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

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.

学界普遍认为，冰岛牛（Icelandic cattle）是在公元870-930年冰岛拓殖时期从挪威引入的。此前针对遗传关系开展的研究表明，冰岛牛与北欧北部本土牛品种的亲缘关系最为紧密。本研究借助冰岛牛以及29个西北欧牛品种的单核苷酸多态性（single nucleotide polymorphism, SNP）基因型数据，探究了这些品种间的亲缘关系与遗传混合（admixture）情况，并评估了冰岛牛的群体遗传结构。通过主成分分析（principal component analysis, PCA）、祖先血统推断以及群体分化与混合模式分析开展的群体结构研究显示，冰岛牛与三类芬兰牛（Finncattle）品种（东芬兰牛、北芬兰牛与西芬兰牛）以及瑞典山地牛的亲缘关系最为密切。冰岛牛的遗传混合程度极低。我们在冰岛牛群体中仅观察到极有限的群体结构，该结构差异源于种公牛贡献量的不均一性。长达千余年近乎完全的地理隔离，使得冰岛牛在遗传层面与其他牛品种形成了显著分化。