Comments
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Amaranthus dubius, a morphologically deviant allopolyploid, is very close genetically to both A. spinosus (sect. Centrusa) and members of sect. Amaranthus. This species most probably originated as a result of ancient hybridization between A. spinosus and either A. hybridus or A. quitensis (W. F. Grant 1959; T. N. Khoshoo and M. Pal 1972; M. Pal and T. N. Khoshoo 1965; J. D. Sauer 1967b; V. Srivastava et al. 1977). Amaranthus nothosect. Dubia Mosyakin & K. R. Robertson (A. sect. Amaranthus × A. sect. Centrusa), was proposed to accommodate A. dubius (S. L. Mosyakin and K. R. Robertson 1996).
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- Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
Comments
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Article reporting naturalization (in Hualien, Taiwan) appeared after publication of the family treatment for the Flora of China. See CHEN Shih-Huei & Ming-Jou Wu. 2007. Notes on four newly naturalized plants in Taiwan. Taiwania 52(1): 59-69).
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Description
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Plants glabrous or sparsely pubescent in distal parts. Stems erect, green, branched, 0.3-1 m. Leaves: petiole of proximal leaves equaling or longer than blade, becoming shorter distally; blade rhombic-ovate or ovate to elliptic, 3-12 × 2-8 cm, base broadly cuneate, margins entire, apex slightly acuminate to obtuse and faintly emarginate, mucronate. Inflorescences terminal panicles and axillary spikes; panicles erect or often drooping, green, dense, branched, leafless at least distally. Bracts lanceolate, shorter than 2 mm, shorter than tepals, apex spinescent. Pistillate flowers: tepals 5, oblong-spatulate to oblong, not clawed, 1.5-2 mm, apex acute, often very shortly mucronate; style branches strongly spreading, shorter than body of fruit; stigmas 3. Staminate flowers usually clustered at tips of inflorescence branches, sometimes gathered in proximal glomerules (as in A. spinosus); tepals 5, equal or subequal; stamens 5. Utricles ovoid or subglobose, 1.5-2 mm, slightly shorter than tepals, smooth to irregularly wrinkled, dehiscence regularly circumscissile. Seeds dark reddish brown to black, subglobose or lenticular, 0.8-1 mm diam., shiny, smooth. 2n = 64.
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Distribution
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introduced; Fla.; West Indies; South America; introduced and locally naturalized Europe, Asia, Africa.
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Flowering/Fruiting
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Flowering summer-fall in tropics, various seasons in subtropics.
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Habitat
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Waste places, disturbed habitats; 0-100m.
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Habitat & Distribution
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Native of the New World but now widely naturalized in the tropics and subtropics.
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