Ecological and evolutionary determinants of the species-area relation in Caribbean anoline lizards

Species area relations were studied for anoline lizards on 147 islands in the Caribbean. The relative importance of ecological and evolutionary factors in determining species number varied with island size. On small islands, only ecological factors affect the species-area relation. Further, the importance of different ecological factors such as colonization, competition, and extinction, varied among different types of islands. On landbridge islands, differential extinction as a function of island area appears to play a key role in producing a species-area relation. By contrast, limited colonization success generally prevents ocean islands from accumulating more than two species. Among the larger islands, evolutionary factors are the primary determinant of species number. Detailed examination of several components of evolutionary diversification indicates that the species area relation among the Greater Antilles primarily results because larger islands have increased number of habitat niches occupied and a greater number of closely related species that are ecologically similar and allopatrically distributed; increased subdivision of certain habitats plays a lesser role.