Multiple introductions from the Iberian peninsula are responsible for invasion of Crupina vulgaris in western North America.

•   Crupina vulgaris is a relatively recent invader to grasslands and other open habitats in western North America. Like related Centaurea species, it was introduced from the Mediterranean region, where it does not exhibit ruderal behavior. Determining the number and sources of invasion founders allows fuller interpretation of colonization dynamics and recognition of potential intercontinental carriers, both critical factors for curbing the spread of invasive species. •   We chose the molecular technique of random amplified polymorphic DNA (RAPD) to identify the number and sources of invasion founders from the eastern hemisphere, by comparing indigenous and invasive populations. •   Our results indicated that the five North American populations derived from three or more successful invasion events whose founders originated in the Iberian peninsula. •   Also inferred by the similarity clustering among eastern hemisphere populations is a more ancient origin of the genus to the east of the Mediterranean, a concept supported by the scarcity of suitable nonanthropic habitat in Spain. Its epizoochoric association with migratory movements of domestic herds suggests probable routes of migration first to southern Europe, then later to North America.