S0125 Changing patterns of genomic variability following domestication of sheep.

Patterns of genome variation are highly informative for understanding the diversity and evolutionary history of domestic animal species. We analyzed sheep genomes from a broad collection of domestic breeds, along with their wild ancestor (O. orientalis) and other wild sheep species (O. canadensis and O. dalli). Following variant calling to identify ∼30 million high confidence SNP, we calculated nucleotide diversity to assess genome-wide differences in variability and applied homozygosity-based metrics to search for specific genomic regions that have undergone selection sweeps. As might be expected for a wild species, mouflon genomes had generally higher nucleotide diversity compared with domestic sheep. Furthermore, bighorn and thin-horn genomes showed depressed diversity, likely reflecting a strong founder effect and the impact of low effective population size. To approach a deeper understanding of changing patterns of diversity following domestication, we used available gene models and comparative information from human enhancer databases (ENCODE, Epigenetic Roadmap) to partition genomic sequence into a collection of features. These included exons, introns, UTRs, intergenic regions, and the components of gene regulatory machinery, such as promoters. For each genome feature, we compared the distribution in nucleotide diversity between wild and domestic sheep. We found clear evidence that exons have undergone a marked decrease in nucleotide diversity, when comparing wild to domestic sheep, in contrast to other genome features tested. We will also report on the collection of chromosomal regions that have undergone sweeps to build a deeper understanding of the impact of domestication in this important farmyard species.