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是形态快速演化的典型范例。尽管性选择可塑造生殖器形态的变异，但学界长期难以验证多重性选择压力是否会共同推动单个生殖器结构的快速演化。本研究验证了这一假说：交配前与交配后性选择可协同作用，塑造次生生殖器形态的复杂结构变异。我们对黑腹果蝇（Drosophila melanogaster）雄性的后叶大小与形态进行了遗传改造，并检测了形态变异对多项生殖指标的影响。研究发现，后叶是生殖器耦合的必要结构，同时也是多重交配后过程作用的靶点——这些过程会塑造形态的数量变异，尽管该结构在交配过程中并不会与雌性外生殖器或体内生殖器官发生直接接触。我们还发现，在竞争受精实验中，后叶更小且结构复杂度更低的雄性会承受显著的适合度代价。本研究结果表明，多种性选择机制可共同塑造单个生殖器结构的形态，且黑腹果蝇的后叶是多重交配后性选择压力的作用靶点。