Phoretic Behaviour of Bromeliad Annelids (<Emphasis Type="Italic">Dero</Emphasis>) and Ostracods (<Emphasis Type="Italic">Elpidium</Emphasis>) using Frogs and Lizards as Dispersal Vectors

The phoretic behaviour of ostracods (Elpidium bromeliarum) andannelids (Dero superterrenus) that inhabit tank bromeliads was studied. Our previous field observations had shown that bromeliad ostracods can be found attached to the skin of amphibians and reptiles that move among bromeliads, probably allowing the ostracods to colonise new tanks. In this paper, we present the first record of bromeliad annelids found attached to frogs moving among bromeliads in the field. We have also enlarged the database on bromeliad ostracods engaged in phoretic association with terrestrial vertebrates in three locations in southeastern Brazil. In our laboratory experiments bromeliad annelids show a strong significant tendency to climb onto papers that had been in contact with frog skin when compared with control papers, indicating a kind of chemically oriented behaviour. Bromeliad ostracods, on the other hand, attached themselves to treated and untreated papers with same frequency. When brought into contact with various species of frogs and lizards, the bromeliad annelids and ostracods both presented preference to attach themselves to frogs, but the annelids showed a stronger preference to attach to frogs and to avoid attachment to lizards. Another experiment demonstrated that bromeliad annelids are much more prone to dehydration than are ostracods. We suggest that the chemically oriented behaviour presented by bromeliad annelids toward frogs could diminish the risk of death by dehydration during the transport among bromeliads due to the moist characteristic of frog skins.     

Calling site selection by the bromeliad-dwelling treefrog Phyllodytes melanomystax (Amphibia: Anura: Hylidae) in a coastal sand dune habitat

We studied bromeliad selection by calling males of Phyllodytes melanomystax. The study site was a restinga environment in the northeastern state of Bahia, northeastern Brazil. We sampled 202 bromeliads, 101 with and 101 without calling males. We used multiple logistic regression analysis and Wald test to identify which of nine environmental variables investigated could explain the occurrence of calling males within bromeliads. The presence/absence of calling males in bromeliads was influenced by the number of bromeliads in a 2 m radius and the amount of debris inside the rosettes, while physical variables of bromeliads and the volume of stored water inside their rosettes had no influence. The mark-recapture procedure of P. melanomystax revealed site fidelity. This study is the first to explain the pattern of bromeliad selection by a species of the bromeliad-dwelling frog genus Phyllodytes.     

Dispersal barriers and climate determine the geographic distribution of the helicopter damselfly Mecistogaster modesta

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Selecting a Hiding Place: Anuran Diversity and the use of Bromeliads in a Threatened Coastal Sand Dune Habitat in Brazil

Among vertebrates, anuran amphibians represent the highest number of species associated with bromeliads and possess a range of ecological, behavioral, and morphological specializations to life in these plants. Despite the importance of bromeliads as biodiversity amplifiers, and their diversity in some habitats, studies of the relationship between anurans and these plants are scarce in Brazil. Here, we investigated the way anurans select and use bromeliads in a threatened coastal habitat. We analyzed data from 23 standardized samples of the anurans associated with the bromeliad Neoregelia cruenta in the Restinga de Maricá, State of Rio de Janeiro, Southeastern Brazil. We found nine anuran species using these bromeliads, representing the highest richness reported for a Brazilian restinga. We identified a general pattern of bromeliad usage, where plants located at the edges of scrub patches (exposed to the sun) were more frequently occupied by anurans than those located more to the center (in the shade). There is strong evidence of an active selective process based on the quality of the water stored in the rosette, which differs between plants depending on their position in the scrub patch. Although the number of individuals varied during the period of study, the frequency of bromeliads used was constant, indicating that plant occupation follows a regular pattern throughout the year. Furthermore, the high frequency of bromeliads used by anurans during the whole year highlights the importance of considering these plants in developing conservation programs concerning the protection of anurans.     

Precipitation Constrains Amphibian Chytrid Fungus Infection Rates in a Terrestrial Frog Assemblage in Jamaica,West Indies

We model Batrachochytrium dendrobatidis (Bd) infection rates in Jamaican frogs—one of the most threatened amphibian fauna in the world. The majority of species we surveyed were terrestrial direct‐developing frogs or frogs that breed in tank bromeliads, rather than those that use permanent water bodies to breed. Thus, we were able to investigate the climatic correlates of Bd infection in a frog assemblage that does not rely on permanent water bodies. We sampled frogs for Bd across all of the major habitat types on the island, used machine learning algorithms to identify climatic variables that are correlated with infection rates, and extrapolated infection rates across the island. We compared the effectiveness of the machine learning algorithms for species distribution modeling in the context of our study, and found that infection rate rose quickly with precipitation in the driest month. Infection rates also increased with mean temperature in the warmest quarter until 22 °C, and remained relatively level thereafter. Both of these results are in accordance with previous studies of the physiology of Bd. Based on our environmental results, we suggest that frogs occupying high‐precipitation habitats with cool rainy‐season temperatures, though zcurrently experiencing low frequencies of infection, may experience an increase in infection rates as global warming increases temperatures in their habitat.     

Ecosystem services provided by bromeliad plants: A systematic review

The unprecedented loss of biological diversity has negative impacts on ecosystems and the associated benefits which they provide to humans. Bromeliads have high diversity throughout the Neotropics, but they have been negatively affected by habitat loss and fragmentation, climate change, invasive species, and commercialization for ornamental purpose. These plants provide direct benefits to the human society, and they also form microecosystems in which accumulated water and nutrients support the communities of aquatic and terrestrial species, thus maintaining local diversity. We performed a systematic review of the contribution of bromeliads to ecosystem services across their native geographical distribution. We showed that bromeliads provide a range of ecosystem services such as maintenance of biodiversity, community structure, nutrient cycling, and the provisioning of food and water. Moreover, bromeliads can regulate the spread of diseases, and water and carbon cycling, and they have the potential to become important sources of chemical and pharmaceutical products. The majority of this research was performed in Brazil, but future research from other Neotropical countries with a high diversity of bromeliads would fill the current knowledge gaps and increase the generality of these findings. This systematic review identified that future research should focus on provisioning, regulating, and cultural services that have been currently overlooked. This would enhance our understanding of how bromeliad diversity contributes to human welfare, and the negative consequences that loss of bromeliad plants can have on communities of other species and the healthy functioning of the entire ecosystems.     

Two coexisting tank bromeliads host distinct algal communities on a tropical inselberg

The tank bromeliads Aechmea aquilega (Salisb.) and Catopsis berteroniana (Schultes f.) coexist on a sun‐exposed Neotropical inselberg in French Guiana, where they permit conspicuous freshwater pools to form that differ in size, complexity and detritus content. We sampled the algal communities (both eukaryotic and cyanobacterial taxa, including colourless forms) inhabiting either A. aquilega (n = 31) or C. berteroniana (n = 30) and examined differences in community composition and biomass patterns in relation to several biotic and abiotic variables. Chlorella sp. and Bumilleriopsis sp. were the most common taxa and dominated the algal biomass in A. aquilega and C. berteroniana, respectively. Using a redundancy analysis, we found that water volume, habitat complexity and the density of phagotrophic protozoa and collector‐gatherer invertebrates were the main factors explaining the distribution of the algal taxa among the samples. Hierarchical clustering procedures based on abundance and presence/absence data clearly segregated the samples according to bromeliad species, revealing that the algal communities in the smaller bromeliad species were not a subset of the communities found in the larger bromeliad species. We conclude that, even though two coexisting tank bromeliad populations create adjacent aquatic habitats, each population hosts a distinct algal community. Hence, bromeliad diversity is thought to promote the local diversity of freshwater algae in the Neotropics.     

Tank bromeliad transplants as an enrichment strategy in southern Costa Rica

Epiphytes represent up to 50% of all vascular plant species in neotropical forests but they are among the slowest plants to recolonize regenerating ecosystems. This discrepancy underlines the need for restoration ecologists to learn how to assist the colonization of organisms in this key functional group. Transplanting tank bromeliads (i.e. bromeliads featuring overlapping leaves that form a water impounding rosette) could be a good approach in the neotropics, where abundant, fallen bromeliads can be sustainably collected from the forest floor. Moreover, tank bromeliads could accelerate restoration processes by providing relatively stable microenvironments for invertebrates, thus helping them resist severe drought and high temperatures, such as predicted in light of many climate change models. We transplanted 60 individuals of the tank bromeliad Werauhia gladioliflora onto trunks and branches of comparable size and orientation on three host tree species. The study took place in three long‐term restoration plantations located in a tropical premontane rainforest zone in southern Costa Rica. Transplant survivorship after 9 months varied among sites, from 65 to 95%. Transplants hosted twice as many arthropod orders as untreated control branches, and they buffered microclimates during the driest (+1.7 to 19.7% relative humidity) and warmest (?0.5 to 5.0°C) times of the day. Our results suggest that bromeliad transplantation is a cost‐effective (circa Epiphytes represent up to 50% of all vascular plant species in neotropical forests but they are among the slowest plants to recolonize regenerating ecosystems. This discrepancy underlines the need for restoration ecologists to learn how to assist the colonization of organisms in this key functional group. Transplanting tank bromeliads (i.e. bromeliads featuring overlapping leaves that form a water impounding rosette) could be a good approach in the neotropics, where abundant, fallen bromeliads can be sustainably collected from the forest floor. Moreover, tank bromeliads could accelerate restoration processes by providing relatively stable microenvironments for invertebrates, thus helping them resist severe drought and high temperatures, such as predicted in light of many climate change models. We transplanted 60 individuals of the tank bromeliad Werauhia gladioliflora onto trunks and branches of comparable size and orientation on three host tree species. The study took place in three long‐term restoration plantations located in a tropical premontane rainforest zone in southern Costa Rica. Transplant survivorship after 9 months varied among sites, from 65 to 95%. Transplants hosted twice as many arthropod orders as untreated control branches, and they buffered microclimates during the driest (+1.7 to 19.7% relative humidity) and warmest (?0.5 to 5.0°C) times of the day. Our results suggest that bromeliad transplantation is a cost‐effective (circa $0.5 USD/successful transplant) strategy to assist the recovery of epiphyte diversity in forest restoration sites with minimal impact on source populations. Longer‐term studies are needed to test this strategy for other epiphyte families or for mixed‐taxa assemblages found on fallen branches.     

Mutualism influences species distribution predictions for a bromeliad‐breeding anuran under climate change

Ecological niche models, or species distribution models, have been widely used to identify potentially suitable areas for species in future climate change scenarios. However, there are inherent errors to these models due to their inability to evaluate species occurrence influenced by non‐climatic factors. With the intuit to improve the modelling predictions for a bromeliad‐breeding treefrog (Phyllodytes melanomystax, Hylidae), we investigate how the climatic suitability of bromeliads influences the distribution model for the treefrog in the context of baseline and 2050 climate change scenarios. We used point occurrence data on the frog and the bromeliad (Vriesea procera, Bromeliaceae) to generate their predicted distributions based on baseline and 2050 climates. Using a consensus of five algorithms, we compared the accuracy of the models and the geographic predictions for the frog generated from two modelling procedures: (i) a climate‐only model for P. melanomystax and V. procera; and (ii) a climate‐biotic model for P. melanomystax, in which the climatic suitability of the bromeliad was jointly considered with the climatic variables. Both modelling approaches generated strong and similar predictive power for P. melanomystax, yet climate‐biotic modelling generated more concise predictions, particularly for the year 2050. Specifically, because the predicted area of the bromeliad overlaps with the predictions for the treefrog in the baseline climate, both modelling approaches produce reasonable similar predicted areas for the anuran. Alternatively, due to the predicted loss of northern climatically suitable areas for the bromeliad by 2050, only the climate‐biotic models provide evidence that northern populations of P. melanomystax will likely be negatively affected by 2050.     

Geographic Range,Habitats, and Host Plants of Bromeliad‐living Jumping Spiders (Salticidae)1

Although spiders are a very diverse group on vegetation, their associations with plants are poorly known. Some salticid species specifically use Bromeliaceae as host plants in some regions of South America. In this study, I report the geographic range of these spider‐bromeliad associations, and whether the spiders inhabit particular bromeliad species and vegetation types, as well as open areas or interior of forests. Nine salticid species were found to be associated with up to 23 bromeliad species in cerrados (savanna‐like vegetation), semideciduous and seasonal forests, coastal sand dune vegetation, restingas, inselbergs, highland forests, chacos, and rain forests at 47 localities in Brazil, Paraguay, Bolivia, and Argentina. Some species were typically specialists, inhabiting almost exclusively one bromeliad species over a large geographic range (e.g., Psecas chapoda on Bromelia balansae), whereas others were generalists, occurring on up to 7–8 bromeliad species (e.g., Psecas sp., Eustiromastix nativo, and Coryphasia sp. 1). The regional availability of bromeliad species among habitats may explain this pattern of host plant use. More jumping spiders were found on bromeliads in open areas than on bromeliads in the interior of forests. These results show that several jumping spider species may be strictly associated with the Bromeliaceae in the Neotropics. This is one of the few studies to show host‐specific associations for spiders on a particular plant type over a wide geographic range.     

Host bromeliads and their associated frog species: Further considerations on the importance of species interactions for conservation

Bromeliads constitute a good example of symbiosis with organisms that spend their entire life cycle inside the plants, and often depend on them to breed. The bromeliads benefit from this interaction by increasing their nutrients intake. Conservation efforts tend to focus on a single endangered species, but in symbiotic associations, the viability of one species depends on that of the other. Based on IUCN criteria, any species that depends on another to complete its life cycle should be assigned a conservation status equivalent to that of the host taxon, where appropriate. We gathered published plus fieldwork data on the frog-bromeliad mutualism and compiled a checklist of 99 bromeligenous frogs species associated to 69 bromeliad hosts, and found threatened bromeliads hosting non-threatened frogs. We found that 62% bromeligenous frogs inhabit unspecified bromeliads. Finally, we propose strategies for improving understanding and conservation of the frog-bromeliad mutualism.     

Bottom-up regulation of bacterial growth in tropical phytotelm bromeliads

Evaluating the factors that regulate bacterial growth in natural ecosystems is a major goal of modern microbial ecology. Phytotelm bromeliads have been used as model ecosystems in aquatic ecology as they provide many independent replicates in a small area and often encompass a wide range of limnological conditions. However, as far as we know, there has been no attempt to evaluate the main regulatory factors of bacterial growth in these aquatic ecosystems. Here, we used field surveys to evaluate the main bottom-up factors that regulate bacterial growth in the accumulated water of tank bromeliads. Bacterial production, water temperature, water color, chlorophyll-a, and nutrient concentrations were determined for 147 different tank bromeliads in two different samplings. Bromeliad position and the season of sampling were also noted. Bacterial production was explained by ion ammonium concentration and water temperature, but the total variance explained was low (r ² = 0.104). Sampling period and bromeliad position were included in additional models that gave empirical support for predicting bacterial production. Bromeliad water tanks are extremely variable aquatic ecosystems in space (among bromeliads) and time (environmental conditions can change within hours), and it is well known that bacterial production responds rapidly to environmental change. Therefore, we concluded that several factors could independently regulate bacterial growth in phytotelm bromeliads depending on the characteristics of each bromeliad, such as location, amount of detritus, and ambient nutrient concentrations. A clear bottom-up limitation pattern of bacterial production in tropical phytotelm bromeliads was not found. Handling editor: Luigi Naselli-Flores     

Diversity and endemism of ciliates inhabiting Neotropical phytotelmata

While the diversity and distribution of macro-organisms living in phytotelmata (plant-container habitats) is well known, detailed taxonomic work on micro-organisms living in the same environments is limited. As a model clade of microbial eukaryotes, sampling of ciliates in Neotropical bromeliad tanks increased, and Neotropical phytotelmata such as bamboo stumps and tree holes were newly sampled. Thirty-three isolates from Brazil, Costa Rica, Dominican Republic, Jamaica and Mexico were sequenced for small subunit rDNA, and placed into a phylogenetic context using non-phytotelmata GenBank accessions. This and the morphological investigations discovered 45 undescribed, possibly endemic ciliate species. The potential endemics are from throughout most clades of the ciliate tree of life, and there is evidence of speciation within the Neotropical phytotelmata habitat. Our data show the number of potential Neotropical phytotelmata-endemic ciliate species increasing as more phytotelmata are sampled. While the new data show that the supposed endemics are mainly recruited from moss and ephemeral limnetic habitats, the bromeliad ciliate fauna is quite distinct from those of other limnetic habitats, lacking many typical and common freshwater genera, such as Coleps, Colpidium, Frontonia, Paramecium, Glaucoma, Nassula, Stylonychia and Trithigmostoma. There is no indication that specific ciliates are confined to specific bromeliads.     

Nitrogen fluxes from treefrogs to tank epiphytic bromeliads: an isotopic and physiological approach

Diverse invertebrate and vertebrate species live in association with plants of the large Neotropical family Bromeliaceae. Although previous studies have assumed that debris of associated organisms improves plant nutrition, so far little evidence supports this assumption. In this study we used isotopic (¹⁵N) and physiological methods to investigate if the treefrog Scinax hayii, which uses the tank epiphytic bromeliad Vriesea bituminosa as a diurnal shelter, contributes to host plant nutrition. In the field, bromeliads with frogs had higher stable N isotopic composition (δ¹⁵N) values than those without frogs. Similar results were obtained from a controlled greenhouse experiment. Linear mixing models showed that frog feces and dead termites used to simulate insects that eventually fall inside the bromeliad tank contributed, respectively, 27.7% (±0.07 SE) and 49.6% (±0.50 SE) of the total N of V. bituminosa. Net photosynthetic rate was higher in plants that received feces and termites than in controls; however, this effect was only detected in the rainy, but not in the dry season. These results demonstrate for the first time that vertebrates contribute to bromeliad nutrition, and that this benefit is seasonally restricted. Since amphibian–bromeliad associations occur in diverse habitats in South and Central America, this mechanism for deriving nutrients may be important in bromeliad systems throughout the Neotropics.     

Distribution and Flowering Ecology of Bromeliads along Two Climatically Contrasting Elevational Transects in the Bolivian Andes1

We compared the diversity, taxonomic composition, and pollination syndromes of bromeliad assemblages and the diversity and abundance of hummingbirds along two climatically contrasting elevational gradients in Bolivia. Elevational patterns of bromeliad species richness differed noticeably between transects. Along the continuously wet Carrasco transect, species richness peaked at mid‐elevations, whereas at Masicurí most species were found in the hot, semiarid lowlands. Bromeliad assemblages were dominated by large epiphytic tank bromeliads at Carrasco and by small epiphytic, atmospheric tillandsias at Masicurí. In contrast to the epiphytic taxa, terrestrial bromeliads showed similar distributions across both transects. At Carrasco, hummingbird‐pollination was the most common pollination mode, whereas at Masicurí most species were entomophilous. The proportion of ornithophilous species increased with elevation on both transects, whereas entomophily showed the opposite pattern. At Carrasco, the percentage of ornithophilous bromeliad species was significantly correlated with hummingbird abundance but not with hummingbird species richness. Bat‐pollination was linked to humid, tropical conditions in accordance with the high species richness of bats in tropical lowlands. At Carrasco, mixed hummingbird/bat‐pollination was found especially at mid‐elevations, i.e., on the transition between preferential bat‐pollination in the lowlands and preferential hummingbird‐pollination in the highlands. In conclusion, both richness patterns and pollination syndromes of bromeliad assemblages varied in distinct and readily interpretable ways in relation to environmental humidity and temperature, and bromeliad pollination syndromes appear to follow the elevational gradients exhibited by their pollinators.     

Environmental drivers of invertebrate population dynamics in Neotropical tank bromeliads

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Aquatic Microbial Habitats Within a Neotropical Rainforest: Bromeliads and pH-Associated Trends in Bacterial Diversity and Composition

Tank-forming bromeliads, suspended in the rainforest canopy, possess foliage arranged in compact rosettes capable of long-term retention of rainwater. This large and unique aquatic habitat is inhabited by microorganisms involved in the important decomposition of impounded material. Moreover, these communities are likely influenced by environmental factors such as pH, oxygen, and light. Bacterial community composition and diversity was determined for the tanks of several bromeliad species (Aechmea and Werauhia) from northern Costa Rica, which span a range of parameters, including tank morphology and pH. These were compared with a nearby forest soil sample, an artificial tank (amber bottle), and a commercially available species (Aechmea). Bacterial community diversity, as measured by 16S rRNA analysis and tRFLP, showed a significant positive correlation with tank pH. A majority of 16S rRNA bacterial phylotypes found in association with acidic bromeliad tanks of pH < 5.1 were affiliated with the Alphaproteobacteria, Acidobacteria, Planctomycetes, and Bacteroidetes, and were similar to those found in acidic peat bogs, yet distinct from the underlying soil community. In contrast, bromeliads with tank pH > 5.3, including the commercial bromeliad with the highest pH (6.7), were dominated by Betaproteobacteria, Firmicutes, and Bacteroidetes. To empirically determine the effect of pH on bacterial community, the tank pH of a specimen of Aechmea was depressed, in the field, from 6.5 to 4.5, for 62 days. The resulting community changed predictably with decreased abundance of Betaproteobacteria and Firmicutes and a concomitant increase in Alphaproteobacteria and Acidobacteria. Collectively, these results suggest that bromeliad tanks provide important habitats for a diverse microbial community, distinct from the surrounding environment, which are influenced greatly by acid–base conditions. Additionally, total organic carbon (∼46%) and nitrogen (∼2%) of bromeliad-impounded sediment was elevated relative to soil and gene surveys confirmed the presence of both chitinases and nitrogenases, suggesting that bromeliad tanks may provide important habitats for microbes involved in the biological cycling of carbon and nitrogen in tropical forests.     

Potential distribution patterns of scorpions in north‐eastern Brazil under scenarios of future climate change

Current predictions about the responses of species to climate change strongly rely on projecting altered environmental conditions on their distributions. In this study, we investigated the effects of future climate change scenarios on the potential distribution of 10 species of scorpions in north‐eastern Brazil in the context of their degree of specialisation to closed (Atlantic and Amazon Forests) and open (Caatinga and Cerrado) habitats. Scorpion species were classified as habitat specialists or generalists according to the IndVal index, and present and future species distribution models were prepared using minimum volume ellipsoids. According to IndVal, four species were classified as closed‐forest specialists (Ananteris mauryi, Tityus brazilae, Tityus pusillus and Tityus neglectus), four as open‐forest specialists (Jaguajir agamemnon, Jaguajir rochae, Physoctonus debilis and Bothriurus rochai), and two as generalists (Tityus stigmurus and Bothriurus asper). All species presented a drastic reduction in potential distribution, ranging from 44% to 72%, when compared with their current distribution. In addition, we found a reduction in scorpion species richness under future climate change scenarios. This finding has implications for scorpion conservation. Further, the results show that climate change may impact the composition of scorpion assemblages in north‐eastern Brazil, revealing important implications for human–scorpion interactions.     

Size-Dependent Variation of Carbon and Nitrogen Isotope Abundances in Epiphytic Bromeliads

Abstract: While atmospheric species of bromeliads have narrow leaves, densely covered with water‐absorbing trichomes throughout their life cycles, many tank bromeliads with broad leaves, forming phytotelmata, go through an atmospheric juvenile phase. The effect of the different habits and the phase change in tank‐forming bromeliads on water and nutrient relations was investigated by analysing the relationship between plant size, C/N ratios and the natural abundance of ¹³C and ¹⁵N in five epiphytic bromeliad species or morphospecies of a humid montane forest in Xalapa, Mexico. The atmospheric species Tillandsia juncea and T. butzii exhibited full crassulacean acid metabolism, with δ¹³C values (mean ‐ 15.3 ‰ and ‐ 14.7 ‰, respectively) independent of size. In Tillandsia species with C₃ photosynthesis, δ¹³C decreased with increasing plant size, indicating stronger drought stress in juveniles. The increase of the C/N ratio with size suggests that, at least in heteroblastic bromeliads, the availability of water is more limiting during early growth, and that limitations of nitrogen supply become more important later on, when water stored in the tank helps to bridge dry periods, reducing water shortage. δ¹⁵N values of the two atmospheric species were very negative (‐ 12.6 ‰ and ‐ 12.2 ‰, respectively) and did not change with plant size. Tank‐forming bromeliads had less negative δ¹⁵N values (c ‐ 6 ‰), and, in species with atmospheric juveniles and tank‐forming adults, δ¹⁵N values increased significantly with plant size. These differences do not appear to be an effect of the isotopic composition of N sources, but rather reflect N availability and limitation and stress‐induced changes in ¹⁵N discrimination.     

Comparative ecophysiology of CAM and C3 bromeliads. I. The ecology of the Bromeliaceae in Trinidad

Abstract This article deals with the physiological ecology of the Bromeliaceae, a large neotropical family containing both terrestrial and epiphytic forms, as well as many species with crassulacean acid metabolism (CAM). The article is in two parts. In the first, we review what is known of the occurrence of CAM and C₃ species in the Bromeliaceae. The photosynthetic pathways are discussed in the context of the major taxonomic divisions within the family and the great diversity of bromeliad life-forms. Of the three subfamilies, the Pitcairnioideae contain both C₃ and CAM species and are essentially all terrestrial. In contrast, the Tillandsioideae are entirely epiphytic or saxicolous, with CAM species being restricted to the genus Tillandsia, And in the Bromelioideae all species show CAM, but terrestrial and epiphytic forms are found in about equal numbers. The evidence suggests that both CAM and the epiphytic habit arose more than once in the family's evolutionary history. In the second part we consider the photosynthetic ecology of the various bromeliad life-forms in more detail using the specific example of Trinidad (West Indies). CAM bromeliads tend to be centred on the drier regions of the island and C₃ forms on the wetter areas. However, at any one site there is a marked vertical stratification of species within the forest profile. Based on the known habitat preferences of the bromeliads, six contrasting sites were selected for field studies in Trinidad. These ranged from arid coastal scrub to montane rain forest, the vegetational and climatic characteristics of which are described here. The constancy of δ¹³C values (carbon-isotope ratios) for individual CAM species in these markedly different habitats emphasized the need for ecophysiological studies to characterize environmental effects on CO₂ assimilation and transpiration. The following papers in this series present the results of a comparative investigation of gas exchange and leaf water relations of CAM and C₃ bromeliads in situ at the various sites.