Molecular evolution in Baiomys (Rodentia: Sigmodontinae): Evidence for a genetic subdivision in B. musculus

The genus Baiomys contains 2 extant species, the northern B. taylori and the southern B. musculus. Mitochondrial DNA sequences from the cytochrome-b gene were used to assess genetic variation within and between the 2 species. Samples of B. taylori and B. musculus each formed 2 separate clades and differed by an average sequence divergence of 11.62%. Average sequence divergence between the 2 clades of B. taylori was minimal (2.82%), whereas the value between the 2 clades of B. musculus was greater (6.46%). The level of genetic divergence between the clades of B. musculus is comparable to values seen between other sister species of sigmodontine rodents. The Trans-Mexican Volcanic Belt, Sierre Madre del Sur, and Rio Balsas may separate populations of B. musculus into northwestern and southern clades.