Parasite-mediated sexual selection: To mate or not to mate?

Abstract

The concept of sexual selection has been around since Darwin, but the notion of parasites being a major driver of sexual selection in their hosts is relatively recent. Sparked by the inception of the Hamilton–Zuk hypothesis four decades ago, parasite-mediated sexual selection (PMSS) has since been a major focus of both theoretical and empirical research in evolutionary biology. This chapter discusses the development and current state of PMSS research, from the main hypotheses (good genes, transmission avoidance, parental care), to empirical data and mathematical modeling. It pays special attention to sexually transmitted infections (STIs) and considers the implications of host–parasite coevolution for PMSS, including recent theoretical advancements in this area. Finally, the chapter identifies directions for future theoretical and empirical research into PMSS.

Separation of evolutionary timescales in coevolving species

“…As such, this method is more suitable than others for modelling systems where one species evolves much faster than the other, but is not suitable for modelling systems in which the species evolve on similar timescales (e.g., in microbial communities, such as bacteria-phage coevolution). Still, our method offers a relatively straightforward test for determining whether results which assume comparable (or arbitrary) rates of evolutionary change still apply when one species evolves much faster than the other, and so will be especially beneficial in scenarios restricted to plants/animals coevolving with microorganisms (e.g., parasite-mediated sexual selection/conflict (Ashby, 2020; Ashby and Boots, 2015; Hamilton and Zuk, 1982; Pirrie et al, 2022; Wardlaw and Agrawal, 2019)).…”

“…However, important feedbacks remain between the ecological and evolutionary dynamics that play a fundamental role in shaping coevolution (Ashby et al, 2019). Separating evolutionary and ecological timescales is also a reasonable approximation for many real biological systems, as evolutionary dynamics are often, but not always (Pelletier et al, 2009), much slower than ecological dynamics.…”

Diagnostic testing and the evolution of detection avoidance by pathogens

“…While theoretical studies of detection avoidance evolution are rare, there are strong analogies with sexually transmitted infections (STIs), such as chlamydia and gonorrhoea, which may have evolved to be inconspicuous to avoid detection by choosy mates (Ashby et al 2019, Pirrie, Chapman, andAshby 2022). If prospective mates are less likely to choose partners who display signs of infection, then this can create strong selection for being inconspicuous, similar to selection for diagnostic testing avoidance.…”