Nature 387, 70 - 73 (01 May 1997); doi:10.1038/387070a0

Adaptive differentiation following experimental island colonization in Anolis lizards

Jonathan B. Losos^*, Kenneth I. Warheitt^† & Thomas W. Schoener^‡

^*Department of Biology, Campus Box 1137, Washington University, St Louis, Missouri 63130-4899, USA
^&;dagger;Department offish and Wildlife, 600 Capitol Way North, Olympia, Washington 98501-1091 and Burke Museum, DB- 10, University of Washington, Seattle, Washington 98195, USA
^‡Section of Evolution and Ecology and Division of Environmental Studies, University of California, Davis, California 95616, USA

If colonizing populations are displaced into an environment that is often very different from that of their source¹, they are particularly likely to diverge evolutionarily, the more so because they are usually small and thus likely to change by genetic restructuring or drift^2,3. Despite its fundamental importance, the consequence of colonization for traits of founding populations have primarily been surmised from static present-day distributions^1,2,4,5, laboratory experiments⁶ and the outcomes of haphazard human introductions^7–9, rather than from replicated field experiments. Here we report long-term results of just such an experimental study. Populations of the lizard Anolis sagrei, introduced onto small islands from a nearby source, differentiated from each other rapidly over a 10–14-year period. The more different the recipient island's vegetation from that of the source, the greater the magnitude of differentiation. Further, the direction of differentiation followed an expectation based on the evolutionary diversification of insular Anolis over its entire geographic range. In addition to providing a glimpse of adaptive dynamics in one of the most extensive generic radiations on earth, the results lend support to the general argument that environment determines the evolution of morphology.

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