Obligate Epiphyte Research Articles

Effects of host size and substrate types on the distribution of accidental and obligate epiphytes: a case study in a temperate forest of Japan

Effects of host size and substrate types on the distribution of accidental and obligate epiphytes: a case study in a temperate forest of Japan

Factors influencing the distributions of two endangered lichens in Nova Scotia, Canada

ABSTRACT The lichens Erioderma pedicellatum (Hue) P.M. Jørg. and Erioderma mollissimum (G. Sampaio) Du Rietz are endangered species in Canada. Both species are obligate epiphytes found in forested wetlands near the Atlantic Coast. They are thought to be primarily threatened by logging and acid pollution, but the influence of these factors has not been examined at large-extents or relative to other habitat features. Critical habitat for protection has remained difficult to define beyond observed occurrences, because of the low accuracy of existing habitat models. To facilitate improved recovery planning and understanding of their ecology in the province of Nova Scotia, we created high-resolution distribution models for both species, incorporating elements of climate, forest composition, hydrology, acid pollution, and anthropogenic influence using the MaxEnt algorithm and a backwards stepwise selection process. The most important predictors were related to rainfall or an oceanic moderation of thermal optima. Depth to water table and the presence of suitable forest composition were also included, as was distance from roads for E. pedicellatum. The putative threats, acid pollution and silvicultural treatment, were not important and therefore excluded from models. Although both species have highly specific habitat requirements, E. pedicellatum appears to be more sensitive to human activities.

Genome Size of Life Forms of Araceae-A New Piece in the C-Value Puzzle.

The genome size of an organism is an important trait that has predictive values applicable to various scientific fields, including ecology. The main source of plant C-values is the Plant DNA C-values database of the Royal Botanic Gardens Kew, which currently contains 12,273 estimates. However, it covers only 2.9% of known angiosperm species and has gaps in the life form and geographic distribution of plants. Only 4.5% of C-value estimates come from researchers in Central and South America. This study provides 41 new C-values for the aroid family (Araceae), collected in the Piedras Blancas National Park area in southern Costa Rica, including terrestrial, epiphytic and aquatic life forms. Data from our study are combined with C-value entries in the RBGK database for Araceae. The analysis reveals a wider range of C-values for terrestrial aroids, consistent with other terrestrial plants, a trend toward slightly lower C-values for epiphytic forms, which is more consistent for obligate epiphytes, and comparatively low C-values for aquatic aroids.

One large tree crown can be defined as a local hotspot for plant species diversity in a forest ecosystem: a case study in temperate old-growth forest

Large, trees have survived for a long time, and their complex crown structure can serve as habitat for epiphytic plants. Canopy plants are not as well studied in the temperate zones as in the tropics, because many of them are accidental epiphytes, epiphytic individuals of normally terrestrial species. We hypothesized that the canopy can serve as a refuge for terrestrial species that have difficulty establishing on the ground (e.g., insufficient light, deer over-browsing), promoting and conserving forest species diversity. Terrestrial species may also vary in their ability to adapt to a wide range of canopy growth conditions. Here, we investigated canopy vascular plants hosted on a large Cercidiphyllum japonicum tree in a temperate old-growth forest, Japan. The canopy plant community was diverse comprising 39 vascular plant species (6 of which were threatened species), including 31 accidental epiphytes and 8 obligate epiphytes. We found at least 14 species could escape deer over-browsing by establishing in the canopy. Most accidental epiphytes were found on multiple and large reiterated trunks bifurcated from the main trunk as well as on large horizontal branches. Leaves of canopy plants had higher nitrogen concentration compared to those of plants on the ground, and higher water-use efficiency with increasing height was achieved by controlling transpirational water loss. Our results show one large tree crown can be defined as a local hotspot for current and future plant species diversity in a temperate old-growth forest, reinforcing its ecological value for conservation purposes.

EpiList 1.0: a global checklist of vascular epiphytes.

Epiphytes make up roughly 10% of all vascular plant species globally and play important functional roles, especially in tropical forests. However, to date, there is no comprehensive list of vascular epiphyte species. Here, we present EpiList 1.0, the first global list of vascular epiphytes based on standardized definitions and taxonomy. We include obligate epiphytes, facultative epiphytes, and hemiepiphytes, as the latter share the vulnerable epiphytic stage as juveniles. Based on 978 references, the checklist includes >31,000 species of 79 plant families. Species names were standardized against World Flora Online for seed plants and against the World Ferns database for lycophytes and ferns. In cases of species missing from these databases, we used other databases (mostly World Checklist of Selected Plant Families). For all species, author names and IDs for World Flora Online entries are provided to facilitate the alignment with other plant databases, and to avoid ambiguities. EpiList 1.0 will be a rich source for synthetic studies in ecology, biogeography, and evolutionary biology as it offers, for the first time, a species-level overview over all currently known vascular epiphytes. At the same time, the list represents work in progress: species descriptions of epiphytic taxa are ongoing and published life form information in floristic inventories and trait and distribution databases is often incomplete and sometimes even wrong. Since the epiphytic growth blends into soil-rooted growth and vice versa, the inclusion or exclusion of particular species in the current list will sometimes be contentious. Thus, initiating a well-founded discussion was one of the motivations for compiling this database; our list represents 31,311 hypotheses on the life form of plant species, and we welcome feedback on possible omission or erroneous inclusions. We release these data into the public domain under a Creative Commons Zero license waiver. When you use the data in your publication, we request that you cite this data paper. If EpiList 1.0 is a major part of the data analyzed in your study, you may consider inviting the EpiList 1.0 core team as collaborators.

Эпифитные лишайники Беларуси. II. Облигатные и факультативные эпифиты

The lichen biota of Belarus lists 406 corticolous species. Of these, 213 (35.7%) species are obligate epiphytes. Crustose lichens make up the majority of obligate epiphytes (157 species, or 73.7%). Apparently, this can indicate the decisive role of the morphology and chemistry of the substrate for the closely contacted lichen thallus. Facultative epiphytes are represented by 193 species, which are quite widely represented by foliose and fruticose life forms (51.3%). Facultative epiphytes inhabit rotting and processed wood, stony substrates, soil (including forest litter), mosses, leaves (needles), root turnouts and metal objects. Wood is inhabited by 154 facultative epiphyte species, of which 80 lichens are strongly epiphyticlignicolous. The lichen diversity of tree bark and wood is relatively similar; the value of the Sørensen-Dice index is equal to 0.51. Soil is the second most important substrate after wood for facultative epiphytes. It is inhabited by 55 lichens, most of which are represented by Cladonia and Peltigera species. 46 species of facultative epiphytes were found on mosses. These are represented mainly by cyanobiont-containing lichens, broad-lobed species, as well as many by the representatives of the genus Cladonia. The stony substrate is suitable for 43 facultative epiphytes species and is characterized by a high specificity of lichen biota. Its Sørensen- Dice index is equal to 0.13. Most of these representatives are common in urban environments. Fungi, lichens, root inversions, leaves, and metal are predominantly inhabited by multisubstrate lichen species.

Drought resistance does not explain epiphytic abundance of accidental epiphytes

ABSTRACT Background Accidental epiphytism is common among vascular plants in forest ecosystems around the globe. A frequent observation in surveys of accidental epiphytes is the occurrence of few species with high epiphytic abundance, while most co-occurring terrestrial species are rarely found as epiphytes. Aims Based on the general assumption that water is the major limiting factor for epiphytic plants, we hypothesised that differences in drought resistance of accidental epiphytes explain the difference in epiphytic abundances. Methods We exposed 16 species with different epiphytic abundance in central Europe to experimentally induced drought during germination and growth of juvenile plants. Results Drought resistance differed substantially among species but did not correlate with their epiphytic abundance, neither during germination nor during juvenile growth. Conclusions In central Europe, accidental epiphytes are usually found on moss cushions or in accumulated arboreal soil on their host tree. In such water-storing substrates, water availability might be less limiting than it is for obligate epiphytes that typically grow on bare bark, which would explain the lack of a correlation between drought resistance and epiphytic abundance of the studied species. Hence, other factors must explain the consistent differences in epiphytic abundance, e.g. dispersal traits and mass effect.

Experience of a Synthetic Approach to an Ecological Classification of Vascular Epiphytes

On the basis of an investigation into epiphytic ferns and taking into account the literature data, information on ecological classifications of vascular epiphytes has been summarized and a multiple ecological classification is proposed in which vascular epiphytes are grouped into three blocks of morphofunctional types (MFT): facultative epiphytes (protoepiphytes), obligate epiphytes (holoepiphytes), and hemiepiphytes. The main criterion underlying this division is the degree of specialization of plants to the epiphytic life pattern. Each group includes several subgroups diverging on the basis of the presence of special morphological structures providing epiphytes with nutrients and water under conditions of their deficit, as well as life under the conditions of low irradiation and high hydrature. Within the subgroups, the variants are distinguished and the preadaptive and adaptive mechanisms used by the epiphytes in order to cope with the specific environment are defined for the variants. Physiofunctional types with specialization to an epiphytic mode of life are distinguished as well.

Accidental epiphytism in the Harz Mountains, Central Europe

AbstractQuestionsVascular epiphytes make up about 9% of all vascular plants globally but are clearly underrepresented in the temperate zones. The accidental epiphytic occurrence of terrestrial species, in contrast, is common at these latitudes and can provide important insights in the evolution of obligate epiphytes. Here, we present the results of the first two annual censuses of a planned long‐term study on accidental epiphytes. We particularly aim to identify: (a) the abundance and species richness of accidental epiphytes; (b) the dynamics of accidental epiphytism; (c) occupied substrates and microsites; and (d) suitable host tree species.LocationHarz Mountains, Germany, Central Europe.MethodsWe surveyed more than 1,200 trees in a low mountain range in two consecutive years for epiphytic individuals of vascular plants, considering host tree species and occupied microsites.ResultsAbout one quarter of the surveyed trees hosted epiphytic plants, totalling 1 450 (2016) and 1 350 (2017) individuals, respectively. These belonged to more than 100 species and 39 different families. The majority of epiphytic individuals newly emerged in 2017, whereas one‐third persisted since 2016 (or earlier) and a smaller proportion even reproduced in the epiphytic habitat. Accidental epiphytes were mostly restricted to host tree species providing water‐storing substrates such as extensive moss pads or arboreal soil accumulated in crotches. Compared to tropical epiphyte communities, accidental epiphytes in the temperate zones show a higher turnover, as they are less consistent in species abundance and composition in time.ConclusionFor the majority of the observed species, epiphytism indeed is an accidental phenomenon. Undoubtedly, abiotic conditions limit the occurrence of obligate epiphytes at higher latitudes, but the presence and persistence of numerous epiphytic individuals illustrate that abiotic conditions do not per se preclude epiphytic occurrence of vascular plants in the north‐temperate zone. Besides water shortage, the availability of suitable host trees is a decisive environmental factor that contributes to limit epiphytism of vascular plants in Central Europe.

The phylogenetic position of the morphologically unusual Pleurostichidium falkenbergii (Rhodomelaceae, Rhodophyta) based on plastid phylogenomics

ABSTRACTPleurostichidium falkenbergii is an obligate epiphyte on Xiphophora chondrophylla and is endemic to northern New Zealand. This monotypic genus is characterised by having dorsiventral and laterally compressed thalli with 20 pericentral cells and complete cortication, adventitious trichoblasts, spherical spermatangial branches formed from cortical cells, and stichidia with up to 19 whorled tetrasporangia. This unusual combination of morphological characters among the Rhodomelaceae led to its placement in a separate tribe Pleurostichidieae. The tribal phylogenetic placement has been investigated only using 18S rRNA and remains uncertain. We investigated the phylogenetic affinities of P. falkenbergii using a plastid phylogenomic approach. We sequenced and assembled its plastid genome and inferred a phylogeny along with 45 other rhodomelacean species and 10 outgroup taxa. P. falkenbergii was placed in a highly supported clade containing the tribes Pterosiphonieae, Dipterosiphonieae, Herposiphonieae, and a clade with two species morphologically assigned to Polysiphonia and Melanothamnus, but genetically unrelated to the true Polysiphonia and Melanothamnus lineages. Pleurostichidium falkenbergii was placed as sister to the Pterosiphonieae with moderate support. Considering our results and the unusual combination of vegetative and reproductive characters of Pleurostichidium, we propose to maintain the tribe Pleurostichidieae for this species.

Amphithallia, a genus with four-celled carpogonial branches and connecting filaments in the Corallinales (Rhodophyta)

ABSTRACTThe South African marine alga Amphithallia crassiuscula, previously subsumed in the widely reported Synarthrophyton patena, is here re-described as a distinct species and genus. Thalli grow as obligate epiphytes on Gelidium capense in the upper sublittoral zone (while S. patena grows on Ballia callitricha). Gametophytes are monoecious with four-celled carpogonial branches and sterile cells are borne on supporting cells (dioecious or hermaphroditic with two or three-celled carpogonial branches and sterile cells borne on hypogynous cells in Synarthrophyton). Postfertilization stages involve a connecting filament linking the carpogonium to several putative auxiliary cells, demonstrating a non-procarpic condition with apparent absence of a fusion cell. Gonimoblast filaments develop at the level of basal cells of carpogonial branches. Spermatangial mother cells remain either unbranched (cutting off spermatangia only) or develop dendroid (branched) filaments with terminal spermatangia (as in Synarthrophyton). Multiporate conceptacles develop straight pore canals lined by non-differentiated cells (conical canals with differentiated pore cells along the base in Synarthrophyton). The here described pre- and post-fertilization characters are new for the order Corallinales motivating the establishment of the new genus Amphithallia.

Noteworthy habitat and phylogeny updates for eastern US Ulota (Orthotrichaceae, Bryophyta)

The moss Ulota crispa is ubiquitous as an obligate epiphyte in eastern North America. Yet several specimens preliminarily identified as U. crispa were collected from the upper portions of boulders in the Shawangunks, NY. Mitochondrial (nad5) and chloroplast (rps4 and trnL-trnF) sequence data were produced for these specimens, confirming their status as the first record of rock-dwelling U. crispa in North America. The reviewed loci were then used to assess phylogenetic relationships of Northeastern US Ulota species, incorporating a species not yet reviewed, U. coarctata. Conforming to peristome morphology, Ulota hutchinsiae appears to be more closely related to U. crispa than to U. coarctata. Monophyly was recovered for U. crispa and U. coarctata. Although monophyly was not found for U. hutchinsiae, it is diagnosably distinct based on the reviewed loci. While almost identical in number of nucleotides sequenced, mitochondrial DNA held substantially less phylogenetically informative nucleotides than the chloroplast loci, but did have important indel information segregating U. coarctata from other species reviewed.

Determinants of occurrence of epiphytic mosses in the urban environment; a case study from Katowice city (S Poland)

Abstract Katowice is the largest city within the Upper Silesian Industrial District (S Poland). The investtigation conducted in this town earlier (1998-2000) showed limited number of epiphytic species. Recent study showed significant increase in number of localities of obligate epiphytes (mainly from the genera Orthotrichum and Ulota). They colonize mainly the edges of strongly urbanized areas bordering forest complexes and larger parks. This paper is an attempt to answer the question as currently in Katowice shape the main factors determining the occurrence of epiphytes. Crucial factors which govern epiphytes colonization processes in urban areas have been confirmed: bark chemistry (taking into account natural attributes and the influence of pollution) and air humidity. The preference of epiphytes towards inhabited phorophytes was confirmed as well. The most commonly and abundantly inhabited species were poplar and willow trees (which have a higher pH of bark).

A host-specific habitat former controls biodiversity across ecological transitions in a rocky intertidal facilitation cascade

Few studies have quantified facilitation cascades from rocky intertidal systems, across ecological transition zones, or where the secondary facilitator is an obligate epiphyte. Here, we address these research gaps. We first quantified distributions of the seaweed host Hormosira banksii and its obligate epiphyte Notheia anomala at different tidal elevations in summer and winter at Kaikoura, New Zealand. This analysis showed that the host and the epiphyte were, in both seasons, most abundant at ‘high’ and ‘low’ tidal elevations respectively, probably driven by contrasting responses to competitors and desiccation. We subsequently quantified richness and abundances of mobile invertebrates associated with Hormosira and various levels of epiphytic Notheia. Hormosira fronds were collected from different elevations, seasons, diurnal cycles, with different neighbouring algae and following an epiphyte-removal experiment. All tests showed positive density-dependent effects of Notheia-epiphytism on richness and abundances of invertebrates, with strongest facilitation occurring at the transition from intertidal to subtidal habitats. Our results support a growing number of facilitation cascade studies from different ecosystems and habitats, and suggest that habitat formation–driven facilitation cascades may be particularly common in marine benthic systems where epibiosis can be a dominant life form.

Ecological Diversity of Bryophytes on Tree Trunks in Protected Forests (A Case Study from Central Poland)

Abstract: Fudali, E. & Wolski, G. J. 2015. Ecological diversity of bryophytes on tree trunks in protected forests (a case study from Central Poland). — Herzogia 28: 87–103. The flora and number of bryophytes (mosses and liverworts) colonizing tree trunks in ten forest nature reserves established between 1954 and 1996 and previously subjected to forest management, were analysed with regard to species ecological preferences, vertical distribution and life history strategies. The study aimed to identify ecological characters of bryophytes occurring on tree trunks in forests where intensive exploitation ceased many years ago. The question whether the current corticolous bryoflora continues to reflect past disturbances in the forest environment due to previous forest management is discussed. With respect to the species richness and diversity of their substratum requirements, the bryoflora occurring on tree trunks more closely resembled that of natural than of managed forests. However, obligate epiphytes (inclu...

DNA sequencing, anatomy, and calcification patterns support a monophyletic, subarctic, carbonate reef-forming Clathromorphum (Hapalidiaceae, Corallinales, Rhodophyta).

For the first time, morpho-anatomical characters that were congruent with DNA sequence data were used to characterize several genera in Hapalidiaceae-the major eco-engineers of Subarctic carbonate ecosystems. DNA sequencing of three genes (SSU, rbcL, ribulose-1, 5-bisphosphate carboxylase/oxygenase large subunit gene and psbA, photosystem II D1 protein gene), along with patterns of cell division, cell elongation, and calcification supported a monophyletic Clathromorphum. Two characters were diagnostic for this genus: (i) cell division, elongation, and primary calcification occurred only in intercalary meristematic cells and in a narrow vertical band (1-2μm wide) resulting in a "meristem split" and (ii) a secondary calcification of interfilament crystals was also produced. Neopolyporolithon was resurrected for N. reclinatum, the generitype, and Clathromorphum loculosum was transferred to this genus. Like Clathromorphum, cell division, elongation, and calcification occurred only in intercalary meristematic cells, but in a wider vertical band (over 10-20μm), and a "meristem split" was absent. Callilithophytum gen. nov. was proposed to accommodate Clathromorphum parcum, the obligate epiphyte of the northeast Pacific endemic geniculate coralline, Calliarthron. Diagnostic for this genus were epithallial cells terminating all cell filaments (no dorsi-ventrality was present), and a distinct "foot" was embedded in the host. Leptophytum, based on its generitype, L. laeve, was shown to be a distinct genus more closely related to Clathromorphum than to Phymatolithon. All names of treated species were applied unequivocally by linking partial rbcL sequences from holotype, isotype, or epitype specimens with field-collected material. Variation in rbcL and psbA sequences suggested that multiple species may be passing under each currently recognized species of Clathromorphum and Neopolyporolithon.

着生シダ植物シノブ科および近縁シダの進化と形態変化

The evolution of epiphytes in Davalliaceae was investigated by field observations and molecular phylogenetic analyses. Field studies revealed that in Davalliaceae and related ferns, epiphytes in a broad sense are classified into climber, secondary hemi-epiphyte, and obligate epiphyte, based on combinations of the places (ground vs. tree) of inferred spore germination and sporophyte growth. Some species of Davalliaceae have multiple life forms, i.e. secondary hemi-epiphyte and obligate epiphyte, whereas others are obligate epiphytes. Phylogenetic trees obtained from rbcL and accD gene sequences supported that secondary hemi-epiphytic Oleandra is sister to the epiphytic Davalliaceae and polygrammoid ferns. Analyses of life form evolution based on the phylogenetic relationships suggested that obligate epiphytes of the Davalliaceae and polygrammoid ferns evolved from secondary hemi-epiphytes, or less likely from climbers. We hypothesized a scenario for the evolution of life forms in Davalliaceae and related groups that involves successive changes in rhizome habit, root function, and germination place. Rhizome dorsiventrality and scale morphology, shared by climbers, secondary hemi-epiphytes, and obligate epiphytes examined, may be other innovations for the ferns to have evolved into epiphytes. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 151, 495–510.

Evolution of sexual systems, dispersal strategies and habitat selection in the liverwort genus Radula

• Shifts in sexual systems are among the most common and important transitions in plants and are correlated with a suite of life-history traits. The evolution of sexual systems and their relationships to gametophyte size, sexual and asexual reproduction, and epiphytism are examined here in the liverwort genus Radula. • The sequence of trait acquisition and the phylogenetic correlations between those traits was investigated using comparative methods. • Shifts in sexual systems recurrently occurred from dioecy to monoecy within facultative epiphyte lineages. Production of specialized asexual gemmae was correlated to neither dioecy nor strict epiphytism. • The significant correlations among life-history traits related to sexual systems and habitat conditions suggest the existence of evolutionary trade-offs. Obligate epiphytes do not produce gemmae more frequently than facultative epiphytes and disperse by whole gametophyte fragments, presumably to avoid the sensitive protonemal stage in a habitat prone to rapid changes in moisture availability. As dispersal ranges correlate with diaspore size, this reinforces the notion that epiphytes experience strong dispersal limitations. Our results thus provide the evolutionary complement to metapopulation, metacommunity and experimental studies demonstrating trade-offs between dispersal distance, establishment ability, and life-history strategy, which may be central to the evolution of reproductive strategies in bryophytes.

An examination of the epiphytic nature of Gambierdiscus toxicus, a dinoflagellate involved in ciguatera fish poisoning

Twenty-four specimen of macroalgae were collected in nearshore waters of the island of Hawaii, identified, and maintained to examine how the epiphytic relationship between Gambierdiscus toxicus (isolate BIG12) varied among the macroalgal species. Gambierdiscus cells were introduced to Petri dishes containing 100 g samples of each macroalgal host, which were examined at two, 16, 24, and every 24–72 h thereafter, over a 29-day period. Gambierdiscus proliferated in the presence of some host species (e.g., Galaxaura marginata and Jania sp.), but grew little in the presence of other species (e.g., Portieria hornemannii). Gambierdiscus exhibited high survival rates (>99%) in the presence of Chaetomorpha sp., but died before the end of the experiment (after 21 days) with other host species (e.g., Dictyota and Microdictyon spp.). Gambierdiscus avoided contact with P. hornemannii, but averaged up to 30% attachment with other host species. The numbers of Gambierdiscus cells belonging to one of three classes (alive and attached; alive and unattached; and dead) were determined for each time point. The 24 algal hosts were grouped according to their commonalities relative to these three classes using a Bray-Curtis similarity index, similarity profile (SIMPROF) permutation tests, and Multi-Dimensional Scaling (MDS) analysis (PRIMER 6). The resultant six groupings were used to construct different Gambierdiscus growth profiles for the different algal hosts. Group A is characterized by a preponderance of unattached cells and high mortality rates. Groups B, C, E, and F also displayed high proportions of unattached cells, but mortality either occurred later (Groups B and C) or rates were lower (Groups E and F). Group D had the highest proportion of attached cells. Group E contained three out of the four chlorophyte species, while Group F contained the majority of the rhodophytes. Over 50% of the species in Group F are considered to be palatable, whereas Groups A, B, and C are composed of species that exhibit chemical defenses against herbivory. The results of this study coupled with previous findings indicate that Gambierdiscus is not an obligate epiphyte; it can be free-swimming and found in the plankton. The conditions that lead to changes between epiphytic and planktonic stages need to be better studied in order to determine how they affect Gambierdiscus growth and physiology, connectivity and dispersion mechanisms, and toxin movement up into the foodweb.

How arboreal are epiphytes? A null model for Benzing's classifications

Benzing (2004) classified epiphytes as either ‘obligate’, ‘facultative’ or ‘accidental’ to describe variability in the tendency of epiphytic plants to grow arboreally. However, no method currently exists to quantitatively categorize epiphytes according to this classification system. Here, I derive a null model to test whether epiphytes are obligate, facultative or accidental, and then apply it to local epiphyte assemblages in two similar latitude forests on either side of the equator to test for hemispherical asymmetries in the relative abundance of different functional guilds of epiphytes. Results from the null model showed that the northern hemisphere site was comprised mostly of facultative epiphytes, which usually occurred on the forest floor. Conversely, the southern hemisphere site was comprised mostly of obligate epiphytes, which rarely occur on the forest floor, if at all, supporting previous speculation that epiphyte communities are structured in fundamentally different ways in the northern and southern hemispheres.