Mechanisms and Implications for Evolution via Sexual Conflict over Mate Choice
Date of Award
Doctor of Philosophy (PhD)
Ecology and Evolutionary Biology
In this dissertation, drawing inspiration from natural systems, I 1) establish the plausibility of the evolution of female resistance via sexual conflict over indirect benefits (wherein females evolve resistance in order to retain the genetic benefits of mating with males they prefer), 2) elucidate the complex mechanisms by which this may occur, and 3) reveal and explore new possibilities and outcomes for systems with conflict between males and females over mate choice. In Chapter 1, I present a new quantitative theoretical model that integrates concepts from both sexual selection and sexual conflict traditions, and demonstrate that any trait that hinders females’ sexual autonomy – their ability to freely choose mates – is sexually coercive, giving rise to selection for female resistance, even for scenarios wherein both attractive and unattractive males can act coercively. In Chapter 2, I introduce another theoretical model that shows that, rather than interfacing directly with male coercion potentially leading to a co-evolutionary arms-race, female resistance to coercion can take the form of an additional mate preference that “remodels” males by selecting for male traits that incidentally interfere with males’ own ability to coerce. I explore the conditions under which a remodeling process can occur, and reveal how male traits that enhance female sexual autonomy can function as a “public good,” allowing for frequency-dependent dynamics, as some females can get the benefits of autonomy without paying any of the cost of actively preferring the autonomy-enhancing traits. Finally, in Chapter 3 I use the generalizable concepts and insights from my theoretical models of sexual conflict over indirect benefits as the impetus for a new empirical analysis of aggressive behavior in lekking systems. Though it has been previously theorized that fighting among the aggregated males on a lek promotes female choice by giving visiting females more information about male quality, my theoretical work in Chapters 1 and 2 suggests that male aggression that disrupts courtship displays and copulations would give rise to sexual conflict over indirect benefits. Using a novel Relation Event Model that accounts for the sequence and timing of behavioral events, I show that although fighting may often be loosely correlated with mating success, fighting is in fact not attractive and does not directly lead to mating events. Rather, the results suggest that the regulation of fighting on leks to promote female sexual autonomy may be fundamental to stable lek evolution and the avoidance of a “Tragedy of the Lek,” wherein unchecked male aggression would otherwise cause the lek to fail as a space for female mate choice. The results also support the hypothesis that the regulation of aggression on leks may be the result of a previously unappreciated process of male remodeling by females. The development and refinement of theory and quantitative models are important tools that drive intellectual progress in the study of evolutionary processes. To advance scientific inquiry, this work shows the importance of being receptive to new lessons from natural history and of continually seeking to update our conceptual models of the world.
Snow, Samuel Spencer, "Mechanisms and Implications for Evolution via Sexual Conflict over Mate Choice" (2021). Yale Graduate School of Arts and Sciences Dissertations. 167.