Populations of introduced species in their new environments are expected to differ from native populations, due to processes such as genetic drift, founder effects, and local adaptation, which can often result in rapid phenotypic change. Such processes can also lead to changes in the genetic structure of these populations. In a new study published in AoB PLANTS, Stout et al. demonstrate that invasive populations of Rhododendron ponticum in Ireland are genetically distinct from ancestral populations in Spain and produce flowers that have wider floral tubes. Although Irish populations are spreading and Spanish ones are declining, they found low genetic diversity among individual plants within populations in both regions, and limited between-population gene flow. Wider floral tubes may have evolved in response to novel pollinators in Ireland, and although few studies examine invasive species in both their introduced and native habitats, this approach is needed to understand invasive species’ evolution and ecology.