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（indirect selection）改变进化轨迹。多效性（pleiotropy）、随机连锁与选择均可导致遗传相关，但对表型进化的影响各不相同。本研究旨在探究周期性孤雌生殖生物普利卡溞（Daphnia pulicaria）中与成熟体大小相关的遗传相关形成机制。我们针对4个性别发生频率存在差异的种群，以体型大小为目标开展选择实验，并通过生命表（life table）分析评估相关响应。晚熟成体体型、繁殖输出与成体生长率在高性别发生频率种群中均呈现出更强的选择响应，幼体大小与内禀增长率（r）也呈现出相似的变化模式。这种变化模式仅在两种条件下成立：一是性状间的相关受到选择的青睐，二是性别发生频率有利于高适合度无性系的产生与种群扩张。幼体生长速率与成熟年龄则未出现一致的分化。产卵间隔似乎在低性别发生频率种群中响应更强，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，并表明在兼具有性与无性生殖的生物中，重组可提升其适应性。