Importance of the vertical gradient in the variation of epiphyte community structure in the Brazilian Atlantic Forest

Epiphytes are strongly affected by the microclimate of the forest canopy. Therefore, understanding how microclimatic changes are related to the functional characteristics of taxa and the patterns of communities is essential. Our objective was to examine the stratification of the epiphyte community along the vertical gradient of the forests and to investigate whether the pattern of species distribution in the canopy height zones is similar among forests with different characteristics and between the families of epiphytic plants. The study was carried out in the Atlantic Forest of Ilha Grande, in southeastern Brazil, where we recorded 76 species. The highest richness and abundance were found on tree trunks. The high crown had less diversity and a characteristic set of species. The vertical stratification pattern was similar across forests with different phytophysiognomies. The main epiphytic families exhibited different patterns of diversity along the canopy. The highest richness of Araceae occurred in the trunk zones, while Polypodiaceae, Bromeliaceae, and Orchidaceae were more diverse in the trunk and inner crown, and Cactaceae were more diverse in the inner crown. Tree height zones select epiphytic taxa with distinct characteristics according to the fundamental conditions for their survival and, therefore, we suggest that the ecological niche theory is adequate to explain the assembly of epiphytic communities at a local scale.