The evolutionary dynamics of intralocus sexual conflict

Males and females often have divergent evolutionary interests, sparking two forms of sexual conflict: 1) interlocus sexual conflict (IRSC), an antagonistic interaction between the sexes that is mediated by different loci in each sex; 2) intralocus sexual conflict (IASC), where genes have opposite fitness consequences depending on the sex expressing them. Both forms of conflict appear to be common, yet there are large gaps in our understanding of their evolutionary dynamics. I focus on IASC and begin by synthesising theoretical concepts and empirical findings to better understand its evolutionary dynamics in a critical review of the topic (Chapter 1). I take a multifaceted approach by considering the maintenance, resolution, and consequences of this evolutionary feud. I then explore the extent of sexually antagonistic genetic variation for fitness in a large-scale study of Drosophila melanogaster, using hemiclonal analysis (Chapter 2). I compare results to data collected from the same population five years previously and show that the strength of the conflict has declined over time. Next, I show that subtle changes in temperature during the adult life-stage can dramatically affect sex-specific fitness and alter the direction of the conflict, which could contribute to the maintenance of IASC in natural populations (Chapter 3). I also present a new theoretical model that incorporates IASC into traits that are involved in IRSC arms races (Chapter 4). Surprisingly, IASC can have dramatic and contrasting effects on sexually antagonistic coevolution: stabilising arms races or drawing the sexes into repeated bouts of arms race escalation and stasis. Finally, I extend IASC theory to explore an analogous conflict between castes in social animal societies (Chapter 5) and suggest unique research opportunities to be capitalised upon in species with a division of labour. I summarise the work in this thesis by highlighting the broad and varied biological consequences of such a pervasive conflict (Chapter 6).