Evolutionary analysis of host pathogen interactions

Abstract

Pathogens are ubiquitous in nature, causing morbidity and mortality in many host species. newlineHosts need to evolve strategies to defend themselves against these pathogens. However, these newlinestrategies are rarely simple, primarily because of various constraints arising out of intertwined newlinestrands of immunological, physiological and life-history variations. For example, the same newlineimmune responses against pathogens that are necessary to clear the infection can also impose newlinea heavy energetic burden and cause physiological damage via reactive species (like damage to newlinevital organs or DNA lesions during metabolic diseases), eventually leading to poor health. newlineConversely, the evolution of immunity can be intimately linked with specific contexts of host newlinelife history which increase the risk of injury, pathogen exposure and disease, thereby newlinestrengthening overall selection pressure on the immune system. In my thesis, I explored various newlineaspects of infection and immunity and their intimate links with life-history evolution, using newlinetractable insect models. I begin by revealing a form of previously-unknown cost of infection newlineand immune activation in Tribolium castaneum that severely compromises germline integrity, newlineresulting in an increased mutation rate. I then discuss how the hosts can overcome such costs newlineduring long-term experimental evolution with pathogens, possibly via metabolic newlinereprogramming. Subsequently, in the next part of my thesis, I highlight how the evolution of newlinesex-specific immunity and infection outcomes can evolve in Callosobruchus maculatus beetles newlineas a function of mating-related injuries due to sexual conflict within the population. Using newlinebeetles evolving under enforced monogamy vs polygamy, I showed that the sexual dimorphism newlinein immunity and infection outcome are more likely to evolve in polygamous beetles where newlinemales and females undergo higher levels of sexual conflict. newlineFinally, in addition to my primary interest in host-pathogen interactions, my interest also newlineextends to various mechanisms underlying f