Morphological diversification and adaptive radiation: A comparison of two diverse lizard clades

We compared the morphological diversity (i.e., the amount of morphological space occupied) of two similar clades, the lizard genera Anolis and Scelopo rus. These species-rich monophyletic clades are similar in body size, age o f origin, and many aspects of their natural history. We examined a number o f morphological traits whose variation is likely to represent adaptation to different aspects of the environment, including body size, limb proportion s, head dimensions, and tail length. Examination of the position of species in multidimensional space, based on a principal components analysis, indic ates that the morphological diversity of Anolis, which we refer to as dispa rity, is significantly greater than that of Sceloporus. One potential expla nation for this pattern is that morphological diversification in Anolis was facilitated by the evolution of subdigital toe-pads, which allow anoles to use the environment in ways not available to Sceloporus. The geographic lo cation of diversification (tropical and subtropical for Anolis, arid for Sc eloporus) may also have been important.