Data from: Correlated responses to clonal selection in populations of Daphnia pulicaria: mechanisms of genetic correlation and the creative power of sex

Genetic correlations among traits alter evolutionary trajectories due to indirect selection. Pleiotropy, chance linkage, and selection can all lead to genetic correlations, but have different consequences for phenotypic evolution. We sought to assess the mechanisms contributing to correlations with size at maturity in the cyclic parthenogen Daphnia pulicaria. We selected on size in each of four populations that differ in the frequency of sex, and evaluated correlated responses in a life table. Size at advanced adulthood, reproductive output, and adult growth rate clearly showed greater responses in high sex populations, with a similar pattern in neonate size and r. This pattern is expected only when trait correlations are favored by selection and the frequency of sex favors the creation and demographic expansion of highly fit clones. Juvenile growth and age at maturity did not diverge consistently. The inter-clutch interval appeared to respond more strongly in low sex populations, but this was not statistically significant. Our data support the hypothesis that correlated selection is the strongest driver of genetic correlations, and suggest that in organisms with both sexual and asexual reproduction, adaptation can be enhanced by recombination.

性状间的遗传相关可通过间接选择改变演化路径。多效性（Pleiotropy）、随机连锁与选择均可引发遗传相关，但三者对表型演化的影响存在显著差异。本研究旨在探究周期性孤雌生殖生物（cyclic parthenogen）普氏溞（Daphnia pulicaria）中成体体型相关性状关联的潜在机制。我们针对四个性频率存在差异的种群开展体型选择实验，并通过生命表评估其相关响应。成年后期体型、繁殖产出与成体生长率在高性频率种群中均呈现出更为显著的响应，新生个体体型与内禀增长率r也呈现出相似的模式。该模式仅在两种条件下成立：一是性状关联受到选择的青睐，二是性频率有利于高适合度克隆的产生与种群扩张。幼体生长速率与成熟年龄则未呈现出一致性的分化。产卵间隔在低性频率种群中似乎呈现出更强的响应，但该结果未达到统计学显著性。本研究数据支持‘相关选择是遗传关联的最强驱动因素’这一假说，并表明：对于兼具有性与无性生殖的生物而言，重组可有效提升其适应性。