XVI International Botanical Congess

Spotted knapweed, today a noxious weed in North America, was introduced into North America as a seed contaminant from southeastern Europe in the middle of the 19th century. According to recent research Centaurea maculosa LAM. (Described from Central France), as well as C. rhenana BOREAU, are synonyms of Centaurea stoebe L. subsp. stoebe, which is native to Western and Central Europe. These plants are biennial, strictly monocarpic and diploid (2n = 18). All the North American plants called Centaurea maculosa" are perennial, polycarpic and tetraploid (2n = 36), so they must belong to a different taxon. Parallel to the introduction into North America similar plants spread over the whole of Europe. The correct name of these is Centaurea stoebe L. subsp. micranthos (GUGLER) HAYEK (synonyms are Centaurea biebersteinii" and C. Micranthos"). Recent works using morphological and molecular techniques have proved that the plants introduced into North America and into Europe belong to the same taxon, C. stoebe L. subsp. micranthos (GUGLER) HAYEK.