HABITAT DESTRUCTION, DISPERSAL, AND DETERMINISTIC EXTINCTION IN COMPETITIVE COMMUNITIES

An analytical model of competitive coexistence in spatial habitats, mo dified to address habitat destruction, predicts that the most abundant species can be among the first species driven extinct by habitat dest ruction, given that abundant species are the poorest dispersers and be st competitors. This contrasts with the classical view of biased extin ction of rare species. Here we explore the robustness of this predicti on both analytically and in spatially explicit simulations of more rea listic cases. The prediction proved surprisingly robust. The poorest d ispersers, which in this model generally are the best competitors and may be the most abundant species, were among the first driven extinct by habitat destruction whether they were abundant or rare, had short o r long range dispersal, or reproduced continuously or periodically; wh ether competitive displacement was immediate or gradual; whether habit at destruction was clumped, uniform, or random and whether destruction occurred at once or progressively; and whether the habitat was large or small. The amount of destruction sufficient to produce extinctions changed considerably as model assumptions changed, but the biased exti nction remained. The underlying reason for the robustness of our concl usions is the broad assumption that inferior competitors persist by vi rtue of greater dispersal ability and/or lower mortality rates. Furthe r work on the forces allowing multispecies coexistence is thus essenti al for understanding the effects of habitat destruction on extinction.