Genetic Constraints on Adaptation?

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Science  04 Sep 2009:
Vol. 325, Issue 5945, pp. 1212-1213
DOI: 10.1126/science.1179326

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According to widely held perception among evolutionary biologists and geneticists, most traits in wild animal and plant populations are heritable, and are thereby able to respond to natural selection. Hence, adaptation and evolution should not be limited by a lack of genetic variability, except on rare occasions (1). On page 1244 of this issue, Kellermann et al. (2) challenge this view, reporting low levels of genetic variation in cold and desiccation tolerance in tropical Drosophila species with narrow geographic distributions. In contrast, widely distributed Drosophila species show much higher levels of genetic variability in the same tolerance traits.