Parasite local adaptation: Red Queen versus Suicide King

Parasites are generally expected to be locally adapted to their hosts, but the basis of this prediction involves two distinct areas of research: coevolutionary studies of infectivity and epidemiological studies of optimal virulence. The distinction between infectivity and virulence is sometimes blurred but is crucial to our understanding of parasite local adaptation. Recent theoretical and empirical work has greatly improved our understanding of the evolutionary processes affecting local infectivity adaptation. However, in spite of the attention paid to the evolution of virulence, only a few recent models have explicitly studied spatial variation in optimal virulence. Our understanding of parasite local adaptation will continue to improve through studies of the genetic basis of infectivity, research on spatial variation in optimal virulence in multiple-deme systems, and the combination of these two interacting components of parasite infection in theoretical and empirical studies.