Ashby B & Farine D (2022) Social information use shapes the coevolution of sociality and virulence. Evolution. 76:1153-1169.
Social contacts can facilitate the spread of both survival-related information and infectious disease, but little is known about how these processes combine to shape host and parasite evolution. Here, we use a theoretical model that captures both transmission processes to investigate how host sociality and parasite virulence (co)evolve. We show how selection for sociality (and in turn, virulence) depends on both the intrinsic costs and benefits of social information and disease as well as their relative prevalence in the population. Specifically, greater sociality and lower virulence evolve when the risk of infection is either low or high and social information is neither very common nor too rare. Lower sociality and higher virulence evolve when the prevalence patterns are reversed. When disease and social information are both at moderate levels, the direction of selection depends on the relative costs and benefits of being infected or informed. We also show that sociality varies inversely with virulence, and that disease may be unable to constrain the evolution of sociality. Together, these findings provide new insights for our understanding of group living and how apparently opposing ecological processes can influence the evolution of sociality and virulence in a range of ways.