Most of the diversity found across the animal kingdom is related to sex. Individuals invest an incredible amount of time and energy into fighting for and gaining the attention of potential mates, and this competition has resulted in a diverse array of reproductive traits and mating strategies. The McCullough lab is interested in the costs and benefits of these sexually selected traits, and how and why they differ among populations and species. Because sexually selected traits are complex and multifarious (involving behavioral, morphological, and/or molecular interactions between males and females both before and after mating), a holistic understanding of reproductive adaptations requires diverse and highly integrated approaches. Our research uses experimental tools from evolutionary biology, behavioral ecology, functional morphology, physiology, and molecular biology to answer fundamental questions about the evolutionary forces that give rise to biodiversity at different levels of biological organization – from proteins to structures to populations to species.