Morphological, genome-size and molecular evidence for the presence of another invasive east Asian Artemisia (Asteraceae) in Western Europe.
Based on morphological characteristics, genome size and molecular phylogenetics the identity of introduced taxa of Artemisia section Artemisia in Belgium and the Netherlands was critically re-assessed. It was shown that several populations of alleged A. verlotiorum belong to A. princeps instead. This species is native to Eastern Asia (China, Japan and Korea) and has not been reported before from Europe. Since the time of its arrival in Belgium and the Netherlands, more than two decades ago, A. princeps was able to locally grow as massive stands in mainly non-natural habitats. Morphologically, A. princeps is in many respects intermediate between the native species A. vulgaris and the Chinese species A. verlotiorum. Morphology, genome size and phylogenetic analyses of these three species and A. ×wurzellii- which is a hybrid of A. vulgaris × verlotiorum parentage that spontaneously arose in the British Isles-are thoroughly discussed. Contrary to A. verlotiorum, A. princeps produces viable seed in Western Europe. Hence, it is able to reproduce both clonally and sexually and potentially is a much bigger threat to native biodiversity than A. verlotiorum.