The biological traits explaining the occurrence of host-associate differentiation: A meta-analysis

Host-associated differentiation (HAD) is a form of ecologically mediated speciation by which two or more parasite populations (e.g., insect herbivores) of the same species become genetically distinct due to their associations with different host species. HAD has been proposed as a potential explanation for the vast species diversity observed throughout parasitic insect lineages. In addition, predicting the occurrence of HAD will aid in the design of better pest control practices. Several biological traits have been suggested to explain the occurrence of HAD including mode of parasite feeding, age of interaction, host-fidelity, level of genetic recombination, differences in microbial species associations, and allochrony. To estimate the relative contribution of each of these traits we conducted a meta-analysis of the relevant literature. In general, HAD is explained by factors that cause or exacerbate differential selection experienced by parasites on different hosts. Results from our meta-analysis reveal several traits that can be used as reliable predictors of HAD.