Wild parsnip is an invasive species with a global distribution in temperate climates. Parsnips are native to Eurasia and have been cultivated for more than five centuries. It is unclear whether the global invasion of this species is a consequence of escape from cultivation or the accidental introduction of a Eurasian wild subspecies. In this study, we used nuclear ribosomal DNA internal transcribed spacer (ITS) and chloroplast DNA (cpDNA) markers to evaluate the genetic structure of wild parsnip in its native range (Europe) and in three distinct geographic regions where it is considered invasive: eastern North America, western North America, and New Zealand. We also compared wild and cultivated parsnips to determine whether they are genetically distinct. From 112 individuals, we recovered 14 ITS and 27 cpDNA haplotypes. One ITS haplotype was widespread; few haplotypes were rare singletons. In contrast, at least two lineages of cpDNA haplotypes were recovered, with several novel haplotypes restricted to Europe. Cultivated parsnips were not genetically distinct from wild parsnips, and numerous wild parsnip populations shared haplotypes with cultivars. High genetic diversity was recovered in all three regions, suggesting multiple introductions.

Nomenclature: Wild parsnip, Pastinaca sativa L. PASA2.

Management Implications: The availability of molecular data and advances in population genetic analysis have made it possible to estimate the patterns of species migrations with considerable precision. Findings from historical colonization and dispersal studies can shed light on human-mediated transport of biological materials and provide a broad understanding of how humans may have contributed to the introduction and spread of an invasive species. Evidence obtained in this study indicates that escape from cultivation led to the globalization of wild parsnips and introduced populations have high genetic diversity. Increased levels of diversity in invasive populations can act as a primer for rapid adaptive evolution of this noxious invasive species. Future studies with increased sampling and additional loci have the potential to elucidate specific patterns of colonization and admixture in this agriculturally entwined invasive plant and may serve as a model for investigating the natural and agricultural history of plant species that exist in wild, cultivated, and feral forms.