Figure 4.—

Dynamics of host and parasite genotype frequencies in a two-locus model with epistasis in costs of alleles at different loci (model B2) as a function of the number of host generations. There is no mutation. Autoinfection rate ψ = 0.9 and maximum cost of disease φ= 0.2. u₁, u₂, costs of host resistance; b₁, b₂, costs of parasite virulence; u₁ = 0.072 and b₁ = 0.024; u₂ = b₂ = 0.0975. (a) Maintenance of all four host genotypes (area C in Figure 3a). (b) Maintenance of all four parasite genotypes (area I in Figure 3b).