Orr Teri J, Lukitsch Theresa, Eiting Thomas P, Brennan Patricia L R
New Mexico State University, Department of Biology, Las Cruces, NM 88003.
Department of Neurobiology, University of Utah, Salt Lake City, UT 84112.
Integr Comp Biol. 2022 Jun 6. doi: 10.1093/icb/icac040.
The lower reproductive tract of female mammals has several competing functions including mating, tract health maintenance, and parturition. Diverse vaginal anatomy suggests interactions between natural and sexual selection, yet despite its importance, female copulatory morphology remains under-studied. We undertook a comparative study across the species-rich mammalian order Chiroptera (bats) with a focus on the suborder Yangochiroptera (Vespertilioniformes) to examine how female vaginal features may have coevolved with male penis morphology to minimize mechanical damage to their tissues during copulation. The penis morphology is diverse, presenting great potential for post-copulatory sexual selection and coevolution with the female morphology, but vaginas have not been carefully examined. Here we test the hypotheses that vaginal thickness and collagen density have coevolved with features of the male penis including the presence of spines and a baculum. We present histological data from females of 24 species from 7 families of bats, and corresponding data on male penis anatomy. We also examine the role of phylogenetic history in the morphological patterns we observe. We found evidence that female vaginal thickness has coevolved with the presence of penile spines, but not with baculum presence or width. Collagen density did not appear to covary with male penile features. Our findings highlight the importance of considering interactions between the sexes in influencing functional reproductive structures and examine how these structures have been under selection in bats.
雌性哺乳动物的下生殖道具有多种相互竞争的功能，包括交配、生殖道健康维持和分娩。多样的阴道解剖结构表明自然选择和性选择之间存在相互作用，然而，尽管其重要性，雌性交配形态仍未得到充分研究。我们对物种丰富的翼手目（蝙蝠）进行了一项比较研究，重点关注小蝙蝠亚目（ Vespertilioniformes），以研究雌性阴道特征如何与雄性阴茎形态共同进化，从而在交配过程中尽量减少对其组织的机械损伤。阴茎形态多样，为交配后的性选择以及与雌性形态的共同进化提供了巨大潜力，但阴道尚未得到仔细研究。在这里，我们检验以下假设：阴道厚度和胶原蛋白密度与雄性阴茎的特征共同进化，包括棘刺的存在和阴茎骨。我们展示了来自7个蝙蝠科24个物种雌性的组织学数据，以及关于雄性阴茎解剖结构的相应数据。我们还研究了系统发育历史在我们观察到的形态模式中的作用。我们发现证据表明，雌性阴道厚度与阴茎棘刺的存在共同进化，但与阴茎骨的存在或宽度无关。胶原蛋白密度似乎与雄性阴茎特征没有相关性。我们的研究结果强调了在影响功能性生殖结构方面考虑两性之间相互作用的重要性，并研究了这些结构在蝙蝠中是如何受到选择的。
