One of the most exciting challenges facing evolutionary biologists is to understand the selective pressures that drive morphological diversity. Competition for mates, in particular, is a potent driver in the evolution of male morphology and has given rise to many of nature’s most extreme body forms, including the flashy ornaments of female choice, and the bulky weapons of male-male combat. Although weapons are equally impressive and diverse as ornaments, sexual selection studies have focused almost exclusively on the process of female choice and the evolution of ornaments. As a result, we still lack a theoretical understanding of the evolution of male weapons, and we simply cannot explain why sexually-selected weapons are so diverse. The overarching aim of my research is to understand the diversity of animal weapons.

Biomechanical models indicate that horns a structurally adapted for their species-specific fighting styles

Biomechanical models indicate that rhinoceros beetle horns are structurally adapted for their species-specific fighting styles

For my doctoral dissertation, I studied the elaboration and diversification of rhinoceros beetle horns, and how both selection to minimize the physiological of costs of horns, and selection to maximize the performance of horns during male-male combat help explain variation in the shape and size of these exaggerated structures. I found that the horns are surprisingly inexpensive to produce and carry, which may explain why these structures are both so elaborate and diverse. My research also provides strong evidence that horns are structurally adapted to meet the functional demands of fighting, and that variation in fighting styles has played a critical role in the diversification of weapon form.

For my postdoctoral research, I am beginning to explore how different ecological factors affect the evolution of male dimorphism and mating strategies in horned dung beetles. Specifically, I aim to understand how population density may shift the relative importance of pre- and post-mating sexual traits, and how differences in ecology contribute to the variation in morphology and behavior within and among species.


Advisors: Doug EmlenBret Tobalske, and Leigh Simmons