Lichen diversity on tree trunks in tropical dry forests is highly influenced by host tree traits

Tropical dry forests have been recognized as one of the most threatened ecosystems in the world due to deforestation. These ecosystems harbour a high endemicity of epiphytes, which play a major role in the functioning of the forests. Lichens constitute an important fraction of the epiphytes. These poikilohydric organisms respond drastically to disturbance, which is strongly linked to humidity and light availability. We hypothesized that richness and species composition of lichens would be related to differences in forest structure (e.g., canopy openness) promoted by deforestation, and by host tree characteristics, due to the fact that dry forests generally have poor microclimatic stratification and low diversity of tree species. In this study, we assessed the richness and composition of epiphytic lichens on the trunks of 513 trees in undisturbed and disturbed dry forests of southern Ecuador. Both lichen composition and richness were highly correlated with tree species and host tree traits such as bark structure and tree diameter. Additionally, epiphytic lichen diversity was related to canopy cover and tree richness at different disturbance levels. We conclude that epiphytic lichen communities in seasonal dry tropical forests of Ecuador are mainly limited by host tree traits and tree species. Loss of epiphytic lichen species in the studied forests is particularly due to loss of host trees such as Cochlospermum vitifolium and Eriotheca ruizii, that maintain high species richness.