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Science 4 September 2009:
Vol. 325. no. 5945, pp. 1212 - 1213
DOI: 10.1126/science.1179326
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Perspectives

Evolution:

Genetic Constraints on Adaptation?

Juha Merilä

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.

Ecological Genetics Research Unit, Department of Biological and Environmental Sciences, Post Office Box 65, FI-00014 University of Helsinki, Finland.

E-mail: juha.merila{at}helsinki.fi

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Science. ISSN 0036-8075 (print), 1095-9203 (online)