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Although rapid adaptive changes in morphology on ecological time scales are now well documented in natural populations, the effects of such changes on whole-organism performance capacity and the consequences on ecological dynamics at the population level are often unclear. Here we show how lizards have rapidly evolved differences in head morphology, bite strength, and digestive tract structure after experimental introduction into a novel environment. Despite the short time scale ( approximately 36 years) since this introduction, these changes in morphology and performance parallel those typically documented among species and even families of lizards in both the type and extent of their specialization. Moreover, these changes have occurred side-by-side with dramatic changes in population density and social structure, providing a compelling example of how the invasion of a novel habitat can evolutionarily drive multiple aspects of the phenotype.

Caribbean Anolis lizards are often cited as a textbook example of adaptive radiation. Similar morphologies (ecomorphs) have originated in similar ecological settings on different large islands in the West Indies. However, relatively little is known about one of the morphologically most specialized and divergent ecomorphs: the twig anoles. Here, we investigate aspects of morphology, dewlap size, locomotor and bite performance, structural habitat and diet of the poorly known twig anole, Anolis sheplani from Hispaniola. Few observations have previously been made of this species in its natural habitat, and few quantitative data on its natural history are available. A. sheplani is an extreme twig anole with respect to its morphology, performance capacities, and ecological niche. Males and females of this species do not differ from each other in body dimensions, performance or habitat use, but males do have a bigger dewlap than females. We present data for 25 individuals and compare them with data for other Greater Antillean anoles. It becomes apparent that twig anoles constitute a large component of the morphological, functional, and ecological diversity of Anolis lizards. Small twig anoles such as A. sheplani appear to be pushing the boundaries of morphospace and are thus crucial in our understanding of the evolution of phenotypic diversity.

As more data have become available on lizard diets in the past few decades, researchers have stressed the importance of lizards as pollinators and seed dispersers. Whereas large body size has been traditionally put forward as a major biological factor "allowing" herbivory and frugivory in lizards, a recent review of frugivory and seed dispersal by lizards showed that frugivory might be considered to be a typical island phenomenon, independent of body size. Here we show that frugivory is correlated with lizard body size among a group of syntopic Anolis species in Jamaica, with larger species eating more fruit. Additionally, the size of the fruits consumed is significantly related to lizard body size. Multiple regression analyses show that this is largely a pure body size effect as head shape or residual bite force are uncorrelated to overall fruit size. Moreover, we demonstrate that among polychrotid (Anolis-like) lizards in general, those that consume fruit are on average larger than those that do not. Lizards from the mainland were not significantly different in body size from island species. We thus suggest that fruit consumption in polychrotid lizards is mediated by large body size whether living on islands or not.