The Genetic Limits of Adaptation at a Range’s Edge
A study of the beetle Diorhabda carinulata provides a real-world test of evolutionary theory during a contemporary range expansion. Researchers tracked the evolution of winter dormancy timing as the beetle moved from northern climates with cold winters into southern areas with milder conditions. While populations at the core of the range were well-adapted to their local environment, those at the expanding southern edge showed varied phenotypes, suggesting rapid evolution in response to novel selection pressures. Crucially, the study found that heritable genetic variation—the raw material for adaptation—was high in the core population’s local environment but became undetectable when that same population was tested in the novel edge environment.
Why it might matter to you: For a geneticist, this work highlights a potential constraint on evolutionary rescue in a changing climate: the very process of colonizing new environments may reduce the expression of heritable variation needed for adaptation. This has direct implications for predicting species’ responses to climate change and for conservation strategies that rely on genetic rescue or assisted migration. Understanding the interplay between gene flow, selection, and the environment-specific expression of genetic variation is central to forecasting population persistence.
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