Flora of North America species comparison

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Descurainia longepedicellata

Descurainia nelsonii

mountain tansymustard, narrow tansymustard, sticky tansymustard, western tansy-mustard

Nelson's tansy-mustard, sagebrush tansymustard
Habit Annuals; usually eglandular, rarely glandular; moderately to sparsely pubescent, often glabrous distally, not canescent, trichomes dendritic. Annuals; eglandular; sparsely to moderately pubescent, sometimes glabrous distally, not canescent, trichomes dendritic.
Stems

erect, unbranched or branched proximally, often branched distally, (1.5–)3–6.2(–8.5) dm.

erect, usually branched basally or slightly distally, rarely unbranched, (0.7–)0.9–3.2(–4.5) dm.
Basal leaves

petiole 0.4–3.5 cm;

blade pinnate, ovate to oblanceolate in outline, 1.5–7 cm, lateral lobes linear or oblong, margins entire or dentate to incised.

petiole 0.5–1.5 cm;

blade pinnate, ovate or oblong in outline, 0.8–2.5 cm, lateral lobe (2–5 pairs), margins dentate or entire.
Cauline leaves

sessile or shortly petiolate;

blade smaller distally, lobes linear to filiform, margins entire, surfaces usually glabrous, rarely pubescent.

sessile or shortly petiolate;

blade smaller distally, distal lobes often narrower, sparsely to moderately pubescent.
Racemes

considerably elongated in fruit.

considerably elongated in fruit.
Flowers

sepals ascending, yellow, oblong, 1.5–2 mm, glabrous;

petals narrowly oblanceolate, 1.7–2.6 cm × 0.5–1 mm;

median filaments 1.5–2 mm;

anthers 0.3–0.4 mm.

sepals ascending, yellowish, oblong, 0.7–1.2 mm, pubescent;

petals narrowly oblanceolate, 0.8–1.2 × 0.2–0.4 mm;

median filaments 1–1.5 mm;

anthers 0.1–0.2 mm.
Fruiting pedicels

horizontal to divaricate, straight, (8–)10–15(–20) mm.

divaricate-ascending (often at 20–45º angle), straight, (1.5–)2.5–7(–10) mm.
Fruits

erect, linear, not torulose, (9–)12–17 × 0.8–1.1 mm, (straight or slightly curved inward);

valves each with obscure midvein;

septum not veined;

ovules 18–32 per ovary;

style 0.1–0.2 mm, glabrous.

erect or ascending, linear, not or slightly torulose, (0.4–)5–8(–10) × 0.7–1 mm;

valves each with distinct midvein;

septum not veined;

ovules 6–12 per ovary;

style 0.1–0.2 mm, glabrous.
Seeds

uniseriate, reddish brown, oblong, 1–1.3 × 0.6–0.7 mm.

uniseriate, brown, oblong, 0.6–0.8 × 0.4–0.5 mm.
2n

= 14.

= 14.

Descurainia longepedicellata

Descurainia nelsonii
Phenology Flowering Apr–Jul. Flowering late May-mid Jul.
Habitat Sandy plains and banks, dry washes, open hillsides, sagebrush and juniper or pine communities, grasslands Roadsides, sagebrush, wash bottoms, silty flats, gravelly grounds
Elevation 200-2100 m (700-6900 ft) 800-3000 m (2600-9800 ft)
Distribution
from FNA
AZ; CO; ID; MT; NV; OR; UT; WA; WY; BC
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; MT; NV; OR; WA; WY; BC
[WildflowerSearch map]
[BONAP county map]
Discussion

L. E. Detling (1939) treated Descurainia longepedicellata as subsp. filipes of D. pinnata, whereas R. C. Rollins (1993) and N. H. Holmgren (2005b) treated it as a subspecies and variety, respectively, of D. incisa. Molecular data, both nuclear and plastidic (B. E. Goodson 2007), place the three taxa in different, well-supported clades.

R. C. Rollins (1993) and N. H. Holmgren (2005b) reported 2n = 28 and 42 for Descurainia longepedicellata (as D. pinnata var. filipes), but these counts are not vouchered. Rollins indicated that the taxon range extends into California and New Mexico; we have not seen material from those states.

Descurainia longepedicellata resembles D. incisa subsp. paysonii in having long fruiting pedicels and linear leaf lobes with entire margins. The latter is easily distinguished by being canescent (versus not canescent) and having fruits strongly curved inward (versus straight). Because the two taxa are not closely related (B. E. Goodson 2007), the similarities in fruiting pedicels and distalmost leaf segments represent convergence.

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

Descurainia nelsonii was treated by L. E. Detling (1939) and R. C. Rollins (1993) as a subspecies of D. pinnata, but the latter in the sense of these authors is not monophyletic, comprising instead either four or two unrelated species, respectively. ITS molecular data (B. E. Goodson 2007) suggest that D. nelsonii is most closely related to D. longepedicellata and D. paradisa. It can be distinguished from the latter species by its linear fruits with cuneate tips; D. paradisa has obovoid fruits with rounded tips. Descurainia nelsonii resembles D. pinnata subsp. brachycarpa in the orientation of fruiting pedicels and in having short styles (to 0.3 mm) and small seeds (to 1 × 0.5 mm). It differs in being branched (versus simple) at base and in having smaller flowers (petals 0.7–1 versus 1.5–2.6 mm), fewer ovules (6–12 versus 16–40) per ovary, linear (versus subclavate) fruits, and uniseriate (versus biseriate) seeds.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 7, p. 524. FNA vol. 7, p. 525.
Parent taxa Brassicaceae > tribe Descurainieae > Descurainia Brassicaceae > tribe Descurainieae > Descurainia
Sibling taxa
D. adenophora, D. brevisiliqua, D. californica, D. incana, D. incisa, D. kenheilii, D. nelsonii, D. obtusa, D. paradisa, D. pinnata, D. sophia, D. sophioides, D. torulosa
D. adenophora, D. brevisiliqua, D. californica, D. incana, D. incisa, D. kenheilii, D. longepedicellata, D. obtusa, D. paradisa, D. pinnata, D. sophia, D. sophioides, D. torulosa
Synonyms Sisymbrium longepedicellatum, D. brachycarpa var. eglandulosa, D. incisa subsp. filipes, D. incisa var. filipes, D. longepedicellata var. glandulosa, D. pinnata subsp. filipes, D. pinnata var. filipes, D. rydbergii var. eglandulosa, Hesperis longepedicellata, Sisymbrium brachycarpum var. filipes, Sisymbrium incisum var. filipes, Sisymbrium incisum var. xerophilum, Sisymbrium longepedicellatum var. glandulosum, Sophia filipes, Sophia glandifera, Sophia gracilis, Sophia longepedicellata Sophia nelsonii, D. brachycarpa var. nelsonii, D. pinnata subsp. nelsonii, D. pinnata var. nelsonii
Name authority (E. Fournier) O. E. Schulz: in H. G. A. Engler, Pflanzenr. 86[IV,105]: 324. (1924) (Rydberg) Al-Shehbaz & Goodson: Harvard Pap. Bot. 12: 422. (2007)
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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