Endemics-area relationships: The influence of species dominance and spatial aggregation

Patterns in the spatial distribution of endemic species are central to setting conservation priorities and estimating extinction rates due to habitat loss. We use quantitative models to isolate the effects of relative species abundances and conspecific spatial distributions on the endemics-area relationship. Using published abundance data from a tropical rain forest community, we apply these models to illustrate how species abundance distributions and species spatial distributions have a strikingly different influence on total and endemic species diversity patterns, respectively. Increased dominance and conspecific aggregation in a region will act to decrease the total species diversity of smaller sampled subregions, but to increase subregional endemic species diversity. Our results suggest that biotic or abiotic forces contributing to regional-scale species dominance and conspecific clustering may increase the risk of extinctions under habitat loss.