Genomic signatures of evolutionary rescue in bats surviving white-nose syndrome

Evolutionary rescue can help populations avoid extinction after abrupt environmental change through the rapid evolution of advantageous traits that promote population growth. However, evolutionary rescue is thought to be rare in taxa with long generation times because demographic declines towards extirpation are likely to outpace the acquisition of adaptive de novo mutations. Adaptive alleles must therefore be selected from standing genetic variation, a process that leaves few detectable genomic signatures. Here, we provide the first genetic evidence for evolutionary rescue in bat populations affected by white nose syndrome (WNS). By comparing genetic samples from before and after little brown bat populations were decimated by WNS, we identified signatures of soft selection on standing genetic variation. This selection occurred at multiple loci in genes linked to hibernation behavior, suggesting that changes in hibernation have allowed these bats to survive infection with WNS. Through these findings, we show that evolutionary rescue can be a conservation-relevant process even in slowly reproducing taxa facing extinction.

当种群遭遇突发环境变化时，进化拯救（evolutionary rescue）可通过快速演化出促进种群增长的有利性状，帮助种群避免灭绝。然而，学界普遍认为进化拯救在世代周期较长的类群中较为罕见，因为种群向灭绝的数量衰退速度往往快于适应性新发突变的获得速率。因此，适应性等位基因需从现存遗传变异中被选择出来，这一过程几乎不会留下可检测的基因组特征。本研究首次为受白鼻综合征（white nose syndrome, WNS）影响的蝙蝠种群发生进化拯救提供了遗传学证据。通过对比小棕蝠种群在遭受白鼻综合征重创前后的遗传样本，我们鉴定出了针对现存遗传变异的软选择（soft selection）特征。该选择作用于与冬眠行为相关的多个基因位点，表明冬眠习性的改变帮助这些蝙蝠成功抵御了白鼻综合征的感染。本研究结果表明，即便在面临灭绝威胁、繁殖缓慢的类群中，进化拯救也可成为与物种保护相关的重要过程。