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）可对异性产生负面、正面或中性的影响。理论预测，雌雄生殖功能间的冲突可能引发同性遗传相关性（intrasexual genetic correlations）的瓦解，使得性拮抗性状（sexually antagonistic traits）出现性二态性（sexual dimorphism）。生殖性状正是这一现象的典型代表，其在两性间的近端功能（proximate functions）存在显著分化。本研究以早成鸟（precocial bird）日本鹌鹑（Japanese quail, Coturnix japonica）为研究对象，通过针对雌性生殖投入（female reproductive investment）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）。研究结果表明，针对雌性提升产卵投入的选择，无论在交配竞争还是非竞争情境下，均能正向影响雄性的生殖成功率。这种生殖成功率的提升，与源自高雌性生殖投入选择品系的雄性个体的左侧睾丸相对更大存在关联。鉴于雌性鹌鹑仅左侧性腺（gonads）具备功能，这一相关响应表明，选择作用于雌雄两性性腺的共同发育基础。综上，本研究证实，尽管两性间存在高度的性二态性，但雌雄核心生殖性状间仍存在正向遗传相关性，同时表明在该研究体系中，针对生殖功能的选择是性别协同的（sexually concordant）。