PHYLOGENETIC-RELATIONSHIPS AND GEOGRAPHIC STRUCTURE IN POCKET GOPHERSIN THE GENUS THOMOMYS

Phylogenetic relationships among pocket gophers were examined based on the complete sequence for the mitochondrial cytochrome b gene (1140 b ase pairs). The tribe Geomyini (Geomys, Orthogeomys, Cratogeomys, and Pappogeomys) was well differentiated from the tribe Thomomyini (Thomom ys), using the heteromyid genera Dipodomys and Perognathus as the outg roup. Within the genus Thomomys, the species in the subgenus Thomomys (T. talpoides, T. monticola, and T. mazama) differed from those in the subgenus Megascapheus (T. bottae, T. townsendii, and T. umbrinus) by an average of 19.3% uncorrected sequence divergence. Extensive samplin g within one species, T. bottae, revealed strongly differentiated geog raphic units, with a maximum difference among localities of 15.7%. The geographic units within T. bottae coincided with geographic regions b ased on allozyme data in some areas, but not at all boundaries. The ge ographic units within currently recognized species in the bottae group (subgenus Megascapheus) were not grouped together with a high level o f confidence. The pattern suggests a rapid radiation of the bottae gro up, followed by geographic subdivision. (C) 1998 Academic Press.