Data from: Sexual selection shapes development and maturation rates in Drosophila

Explanations for the evolution of delayed maturity usually invoke trade-offs mediated by growth, but processes of reproductive maturation often continue long after growth has ceased. Here, we tested whether sexual selection shapes the rate of post-eclosion maturation in the fruit fly Drosophila melanogaster. We found that populations maintained for more than 100 generations under a short generation time and polygamous mating system evolved faster post-eclosion maturation and faster egg-to-adult development of males, when compared to populations kept under short generations and randomized monogamy that eliminated sexual selection. An independent assay demonstrated that more mature males have higher fitness under polygamy, but this advantage disappears under monogamy. In contrast, for females greater maturity was equally advantageous under polygamy and monogamy. Furthermore, monogamous populations evolved faster development and maturation of females relative to polygamous populations, with no detectable trade-offs with adult size or egg-to-adult survival. These results suggest that a major aspect of male maturation involves developing traits that increase success in sexual competition, whereas female maturation is not limited by investment in traits involved in mate choice or defense against male antagonism. Moreover, rates of juvenile development and adult maturation can readily evolve in opposite directions in the two sexes, possibly implicating polymorphisms with sexually antagonistic pleiotropy.

关于延迟成熟的演化，既往研究通常援引生长介导的适应性权衡进行解释，但生殖成熟过程往往在个体生长停止后仍持续相当长时间。本研究以黑腹果蝇（Drosophila melanogaster）为实验材料，检验性选择（sexual selection）是否会调控其羽化后成熟（post-eclosion maturation）速率。我们发现，相较于在短世代且通过随机单配偶制消除性选择的种群，在短世代多配偶交配系统（polygamous mating system）下维持超过100代的果蝇种群，其雄性的羽化后成熟速率与卵至成虫发育速率均显著更快。独立测定结果显示，在多配偶交配条件下，成熟度更高的雄性具有更高的适合度（fitness），但该优势在单配偶制环境中完全消失。与之相反，雌性的更高成熟度在多配偶与单配偶两种条件下均能带来同等的适合度优势。此外，相较于多配偶种群，单配偶种群的雌性发育与成熟速率更快，且未检测到与成虫体型或卵至成虫存活率相关的适应性权衡。上述结果表明，雄性成熟的核心演化方向之一是发育出能够提升性竞争成功率的性状，而雌性成熟则未受限于为配偶选择或抵御雄性拮抗作用所投入的资源。进一步而言，幼体发育与成虫成熟的速率可在两性中朝相反方向快速演化，这一现象可能与携带性拮抗多效性（sexually antagonistic pleiotropy）的遗传多态性（polymorphisms）有关。