A phylogenetic analysis of body size evolution in the Anolis roquet group (Sauria : Iguanidae): character displacement or size assortment?

The important role that competition plays in structuring communities is wel l documented; however, the role of competition in an evolutionary context r emains unclear. Evolutionary investigations into the role of competition ha ve often focused on the process of character displacement, and a good examp le of this is the evolution of body size in the Anolis lizards of the Carib bean islands. Previous work on the A. roquet species group has taken a phyl ogenetic approach and concluded that patterns of body size differences are not caused by character displacement but are a result of size assortment. U sing a phylogenetic reconstruction based on the sequence of the cytochrome b gene (cyt-b) and ancestral character-state reconstruction methods, we inv estigated the roles of character displacement and size assortment. Our resu lts indicated that size assortment alone was insufficient to explain the ob served patterns of body size differences. Furthermore, we found that change in body size was associated with a change in allopatry/sympatry, thus supp orting the character-displacement hypothesis. We conclude that patterns of body size differences in the A. roquet species group appear to be the resul t of a combination of character displacement and size assortment because ch aracter displacement was only found to be possible on three occasions.