Draba corymbosa |
Draba maguirei |
|
---|---|---|
Baffin bay Draba, Baffin bay whitlow-grass, flat-top Draba |
Maguire's Draba |
|
Habit | Perennials; (cespitose); caudex branched (with persistent leaves or leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Perennials; (cespitose, forming loose mats); caudex branched (with some persistent leaf bases, branches often creeping, 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, (0.4–)0.7–1.7(–2.2) dm, usually glabrous, rarely proximalmost parts and sterile shoots pubescent, trichomes short-stalked, 2–4-rayed, 0.2–0.5 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; sessile; blade oblanceolate, (0.5–)0.7–1.4(–2) cm × 1.5–3.5(–5) mm, margins entire, surfaces pubescent with stalked, cruciform, and 2- or 3-rayed trichomes, 0.2–0.6 mm, (sometimes trichomes only on margins or apex, not ciliate, midvein obscure abaxially). |
Cauline leaves | 0. |
0. |
Racemes | 2–9(–12)-flowered, ebracteate, (corymbose), slightly elongated in fruit; rachis not flexuous, pubescent as stem. |
5–18(–23)-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, 2.5–4 mm, glabrous; petals yellow, oblanceolate, 5–7 × 2–3 mm; anthers ovate, 0.5–0.6 mm. |
Fruiting pedicels | divaricate-ascending, straight or slightly curved upward, 4–11(–16) mm, pubescent, trichomes simple and 2–4-rayed. |
divaricate-ascending to ascending (not expanded basally), straight, 5–13(–18) 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). |
broadly ovate to lanceolate, plane (not curved), flattened, (3–)4–6.5(–8) × 2–3 mm; valves glabrous or puberulent, trichomes simple, 0.05–0.2 mm; ovules 4–8 per ovary; style 0.6–1.7 mm. |
Seeds | (brown), ovoid, 1–1.3 × 0.6–0.9 mm. |
ovoid to oblong, 1.6–2 × 1–1.3 mm. |
2n | = 128, 144. |
= 16, 32. |
Draba corymbosa |
Draba maguirei |
|
Phenology | Flowering Jun–Aug. | Flowering May–Jul. |
Habitat | Moist tundra, among calcareous or dolomitic rocks, gravel beaches, silt and clay terraces | Dolomite outcrops, talus, rocky slopes |
Elevation | 0-1700 m (0-5600 ft) | 1600-2900 m (5200-9500 ft) |
Distribution |
AK; BC; NT; NU; YT; Greenland; Europe (Norway, n Russia); e Asia (Russian Far East, Siberia) |
UT |
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.) |
Draba maguirei is known from the Bear River Range in Cache County. Despite this very narrow distribution, the species includes two ploidy levels (diploid and tetraploid) that are morphologically and ecologically distinct (M. D. Windham, unpubl.). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 301. | FNA vol. 7, p. 318. |
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 | |
Name authority | R. Brown ex de Candolle: Syst. Nat. 2: 343. (1821) | C. L. Hitchcock: Revis. Drabas W. N. Amer., 70, plate 5, figs. 37a–c. (1941) |
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