Przewalski's Horse - Taxonomy

Taxonomy

The Przewalski's horse was described in 1881 by L. S. Poliakov. The taxonomic position of Przewalski's horse has always been problematic and no consensus exists whether it is a full species (Equus przewalskii), a subspecies of the wild horse (Equus ferus przewalskii), or even a sub-population of the horse (Equus ferus). Studies using DNA have been inconclusive, in part due to crossing domestic horses into the Przewalski's horse as well as the limited genetic variation present in the founder population of the Przewalski's horse. A 2009 molecular study using ancient DNA recovered from archaeological finds like bones and teeth places the Przewalski's horse in the middle of the domesticated horses, but more recent mitochondrial DNA analysis suggests that the Przewalski and the modern domestic horse diverged some 160,000 years ago. The karyotype of the domestic horse differs from that of Przewalski’s horse by an extra chromosome pair either because of the fission of domestic horse chromosome 5 in Przewalski’s horse or fusion of Przewalski’s horse chromosomes 23 and 24 in the domestic horse. In comparison, the chromosomal differences between domestic horses and zebras include numerous translocations, fusions, and inversions. Przewalski’s horse is known to have the highest diploid chromosome number among all equine species. Przewalski’s horse can interbreed with the domestic horse and produce fertile offspring (65 chromosomes).