Sunday, October 28, 2012

Icelandic Horse mtDNA Research



Shetland Ponies, Wikipedia
Now let’s examine how recent mtDNA research supports or contradicts what historical and saga references have suggested are the origins of the Icelandic horse.  Jansen, Forster et al, (2002) extracted DNA from 318 unrelated horses representing 25 breeds from the US, Austria, Germany, Britain, Germany, Morocco, Spain, and Portugal.  Each horse had to have documented ancestry for at last five generations.  Additional mtDNA data was used from the GenBank or other publications creating a total horse population of 652.  Using this data, the researchers were able to create 17 very frequent mtDNA types indicating relationships among breeds.  As Jansen, and Forster, et al specify, “The clearest association between cluster and breed is evidenced by cluster C1 (n = 48): in our sample, it is geographically restricted to central Europe, the British Isles, and Scandinavia, including Iceland. A total of 17 of 19 documented horses with C1 are northern European ponies (Exmoor, Fjord, Icelandic, and Scottish Highland). Additionally, 14 of 27 undocumented horses with C1 are ponies, including Connemara ponies. The cluster is younger than perhaps 8,000 y, but definitely older than 1,500 y, because C1 was also found in two ancient Viking horses. Furthermore, mtDNA cluster E (n = 16) consists entirely of Icelandic, Shetland, and Fjord ponies. Taken together, this suggests a common late glacial or postglacial origin for these pony breeds.”
Mongolian Horse, Wikipedia

McCue, Bannasch, et al, (2012) conducted additional mtDNA research on samples from fourteen domestic horse breeds.  Results indicate that “The Norwegian Fjord, Icelandic, Mongolian, and Belgian clustered together in 3 dimensions, and Icelandic and Norwegian Fjord horses clustered tightly together in all 6 dimensions. This may reflect the suggested influence of Mongolian genes in the development of the Norwegian Fjord and subsequent development of the Icelandic horse from Scandinavian stock imported to Iceland.”    Note that the researchers caution against regarding the Belgian, a draft breed, as being closely related to the Norwegian Fjord, Icelandic, and Mongolian horses since its history shows that it could have little relationship to the other breeds.


Nordland Horse, Wikipedia
Additional research suggests that the Nordland, a rare Norwegian breed, is also very closely related to the Icelandic.  These horses exhibit very similar conformation and colors to the Icelandic horse and are also gaited  (Bjőrnsson and Sveinsson (2006)).  Representatives of the Nordland have not been included in recent mtDNA studies.

Without the benefit of some of the more recent mtDNA research, Bjőrnsson and Sveinsson (2006) argue against including the Norwegian Fjord as a direct ancestor of the Icelandic horse since the conformation and singular coloring of the breed (only dun coloring is acceptable) is so different from the conformation and multiple colors of the Icelandic breed.  Nor is the Norwegian Fjord gaited.  Certainly in the far past, the Norwegian Fjord could have had more colors especially since all extant Fjords are the offspring of one Fjord stallion born in 1891.  One could certainly reason that both breeds had a common ancestor that would explain the close relationship indicated by recent mtDNA studies.  

Fjord Mare and Foal, Wikipedia


 

As researchers refine their analytical techniques and increase the number of individual Icelandic horses included in their research, additional surprises about the breed’s genetic background may be revealed.   As Lippold, Matzke, et al (2011) caution, “…mitochondrial DNA alone is unlikely to resolve the geographical origin of horse domestication. Given the relatively recent origin of modern horse breeds and the extensive trade of horses as well as their use as a means of long distance transport, this result is, however, not entirely surprising. Resolving the timing and geographical origin of horse domestication will therefore require the use of alternative genetic markers.”
 
Sources:
Bjőrnsson, G., & Sveinsson, H.  (2006).  The Icelandic Horse, Edda Publishing, Reykjavik, Iceland.




Jansen, T., Forster, P. Levine, M., Oelke, H., Hurles, M., Renfrew, C., Weber, J., & Olek, K.  (2002) Mitochondrial DNA and the origins of the domestic horse.  Proceedings of the National Academy of Sciences of the United States.  Found September 10, 2012 at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC125071/
Lippold, S., Matzke, N., Reissmann, M.,  & Hofreiter, M.  (2011).  Whole mitochondrial genome sequencing of domestic horses reveals incorporation of extensive wild horse diversity during domestication, BMC Evolutionary Biology 2011, 11:328, http://www.biomedcentral.com/1471-2148/11/328
 


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


1 comment:

  1. Jessie,
    I am always glad when people comment on Blessi blog and share their love of horses. However, it was very interesting that three different "people," all with different names, commented on different entries in this blog with minutes of each other. Each comment included a link for something like "further blogs regarding Icelandic horses but said link went to a web page selling horses in Australia. Horses.

    I have deleted all the posts so the readers don't click the link thinking they are going to additional information on how horse vision works.

    And, yes, the Icelandic horse does have some unique characteristics--heavier coat (University of Penn sends out a call for donations of Icelandic horse hair every few years to test as part of a composite building material), lower tail set, often a thrifty gene metabolism to deal with the unique environment of Iceland. They also have yellow fat dispersed throughout the muscles which enables them to store carotene that they can graze on winter grass with insufficient Vitamin A. And the end part of the Icelandic horse digestive track is longer than in other breeds—probably to help with digesting lower quality grass. They also have about 35% slow twitch muscle fibers, which helps with endurance. But to me the best part of the Icelandic horse is their wonderful, calm, sensible, friendly attitude.

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