Analysis of the history and population structure of the Icelandic horse using pedigree data and DNA analyses

The Icelandic horse breed is believed to have been founded on the basis of horses brought to Iceland eleven hundred years ago. It has in past decades gone from close to obsolete to enjoying considerable popularity with about 250,000 horses in at least 19 countries. To characterize the population structure pedigree data for over 300,000 individuals was analysed, calculating parameters such as effective population size, effective number of founders and ancestors, as well as inbreeding. DNA sequence analysis was also used to assess population structure and genetic diversity. The Icelandic horse population is genetically uniform despite differences in the use of genetic material between areas, has high levels of heterozygosity, numerous D-loop haplotypes, and an effective population size above one hundred horses. Despite long-term isolation, fluctuations in population size, and a selective breeding program the Icelandic horse population is well-off in regards to genetic diversity.