Draba incerta |
Draba zionensis |
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whitlow-wort, Yellowstone Draba, Yellowstone Draba whitlow-wort, Yellowstone whitlow-grass, Yellowstone whitlow-wort |
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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 branched (with persistent leaf bases, branches sometimes terminating in sterile rosettes); 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, 0.5–1.5(–1.8) dm, usually sparsely pubescent proximally, usually glabrous distally, rarely throughout, trichomes simple, 0.3–0.8 mm, often with smaller, 2–4-rayed ones. |
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; shortly petiolate; petiole base sometimes ciliate (margin not ciliate, trichomes simple and 2-rayed, 0.2–0.5 mm); blade spatulate to obovate, 0.7–3.5 cm × 3–10(–12) mm, margins usually entire, rarely obscurely dentate (near apex), surfaces sparsely pubescent with stalked, (2–)4 (or 5)-rayed trichomes, 0.05–0.5 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. |
14–36-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 ovate, 2–3 mm, glabrous or sparsely pubescent, (trichomes simple and short-stalked, 2–4-rayed); petals orange-yellow (fading pale yellow), broadly spatulate to subovate, 5–6 × 1.8–2.8 mm; anthers ovate, 0.4–0.5 mm. |
Fruiting pedicels | ascending, straight, (2.5–)4–11(–27) mm, glabrous or pubescent, trichomes 2–5-rayed or pectinate. |
ascending to divaricate-ascending, straight, (not expanded basally), (4–)5–12(–15) 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. |
lanceolate to linear-lanceolate or ovate, plane (not curved), flattened, 6–12(–17) × 2–3 mm; valves glabrous; ovules 12–20 per ovary; style 0.4–1 mm. |
Seeds | oblong, 1.1–1.5 × 0.7–1 mm. |
oblong, 1–1.3 × 0.6–0.8 mm. |
2n | = 112. |
= 26. |
Draba incerta |
Draba zionensis |
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Phenology | Flowering Jun–Aug. | Flowering Mar–May. |
Habitat | Rock outcrops, talus, gravelly areas, tundra | Sandstone (rarely limestone) rock outcrops and sandy slopes in pinyon-juniper or pine communities |
Elevation | 0-3300 m (0-10800 ft) | 1000-2500 m (3300-8200 ft) |
Distribution |
AK; CO; ID; MT; NV; UT; WA; WY; AB; BC; QC; YT
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UT |
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.) |
R. C. Rollins (1993) treated Draba zionensis as a variety of D. asprella, but its true relationships appear to lie with two other southern Utah endemics, D. sobolifera and D. subalpina. Draba zionensis is easily distinguished from D. subalpina by having orange-yellow (versus white) petals, and from D. asprella and D. sobolifera by its glabrous (versus pubescent) pedicels and stems distally. Nearly all populations of the species are found in and around Zion National Park in southwestern Utah (Iron, Kane, and Washington counties). A specimen supposedly from the Deep Creek Mountains (Juab County) may be mislabeled. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 313. | FNA vol. 7, p. 346. |
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 | D. asprella var. zionensis |
Name authority | Payson: Amer. J. Bot. 4: 261. (1917) | C. L. Hitchcock: Revis. Drabas W. N. Amer., 49, plate 2, fig. 16. (1941) |
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