Data from: High temperatures reveal cryptic genetic variation in a polymorphic female sperm storage organ

Variation in female reproductive morphology may play a decisive role in reproductive isolation by affecting the relative fertilization success of alternative male phenotypes. Yet, knowledge of how environmental variation may influence the development of the female reproductive tract and thus alter the arena of post-copulatory sexual selection is limited. Yellow dung fly females possess either three or four sperm storage compartments, a polymorphism with documented influence on sperm precedence. We performed a quantitative genetics study including 12 populations reared at three developmental temperatures complemented by extensive field data to show that warm developmental temperatures increase the frequency of females with four compartments, revealing striking hidden genetic variation for the polymorphism. Systematic genetic differentiation in growth rate and spermathecal number along latitude, and phenotypic covariance between the traits across temperature treatments suggest that the genetic architecture underlying the polymorphism is shaped by selection on metabolic rate. Our findings illustrate how temperature can modulate the preconditions for sexual selection by differentially exposing novel variation in reproductive morphology. This implies that environmental change may substantially alter the dynamics of sexual selection. We further discuss how temperature-dependent developmental plasticity may have contributed to observed rapid evolutionary transitions in spermathecal morphology.

雌性生殖形态的变异可通过影响不同雄性表型的相对受精成功率，在生殖隔离中发挥决定性作用。然而，目前学界对环境变异如何影响雌性生殖道发育、进而改变交配后性选择的作用场域的认知仍较为有限。黄粪蝇雌性具有3个或4个受精囊（sperm storage compartment），这一多态性已被证实会影响精子优先受精（sperm precedence）。本研究开展了一项数量遗传学研究，纳入在三种发育温度下饲养的12个种群，并辅以大量野外数据，结果证实较高的发育温度会提升拥有4个受精囊的雌性比例，揭示了该多态性背后此前未被发现的显著遗传变异。沿纬度梯度呈现的生长速率与受精囊数量的系统性遗传分化，以及不同温度处理下各性状间的表型协方差，均表明该多态性背后的遗传架构受代谢速率相关选择的塑造。本研究结果阐明了温度如何通过差异化暴露生殖形态的新变异，来调控性选择的前提条件。这意味着环境变化可能会大幅改变性选择的动态过程。我们还进一步讨论了温度依赖的发育可塑性，如何促成了此前观测到的受精囊形态的快速进化转变。