Draba aurea |
Draba corymbosa |
|
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golden Draba, golden Draba whitlow-grass, golden whitlow-grass, twisted-pod Draba |
Baffin bay Draba, Baffin bay whitlow-grass, flat-top Draba |
|
Habit | Perennials; (not cespitose); caudex simple or branched; not scapose. | Perennials; (cespitose); caudex branched (with persistent leaves or leaf remains, branches sometimes terminating in sterile rosettes); scapose. |
Stems | sometimes branched distally, (0.5–) 1–3.5(–5.2) dm, pubescent throughout, trichomes simple (non-crisped), 0.4–1.3 mm, and 3–6-rayed ones, 0.1–0.5 mm. |
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). |
Basal leaves | rosulate; petiolate; petiole (distinct or obscure) ciliate, (trichomes simple, to 0.8 mm); blade oblanceolate to obovate, (0.4–)1–3.7(–5) cm × (1–)2–7(–10) mm, margins entire or denticulate, surfaces pubescent, trichomes stalked, (2–)4–7 (or 8)-rayed, 0.2–0.5(–0.6) mm. |
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. |
Cauline leaves | 5–20(–26); sessile; blade oblong to lanceolate or ovate, margins entire or dentate, surfaces pubescent as basal, sometimes adaxially with simple trichomes. |
0. |
Racemes | (10–)18–52(–72)-flowered, usually bracteate on proximalmost 1–12(–17) flowers, rarely ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. |
2–9(–12)-flowered, ebracteate, (corymbose), slightly elongated in fruit; rachis not flexuous, pubescent as stem. |
Flowers | sepals (green or yellowish), oblong, 2.2–3 mm, pubescent, (trichomes simple and branched); petals yellow, oblanceolate, 3.5–5 × 1.5–2.5 mm; anthers ovate, 0.4–0.5 mm. |
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. |
Fruiting pedicels | divaricate-ascending to ascending or suberect, straight, 3–13(–20) mm, pubescent as stem. |
divaricate-ascending, straight or slightly curved upward, 4–11(–16) mm, pubescent, trichomes simple and 2–4-rayed. |
Fruits | (often subappressed to rachis), lanceolate to linear-lanceolate or narrowly oblong, slightly twisted or plane, flattened, (6–)9–14(–17) × 2–3.5 mm; valves pubescent, trichomes simple and short-stalked, 2–4-rayed, 0.05–0.3 mm; ovules 28–38(–44) per ovary; style 0.5–1.2(–1.5) mm. |
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). |
Seeds | oblong, 0.9–1.3 × 0.5–0.7 mm. |
(brown), ovoid, 1–1.3 × 0.6–0.9 mm. |
2n | = 74. |
= 128, 144. |
Draba aurea |
Draba corymbosa |
|
Phenology | Flowering Jun–Aug. | Flowering Jun–Aug. |
Habitat | Rock outcrops, talus, damp gullies and meadows, subalpine conifer woodlands, alpine slopes and turf, tundra, road banks, river gravel | Moist tundra, among calcareous or dolomitic rocks, gravel beaches, silt and clay terraces |
Elevation | (0-)700-4200 m ((0-)2300-13800 ft) | 0-1700 m (0-5600 ft) |
Distribution |
AK; AZ; CO; ID; MT; NM; NV; SD; UT; WA; WY; AB; BC; MB; NF; NT; NU; ON; QC; SK; YT; Greenland
|
AK; BC; NT; NU; YT; Greenland; Europe (Norway, n Russia); e Asia (Russian Far East, Siberia) |
Discussion | Draba aurea is extremely variable in plant size, number of cauline leaves, number of bracteate flowers, style length, and fruit size, shape, orientation, twisting, and indumentum. Much of the variation in the number of bracts, style length, fruit twisting, and growth habit occurs in Greenland, where the type specimen was collected and where the species is found near sea level. The highly deviant chromosome counts (e.g., 2n = 40 + 1, 64, 82) listed by R. C. Rollins (1993) and S. I. Warwick and I. A. Al-Shehbaz (2006) are mostly unvouchered and have to be disregarded; counts of 2n = ca. 80 have been re-assigned to Draba glabella. Published (G. A. Mulligan 2002) and unpublished counts made by Mulligan and M. D. Windham from Alaska, British Columbia, Colorado, Quebec, Utah, and Yukon indicate that the most common chromosome number of D. aurea is 2n = 74 (or 72). This suggests that the species is an allopolyploid (hexaploid or higher), incorporating genomes from both euploid and aneuploid lineages (M. A. Beilstein and Windham 2003). Detailed cytological and molecular studies are much needed to fully understand this widely distributed and highly variable species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 7, p. 294. | FNA vol. 7, p. 301. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. aurea var. aureiformis, D. aurea var. leiocarpa, D. aurea var. luteola, D. aureiformis, D. aureiformis var. leiocarpa, D. bakeri, D. decumbens, D. henneana var. maccallae, D. luteola, D. luteola var. minganensis, D. maccallae, D. minganensis, D. surculifera, D. uber | D. alpina var. bellii, D. alpina var. corymbosa, D. barbata, D. bellii, D. kjellmanii, D. macrocarpa, D. vestita |
Name authority | Vahl ex Hornemann: Fors. Oecon. Plantel. ed. 2, 599. (1806) | R. Brown ex de Candolle: Syst. Nat. 2: 343. (1821) |
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