Boechera subpinnatifida |
Boechera divaricarpa |
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ashy rock-cress, Klamath rockcress |
spreading-pod rock-cress, uplifting suncress |
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Habit | Perennials; long-lived; sexual; caudex woody (often with persistent, crowded leaf bases). | Biennials or perennials; short-lived; apomictic; caudex present or absent. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 1–4(–5) dm, densely pubescent proximally, trichomes short-stalked, 2–6-rayed, 0.1–0.2 mm, sparsely pubescent distally. |
usually 1 per caudex branch, arising from center of rosette near ground surface, (1.5–)3–9 dm, glabrous or pubescent proximally, trichomes sessile, 2–4-rayed (some simple), to 0.7 mm, glabrous distally. |
Basal leaves | blade narrowly oblanceolate, 1–4(–5) mm wide, margins prominently dentate to subpinnatifid (leaf margins of sterile shoots often entire), ciliate near petiole base, trichomes (simple or 2-rayed), 0.4–0.6 mm, surfaces densely pubescent, trichomes short-stalked, (2–)4–9-rayed, 0.05–0.2 mm. |
blade oblanceolate, 2–10 mm wide, margins usually entire, rarely denticulate, ciliate along petiole, trichomes (simple), to 0.8 mm, surfaces sparsely to densely pubescent, trichomes sessile, 2–6-rayed, 0.1–0.4 mm. |
Cauline leaves | (10–)20–60, often concealing stem throughout; blade auricles 0.5–3 mm, surfaces of distalmost leaves moderately to sparsely pubescent. |
(10–)15–56, concealing stem proximally; blade auricles 1–5 mm, surfaces of distalmost leaves glabrous. |
Racemes | 8–30-flowered, usually unbranched. |
12–40(–65)-flowered, usually unbranched. |
Flowers | divaricate-ascending to pendent at anthesis; sepals pubescent; petals usually purple, rarely lavender, 9–14 × 1.5–3 mm, glabrous; pollen ellipsoid. |
divaricate-ascending at anthesis; sepals glabrous or with scattered trichomes; petals usually purple, rarely lavender, 6–9 × 1.5–3 mm, glabrous; pollen spheroid. |
Fruiting pedicels | reflexed, strongly recurved, 5–15 mm, pubescent, trichomes appressed, branched. |
divaricate-ascending to horizontal, straight, 5–12 mm, glabrous. |
Fruits | pendent, not appressed to rachis, not secund, straight to slightly curved, edges parallel, (3.5–)5–8 cm × (1.6–)2–3 mm; valves pubescent throughout; ovules 24–42 per ovary; style 0.5–1 mm. |
divaricate-ascending to horizontal, not appressed to rachis, not secund, straight, edges parallel, (4.5–)5.5–11 cm × 1.7–2.5 mm; valves glabrous; ovules 114–142 per ovary; style 0.05–0.2 mm. |
Seeds | uniseriate, 2.5–3.5 × 1.5–2.2 mm; wing continuous or at both ends, 0.4–0.8 mm wide. |
uniseriate to sub-biseriate, 1.4–2 × 1–1.5 mm; wing continuous, 0.1–0.2 mm wide. |
2n | = 14. |
= 21. |
Boechera subpinnatifida |
Boechera divaricarpa |
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Phenology | Flowering Mar–May. | Flowering May–Jul. |
Habitat | Rock outcrops, talus, gravelly soil, often in sagebrush-grassland communities | Rock outcrops, talus slopes and gravelly hillsides in sagebrush, mountain shrub, and open conifer forests |
Elevation | 800-2400 m (2600-7900 ft) | 900-2500 m (3000-8200 ft) |
Distribution |
CA; ID; NV; OR; UT
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CA; ID; MT; NV; UT; WA; WY
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Discussion | Originally thought to be restricted to northern California and adjacent Oregon, Boechera subpinnatifida is a sexual species that recently has been found in central Idaho, northern Nevada, and northwestern Utah. It appears to intergrade with both B. puberula and B. retrofracta, and species boundaries within this complex need further study. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
The name Arabis (Boechera) divaricarpa has been applied to nearly every hybrid containing a genome derived from B. stricta. This presents a serious barrier to understanding the evolution of Boechera and also is contrary to the International Code of Botanical Nomenclature, because some names usually placed in synonymy (i.e., B. grahamii and B. brachycarpa) have priority at species level (M. D. Windham and I. A. Al-Shehbaz 2007b). To address this problem, we treat the following as distinct species: B. acutina, B. grahamii (= B. brachycarpa of R. D. Dorn 2001), and B. pratincola (all considered synonyms of A. divaricarpa by R. C. Rollins 1993), and B. calderi, B. elkoensis, and B. quebecensis (taxa described after 1993). Detailed comparison among these taxa are provided by Windham and Al-Shehbaz (2007, 2007b). The narrow concept of B. divaricarpa advocated here encompasses apomictic triploid populations containing three distinct genomes, one each derived from B. retrofracta, B. sparsiflora, and B. stricta. If the species is defined more broadly, the name B. grahamii has priority. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 409. | FNA vol. 7, p. 374. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Arabis subpinnatifida | Arabis divaricarpa, Arabis stokesiae |
Name authority | (S. Watson) Al-Shehbaz: Novon 13: 389. (2003) | (A. Nelson) Á. Löve & D. Löve: Bot. Not. 128: 513. (1976) |
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