Sexually transmitted infections and host reproductive strategies

: (Alternative Format Thesis)

Abstract

Interactions between hosts and parasites are ubiquitous and can be incredibly intricate. Parasites, by nature, are disadvantageous for their hosts due to the costs they impose. This can drive hosts to adapt to their presence, for example through tolerance or avoidance. This can be seen in various theories of parasite-mediated sexual selection, where costly host ornamentation can help act as a signal to potential partners, indicating infection status. One specific subcategory of parasites are sexually transmitted infections (STIs).

Sexually transmitted infections have different transmission routes and characteristics than ordinary infectious diseases, and as such are expected to interact with their hosts in different ways. Because of the dependence of STIs on the host's mating system, one would expect that changes in host mating systems can have a substantial impact on the epidemiology and evolution of the STI. Furthermore, parasites can manipulate their hosts to increase transmission opportunities. Considering this from the perspective of STIs, it is reasonable to expect that STIs might manipulate host mating systems as a way of increasing transmission opportunities.

In this thesis we first use mathematical models to investigate how variations in sex ratio and other life-history traits affect the epidemiology of an STI. We then contest a recent paper and confirm that classical Fisherian theory on the evolution of sex ratio still holds. Following this we consider how an STI might manipulate divorce behaviours in hosts. Finally, we investigate how an STI might manipulate the mating rate of hosts and how the host coevolves to mitigate the effects of the STI.

Date of Award	28 Jun 2023
Original language	English
Awarding Institution	University of Bath
Supervisor	Ben Ashby (Supervisor) & Tamas Szekely (Supervisor)