SSA: The evolution of cooperation in an arid-zone bird: bet-hedging, plasticity and constraints

Explaining the evolution of cooperation (behaviour that benefits others at a cost to self) is a key challenge in evolutionary and mechanistic biology. While it has long been recognised that cooperative behaviour may yield indirect fitness benefits to actors by increasing the reproductive success of related breeders, recent advances in the field have highlighted several potential complications with testing this idea in practice. First, cooperative behaviour may actually yield indirect fitness benefits by compressing variance in the reproductive success of related breeders. Second, the effects of cooperative behaviour on the reproductive success of related mothers may be shrouded by pre-emptive maternal responses to the presence of co-operators (e.g. mothers may reduce their pre-natal investment in offspring when they anticipate receiving cooperative post-natal care for their young). Third, the evolution of the best-studied form of animal cooperation (alloparental care; the provision of care to the offspring of others) could be constrained by genetic correlations with parental care. In this thesis we utilise long-term life-history and high density genomic data from wild Kalahari sparrow-weaver societies to provide the strongest support to date for each of these phenomena, shedding new light on their potential importance in shaping the evolution of cooperation.