Draba breweri |
Draba aurea |
|
---|---|---|
Brewer's whitlow grass, cushion Draba |
golden Draba, golden Draba whitlow-grass, golden whitlow-grass, twisted-pod Draba |
|
Habit | Perennials; (cespitose, grayish pubescent); caudex branched (sometimes covered with persistent leaf bases, branches short, compact); sometimes scapose. | Perennials; (not cespitose); caudex simple or branched; not scapose. |
Stems | unbranched, (0.1–)0.2–1(–1.5) dm, pubescent throughout, trichomes stalked, 4–10-rayed, 0.1–0.3 mm. |
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. |
Basal leaves | rosulate; petiolate; petiole base ciliate, margin not ciliate, (trichomes simple and 2-rayed, 0.3–0.8 mm); blade oblanceolate to obovate, (0.3–)0.4–1.5(–2.5) cm × 1.5–3(–5) mm, margins usually entire, rarely dentate, surfaces densely pubescent with stalked, 4–10-rayed, stellate trichomes, 0.1–0.2 mm (sometimes 1 or more rays spurred). |
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. |
Cauline leaves | 0–3(–6); sessile; blade oblong or lanceolate to ovate, margins entire (sometimes ciliate at base), surfaces usually pubescent as basal. |
5–20(–26); sessile; blade oblong to lanceolate or ovate, margins entire or dentate, surfaces pubescent as basal, sometimes adaxially with simple trichomes. |
Racemes | (5–)7–18(–24)-flowered, ebracteate, slightly to considerably elongated in fruit; rachis not flexuous, pubescent with stalked, 4–10-rayed trichomes, (0.1–0.3 mm). |
(10–)18–52(–72)-flowered, usually bracteate on proximalmost 1–12(–17) flowers, rarely ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. |
Flowers | sepals (persistent), ovate, 1.2–2 mm, pubescent, (trichomes short-stalked, 2–6-rayed); petals white, spatulate to oblanceolate, 2–3 × 0.7–1.1 mm; anthers ovate, 0.2–0.25 mm. |
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. |
Fruiting pedicels | ascending, (sometimes slightly appressed to rachis), straight, 1.5–3(–4) mm, pubescent as rachis. |
divaricate-ascending to ascending or suberect, straight, 3–13(–20) mm, pubescent as stem. |
Fruits | lanceolate or oblong to linear, usually slightly to strongly twisted, rarely plane, flattened, 3.5–9(–11) × 1.5–2.5 mm; valves pubescent, trichomes short-stalked, 2–5-rayed, 0.05–0.25 mm; ovules 28–40 per ovary; style 0.1–0.3(–0.4) mm. |
(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. |
Seeds | ovoid, 0.5–0.7 × 0.3–0.5 mm. |
oblong, 0.9–1.3 × 0.5–0.7 mm. |
2n | = 32. |
= 74. |
Draba breweri |
Draba aurea |
|
Phenology | Flowering Jul–Aug. | Flowering Jun–Aug. |
Habitat | Rock outcrops, talus, exposed ridges, alpine areas | Rock outcrops, talus, damp gullies and meadows, subalpine conifer woodlands, alpine slopes and turf, tundra, road banks, river gravel |
Elevation | 3100-4100 m (10200-13500 ft) | (0-)700-4200 m ((0-)2300-13800 ft) |
Distribution |
CA
|
AK; AZ; CO; ID; MT; NM; NV; SD; UT; WA; WY; AB; BC; MB; NF; NT; NU; ON; QC; SK; YT; Greenland
|
Discussion | The circumscription of Draba breweri was expanded by R. C. Rollins (1993) to include D. cana. Plants of D. cana differ from those of D. breweri by being non-cespitose (versus cespitose) and taller [(4–)10–30(–38) versus (1–)2–9(–15) cm], and by having basally bracteate (versus ebracteate) racemes, and stems, pedicels, and sepals pubescent with a mixture of simple and branched (versus exclusively branched) trichomes. Draba breweri is known to us from Alpine, Fresno, Inyo, Mono, Plumas, Tulare, and Tuolumne counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 7, p. 297. | FNA vol. 7, p. 294. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. breweri var. sublaxa | 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 | S. Watson: Proc. Amer. Acad. Arts 23: 260. (1888) | Vahl ex Hornemann: Fors. Oecon. Plantel. ed. 2, 599. (1806) |
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