Evolutionary ecology of insect-pathogen interactions: Decomposing virulence, and the wild
Institute of Biology, Free University of Berlin, Berlin, Germany
Virulence, the decrease in host fitness caused by a pathogen, will be influenced by both host and pathogen traits. Defence against pathogens can be attributed to a combination of host resistance, i.e., limiting pathogen growth, and tolerance, i.e., damage limitation. Each of which is predicted to have distinct ecological and evolu-tionary consequences for pathogens. On the other hand, pathogens can affect virulence through their ability to exploit the host, i.e., their load inside the host, and through per parasite pathogenicity, i.e., the damage inflicted per pathogen. In this talk I will first address both the host and pathogen perspective of infection. From the hosts side I will present some unpublished data where we attempted to select Drosophila melanogaster over multiple generations for tolerance and resistance to examine the effects that it might have upon both the host and upon pathogen virulence. Second, from the pathogen perspective I will present data where, across pathogen species, we attempted to disentangle the relative contributions of exploitation and per parasite pathogenicity towards virulence. Third, I will take a more ecological perspective on host defences. To fully understand immune defence variation and function it is important to consider the ecological context in which defences are used. However, much of our extensive knowledge on host defences is from carefully controlled laboratory-based studies, which is quite different from the complex environments under which the defences have evolved. As a starting point to connect insight from the lab with that from wild organisms, we have carried out a survey of wounding. Wounds can directly reduce host fitness, can be sources of infection, and they elicit immune pathways for repair. I will present some unpublished data where we have systematically quantified wounding in natural D. melanogaster populations to provide some insight into variation in the risk of being wounded, and hence the selection pressure that it might place on a natural population.