Parasitism as a driver of host diversification

Abstract

Parasites are ubiquitous and frequently impose strong deleterious fitness effects on host individuals. These effects often manifest at the microevolutionary scale through host assortative mating and local adaptation. At the macroevolutionary scale, parasite-mediated effects can not only cause population divergence leading to speciation but also cause extirpation of host populations, leading to extinction. The balance between parasite-mediated effects on both speciation and extinction determines species diversification patterns. However, empirical tests of the hypothesis that parasitism contributes to macroevolutionary dynamics of host speciation and extinction are lacking. In this Perspective, we discuss how parasites can affect host macroevolution and outline an approach to determine whether parasitism and diversification are linked. We predict that parasitism, similar to other species interactions, shapes the process of diversification specifically in host species. Testing this hypothesis will require further empirical research to investigate the role of parasitism driving host diversification across the tree of life.