Cospeciation between Geomys pocket gophers (Rodentia: Geomyidae) and their Aphodius inquilines (Coleoptera: Scarabaeidae)

Most of the species of Aphodius that occur as inquilines living in the burrows of species of pocket gophers have been traditionally assigned to the cosmopolitan subgenera Koshantschikovius and Platyderides. Phylogenetic analysis of 140 morphological characters in the genus Aphodius provides evidence that Koshantschikovius and Platyderides are polyphyletic. New classifications are proposed. Nearctic Platyderides is subdivided into eight provisional taxa. The concavus species group with 15 species is removed from Koshantschikovius. Nine new species in the concavus group are described. The Geomys-associated species of the concavus group are shown to form a monophyletic clade. Phylogeny of that clade is compared to that of their hosts ( Geomys) and evidence for episodes of cospeciation between host and inquiline species is presented.