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.性状间的遗传相关会通过间接选择改变演化轨迹。多效性（pleiotropy）、随机连锁（chance linkage）与选择均可导致遗传相关的产生，但三者对表型演化（phenotypic evolution）的影响各不相同。本研究旨在探究周期性孤雌生殖（cyclic parthenogen）物种蚤状溞（Daphnia pulicaria）中与成熟体型相关的遗传相关形成机制。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（life table）评估相关响应。成年后期体型、繁殖产出以及成体生长速率在高性频率种群中均呈现出更为显著的响应，新生幼体体型与内禀增长率（r）也呈现出相似的变化模式。该变化模式仅在两种条件下成立：一是性状间的相关关系受到选择的青睐，二是性频率能够促进高适合度克隆（clone）的产生与种群数量扩张。幼体生长速率与成熟年龄则未呈现出一致的分化趋势。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水平。本研究数据支持‘相关选择是遗传相关形成的最主要驱动因素’这一假说，同时表明，在兼具有性与无性生殖的生物类群中，重组（recombination）可提升其适应性演化效率。