Species accumulation curves and the measure of sampling effort

Summary Moreno & Halffter (2000) described the problems associated with comparing species richness among communities that have inventories compiled using different methods or with different sampling effort. They used species accumulation curves to standardize samples among sites, to predict the species richness of sites and to estimate the minimum effort required for adequate completeness of inventories. I argue that their measure of sampling effort, number of nights, is inappropriate because it does not distinguish between genuine differences in species richness among sites and differences in trap efficiency. The number of individuals is the best measure of sampling effort to avoid this problem, as illustrated by data on moths collected from a Bornean rainforest. Furthermore, the approach of Moreno & Halffter requires the species accumulation curves to be approaching an asymptote for accurate estimation, and so for practical reasons is probably limited to less diverse taxa.