The evolution of cooperative breeding in vertebrates

The evolution of cooperation ranks among the most fundamental unsolved puzzles in biology. Cooperative breeding, a form of cooperation in which helpers provide alloparental care while delaying reproduction, is especially challenging since it violates our expectation of selfishness under Darwinian evolution. After decades of study, the main gaps in our understanding of the evolutionary drivers of cooperative breeding still are: (1) the relative importance of direct versus indirect fitness benefits, and (2) the roles of spatial and temporal environmental variability. Limitations in previous research include the lack of a general framework for the coevolution of philopatry, reproductive competition and alloparental care, all crucial components of cooperative societies. Moreover, most previous studies consider all forms of alloparental care under the same fitness cost umbrella even though distinct helping tasks affect life-history traits differently. To address these gaps, I will first develop a framework to explore the phenomenon of age-dependent task specialization in vertebrates by varying fitness costs of different helping commodities, while considering the influence of relatedness and the environment. Second, results from the model will be tested using empirical data from a long-term study in the superb starlings and experimental fieldwork. Third, I will build a general model on reproductive conflict and skew that focuses on the context of dominants and subordinates’ interests aligned to obtain direct and indirect fitness benefits. Finally, I will test predictions from the model on reproductive skew with a phylogenetic comparative study using data on group size, genetic relatedness and environmental harshness collected from the literature. Thus, by using a combination of theoretical, empirical, and comparative approaches, I aim to improve our general understanding of long-standing questions on the evolution of cooperation and sociality.