Epiphytes are a unique plant growth form that live non-parasitically on other plants and constitute approximately one-third of tropical vascular plant diversity. They are key components of forest ecosystem function and provide resources for a wide array of animals. Understanding the ecology of epiphytes is timely because they are particularly vulnerable to climate change and deforestation. Because of the innately close connection between an epiphyte and its host tree, substrate traits are likely critical to the establishment of diverse epiphyte communities. However, little experimental evidence exists for when during ontogeny that host traits are most important, or what host traits drive epiphyte community development. Here, we use an in situ experiment in the cloud forest of Santa Fé, Panama, to test the extent to which substrate texture serves as a filter to epiphyte establishment. We applied a mix of several species of epiphyte seeds to salvaged native wood substrates with five different rugosities (roughness measurements), and monitored the seed germination and establishment over several months. We focus on the very early life stages because these are a key bottlenecks for community assembly.
Results/Conclusions
We present some of the first experimental field evidence that substrate texture can drive subsequent epiphyte establishment. Rougher substrates facilitated higher epiphyte establishment, and epiphyte seedling abundances differed between the smoothest and the two most rugose substrates. After just two months, less than 1% of all seedlings on average were present on the smoothest substrate and 34% of the seedlings remained on the second-roughest substrate (14% more than expected). Survival rates differed among rugosity treatments, but all seedlings died in a catastrophic rainstorm after approximately 14 months. Our results suggest that the texture of the substrate can account for some of the variability in epiphyte seedling survival at this early bottleneck stage. This variability likely contributes to observed niche differentiation of epiphytes both within- and among-host trees.