The Evolution and Development of Novel Traits, or How Beetles Got Their Horns

Abstract How do major novel traits originate and diversify in natural populations? This question addresses one of the most fundamental, yet unresolved, issues in evolutionary biology. Over the past decade, a peculiar group of organisms, horned beetles, has emerged as a model system for understanding the ecological, developmental, and genetic mechanisms that operate during the early stages of innovation and diversification. Here I review this body of research and highlight surprising insights into the interplay between proximate and ultimate mechanisms in the origins of diversity in these organisms.