The impact of predation on the evolution of hosts and parasites.

The study of infectious diseases, particularly those transmitted by parasites, is vital to improving our understanding of the evolutionary and population dynamics which may arise during an epidemic outbreak or ongoing endemic. The evolution of host-parasite systems within complex communities is not fully understood. With the use of mathematical models, I build upon our theoretical knowledge of this area. By including a predator population in these systems, I determine how this impacts the evolution of host resistance against infection and multiple enemies, specifically parasites and predators. I also determine when parasite populations are likely to evolve intermediate host manipulation in order to reach a final host. Additionally, trade-offs are included within the host and parasite populations as evolving such defences or manipulation is likely to come at a cost. The presence of the predator increases the potential for host diversity to arise. Experimental work is used to determine the existence of trade-offs occurring in the Plodia interpunctella (Indian meal moth) host system. My results reveal the underlying ecological feedbacks, created by relative population densities and growth rates, which drive host-parasite evolution, whilst uncovering the key effects of the predator population. The inclusion of such complexities is important as they clearly affect host-parasite evolution. Overall, I provide an insight into the interesting dynamics arising in these systems. Future studies in this area will continue to develop and improve our understanding of these complex systems