Host-Parasite Co-Evolution on Infection Networks: Effects of Parasite Sociobiology and Social Immunity
Westfälische Wilhelms-Universität Münster
Institut für Evolution und Biodiversität (IEB)
The evolution of conflict and cooperation is one of the main themes in evolutionary biology, and host-parasite interactions are potentially the most prominent examples of conflict relationships in natural systems. They are ubiquitous and thought to affect a wide range of evolutionary questions. Cooperation, on the other side, is thought to be rare and difficult to evolve. This research proposal aims to connect the two research fields of host-parasite co-evolution and evolution of cooperation by integrating social interactions, either amongst hosts or amongst parasites, into the co-evolutionary dynamics between host and parasite. The proposal focuses (1) on sociobiology of parasitic bacteria and (2) on social immunity in hosts. The project is purely theoretical. Host-parasite co-evolution will be modeled using a network approach, and the mathematical analysis will be conducted using computer simulations. Central to our project is to analyze the influence of network structure on host-parasite co-evolution. We propose to investigate the following two questions. (1) How does the sociobiology of parasites affect their evolution and how is this influenced by the host network structure? Experimental work has revealed that virulence of pathogens is often affected by evolutionary processes between different types of parasites in the same host. In the proposed project, we focus on sociobiological interactions commonly found in (pathogenic) microbes. A case in point is the presence of cooperative and non-cooperative genotypes in bacterial biofilms (e.g., Bacillus thuringiensis). Whereas previous theoretical work has appreciated the evolution of cooperation in biofilms, a theoretical analysis taking into account the role of the host is missing. We plan to investigate parasite evolution for given host interaction network structures. Important aspects are the evolution of cooperation between parasites as well as the evolution of virulence. (2) How does social immunity affect the evolution of parasites and how does it co-evolve with them? A basic form of social immunity is the production of antimicrobial substances, which are released to the environment and protect not only the producer but also nearby individuals. Examples include eusocial insects and the red flour beetle Tribolium castaneum. In order to perform an evolutionary analysis we consider the host interaction network and assume that links are not only potential pathways for disease transmission, but also for social immunity. Using computer simulations, we will investigate how social immunity affects parasite evolution and how social immunity evolves in the presence or absence or sociobiological pathogens. As a whole, we expect that this project will elucidate (1) the role of sociality in host-parasite co-evolution, and (2) how host-parasite interactions affect the evolution of cooperation amongst hosts and amongst parasites, respectively.