The Peninsular Effect on Species Diversity and the Biogeography of Baja California

Abstract

A simulation model is presented which explores the extinction-recolonization explanation of the decreased number of animal species on peninsulas. Using as an example the pattern of species density of heteromyid rodents on Baja California, we show that severe constraints on the values of the parameters are necessary for the model to produce an appropriate pattern. When competition, modeled as influencing the probability of extinction, is included in the simulation, an appropriate equilibrium pattern is difficult to produce. A peninsular effect results more easily if the habitable sites are few and widely spaced. The rapid speed with which equilibria were approached, even when adjusted for inaccurate assumptions, makes an explanation based upon a faunal disequilibrium unlikely.