Host-Parasite Coevolutionary Dynamics with Generalized Success/Failure Infection Genetics

Host-parasite infection genetics can be more complex than envisioned by classic models such as the gene-for-gene or matching-allele models. By means of a mathematical model, I investigate the coevolutionary dynamics arising from a large set of generalized models of infection genetics in which hosts are either fully resistant or fully susceptible to a parasite, depending on the genotype of both individuals. With a single diploid interaction locus in the hosts, many of the infection genetic models produce stable or neutrally stable genotype polymorphisms. However, only a few models, which are all different versions of the matching-allele model, lead to sustained cycles of genotype frequency fluctuations in both interacting species (Red Queen dynamics). By contrast, with two diploid interaction loci in the hosts, many infection genetics models that cannot be classified as one of the standard infection genetics models produce Red Queen dynamics. Sexual versus asexual reproduction and, in the former case, the rate of recombination between the interaction loci have a large impact on whether Red Queen dynamics arise from a given infection genetics model. This may have interesting but as yet unexplored implications with respect to the Red Queen hypothesis for the evolution of sex.