Search

Copyright of Functional Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aim: Vascular epiphytes are ubiquitous components of wet tropical forests where they contribute substantially to local and regional plant diversity. While some basic epiphyte distribution patterns are relatively well studied, little effort has been made to understand the drivers responsible for constraining their global distribution. This study quantifies the substantial contribution of epiphytes to global gradients and centres of vascular plant diversity and explores whether epiphytes vary from terrestrial plants in relation to contemporary and historical environmental variables. Location: Global. Time period: Present. Major taxa studied: Tracheophyta. Methods: Using a comprehensive epiphyte species list (EpiList 1.0), and distribution information for 27,850 epiphyte species derived from numerous literature sources, we describe the global biogeography of epiphytes. We use generalized linear mixed effects models to assess the relationship between epiphytic and terrestrial plant diversity, and contemporary and historical environmental predictors. Results: Epiphytes substantially contribute to global centres of vascular plant diversity, accounting for up to 39% of the vascular flora in Neotropical regions. Epiphytes decrease in species numbers with increasing latitude at a rate three times faster than terrestrial plants, a trend that is driven mainly by the distribution of tropical forests and precipitation. Further, large regional differences emerge that are explained by several large endemic angiosperm families (e.g., Neotropical Bromeliaceae) that are absent in other tropical regions. Main conclusions: Our results show that epiphytes are disproportionately diverse in most global centres of plant diversity and play an important role in driving the global latitudinal diversity gradient for plants. The distribution of precipitation and tropical forest area emerge as major drivers of the latitudinal diversity gradient in epiphyte species richness. Finally, our findings demonstrate how epiphyte floras in different biogeographical realms are composed of different families and higher taxa, revealing an important signature of historical biogeography. [ABSTRACT FROM AUTHOR]

The extraordinary diversity of orchids has captivated scientists for more than a century, yet their complex spatial patterns at large scales remain poorly resolved. On islands, orchid diversity patterns are especially puzzling. While some islands are centres of orchid diversity, orchids are underrepresented on most islands. To disentangle such complex patterns, key functional differences among orchids must be considered – a distinction seldom made in biogeographical analyses. Using a global dataset of 454 islands, we tested prominent hypotheses in island biogeography, while simultaneously making the distinction between epiphytes and two terrestrial life forms (geophytes and non‐geophytes). Orchid diversity was unevenly distributed across islands and life forms. Epiphytic orchid diversity strongly increased with temperature, illustrating the near confinement of epiphytes to the tropics. Geophytes became proportionally more important with increasing seasonality, highlighting their ability to withstand harsh climatic conditions. Epiphytes and non‐geophytes both displayed responses (e.g. negative relationship with seasonality) related to their dependence on consistently favourable conditions, possibly because of the absence of subterranean storage organs. This highlights that the factors explaining orchid diversity differ strongly with, and are related to, life form. We suggest that key functional differences within and across plant families be considered in future studies to better understand drivers of complex diversity patterns. [ABSTRACT FROM AUTHOR]

Vertical gradients of light and humidity within forest canopies are major predictors of air plant distributions. Although this pattern was first recognized over 120 years ago, few studies have considered an additional axis of resource availability, which exists radially around the trunks of trees. Here, we explored the radial distributions of mistletoes and epiphytes in relation to gradients of light and humidity around the trunks of their south-temperate host trees. Additionally, we correlated microclimate occupancy with plant physiological responses to shifting resource availability. The radial distributions of mistletoes and epiphytes were highly directional, and related to the availability of light and humidity, respectively. Mistletoes oriented northwest, parallel to gradients of higher light intensity, temperature, and lower humidity. Comparatively, epiphytes oriented away from the sun to the southeast. The rate of CO2 assimilation in mistletoes and photochemical efficiency of epiphytes was highest in plants growing in higher light and humidity environments, respectively. However, the photosynthetic parameters of mistletoes suggest that they are also efficient at assimilating CO2 in lower light conditions. Our results bridge a key gap in our understanding of within-tree distributions of mistletoes and epiphytes, and raise further questions on the drivers of air plant distributions. [ABSTRACT FROM AUTHOR]

Aim Epiphytes are a conspicuous feature of numerous forests, yet they are poorly understood compared with terrestrial plants. Theoretical frameworks have helped bridge this gap; however, important questions relating to epiphyte community development have yet to be answered. For example, at what point in tree ontogeny do epiphytes first establish? Do epiphyte communities develop uniformly, or is there variation among host trees? Methods In this study, we build upon Darwin's geological theory of island ontogeny to explore changes in epiphyte species richness throughout the life span of their respective host trees. Based on the general features of island ontogeny, we predict that there are three stages of epiphyte community development: (i) an initial stage where host trees are devoid of epiphytes because they lack sufficient architectural and physiological characteristics suitable for epiphyte establishment, (ii) a second stage where trees acquire epiphytes as adults and continue to do so into maturity, and (iii) a final stage where epiphyte communities progress through a period of species decline following host tree mortality. To test our model predictions, we censused epiphyte communities on 371 host trees from six New Zealand tree species. We first assessed the relationship between epiphyte species richness and host tree diameter. We then tested whether relationships between epiphyte species richness and host tree diameter varied between host species. Results and conclusion Results were consistent with model predictions. Our investigation found variation in the ontogenetic stage at which host trees become favourable for epiphyte establishment. Moreover, the rate at which epiphyte species richness increased with host tree diameter varied among host species. Our findings indicate that an island ontogeny framework is useful for guiding investigations on epiphyte community development. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]