Eurasian Alpine Asters
The Diplactis Raf. group of Aster includes many species of white to pink-purple rayed asters with a chromosome base number of x=9 . Some of these are spring and early summer blooming species unlike most North American asters which are typically fall blooming. Species of A. sect. Alpigeni can be rather Erigeron-like in general appearance.
Diplactis was not accepted as a distinct genus, until Semple, Heard and Xiang (1996) transferred two species from Aster s.l. to Dipactis. In a cpDNA study by Xiang and Semple (1996), A. alpinus was found to be distantly related to Aster amellus (the type of Aster s.s. sensu Semple). Nesom (1994) treated the two species as related and placed them in Aster (s.s. sensu Nesom). The two hypotheses represent very different definitions of the genus Aster in the new strict sense. More study study was needed on the Asian species studied by Onno (1932; as Aster sect. Alpigeni). Brouillet, Allen, Semple and Ito (2001) using ITS DNA sequence data resolved the question and found that Nesom (1994) was correct; Diplactis sensu Semple belongs within Aster, in the new sense.