Get access

Mitochondrial diversity supports multiple origins for invasive pigs


  • Associate Editor: Emily Latch


Our objective was to identify and evaluate mitochondrial diversity of wild pigs in the United States (U.S.). We obtained tissue samples from 81 individual pigs in 30 U.S. states and amplified a 403 base-pair region of mitochondrial DNA. We then downloaded overlapping sequences (n = 904) from public repositories to create a global reference. We used parsimony and Bayesian techniques to evaluate phylogenetic relationships, and we used origins of published sequences from Eurasian wild boar to establish a phylogeographic reference. We then compared gene and nucleotide diversity measures for introduced pigs in North America with those of domestic swine, Eurasian wild boar, and feral pigs within broad-scale geographic groupings. We identified 15 haplotypes for introduced pigs, representing wild and domestic animals from >30 countries spanning the indigenous range of S. scrofa. Mitochondrial diversity measures and phylogenetic relationships indicated a strong association between introduced pigs and European domestic breeds, reflecting the known history of human colonization, trade, and settlement in the United States. Based on the geographic distribution of haplotypes in North America, we found that range expansion is a product of translocation from historical populations and introduction from new genetic sources. Finally, haplotype network analyses provided evidence of past demographic expansions within lineages, contributing to observed mtDNA variation among introduced pigs in North America. © 2014 The Wildlife Society.