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.部分隔离种群间的高水平基因流可抵消自然选择作用，限制种群的局部适应性演化。这一过程被称为“基因冲刷（gene swamping）”，可抹平种群间的遗传多样性差异，并降低物种应对快速环境变化的能力。本研究以分布于巴哈马群岛7座岛屿上的棕安乐蜥（Anolis sagrei）为研究对象，采用微卫星标记（microsatellite markers）估算岛屿间的基因流水平，并分析了热性能与岛屿温度之间的相关性。研究发现，疾跑性能的热最适温度与岛屿的平均温度和最高温度均呈显著相关，而性能广度则与任何温度变异指标均无相关性。岛屿间的基因流水平随岛屿平均温度差异的增大而降低，即便这些岛屿彼此相邻亦是如此。上述数据表明，表型变异的产生可能源于以下三种机制之一：1）本地遗传适应——通过对外来个体的选择维持热最适温度的种群间差异；2）不可逆转的适应性表型可塑性，致使外来个体适合度下降；或3）固定遗传差异与表型可塑性的共同作用。总体而言，本研究观测到的基因流模式表明，局部热环境是重要的生态过滤因子，可在相对精细的地理尺度上调控基因流的发生。