Antagonistic coevolution between hosts and sexually transmitted infections

AO_SCPLOWBSTRACTC_SCPLOWSexually transmitted infections (STIs) are predicted to play an important role in the evolution of host mating strategies, and vice versa, yet our understanding of host-STI coevolution is limited. Here, I present a model of acute STI infection in populations with ephemeral mating dynamics, where hosts evolve their preference for healthy mates and STIs evolve mortality or sterility virulence. Mate choice readily evolves even though ephemeral mating and acute infections reduce the advantages of mate choice compared to previous theory based on serial monogamy and chronic infections. Selection for mate choice constrains both mortality and sterility virulence, leading to optimal strategies in each population, host polymorphism, or fluctuating selection. I show how the mode of virulence, costs associated with mate choice, recovery, and host lifespan impact on host-STI coevolution, with fluctuating selection most likely when hosts have intermediate lifespans, STIs cause sterility and longer infections, and costs of mate choice are not too high. The results reveal new insights into the evolution of mate choice and how coevolution unfolds for different host and STI life-history traits, providing increased support for parasite-mediated sexual selection as a potential driver of host mate choice, and mate choice as a constraint on STI virulence.