Quantitative genetics of behaviour: cooperative breeding and lifetime fitness

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Why are some individuals more helpful than others? Why do some individuals settle close to their parents when others disperse? At first these appear to be extremely complex questions, given that we don't know whether behaviour is culturally or genetically inherited, or whether the context in which it is expressed matters. We inherit our genes from our parents and they inherit them from their parents. By building a family tree and looking at how the behaviours of family members are more similar than behaviours of unrelated individuals, we can discover the inherited contribution to these behaviours. We can then look at the benefits of these behaviours, and begin to understand why these behaviours have evolved in the way that they have. It is also very important to consider the situation or environment in which we express behaviour. We might stop to help someone who is lost on a sunny day, but not when it's pouring with rain; equally the people around us may influence our decision. Situations or environments clearly have the ability to influence our behaviour. If our behaviour influences our survival or breeding success (e.g. we get pneumonia helping someone when it's raining), and this behaviour (tendency to help) is inherited, then the environment has the ability to influence which behaviours evolve. Evolution is the result of selection; selection is the process that leads to the survival of successful behaviours. Individuals evolve behaviour that maximises their success in the conditions they experience; however, the environment or individuals that we interact with are constantly varying or changing, over time and space, and individuals must have a range of flexible behaviours to allow them to respond. Environmental or social factors can therefore influence the way in which our behaviour evolves. It is important to study how environmental and social variation influences behaviours in natural populations so that we understand how behaviour evolves and what maintains the diversity of behavioural strategies that occur. I will use recent analytical developments to explore which behaviours are inherited and how the environment and context in which behaviours are expressed influences this. I will investigate this in two natural populations of birds that represent the most detailed long-term genetic data sets of avian cooperative breeders. Cooperative breeding occurs in many fish, insects, birds and mammals (e.g. Meerkat Manor). I will investigate whether individuals differ in their cooperative-breeding behaviour and whether these differences are heritable; for example, I will quantify how much of the variation in tendency to help is genetic. I will then examine how the environment and social interactions influence behaviours. My two study species live in family groups on territories. Some territories are better than others, the weather is better in some years than others, and territories contain different individuals. I will ask how this environmental and social variation affects the expression of behaviours. By exploring how the environment and social surroundings influence evolutionary dynamics in these wild cooperative-breeding systems, I will gain insights into the genetic basis of behaviours that are likely to be similar in other cooperative species such as humans. This will improve our understanding of the degree to which individuals can adapt to environmental variability and change, crucial to species of conservation concern (e.g. one of my study species) in these times of accelerated anthropogenic change. Finally, I will assess the foundations on which our understanding of the evolution of social behaviour is based. I will do this by developing theoretical models, using precise fitness estimates from a closed population, to investigate the performance of fitness measures. This will have widespread relevance to cooperative breeding and evolutionary biology studies in general.