Wild or Tame? In Search for the Genetic Origin of Wild Boar (Sus scrofa) in Sweden

The wild boar (Sus scrofa) has been a part of the Swedish fauna for thousands of years. Although it became extinct in the 17th century, populations reemerged in the 1970s and 1980s after escapes from enclosures. The country of origin of the wild boars kept in these enclosures is unknown. This study aims to investigate the origin and level of genetic diversity of Swedish wild boars, as well as to compare them with Swedish domestic pigs. Swedish wild boar samples were collected from four regions of Sweden: Skåne, Blekinge, Södermanland and Uppland. In total, 107 wild boars and 427 domestic pigs were genotyped using the 80 K SNP chip. Wild boars from Skåne and Blekinge were shown to belong to the same genetic group, whereas the Södermanland and Uppland formed separate clusters. Results from both principal component analysis (PCA) and fixation index (F_ST) analyses demonstrate that Swedish wild boars are genetically distinct from Swedish domestic pigs. Moreover, the ADMIXTURE analysis revealed no evidence of introgression from domestic pigs into Swedish wild boar populations. The genetic differentiation observed among Swedish wild boar populations further indicates that they originate from more than one external source population.