Data from: Ontogenetic stage-specific quantitative trait loci contribute to divergence in developmental trajectories of sexually dimorphic fins between medaka populations

Sexual dimorphism can evolve when males and females differ in phenotypic optima. Genetic constraints can, however, limit the evolution of sexual dimorphism. One possible constraint is derived from alleles expressed in both sexes. Because males and females share most of their genome, shared alleles with different fitness effects between sexes are faced with intralocus sexual conflict. Another potential constraint is derived from genetic correlations between developmental stages. Sexually dimorphic traits are often favoured at adult stages, but selected against as juvenile, so developmental decoupling of traits between ontogenetic stages may be necessary for the evolution of sexual dimorphism in adults. Resolving intralocus conflicts between sexes and ages is therefore a key to the evolution of age-specific expression of sexual dimorphism. We investigated the genetic architecture of divergence in the ontogeny of sexual dimorphism between two populations of the Japanese medaka (Oryzias latipes) that differ in the magnitude of dimorphism in anal and dorsal fin length. Quantitative trait loci (QTL) mapping revealed that few QTL had consistent effects throughout ontogenetic stages and the majority of QTL change the sizes and directions of effects on fin growth rates during ontogeny. We also found that most QTL were sex-specific, suggesting that intralocus sexual conflict is almost resolved. Our results indicate that sex- and age-specific QTL enable the populations to achieve optimal developmental trajectories of sexually dimorphic traits in response to complex natural and sexual selection.

当雄性与雌性的表型最适值存在差异时，性别二态性（sexual dimorphism）可发生演化。然而，遗传限制（genetic constraints）会限制性别二态性的演化。其中一种潜在限制源自于在两性中均表达的等位基因。由于雌雄个体共享大部分基因组，在两性间适合度效应存在差异的共享等位基因会面临座位内性别冲突（intralocus sexual conflict）。另一种潜在限制则源自发育阶段间的遗传相关（genetic correlations）。通常在成虫阶段，性别二态性性状会受到选择青睐，但在幼体阶段却会被选择抑制，因此，若要实现成虫性别二态性的演化，可能需要实现不同个体发育阶段间性状的发育解耦。因此，解决两性及不同年龄间的座位内性别冲突，是实现性别二态性年龄特异性表达演化的关键。我们针对两个日本青鳉（Oryzias latipes）种群开展了研究，这两个种群在臀鳍与背鳍长度的性别二态性程度上存在差异，我们解析了其性别二态性个体发育分化的遗传结构（genetic architecture）。数量性状位点（quantitative trait loci，QTL）定位结果显示，几乎没有QTL在整个个体发育阶段中均能产生稳定的效应，绝大多数QTL会在个体发育过程中改变其对鳍生长速率的效应大小与方向。我们还发现，大部分QTL均为性别特异性，这表明座位内性别冲突已基本得到解决。我们的研究结果表明，具备性别与年龄特异性的QTL能够帮助种群响应复杂的自然选择与性选择，实现性别二态性性状的最优发育轨迹。