Draba aurea |
Draba saxosa |
|
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golden Draba, golden Draba whitlow-grass, golden whitlow-grass, twisted-pod Draba |
Southern California Rock Draba |
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Habit | Perennials; (not cespitose); caudex simple or branched; not scapose. | Perennials; (cespitose); caudex branched (covered with persistent leaves); 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, 0.5–1.5 dm, pubescent throughout, trichomes simple and long-stalked, 2-rayed, 0.3–1 mm, with smaller, 2–4-rayed ones, 0.1–0.5 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; petiolate; petiole base and margin ciliate, (trichomes simple, 0.5–1.2 mm); blade oblanceolate, 1–3.1 cm × 2–7 mm, margins entire, surfaces densely pubescent, abaxially with stalked, (2–)4-rayed trichomes, 0.2–0.8 mm, adaxially mostly with long-stalked, 2-rayed trichomes, 0.6–1.3 mm, sometimes with simple and 3- or 4-rayed ones. |
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 (or 1); sessile; blade oblong, margins entire, surfaces pubescent as basal. |
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. |
12–43-flowered, ebracteate, 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 oblong, 2–2.5 mm, pubescent, (trichomes short-stalked, 2–4-rayed); petals yellow, linear-oblanceolate, 3–3.5 × 0.5–1 mm; anthers oblong, 0.5–0.6 mm, (exserted). |
Fruiting pedicels | divaricate-ascending to ascending or suberect, straight, 3–13(–20) mm, pubescent as stem. |
divaricate to ascending, straight or curved, (6–)10–17 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. |
oblong to linear-oblong, slightly twisted or plane, flattened, 6–10 × 2.5–4 mm; valves pubescent, trichomes short-stalked, cruciform, 0.07–0.25 mm, sometimes with fewer, 2- or 3-rayed ones; ovules 8–24 per ovary; style (0.8–)1.2–3.5 mm. |
Seeds | oblong, 0.9–1.3 × 0.5–0.7 mm. |
oblong, 1–1.2 × 0.6–0.8 mm. |
2n | = 74. |
|
Draba aurea |
Draba saxosa |
|
Phenology | Flowering Jun–Aug. | Flowering Jun–Jul. |
Habitat | Rock outcrops, talus, damp gullies and meadows, subalpine conifer woodlands, alpine slopes and turf, tundra, road banks, river gravel | Among rocks |
Elevation | (0-)700-4200 m ((0-)2300-13800 ft) | 2600-3300 m (8500-10800 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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CA |
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 saxosa is related to D. corrugata and is often considered a variety of that species. The two taxa are easily distinguished (I. A. Al-Shehbaz and M. D. Windham 2007) and the available data support their recognition as distinct species. Draba saxosa is restricted to the San Jacinto and Santa Rosa mountains in southern California (Riverside and San Diego counties). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 294. | FNA vol. 7, p. 335. |
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. corrugata var. saxosa |
Name authority | Vahl ex Hornemann: Fors. Oecon. Plantel. ed. 2, 599. (1806) | Davidson: Bull. S. Calif. Acad. Sci. 19: 11. (1920) |
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