Sexual conflict in the alfalfa leafcutting bee, Megachile rotundata, and the effect of the haplodiploid genetic system

Sexual conflict, when the evolutionary interests of males and females diverge, is a major force driving the evolution of males and females. Males evolve harmful traits that benefit males at the expense of female fitness. Females evolve counter-adaptations to reduce the harmful trait's effects, leading to a sexual arms race. However, this evolution can be influenced by the species' genetic system, the organization and transmission of genes. In this dissertation, I focus on the dynamics of sexual conflict and its origin in haplodiploid systems. The genetic system affects the likelihood that new traits invade and spread and should affect the sexual arms race in a species. Using a theoretical model, I simulated the appearance of a new harmful male trait and female resistance to that trait in different genetic systems and found that haplodiploid systems were more likely to be invaded by these male and female traits, suggesting that haplodiploid species may more often exhibit sexual arms races. Female resistance was also more effective in haplodiploid systems. The remainder of this dissertation focuses on the alfalfa leafcutting bee (Megachile rotundata). Males exhibit a form of sexual conflict called sexual harassment, where males coerce females to mate through repeated attempts. I measured the fecundity of females housed under various sex ratios, which affected harassment rates. Females harassed more produced fewer offspring, demonstrating the cost harassment imposes on female fecundity. I examined how harassment indirectly affects offspring by increasing females' production of early-emerging offspring that developed as adults that same season. These offspring have fewer foraging opportunities than overwintering offspring that develop and emerge the following season. I infer that harassment creates poor foraging conditions for females, so females produce more early-emerging offspring to make the "best of a bad situation." Finally, I examined the males' perspective, testing for male mate preferences through laboratory choice tests. Larger males attempted to mate more and had an unexpected preference for previously mated females over virgin females. I demonstrate the impact of a species' genetics on its evolution and behavior as well as the value of haplodiploid species as model systems for sexual conflict research.