The effect of variable frequency of sexual reproduction on the genetic structure of natural populations of a cyclical parthenogen

Cyclical parthenogens are a valuable system in which to empirically test theoretical predictions as to the genetic consequences of sexual reproduction in natural populations, particularly if the frequency of sexual relative to asexual reproduction can be quantified. In this study we utilized a series of lake populations of the cyclical parthenogen, Daphnia pulicaria, that vary consistently in their investment in sexual reproduction, to address the questions of whether the ecological variation in investment in sex is detectable at the genetic level, and if so, whether the genetic patterns seen are consistent with theoretical predictions. We show that there is variation in the genetic structure of these populations in a manner consistent with their investment in sexual reproduction. Populations engaging in a high frequency of sex were in Hardy-Weinberg and gametic phase equilibrium, and showed little genotypic differentiation across sampled years. In contrast, populations with a lower frequency of sex deviated widely from equilibrium, had reduced multi-locus clonal diversity, and showed significant temporal genotypic deviation.

周期性孤雌生殖生物（cyclical parthenogens）是一类极具科研价值的研究系统，可用于实证检验自然种群有性生殖遗传后果的相关理论预测，尤其当可量化有性生殖相较于无性生殖的发生频率时，更能发挥其研究价值。本研究选取了一系列蚤状溞（Daphnia pulicaria）的湖泊种群作为实验材料，这类周期性孤雌生殖生物在有性生殖投入上存在稳定的差异。我们旨在解答两个核心科学问题：其一，有性生殖投入的生态差异能否在遗传水平上被检测到？其二，若该差异可被检测，观测到的遗传模式是否与理论预测相符？研究结果显示，这些种群的遗传结构存在变异，且该变异与其有性生殖投入水平相一致：高有性生殖频率的种群处于哈迪-温伯格平衡（Hardy-Weinberg equilibrium）与配子相平衡（gametic phase equilibrium）状态，且在不同采样年份间几乎未出现基因型分化。与之形成鲜明对比的是，低有性生殖频率的种群则显著偏离遗传平衡，其多位点克隆多样性（multi-locus clonal diversity）有所降低，且在不同采样年份间呈现出显著的基因型偏离。