Inclusive fitness benefits mitigate costs of cuckoldry to socially paired males

Background: In socially monogamous species, reproduction is not always confined to paired males and females. Extra-pair males commonly also reproduce with paired females, which is traditionally thought to be costly to the females’ social partners. However, we suggest that when the relatedness between reproducing individuals is considered, cuckolded males can suffer lower fitness losses than otherwise expected, especially when the rate of cuckoldry is high. We combine theoretical modeling with a detailed genetic study on a socially monogamous wild fish, Variabilichromis moorii, which displays biparental care despite exceptionally high rates of extra-pair paternity. Results: We measured the relatedness between all parties involved in V. moorii spawning events (i.e. between males and females in social pairs, females and their extra-pair partners, and paired males and their cuckolders), and we reveal that males are on average more related to their cuckolders than expected by chance. Quel...研究背景：在社会单配制物种（socially monogamous species）中，繁殖并非仅局限于配对的雌雄个体。婚外配雄性（extra-pair males）通常可与配对雌性发生繁殖行为，传统观点认为此举会对雌性的社会配偶造成适合度代价。但我们提出，若考虑繁殖个体间的亲缘关系，遭遇婚外配的雄性（cuckolded males）所承受的适合度损失或低于预期，尤其当婚外配发生率较高时。我们结合理论建模与针对野生鱼类穆尔七彩丽鲷（Variabilichromis moorii）的详细遗传学研究，该物种尽管婚外父权（extra-pair paternity）发生率极高，但仍存在双亲抚育（biparental care）行为。 研究结果：我们测定了穆尔七彩丽鲷产卵事件中所有参与方的亲缘关系，具体包括社会配对的雌雄个体间、雌性与其婚外配配偶间，以及配对雄性与其插足雄性间的亲缘关系，并发现雄性平均而言比随机概率下更亲近其插足的婚外配者。Quel...