Extinction-Mediated Competition: The Anolis Lizards and Insectivorous Birds of the West Indies

Abstract

Three lines of evidence suggest that West Indian Anolis lizards and insectivorous birds compete for their arthropod prey: (1) Extensive diet overlaps exist between anoles and insectivorous birds; (2) West Indian anoles are food-limited; (3) there are reciprocal changes in the population densities of anoles and insectivorous birds on islands of different area. On small islands anoles are relatively abundant and on large islands insectivorous birds are relatively abundant. Differences in extinction rates may account for this pattern. West Indian anoles are apparently immune to extinction, but avian extinctions are a regular phenomenon and occur most frequently on small islands. Therefore, if anoles experience ecological release after the extinction of an avian insectivore, anoles should be progressively more abundant on progressively smaller islands. Concomitantly insectivorous birds should be progressively more abundant on progressively larger islands, as is the case.