An analysis of the genomic architecture of the worldwide Irish Wolfhound dogs

The Irish Wolfhound (IW) is a dog breed characterised by a complex demographic history and reduced population size. In this study, we combined multiple population genomic approaches to characterise the genetic structure of 96 dogs collected from 23 countries worldwide, genotyped using the Illumina CanineHD BeadChip. Analyses of effective population size (Ne), linkage disequilibrium (LD) decay, heterozygosity and principal component analysis (PCA) consistently revealed limited genetic diversity. Complementary analyses of runs of homozygosity (ROH) and integrated haplotype score (iHS) identified extended homozygous segments and signatures of selection across the genome. ROH were predominantly short in length, and 40 samples showed ROH longer than 8 Mb. No ROH exceeding 16 Mb were detected, suggesting that these patterns reflect long-term demographic processes and historical selection rather than exclusively recent inbreeding. Particularly, 26 ROH islands were shared by at least 85% of the analysed individuals, with 3 ROHs shared by 100% of the population. Several ROH islands overlapped with regions previously reported in other hunting dog breeds and harboured genes associated with morphology, behaviour and diseases of major relevance to IWs, including osteosarcoma. Genomic regions identified by iHS also include genes involved in cancer and immune response. Compared with a previous IW population with publicly available genotypes, the dogs analysed here represent a more homogeneous subgroup. Overall, all approaches converged on a coherent genomic scenario, which highlights the combined effects of demographic history and selection in shaping the current genetic architecture of the IWs.