Ancient breeds and modern genetics - A study of Icelandic horses and exmoor ponies

The Icelandic horse and the Exmoor pony are two of Europe's oldest indigenous horse breeds, shaped by centuries of isolation and harsh environmental conditions. Both have undergone genetic bottlenecks as their populations have declined, but they have also been affected in different ways by breeding selection.

A new study, conducted by researchers at the Swedish University of Agricultural Sciences, examined the breeds' genetic diversity, degree of inbreeding and areas of the genome affected by selection. The results showed that while the Icelandic horse has maintained an acceptable level of genetic variation, the Exmoor pony appears to have a worryingly low level of variation - although this needs further confirmation.

Relatively high levels of genomic inbreeding were seen in both breeds, but it was mainly of older origin, suggesting that recent breeding efforts have avoided close kinship pairings.

In the Icelandic horse, several signs of selection for performance traits were identified in the genome, particularly in the genomic region containing the so-called ‘gait gene’ DMRT3. In both breeds, there was also evidence of selection in the genome for traits such as metabolism, immunity and body size, probably due to adaptation to their natural environment.

The Exmoor pony also showed signs of selection in genomic regions with genes linked to coat color and fertility.

The results thus highlight both genetic adaptations to similar environments and differences in how the breeds have been used, and provide valuable insights for future breeding and conservation of genetic health.

Funding

The Agricultural University of Iceland’s Doctoral Fund, The Conservation Fund for the Icelandic Horse Breed, The Swedish Icelandic Horse Association (SIF), Blikastaðir Fund, The Icelandic Genetic Resource Council in Agriculture (AGROGEN) and The Swedish Research Council (VR). Open access funding provided by the Swedish University of Agricultural Sciences.

Link to the publication

Sigurðardóttir, H., Ablondi, M., Kristjansson, T., Lindgren, G. & Eriksson, S. (2024). Genetic diversity and signatures of selection in Icelandic horses and Exmoor ponies. BMC Genomics 25, 772.