The taxonomy of the tribe Astereae has been dramatically changed after both morphologic and molecular evidence suggested that large genera such as Aster, as well as many others, needed to be separated into several genera or shifted to better reflect the plants' relationships. A paper by R. D. Noyes and L. H. Rieseberg showed that most of the genera within the tribe in North America actually belong to a single clade, meaning they have a common ancestor. This is referred to as the North American clade. Guy L. Nesom and Harold E. Robinson have been two of the most important taxonomists involved in the recent work and are continuing to re-categorise the genera within the tribe worldwide.
Sources: FNA, E+M, UniProt, NHNSW, AFPD