LAUSR

The means by which assemblages of closely related species form and persist have become a primary focus in evolution and ecology. Comparative studies of island and mainland assemblages may provide novel insight into assemblage evolution. The isolation and relative simplicity of islands may foster distinct evolutionary rates and endpoints relative to mainland areas. Adaptive radiations on islands are expected to result in assemblages that include close phylogenetic relatives but are phenotypically diverse, whereas predatorand competitor-rich mainland environments may produce phenotypically uniform assemblages. Here we use a nearly complete phylogeny and morphological data for 336 species of Anolis lizards to test for differences in phenotypic and phylogenetic structure in 91 mainland versus 76 island assemblages. We present three main conclusions: (1) both mainland and island assemblages comprise close relatives that are phenotypically similar; (2) mainland assemblages tend to be more clustered than island assemblages according to both phylogenetic and phenotypic measures; and (3) differences in degree of phenotypic clustering between mainland and island assemblages are not explained by differences in phylogenetic clustering alone. We interpret these results in terms of biogeography and differences between mainland and island environments.