Cast adrift on an island: Introduced populations experience an altered balance between selection and drift

Abstract

A long-standing question in evolutionary biology is what becomes of adaptive traits when a species expands its range into novel environments. Here, we report the results of a study on an adaptive colour pattern polymorphism (stripes) of the coqui frog, Eleutherodactylus coqui, following its introduction toHawaii fromPuertoRico.We compared population differentiation (φST and FST) for the stripes locus-which underlies this colour pattern polymorphism-with neutral microsatellite loci to test for a signature of selection among native and introduced populations. Among native populations, φST and FST for stripes were lower than expected under the neutral model, suggesting uniformbalancing selection. Alternatively, among introduced populations, φST and F ST for stripes did not differ from the neutral model. These results suggest that the evolutionary dynamics of this previously adaptive trait have become dominated by random genetic drift following the range expansion. © 2011 The Royal Society.