Department of Biology, University of Oklahoma, Norman, Oklahoma.
Evolution. 2021 May;75(5):989-1002. doi: 10.1111/evo.14169. Epub 2021 Jan 18.
Rapid divergence in genital structures among nascent species has been posited to be an early-evolving cause of reproductive isolation, although evidence supporting this idea as a widespread phenomenon remains mixed. Using a collection of interspecific introgression lines between two Drosophila species that diverged approximately 240,000 years ago, we tested the hypothesis that even modest divergence in genital morphology can result in substantial fitness losses. We studied the reproductive consequences of variation in the male epandrial posterior lobes between Drosophila mauritiana and Drosophila sechellia and found that divergence in posterior lobe morphology has significant fitness costs on several prefertilization and postcopulatory reproductive measures. Males with divergent posterior lobe morphology also significantly reduced the life span of their mates. Interestingly, one of the consequences of genital divergence was decreased oviposition and fertilization, which suggests that a sensory bias for posterior lobe morphology could exist in females, and thus, posterior lobe morphology may be the target of cryptic female choice in these species. Our results provide evidence that divergence in genitalia can in fact give rise to substantial reproductive isolation early during species divergence, and they also reveal novel reproductive functions of the external male genitalia in Drosophila.
新生物种之间生殖器结构的快速分化被认为是生殖隔离的早期进化原因，尽管支持这一观点作为一种普遍现象的证据仍然存在分歧。利用大约 24 万年前分化的两个果蝇物种之间的种间渗入系的集合，我们检验了这样一个假设，即即使是生殖器形态的适度分化也会导致显著的适应度损失。我们研究了雄性 epandrial 后叶在果蝇和果蝇之间的变化对几种受精前和后交配生殖措施的影响，发现后叶形态的分化对几个预受精和后交配生殖措施有显著的适应度代价。具有不同后叶形态的雄性也显著降低了其配偶的寿命。有趣的是，生殖器分化的一个后果是产卵和受精减少，这表明雌性可能对后叶形态存在感觉偏差，因此，后叶形态可能是这些物种中隐性雌性选择的目标。我们的结果提供了证据，表明生殖器的分化实际上可以在物种分化的早期导致显著的生殖隔离，并且它们还揭示了果蝇外部雄性生殖器的新的生殖功能。
