Panarctic Flora

672113 Draba pilosa Adams ex DC.

• DC., Syst. Nat. 2: 336 (1821). Described from the lower Lena River area in Yakutia (Siberia), leg. Adams. Type in G-DC!
• Draba aspera Adams ex DC., Syst. Nat. 2: 337 (1821). Described from the lower Lena River area in Yakutia (Siberia), leg. Adams. Type in G-DC!
• Draba alpina auct., non L. (1753).
• Draba barbata auct., non Pohle (1914).

2n= See notes.

Geography: Asian (N) - amphi-Beringian: SIB RFE ALA CAN.

Notes: North American authors have only rarely acknowledged Draba pilosa (but see Al-Shehbaz et al. 2010a). This is a common yellow-flowered Draba in northern Siberia, Beringia, and northwestern North America (western and northern Alaska, the northern Yukon Territory, and in N.W.T./Nunavut at least east to Victoria Island; specimens in ALA and CAN), i.e., a major (perhaps the major) species behind the erroneous reports of D. alpina from these regions. The circumscription of D. pilosa has been disputed. Russian authors have mostly accepted two species: D. pilosa Adams ex Fisch. and D. barbata Pohle. For our view of the name D. barbata as a synonym for D. corymbosa, see that species.

Draba pilosa is one of the most distinctive of the arctic yellow-flowered Drabas with its narrow leaves with very prominent and strengthened midvein and margins which are retained for many years as marcescent, the presence of uncommonly coarse and stiff simple and forked hairs, mainly along the margins and midvein, and the large (and fragrant) flowers on very slender pedicels. There is, however, a polymorphy in the material that may justify a treatment as two taxa. The two plants are similar in flowers and fruits but differ in leaf shape between dry sites where they have very narrow leaves with very thick midvein and margins (here belongs the type specimens of D. pilosa), and wet sites where they have broader leaves with less thick veins and margins. This could be ecological modification but there is also a variation in hairs, from purely coarse ciliate to mixed ciliate and branched, associated with the leaf shape and site differences. The two types co-occur quite regularly in both northern Yakutia and Alaska but keep apart in morphology and ecology. This possibly taxonomically significant variation is discussed by Al-Shehbaz et al. (2010a). In the more recent floristic treatments of Siberia (e.g., Nikiforova 1994), these plants key out as, respectivelly, D. pilosa and D. barbata. We therefore suspect that there may be two taxa: D. pilosa s. str. and one currently going by the name D. barbata but different from the original material available for that name. Another aspect is that there sometimes is problematic to draw a clear line between this D. barbata and D. corymbosa in the Beringian regions. A partly common allopolyploid origin may be suspected.

Löve and Löve (1975a) synonymized D. pilosa with D. alpina L. s. str. and reported the species to be octoploid (2n = 64). The first conclusion is erroneous and probably the second one, too. Siberian and Alaskan specimens of D. pilosa, including the types of D. pilosa and its synonym D. aspera, differ from D. alpina in almost every character except for having yellow petals. Linnaean D. alpina is decaploid, see above. The proven octoploid representatives of the D. alpina aggregate in the North Atlantic regions (D. oxycarpa) and in Beringia (D. "pseudo-oxycarpa", D. macounii) differ from D. pilosa in the majority of characters. Petrovsky (PAF proposal) rather reported D. pilosa to be tetraploid (2n = 32). This needs confirmation. A tentative investigation by H.H. Grundt (unpubl.) of an Alaskan population of wetland D. pilosa indicated it to be 10-12-ploid. Zhukova and Petrovsky (1984) reported several chromosome numbers for their D. barbata: 2n = 32 (East Chukotka), >90 (East Chukotka), >100 (Wrangel Island), and >120 (East Chukotka). The counted material probably belongs to more than one species.