Predicting Species Numbers Using Species–Area and Endemics–Area Relations

Current ecological theory predicts an allometric relation between the number of species with restricted range size (endemics) and area (the endemics–area relation EAR), a pattern similar to the common species–area relation (SAR). Using SARs and EARs we can estimate species loss after habitat loss. A comparison of the predictive power of both approaches (using a patch occupancy model and data from European butterflies) revealed that the EAR approach is less reliable than the SAR. Contrary to current theory it appeared that EARs are relations in their own right that describe spatial distributions of endemic species. They do not simply follow from the underlying SAR. The implications of these results for the applicability of SARs and EARs in biodiversity forecasting are discussed.