SEX AGAINST VIRULENCE - THE COEVOLUTION OF PARASITIC DISEASES

Reciprocal selection is the underlying mechanism for host-parasite coe volutionary arms races. Its driving force is the reduction of host lif espan or fecundity that is caused by a parasite. Parasites evolve to o ptimize host exploitation, while hosts evolve to minimize the 'parasit e-induced' loss of fitness (virulence). Research on the evolution of v irulence has mostly emphasized the role of parasite evolution in deter mining virulence. However, host evolution, accelerated by sexual recom bination, contributes to the evolution and expression of virulence as well. The Red Queen hypothesis predicts that genetic variation among h ost offspring facilitates selection for reduced virulence. Here, we ou tline a synthesis between current thinking about the evolution of viru lence and the evolution of sex.