Signal Diversity, Sexual Selection, and Speciation

Communication is ubiquitous. Developing a framework for the diversity of signals has important consequences for understanding alternative models of sexual selection and the processes contributing to speciation. In this article we review how models of neutral evolution in the perceptual space of signal perceivers provide a first step toward constructing a framework for signal diversity. We discuss how the distinction between additive and multiplicative effects of multimodal signaling represents a second step. We then assess how signal efficiency, reliability, and the aesthetics of perceivers provide distinct mechanisms for signals to be effective, thereby partly explaining signal diversity. Understanding the relative contribution of each of these mechanisms to the effectiveness of mate choice signals unravels the relative importance of alternative models of sexual selection. It can also help to distinguish whether divergence of communication is a driver or a consequence of speciation. Throughout the review we emphasize the importance of verification and learning in repeated interactions for understanding variation in signals.