New insights on the role of ecology and life-history in social evolution

Abstract

Biological altruism, defined as a behaviour that benefits others at an apparent cost to the focal individual, is found abundantly across different levels of biological organization. While kin selection has been useful for explaining both cooperation and conflict in specialized cooperative societies, more theoretical work has to be done to develop models for realistic ecological and life-history contexts. This thesis aims to fill this gap by providing several new insights on the role of ecology and life-history in various social systems. Firstly, I propose a model that incorporates realistic ecological mechanisms of population regulation and study how different population regulation mechanisms affect the evolution of helping behaviour. I show that nest-site limitation strongly favours evolution of helping behaviour even if the helpers are relatively inefficient. I also find that interactions between density dependent mechanisms and life-history traits affect the evolution of social behaviour. Secondly, I consider a resource allocation model for eusocial insect colonies that incorporates the dynamics of colony growth and the conflict between the queen and the workers over the sex ratio. I show that conflict over sex allocation gives rise to a suboptimal pattern of colony growth, while the queen wins the sex allocation conflict. Thirdly, I study optimal reproductive tactics in facultatively cooperative wasps. I show that co-foundress nests and costly helping can evolve even with a low average relatedness between co-foundresses, but only during the initial stages of the nesting cycle. Costly helping during the reproductive phase can only evolve if the relatedness between co-foundresses is high. In conclusion, this thesis demonstrates the importance of considering ecological and life-history aspects in the study of social interactions from early stages of helping behaviour to resolving conflicts in eusocial insect colonies.