Conceptions from the marriage of host-associated differentiation and multitrophic interactions

The possibility of insect parasite speciation and diversification arising from interactions with hosts has been under study for decades. The last decade of phylogenetic work on this issue has shown the common pattern of host switches in the history of parasites, rather than simple co-cladogenesis between pairs of interacting lineages. The association between host switching and diversification suggests that, in cases of ecological or adaptive speciation, selection pressures affecting a parasite's fitness on alternative hosts are consequential to parasite diversification. A multitrophic perspective on this process is important because many recent ecological studies show that bi-trophic interactions alone offer limited explanatory power for the evolutionary ecology of host use by insects. Here I use the concept of the multitrophic niche to generate and clarify hypotheses about the process of population divergence as well as patterns of insect-host association in ecological communities and phylogenetic space.