Fig. 5.
Model IV. Infection in viscous populations favors selection of short-lived hosts. (A) Modifications made to the model I to simulate viscosity. The maximum speed of individuals was limited, and the repulsion between individuals was introduced. Individual areas were calculated and used to find the dependence of fitness on local density (see Movie S5 for illustration of viscosity simulation and Movie S6 for epidemics progression in viscous populations). See Methods for details. (B) The principal stages of the selection scenario. After the initial expansion of the long-lived strain, the pathogen is encountered. Epidemics spread rapidly within long-lived individuals, resulting in its depression and extinction. (C) An example of simulation. β = 0.03, ASL = 90, ALL = 180, P = 0.9, B = 0.05, and R = 3 × 105. See Movie S7.