Hooper Rebecca, Maher Kathryn, Moore Karen, McIvor Guillam, Hosken David, Thornton Alex
Centre for Research in Animal Behaviour, University of Exeter, Exeter, UK.
NERC Environmental Omics Facility, School of Biosciences, The University of Sheffield, Sheffield, UK.
R Soc Open Sci. 2024 Mar 27;11(3):231226. doi: 10.1098/rsos.231226. eCollection 2024 Mar.
Forced copulation is common, presumably because it can increase male reproductive success. Forced extra-pair copulation (FEPC) occurs in birds, even though most species lack a penis and are widely thought to require female cooperation for fertilization. How FEPC persists, despite a presumed lack of siring success and likely non-negligible costs to the male, is unknown. Using the jackdaw () as a case study, we use SNPs to quantify the extra-pair paternity rate through FEPC and evaluate explanations for the persistence of FEPC in species without a penis. We then collate evidence for FEPC across penis-lacking birds. Combining genetic and behavioural analyses, our study suggests that the most likely explanations for the maintenance of FEPC in jackdaws are that it provides a selective advantage to males or it is a relic. Our literature review shows that across birds lacking a penis, FEPC is taxonomically widespread, and yet, little is known about its evolution. A broader implementation of the approach used here, combining both genetic and behavioural data, may shed light on why this widespread sexual behaviour persists. Additional work is necessary to understand whether a penis is needed for paternity through forced copulation and to quantify the costs of FEPC.
强迫交配很常见，大概是因为它能提高雄性的繁殖成功率。强迫配偶外交配（FEPC）在鸟类中存在，尽管大多数鸟类没有阴茎，且普遍认为受精需要雌性的配合。尽管强迫配偶外交配可能无法成功授精，且对雄性来说成本可能不可忽视，但它为何持续存在仍是未知数。以寒鸦（ ）为例，我们使用单核苷酸多态性（SNP）来量化通过强迫配偶外交配产生的配偶外父权率，并评估在没有阴茎的物种中强迫配偶外交配持续存在的原因。然后，我们整理了缺乏阴茎的鸟类中强迫配偶外交配的证据。综合遗传和行为分析，我们的研究表明，寒鸦中强迫配偶外交配持续存在的最可能原因是它为雄性提供了选择优势，或者它是一种遗留现象。我们的文献综述表明，在缺乏阴茎的鸟类中，强迫配偶外交配在分类学上广泛存在，然而，对其进化却知之甚少。更广泛地应用这里所采用的结合遗传和行为数据的方法，可能会揭示这种广泛存在的性行为为何持续存在。还需要进一步的研究来了解通过强迫交配获得父权是否需要阴茎，并量化强迫配偶外交配的成本。
