Draba incerta |
Draba subalpina |
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whitlow-wort, Yellowstone Draba, Yellowstone Draba whitlow-wort, Yellowstone whitlow-grass, Yellowstone whitlow-wort |
subalpine Draba |
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Habit | Perennials; (cespitose, often pulvinate); caudex branched (dense with persistent leaf remains, branches sometimes terminating in sterile rosettes); scapose. | Perennials; (cespitose); caudex simple or branched (with some persistent leaf bases); scapose. |
Stems | unbranched, (0.2–)0.4–1.4(–2.1) dm, often pubescent throughout, sometimes glabrous distally, trichomes often simple and 2–5-rayed, 0.1–0.5 mm, (sometimes with mostly subpectinate ones). |
unbranched, 0.3–1(–1.3) dm, often glabrous throughout, sometimes sparsely pubescent proximally, trichomes simple and stalked, 2-rayed, 0.2–1 mm. |
Basal leaves | rosulate; petiolate; petiole (0–1 cm), ciliate throughout; blade narrowly oblanceolate to linear, (0.4–)0.6–1.7(–2.5) cm × (1–)1.5–3.5(–5) mm, margins entire, (ciliate, trichomes usually simple, rarely 2-rayed, 0.2–1.1 mm), surfaces usually pubescent with short-stalked, pectinate trichomes, 0.15–0.5 mm, sometimes also with 4–6-rayed ones, (midvein usually obscure abaxially), sometimes glabrous adaxially. |
rosulate; sessile; blade (fleshy), oblanceolate to linear, (0.4–)0.5–1.4(–2) cm × (1–)1.5–3(–4) mm, margins entire, (ciliate at least apically, trichomes simple and 2-rayed), surfaces usually glabrous, rarely sparsely pubescent with simple and stalked, 2- (or 3-)rayed trichomes, 0.2–1 mm, (midvein obscure). |
Cauline leaves | usually 0 (or 1, as a bract); sessile; blade linear to oblong, margins entire, surfaces pubescent as basal. |
0. |
Racemes | 3–14(–30)-flowered, usually ebracteate, rarely proximalmost flowers bracteate, elongated in fruit; rachis not flexuous, glabrous or pubescent as stem. |
(6–)10–28(–40)-flowered, ebracteate, elongated in fruit; rachis not flexuous, glabrous. |
Flowers | sepals broadly ovate, 2.5–3.5(–4) mm, pubescent, (trichomes simple and 2- or 3-rayed); petals yellow (fading white), oblanceolate to obovate, 4–6 × 1.5–2.5 mm; anthers ovate, 0.3–0.5 mm. |
sepals broadly ovate, 1.7–2.5 mm, usually glabrous, rarely pubescent, (trichomes simple and short-stalked, 2-rayed); petals white, spatulate to obovate, 3–5 × 2–3 mm; anthers oblong, 0.5–0.7 mm. |
Fruiting pedicels | ascending, straight, (2.5–)4–11(–27) mm, glabrous or pubescent, trichomes 2–5-rayed or pectinate. |
divaricate-ascending, straight, (3–)5–10(–17) mm, glabrous. |
Fruits | broadly ovate to lanceolate, plane, flattened, 5–9(–11) × 2–4 mm; valves glabrous or puberulent, trichomes simple and 2-rayed, 0.05–0.3 mm; ovules 8–16(–20) per ovary; style 0.2–0.9 mm. |
ovoid to lanceolate, plane, inflated at least basally, 4–8(–10) × 2.5–4 mm; valves glabrous or sparsely puberulent, trichomes simple, 0.02–0.1 mm; ovules 6–12 per ovary; style 0.2–0.9 mm. |
Seeds | oblong, 1.1–1.5 × 0.7–1 mm. |
ovoid, 1–1.5 × 0.7–1.1 mm. |
2n | = 112. |
= 26. |
Draba incerta |
Draba subalpina |
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Phenology | Flowering Jun–Aug. | Flowering May–Jun. |
Habitat | Rock outcrops, talus, gravelly areas, tundra | Rocky knolls and marly limestone soil in pine-oak-juniper woodlands, edges of spruce-fir forests |
Elevation | 0-3300 m (0-10800 ft) | 1800-3400 m (5900-11200 ft) |
Distribution |
AK; CO; ID; MT; NV; UT; WA; WY; AB; BC; QC; YT
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UT
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Discussion | Draba incerta was shown by G. A. Mulligan (1972) to be sexually reproducing and 14-ploid with x = 8. It is often confused with the apomict D. oligosperma (2n = 32, 64). Draba incerta is readily separated from D. oligosperma by having well-formed (versus abortive) anthers and pollen, stalked (versus sessile) leaf trichomes, and ciliate (versus non-ciliate) basal leaves with obscure (versus prominent) midveins. Although both species have leafless scapes, one often finds a bract adnate to, or subtending, the proximalmost pedicel in D. incerta. Draba incerta is found near sea level in Alaska. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Molecular studies (M. A. Beilstein and M. D. Windham 2003) and chromosomal data (Windham 2000, 2004) suggest that Draba subalpina is most closely related to D. cusickii and D. sobolifera. From those, it is easily distinguished by having white (versus yellow) petals, glabrous (versus pubescent) rachises and stems distally, and glabrous or, rarely, sparsely pubescent (versus always pubescent) abaxial leaf blade surfaces. Draba subalpina is known from Garfield, Iron, Kane, and Wayne counties in south-central Utah. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 313. | FNA vol. 7, p. 342. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. exalata, D. incerta var. laevicapsula, D. incerta var. peasei, D. laevicapsula, D. peasei | |
Name authority | Payson: Amer. J. Bot. 4: 261. (1917) | Goodman & C. L. Hitchcock: Ann. Missouri Bot. Gard. 19: 77. (1932) |
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