Draba alpina |
Draba porsildii |
|
---|---|---|
alpine Draba |
Porsild's Draba, Porsild's whitlow-grass |
|
Habit | Perennials; (cespitose); caudex branched (covered with persistent leaves or leaf remains); scapose. | Perennials; (cespitose); caudex branched (with persistent leaf remains); often scapose. |
Stems | unbranched, (0.3–)0.5–1.7(–2.8) dm, pubescent throughout, trichomes simple and 2-rayed, 0.3–0.8 mm, with 3–5-rayed ones, 0.1–0.3 mm. |
unbranched, 0.2–1.2 dm, sparsely pubescent proximally, trichomes short-stalked, 3–5- rayed, (non-crisped), 0.2–0.4 mm, glabrous distally. |
Basal leaves | rosulate; petiolate; petiole base (not thickened), ciliate, (trichomes simple, 0.3–1 mm); blade oblanceolate to obovate or lanceolate to oblong, 0.8–3(–4.5) cm × 2.5–6(–9) mm, margins entire, surfaces abaxially pubescent with stalked, 2–4-rayed trichomes, 0.1–0.5 mm, with simple ones (midvein obscure, not thickened), adaxially glabrous or sparsely pubescent with simple and stalked, 2–4-rayed trichomes. |
rosulate; subsessile or shortly petiolate; petiole base and margin ciliate proximally, (trichomes simple, subsetiform, stiff, 0.3–0.9 mm); blade oblanceolate to obovate, 0.4–1.5 cm × 1–3 mm, margins entire, surfaces pubescent, abaxially with stalked, 6–12-rayed, (non-crisped) trichomes, 0.2–0.5 mm, (midvein obscure), adaxially similar, or with simple trichomes on proximal 1/2. |
Cauline leaves | 0. |
0 or 1; sessile; blade oblong to lanceolate, margins entire, surfaces pubescent as basal. |
Racemes | 6–18-flowered, ebracteate, considerably elongated in fruit; rachis not flexuous, pubescent as stem. |
3–13-flowered, ebracteate, elongated in fruit; rachis not flexuous, glabrous. |
Flowers | sepals (purplish tinged), narrowly ovate, 2.5–3 mm, pubescent, (trichomes simple and fewer, stalked, 2-rayed); petals bright yellow, narrowly obovate, 3.5–5 × 1.7–2.5 mm; anthers ovate, 0.3–0.4 mm. |
sepals ovate, 1.5–2 mm, pubescent, (trichomes simple and 2-rayed); petals white, spatulate, 2–4 × 1–1.7 mm; anthers ovate, ca. 0.2 mm. |
Fruiting pedicels | ascending to divaricate-ascending, straight or, sometimes, slightly curved upwards, 4–14(–30) mm, pubescent, trichomes simple and 2–4-rayed. |
divaricate-ascending, straight, 1–4(–8) mm, glabrous. |
Fruits | elliptic, plane, flattened, 6–10 × 2–3 mm; valves glabrous or glabrescent, trichomes simple, (not confined to replum); ovules 12–24 per ovary; style 0.2–0.3 mm (stigma about as wide as style). |
ovate to oblong, plane, flattened, 4–7.5 × 1.7–3 mm; valves glabrous; ovules 12–16 per ovary; style 0.1–0.3(–0.5) mm. |
Seeds | (pale brown), ovoid, 0.9–1.3 × 0.6–0.9 mm. |
ovoid, 0.7–1 × 0.5–0.6 mm. |
2n | = 80. |
= 32. |
Draba alpina |
Draba porsildii |
|
Phenology | Flowering Jun–Aug. | Flowering Jun–Jul. |
Habitat | Moist tundra and ridges, sand and gravel flats or beaches | Rock outcrops, talus, meadows, gravel slopes |
Elevation | 0-1000 m (0-3300 ft) | 600-3000 m (2000-9800 ft) |
Distribution |
LB; MB; NU; ON; QC; Greenland; Europe (Finland, Norway, Russia, Sweden)
|
AK; MT; WY; AB; YT |
Discussion | The synonymy above includes two North American names overlooked by C. L. Hitchcock (1941) and R. C. Rollins (1993). Draba alpina was broadly delimited by O. E. Schulz (1927) and included 17 varieties, some of which (e.g., corymbosa, oxycarpa, pilosa) are recognized herein as distinct species. The name D. alpina was so misapplied that it was used for any circumpolar or alpine, scapose, yellow-flowered, perennial Draba. Various chromosome numbers (e.g., 2n = 64, 80, 112, 120; S. I. Warwick and I. A. Al-Shehbaz 2006) have been reported for the species. As circumscribed here, it has the narrow distribution outlined above and includes plants with 2n = 80. Reports of the species from Alaska, Canadian Northwest Territories and Yukon, Siberia, eastern Asia, Russian Far East, and the Central Asian republics are either suspect or very unlikely. The entire D. alpina complex (including the above three species, D. glacialis Adams, D. macounii, etc.) is in need of critical molecular, cytological, and morphological study. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
According to H. H. Grundt et al. (2004), tetraploid Draba porsildii probably originated from a diploid ancestor such as D. lonchocarpa. The Wyoming plants are a close match to the type of the species, though they have distinctly shorter pedicels. Some of the Alaskan plants are more problematic; they have finer and more branched trichomes, larger flowers, longer pedicels, and longer styles than the type. It is likely that they belong to another species; detailed molecular and cytological studies on this complex are needed before any meaningful conclusions are reached. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 290. | FNA vol. 7, p. 331. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. alpina var. hydeana, D. alpina var. inflatisiliqua | D. nivalis var. brevicula, D. porsildii var. brevicula |
Name authority | Linnaeus: Sp. Pl. 2: 642. (1753) | G. A. Mulligan: Canad. J. Bot. 52: 1795, fig. 8. (1974) |
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