How parasite-mediated costs drive the evolution of disease state-dependent dispersal

The process of dispersal is central to population biology and evolutionary ecology. Because of negative impacts on host fitness, parasite infection generates potential costs of dispersal. However, theoretical predictions that address this issue are lacking. Here, we develop a mathematical model to demonstrate how the dispersal rate of hosts evolves under the influence of parasites in ecological scenarios incorporating pre-, during-, and post-dispersal infection/recovery events. We show that (1) the dispersal tendency is strongly biased towards either infected individuals or susceptible individuals, (2) the bias is inherently determined by the parasite-mediated relative cost of dispersal, and (3) the dispersal costs are determined by the autocorrelation of disease states (susceptible and infected) between pre- and post-dispersal. Our results suggest that parasite virulence in concert with the timing of infection drive the evolution of disease state-biased dispersal. To understand the evolutionary processes in spatial host–parasite systems, the parasite-induced costs of dispersal need to be taken into account.