The role of biology and biologists: A meta-analysis of factors affecting host-parasite local adaptation

Adaptive divergence among populations can result in local adaptation, where genotypes exhibit higher fitness in native environments than in novel environments. A large body of theory has been developed to predict how different species traits, such as rates of dispersal and generation times, influence patterns of local adaptation in coevolutionary interactions between hosts and parasites. We used a meta-analysis of local adaptation across a wide variety of host-parasite interactions to evaluate some of these very common but relatively untested predictions. Our analyses indicate that asymmetry between hosts and parasites in their dispersal abilities was the best predictor of local adaptation in infectivity of parasites. In contrast, relative generation times and taxonomic relatedness of the host and parasites did not explain significant variation in infectivity. We also evaluated how experimental design influenced patterns of local adaptation, and found that there was a trend towards higher parasite local adaptation in fully reciprocal experiments. However, contrary to theoretical predictions, the spatial scale of the study did not explain significant variation in parasite adaptation. These results represent the first broad conclusions regarding the role of both the biology (species traits) and the biologists (experimental design) in finding local adaptation in coevolving species interactions.