Relationship of Icelandic cattle with Northern and Western European cattle breeds, admixture and population structure

ABSTRACT

Icelandic cattle is believed to have been brought from Norway during the settlement of Iceland around AD 870-930. Previous research on genetic relationships has indicated that Icelandic cattle is most related to northern Nordic indigenous breeds. Using single nucleotide polymorphism genotype data from Icelandic cattle and 29 Northern and Western European cattle breeds, we studied relationships and admixture among these breeds, and assessed population structure in Icelandic cattle. Population structure analysis through principal component analysis, estimation of ancestry, and analysis of patterns of population splitting and mixing revealed that Icelandic cattle are most related to three Finncattle breeds (Eastern, Northern and Western Finncattle), and Swedish Mountain cattle. Icelandic cattle has very low levels of admixture. We observed very limited population structure in Icelandic cattle. The observed structure was due to variable sire contributions. Over 1000 years of almost complete isolation has made Icelandic cattle highly genetically distinct from other cattle breeds.

KEYWORDS:

• Bos Taurus
• genetic diversity
• TreeMix
• PCA
• SNP
• livestock

Acknowledgements

We are grateful to Baldur Helgi Benjamínsson for his continuous support and advice. We thank Guðmundur Jóhannesson for his assistance concerning the Icelandic breeding program records, and the Icelandic Cattle Farmers' Association, and the Icelandic Farmers' Association for providing access to genotype and phenotype data for the Icelandic cattle population. We thank Donagh Berry and Deirdre Purfield for the data from Ireland, and we thank Geno, SLU and LUKE for providing access to genotype data for Scandinavian populations. This work was financially supported by the dairy cooperative Auðhumla, MS Iceland Dairies (Mjólkursamsalan) and the cooperative Kaupfélag Skagfirðinga.

Disclosure statement

This article is a part of Egill Gautason's PhD programme, which is funded by the dairy cooperative Auðhumla, MS Iceland Dairies (Mjólkursamsalan) and the farmer cooperative Kaupfélag Skagfirðinga. Other authors declare no conflict of interest.