Recent years have seen great enthusiasm for the idea that populations experiencing different selective pressures will diverge genetically, perhaps to the point of speciation. Ian Wang examined 17 species of Anolis lizards to determine the extent to which genetic differences between populations were a function of ecological differences in the environments they occupy versus geographic differences. Across all 17 species, geography explained twice as much of the variation as did ecological differences, although patterns varied from one species to another. These results suggest that although adaptation to different environment plays some role in driving genetic differentiation, other factors are equally or more important in most cases.

Jonathan Losos