The genus Aster (sunflower family - Asteraceae) is now generally restricted to the Old World species.
The other species have now been reclassified as Afroaster, Almutaster, Canadanthus, Doellingeria, Eucephalus, Eurybia, Ionactis, Oligoneuron, Oreostemma, Sericocarpus and Symphyotrichum.