Uncovering the genomic basis of an extraordinary plant invasion

With global trade, increasing numbers of species are introduced into new environments. Not all of these become established in the introduced range. The exact reasons as to why some species become established while others do not remain open to debate. Suggested as possible factors for invasion success are admixture of several source populations, rapid adaptation, and escape from native-range enemies. We here use the annual weed Ambrosia artemisiifolia which was introduced from North America to Europe in the late 19th century and became invasive since. To infer temporal changes in population structure and the presence of plant pathogens, we resequenced 655 specimens, including 308 herbarium specimens collected up to 190 years ago. We found signs of selection in Europe, especially in genes associated with defense. We found lower prevalence of some plant pathogens in the invasive range, suggesting escape from enemies could have enabled the invasive success of this plant.