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）是适应性进化各类潜在约束中研究最为普遍的一类。本研究针对遗传相关引发的进化约束开展了系统性检验，将实验观测结果与理论预测进行了比对分析。野萝卜（wild radish）花中花丝（filament）与花冠筒（corolla tube）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）所导致。因此，这两个性状的相对长度演化理应受到约束。然而，人工选择却使得这两个性状朝着相反方向快速演化：在一个实验重复组中，仅经过9代，二者的性状差值相较于对照组便提升了6个标准差。基于该种群此前的自然选择估算结果，这一演化变化将使相对适合度（relative fitness）提升54%，且仅需不到100代即可产生十字花科（Brassicaceae）中极端物种所具备的表型。这些演化响应符合理论预期，且相较于遗传相关为零的情况要缓慢得多，由此证实了进化约束的存在。结合其他物种的类似研究结果，本研究表明即便存在遗传相关所带来的进化约束，演化仍可快速发生。