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Genome-Wide Analysis of the World's Sheep Breeds Reveals High Levels of Historic Mixture and Strong Recent Selection

Figure 6

Selection for sheep without horns (poll).

Animals from two breeds with horns (Dorset Horn and Merino) were pooled and compared with two polled breeds (Poll Dorset and Poll Merino). Pairwise FST was calculated between the two groups of animals for all 49,034 SNP, before smoothed values were plotted in order across the genome (top panel). A strong selection signal was observed on Chromosome 10 (SNP number 27,878–29,558 with the signal peak at SNP OAR10_29546872). Pairwise FST was also calculated between horned breeds (green line) or between polled breeds (blue line) before the smoothed values were plotted across Chromosome 10 (bottom panel). The peak was only observed where horned breeds were compared with polled breeds, verifying that the signal relates to the long-standing husbandry practise of selecting animals for the absence of horns.

Figure 6