Panarctic Flora

672125-30 The Draba cinerea aggregate D. arctica, D. arctogena, D. aff. arctogena, D. cinerea, D. oblongata, D. parvisiliquosa

Geography: Circumboreal-polar.

Notes: Elven and Petrovsky: Tolmachev's series Cinereae is kept together morphologically by predominance of (compared with the Draba nivalis group) coarse and more few-branched stellate hairs on all vegetative parts, scapes mostly with one to several leaves, infrutescences elongating, fruits with stellate or at least multibranched hairs, and comparatively large, milky white petals. The taxa are all polyploid (4x-10x) and at least some of the polyploids may have several diploid genomes in common (Brochmann et al. 1992, 1993, for D. arctica and D. cinerea). Four relevant studies of this group are Böcher (1966a), Mulligan (1971a), Andersen et al. (1999), and Andersen (2003).

Draba cinerea is assumed to be a common species throughout the Arctic except for the northern North Atlantic regions where it is largely replaced by D. arctica and D. arctogena. Draba cinerea, D. arctica, and D. arctogena are comparatively easy to keep apart in the North Atlantic regions (Andersen 2003) but this is not the case elsewhere. Parts of the northern Canadian, Alaskan, Far East, and Siberian material currently assigned to D. cinerea differ morphologically from North Atlantic D. cinerea, and some Alaskan plants also differ molecularly (Andersen 2003). The second most widely distributed species is D. oblongata, sometimes difficult to keep apart morphologically from D. arctica, D. arctogena, and D. cinerea but at another ploidy level. Draba parvisiliquosa is a problematic part of the aggregate, found within the Asian range of D. cinerea and D. oblongata. The six proposed species are reported to be at four ploidy levels: D. parvisiliquosa tetraploid and hexaploid (2n = 32, 48); D. arctogena, D. aff. arctogena, and D. cinerea mainly hexaploid (2n = 48); D. oblongata octoploid (2n = 64); and D. arctica decaploid (2n = 80).

The variation in this aggregate is largely unresolved. Its subdivision has relied much on an assumption of constant ploidy level differences between species. There are indications that this assumption fails in some Drabas. Several octoploid plants from northern Siberia and the Russian Far East do not fit morphologically the known octoploid D. oblongata but rather the hexaploid D. cinerea with a pubescence more or less entirely of stellate hairs. The separation of octoploid D. oblongata and decaploid D. arctica is also disputed. A combined morphological and molecular circumpolar revision of the entire aggregate is needed. Waiting for this, we accept the named taxa except for "ovibovina".