Figure 4.

Concurrent dynamics of winged and wingless aphids, summarizing the effects of VMPPs on NPT virus epidemics when aphid and virus invasions coincide. (A) Final population size of winged aphids. (B) Final incidence of virus‐infected plants. (C) Incorporating winged and wingless aphids introduces a previously unconsidered effect of VMPP: inoculum release from the local host population. Inoculum released is the total number of virus‐bearing winged aphids that emigrated from the host patch during a 60 day NPT virus epidemic. In (A)–(C) results are shown for varying plant acceptability VMPP only (for simplicity, there was no effect of virus infection on plant attractiveness, ν = 1). Blue dashed curve in (A)–(C) shows results when vector is already endemic for comparison (i.e., at steady‐state when the virus invades). Parameters for (A)–(C) were as per caption of Fig. 3 but with p = 0.2 throughout. In addition, the probability that individual offspring of aphids on any plant i, j develop to be winged was $A_{i,j}^6/(A_{i,j}^6+{(0.5\mathrm{\kappa })}^6)$. This form was chosen so that the probability that offspring develop to be winged is exactly 0.5 when aphid density on the plant (A _i,j) is κ/2, and in addition, is higher than 0.95 when aphid density on the plant is κ. All figures were generated using event‐based simulation only. Results represent the median of 4,000 replicate simulations commencing with virus invasion and simultaneous introduction of a single settled winged aphid into a field of 20 × 20 otherwise uncolonized susceptible host plants. For blue dashed curves, results represent the median of 1,000 replicate simulations with virus invasion lagged so that the vector had reached steadystate at the time of virus invasion.