Draba corymbosa |
Draba serpentina |
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Baffin bay Draba, Baffin bay whitlow-grass, flat-top Draba |
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Habit | Perennials; (cespitose); caudex branched (with persistent leaves or leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Perennials; (cespitose); caudex branched (with persistent leaves, branches sometimes terminating in sterile rosettes); scapose. |
Stems | unbranched, (0.05–)0.2–0.8(–1.5) dm, pubescent throughout, trichomes simple and 2-rayed, 0.4–1 mm, with 3–5-rayed ones, 0.05–0.4 mm, (sometimes trichomes mostly simple). |
unbranched, 0.3–1.3 dm, glabrous throughout. |
Basal leaves | rosulate; petiolate; petiole base and margin ciliate, (trichomes often course, simple, 0.4–1.3 mm); blade oblanceolate to obovate, 0.6–1.8 cm × 1.5–5 mm, margins entire, surfaces pubescent, abaxially with stalked, 2–6-rayed trichomes, 0.2–0.6 mm, adaxially with primarily simple and stalked, 2-rayed trichomes, to 1.1 mm, with 3–5-rayed ones, 0.2–0.4 mm. |
rosulate; sessile; blade obovate to obovate-oblanceolate, 0.4–1 cm × (2–)2.5–4(–5) mm, margins entire, (ciliate, trichomes simple, 0.2–0.5 mm, apex acute), surfaces glabrous. |
Cauline leaves | 0. |
0. |
Racemes | 2–9(–12)-flowered, ebracteate, (corymbose), slightly elongated in fruit; rachis not flexuous, pubescent as stem. |
6–14-flowered, ebracteate, elongated in fruit; rachis not flexuous, glabrous. |
Flowers | sepals (grayish green), broadly ovate, 2.2–3 mm, pubescent, (trichomes simple, to 1 mm, sometimes with stalked, smaller, 2–4-rayed ones); petals (broadly patent), yellow, obovate, 4–6 × 3–5 mm; anthers ovate, 0.3–0.4 mm. |
sepals ovate, 2–3 mm, glabrous; petals white, spatulate to obovate, 5–6.5 × 2–3 mm; anthers ovate to oblong, 0.4–0.5 mm. |
Fruiting pedicels | divaricate-ascending, straight or slightly curved upward, 4–11(–16) mm, pubescent, trichomes simple and 2–4-rayed. |
divaricate-ascending, straight, 5–13 mm, glabrous. |
Fruits | oblong or ovate, plane, flattened, 6–12 × 3.5–5.5 mm; valves pubescent or puberulent, trichomes simple, 0.1–0.4 mm, (sometimes with short-stalked, 2- or 3-rayed ones); ovules 12–24 per ovary; style 0.6–1 mm (stigma distinctly wider than style). |
lanceolate to narrowly oblong, slightly twisted or plane, flattened, 6–12 × 2–3.5 mm; valves glabrous; ovules 8–16 per ovary; style 0.6–1.8(–2.5) mm. |
Seeds | (brown), ovoid, 1–1.3 × 0.6–0.9 mm. |
oblong, 1.1–1.4 × 0.7–0.8 mm. |
2n | = 128, 144. |
= 52. |
Draba corymbosa |
Draba serpentina |
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Phenology | Flowering Jun–Aug. | Flowering May–Jul. |
Habitat | Moist tundra, among calcareous or dolomitic rocks, gravel beaches, silt and clay terraces | Rock outcrops, talus, and gravelly soil in mixed conifer and subalpine meadow communities |
Elevation | 0-1700 m (0-5600 ft) | 3200-3600 m (10500-11800 ft) |
Distribution |
AK; BC; NT; NU; YT; Greenland; Europe (Norway, n Russia); e Asia (Russian Far East, Siberia) |
NV |
Discussion | Draba corymbosa, which is 16-ploid or 18-ploid with x = 8, is an extremely variable species of polyphyletic, allopolyploid origin. Most individuals appear to have decaploid D. alpina (2n = 80) in their parentage, but the other genomes are provided by hexaploid (2n = 48) and octoploid (2n = 64) species (C. Brochmann et al. 1993). O. E. Schulz reduced D. corymbosa to a variety of D. alpina; R. C. Rollins (1993) treated it as a distinct species. Draba corymbosa is distinguished from D. alpina by having pubescent or puberulent (versus glabrous or glabrescent) fruits, corymbose (versus usually elongated) fruiting racemes, and abaxial leaf blade surfaces always lacking (versus usually with some) simple trichomes. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Draba serpentina has been treated by other authors as a variety or synonym of D. oreibata. As indicated by I. A. Al-Shehbaz and M. D. Windham (2007), the two taxa are morphologically distinct, have different chromosome numbers, and are separated by over 480 kilometers. They are treated herein as separate species. Draba serpentina is known only from the Snake Range (White Pine County) and the Toiyabe Mountains (Lander County) in central Nevada. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 301. | FNA vol. 7, p. 335. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. alpina var. bellii, D. alpina var. corymbosa, D. barbata, D. bellii, D. kjellmanii, D. macrocarpa, D. vestita | D. oreibata var. serpentina |
Name authority | R. Brown ex de Candolle: Syst. Nat. 2: 343. (1821) | (Tiehm & P. K. Holmgren) Al-Shehbaz & Windham: Harvard Pap. Bot. 12: 414. (2007) |
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