Draba aurea |
Draba simmonsii |
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golden Draba, golden Draba whitlow-grass, golden whitlow-grass, twisted-pod Draba |
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Habit | Perennials; (not cespitose); caudex simple or branched; not scapose. | Perennials; caudex branched (with persistent leaf bases and petioles); 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, (0.15–)0.3–1.1(–1.3) dm, often pubescent throughout, sometimes sparsely pubescent distally, trichomes stalked, 2–4-rayed, and fewer, simple ones, 0.1–0.3(–0.6) 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. |
(not imbricate); rosulate; petiolate; petiole (base somewhat thickened), margin ciliate, (trichomes simple, 0.5–1 mm); blade oblong to oblong-lanceolate, 0.5–1.6 cm × 2–5 mm, margins entire (apex subacute to obtuse), surfaces pubescent throughout or glabrous adaxially, with simple and stalked, 2–4(–6)-rayed, stellate to subdendritic trichomes. |
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–)4–10(–14)-flowered, ebracteate, slightly elongated in fruit; rachis not flexuous (straight), 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 (purplish green), oblong, (2.5–)2.8–3.5(–3.8) mm, pubescent, (trichomes simple and sometimes short-stalked, 2-rayed); petals pale yellow, narrowly obovate, (sides non-parallel), (3.5–)3.8–5.5(–5.8) × (2.5–)2.8–4(–4.6) mm, (emarginate); anthers ovate, ca. 0.5 mm. |
Fruiting pedicels | divaricate-ascending to ascending or suberect, straight, 3–13(–20) mm, pubescent as stem. |
divaricate, straight, 2.5–10 mm, pubescent as stem. |
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. |
lanceolate, plane, slightly flattened, 5.5–9(–11) × 2.3–3.8 mm; valves pubescent, trichomes simple, sometimes with fewer, 2-rayed ones, 0.1–0.3 mm; ovules 16–24(–28) per ovary; style 0.1–0.3 mm (stigma as wide as style). |
Seeds | oblong, 0.9–1.3 × 0.5–0.7 mm. |
(dark brown), oblong-ovate, 1–1.3 × 0.7–0.8 mm. |
2n | = 74. |
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Draba aurea |
Draba simmonsii |
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Phenology | Flowering Jun–Aug. | Flowering late Jun–Jul. |
Habitat | Rock outcrops, talus, damp gullies and meadows, subalpine conifer woodlands, alpine slopes and turf, tundra, road banks, river gravel | Dry open ground, open patches in meadows or heath vegetation, outwash plains |
Elevation | (0-)700-4200 m ((0-)2300-13800 ft) | 0-100 m (0-300 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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NT; NU |
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.) |
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Source | FNA vol. 7, p. 294. | FNA vol. 7, p. 337. |
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. gracilescens |
Name authority | Vahl ex Hornemann: Fors. Oecon. Plantel. ed. 2, 599. (1806) | Elven & Al-Shehbaz: Novon 18: 326. (2008) |
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