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）是适应性进化（adaptive evolution）各类潜在限制因素中研究最为广泛的一类。本研究针对遗传相关引发的进化限制开展了全面检验，将实证结果与理论预测进行了对比分析。野萝卜（wild radish）花中，花丝（filament）与花冠筒（corolla tube）之间的加性遗传相关（additive genetic correlation）数值极高，且估算精度良好（0.85 ± 0.06），该相关由多效性（pleiotropy）所致。因此，这两个性状相对长度的进化改变理应受到限制。然而，人工选择（artificial selection）却使这两个性状朝着相反方向发生了快速进化：在一个实验重复组中，仅经过9代，二者的相对长度差值相较于对照组便提升了6个标准差（standard deviation）。基于该种群此前的自然选择估算结果，这一变化将使相对适合度（relative fitness）提升54%；且仅需不到100代，便可演化出十字花科（Brassicaceae）中表型最极端的物种所具有的表型。这些进化响应符合理论预期，且其速率远低于遗传相关为零时的情况；由此可见，确实存在进化限制的证据。结合其他物种的同类研究结果，本研究结果表明：即便存在遗传相关带来的进化限制，进化过程仍可快速发生。