Am Nat. 2023 Jul;202(1):18-39. doi: 10.1086/724579. Epub 2023 May 25.
AbstractPrevious theory has shown that assortative mating for plastic traits can maintain genetic divergence across environmental gradients despite high gene flow. Yet these models did not examine how assortative mating affects the evolution of plasticity. We here describe patterns of genetic variation across elevation for plasticity in a trait under assortative mating, using multiple-year observations of budburst date in a common garden of sessile oaks. Despite high gene flow, we found significant spatial genetic divergence for the intercept, but not for the slope, of reaction norms to temperature. We then used individual-based simulations, where both the slope and the intercept of the reaction norm evolve, to examine how assortative mating affects the evolution of plasticity, varying the intensity and distance of gene flow. Our model predicts the evolution of either suboptimal plasticity (reaction norms with a slope shallower than optimal) or hyperplasticity (slopes steeper than optimal) in the presence of assortative mating when optimal plasticity would evolve under random mating. Furthermore, a cogradient pattern of genetic divergence for the intercept of the reaction norm (where plastic and genetic effects are in the same direction) always evolves in simulations with assortative mating, consistent with our observations in the studied oak populations.
先前的理论表明，尽管基因流动很高，但对可塑性状的同型交配可以在环境梯度上维持遗传分化。然而，这些模型并没有研究同型交配如何影响可塑性的进化。在这里，我们使用在一个固定栎属树木的公共花园中多年观察到的芽期数据，描述了在同型交配下，一个性状的可塑性在海拔上的遗传变异模式。尽管基因流动很高，但我们发现了反应规范的截距（intercept）存在显著的空间遗传分化，而斜率（slope）则没有。然后，我们使用基于个体的模拟，其中反应规范的斜率和截距都在进化，来研究同型交配如何影响可塑性的进化，改变基因流的强度和距离。我们的模型预测，在同型交配存在的情况下，当随机交配下会进化出最佳可塑性时，会出现次优可塑性（反应规范的斜率比最佳斜率浅）或超可塑性（斜率比最佳斜率陡）的进化。此外，反应规范截距的共梯度遗传分化模式（其中可塑性和遗传效应方向相同）总是在同型交配的模拟中进化，这与我们在研究的栎属种群中的观察结果一致。
