Kellogg Biological Station, Michigan State University, 3700 E. Gull Lake Dr., Hickory Corners, MI 49060, USA.
J Evol Biol. 2012 Aug;25(8):1636-49. doi: 10.1111/j.1420-9101.2012.02548.x. Epub 2012 Jun 11.
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 with the environmental gradients. To identify the traits associated uniquely with 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.
在相似环境中，大量有记载的平行和趋同进化的例子为自然选择在性状变异进化中的作用提供了有力证据。然而，物种可能以不同的方式对选择做出反应；它们进化历史的特殊性可能会影响不同物种对相同选择压力的反应方式。为了确定进化历史是否会影响最近分化谱系中性状与环境的关联，我们调查了近缘的白色金合欢属植物中种内性状与环境的关联。我们首先使用多变量方差分析来确定对选择的共同反应、进化历史和对选择的独特反应对性状变异的相对重要性。我们发现，平均而言，物种之间对环境的相似关联解释了性状变异，但物种的平均性状值不同。我们还检测到性状与环境梯度的种特异性关联。为了确定与环境相关的独特性状，我们使用了结构方程模型。我们的分析表明，物种在其性状与每个环境变量的关联方式上存在差异。此外，对于两个根性状（根质量和根长/质量比），两个物种的关联方向也不同（例如，一个物种的种群在温暖地区的根较重，而另一个物种的种群在温暖地区的根较轻）。我们的研究表明，即使在一个密切相关的物种群体中，进化历史也可能对环境适应的大小和方向产生影响。
