The mechanisms underlying polyandry and female mate choice in certain taxonomic groups remain widely debated. In elasmobranchs, several species have shown varying rates of polyandry based on genetic studies of multiple paternity (MP). We investigated MP in the finetooth shark, Carcharhinus isodon, in order to directly test the encounter rate hypothesis (ERH), which predicts that MP is a result of the frequency of encounters between mature conspecifics during the breeding season, and should therefore increase when more time is available for copulation and sperm storage. Female finetooth sharks in the northern Gulf of Mexico (GoM) have been found to reproduce with both annual periodicity and biennial periodicity, while finetooth sharks from the northwestern Atlantic Ocean have only been found to reproduce biennially, allowing us to compare mating opportunity to frequency of MP. Our results show high rates of MP with no significant difference in frequency between females in the GoM (83.0%) and Atlantic (88.2%, p = .8718) and varying but nonsignificant rates of MP between females in the GoM reproducing annually (93.0%) and biennially (76.6%, p = .2760). While the ERH is not supported by this study, it remains possible that reproductive periodicity and other physiological factors play a role in determining rates of MP in elasmobranchs, with potential benefits to individuals and populations.

中文翻译：

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具有不同繁殖周期的两个细齿鲨（Carcharhinus isodon）种群的多重父系关系

某些分类群中一妻多夫和雌性配偶选择的潜在机制仍然存在广泛争议。在 elasmobranchs 中，基于多父系 (MP) 的遗传研究，几个物种显示出不同的一妻多夫率。我们研究了细齿鲨Carcharhinus isodon 中的MP，为了直接测试相遇率假设（ERH），该假设预测 MP 是繁殖季节成熟同种之间相遇频率的结果，因此当有更多时间可用于交配和精子储存时，MP 应该增加。墨西哥湾北部 (GoM) 的雌性细齿鲨被发现以一年一次和两年一次的周期繁殖，而来自大西洋西北部的细齿鲨只被发现每两年一次繁殖，这使我们能够比较交配机会与频率议员。我们的结果显示，在 GoM (83.0%) 和大西洋 (88.2%, p = .8718) 以及每年 (93.0%) 和每两年 (76.6%, p  = .2760)的 GoM 雌性之间 MP 的变化但不显着的比率。虽然本研究不支持 ERH，但生殖周期和其他生理因素仍有可能在确定弹性鳃中的 MP 率方面发挥作用，对个人和人群具有潜在益处。