Data from: Strong selection barriers explain microgeographic adaptation in wild salamander populations

Microgeographic adaptation occurs when populations evolve divergent fitness advantages across the spatial scales at which focal organisms regularly disperse. Although an increasing number of studies find evidence for microgeographic adaptation, the underlying causes often remain unknown. Adaptive divergence requires some combination of limited gene flow and strong divergent natural selection among populations. In this study, we estimated the relative influence of selection, gene flow and the spatial arrangement of populations in shaping patterns of adaptive divergence in natural populations of the spotted salamander (Ambystoma maculatum). Within the study region, A. maculatum co-occur with the predatory marbled salamander (A. opacum) in some ponds, and past studies have established a link between predation risk and adaptive trait variation in A. maculatum. Using 14 microsatellite loci, we found a significant pattern of genetic divergence among A. maculatum populations corresponding to levels of A. opacum predation risk. Additionally, A. maculatum foraging rate was strongly associated with predation risk, genetic divergence and the spatial relationship of ponds on the landscape. Our results indicate the sorting of adaptive genotypes by selection regime and strongly suggest that substantial selective barriers operate against gene flow. This outcome suggests that microgeographic adaptation in A. maculatum is possible because strong antagonistic selection quickly eliminates maladapted phenotypes despite ongoing and substantial immigration. Increasing evidence for microgeographic adaptation suggests a strong role for selective barriers in counteracting the homogenizing influence of gene flow.微地理适应（Microgeographic adaptation）指种群在其目标生物常规扩散的空间尺度范围内，演化出差异化适合度优势的过程。尽管越来越多的研究找到了微地理适应的相关证据，但其背后的潜在成因往往仍不明确。适应性分化的发生，需要种群间兼具有限基因流与强烈的歧向自然选择两种条件。本研究以斑点钝口螈（Ambystoma maculatum）的自然种群为研究对象，评估了选择作用、基因流以及种群空间分布格局，对其适应性分化模式塑造的相对影响。在本研究区域内，部分池塘中斑点钝口螈与捕食性云斑钝口螈（Ambystoma opacum）共存；既往研究已证实，斑点钝口螈的捕食风险与其适应性性状变异之间存在显著关联。我们利用14个微卫星位点（microsatellite loci），发现斑点钝口螈种群间存在显著的遗传分化模式，且该分化程度与云斑钝口螈的捕食风险等级相对应。此外，斑点钝口螈的觅食速率与捕食风险、遗传分化以及景观内池塘的空间分布关系密切相关。本研究结果表明，选择体系会对适应性基因型进行筛选，且强烈暗示存在显著的选择障碍以阻碍基因流。该结果表明，斑点钝口螈的微地理适应之所以能够实现，是因为尽管存在持续且大量的个体迁入，强烈的拮抗选择仍能快速清除不适宜表型。越来越多关于微地理适应的研究证据表明，选择障碍在抵消基因流的同质化效应方面发挥着重要作用。