Data from: Spatial variation in climate mediates gene flow across an island archipelago

High levels of gene flow among partially isolated populations can
overwhelm selection and limit local adaptation. This process, known as
“gene swamping,” can homogenize genetic diversity among populations and
reduce the capacity of a species to withstand rapid environmental change.
We studied brown anole lizards (Anolis sagrei) distributed across seven
islands in The Bahamas. We used microsatellite markers to estimate gene
flow among islands and then examined the correlation between thermal
performance and island temperature. The thermal optimum for sprint
performance was correlated with both mean and maximum island temperature
whereas performance breadth was not correlated with any measure of
temperature variation. Gene flow between islands decreased as the
difference between mean island temperatures increased, even when those
islands were adjacent to one another. These data suggest that phenotypic
variation is the result of either 1) local genetic adaptation with
selection against immigrants maintaining variation in the thermal optimum,
2) irreversible forms of adaptive plasticity such that immigrants have
reduced fitness, or 3) an interaction between fixed genetic differences
and plasticity. In general, the patterns of gene flow we observed suggest
that local thermal environments represent important ecological filters
that can mediate gene flow on relatively fine geographic scales.