Data from: Rapid independent trait evolution despite a strong pleiotropic genetic correlation

Genetic correlations are the most commonly studied of all potential constraints on adaptive evolution. We present a comprehensive test of constraints caused by genetic correlation, comparing empirical results to predictions from theory. The additive genetic correlation between the filament and corolla tube in wild radish flowers is very high in magnitude, estimated with good precision (0.85 ± 0.06), and is caused by pleiotropy. Thus, evolutionary changes in the relative lengths of these two traits should be constrained. Still, artificial selection produced rapid evolution of these traits in opposite directions, so that the difference between them in one replicate increased by six standard deviations relative to controls in only nine generations. This would result in a 54% increase in relative fitness based on a previous estimate of natural selection in this population, and would produce the phenotypes found in the most extreme species in the family Brassicaceae in less than 100 generations. These responses were within theoretical expectations and much slower than if the genetic correlation was zero; thus, there was evidence for constraint. These results, coupled with comparable results from other species, show that evolution can be rapid despite the constraints caused by genetic correlations.

遗传相关（genetic correlation）是适应性演化（adaptive evolution）各类潜在约束中研究最为广泛的一类。我们针对遗传相关引发的演化约束开展了综合性检验，将实证结果与理论预测进行对比分析。野萝卜（wild radish）的花中，花丝（filament）与花冠筒（corolla tube）间的加性遗传相关（additive genetic correlation）强度极高，估算精度良好（0.85 ± 0.06），且该相关由多效性（pleiotropy）所致。据此，这两个性状相对长度的演化改变理应受到约束。尽管如此，人工选择（artificial selection）仍使二者朝着相反方向快速演化：仅历经9代，一个重复组中二者的性状差值较对照组提升了6个标准差（standard deviations）。基于该种群此前的自然选择估算结果，这将使相对适合度（relative fitness）提升54%，且仅需不到100代即可产生十字花科（Brassicaceae）中表型最极端物种所具备的表型。这些演化响应符合理论预期，且远慢于遗传相关为零的情形；由此可证实演化约束的存在。结合其他物种的同类研究结果，本研究表明：即便存在遗传相关带来的演化约束，生物演化仍可快速推进。