Tracing the First Steps of American Sturgeon Pioneers in Europe

Background: A Baltic population of Atlantic sturgeon was founded ~1,200 years ago by migrantsfrom North America, but after centuries of persistence, the population was extirpated in the 1960s,mainly as a result of over-harvest and habitat alterations. As there are four genetically distinctgroups of Atlantic sturgeon inhabiting North American rivers today, we investigated the geneticprovenance of the historic Baltic population by ancient DNA analyses using mitochondrial andnuclear markers.Results: The phylogeographic signal obtained from multilocus microsatellite DNA genotypes andmitochondrial DNA control region haplotypes, when compared to existing baseline datasets fromextant populations, allowed for the identification of the region-of-origin of the North AmericanAtlantic sturgeon founders. Moreover, statistical and simulation analyses of the multilocusgenotypes allowed for the calculation of the effective number of individuals that originally foundedthe European population of Atlantic sturgeon. Our findings suggest that the Baltic population of A.oxyrinchus descended from a relatively small number of founders originating from the northernextent of the species' range in North America.Conclusion: These results demonstrate that the most northerly distributed North American A.oxyrinchus colonized the Baltic Sea ~1,200 years ago, suggesting that Canadian specimens should bethe primary source of broodstock used for restoration in Baltic rivers. This study illustrates thegreat potential of patterns obtained from ancient DNA to identify population-of-origin toinvestigate historic genotype structure of extinct populations.