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选择作用，限制局部适应性演化。这一过程被称为“基因淹没（gene swamping）”，可使种群间的遗传多样性趋于均质化，并降低物种抵御快速环境变化的能力。我们以分布于巴哈马群岛7座岛屿的棕色安乐蜥（Anolis sagrei）为研究对象，利用微卫星标记（microsatellite markers）估算了岛屿间的基因流，随后分析了热性能与岛屿温度之间的相关性。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。岛屿间的基因流随其平均温度差异的增大而减弱，即便这些岛屿彼此相邻亦是如此。上述数据表明，表型变异可能源于以下三种情形之一：1）局部遗传适应，通过对迁入个体的选择维持热最适温度的变异；2）不可逆转的适应性可塑性，导致迁入个体适合度下降；或3）固定遗传差异与可塑性的共同作用。总体而言，我们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。