The vascular epiphytes of a lowland forest in Panama-species composition and spatial structure

We conducted a comprehensive census of the vascular epiphytes in a lowland forest in Panama by means of a canopy crane. In 0.4 ha of ca. 40-m tall forest, 103 species of vascular epiphytes with 13,099 individuals were found. The orchids were the most important family both in species and individual numbers, accounting alone for > 40% of all species and > 50% of all individuals. There was a clear vertical segregation of species with a concentration at intermediate heights: more than 50% of all individuals were found between 15 m and 25 m above ground. Tree species identity, tree size and the position of a tree in the forest (space) all influenced species composition. However, none of the two environmental variables nor space alone explained more than 10% of the total variation in epiphyte assemblages in several canonical correspondence analyses. By far the largest proportion of the observed variation remained unexplained and is arguably due to mere chance. In the future, our results will be used as a baseline data-set for the direct observation of the long-term dynamics in a diverse epiphyte community.