Data from: The effect of historical legacy on adaptation: do closely related species respond to the environment in the same way?

The many documented examples of parallel and convergent evolution in similar environments are strong evidence for the role of natural selection in the evolution of trait variation. However, species may respond to selection in different ways; idiosyncrasies of their evolutionary history may affect how different species respond to the same selective pressure. To determine whether evolutionary history affects trait-environment associations in a recently diverged lineage, we investigated within-species trait-environment associations in the white proteas, a closely related monophyletic group. We first used MANOVAs to determine the relative importance of shared response to selection, evolutionary history, and unique responses to selection on trait variation. We found that on average, similar associations to the environment across species explained trait variation, but that the species had different mean trait values. We also detected species-specific associations of traits to the environmental gradients. To identify the traits associated uniquely to the environment we used a structural equation model. Our analysis showed that the species differed in how their traits were associated with each of the environmental variables. Further, in the cases of two root traits (root mass and root length:mass ratio), two species differed in the direction of their associations (e.g. populations in one species had heavier roots in warmer areas, and populations in the other species had lighter roots in warmer areas). Our study shows that even in a closely related group of species, evolutionary history may have an effect on both the size and direction of adaptations to the environment.诸多已被记录的、发生在相似环境中的平行演化（parallel evolution）与趋同演化（convergent evolution）案例，为自然选择在性状变异演化过程中的作用提供了坚实证据。然而，不同物种对选择压力的响应方式可能存在差异；其演化历史的独特性，会影响不同物种对同一选择压力的响应模式。为探究演化历史是否会影响新近分化支系内的性状-环境关联，我们以亲缘关系密切的单系群——白色山龙眼（white proteas）为研究对象，分析了种内的性状-环境关联模式。我们首先采用多元方差分析（Multivariate Analysis of Variance, MANOVA），以明确共有选择响应、演化历史以及独特选择响应对性状变异的相对重要性。研究结果显示，平均而言，不同物种间共有的环境关联模式可解释性状变异，但各物种的平均性状值存在差异。同时，我们还检测到了物种特有的性状与环境梯度间的关联模式。为筛选出仅与环境相关的性状，我们采用了结构方程模型（Structural Equation Model, SEM）。分析结果表明，各物种的性状与各类环境变量之间的关联模式存在差异。此外，针对两项根系性状（根生物量以及根长-生物量比），两个物种的关联方向存在显著差异：例如，一个物种的种群在温暖区域根系生物量更高，而另一物种的种群在温暖区域根系生物量更低。本研究表明，即便是亲缘关系密切的物种类群，演化历史仍可能会对物种适应环境的效应强度与作用方向产生影响。