Causes, consequences and evolution of inbreeding tolerance and avoidance in a cooperative mammal

众所周知，近亲交配有时发生在野生种群中，这通常会产生适应成本，但近亲交配的影响可能比近亲交配衰退更严重。在最基本的层面上，近亲繁殖增加了群体成员之间的亲缘关系，这反过来可能会增加合作的好处。这一想法虽然有争议，但得到了相当大的理论支持。在合作繁殖物种中，近亲交配的个体可能与其他群体成员关系更密切，因此可能比近亲交配的个体更有可能帮助或接受帮助。因此，近亲交配可能会对社会群体中帮助行为的分布产生重要影响。此外，尽管近亲交配衰退的影响已经被大量研究，但近亲交配的潜在原因却知之甚少。例如，人们对可能导致饲养者之间高度关联的人口统计因素知之甚少。个体能够避免近亲交配的确切情况也尚不清楚。我们建议使用来自一种高度合作的哺乳动物--带状猫鼬--Mungos Mungo的长期研究的丰富的多世代数据来研究近亲交配的原因和后果。我们之前在这个系统上的工作揭示了近亲交配倾向和近亲交配实现水平在种内的相当大的差异，使其非常适合于研究近亲交配的自然历史。因此，我们将利用现有的在40个微卫星座位上进行基因分型的大约2000个个体的大型分子数据库来构建长达17代的系谱。这将被用来建立近亲交配和亲缘关系的水平，这反过来又将与近20年来连续收集的详细的基于个体的行为和表型数据相联系。这些丰富的谱系和生活史数据将被用来探索影响近亲交配行为的社会和遗传因素，确定雌性是否以及如何避免近亲交配，以及确定帮助行为是否可以减轻近亲交配抑制的成本。最后，我们将利用这个物种独特的“护送”系统，在这个系统中，每个后代都由一只成年幼崽保护、喂养和培育，以检验这样的假设，即帮助者优先照顾关系密切的近亲繁殖的幼崽。如果是这样的话，这将为我们关于近亲繁殖促进哺乳动物近亲选择的知识提供第一个经验性的证明。

It is well known that inbreeding sometimes occurs in wild populations, and that this usually incurs a fitness cost, but the impacts of inbreeding may go much further than inbreeding depression. At its most basic level, inbreeding increases relatedness between group members, which may in turn increase the benefits of cooperation. This idea, whilst controversial, has received considerable theoretical support. In cooperatively breeding species, inbred individuals may be more closely related to other group members and hence may be more likely to help, or to receive help, than their outbred counterparts. Consequently, inbreeding could have important impacts on the distribution of helping behavior within social groups. Furthermore, although the impacts of inbreeding depression have been much studied, the underlying causes of inbreeding are poorly understood. Little is known, for example, about the demographic factors that can lead to high levels of relatedness between breeders. The exact circumstances under which individuals are able to avoid inbreeding also remain unclear.We propose to investigate the causes and consequences of inbreeding using rich, multigenerational data from a long-term study of a highly cooperative mammal, the banded mongoose, Mungos mungo. Our previous work on this system has revealed considerable intraspecific variation in both the propensity to inbreed and the realised level of inbreeding, making it ideally suited to studying the natural history of inbreeding. Consequently, we will exploit a large existing molecular dataset of around 2000 individuals genotyped at 40 microsatellite loci to construct a pedigree up to 17 generations deep. This will be used to establish levels of inbreeding and relatedness, which in turn will be linked to detailed individual-based behavioural and phenotypic data collected continuously over almost two decades.This wealth of pedigree and life-history data will be used to explore the social and genetic factors that shape inbreeding behaviour, to establish if and how females avoid inbreeding, and to determine if whether helping behaviour can mitigate the costs of inbreeding depression. Finally, we will exploit the unique 'escorting' system of this species, in which each offspring is protected, fed and groomed by a single adult, to test the hypothesis that helpers preferentially direct care towards closely related, inbred pups. If so, this would provide the first empirical demonstration to our knowledge of inbreeding facilitating kin selection in a cooperatively breeding mammal.