Ancient Plumage Colour Genetics Reveal Goose Domestication and Hybridization

In archaeological assemblages, differentiating the European domestic goose and its wild progenitor, the greylag goose (Anser anser), has been challenging due to their similar skeletal morphologies. A short region of mitochondrial DNA (mtDNA) analysed from ancient DNA (aDNA) has been shown to distinguish wild greylags from domestic geese, but some ancient specimens display atypical haplotypes or haplotypes belonging to other wild Anser species. Plumage colouration could verify the domestic status of archaeological geese, as white or mottled plumage would be indicative of domestication. We analysed a SNP upstream of the EDNRB2 gene (endothelin receptor B-like) linked to white spotting and a 1-bp deletion in the Z-chromosomal MLANA gene (melan-A), causative of sex-linked dilution colour (almost white male and light grey female) in European domestic geese. Together, white spotting and sex-linked dilution result in white plumage. We also analysed a Chinese domestic goose (A. cygnoid)-specific 14-bp insertion within the EDNRB2 gene, which also causes white colour, and searched for possible evidence of historical interbreeding between European and Chinese domestic geese. We detected several plumage colour patterns such as solid wild type, white spotted (i.e., saddleback), nearly white with some grey spots, and white or autosexing with of 'almost white male and saddleback female'. Further, we discovered that European domestic geese had introgression from the Chinese domestic goose at least occasionally, from the 16th-17th century Common Era, due to the presence of both European and Chinese domestic goose white alleles in a single individual.