Draba yukonensis |
Draba nivalis |
|
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Yukon whitlowgrass |
snow Draba, snow whitlow-grass, yellow arctic Draba |
|
Habit | Perennials; (short-lived); caudex simple or branched (with persistent leaf remains); not scapose. | Perennials; (cespitose, usually forming mats); caudex branched (covered with persistent leaf bases); usually scapose. |
Stems | branched, 0.4–2 dm, pubescent throughout, trichomes simple, 0.3–1.2 mm, and 2–6-rayed, 0.05–0.6 mm. |
unbranched, 0.2–0.8(–1.2) dm, pubescent throughout, trichomes minutely stalked, 8–15-rayed, stellate, (non-crisped), 0.03–0.15 mm. |
Basal leaves | rosulate; subsessile; blade oblanceolate to narrowly so, 0.3–1 cm × 0.5–2 mm, margins entire, (ciliate, trichomes simple, to 1.3 mm), surfaces pubescent, abaxially with (rigid), simple and 2-rayed trichomes, 0.4–1.2 mm, sometimes with short-stalked, 3–6-rayed ones, 0.1–0.3 mm, adaxially with simple trichomes. |
rosulate; petiole (obsolete), ciliate throughout; blade oblanceolate to obovate, 0.2–0.9(–1.5) cm × 1–3(–5) mm, margins entire, (not ciliate), surfaces usually pubescent, rarely glabrescent, with short-stalked, 8–15-rayed, stellate, (non-crisped) trichomes, 0.05–0.15 mm. |
Cauline leaves | 1–3; sessile; blade ovate to oblong, margins entire, surfaces pubescent as basal. |
0 or 1; sessile; blade ovate or oblong, margins entire, surfaces pubescent as basal. |
Racemes | 5–20-flowered, ebracteate, considerably elongated in fruit; rachis not flexuous, pubescent as stem. |
3–9(–11)-flowered, ebracteate, elongated in fruit; rachis often slightly flexuous, pubescent as stem. |
Flowers | sepals ovate, 1.2–1.6 mm, pubescent, (trichomes simple and 2–4-rayed); petals white, spatulate, 1.5–2 × 0.7–0.8 mm; anthers ovate, ca. 0.2 mm. |
sepals ovate, 1.5–2 mm, pubescent, (trichomes simple and short-stalked, 2–5-rayed); petals white, spatulate to oblanceolate, 2–3.5 × 0.8–1.4 mm; anthers ovate, 0.2–0.3 mm. |
Fruiting pedicels | erect to ascending, straight, 0.5–3 mm, pubescent as stem. |
usually ascending, rarely divaricate, straight, 1–4.5(–8) mm, pubescent as stem. |
Fruits | ovoid to oblong, plane, not flattened, 2–5 × 1.5–2 mm; valves pubescent, trichomes short-stalked, 4- or 5-rayed, 0.05–0.3 mm; ovules 36–52 per ovary; style 0.1–0.3 mm. |
elliptic to narrowly oblong-elliptic, twisted or not, flattened, 3.5–9 × 1.5–2.2 mm; valves usually glabrous, rarely with 3–6-rayed trichomes on replum; ovules 12–24(–28) per ovary; style 0.1–0.4 mm. |
Seeds | oblong, 0.6–0.8 × 0.3–0.4 mm. |
ovoid, 0.6–1 × 0.5–0.6 mm. |
2n | = 16. |
|
Draba yukonensis |
Draba nivalis |
|
Phenology | Flowering late May–Jun. | Flowering Jun–Aug. |
Habitat | Open stony ridges on ancient beach in grassy areas and aspen stands | Rock outcrops and fellfields, meadows, open tundra, stream banks, gravelly beaches, roadsides |
Elevation | ca. 600 m (ca. 2000 ft) | 0-2500 m (0-8200 ft) |
Distribution |
YT |
AK; AB; BC; MB; NF; NT; NU; ON; QC; YT; Greenland; Europe (Finland, Norway [including Svalbard], n, w Sweden); e Asia (Russian Far East, n Siberia); Atlantic Islands (Iceland); circumpolar |
Discussion | Of conservation concern. Draba yukonensis is known only from Kluane National Park, southwestern Yukon Territory. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Draba nivalis is most often confused with D. lonchocarpa, and C. L. Hitchcock (1941) reduced the latter to a variety (var. elongata) of D. nivalis. A critical comparison reveals that there are enough differences to warrant their recognition as distinct species. Draba nivalis is distinguished by having non-ciliate leaf bases, basal leaf blades pubescent with trichomes 0.05–0.15 mm, stems and pedicels that are always pubescent, and fruits that are elliptic to narrowly elliptic-oblong, plane, and 3.5–9 mm. By contrast, D. lonchocarpa has ciliate leaf bases, basal leaf blades pubescent with trichomes 0.15–0.5 mm, stems and pedicels that are glabrous or sparsely pubescent, and fruits that are linear to lanceolate or oblong, slightly twisted or plane, and 6–15(–18) mm. Except for Alaska, D. nivalis does not grow in the continental United States, whereas D. lonchocarpa grows in nearly all Mountain and Pacific states. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 346. | FNA vol. 7, p. 322. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | D. caesia | |
Name authority | A. E. Porsild: Publ. Bot. (Ottawa) 4: 37, plate 7. (1975) | Liljeblad: Utkast Sv. Fl., 236. (1792) |
Web links |