Vertical distribution and transplanted survival of epiphytes in a Neotropical premontane cloud forest

Background One well-established hypothesis to explain high epiphyte diversity in the Neotropics is the vertical niche differentiation hypothesis (VNDH). The VNDH posits that Neotropical epiphytic biodiversity is driven by the differentiation of epiphytes into specialised niches throughout the forest canopy. However, few studies have taken an experimental approach to testing this hypothesis.Aims To determine whether epiphyte morphospecies exhibit vertical niche specialisation and whether shifts in vertical position affect their survival.Methods We assessed the vertical distribution of 35 common epiphyte morphospecies across 30 focal host trees to characterise naturally occurring variability in epiphyte distributions. We then experimentally transplanted individuals from their original canopy positions to the understorey to test the effects of altered vertical strata on survival.Results None of the 35 morphospecies were strictly specialised by height zone and many were non-uniformly distributed throughout the canopy. Survival rates declined with increasing original canopy height – epiphytes found higher in the canopy were less likely to persist after relocation to the understorey.Conclusion Our results support the notion of vertical stratification among Neotropical vascular epiphytes and experimentally demonstrate survival consequences linked to this stratification. These findings contribute to understanding mechanisms underlying tropical epiphyte diversity and offer insights for forest managers interested in the sustainable horticulture of tropical epiphytes.