Data from: Multi-generational response to artificial selection for biased clutch sex ratios in Tigriopus californicus populations

Polygenic sex determination (PSD) is relatively rare and theoretically evolutionary unstable, yet has been reported across a range of taxa. Evidence for multilocus PSD is provided by (i) large between-family variance in sex ratio, (ii) paternal and maternal effects on family sex ratio and (iii) response to selection for family sex ratio. This study tests the polygenic hypothesis of sex determination in the harpacticoid copepod Tigriopus californicus using the criterion of response to selection. We report the first multigenerational quantitative evidence that clutch sex ratio responds to artificial selection in both directions (selection for male- and female-biased families) and in multiple populations of T. californicus. In the five of six lines that showed a response to selection, realized heritability estimated by multigenerational analysis ranged from 0.24 to 0.58. Divergence of clutch sex ratio between selection lines is rapid, with response to selection detectable within the first four generations of selection.

多基因性别决定（Polygenic Sex Determination, PSD）较为罕见，且理论上具有进化不稳定性，但目前已在多个生物类群中被报道。多基因性别决定的多位点证据包括：（i）家系间性比方差较大；（ii）父本与母本对家系性比存在显著效应；（iii）家系性比可对选择产生响应。本研究以对选择的响应为判定标准，在猛水蚤目桡足类动物加州虎斑猛水蚤（Tigriopus californicus）中检验了性别决定的多基因假说。我们首次提供了多代定量研究证据，表明加州虎斑猛水蚤的多个种群中，每窝幼体性比可在两个方向（即人工选择偏向雄性家系与偏向雌性家系）上响应人工选择。在6个选择系中，有5个出现了选择响应，经多代分析估算的实现遗传力范围为0.24至0.58。不同选择系间的每窝幼体性比分化速度较快，在选择开始后的前4代即可检测到对选择的响应。