Opuntia basilaris |
Opuntia tortispina |
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beavertail, beavertail cactus, beavertail pricklypear |
plains pricklypear |
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Habit | Shrubs, forming clumps, 1–2(–3) segments tall, to 7–40 cm. | Shrubs, low, to 0.4 m, creeping from clumps, sometimes from thickened rootstocks. | ||||||||||||
Stem | segments not disarticulating, blue- to yellow-green, sometimes tinged maroon-purple, flattened, spatulate to broadly obovate or subcircular, thick, 5–22(–35) × 2–13.5(–16) cm, nearly smooth, papillose to puberulent (rarely glabrous); areoles 4–16(–19) per diagonal row across midstem segment, circular to elliptic, 3–5 × 3 mm; wool white to tan, aging gray. |
segments not easily detached, pale green to deep green, graying with age, wrinkled when stressed, flattened, broadly obovate to ovate, 6.5–15 × 4–10 cm, tuberculate, glossy, glabrous; areoles 6–9 per diagonal row across midstem segment, oval, obovate, or subcircular, 2.5–5 × 1.5–4 mm; wool tan, aging brown. |
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Spines | 0(–8) per areole, when present, usually in distal areoles, spreading, yellow, straight, acicular, 5–25 mm. |
1–9 on most areoles to only on distal 1/2 of stem segment, white to gray with pale brown tips and bases, sometimes brown throughout; central spines 1–3, all deflexed or 1–2 porrect or ascending, terete or flattened, occasionally spirally twisted, 25–70 mm; small spines (2–)3–6(–8) strongly deflexed, usually slender, even bristlelike, 5–15 mm. |
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Glochids | numerous, nearly filling areoles, yellow to red-brown or dark brown, to 3 mm. |
forming a well developed adaxial tuft, yellow to brownish white, to 6 mm. |
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Flowers | inner tepals pink to magenta throughout (rarely white), 25–40 mm; filaments red-magenta (rarely pale); anthers yellowish; style white to pink; stigma lobes white to cream. |
inner tepals yellow to gold, commonly darker to red near base, broadly spatulate, 30–40 mm, apiculate; filaments usually pale yellow; anthers yellow; style whitish to pale green; stigma lobes greenish. |
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Fruits | maturing tan, 20–40 × 15–23 mm, dry at maturity, puberulent, spineless (except in var. treleasei); umbilicus 5–12 mm deep; areoles 24–76. |
purple-red, oval to broadly ovate, subspheric or short ovoid, bases not narrowed, 30 × 20–25 mm, fleshy, base not narrowed, glabrous, spineless or nearly so; umbilicus deep; areoles 18–30. |
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Seeds | yellowish to tan, ± subspheric but angular, thick, 6.5–9 × 6.5–7 mm, sides smooth or bearing 1–3 depressions; girdle protruding to 1 mm. |
whitish to tan, irregularly shaped, flattened, 4–6 × 3–4 mm; girdle protruding 1–2 mm. |
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2n | = 44, 66. |
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Opuntia basilaris |
Opuntia tortispina |
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Phenology | Flowering spring–early summer (Apr–Jul). | |||||||||||||
Habitat | Grass-lands, pinyon-juniper-oak woodlands, sandy or shaley flats, rocky hills | |||||||||||||
Elevation | 1400-1800 m (4600-5900 ft) | |||||||||||||
Distribution |
AZ; CA; NV; UT; n Mexico
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CO; KS; NE; NM; OK; TX; WY |
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Discussion | Varieties 4 (4 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Opuntia tortispina is apparently of hybrid origin. It has intermediate character states from its putative parents, O. macrorhiza (fleshy and spineless fruits) and O. polyacantha (areoles with basal deflexed spines and barrel-shaped fruits). The spirally twisted spines, which the specific epithet implies, are not at all characteristic for this species. When O. tortispina and O. cymochila are considered conspecific, the former has priority, as first selected by N. L. Britton and J. N. Rose (1919–1923, vol. 1). One favored hypothesis as to the origins is that the O. humifusa-O. macrorhiza-O. pottsii complex spread across the United States from the east coast to Arizona. Opuntia polyacantha originated in north-central Mexico and spread northward. Tetraploid O. macrorhiza came into contact with the east flank of O. polyacantha and hybridized (probably repeatedly, even at present), producing the highly variable taxon referred to here as O. tortispina, which then spread eastward onto the plains. Opuntia tortispina has hexaploid members, presumably from unions of reduced and unreduced gametes. Those hexaploids apparently hybridize with hexaploid O. phaeacantha and add further to variation of O. tortispina. Many of these variations have been formally named or since treated as synonyms of O. macrorhiza. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 4, p. 144. | FNA vol. 4, p. 132. | ||||||||||||
Parent taxa | Cactaceae > subfam. Opuntioideae > Opuntia | Cactaceae > subfam. Opuntioideae > Opuntia | ||||||||||||
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Subordinate taxa | ||||||||||||||
Synonyms | O. cymochila, O. mackensenii, O. tortispina var. cymochila | |||||||||||||
Name authority | Engelmann & J. M. Bigelow: Proc. Amer. Acad. Arts 3: 298. (1856) | Engelmann & J. M. Bigelow: Proc. Amer. Acad. Arts 3: 293. (1856) | ||||||||||||
Web links |