Pathogens are ubiquitous in nature, causing morbidity and mortality in many host species. Hosts in turn also need to evolve strategies to defend themselves against these pathogens. However, these responses are rarely simple and not very straightforward to invoke, primarily because of various constraints arising out of intertwined strands of immunological, physiological and life-history variations. For example, the same immune responses against pathogens that are necessary to clear the infection can also impose a heavy energetic burden and physiological damages via reactive intermediates (e.g., damage to vital organs or DNA lesions during various metabolic diseases and cancer), eventually leading to poor health conditions. Conversely, the evolvability of immunity can also be intimately linked with specific contexts of host life history which increases the risk of injury, pathogen exposure and disease, thereby strengthening overall selection pressure on the immune system. In my thesis, I have tried to explore these various aspects of infection and immunity and their intimate links with life-history evolution, using tractable beetle models. In my talk, I will begin by revealing a form of previously-unknown cost of infection and immune activation in Tribolium castaneum where they drastically compromise germline maintenance and increase the rate of mutation transmission into the subsequent generations. I will also discuss how they can overcome such costs of mutation accumulation during long-term experimental evolution with pathogens, possibly via metabolic reprogramming. Following this, I will move on to highlight a rare example of how the evolution of sex-specific immunity and infection outcomes can evolve in Callosobruchus maculatus beetles as a function of possible mating-related injuries and infection risk due to sexual conflict within the population. Using beetles under enforced monogamy vs polygamy, I could show that the sexual dimorphism in immunity and infection outcome are more likely to evolve in polygamous beetles where males and females had higher divergence in their fitness optima and hence, were more conflicted.
Finally, in addition to my primary academic interest in host-pathogen interactions, I have also been fascinated by the various mechanisms underlying female-female intrasexual competition in nature which is gathering a lot of attention in recent years as a fundamental evolutionary ecological phenomenon. To this end, I thus worked on a unique form of chemically-driven female interference competition in flour beetles and discovered a novel role of carcass scavenging to compensate for the protein limitation among competing females. My results also implicated the possibility of disease transmission during scavenging but the benefits of scavenging under nutrient limitations might outweigh any such costs associated with scavenging. Together, in my thesis, I could thus successfully cover both the depth and breadth of diverse evolutionary ecological phenomena related to host-pathogen interactions and life history.
Basabi Bagchi is a PhD scholar in the Evolutionary Immunology lab under Dr. Imroze Khan at the Department of Biology, Ashoka University. Prior to joining her PhD she did her B.Sc in Microbiology from St. Xaviers College, Kolkata and M.Sc in Biochemistry from the University of Calcutta. She has been interested in evolutionary biology research ever since her graduation. Currently she is interested in understanding various aspects of host pathogen interactions and its evolutionary implications using insect model systems.