Flora of North America species comparison

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Draba alpina

Draba arabisans

alpine Draba

rock Draba, rock whitlow-mustard
Habit Perennials; (cespitose); caudex branched (covered with persistent leaves or leaf remains); scapose. Perennials; (sometimes cespitose); caudex simple or branched; not 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.

branched or unbranched, (0.5–)0.7–3(–4.5) dm, pubescent proximally, glabrous or pubescent distally, trichomes sessile (non-crisped), 4- or 5-rayed, stellate, or subpectinate, 0.07–0.4 mm.
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; petiolate;

petiole base and margin sparsely ciliate, (trichomes simple and 2-rayed, 0.2–0.8 mm);

blade oblanceolate to spatulate or linear-oblanceolate, 1–3.8(–5) cm × 2–5(–8) mm, margins dentate or denticulate, surfaces pubescent with sessile, non-crisped, 4- or 5-rayed, stellate trichomes, 0.07–0.5mm, (some rays branched, appearing 2–12-rayed, midvein obscure abaxially).
Cauline leaves

0.

(2 or) 3–10(–13);

sessile;

blade ovate to oblong, margins dentate to subentire, surfaces pubescent as basal.
Racemes

6–18-flowered, ebracteate, considerably elongated in fruit;

rachis not flexuous, pubescent as stem.

5–18(–25)-flowered, ebracteate, elongated in fruit;

rachis not flexuous, glabrous or pubescent as stem.
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 oblong, 1.7–2.5 mm, pubescent, trichomes short-stalked, 3- or 4-rayed;

petals white, broadly obovate, 3.5–5 × 1.5–2.5 mm;

anthers ovate, 0.4–0.5 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 to suberect, straight or slightly curved, (3–)4–10(–13) mm, glabrous or pubescent as stem.
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 lanceolate or linear-lanceolate, usually slightly twisted, rarely plane, flattened, 5–11(–14) × 2–3.5 mm;

valves usually glabrous, rarely pubescent, trichomes 3- or 4-rayed, 0.07–0.2 mm;

ovules 20–28(–32) per ovary;

style (0.2–)0.4–1 mm.
Seeds

(pale brown), ovoid, 0.9–1.3 × 0.6–0.9 mm.

oblong, 0.8–1.1 × 0.6–0.8 mm.
2n

= 80.

= 96.

Draba alpina

Draba arabisans
Phenology Flowering Jun–Aug. Flowering Jun–Aug.
Habitat Moist tundra and ridges, sand and gravel flats or beaches Rock outcrops and talus (usually limestone or dolomite), open woods, rocky shores
Elevation 0-1000 m (0-3300 ft) 0-300 m (0-1000 ft)
Distribution
from FNA
LB; MB; NU; ON; QC; Greenland; Europe (Finland, Norway, Russia, Sweden)
[WildflowerSearch map]
[BONAP county map]
from FNA
ME; MI; MN; NY; VT; WI; MB; NB; NF; NS; ON; QC
[WildflowerSearch map]
[BONAP county map]
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.)

Draba arabisans is often confused with D. glabella (2n = 80); it is easily distinguished by having sessile (versus short-stalked) stellate trichomes on abaxial leaf blade surfaces and longer styles (0.2–)0.4–1 [versus 0.1–0.2(–0.4)] mm. Both species have twisted and plane fruits; D. arabisans has mostly twisted fruits; D. glabella has predominantly plane fruits. The complete absence of simple trichomes proximally on stems of D. arabisans can be a useful feature separating it from D. glabella, which often has at least some simple trichomes on the proximal half of the stem.

Draba arabis Persoon is an illegitimate name, sometimes found in synonymy with D. arabisans.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 7, p. 290. FNA vol. 7, p. 291.
Parent taxa Brassicaceae > tribe Arabideae > Draba Brassicaceae > tribe Arabideae > Draba
Sibling taxa
D. abajoensis, D. albertina, D. aleutica, D. aprica, D. arabisans, D. arctica, D. arctogena, D. argyrea, D. arida, D. asprella, D. asterophora, D. aurea, D. aureola, D. bifurcata, D. borealis, D. brachycarpa, D. brachystylis, D. breweri, D. burkei, D. californica, D. cana, D. carnosula, D. chamissonis, D. cinerea, D. corrugata, D. corymbosa, D. crassa, D. crassifolia, D. cruciata, D. cuneifolia, D. cusickii, D. cyclomorpha, D. daviesiae, D. densifolia, D. exunguiculata, D. fladnizensis, D. glabella, D. globosa, D. graminea, D. grandis, D. grayana, D. heilii, D. helleriana, D. hitchcockii, D. howellii, D. incana, D. incerta, D. incrassata, D. inexpectata, D. jaegeri, D. juvenilis, D. kassii, D. kluanei, D. lactea, D. lemmonii, D. lonchocarpa, D. longisquamosa, D. macounii, D. maguirei, D. malpighiacea, D. micropetala, D. mogollonica, D. monoensis, D. mulliganii, D. murrayi, D. nemorosa, D. nivalis, D. norvegica, D. novolympica, D. oblongata, D. ogilviensis, D. oligosperma, D. oreibata, D. oxycarpa, D. palanderiana, D. pauciflora, D. paucifructa, D. paysonii, D. pectinipila, D. pedicellata, D. pennellii, D. petrophila, D. pilosa, D. platycarpa, D. porsildii, D. praealta, D. pterosperma, D. ramosissima, D. ramulosa, D. rectifructa, D. reptans, D. ruaxes, D. santaquinensis, D. saxosa, D. scotteri, D. serpentina, D. sharsmithii, D. sibirica, D. sierrae, D. simmonsii, D. smithii, D. sobolifera, D. spectabilis, D. sphaerocarpa, D. sphaeroides, D. standleyi, D. stenoloba, D. stenopetala, D. streptobrachia, D. streptocarpa, D. subalpina, D. subcapitata, D. subumbellata, D. trichocarpa, D. ventosa, D. verna, D. viridis, D. weberi, D. yukonensis, D. zionensis
D. abajoensis, D. albertina, D. aleutica, D. alpina, D. aprica, D. arctica, D. arctogena, D. argyrea, D. arida, D. asprella, D. asterophora, D. aurea, D. aureola, D. bifurcata, D. borealis, D. brachycarpa, D. brachystylis, D. breweri, D. burkei, D. californica, D. cana, D. carnosula, D. chamissonis, D. cinerea, D. corrugata, D. corymbosa, D. crassa, D. crassifolia, D. cruciata, D. cuneifolia, D. cusickii, D. cyclomorpha, D. daviesiae, D. densifolia, D. exunguiculata, D. fladnizensis, D. glabella, D. globosa, D. graminea, D. grandis, D. grayana, D. heilii, D. helleriana, D. hitchcockii, D. howellii, D. incana, D. incerta, D. incrassata, D. inexpectata, D. jaegeri, D. juvenilis, D. kassii, D. kluanei, D. lactea, D. lemmonii, D. lonchocarpa, D. longisquamosa, D. macounii, D. maguirei, D. malpighiacea, D. micropetala, D. mogollonica, D. monoensis, D. mulliganii, D. murrayi, D. nemorosa, D. nivalis, D. norvegica, D. novolympica, D. oblongata, D. ogilviensis, D. oligosperma, D. oreibata, D. oxycarpa, D. palanderiana, D. pauciflora, D. paucifructa, D. paysonii, D. pectinipila, D. pedicellata, D. pennellii, D. petrophila, D. pilosa, D. platycarpa, D. porsildii, D. praealta, D. pterosperma, D. ramosissima, D. ramulosa, D. rectifructa, D. reptans, D. ruaxes, D. santaquinensis, D. saxosa, D. scotteri, D. serpentina, D. sharsmithii, D. sibirica, D. sierrae, D. simmonsii, D. smithii, D. sobolifera, D. spectabilis, D. sphaerocarpa, D. sphaeroides, D. standleyi, D. stenoloba, D. stenopetala, D. streptobrachia, D. streptocarpa, D. subalpina, D. subcapitata, D. subumbellata, D. trichocarpa, D. ventosa, D. verna, D. viridis, D. weberi, D. yukonensis, D. zionensis
Synonyms D. alpina var. hydeana, D. alpina var. inflatisiliqua D. arabisans var. superiorensis, D. incana var. arabisans, D. incana var. glabriuscula
Name authority Linnaeus: Sp. Pl. 2: 642. (1753) Michaux: Fl. Bor.-Amer. 2: 28. (1803)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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