Boechera gracilenta |
Boechera fernaldiana |
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Selby's rockcress |
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Habit | Perennials; short- or (rarely) long-lived; apomictic; caudex usually not woody. | Perennials; long-lived; (cespitose); sexual; caudex somewhat woody (sometimes with persistent, crowded leaf bases). | ||||
Stems | 1–9 per caudex branch, arising from center or margin of rosette near ground surface, (1.5–)2.5–5.5 dm, densely pubescent proximally, trichomes short-stalked, 2–4-rayed, 0.1–0.5 mm, mixed with some simple ones, to 0.8 mm, glabrous distally. |
usually 1 per caudex branch, arising from center of rosette, near ground surface or slightly elevated on woody base, 1–3.8 dm, densely pubescent proximally, trichomes short-stalked, 4–8-rayed, 0.04–0.1 mm, sometimes mixed with stalked, 2-rayed ones, to 0.5 mm, usually sparsely pubescent distally. |
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Basal leaves | blade oblanceolate, 2–9 mm wide, margins shallowly dentate or sometimes entire, ciliate proximally, trichomes (simple and spurred), to 1.2 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 4–6(–8)-rayed, 0.1–0.5 mm. |
blade narrowly oblanceolate, 1–4 mm wide, margins entire, ciliate along petiole, trichomes (simple), to 1 mm, surfaces densely pubescent, trichomes short-stalked, 4–8-rayed, 0.04–0.1 mm. |
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Cauline leaves | 4–9, not concealing stem; blade auricles 1–3 mm, surfaces of distalmost leaves usually glabrous. |
5–10, not concealing stem; blade auricles 0.3–2 mm, surfaces of distalmost leaves usually sparsely pubescent. |
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Racemes | 7–20-flowered, usually unbranched. |
10–20-flowered, usually unbranched. |
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Flowers | ascending at anthesis; sepals pubescent; petals lavender, 6–7 × 1.5–2 mm, glabrous; pollen spheroid. |
ascending at anthesis; sepals (purplish or greenish) glabrous or sparsely or moderately pubescent; petals white or purple to lavender, 7–12 × 1.5–4 mm, glabrous; pollen ellipsoid. |
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Fruiting pedicels | divaricate-ascending, gently curved downward, (7–)10–18 mm, glabrous. |
divaricate-ascending, straight, 5–20 mm, sparsely pubescent, trichomes appressed, branched. |
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Fruits | usually widely pendent, rarely horizontal, not appressed to rachis, not secund, slightly curved, edges parallel, (3–)4.5–7 cm × 1.7–2 mm; valves glabrous; ovules 60–96 per ovary; style 0.1–0.3 mm. |
divaricate-ascending, not appressed to rachis, not secund, straight or curved, edges parallel, 3.5–6.5(–7.5) cm × 1–1.6 mm; valves glabrous; ovules 30–72 per ovary; style 0.1–1 mm. |
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Seeds | sub-biseriate, 1.2–1.8 × 0.9–1.2 mm; wing continuous, 0.1–0.25 mm wide. |
uniseriate, 1–1.2 × 0.8–1 mm; wing continuous, ca. 0.1 mm wide. |
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Boechera gracilenta |
Boechera fernaldiana |
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Phenology | Flowering Apr–May. | |||||
Habitat | Rocky slopes and sandy soil in pinyon-juniper woodlands and mountain shrub communities | |||||
Elevation | 1900-2300 m (6200-7500 ft) | |||||
Distribution |
AZ; CO; NM; UT
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CO; NV; UT |
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Discussion | Morphological evidence suggests that Boechera gracilenta is an apomictic species that arose through hybridization between B. fendleri and B. pallidifolia; it is superficially similar to the sexual diploid B. perennans but is not closely related (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Subspecies 2 (2 in the flora). Taxa treated here as subspecies of Boechera fernaldiana share many morphological traits, and most recent authors (R. C. Rollins 1993; N. H. Holmgren 2005b) did not recognize them as distinct. They are consistently separated by the characters listed below, show some degree of molecular divergence (C. D. Bailey et al., unpubl.), and their ranges are separated by ca. 500 km. They clearly represent genetically isolated population systems that warrant taxonomic recognition. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 7, p. 381. | FNA vol. 7, p. 378. | ||||
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Arabis gracilenta, Arabis selbyi, B. selbyi | Arabis fernaldiana, Arabis canescens var. stylosa, Arabis fernaldiana var. stylosa | ||||
Name authority | (Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 240. (2007) | (Rollins) W. A. Weber: Phytologia 51: 370. (1982) | ||||
Web links |