Data from: Divergent artificial selection for female reproductive investment has a sexually concordant effect on male reproductive success

Depending on the genetic architecture of male and female fitness, sex-specific selection can have negative, positive or neutral consequences for the opposite sex. Theory predicts that conflict between male and female function may drive the breakdown of intrasexual genetic correlations, allowing sexual dimorphism in sexually antagonistic traits. Reproductive traits are the epitome of this, showing highly differentiated proximate functions between the sexes. Here we use divergent artificial selection lines for female reproductive investment to test how female-specific selection on a sex-limited trait affects male reproductive success in a precocial bird, the Japanese quail (Coturnix japonica). We demonstrate that selection for increased egg investment in females positively affects male reproductive success both in competitive and non-competitive mating situations. This increased reproductive success was linked to a relatively larger left testis in males originating from lines selected for high female reproductive investment. Given that female quail have functional gonads only on their left side, this correlated response indicates that selection has acted on the shared developmental basis of male and female gonads. Our study thereby provides evidence for a positive genetic correlation between key reproductive traits in males and females despite a high degree of sexual dimorphism, and suggests that, in this system, selection on reproductive function is sexually concordant.

根据雌雄适合度的遗传结构（genetic architecture），性别特异性选择（sex-specific selection）对异性的影响可呈负面、正向或中性效应。理论预测，雌雄生殖功能间的冲突可能会打破性内遗传相关性（intrasexual genetic correlations），进而推动性拮抗性状（sexually antagonistic traits）演化出两性异形（sexual dimorphism）。生殖性状正是这一演化现象的典型缩影，其在两性间展现出高度分化的近缘功能。
本研究以早成鸟（precocial bird）日本鹌鹑（Coturnix japonica）为实验材料，利用针对雌性生殖投入的差异化人工选择品系（artificial selection lines），探究限性性状（sex-limited trait）上的雌性特异性选择如何影响雄性生殖成功率（male reproductive success）。实验结果表明，在竞争性交配情境（competitive mating situations）与非竞争性交配情境（non-competitive mating situations）下，针对雌性生殖投入提升的选择均对雄性生殖成功率产生了正向影响。这一生殖成功率的提升，与来自高雌性生殖投入选择品系的雄性个体拥有相对更大的左侧睾丸（left testis）密切相关。
鉴于雌性鹌鹑仅左侧性腺（gonads）具有功能，这一相关响应（correlated response）表明选择作用于雌雄两性性腺的共同发育基础（shared developmental basis）。综上，本研究提供了确凿证据表明，尽管两性间存在高度的两性异形，雌雄关键生殖性状间仍存在正向遗传相关性（genetic correlation），并表明在该体系中，针对生殖功能的选择呈性别协同（sexually concordant）效应。