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）指种群在其目标物种常规扩散的空间尺度范围内，演化出分化的适合度优势的现象。尽管目前针对微地理适应的相关研究日益增多，但该现象背后的潜在驱动机制往往仍不明确。适应性分化需要种群间兼具有限基因流与强烈趋异自然选择的共同作用。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的相对影响。在本研究区域内，部分池塘中斑点钝口螈会与捕食性的云斑钝口螈（Ambystoma opacum）共存，且既往研究已证实捕食压力与斑点钝口螈的适应性性状变异存在关联。本研究利用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，且该遗传分化与云斑钝口螈的捕食压力水平显著相关。此外，斑点钝口螈的觅食速率与捕食压力、遗传分化以及研究区域内池塘的空间分布关系均存在显著关联。本研究结果表明选择机制会对适应性基因型进行筛选，并有力暗示存在显著的选择屏障以阻碍基因流。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，但强烈的拮抗选择会快速淘汰非适应性表型。越来越多关于微地理适应的研究证据表明，选择屏障在抵消基因流的均质化影响方面发挥着关键作用。