The coevolution of cooperation and socially-mediated dispersal: a model

Iris Prigent, Charles Mullon 

Limited dispersal can promote the evolution of cooperation by increasing relatedness between social partners. However it also intensifies kin competition, potentially cancelling the benefits of helping. Here, we analyse a model in which individuals evolve both (i) the probability of cooperating within social groups as adults, and (ii) the dispersal probability of juveniles conditional on the number of adults that have cooperated in the group, leading to a reaction norm for dispersal. We show that cooperation and socially-mediated dispersal coevolve such that individuals disperse more from cooperative groups, reducing kin competition and thereby favouring further cooperation. This evolutionary feedback allows cooperation to evolve even when it would be entirely disfavoured under unconditional dispersal. In some cases, selection leads to the long-term coexistence of full cooperators and full defectors, each expressing a distinct dispersal reaction norm: cooperators disperse less on average but are more responsive to the social environment. These outcomes are driven by selection on indirect fitness effects and do not require kin recognition or spatial memory. Our results show how social behaviour and dispersal plasticity can coevolve through a feedback that enhances cooperation among relatives and mitigates kin competition.