Thursday, October 25, 2012

Przewalski's Horse and Domesticated Horses



Certain breed descriptions have claimed the Przewalski's Horse, an endangered wild horse, as a direct ancestor.  However recent mtDNA research (Ryder, Fisher, et al, 2011) indicates that Przewalski's Horse diverged from the ancestor of the modern horse approximately 160,000 years ago—long before domestication and development of modern horse breeds. 

Interestingly, mtDNA research by McCue, Bannasch, et al.(2012) shows that Przewalski's Horse is more closely related to Mongolian, Norwegian Fjord, Belgian, and Icelandic breeds than other breeds such as Thoroughbreds.   Although Przewalski’s Horse and the domesticated horse differ in number of chromosomes, the two species can interbreed.  McCue, Bannasch, et al.(2012) propose that mtDNA research indicates there was interbreeding of domesticated horses with Przewalski’s horses.
 
Horse herds in the wild where the range of the two equine subspecies overlapped--especially in Mongolia.  Since all existing Przewalski’s Horses are offspring of nine of these horses captured in 1945, said founding horses are not purebred but hybrids with domesticated horses.  In other words, the genetic material was from the domestic horse to Przewalksi’s Horse only.  The above example serves to caution the reader about making quick interpretations about breed origination on basis of mtDNA research.
 
Sources: 
McCue, M., Bannasch, D., Petersen, J., Gurr, J., Bailey, E, Binns, M., Distl, O., Guérin, G., Hasegawa, T, Hill, E., Lee, T., Lindgren, G., M. Penedo, M., Røed, K. Ryder, O, Swinburne, J., Tozaki, T, Valberg, S., Vaudin, M., Lindblad-Toh, K., Wade, C., & Mickelson, J.  (2012) A High Density SNP Array for the Domestic Horse and Extant Perissodactyla: Utility for Association Mapping, Genetic Diversity, and Phylogeny Studies, PLOS Genetics, Found on September 20, 1012 at http://www.plosgenetics.org/article/info:doi%2F10.1371%2Fjournal.pgen.1002451
Ryder, A., Fisher, Schultz, B., Pond, S., Nekrutenko, A.,  & Makova., K. (2011).  A massively parallel sequencing approach uncovers ancient origins and high genetic variability of endangered Przewalski's horses". Genome Biology and Evolution.

 

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