Species often comprise several ecotypes, distinct populations that occupy different habitats. Ecotypes can persist over long time periods, even with substantial gene flow between them, which raises the question of how they maintain their locally adaptive phenotypes over time. Hager et al. examined the genetic basis of two traits, tail length and coat color, that define the forest and prairie ecotypes of deer mice. They found a large chromosomal inversion that links redder coats and longer tails in the forest ecotype. Modeling suggests that the inversion originated under divergent selection many thousands of generations ago and likely provided a benefit to the forest ecotype by suppressing recombination despite gene flow.
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