Disentangling the drivers of genetic differentiation is one of the cornerstones in evolution. This is because genetic diversity, and the way in which it is partitioned within and among populations across space, is an important asset for the ability of populations to adapt and persist in changing environments. We tested three major hypotheses accounting for genetic differentiation—isolation-by-distance (IBD), isolation-by-environment (IBE) and isolation-by-resistance (IBR)—in the annual plant Arabidopsis thaliana across the Iberian Peninsula, the region with the largest genomic diversity. To that end, we sampled, genotyped with genome-wide SNPs, and analyzed 1772 individuals from 278 populations distributed across the Iberian Peninsula. IBD, and to a lesser extent IBE, were the most important drivers of genetic differentiation in A. thaliana. In other words, dispersal limitation, genetic drift, and to a lesser extent local adaptation to environmental gradients, accounted for the within- and among-population distribution of genetic diversity. Analyses applied to the four Iberian genetic clusters, which represent the joint outcome of the long demographic and adaptive history of the species in the region, showed similar results except for one cluster, in which IBR (a function of landscape heterogeneity) was the most important driver of genetic differentiation. Using spatial hierarchical Bayesian models, we found that precipitation seasonality and topsoil pH chiefly accounted for the geographic distribution of genetic diversity in Iberian A. thaliana. Overall, the interplay between the influence of precipitation seasonality on genetic diversity and the effect of restricted dispersal and genetic drift on genetic differentiation emerges as the major forces underlying the evolutionary trajectory of Iberian A. thaliana.

中文翻译：

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拟南芥区域遗传分化的生态，遗传和进化驱动力。

弄清遗传分化的驱动因素是进化的基石之一。这是因为遗传多样性及其在空间内各种群之间以及在各种群之间的分配方式，是提高种群适应和在不断变化的环境中生存的能力的重要资产。我们测试了三个主要假说，这些假说解释了该地区伊比利亚半岛的年度植物拟南芥中的遗传分化-按距离隔离（IBD），按环境隔离（IBE）和按电阻隔离（IBR）。具有最大的基因组多样性。为此，我们对全基因组SNP进行了采样，基因分型，并分析了伊比利亚半岛278个人口中的1772个个体。IBD和较小程度的IBE是拟南芥遗传分化的最重要驱动力。换句话说，散布限制，遗传漂移以及在较小程度上对环境梯度的局部适应，是遗传多样性在种群内和种群间分布的原因。应用于四个伊比利亚遗传集群的分析代表了该地区物种的长期人口统计和适应历史的联合结果，结果相似，但其中一个集群除外，其中IBR（景观异质性的函数）最为重要基因分化的驱动力。使用空间分层贝叶斯模型，我们发现降水季节和表土pH值主要是伊比利亚拟南芥遗传多样性的地理分布。总体，