The evolutionary dynamics of local infection and global reproduction in host-parasite interactions

A fundamental question in both evolutionary biology and parasitology is why do different levels of virulence evolve in different parasites. Here we us e explicitly spatial lattice models to show how the spatial relationships o f infection and host reproduction determine the degree of virulence that wi ll occur. When the reproduction of the host acts over larger spatial scales than the infection process higher virulence is predicted. In contrast to b oth the mean-field and the case where infection acts over larger spatial sc ales than reproduction, the transmission and virulence predicted are always finite as "self-shading" of infected individuals always occurs. This proce ss may help to explain the evolution of the high virulence of larval diseas es of insects where reproduction clearly acts over greater distances than i nfection.