Data from: Genetic change for earlier migration timing in a population of pink salmon

To predict how climate change will influence populations it is necessary to understand the mechanisms, particularly microevolution and phenotypic plasticity, which allow populations to persist in novel environmental conditions. Although evidence for climate-induced phenotypic change in populations is widespread, evidence documenting that these phenotypic changes are due to microevolution is exceedingly rare. In this study we use 32 years of genetic data (17 complete generations) to determine whether there has been genetic change toward earlier migration timing in a population of pink salmon that shows phenotypic change; average migration time occurs nearly 2 weeks earlier than it did 40 years ago. Experimental genetic data support the hypothesis that there has been directional selection for earlier migration timing, resulting in a substantial decrease in the late migrating phenotype (from >30% to <10% of the total abundance). From 1983-2011 there was a significant decrease – over three fold – in the frequency of a genetic marker for late migration timing, but there were minimal changes in allele frequencies at other neutral loci. These results demonstrate there has been rapid microevolution for earlier migration timing in this population. Circadian rhythm genes, however, did not show any evidence for selective changes from 1993-2009.若要预测气候变化对种群的影响，需明晰促使种群在全新环境中存续的核心机制，尤其是微进化（microevolution）与表型可塑性（phenotypic plasticity）。尽管种群中由气候驱动的表型变化证据已较为普遍，但能够证实此类表型变化由微进化驱动的相关证据却极为稀缺。本研究依托32年的遗传数据（涵盖17个完整世代），针对出现表型变化的粉红鲑（pink salmon）种群展开分析，以明确其是否发生了朝着更早洄游时间的遗传改变；该种群的平均洄游时间较40年前提前了近两周。实验遗传数据支持如下假说：种群已针对更早洄游时间产生定向选择（directional selection），致使晚洄游表型的种群占比大幅下降——从总丰度的30%以上降至10%以下。1983年至2011年间，用于标识晚洄游性状的遗传标记（genetic marker）的频率出现了显著下降，降幅超过三倍；但其他中性基因座（neutral loci）的等位基因频率（allele frequencies）仅发生了微小变化。上述结果证明，该种群已发生了针对更早洄游时间的快速微进化。但1993年至2009年间，昼夜节律基因（circadian rhythm genes）未表现出任何选择性变化的迹象。