Data from: Postmating sexual selection and the enigmatic jawed genitalia of Callosobruchus subinnotatus

Insect genitalia exhibit rapid divergent evolution. Truly extraordinary structures have evolved in some groups, presumably as a result of post-mating sexual selection. To increase our understanding of this phenomenon, we studied the function of one such structure. The male genitalia of Callosobruchus subinnotatus (Coleoptera: Bruchinae) contain a pair of jaw-like structures with unknown function. Here, we used phenotypic engineering to ablate the teeth on these jaws. We then experimentally assessed the effects of ablation of the genital jaws on mating duration, ejaculate weight, male fertilization success and female fecundity, using a double-mating experimental design. We predicted that copulatory wounding in females should be positively related to male fertilization success. However, we found no significant correlation between genital tract scarring in females and male fertilization success. Male fertilization success was, however, positively related to the amount of ejaculate transferred by males and negatively related to female ejaculate dumping. Ablation of male genital jaws did not affect male relative fertilization success but resulted in a reduction in female egg production. Our results suggest that postmating sexual selection in males indeed favors these genital jaws, but not primarily through an elevated relative success in sperm competition but by increasing female egg production.昆虫生殖器呈现快速趋异进化态势。部分昆虫类群演化出了极为奇特的结构，这大概率是交配后性选择作用的结果。为加深对该现象的认知，我们针对这类结构中的一种的功能展开了研究。亚侧斑豆象（Callosobruchus subinnotatus，鞘翅目：豆象亚科）的雄性生殖器具有一对功能未知的颚状结构。本研究采用表型工程（phenotypic engineering）技术，切除了这些颚状结构上的齿突；随后通过双交配实验设计，评估了切除生殖颚对交配时长、射精物重量、雄性受精成功率以及雌性繁殖力（fecundity）的影响。我们曾预测雌性的交配创伤（copulatory wounding）程度与雄性受精成功率呈正相关，但并未发现雌性生殖道瘢痕与雄性受精成功率之间存在显著相关性。不过，雄性受精成功率与雄性转移的射精物总量呈正相关，且与雌性的射精物排出（ejaculate dumping）行为呈负相关。切除雄性生殖颚并未影响雄性的相对受精成功率，但却导致雌性产卵量下降。我们的研究结果表明，雄性的交配后性选择确实偏好这类生殖颚结构，但这一偏好并非主要通过提升精子竞争（sperm competition）中的相对成功率实现，而是通过提高雌性的产卵量达成。