Draba santaquinensis |
Draba aurea |
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golden Draba, golden Draba whitlow-grass, golden whitlow-grass, twisted-pod Draba |
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Habit | Biennials or perennials; (short-lived); caudex simple (poorly developed, without persistent leaf bases); not scapose. | Perennials; (not cespitose); caudex simple or branched; not scapose. |
Stems | usually branched, 1.1–3.4 dm, hirsute proximally, trichomes mostly simple and 2-rayed, 0.2–1.5 mm, pubescent distally, trichomes mostly 2- or 3-rayed, 0.2–1 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; petiole (obscure), ciliate, (trichomes simple and 2-rayed); blade obovate to oblanceolate, 1.6–2.5 cm × 5–10 mm, margins usually entire, rarely denticulate, surfaces pubescent, abaxially with stalked, mostly cruciform trichomes, 0.5–1 mm, adaxially with simple and stalked, 2–4-rayed ones. |
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 | usually 1–5; sessile or subsessile; blade oblanceolate to oblong, margins often denticulate, (ciliate proximally, with 2- or 3-rayed trichomes). |
5–20(–26); sessile; blade oblong to lanceolate or ovate, margins entire or dentate, surfaces pubescent as basal, sometimes adaxially with simple trichomes. |
Racemes | 9–25-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent, trichomes 2- or 3-rayed. |
(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 oblong-obovate, 2–3.5 mm, pubescent, (trichomes short- to long-stalked, 2–4-rayed, 0.2–0.8 mm); petals yellow (often fading whitish), oblanceolate, 3–5 × 1–1.5 mm; anthers ovate, 0.4–0.5 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 | horizontal to divaricate-ascending, usually straight, rarely curved upward, 7–10 mm, pubescent, trichomes 2- or 3-rayed. |
divaricate-ascending to ascending or suberect, straight, 3–13(–20) mm, pubescent as stem. |
Fruits | narrowly elliptic to slightly falcate, plane, flattened, (7–)10–16 × (2–)2.5–3.7 mm; valves pubescent, trichomes short-stalked, 2–4-rayed, 0.2–0.5 mm; ovules 14–22 per ovary; style 0.9–1.2 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 | oblong, 1.1–1.5 × 0.7–0.9 mm. |
oblong, 0.9–1.3 × 0.5–0.7 mm. |
2n | = 20. |
= 74. |
Draba santaquinensis |
Draba aurea |
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Phenology | Flowering late Apr-early Jun. | Flowering Jun–Aug. |
Habitat | Limestone outcrops and rocky slopes in mixed conifer communities | Rock outcrops, talus, damp gullies and meadows, subalpine conifer woodlands, alpine slopes and turf, tundra, road banks, river gravel |
Elevation | 1800-2400 m (5900-7900 ft) | (0-)700-4200 m ((0-)2300-13800 ft) |
Distribution |
UT |
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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Discussion | Although Draba santaquinensis was included within D. brachystylis by previous authors, I. A. Al-Shehbaz and M. D. Windham (2007) have shown that it is distinct both morphologically and chromosomally. It is currently known only from Utah County (American Fork, Provo, and Santaquin canyons) in north-central Utah. (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. 334. | FNA vol. 7, p. 294. |
Parent taxa | ||
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 | Windham & Allphin: Harvard Pap. Bot. 12: 410. (2007) | Vahl ex Hornemann: Fors. Oecon. Plantel. ed. 2, 599. (1806) |
Web links |