Sampling Methods for Vascular Epiphytes: Their Effectiveness in Recording Species Richness and Frequency

Abstract

Vascular epiphytes are an important component of tropical biodiversity; however, because of problems associated with accessing them, it is hard to obtain a complete species inventory. It is faster and safer to make ground-based observations of epiphytes than it is to collect data using climbing techniques, but the quality of the observations may be suspect. To compare ground-based observations and observations based on climbing, we recorded epiphytic species present in three types of vegetation: remnant trees in pasture, a forest corridor along a brook, and a closed forest. Using species accumulation functions, we predicted total species richness and the sampling effort to determine it. Ground-based observations underestimated epiphytic species richness, but this underestimation was independent of vegetation structure and tree size. The number of epiphytic species recorded with climbing-based observations increased by 16.3- 23.3% over the number recorded with ground-based observations. Such observations underestimated species frequency and could indicate that a species is rare when it is not. Species accumulation models fitted to ground-based data failed to predict species richness correctly. If fitted to climbing-based observations, however, they could predict the richness and sampling effort for a complete species inventory. Our study demonstrated the limitations and problems of ground-based epiphyte observations for species inventories.