Draba nivalis |
Draba sobolifera |
|
---|---|---|
snow Draba, snow whitlow-grass, yellow arctic Draba |
stolon Draba |
|
Habit | Perennials; (cespitose, usually forming mats); caudex branched (covered with persistent leaf bases); usually scapose. | Perennials; (cespitose); caudex often branched (with persistent leaf bases, branches elongated, sometimes terminating in sterile rosettes); scapose. |
Stems | unbranched, 0.2–0.8(–1.2) dm, pubescent throughout, trichomes minutely stalked, 8–15-rayed, stellate, (non-crisped), 0.03–0.15 mm. |
unbranched, (0.15–)0.25–0.6(–0.7) dm, pubescent basally, trichomes simple and 2- or 3-rayed, 0.1–0.5 mm. |
Basal leaves | 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. |
rosulate; subsessile; petiole (0–0.5 cm) margin ciliate, (trichomes simple, 0.2–1 mm); blade oblanceolate to spatulate or obovate, (0.3–)0.4–1.4(–2) cm × (1.5–)2–4(–6) mm, margins entire, (ciliate as petiole), surfaces usually pubescent, sometimes glabrescent, abaxially with stalked, 2–4-rayed trichomes, 0.1–0.5 mm, adaxially often with simple and 2-rayed trichomes, to 0.9 mm. |
Cauline leaves | 0 or 1; sessile; blade ovate or oblong, margins entire, surfaces pubescent as basal. |
0 (or 1); sessile; blade similar to basal. |
Racemes | 3–9(–11)-flowered, ebracteate, elongated in fruit; rachis often slightly flexuous, pubescent as stem. |
(5–)9–18(–23)-flowered, ebracteate, slightly elongated in fruit; rachis not flexuous, pubescent as stems proximally (trichomes often crisped). |
Flowers | 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. |
sepals ovate or broadly oblong, 1.7–2.5 mm, pubescent, (trichomes simple and stalked, 2-rayed); petals yellow, spatulate to oblanceolate, 3–4 × 1.5–2 mm; anthers ovate, 0.4–0.5 mm. |
Fruiting pedicels | usually ascending, rarely divaricate, straight, 1–4.5(–8) mm, pubescent as stem. |
divaricate-ascending, usually straight, rarely curved upward, 3–6(–10) mm, pubescent, trichomes simple and 2- or 3-rayed, (crisped, 0.1–0.5 mm). |
Fruits | 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. |
ovoid or ovoid-lanceolate, plane, inflated at least basally, (3–)4–6(–7) × 2–4 mm; valves glabrous or pubescent, trichomes simple and 2-rayed, 0.07–0.3 mm; ovules (4–)8–12 per ovary; style (0.3–)0.4–0.6 mm. |
Seeds | ovoid, 0.6–1 × 0.5–0.6 mm. |
oblong, 1–1.4 × 0.6–0.8 mm. |
2n | = 16. |
= 26. |
Draba nivalis |
Draba sobolifera |
|
Phenology | Flowering Jun–Aug. | Flowering Jun–Aug. |
Habitat | Rock outcrops and fellfields, meadows, open tundra, stream banks, gravelly beaches, roadsides | Igneous rock outcrops, fellfields, rocky slopes in mixed conifer and alpine meadow communities |
Elevation | 0-2500 m (0-8200 ft) | 3100-3600 m (10200-11800 ft) |
Distribution |
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 |
UT |
Discussion | 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.) |
Of conservation concern. Draba sobolifera is related to, and sympatric with, D. ramulosa, and occasional sterile hybrids are encountered. There is no evidence of introgression and the two species are easily distinguished (see discussion of 90. D. ramulosa). Draba sobolifera is known from the Tushar Mountains in south-central Utah (Beaver and Piute counties). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 322. | FNA vol. 7, p. 338. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. caesia | D. sobolifera var. uncinalis, D. uncinalis |
Name authority | Liljeblad: Utkast Sv. Fl., 236. (1792) | Rydberg: Bull. Torrey Bot. Club 30: 251. (1903) |
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