Date of Award

January 2012

Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Rebecca B. Simmons


Wild pigs are a damaging invasive species with a long history in the United States. However, during the last 30 years wild pigs have drastically expanded their invasive range and are now present in 44 U.S. states. Though historic records provide insights regarding original introduction histories in areas where pigs are long-established, little is known regarding sources for new populations. To develop a better understanding of recent invasions, I utilized an array of molecular markers (mitochondrial DNA sequence, nuclear microsatellites, and nuclear single nucleotide polymorphisms) to evaluate both the evolutionary history of introduced pigs and gene flow between populations indicative of dispersal pathways.

Mitochondrial sequence provided a basal understanding of pig invasions (i.e., geographic origins and breed associations) through evaluation of U.S. pigs in context of published sequence from around the world. However, mitochondrial relationships must be considered cautiously, as introduction sources can be obscured due to shared ancestry between Eurasian wild boar and domestic pigs and the ubiquity of some haplotypes in national and global datasets.

With microsatellites and single nucleotide polymorphisms, I identified multiple genetic groupings that corresponded to geographic distributions and known introduction histories. Through individual and population genetic distance analyses, I found that

dispersal patterns and sources for invasions of wild pigs can be identified using molecular techniques. I also identified an isolation by distance relationship at the national level and in California, which suggests that range expansion can be tracked in terms of gene flow across the landscape. However, my results did not resolve whether the association of genetic distance with geographic distance has resulted from diminishing rates of gene flow under a natural dispersal scenario or from genetic drift associated with anthropogenic dispersal; evidence of both pathways for pig invasion was apparent in my dataset. Further, landscape genetic analyses suggested some role for natural dispersal in range expansion in California.

My findings here suggest that ongoing research in the area of wild pig genetics would be productive. Additional samples from throughout the United States will be necessary to further resolve population genetic relationships and the role of anthropogenic and natural dispersal in range expansion.