Data from: Multiple sexual selection pressures drive the rapid evolution of complex morphology in a male secondary genital structure

The genitalia of internally fertilizing taxa represent a striking example of rapid morphological evolution. Although sexual selection can shape variation in genital morphology, it has been difficult to test whether multiple sexual selection pressures combine to drive the rapid evolution of individual genital structures. Here, we test the hypothesis that both pre- and postcopulatory sexual selection can act in concert to shape complex structural variation in secondary genital morphology. We genetically modified the size and shape of the posterior lobes of Drosophila melanogaster males and tested the consequences of morphological variation on several reproductive measures. We found that the posterior lobes are necessary for genital coupling and that they are also the targets of multiple postcopulatory processes that shape quantitative variation in morphology, even though these structures make no direct contact with the external female genitalia or internal reproductive organs during mating. We also found that males with smaller and less structurally complex posterior lobes suffer substantial fitness costs in competitive fertilization experiments. Our results show that sexual selection mechanisms can combine to shape the morphology of a single genital structure and that the posterior lobes of D. melanogaster are the targets of multiple postcopulatory selection pressures.体内受精类群的生殖器，堪称形态快速演化的典型范例。尽管性选择能够塑造生殖器形态的变异，但验证多重性选择压力是否共同推动单个生殖结构的快速演化，始终颇具挑战。本研究针对"交配前与交配后性选择可协同作用，塑造次生生殖形态的复杂结构变异"这一假说展开验证。我们对黑腹果蝇（Drosophila melanogaster）雄性的后叶（posterior lobes）的大小与形态进行了基因改造，并检测该形态变异对多项生殖指标的影响。研究发现，后叶对于生殖器官接合至关重要；即便该结构在交配过程中，并未与雌性外生殖器或体内生殖器官发生直接接触，它们仍是多重交配后过程的作用靶点，这些过程会塑造形态的数量变异。我们还发现，在竞争性受精实验中，后叶体积更小、结构复杂度更低的雄性，其适合度会承受显著代价。本研究结果表明，多种性选择机制可共同塑造单个生殖结构的形态，而黑腹果蝇的后叶正是多重交配后选择压力的作用靶点。