Mixed ancestry from wild and domestic lineages contributes to the rapid expansion of invasive feral swine

Authors: SMYSER, TIMOTHY - Animal And Plant Health Inspection Service (APHIS); TABAK, M. - Animal And Plant Health Inspection Service (APHIS); SLOOTMAKER, CHRIS - Animal And Plant Health Inspection Service (APHIS); ROBESON, M. - Animal And Plant Health Inspection Service (APHIS); MILLER, RYAN - Animal And Plant Health Inspection Service (APHIS); MEGENS, H. - Wageningen University; GROENEN, M. - Wageningen University; PAIVA, S. - Brazilian Agricultural Research Corporation (EMBRAPA); FARIA, D. - Brazilian Agricultural Research Corporation (EMBRAPA); Blackburn, Harvey; SCHMIT, BRANDON - Animal And Plant Health Inspection Service (APHIS); PIAGGIO, A. - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2020
Publication Date: 2/21/2020
Citation: Smyser, T.J., Tabak, M.A., Slootmaker, C., Robeson, M.S., Miller, R., Megens, H., Groenen, M., Paiva, S.R., Faria, D., Blackburn, H.D., Schmit, B., Piaggio, A.J. 2020. Mixed ancestry from wild and domestic lineages contributes to the rapid expansion of invasive feral swine. Molecular Ecology. 29(6):1103-1119. https://doi.org/10.1111/mec.15392.
DOI: https://doi.org/10.1111/mec.15392

Interpretive Summary: Feral swine are a threat to ecological systems and poise a threat to the domestic swine industry. This study evaluated the genetic basis of feral populations using samples from 6,566 feral swine samples. The study showed current feral swine populations come from a variety of breed origins and are often of mixed ancestry. Feral swine had dominant associations with western heritage breeds, followed by major pig breeds, and European populations of wild boar. The study suggests wild boar hybridization may contribute to population fitness heightening the populations' invasive capacity.

Technical Abstract: Invasive alien species are a significant threat to both economic and ecological systems. Identifying processes that give rise to invasive populations is essential for implementing effective control strategies. We conducted an ancestry analysis of invasive feral swine (Sus scrofa, Linnaeus, 1758), a highly destructive ungulate that is widely distributed throughout the contiguous United States, to describe introduction pathways, sources of newly-emergent populations, and processes contributing to an ongoing invasion. Comparisons of high-density single nucleotide polymorphism genotypes for 6,566 invasive feral swine to a comprehensive reference set of S. scrofa revealed that the vast majority of feral swine were of mixed ancestry, with dominant genetic associations to Western heritage breeds of domestic pig and European populations of wild boar. Further, the rapid expansion of invasive feral swine over the past 30 years was attributable to secondary introductions from established populations of admixed ancestry as opposed to direct introductions of domestic breeds or wild boar. Spatially-widespread genetic associations of invasive feral swine to European wild boar deviated strongly from historical S. scrofa introduction pressure, which was largely restricted to domestic pigs with infrequent, localized wild boar releases. The deviation between historical introduction pressure and contemporary genetic ancestry suggests wild boar-hybridization may contribute to differential fitness in the environment and heighted invasive potential for individuals of admixed domestic pig-wild boar ancestry.