Population genomics traces zebra mussel invasions along the expanding western North American front in Minnesota, USA to their source waters.

Zebra mussels (ZMs) continue to transform aquatic ecosystems, threaten native species, and accrue high economic costs in the Northern Hemisphere. In 2024, Minnesota (MN) in the western Great Lakes became the state with the most ZM-infested lakes in the USA. We used population genomics to examine recent ancestry and infer the source water bodies from which ZMs colonized > 1/3 of MN lakes infested from 2003 to 2018 (when spread accelerated), then compared results to traffic between lakes of boaters and anglers, the suspect invasion vectors. Lake Superior, the Upper Mississippi River, Lake Erie, and several inland lakes were our top-ranked inferred sources. We traced ZMs in 51 of 58 infested lakes to source water bodies in-state, but most were not from alleged "superspreaders" (sensu epidemiology). Mille Lacs Lake, a popular angling destination and boater network hub, was a notable exception as the inferred source for three lakes. In three MN lake-rich regions in which spread continues to be concentrated, invasions from nearby were common, and sources were most often not high boat-traffic lakes, suggesting that vectors other than trailered boats need further evaluation. Geographic expansion of our population genomic dataset could provide genomic surveillance and guide prevention of the continuing spread of ZMs.