Evolutionary genetics of social behaviour in birds

自从达尔文第一次认识到自然选择预示着自私而不是合作以来，合作行为的存在就给进化生物学家带来了一个重大问题。因此，群居昆虫(蚂蚁、蜜蜂和黄蜂)的复杂社会和许多脊椎动物的合作繁殖系统，在这种系统中，非繁殖助手帮助繁殖者抚养后代，一直是进化生物学家研究的主要重点。自达尔文以来，在我们对这种行为的理解上取得的最大进步是汉密尔顿在1964年引入了亲属选择(包容性适应度理论)的概念。关键的见解是，个人可以通过提高亲属的存活率或生产力以及通过个人繁殖来增加他们在进化上的适应性。然而，亲缘选择在脊椎动物合作繁育系统进化中的作用仍然是一个相当有争议的问题。这种理解差距背后的一个问题是，很难衡量通过个人繁殖直接获得的健康状况，以及通过亲属选择的合作间接获得的健康状况。本项目的第一个目标是在长尾山雀的合作繁育系统中以这种方式划分适应度。长尾山雀在英国鸟类中是独一无二的，因为它有一个合作的繁殖系统，在这个系统中，失败的鸟类会在同一种群中寻找亲戚的巢穴，并通过帮助它们抚养后代来成为帮手，从而获得间接的健康益处。长尾山雀为这个项目提供了一个很好的模型系统，因为它们一直是(自1994年以来)长期实地研究的对象，每年都会系统地测量大量个体的许多相关行为和生活史特征(从2010年到2010年，共2500只)。这使我们能够衡量大量个体的生殖成功(即适合度)。我们还建立了社会和遗传谱系，这将使我们能够使用数量遗传学来确定与该物种社会行为进化相关的关键行为和生活史特征变异的遗传和环境基础。更具体地说，利用我们谱系中的亲属网络，我们将调查适应性和合作行为的衡量标准是否是可遗传的特征。其次，我们将调查个人的行为、形态和/或生活史的特定特征是否会随着他们直接或间接的适应而变化。我们特别感兴趣的是合作行为中可能存在的性别差异，因此个体获得的健康类型的性别差异，以及这对与男性和女性的直接或间接健康相关的其他特征的进化的影响。最后，我们将使用这个研究系统来解决进化生物学中另一个长期存在的问题：如果特定的特征(如合作行为)是可遗传的，并与适应能力有关，那么这些特征中的变异是如何保持的？我们将研究环境中的空间和时间变化是否会影响适合度和特定特征之间的关系。

The existence of cooperative behaviour has posed a major problem for evolutionary biologists since Darwin first recognised that natural selection predicts selfishness rather than cooperation. Therefore, the sophisticated societies of social insects (ants, bees and wasps) and the cooperative breeding systems of many vertebrates, where non-breeding helpers assist breeders in raising their offspring, have been a major focus of research by evolutionary biologists. The biggest advance since Darwin in our understanding of such behaviour was the introduction of the concept of kin selection (inclusive fitness theory) by Hamilton in 1964. The key insight was the idea that individuals could increase their evolutionary fitness by increasing the survival or productivity of their relatives, as well as through personal reproduction. However, the role of kin selection in the evolution of the cooperative breeding systems of vertebrates remains a matter of considerable debate. One of the problems underlying this gap in understanding is the difficulty of measuring the fitness gained directly via personal reproduction, and that gained indirectly through kin-selected cooperation. The first objective of this project is to partition fitness in this way in the cooperative breeding system of the long-tailed tit Aegithalos caudatus. Long-tailed tits are unique among UK birds in having a cooperative breeding system in which birds who have failed in their own breeding attempt seek out the nest of a relative in the same population and become helpers by assisting them in raising their offspring, thereby gaining indirect fitness benefits. The long-tailed tit provides an excellent model system for this project because they have been the subject of a long-term (since 1994) field study in which many relevant behavioural and life history traits have been measured in a systematic fashion each year for a large number of individuals (>2500 birds to 2010). This has allowed us to measure the reproductive success (i.e. fitness) of a large number of individuals. We have also established a social and genetic pedigree that will allow us to use quantitative genetics to determine the genetic and environmental basis for variation in key behavioural and life history characteristics associated with the evolution of social behaviour in this species.More specifically, using the network of relatives in our pedigree we will investigate whether measures of fitness and cooperative behaviour are heritable traits. Secondly, we will investigate whether particular features of individuals' behaviour, morphology and/or life history vary with either their direct or indirect fitness. We are particularly interested in the likely sex differences in cooperative behaviour, hence sex differences in the kind of fitness individuals gain, and the consequences of this for the evolution of other traits linked to direct or indirect fitness in males and females. Finally, we will use this study system to address another long-standing question in evolutionary biology: if particular traits (such as cooperative behaviour) are heritable and linked to fitness, how is variation in those traits maintained? We will examine whether spatial and temporal variation in the environment influences the relationship between fitness and specific traits.