Transpecific Signatures of Selection Related to Domestication in Sheep and Goats

As noticed by Darwin, domestic animals display similar morphological changes known as the domestication syndrome. These traits would rather result from variations in developmental genes possibly organised in a single genetic regulatory network. Besides, improvement traits shared by several domestic species might also have similar genetic bases (e.g., milk or meat in livestock). To detect the genomic regions involved in the early domestication process of sheep and goat, we produced more than 70 individual whole genome sequences (12 X coverage) for wild individuals from the domestication centre and three groups of domestics per species representing 2 traditionally-managed populations and a worldwide panel of breeds. A total number of 33.2 and 23.4 million SNPs were genotyped in Ovis and Capra, respectively, revealing a genetic load on genes related to morphological traits in domestic sheep. Using hapFLK and a stratified FDR approach, we detected 71 genomic regions contrasting the wilds to each domestic group. These regions showed either positive selection or relaxation in domestics, and corresponded to genes mainly related to immunity, production traits and nervous system. Among those regions, 22 were homologous between sheep and goats representing trans-specific signatures of selection. While most of genes related to immunity or production traits were species-specific, those related to the nervous system were over-represented among the trans-specific signals. These pleiotropic genes (KITLG, MTMR7, NBEA, HMGl-C) would account for both behavioural and morphological traits. They have already been identified as domestication-related traits in other species, and are good candidates for being key domestication genes.