Draba corymbosa |
Draba sharsmithii |
|
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Baffin bay Draba, Baffin bay whitlow-grass, flat-top Draba |
Mount Whitney Draba, Mt. Whitney Draba, Sharsmith's Draba |
|
Habit | Perennials; (cespitose); caudex branched (with persistent leaves or leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Perennials; (densely cespitose); caudex branched (covered with persistent leaves or leaf remains, 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, (0.15–)0.3–0.7(–1) dm, glabrous throughout or pubescent proximally, trichomes simple and 2-rayed, 0.1–0.4 mm. |
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; petiolate; petiole base and margin ciliate, (trichomes simple and 2-rayed, 0.3–1 mm); blade oblanceolate to oblong-obovate or oblong, 0.4–0.7(–1) cm × 1–3(–5) mm, margins entire, surfaces pubescent abaxially with short-stalked, 2–5-rayed trichomes, 0.1–0.4 mm, adaxially glabrous or sparsely pubescent, with simple and short-stalked, 2-rayed trichomes. |
Cauline leaves | 0. |
0. |
Racemes | 2–9(–12)-flowered, ebracteate, (corymbose), slightly elongated in fruit; rachis not flexuous, pubescent as stem. |
2–10(–16)-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, 2.8–3.5 mm, sparsely pubescent, (trichomes simple and short-stalked, 2–4-rayed); petals yellow, spatulate to oblanceolate, 4–6 × 2–3 mm; anthers oblong, 0.6–0.7 mm. |
Fruiting pedicels | divaricate-ascending, straight or slightly curved upward, 4–11(–16) mm, pubescent, trichomes simple and 2–4-rayed. |
ascending, straight, (3–)5–12(–16) 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). |
oblong to lanceolate or narrowly ovate, twisted (curved), flattened, (5–)8–15(–20) × 2–4(–5) mm; valves usually glabrous, rarely pubescent, trichomes simple and short-stalked, 2-rayed, (marginal), 0.5–0.15 mm; ovules 16–20 per ovary; style (0.5–)0.9–1.8(–2) mm. |
Seeds | (brown), ovoid, 1–1.3 × 0.6–0.9 mm. |
oblong, 1–1.6 × 0.6–0.7 mm. |
2n | = 128, 144. |
= 36. |
Draba corymbosa |
Draba sharsmithii |
|
Phenology | Flowering Jun–Aug. | Flowering Jul–Aug. |
Habitat | Moist tundra, among calcareous or dolomitic rocks, gravel beaches, silt and clay terraces | Granitic outcrops and rocky slopes in open subalpine conifer communities |
Elevation | 0-1700 m (0-5600 ft) | 3300-3800 m (10800-12500 ft) |
Distribution |
AK; BC; NT; NU; YT; Greenland; Europe (Norway, n Russia); e Asia (Russian Far East, Siberia) |
CA |
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 sharsmithii is clearly related to D. cruciata; there is some evidence that it may be an allopolyploid incorporating a genome from that species. It is known only from the vicinity of Mount Whitney in the southern Sierra Nevada (Inyo County). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 301. | FNA vol. 7, p. 336. |
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. cruciata var. integrifolia |
Name authority | R. Brown ex de Candolle: Syst. Nat. 2: 343. (1821) | Rollins & R. A. Price: Harvard Pap. Bot. 1(3): 71. (1991) |
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