LAUSR

Pheromones are chemical signals that elicit innate and stereotyped responses in conspecifics, often with intricate species specificity. The remarkable diversity of pheromones has made them particularly useful for studying the physiological and evolutionary mechanisms underlying communication. However, most discussions on pheromone evolution focus on divergence among species and give little attention to the processes underlying overlap or cross-reaction among species. Here, we review the evolution of pheromones with particular emphasis on the processes that yield pheromones that are not species specific. Although costly interactions with heterospecifics exert selection for pheromone divergence, species isolation via other chemical or multi-modal cues and temporal or spatial barriers can alleviate selection for species specificity. Likewise, common aspects of animals’ evolutionary history, physiology, and ecology can yield convergent, homologous, or otherwise cross-reacting pheromones. We hope that our review stimulates continued research on pheromone species specificity, which has implications for understanding their identity, function, and evolution, and predicting the ecological consequences of changing environments.