Authors

Discussion

Host-parasite coevolution shapes trait distribution and dynamics of interacting populations. However, the role of host-parasite coevolution in complex natural systems, such as food webs, remains largely unexplored. Theoretical modelling can help to capture the complexity that stems from multiple species interactions. We designed a general individual-based model of a predator-prey-parasite system, in which predators are infected by trophically transmitted parasites when ingesting their prey. In our simulations, we allow predators and prey to evolve resistance, and parasites to evolve infectivity, with stochastic de-novo mutations. Following the gene-for-gene principle for infection genetics, we test whether the evolution of resistance in top predators mediates the community composition and dynamics (i.e. food web stability, diversity and species interactions). We show that predators’ partial resistance to parasites alters the system’s equilibrium for species coexistence, when the impact of the parasite on the predator is high. The resulting changes in populations’ sizes shape trait evolution further (e.g. a high abundance of resistant hosts imposes strong selection pressures on the parasites, which counter-evolve infectivity to persist). This highlights the dynamical interplay between ecological and evolutionary processes shaping community dynamics. Our general model allows to explore scenarios that test the impact of evolutionary change on ecological processes such as parasite-mediated trophic cascades and invasion ecology.