Draba aurea |
Draba maguirei |
|
---|---|---|
golden Draba, golden Draba whitlow-grass, golden whitlow-grass, twisted-pod Draba |
Maguire's Draba |
|
Habit | Perennials; (not cespitose); caudex simple or branched; not scapose. | Perennials; (cespitose, forming loose mats); caudex branched (with some persistent leaf bases, branches often creeping, 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, (0.4–)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 (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 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 | 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. |
5–18(–23)-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 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 to ascending or suberect, straight, 3–13(–20) mm, pubescent as stem. |
divaricate-ascending to ascending (not expanded basally), straight, 5–13(–18) 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. |
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 | oblong, 0.9–1.3 × 0.5–0.7 mm. |
ovoid to oblong, 1.6–2 × 1–1.3 mm. |
2n | = 74. |
= 16, 32. |
Draba aurea |
Draba maguirei |
|
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 | Dolomite outcrops, talus, rocky slopes |
Elevation | (0-)700-4200 m ((0-)2300-13800 ft) | 1600-2900 m (5200-9500 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.) |
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. 294. | FNA vol. 7, p. 318. |
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) | C. L. Hitchcock: Revis. Drabas W. N. Amer., 70, plate 5, figs. 37a–c. (1941) |
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