Flora of North America species comparison

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Draba glabella

Draba standleyi

golden Draba, rock whitlow-grass, smooth Draba, smooth whitlow-grass, smooth whitlow-mustard

Standley's Draba
Habit Perennials; (sometimes cespitose); caudex simple or branched; not scapose. Perennials; (densely pulvinate); caudex branched (with persistent, thickened petioles, branches compact); not scapose.
Stems

branched or unbranched, (0.4–)1–3.5(–4.7) dm, often pubescent throughout (sometimes sparsely so distally), sometimes glabrous, trichomes simple and 2-rayed, (non-crisped), 0.2–1 mm, or subsessile, stellate-pectinate, and 3–8-rayed, 0.1–0.3 mm.

unbranched, 0.3–1.3(–1.7) dm, usually glabrous throughout or sparsely pubescent proximally, rarely sparsely pubescent distally, trichomes simple and 2-rayed, 0.1–0.7 mm.
Basal leaves

rosulate; petiolate;

petiole ciliate, (trichomes simple, 0.1–0.8 mm);

blade oblanceolate to spatulate or linear-oblanceolate, (0.6–)1–3.5(–5) cm × 2–8(–10) mm, margins dentate or denticulate, (pubescent as petiole), surfaces pubescent with non-crisped, minutely stalked, 4–8(–12)-rayed, stellate-pectinate trichomes, 0.15–0.6 mm, (midvein obscure abaxially), adaxially sometimes also with simple trichomes, or glabrous.

(not imbricate); rosulate; petiolate;

petiole ciliate, (trichomes usually simple, rarely 2-rayed, not setiform);

blade narrowly oblanceolate to linear-lanceolate, (strongly differentiated into blade and petiole), (1.2–)1.8–6(–8.5) cm × 1–5(–7) mm, margins entire or sparsely denticulate, (ciliate as petiole; midvein not prominent), surfaces glabrous or pubescent, usually with simple trichomes 0.1–0.8 mm, rarely 2-rayed.
Cauline leaves

2–17(–25);

sessile;

blade ovate to oblong, margins dentate to subentire, surfaces often pubescent as basal, or predominantly with simple trichomes adaxially.

1–8;

sessile;

blade lanceolate to narrowly oblong, margins usually entire, surfaces pubescent as basal.
Racemes

(5–)8–26(–34)-flowered, ebracteate or proximalmost 1 or 2 flowers bracteate, elongated in fruit;

rachis not flexuous, usually glabrous, rarely pubescent as stem.

5–17(–23)-flowered, ebracteate, elongated in fruit;

rachis not flexuous, usually glabrous, rarely pubescent, trichomes simple and 2-rayed, (non-crisped).
Flowers

sepals oblong, 2–3.5 mm, pubescent, (trichomes simple and short-stalked, 2–4-rayed);

petals white, broadly obovate, 4–5.5 × 1.5–3 mm;

anthers ovate, 0.3–0.5 mm.

sepals ovate, 2–2.5 mm, pubescent, (trichomes simple);

petals yellow, oblanceolate, 4–6 × 1.5–2 mm;

anthers oblong, 0.6–0.8 mm.
Fruiting pedicels

divaricate-ascending to suberect, straight, (1–)3–10(–16) mm, glabrous or pubescent as stem.

divaricate-ascending or ascending, straight, 3–9(–13) mm, usually glabrous, rarely sparsely pubescent, trichomes simple.
Fruits

oblong to ovate or ovoid to lanceolate or linear-lanceolate, usually plane, rarely slightly twisted, flattened or inflated, (3–)5–12(–16) × 2–3.5 mm;

valves glabrous or pubescent, trichomes simple or 2–4-rayed, 0.05–0.2(–0.4) mm;

ovules (20–)24–36 per ovary;

style 0.05–0.2(–0.5) mm.

linear-elliptic to elliptic, twisted or plane, flattened, 5–10(–13) × 1.5–2.5 mm;

valves usually glabrous, rarely puberulent, trichomes simple, 0.05–0.1 mm;

ovules 12–24 per ovary;

style 0.7–1.4(–1.8) mm.
Seeds

oblong, 0.9–1.1 × 0.5–0.7 mm.

ovoid, 1–1.2 × 0.7–0.8 mm.
2n

= 64, 80.

Draba glabella

Draba standleyi
Phenology Flowering May–Aug. Flowering Jun–Aug.
Habitat Rock outcrops, talus, rocky ridges and knolls, meadows, tundra, gravelly beaches sandy river margins, disturbed soils Igneous rock outcrops, stabilized talus slopes
Elevation 0-1400 m (0-4600 ft) 1800-3100 m (5900-10200 ft)
Distribution
from FNA
AK; ME; VT; WI; BC; MB; NB; NL; NS; NT; NU; ON; QC; YT; Greenland; n Europe (n Russia); e Asia (Russian Far East, Siberia)
[BONAP county map]
from FNA
AZ; NM; TX
[BONAP county map]
Discussion

Draba glabella was reported by J. V. Freudenstein and J. K. Marr (1986) from Michigan, but that record likely was based on plants of D. arabisans, a highly variable species that occurs in that state.

Draba glabella is extremely variable in indumentum, number of cauline leaves, fruiting pedicel length, fruit shape and size, style length, and seed number. M. L. Fernald (1934) divided it into five species and three varieties; R. C. Rollins (1993) recognized three species. Of these, G. A. Mulligan (1970, 1976) reduced D. laurentiana to synonymy of D. glabella and treated D. pycnosperma as a variety. Of all the segregates of D. glabella, var. pycnosperma might merit recognition. It is restricted to northwestern Newfoundland and northeastern Quebec, where var. glabella also grows. The main difference between the two varieties is the presence in var. pycnosperma of plump (versus flattened), ovoid to oblong fruits. Draba sornborgeri, recognized by Rollins as a distinct species, is merely a glabrescent form of D. glabella. Because of the tremendous morphological variability, wide distribution, extensive synonymy, and different chromosome numbers, D. glabella will require extensive molecular, cytological, and morphological studies to properly delimit the species and any potential infraspecific taxa.

Some forms of Draba glabella approach both D. borealis and D. praealta, but these can be distinguished by examining the trichomes on the abaxial surfaces of basal leaf blades. In D. glabella, these trichomes are minutely stalked or subsessile and have branched rays. In the other two species, the trichomes have long stalks and the rays are always unbranched.

The Linnaean name Draba hirta was applied to this species previously, and still is in Russia. The name is not typified, and the material at LINN is in bad condition and probably belongs to two species, D. glabella and D. norvegica, as recognized here. A typification of D. hirta may necessitate its re-introduction for this species.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Of conservation concern.

Draba standleyi is a distinctive species that is sporadically distributed in the mountains of southwestern United States. It is known from the Chiricahua Mountains (Cochise County, southeastern Arizona), the Organ Mountains and Black Range (Dona Ana and Sierra counties, south-central New Mexico), and the Davis Mountains (Jeff Davis County, western Texas). It has not been reported from Mexico, though it is very likely to occur there.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 7, p. 307. FNA vol. 7, p. 340.
Parent taxa Brassicaceae > tribe Arabideae > Draba Brassicaceae > tribe Arabideae > Draba
Sibling taxa
D. abajoensis, D. albertina, D. aleutica, D. alpina, 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. 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. 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. 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. arabisans var. canadensis, D. arabisans var. orthocarpa, D. canadensis, D. canadensis var. pycnosperma, D. daurica, D. glabella var. megasperma, D. glabella var. orthocarpa, D. glabella var. pycnosperma, D. henneana, D. hirta var. laurentiana, D. hirta var. pycnosperma, D. laurentiana, D. megasperma, D. norvegica var. pleiophylla, D. pycnosperma, D. sornborgeri D. gilgiana, D. chrysantha var. gilgiana
Name authority Pursh: Fl. Amer. Sept. 2: 434. (1813) J. F. Macbride & Payson: Ann. Missouri Bot. Gard. 5: 150. (1918)
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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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