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Summary Despite the Icelandic horse enjoying great popularity worldwide, the breeds gene pool issmall. This is because of a millennium of isolation on Iceland, population crashes caused bynatural disasters and selective breeding. Populations with small effective population sizesare considered to be more at risk of selection pressures such as disease and environmentalchange. By analysing historic and modern mitochondrial DNA sequences and nuclear coatcolour genes, we examined real-time population dynamics in the Icelandic horse over thelast 150 years. Despite the small gene pool of this breed, we found that the effective pop-ulation size and genetic profile of the Icelandic horse have remained stable over the studiedtime period.Keywords coat colour genetics, effective population size, historic DNA, Icelandic horse,mitochondrial DNA, selective breeding.The Icelandic horse is an ancient breed descended fromhorses imported by the original Scandinavian settlers ofIceland (Hendricks 1995). The breeds gene pool has beeneffectively closed for a millennium. Since the middle of the20th century, the Icelandic horse has been one of theworlds most popular breeds in terms of numbers of pedigreehorses (approximately 300 000 registered individualstoday; International Federation of Icelandic Horse Associa-tions 2010). The majority of the breed now lives outsideIceland, with breeding societies in existence in 19 countries.Nevertheless, a series of natural disasters, including adevastating famine in the 1790s, as well as the long isola-tion of the breed and strict selective breeding, havedramatically reduced the effective population size (N |
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