Turnover Rates in Insular Biogeography: Effect of Immigration on Extinction

Abstract

Demographic and genetic contributions from conspecific immigrants tend to reduce extinction rates of insular populations. The MacArthur—Wilson model of island biogeography is modified to provide for this effect of immigration on extinction, which we call the rescue effect. This new model predicts that when immigration rates are high relative to extinction rates, turnover rate is directly related to the distance between an island and the source of colonizing species. A field study of the distribution of arthropods among isolated plants supports the model.