Species that are threatened in their native range, may actually prosper as introduced populations. To investigate how such introduced populations were established involves determining from where within the natural range the founder individuals originated. This can be accomplished through mtDNA barcoding. The common spadefoot toad ( Pelobates fuscus ) naturally occurs in the south and east of the Netherlands and has shown a rapid decline. Yet, a flourishing introduced population was recently discovered in the coastal dunes in the west of the country. We use mtDNA barcoding to determine the provenance of the introduced population. We sampled both native and introduced populations from the Netherlands and compared our sequences to haplotypes from across the entire distribution range. The mtDNA haplotypes found in the introduced population are distinct from those naturally occurring in the Netherlands and point towards an origin in the Pannonian Basin, on the boundary between Central and Southeastern Europe. ...