Comparative phylogeography: The use of parasites for insights into host history

Abstract

Parasites are useful biological tags of the ecology of their hosts. In this chapter, we will show that parasites can also be used as powerful “evolutionary prints” in order to generate new hypotheses about the history of their hosts. By this we mean that genes of a parasite might actually better reflect host history than genes of the host. This can be useful as incongruence between the genealogies of several genes within a species often limits the resolution of the species history. We will focus on the developing field of comparative phylogeography between hosts and parasites and show that parasites can highlight historical events affecting host lineages that can not be detected by the study of the host itself, such as past host migration or differentiation events. Congruence in host-parasite phylogeographies relies on long-term host specificity, which is favoured by limited dispersal abilities, direct life cycles, high abundance and prevalence of the parasite. Parasites might play the role of an evolutionary print of their host’s history if they present reduced ancestral polymorphism, i.e. when parasites have shorter generation times and lower effective sizes than their hosts. Provided that the appropriate parasite species is selected according to these conditions, there appears to be no limitation to the use of parasites as evolutionary prints of the phylogeography of their hosts