The pig, Sus scrofa, is a foreign species to the American continent. Although pigs originally introduced in the Americas should be related to those from the Iberian Peninsula and Canary islands, the phylogeny of current creole pigs that now populate the continent is likely to be very complex. Because of the extreme climates that America harbors, these populations also provide a unique example of a fast evolutionary phenomenon of adaptation. Here, we provide a genome wide study of these issues by genotyping, with a 60k SNP chip, 206 village pigs sampled across 14 countries and 183 pigs from outgroup breeds that are potential founders of the American populations, including wild boar, Iberian, international and Chinese breeds. Results show that American village pigs are primarily of European ancestry, although the observed genetic landscape is that of a complex conglomerate. There was no correlation between genetic and geographical distances, neither continent wide nor when analyzing specific areas. Most populations showed a clear admixed structure where the Iberian pig was not necessarily the main component, illustrating how international breeds, but also Chinese pigs, have contributed to extant genetic composition of American village pigs. We also observe that many genes related to the cardiovascular system show an increased differentiation between altiplano and genetically related pigs living near sea level.
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We thank all people and institutions who helped to collect samples, provided genotypes or comments: network CONBIAND, coordinated by JV Delgado, J Capote, M Amills, T Strumia, S Quisbert, S de la Rosa, M Montenegro, M Sturek. We thank A Mercadé and A Castelló for genotyping part the animals and SE Ramos-Onsins for help with coalescence simulations. We are grateful to M Teran-Garcia (UIUC) and colleagues for her helpful assistance with running IPA’s system at the Department of Food Sciences and Human Nutrition, (license 11904312, obtained with an equipment grant from the Office of Research, College of ACES). WBP is funded by COLCIENCIAS (Francisco José de Caldas fellowship 497/2009, Colombia), CAS thanks grants from CAPES and EMBRAPA (Brazil), YRC is recipient of a PhD studentship from MICINN (Spain, ref. AP2008-01450), AEC is recipient of a PhD studentship from MICINN (Spain). Work funded by Consolider CSD2007-00036 ‘Center for Research in Agrigenomics’ and AGL2010-14822 grants (Spain) to MPE, EU SABRE project FOOD-CT-2006-01625, USDA project 2007-04315 (USA), Facultad de Ciencias Agrarias, San Pedro (UNA), Unión de Gremios de la Producción (UGP) and Empresa San Rafael Agricola y Ganadera SRL (Paraguay), Universidad Técnica de Oruro (Bolivia), Programa de Conservación de los Bancos de Germoplasma, Instituto Colombiano Agropecuario (grant 048-2011) and Ministerio de Agricultura y Desarrollo Rural (Colombia), and Centro de Validación de Tecnologı´as Agropecuarias (CEDEVA, Formosa, Argentina).