Draba aurea |
Draba burkei |
|
---|---|---|
golden Draba, golden Draba whitlow-grass, golden whitlow-grass, twisted-pod Draba |
snowbasin Draba |
|
Habit | Perennials; (not cespitose); caudex simple or branched; not scapose. | Perennials; (cespitose, forming loose mats); caudex branched (with persistent leaves, 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, 0.3–0.6(–0.9) dm, glabrous. |
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. |
subrosulate; subsessile; blade oblanceolate to obovate, 0.3–0.8(–1.3) cm × 1–2.5 mm, margins entire, (ciliate, trichomes simple, subsetiform, 0.25–0.8 mm), surfaces glabrous. |
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. |
4–10-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, 2–3.5 mm, glabrous or sparsely pubescent, (trichomes simple, 0.07–0.35 mm); petals yellow, oblanceolate, 4–6 × 1.5–2 mm; anthers ovate, 0.4–0.5 mm. |
Fruiting pedicels | divaricate-ascending to ascending or suberect, straight, 3–13(–20) mm, pubescent as stem. |
divaricate-ascending to ascending, straight, 4–9(–15) 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. |
ovate, plane, flattened, 3–5.5 × 2–3.2 mm; valves glabrous or puberulent, trichomes simple, 0.02–0.08 mm; ovules 4–10 per ovary; style 0.5–1.7 mm. |
Seeds | oblong, 0.9–1.3 × 0.5–0.7 mm. |
ovoid, 1–1.4 × 0.7–1 mm. |
2n | = 74. |
= 20. |
Draba aurea |
Draba burkei |
|
Phenology | Flowering Jun–Aug. | Flowering May–Jul. |
Habitat | Rock outcrops, talus, damp gullies and meadows, subalpine conifer woodlands, alpine slopes and turf, tundra, road banks, river gravel | Rocky ridges, steep talus slopes, rock outcrops and crevices |
Elevation | (0-)700-4200 m ((0-)2300-13800 ft) | 1600-3000 m (5200-9800 ft) |
Distribution |
AK; AZ; CO; ID; MT; NM; NV; SD; UT; WA; WY; AB; BC; MB; NF; NT; NU; ON; QC; SK; YT; Greenland
|
UT |
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.) |
Of conservation concern. Draba burkei was treated by C. L. Hitchcock (1941) and R. C. Rollins (1993) as a variety of D. maguirei. Chromosome numbers (2n = 20 versus 2n = 32), plant morphology, and molecular data support the recognition of these taxa as independent species (M. D. Windham 2004). Draba burkei is easily distinguished from D. maguirei by having exclusively simple trichomes confined to leaf blade margins (versus mostly branched trichomes on margins and surfaces) and smaller seeds (1–1.4 × 0.7–1 versus 1.6–2 × 1–1.3 mm). It is known from Box Elder, Cache, Morgan, and Weber counties, where it approaches but does not overlap the range of D. maguirei. Draba burkei (as D. maguirei var. burkei) is in the Center for Plant Conservation’s National Collection of Endangered Plants and is listed in NatureServe as a plant of conservation concern. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 294. | FNA vol. 7, p. 298. |
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. maguirei var. burkei |
Name authority | Vahl ex Hornemann: Fors. Oecon. Plantel. ed. 2, 599. (1806) | (C. L. Hitchcock) Windham & Beilstein: Madroño 50: 221. (2004) |
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