Data for: Immigration counter-acts local micro-evolution of a major fitness component: migration-selection balance in free-living song sparrows

Ongoing adaptive evolution, and resulting ‘evolutionary rescue’ of declining populations, requires additive genetic variation in fitness. Such variation can be increased by gene flow resulting from immigration, potentially facilitating evolution. But, gene flow could in fact constrain rather than facilitate local adaptive evolution if immigrants have low additive genetic values for local fitness. Local migration-selection balance and micro-evolutionary stasis could then result. However, key quantitative genetic effects of natural immigration, comprising the degrees to which gene flow increases the total local additive genetic variance yet counter-acts local adaptive evolutionary change, have not been explicitly quantified in wild populations. Key implications of gene flow for population and evolutionary dynamics consequently remain unclear. Our quantitative genetic analyses of long-term data from free-living song sparrows (Melospiza melodia) show that mean breeding value for local juven...持续的适应性进化以及由此实现的衰退种群"进化拯救（evolutionary rescue）"，有赖于适合度相关的加性遗传变异（additive genetic variation）。此类变异可通过迁入引发的基因流（gene flow）得以增加，从而潜在地推动进化进程。但倘若迁入个体在局部适合度上的加性遗传值较低，那么基因流实则可能制约而非促进局部适应性进化，进而可能形成局部的迁移-选择平衡（migration-selection balance）与微观进化停滞（micro-evolutionary stasis）。然而，自然迁入所带来的关键数量遗传效应（quantitative genetic effects）——即基因流在多大程度上提升了局部总加性遗传方差，同时又抵消了局部适应性进化变化——尚未在野生种群中得到明确量化。因此，基因流对种群与进化动态的关键影响仍未明晰。我们对自由生活的歌带鹀（Melospiza melodia）的长期数据开展的数量遗传分析显示，局部幼体的平均育种值……