Systematic Relationships in the Artiodactyl Tribe Bovini (Family Bovidae), as Determined from Mitochondrial DNA Sequences

The systematic relationships of genera in the artiodactyl tribe Bovini were evaluated using two sets of mitochondrial DNA (mtDNA) sequences available for Bison, Bos, and Bubalus. One of these sets included 2,726 aligned positions from the two relatively conserved ribosomal RNA genes and three flanking transfer RNA genes; the other consisted of 247 base pairs from the rapidly evolving D-loop region. Most-parsimonious cladograms derived from the two data sets indicated that Bison and Bos are more closely related to each other than either is to Bubalus, as suggested from morphological, paleontological, and reproductive data. However, the traditional arrangement of the genus Bos is seriously challenged, as Bos grunniens groups first with Bison bison rather than with its congener Bos taurus. These results, when coupled with reproductive and other molecular data, strongly suggest that Bison should be treated as a congener of Bos rather than as a distinct genus in the tribe Bovini.