Amaranthus hybridus L.

11. Amaranthus hybridus L., Sp. Pl. 2: 990. 1753 Type (lectotype designated by Townsend 1974: 19):— U.S.A. Habitat in Virginia, Herb. Linn. No. 1117.19 (LINN!, image of the lecyotype is available at http://linnean-online.org/11645/). = Amaranthus chlorostachys Willd., Hist. Amaranth.: 34. 1790. Type (lectotype designated by Iamonico 2016a: 521):— UNSPECIFIED LOCALITY, Hermes s.n. (B-W17521!, image of the lecyotype is available at https://herbarium.bgbm.org/object/BW17521000). = Amaranthus patulus Bertol., Comment. Itin. Neapol. 19. 1837. Type (lectotype designated by Iamonico 2016a: 525):— ITALY. Campania: Napoli al Pasconcello, September 1834, Bertoloni s.n. (BOLO!, image of the lectotype in Iamonico 2916°: Figure 3). = Amaranthus hybridus L. subsp. hybridus var. erythrostachys Moq., Prodr. [A.P. de Candolle] 13(2): 259. 1849. Type (lectotype designated by Iamonico 2016a: 522):— FRANCE. “ Hort. Tol. ”, 1844, sine coll. s.n. (G147762/1!, image of the lectotype available at http://www.ville-ge.ch/musinfo/bd/cjb/chg/adetail.php?id=138993&base=img&lang=en). Description:— Herbs 6–20(–25) dm tall, monoecious, annual (therophyte). Stems erect, glabrous (pubescent in the upper part), green to reddish, often branched. Leaves usually green, ovate to ovate-lanceolate, rhomboidal [(2.0–)3.0– 8.0(–13.0) × (1.0–)1.5–6.0(–6.0) cm], with usually entire margins, apex acute or obtuse, mucronate, base cuneate, usually glabrous, petioled [petiole (1.0–)1.5–4.0(–6.0) cm long]. Synflorescences terminal, panicle-like, the main florescence usually up to 15 cm long (longer than the paraclades), usually green. Floral bracts greenish or yellowish, lanceolate to lanceolate-linear [(2.5–4.5(–6.0) × 1.0– 1.5 mm)], 1.6–2.0 times longer than the perianth, acute, awned, with membranous border abruptly interrupted at the half, margin entire, glabrous. Staminate flowers with 5 tepals, ovate-lanceolate; stamens (4–)5. Pistillate flowers with 5 tepals, ovate to lanceolate [(1.5–)2.0–2.5(–3.0) × 0.5–0.7 mm], with acute and sometimes mucronate apex, median vein usually dark-green; stigmas 3. Fruit usually brown, ellipsoidal [1.5–2.5(–3.5) × 1.0– 1.2 mm], as long as or longer than the perianth, smooth to rugose, dehiscent. Seed lenticular (0.9–1.4 mm in diameter), black to dark reddish-brown. Iconography:— Ardenghi & Parolo (2010: 71, figs. 6b, e), Bayón (2015: 283, Figura 10). Phenology:— Flowering time April (Al-Eisawi & Al-Ruzayza 2015). Habitat and elevation:— Human-made habitat, at 250–300 m a.s.l. (Al-Eisawi & Al-Ruzayza 2015). Chromosome number:— 2n = 32, 34. Alien status:— Neophyte species native to tropical areas of North and Central America, it can be considered as naturalized in Saudi Arabia (Chaudhary 1998). Occurrence in Saudi Arabia (Fig. 14):— Al-Baha, Makkah (Al-Eisawi & Al-Ruzayza 2015), Tabuk (Aljieddani et al. 2021), Bisha (Abbas et al. 2020), and Taif (Abdullah et al. 2017). No finding was done during the filed surveys. Further researches are necessary to verify the distribution of Amaranthus hybridus in the country. Taxonomic annotations:— Amaranthus hybridus is a species characterized in having an high phenotypic variability, especially concerning the features of the flowers. Costea et al. (2001) recognized two subspecies [subsp. hybridus and subsp. quitensis (Kunth) Costea & Carretero] on the basis of the shape of the tepals (ovate and acute in subsp. hybridus, obovate to spathulate tepals and obtuse to truncate in subsp. quitensis). However, one of us (DI) believes that the taxon quitensis is more related to A. retroflexus, at least on the basis of shape and length of the tepal (a study is in progress by DI). In other cases, other taxa (e.g., A. cruentus L. or A. hypochondriacus L.) were accepted as subspecies of A. hybridus (see, e.g. Galasso et al. 2018). Anyway, further several forms were described in the past and a taxonomic revision is still lacking. We here accept the recognition of A. hybridus as separate species from the other member of the aggregate, according to Iamonico (2015).Published as part of Hassan, Walaa A., Al-Shaye, Najla A., Alghamdi, Salma, Korany, Shereen M. & Iamonico, Duilio, 2022, Taxonomic revision of the genus Amaranthus (Amaranthaceae) in Saudi Arabia, pp. 135-157 in Phytotaxa 576 (2) on pages 151-152, DOI: 10.11646/phytotaxa.576.2.1, http://zenodo.org/record/746128