Data from: Local adaptation and ecological differentiation under selection, migration and drift in Arabidopsis lyrata

How the balance between selection, migration and drift influences the evolution of local adaptation has been under intense theoretical scrutiny. Yet, empirical studies that relate estimates of local adaptation to quantification of gene flow and effective population sizes have been rare. Here, we conducted a reciprocal transplant trial, a common garden trial, and a whole-genome based demography analysis to examine these effects among Arabidopsis lyrata populations from two altitudinal gradients in Norway. Demography simulations indicated that populations within the two gradients are connected by gene flow (0.1 < 4Nem < 11) and have small effective population sizes (Ne < 6,000), suggesting that both migration and drift can counteract local selection. However, the three-year field experiments showed evidence of local adaptation at the level of hierarchical multi-year fitness, attesting to the strength of differential selection. In the lowland habitat, local superiority was associated with greater fecundity, while viability accounted for fitness differences in the alpine habitat. We also demonstrate that flowering time differentiation has contributed to adaptive divergence between these locally adapted populations. Our results show that despite the estimated potential of gene flow and drift to hinder differentiation, selection among these A. lyrata populations has resulted in local adaptation.

选择、迁移与遗传漂变之间的平衡如何影响本地适应的演化，长期以来都是理论学界密切关注的核心课题。然而，将本地适应的量化评估与基因流及有效种群大小（Ne）的测算结果相关联的实证研究却较为罕见。本研究针对挪威两条海拔梯度下的 lyrate 鼠耳芥（Arabidopsis lyrata）种群，开展了互惠移植试验（reciprocal transplant trial）、共同花园试验（common garden trial）以及基于全基因组的种群人口统计学分析，以探究上述因素的作用效应。种群人口模拟结果显示，两条海拔梯度内的种群间存在基因流（0.1 < 4Nem < 11），且有效种群规模较小（Ne < 6000），这表明迁移与遗传漂变均可能抵消本地选择的作用。不过，为期三年的野外实验结果却在多年分层适合度层面呈现出本地适应的证据，证实了差异化选择的强度。在低地生境中，本地种群的生存优势源于更高的繁殖力；而在高山生境中，适合度差异则由存活率决定。本研究还证实，开花时间的分化推动了这些本地适应种群间的适应性分化。研究结果表明，尽管基因流与遗传漂变的估算结果显示其可能阻碍种群分化，但这些 lyrate 鼠耳芥种群间的选择作用仍促成了本地适应。