Justification: Vascular epiphytes contribute substantially to local plant diversity in tropical forests. However, does this trend hold true at larger spatial scales?

Objectives: We give an overview on the current state of the art in epiphyte research at the regional to global scale, with the objectives of understanding a) the general trends and contribution of epiphytes to large-scale gradients of vascular plant diversity, and b) the drivers responsible for constraining their regional and global distribution.

Methods: We draw inferences from epiphyte biodiversity studies spanning regional and elevational gradients to global-level biogeographical analyses.

Results: Epiphytes substantially contribute to both regional and global centres of vascular plant diversity, with clear hotspots in the Neotropics and tropical Asia. These hotspots are attributed to extensive tropical forests and mountain ecosystems, both of which offer optimal conditions (e.g., high humidity) for epiphyte growth and survival. Across elevational gradients, epiphytes generally peak in species richness at mid-elevations, highlighting their comparatively narrow climatic tolerances compared to terrestrial plants.

Implications: Our talk highlights the importance of epiphytes as contributors of biodiversity beyond local scales, and that their striking regional differences have resulted from historical and evolutionary processes, such as the radiation of large endemic angiosperm groups in some regions (e.g., Pleurothallis spp, and Bromeliaceae in the Neotropics).