GELIFES Seminars - Barbara Taborsky

Barbara Taborsky (University of Bern)

The emergence of social phenotypes in cooperative breeders: plasticity matters

In cooperative breeders, young decide whether to stay in the natal territory and provide alloparental care or to disperse and breed independently. To understand the evolutionary mechanisms underlying this decision the main focus has been on the role of dispersal for population kin structure. Theory predicts a negative relationship between cooperative behaviour and dispersal tendencies, which is explained by philopatric, cooperative individuals gaining indirect fitness benefits through interactions with relatives, whereas ‘selfish’ dispersers are more likely to interact with unrelated individuals. These models assume a heritable basis of dispersal and cooperation, and an important role of indirect fitness benefits through interactions with relatives.

Using highly social cichlid fish as model, I will present evidence that if the assumptions of high within-group relatedness and genetic determination of behaviour do not hold, the relationship between cooperation and dispersal may go into reverse and become positive. If behavioural strategies are determined plastically, divergent life history trajectories resulting in distinct social types can emerge, where cooperative helpers disperse early whereas less helpful individuals stay as subordinates in the group. Which of these alternative social trajectories is pursued is determined by social and ecological contexts early in life. At the neural level, these behavioural differences go along with differential gene expression and stress axis programming in the brain. I will discuss alternative explanations for the emergence of social types that do not require within-group relatedness and narrow-defined inheritance of behaviour.