Program SimAssem: software for simulating species assemblages and estimating species richness

Summary 1. Species richness, the number of species in a defined area, is the most frequently used biodiversity measure. Despite its intuitive appeal and conceptual simplicity, species richness is often difficult to quantify, even in wellsurveyed areas, because of sampling limitations such as survey effort and species detection probability. Nonparametric estimators have generally performed better than other options, but no particular estimator has consistently performed best across variation in assemblage and survey parameters. 2. In order to evaluate estimator performances, we developed the program SimAssem. SimAssem can: (i) simulate assemblages and surveys with user-specified parameters, (ii) process existing species encounter history files, (iii) generate species richness estimates not available in other programs and (iv) format encounter history data for several other programs. 3. SimAssem can help elucidate relationships between assemblage and survey parameters and the performance of species richness estimators, thereby increasing our understanding of estimator sensitivity, improving estimator development and defining the bounds for appropriate application.