January 31, 2013

Genetic diversity of modern horses

Some very distinctive groupings of modern breeds emerge in this survey of modern horse breed genetic variation, and some of these groups have clear geographical associations.

Horses are very mobile, and can also be traded; much of their existing variation may also be the result of artificial breeding which might have included both selection for particular desirable traits as well as mixing different populations.

Now that there is a fairly clear picture of modern variation, it will be useful to explore how this has emerged over time. It'll be interesting to see how ancient horses fit into the modern picture: will they prove ancestral to those living in the same regions, or is there a process of continuous renewal, with multiple episodes of turnover, as good breeds emerge somewhere across the geographical range of the animal, and quickly replace less advantageous ones?
PLoS ONE 8(1): e54997. doi:10.1371/journal.pone.0054997

Genetic Diversity in the Modern Horse Illustrated from Genome-Wide SNP Data

Jessica L. Petersen et al.

Horses were domesticated from the Eurasian steppes 5,000–6,000 years ago. Since then, the use of horses for transportation, warfare, and agriculture, as well as selection for desired traits and fitness, has resulted in diverse populations distributed across the world, many of which have become or are in the process of becoming formally organized into closed, breeding populations (breeds). This report describes the use of a genome-wide set of autosomal SNPs and 814 horses from 36 breeds to provide the first detailed description of equine breed diversity. FST calculations, parsimony, and distance analysis demonstrated relationships among the breeds that largely reflect geographic origins and known breed histories. Low levels of population divergence were observed between breeds that are relatively early on in the process of breed development, and between those with high levels of within-breed diversity, whether due to large population size, ongoing outcrossing, or large within-breed phenotypic diversity. Populations with low within-breed diversity included those which have experienced population bottlenecks, have been under intense selective pressure, or are closed populations with long breed histories. These results provide new insights into the relationships among and the diversity within breeds of horses. In addition these results will facilitate future genome-wide association studies and investigations into genomic targets of selection.



shenandoah said...

Great article; I'm from Thoroughbred country in Central Florida, and delighted to see the 'Florida Cracker' breed on the chart! My all-time favorite breed is the Friesian, a light draft horse originating from the Netherlands. They're so beautiful and have wonderful personalities. But, I generally admire them all.





pconroy said...

Pity they don't include the "Irish Draught" and the Irish "Connemara Pony" as both these breeds may have contributed most genetically to the making of the Thoroughbred horses of today!

Shayan said...

There's a lot less resemblance between Connemara or Irish Draught and Thoroughbreds than there is between Muniqi Arabian or Akhal Teke and Thoroughbreds, phenotypically. Also, both Irish Draught and Connemara Ponies have had either Thoroughbred or Arabian outcrossing, so the genetics from extant horses would be confounded if trying to establish ancestry.

fmgarzam said...

I am no horse expert, got to this out of need of answer to several historical questions, that arise her in Monterrey, just 100 miles south of the Rio Grande and 200 miles west of the Gulf of Mexico.
Is anyone familiar with wild ponies', mustangs', genetics?
First colonization effort of New Mexico departed from here, probabley mustangs descend from their Portuguese and Castillian horses.
The other question was about Frisian mules, I had to research for a close friend. His ancestor an 1850's big businessman describes going to Matamoros, now across the river from Brownsville, riding a Mula Frisona. This region was famous for the best mules in Mexico. So there must have been a lot of Frisian horses here then, and perhaos since the late 1500's.
Frisians do not appear in that chart because they are also Called Belgian Black. Belgian and Percheron are in the chart.
We see Percheron here at parades, pulling beer carts
of local Brewery. Now owned by Netherland's Heineken.