On the origins of novelty and diversity in development and evolution: a case study on beetle horns.

The origin of novel features continues to represent a major frontier in evolutionary biology. What are the genetic, developmental, and ecological processes that mediate not just the modification of preexisting traits, but the origin of novel traits that lack obvious homology with other structures? In this chapter, I highlight a class of traits and organisms that are emerging as new models for exploring the mechanisms of innovation and diversification in nature: beetle horns and horned beetles. Here, I review recent significant findings and their contributions to current frontiers in evolutionary developmental biology.