We compared the morphological
diversity (i.e., the amount of morphological space occupied) of two similar
clades, the lizard genera Anolis and Sceloporus. These
species-rich monophyletic clades are similar in body size, age of origin,
and many aspects of their natural history. We examined a number of
morphological traits whose variation is likely to represent adaptation
to different aspects of the environment, including body size, limb proportions,
head dimensions, and tail length. Examination of the position of
species in multidimensional space, based on a principal components analysis,
indicates that the morphological diversity of Anolis, which we refer
to as disparity, is significantly greater than that of Sceloporus.
One potential explanation 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 location of diversification (tropical and subtropical for
Anolis, arid for Sceloporus) may also have been important.
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