 395
T. laxissima 511, 512
T. leiboldiana 185–6, 360, 491, 577
T. leonamiana 580
T. lepidosepala 254, 583
T. lindenii 511, 512, 556
T. linearis 94, 580, 581
T. loliacea 83, 491
T. lorentziana 267, 579, 580
T. lotteae 580
T. lucida 23
T. lymanii 583
T. macdougallii 49, 265, 270
T. maculata 593, 605
T. magnusiana 612
T. makoyana 307, 560
T. malzinei 563
T. marnier-lapostollei 573
T. matudae 252
T. mauryana 581, 583, 620
T. maxima 593, 599
T. mellemonti 511, 512
T. milagrensis 580
T. mima var. chiletensis 574
T. monadelpha 134, 496, 511, 512, 566, 574,
581
T. monstrum 85
T. montana 580
T. muhriae 507, 508, 580
T. muhrii 578
688
Taxon index
T. multicaulis 34, 85, 150, 164, 254, 561,
564, 574
T. multiflora 564
T. myosura 28, 250, 491
T. narthecioides 511, 512, 574, 581, 583, 585,
612
T. neglecta 393, 580
T. nubis 511, 512
T. nuptialis 580
T. oaxacana 614
T. organensis 580
T. orogenes 593
T. oropezana 580
T. oroyensis 593, 599
T. pabstiana (5 V. drepanocarpa) 96, 247
T. paleacea 28, 175, 325, 395, 511, 512, 513
T. paniculata 584
T. paraensis 565
T. parryi 250
T. paucifolia xiii, 9, 20, 47, 65, 89, 122, 153,
191, 193, 194, 197, 198, 205, 233, 241,
242, 252, 259, 278, 279, 285, 287, 303,
304, 308, 309, 310, 311, 312, 313, 314,
315, 316, 317, 318, 321, 322, 325, 327,
328, 343, 345, 346, 349, 350, 351, 356,
358, 365, 368, 377, 432, 480
subsp. schubertii 574
T. pedicellata 505, 569
T. peiranoi 505, 511, 512, 580
T. pentasticha 582
T. pfeufferi 580
T. subgenus Phytarrhiza 94, 95, 254, 268,
480, 492, 505, 506, 507, 508, 509, 510,
511, 512, 513, 528, 529, 558, 560, 562,
565, 574, 575, 577, 580–1, 582
T. plagiotropica 583
T. platyphylla 583
T. platyrhachis 511, 512
T. plumosa 271, 583
T. pohliana 237, 238, 579, 580
T. 3 polita 556
T. polystachia 277, 338, 573, 577
T. ponderosa 253, 593
T. pretiosa 511, 512
T. pringlei (see T. utriculata var. pringlei)
T. prodigiosa 277
T. propagulifera 574
T. pruinosa 77, 285, 337, 362
T. subgenus Pseudalcantarea 247, 256, 505,
509, 510, 559, 569, 575, 576, 578, 584
T. pseudobaileyi (see T. baileyi)
T. pseudocardenasii 578
T. subgenus Pseudocatopsis (5 Racinaea)
505, 509, 510, 513, 528, 529, 573, 578,
585
T. pseudomacbrideana 578
T. pseudomicans 578
T. pseudomontana 580
T. pucaraensis 580
T. punctata 249, 251
T. punctulata 86, 251, 252, 367, 412, 574,
587
3 T. kirchoffiana 248
T. purpurea 175, 395, 511, 512, 563, 574,
581, 593, 606, 609, 611
T. pyramidata 574
T. ramellae 580
T. rauhii 319, 583, 584
T. reclinata 395, 580
T. recurvata 9, 20, 28, 29, 99, 122, 149, 165,
175, 207, 212, 241, 242, 250, 253, 281,
282, 283, 322, 330, 336, 337, 338, 339,
344, 346, 356, 362, 372, 374, 377, 378,
399, 482, 505, 577, 582, 594, 598, 599,
604, 609
T. recurvifolia 580
T. reichenbachii 505, 511, 512, 581
T. retorta 577, 582
T. rodrigueziana 594
T. roland-gosselinii 251
T. roseiflora 580
T. rubella 594, 599
T. rupicola 511, 512
T. scaligera 511, 512, 577
T. schiedeana 47, 65, 166, 167, 172, 173, 198,
211, 270, 482, 594, 604, 612
T. secunda 81, 323, 528, 530, 532, 559, 565,
578
var. vivipara 574
T. seideliana 580
T. seleriana 251, 427, 594
T. selleana 577
T. setacea 29, 285, 336, 338, 573
T. simulata 338
T. skunkei 511, 512
T. 3 smalliana 321
T. 3 smallii 338
T. somnians 559, 574
T. sphaerocephala 285, 286, 303, 306, 396,
594, 599, 601, 605, 608
T. spiraliflora 573, 583, 584
T. sprengeliana 580, 620
T. straminea 356, 510, 511, 512, 567, 581
T. streptocarpa 83, 392, 396, 505, 511, 512,
580, 581
T. streptophylla 7, 39, 165, 189, 251, 345,
423, 429, 433, 594, 599, 608, 615
T. stricta 249, 277, 298, 301, 363, 387, 388,
397, 399, 507, 573, 580, 615
T. sucrei 393, 579, 580, 609, 620
T. sueae 250
T. tectorum 27, 72, 77, 145, 153, 175, 396,
482, 574, 578, 611, 613
T. tenuifolia 330, 344, 507, 579, 580
Taxon index
T. teres 583
T. tetrantha 612
T. thiekenii 393, 580
T. subgenus Tillandsia 86, 91, 92, 248, 249,
251, 252, 253, 254, 255, 276, 281, 504,
505, 509, 510, 529, 557, 559, 561, 562,
565, 566, 567, 568, 574, 575, 576, 577,
578, 582–4
T. toropiensis 580
T. tortilis 254, 583
T. tricholepsis 49, 528, 529, 530, 532
T. tricolor 559, 613
T. triglochinoides 511, 512, 581
T. truxillana 578
T. turneri 270, 388
T. umbellata 491, 511, 512
T. undulatobracteata 579
T. usneoides 20, 25, 26, 28, 29, 43, 46, 53, 62,
65, 81, 99, 107, 109, 117, 118, 120, 143,
144, 146, 149, 160, 162, 163, 165, 167,
168, 172, 173, 174, 192, 194, 201, 230,
232, 238, 241, 242, 243, 253, 270, 282,
285, 321, 322, 334, 336, 344, 349, 351,
372, 373, 374, 381, 395, 413, 416, 480,
482, 503, 505, 506, 518, 527, 559, 562,
563, 568, 569, 582, 587, 588, 590, 594,
595, 597, 604, 605, 606, 607
T. utriculata 119, 121, 149, 177, 178, 189,
241, 242, 246, 250, 253, 259, 277, 281,
282, 285, 286, 303, 305, 306, 308, 322,
323, 326, 327, 328, 336, 369, 380, 393,
399, 412, 436, 443, 445, 446, 447, 448,
528, 530, 532, 560, 563, 578, 583, 589,
594, 599
var. pringlei 307
var. utriculata 307, 574
T. valenzuelana 173
T. variabilis 148, 338
T. venusta 511, 512
T. vernicosa 580
T. violacea 594
T. virescens 268, 491
T. viridiflora 83, 185, 256, 521, 584, 585
T. wagneriana 511, 512, 513, 578, 581, 583,
584
T. walter-richteri 580
T. walteri 577
T. werdermanii 175
T. xerographica 503, 613, 614, 615, 620
T. xiphioides 83, 91, 94, 267, 268, 507, 573,
578, 579, 580, 594, 604, 615
var. lutea 580
T. yuncharaensis 578, 580
T. zecheri 578
var. cafayatensis 507, 508
Tillandsioideae 12, 20, 29, 31, 32, 34, 37, 39,
43, 44, 46, 48, 49, 50, 52, 53, 54, 55, 57,
689
58, 63, 64, 67, 70, 71, 72, 73, 74, 75, 76,
77, 79, 81, 83, 86, 88, 89, 91, 92, 94, 96,
97, 98, 100, 101, 102, 103–4, 105, 107,
109, 112, 113, 114, 115, 118, 133, 134,
135, 136, 137, 143, 150, 151, 162, 163,
164, 168, 178, 187, 197, 198, 200, 218,
224, 229, 230, 231, 232, 234, 235, 238,
239, 240, 245, 247–57, 260, 261, 262,
263, 265, 267, 269, 277, 278, 284–7,
288, 295, 296, 298, 299, 301, 338, 339,
346, 354, 356, 357, 369, 385, 386, 387,
388, 390, 391, 393, 395, 398, 406, 408,
415, 424, 427, 428, 431, 438, 464, 466,
469, 470, 472, 476, 477, 480–2, 483,
486, 487, 488, 491, 492, 493, 494, 495,
496, 497, 498, 499, 500, 501, 502, 503,
504, 506, 508, 509, 514, 516, 518, 521,
522, 525, 526, 527–36, 540, 555–71,
575, 576, 588, 604
Tnethecoris distinctus 410
Tococa 347
Toxorhynchites haemorrhoidalis 449
Troglodytes ochraceus 416
Tracheophyta 475
Tremarctos ornatus 599
Trombidiidae 411
Tylenchocriconema alleni 410
Typha 328
Typhaceae 523, 524
Typhales 522
Uredo nidulaari 413
Ursulaea 14
Utricularia 219, 224, 367
U. humboldtii 419, 439
U. nelumbifolia 439
U. reniformis 439
Vellozia 391, 521
Velloziaceae 391, 437, 488, 522
Velloziales 522
Vibrio 211
Vireya 618
Vriesea 11, 12, 14, 30, 31, 54, 57, 79, 94, 95,
96, 247, 254, 255, 256, 257, 258, 265,
267, 276, 277, 298, 325, 331, 335, 336,
341, 357, 358, 360, 385, 387, 397, 418,
420, 439, 451, 464, 480, 487, 495, 508,
509, 510, 516, 521, 525, 528, 529, 531,
532, 533, 535, 536, 537, 540, 555, 558,
559, 561, 562, 563, 564, 565, 568, 569,
571, 573, 577, 578, 579, 588, 604
V. subgenus Alcantarea 104, 256, 257, 509,
510
V. amazonica 120, 175, 364
V. atra 87, 246, 439, 531
var. atra 266
690
Taxon index
V. attomacaensis 273
V. bituminosa 55, 81, 87, 256, 567
var. bituminosa 273
V. carinata 164, 246, 255, 257, 335, 336, 355
V. cereicola 394
V. chontalensis 371
V. comata 371
V. corcovadensis 335
V. crassa 439
V. cylindrica 86, 87
V. drepanocarpa 96, 247
V. ensiformis 355, 394
V. erythrodactylon 38, 55, 255, 454
V. espinosae 47, 356, 524, 528, 530, 531, 532
V. fenestralis 136, 559
V. fosteriana 33, 35, 54, 182, 184, 185, 413,
454, 456, 559, 611
V. fosteriana chestnut 54, 56
V. friburgensis 267
V. geniculata 137, 139, 141, 145, 499, 502,
503
V. gigantea 7, 189, 256
V. gladioliflora 528, 530, 532
V. glutinosa 89, 528, 530, 532
V. guttata 335
V. haematina 266, 273, 300
V. hainesiorum 255
V. heliconioides 358, 359, 360
V. heterandra 369, 370, 565
V. heterostachys 273
V. hieroglyphica 184, 237, 413, 456, 611, 620
V. hydrophora 81, 86, 87, 266, 273
V. imperialis 555, 574, 578, 579
V. incurvata 148, 255, 355, 371
V. inflata 246, 336
V. irazuensis 135
V. jonghei 120, 134, 236, 255, 355
V. leucophylla 255
V. longicaulis 273, 336
V. longiscapa 255, 273
V. macrostachya 211
V. malzinei 69, 524, 528, 530, 531, 532
V. minuta 263
V. neoglutinosa 254, 266, 316, 319, 397, 398
V. oligantha 81, 83, 391
V. paralbica 273
V. philippo-coburgii 237, 238, 255, 323
V. platynema 136, 182, 195, 196, 210, 216,
263, 383, 466
V. psittacina 257
V. regnellii 255
V. ringens 212
V. rodigasiana 356
V. sazimae 256
V. scalaris 100, 300, 310
V. schwackeana 489
V. simplex 54, 109, 134, 185, 556
3 ‘Mariae’ 273
V. sparsiflora var. sparsiflora 273
V. splendens 185, 210, 270, 369, 370, 456,
527, 528, 530, 532
var. formosa 54
var. splendens 54
V. splitgerberi 120
V. triligulata 528, 530, 532
V. unilateralis 255
V. vagans 273, 336
V. vietoris 255
V. viridiflora 528, 530, 532
V. vittata 528, 530, 532
V. subgenus Vriesea 509, 510, 527, 528, 556,
558, 566, 574, 576, 578, 582, 583
V. werckleana 594
V. section Xiphion 255, 256, 257, 268, 527,
528, 530, 531, 558, 562, 567; see also
Werauhia
Wasmania auropunctata 430
Weberocereus glaber 365, 366
Werauhia 14, 255, 257, 555, 558, 562, 564,
565, 566, 569, 576
W. attenuata 371
W. gigantea 556
W. gladioliflora 246, 424, 562, 565
W. section Jutleya 558
W. sanguinolenta 356
W. tarmaensis 565
W. section Werauhia 558
Whitesloania crassa 619
Wittrockia 14, 55, 294, 371, 480, 525, 533,
536, 537, 538, 545
W. campos-portoi 108
W. superba 263, 279, 301, 355
Wyeomyia 220, 221, 441
W. medioalbipes 447
W. mitchellii 445
W. smithii 445
W. vanduzeei 445, 447
Xanthium 119
Xenochalepus omogerus 410
Zingiberaceae 89, 523
Zingiberiflorae 522, 523
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