Draba aurea |
Draba subalpina |
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golden Draba, golden Draba whitlow-grass, golden whitlow-grass, twisted-pod Draba |
subalpine Draba |
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Habit | Perennials; (not cespitose); caudex simple or branched; not scapose. | Perennials; (cespitose); caudex simple or branched (with some persistent leaf bases); 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, 0.3–1(–1.3) dm, often glabrous throughout, sometimes sparsely pubescent proximally, trichomes simple and stalked, 2-rayed, 0.2–1 mm. |
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; sessile; blade (fleshy), oblanceolate to linear, (0.4–)0.5–1.4(–2) cm × (1–)1.5–3(–4) mm, margins entire, (ciliate at least apically, trichomes simple and 2-rayed), surfaces usually glabrous, rarely sparsely pubescent with simple and stalked, 2- (or 3-)rayed trichomes, 0.2–1 mm, (midvein obscure). |
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. |
(6–)10–28(–40)-flowered, ebracteate, elongated in fruit; rachis not flexuous, glabrous. |
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 broadly ovate, 1.7–2.5 mm, usually glabrous, rarely pubescent, (trichomes simple and short-stalked, 2-rayed); petals white, spatulate to obovate, 3–5 × 2–3 mm; anthers oblong, 0.5–0.7 mm. |
Fruiting pedicels | divaricate-ascending to ascending or suberect, straight, 3–13(–20) mm, pubescent as stem. |
divaricate-ascending, straight, (3–)5–10(–17) mm, glabrous. |
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. |
ovoid to lanceolate, plane, inflated at least basally, 4–8(–10) × 2.5–4 mm; valves glabrous or sparsely puberulent, trichomes simple, 0.02–0.1 mm; ovules 6–12 per ovary; style 0.2–0.9 mm. |
Seeds | oblong, 0.9–1.3 × 0.5–0.7 mm. |
ovoid, 1–1.5 × 0.7–1.1 mm. |
2n | = 74. |
= 26. |
Draba aurea |
Draba subalpina |
|
Phenology | Flowering Jun–Aug. | Flowering May–Jun. |
Habitat | Rock outcrops, talus, damp gullies and meadows, subalpine conifer woodlands, alpine slopes and turf, tundra, road banks, river gravel | Rocky knolls and marly limestone soil in pine-oak-juniper woodlands, edges of spruce-fir forests |
Elevation | (0-)700-4200 m ((0-)2300-13800 ft) | 1800-3400 m (5900-11200 ft) |
Distribution |
AK; AZ; CO; ID; MT; NM; NV; SD; UT; WA; WY; AB; BC; MB; NF; NT; NU; ON; QC; SK; YT; Greenland
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UT
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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.) |
Molecular studies (M. A. Beilstein and M. D. Windham 2003) and chromosomal data (Windham 2000, 2004) suggest that Draba subalpina is most closely related to D. cusickii and D. sobolifera. From those, it is easily distinguished by having white (versus yellow) petals, glabrous (versus pubescent) rachises and stems distally, and glabrous or, rarely, sparsely pubescent (versus always pubescent) abaxial leaf blade surfaces. Draba subalpina is known from Garfield, Iron, Kane, and Wayne counties in south-central Utah. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 294. | FNA vol. 7, p. 342. |
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 | |
Name authority | Vahl ex Hornemann: Fors. Oecon. Plantel. ed. 2, 599. (1806) | Goodman & C. L. Hitchcock: Ann. Missouri Bot. Gard. 19: 77. (1932) |
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