Comparative Study of Adaptive Radiation in Iguanian Lizards

Washington University, Saint Louis MO

Investigators

Abstract

9982736 Losos, Larson & deQueiroz A central goal of biology is to understand processes responsible for biodiversity. Of particular interest are "adaptive radiations"-situations in which one ancestral species diversified to produce a variety of descendants adapted to use different parts of the environment. Most previous studies of adaptive radiation have emphasized unique features of different radiations rather than a search for common patterns. Because these studies differ in type of organism, time scale, method of analysis, and characters considered, it is perhaps not surprising that comparisons of these studies reveal more differences than similarities. What is needed is a comparative study of adaptive radiation among closely related organisms using consistent methodology to test the hypothesis that general patterns of adaptive radiation exist. Regular patterns in the evolution of Anolis lizards on different Caribbean islands suggest that adaptive radiations may evolve in similar ways. Whether other groups of lizards show similar patterns is unknown. We propose to study independent radiations of iguanian lizards to test hypotheses suggested by our studies of Caribbean anoles. The integrative and multidisciplinary approaches to the study of adaptive evolution and radiation developed in our earlier studies will be extended to mainland anoles, Australian agamids, Liolaemus, and Sceloporus. We focus on iguanian lizards because they share, at a broad level, similarities in body form, behavior, and ecology. Each group is a worthy subject in its own right; in addition, their close evolutionary relationship to Caribbean anoles makes them ideal for testing hypotheses about adaptive radiation derived from our studies of Caribbean anoles. For each lizard group, we will derive evolutionary trees using data from DNA. Using these trees, we will test the hypotheses that evolutionary change in body form is linked to evolutionary change in functional capabilities which, in turn, lead to evolutionary change in habitat use and behavior. To test these hypotheses, field studies of behavior and ecology will be complemented by laboratory studies of morphology and functional capabilities. We will then compare the pattern of evolutionary diversification in each lizard group to see if similarities exist or, conversely, whether each group has had its own unique evolutionary path.