Regional and Fine Scale Variation of Holoepiphyte Community Structure in Central Amazonian White-Sand Forests

Abstract

Factors controlling holoepiphyte (plants which start and complete their life cycle on a phorophyte) distributions may be wide and variable. They are determined either by spatial processes, as evidenced by dispersal limitation and/or historical factors, environmental filters, such as microsite variation within phorophytes, and/or biotic interactions. Disentangling the importance of these classes is particularly difficult in tropical forests where phorophyte alpha-diversity is exceptionally high. We controlled for phorophyte specificity by studying the holoepiphytic communities of an emergent tree Aldina heterophylla (Fabaceae), known for its heavy epiphyte loads and dominance in Amazonian white-sand habitats, in order to quantify the importance of tree zone and geographic distance on holoepiphytes at fine (100 m2) and regional (2500 km2) scales. At regional scales, tree zone explained nearly two-thirds of the main compositional gradient, accounting for more than double that of site differences. No spatial effects were observed on holoepiphyte community structure at the fine scale as treelet communities were more dissimilar than by chance alone from their neighboring emergent phorophyte. These results suggest that microsite availability, as opposed to dispersal limitation, is the most important mechanism in structuring holoepiphyte communities of this insular forest type. © 2016 The Association for Tropical Biology and Conservation.