Mitochondrial DNA sequences of various species of the genus Equus with special reference to the phylogenetic relationship between Przewalskii's wild horse and domestic

Abstract. The noncoding region between tRNA Pr° and the large conserved sequence block is the most vari-able region in the mammalian mitochondrial DNA D-loop region. This variable region (ca. 270 bp) of four species of Equus, including Mongolian and Japanese na-tive domestic horses as well as Przewalskii's (or Mon-golian) wild horse, were sequenced. These data were compared with our recently published Thoroughbred horse mitochondrial DNA sequences. The evolutionary rate of this region among the four species of Equus was estimated to be 2-4 x 10-8 per site per year. Phylogenetic trees of Equus species demonstrate hat Przewalskii's wild horse is within the genetic variation among the do-mestic horse. This suggests that the chromosome number change (probably increase) of the Przewalskii's wild horse occurred rather ecently