Mating with multiple partners is common across animal taxa. Males mate multiply because reproductive success positively correlates with mating success. In contrast, multiple mating is expected to increase the direct (material) or indirect (genetic) benefits accrued by females but not necessarily increase their reproductive success. Cases in which female reproductive success increases with mating success could be due to females acquiring material resources that directly increase reproductive output. Because multiple mating likely increases reproductive success more in males than in females, males typically experience greater sexual selection. Consequently, males in harem polygynous species, where a few males can monopolize access to several females in a population, are expected to be under stronger sexual selection than females. We field-test these predictions by using the harem polygynous Wellington tree wētā, Hemideina crassidens. Here, we develop microsatellite markers for H. crassidens and use them to genotype females, their offspring and putative sires to estimate the opportunity for selection as well as quantify natural rates of multiple mating and its effect on male and female reproductive success (number of hatchlings). We found that both sexes mate multiply and that reproductive success increases with mating success in both sexes. Males and females have similar total opportunities for selection, and sexual selection comprises approximately 50% of the total selection operating in males. We found that female oviposition rate increases with mating success, but we found no evidence to support the hypothesis that females derive indirect benefits from polyandry. Our study provides strong evidence that male and female H. crassidens derive significant direct fitness benefits from multiple mating under natural conditions.

中文翻译：

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性二态性多雌性昆虫多次交配的好处

与多个伙伴交配在动物分类群中很常见。雄性交配成倍增加，因为繁殖成功与交配成功呈正相关。相比之下，预计多次交配会增加雌性产生的直接（物质）或间接（遗传）益处，但不一定会增加其繁殖成功率。雌性繁殖成功率随着交配成功而增加的情况可能是由于雌性获得了直接增加繁殖产量的物质资源。由于多次交配可能比雌性更能提高雄性的繁殖成功率，因此雄性通常会经历更多的性选择。因此，后宫一夫多妻物种中的雄性，在这种情况下，少数雄性可以垄断种群中的几个雌性，预计比雌性面临更强的性选择。我们通过使用后宫一夫多妻惠灵顿树 wētā，Hemideina crassidens 对这些预测进行了现场测试。在这里，我们开发了 H. crassidens 的微卫星标记，并使用它们对雌性、它们的后代和推定的公牛进行基因分型，以估计选择的机会，并量化多次交配的自然率及其对雄性和雌性繁殖成功率的影响（孵化数量）。我们发现两性交配成倍增加，并且繁殖成功率随着两性交配成功而增加。男性和女性的总选择机会相似，性选择约占男性总选择的 50%。我们发现雌性产卵率随着交配成功而增加，但我们没有发现任何证据支持雌性从一妻多夫中间接获益的假设。