Phylogenetic relationships of pocket gophers (genus Geomys) based on the mitochondrial 12S rRNA gene

The mitochondrial 12S ribosomal RNA (rRNA) gene was sequenced from 16 indiv iduals representing 10 species of the genus Geomys. DNA, sequences of Crato geomys castanops, Thomomys bottae, T. umbrinus, Dipodomys phillipsii, and P edetes capensis were included as outgroup taxa. Levels of 12S rRNA sequence divergence (average 3.5%, range 0.6-7.5%) suggested low levels of genetic differentiation within Geomys, with the transition: transversion ratio lowe r than that observed in other mammalian groups. Relative rate tests did nor detect significant levels of rate heterogeneity between Geomys and outgrou p taxa; however, certain ingroup taxa did show significant levels of rate h eterogeneity when compared with other ingroup members. Phylogenies consiste ntly supported previously identified relationships among taxa of Geomys.