Developments in the evolutionary theory of social interactions

Abstract

Altruistic behaviour, which benefits others but harms the actor, can evolve when copies of the underlying genes are transmitted to future generations by related beneficiaries. While we know that the mechanism of ‘kin selection’ answers to how altruism can evolve, the answers to why and when it can evolve are still obscure. The first aim of this thesis is to shed light to the evolution of altruism by identifying factors that facilitate or promote it. I find that the conditions under which altruism can evolve follow surprisingly simple principles that are independent of the taxon-specific traits such as fecundity. Further, by analysing the unique aspects of haplodiploid sex determination system (where males are born from unfertilized eggs and females from fertilized eggs) I find that its role in the evolution of altruism might have been prematurely dismissed by recent studies. The second aim is to contribute a new dimension to studies which link mating behaviour with the evolution of altruism. I find that virginity can be an adaptive mating strategy in haplodiploid taxa, and that adaptive virginity affects, and is affected by, the evolution of altruism. According to my analysis haplodiploidy offers a unique adaptive pathway to sociality. The third aim is to predict patterns of genomic imprinting in female soldier development in polyembryonic parasitoid wasps. The function of these soldiers is unknown, and it has been argued that their primary function is either altruistically protect their siblings, or spitefully kill their brothers to make room for sisters. I find that contrasting patterns of genomic imprinting are expected to be found depending on the function of the soldiers. These are empirically testable prediction, which can not only help find the function of these soldiers, but also help test social-evolution theory. The models built in this thesis highlight the need for better incorporation of future expectations, population parameters, and possible epigenetic changes to kin selection models.