The decision to cooperate: kin recognition mechanisms in female house mice

这个项目解决了亲缘关系识别的潜在机制，以及亲缘关系在雌性之间合作繁殖中的重要性。当动物帮助饲养非自己的后代时，合作繁殖就发生了。例如，雌性家鼠经常与另一只繁殖的雌性家鼠共同饲养它们的后代，为共同巢中的所有幼崽提供牛奶。这一决定是临时的--他们可以选择与特定的合作伙伴合作或不合作。然而，社会伴侣选择背后的因素，以及这种选择如何影响个体雌性对自己和其他幼崽的投资，人们知之甚少。人们通常认为，亲属关系通过增加拥有相同基因的亲属的成功来驱动这种合作行为。隐含地，这需要可靠地识别亲缘关系和非亲缘关系个体混合的物种中的近亲，尽管我们对动物识别亲缘关系的能力以及可能支撑这一能力的机制的了解令人惊讶地贫乏。最近，我们发现了一种高度多态的遗传身份信号，用于避免与近亲小鼠进行近亲繁殖。这为基因识别机制提供了明确的证据，该机制用于识别共享相同高度多态遗传标记的近亲。我们将使用这一已被证实的遗传标记来测试雌性家鼠是否更喜欢已知的亲戚作为合作伙伴。我们还将使用一种新的非侵入性方法来标记单个母亲的乳汁，并首次测量在公共巢穴中每只幼崽的投资。这将使我们能够解决那些与已知亲属合作的人是否比那些与其他女性合作的人在自己和其他子女身上表现出更平等的投资。然而，这种简单的遗传亲属识别机制是有限的，因为它只能识别一小部分近亲。通过建模，我们已经生成了关于同胞和无关动物的比例的可测试预测，这些比例将使用替代的遗传亲属识别机制进行识别。从理论上讲，在养育过程中通过母亲的表型检测到的母亲等位基因上的行为印记可以可靠地识别出非常高比例的近亲。然而，使用这一机制识别亲属的关键要求还有待测试。在这个项目中，我们将确定正常的、遗传可变的家鼠是否可以通过在母系等位基因上的行为印记来识别母系亲属。我们将确定它们是在三个高度多态的基因簇上特异地印记，这些基因簇编码了老鼠气味中已建立的遗传身份信号，还是在其他遗传位点上。我们还将测试共同的母体环境是否有助于识别母系同胞和同父异母的同胞，这会影响近亲基因纯合实验室小鼠的气味。我们的发现将对理解动物在广泛的社会背景下能够识别近亲的程度具有普遍的相关性。亲属关系不太可能是影响繁殖雌性之间合作决定的唯一因素。小鼠可以通过犁鼻嗅子系统检测到的尿蛋白和代谢物(类固醇硫酸盐)获得大量关于雌性生理状态的信息。我们将测试不是由亲属关系决定的个人伴侣偏好是否与这些生理变量气味成分的表达相关。我们还将测试雌性是否会避免近亲交配的伴侣(来自同胞交配)，因为近亲交配在抚养后代到断奶方面的成功率会显著降低。

This project addresses mechanisms underlying kin recognition, and the importance of kinship in cooperative breeding between females. Cooperative breeding occurs when animals assist in rearing offspring that are not their own. For example, female house mice frequently rear their offspring communally with another breeding female, providing milk to all pups in the communal nest. This decision is facultative - they can choose to cooperate with a particular partner or not. However, the factors that underlie social partner choice, and how this choice influences an individual female's investment in own and other pups, are poorly understood. It is generally assumed that kinship drives such cooperative behaviour by increasing the success of relatives that share genes. Implicitly, this requires reliable recognition of close kin in species where related and unrelated individuals mix, although we have surprisingly poor understanding of the abilities of animals to recognize kin and the mechanisms that might underlie this. Recently, we discovered a highly polymorphic genetic identity signal that is used to avoid inbreeding with close kin by house mice. This has provided clear evidence of a genetic recognition mechanism that is used to identify close kin sharing the same highly polymorphic genetic marker. We will use this proven genetic marker to test whether female house mice prefer known kin as cooperative partners. We will also use a novel non-invasive approach to label the milk of individual mothers and measure investment in each pup in communal nests for the first time. This will allow us to address whether those cooperating with known kin show more egalitarian investment in their own and other offspring than those cooperating with other females. This type of simple genetic kin recognition mechanism is limited, though, because it identifies only a small proportion of close kin. Through modeling, we have generated testable predictions concerning the proportion of sibs and unrelated animals that would be recognized using alternative genetic kin recognition mechanisms. Theoretically, behavioural imprinting on maternal alleles detected through a mother's phenotype during rearing could allow reliable recognition of a very high proportion of close kin. However, the key requirements for recognition of kin using this mechanism have yet to be tested. In this project, we will establish whether normal, genetically variable house mice can recognize maternal kin through behavioural imprinting on maternal alleles. We will determine whether they imprint specifically on three highly polymorphic gene clusters that encode established genetic identity signals in mouse scents, or on other genetic loci. We will also test whether a common maternal environment, which influences the scents of inbred genetically homozygous laboratory mice, contributes to any recognition of maternal sibs and half-sibs. Our findings will have general relevance for understanding the extent to which animals are able to recognize close kin in a broad range of social contexts. Kinship is unlikely to be the only factor influencing the decision to cooperate among breeding females. Mice can gain considerable information about female physiological status through urinary proteins and metabolites (steroid sulphates) detected through the vomeronasal olfactory subsystem. We will test whether individual partner preferences that are not determined by kinship correlate with expression of these physiologically-variable scent components. We will also test whether females avoid inbred partners (from sib matings) that would have significantly poorer success in raising offspring to weaning.