The overall goal of this research unit is to understand the impacts of the host immune system and the resident microbiota on pathogen virulence and resistance evolution. We study insects as they are excellent models, crucial providers of ecosystem services, important vectors of disease and the most diverse group of animals. To address our goal, we combine six empirical projects with one integrative theoretical and one bioinformatic project. We will use six insect species representing the three most speciose groups as host, and a suite of mostly bacteria, symbionts and pathogens. The new projects are based on a conceptual framework resulting from the current funding period. P1 will investigate the contributions of a host, the microbiota and a pathogen on the evolution of virulence using the fruit fly as a model. This will be achieved by decomposing virulence into host resistance and tolerance, and pathogen exploitation and per parasite pathogenicity and focus on non-competitive interactions. P2 is a theoretical project that will build a mathematical framework for the research unit to understand the consequences of tripartite interactions between hosts, microbiota and pathogens for pathogen virulence evolution. It will use the tools of population dynamics and models to understand interactions and collaborate with all other projects. P3 will usethe co-evolved honey bee-Paenibacillus system to study within-host virulence evolution of a spore-forming necrotrophic pathogen. It will study the co-evolutionary interactions between host and pathogen mediated by the microbiota. In P4, using Lagria beetles and their symbiotic Burkholderia bacteria, the evolution of symbiont establishment in the light of defense cocktails will be studied providing a deeper insight into co-evolution in a tripartite interaction. P5 will focus on the host side: how is the regulation of AMPs in the host altered by the presence/absence of microbiota? Using the mealworm beetle the evolution of virulence in P. entomophila will be studied. In P6, using roaches and termites, the evolution of host immune genes in response to the presence/absence of symbiotic Blattabacteria will be investigated, allowing comparative insights into how symbiont co-evolution has shaped host immune defenses and its consequence for pathogen virulence. P7 will investigate the virulence -transmission tradeoff in a pathogen with spores. It will use red flour beetles as hosts and investigate virulence evolution in the presence or absence of the microbiota. The bioinformatic project including the technical support will be pivotal as most empirical projects will partially rely on next generation sequencing. A postdoc will lead this work. We argue that our combined approach is essential to gain new insight into host-microbiota-pathogen interactions and their consequences for the evolution of pathogen virulence.

Further information on DFG websites: DFG - GEPRIS - FOR 5026: Integrating insect immunity, microbiota and pathogens