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.

基于雌雄适合度（fitness）的遗传结构（genetic architecture），性别特异性选择（sex-specific selection）对异性可能产生负面、正面或中性的影响。理论预测，雌雄生殖功能间的冲突可能驱动种内遗传相关性（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（reproductive traits）正是这一现象的典型缩影，其在两性间展现出高度分化的近缘功能（proximate functions）。
本研究以雌性生殖投入（female reproductive investment）为目标构建分歧人工选择品系（divergent artificial selection lines），以此探究限性性状（sex-limited trait）上的雌性特异性选择如何影响早成鸟（precocial bird）——日本鹌鹑（Coturnix japonica）的雄性生殖成功率（male reproductive success）。研究证实，对雌性提升产卵投入的选择，无论在竞争性还是非竞争性交配情境下，均能正向提升雄性生殖成功率。这种生殖成功率的提升，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）存在关联。
鉴于雌性鹌鹑仅左侧性腺（gonads）具备功能，这种相关响应表明，选择作用于雌雄两性性腺共有的发育基础。因此，本研究提供了证据：尽管存在高度的性二态性，雌雄两性的关键生殖性状之间仍存在正向遗传相关性（genetic correlation），并提示在该物种系统中，生殖功能所受的选择属于性协同选择（sexual concordant）。