Banded mongooses avoid inbreeding when mating with members of the same natal group

Inbreeding and inbreeding avoidance are key factors in the evolution of animal societies, influencing dispersal and reproductive strategies which can affect relatedness structure and helping behaviours. In cooperative breeding systems, individuals typically avoid inbreeding through reproductive restraint and/or dispersing to breed outside their natal group. However, where groups contain multiple potential mates of varying relatedness, strategies of kin recognition and mate choice may be favoured. Here, we investigate male mate choice and female control of paternity in the banded mongoose (Mungos mungo), a cooperatively breeding mammal where both sexes are often philopatric and mating between relatives is known to occur. We find evidence suggestive of inbreeding depression in banded mongooses, indicating a benefit to avoiding breeding with relatives. Successfully breeding pairs were less related than expected under random mating, which appeared to be driven by both male choice and female control of paternity. Male banded mongooses actively guard females to gain access to mating opportunities, and this guarding behaviour is preferentially directed towards less closely related females. Guard–female relatedness did not affect the guard's probability of gaining reproductive success. However, where mate-guards are unsuccessful, they lose paternity to males that are less related to the females than themselves. Together, our results suggest that both sexes of banded mongoose use kin discrimination to avoid inbreeding. Although this strategy appears to be rare among cooperative breeders, it may be more prominent in species where relatedness to potential mates is variable, and/or where opportunities for dispersal and mating outside of the group are limited.

近交与近交回避是动物社群演化的关键因素，可通过影响扩散与繁殖策略，进而改变种群的亲缘结构与互助行为模式。在合作繁殖体系中，个体通常通过繁殖抑制或扩散至出生地群体外进行繁殖，以此规避近交风险。然而，当群体内存在多只亲缘关系各异的潜在配偶时，亲缘识别与配偶选择策略往往会受到自然选择的青睐。本研究以缟獴（Mungos mungo）为研究对象，该物种为合作繁殖的哺乳动物，雌雄两性均常表现出恋巢性，且已有记录显示其存在近亲交配现象。我们在缟獴种群中发现了近交衰退的相关证据，表明规避近亲交配具有演化收益。成功配对的繁殖个体间的亲缘关系程度低于随机交配下的预期值，这一现象似乎由雄性配偶选择与雌性父权控制共同驱动。雄性缟獴会主动守卫雌性以获得交配机会，且该守卫行为更倾向于指向亲缘关系更远的雌性。守卫者与雌性的亲缘关系并未影响其获得繁殖成功的概率，但当配偶守卫者未能成功交配时，其繁殖父权会被与雌性亲缘关系较自身与雌性亲缘关系更远的雄性所取代。综合来看，我们的研究结果表明，缟獴的雌雄两性均会通过亲缘识别来规避近交。尽管该策略在合作繁殖物种中较为罕见，但在潜在配偶亲缘关系存在差异、且/或群体外扩散与交配机会受限的物种中，该策略可能更为普遍。