Fig. 3

Population size changes in the host (a) and in the parasite (b) are generated for the GFG model via the parameters \(b=1, d=0.9, \delta =0.01, \beta =0.00005, c_{H_{1}}=c_{P_{2}}=0.05, c_{H_{2}}=c_{P_{1}}=0,\) and s=1. The initial conditions are H₁=H₂=4150 and I₁₁=I₁₂=I₂₁=I₂₂=415, so that the reference population sizes N_ref of the host and the parasite are given by 9960 and 1660, respectively, before their interaction starts at time zero. In both cases, the lower x-axes show time at the original scale of the dynamical system, whereas time is scaled by the respective values of N_ref·1/d for the upper x-axes. The left y-axes denote the absolute values of the changing population size and the right y-axes denote the relative values as ρ(t)=N(t)/N_ref. We evaluated the SFS for every second generation (on the original scale) in both cases and plot (c) r_20,j(t) for j=1 (black), j=3 (blue) and j=8 (red) against time for the host (dashed) and the parasite (solid). Note that the SFS shows similar results for all j≥8