Pocket gophers (Rodentia: Geomyidae) and their ectoparasitic chewing lice (Phthiraptera Trichodectidae) have congruent phylogenies and show evidence of cospeciation. We examined a potential mechanism that could generate the observed pattern of cospeciation by testing the ability of lice to survive and reproduce on hosts other than their own. Our tests were conducted at the subspecific, specific, and generic levels relative to the natural host. Although lice established successful colonies at each level, colonization of new hosts diminished with increasing phylogenetic distance from the natural host of each louse. We suggest that the pattern of cospeciation results primarily from lack of opportunity for lice to colonize new hosts. However, in rare cases where lice disperse to new hosts, survival may be difficult on hosts that are not closely related to the natural host, which would reinforce the pattern of cospeciation.

Author notes

Associate Editor was Glennis A. Kaufman.