The Effects of Assortment on Population Structuring Traits on the Evolution of Cooperation

Population structure plays an important role in the evolution of social behaviours, particularly by generating positive assortment on social interactions. This enables cooperative behaviours that have a net cost to the individual to spread by directing their benefits towards other cooperators. Previous work on the coevolution of population structures and social behaviours has suggested that the evolution of population structuring traits is strongly influenced by the dominant social strategies. Here we investigate the idea that the coevolution of population structure and behaviour can be enhanced in favour of cooperation when there is also assortment on the population structuring traits themselves. This paper presents a simulation model that investigates the effects of evolving this second-order assortment and introduces a mathematical framework to model it in terms of the replicator equation. We find that with second order assortment the dominant social behaviour trait does not necessarily have to control the evolution of population structure, increasing the range of social scenarios in which population structures that support increased cooperation can evolve.