Amaranthus dubius Mart. ex Thell., Fl. Adv. Montpell.

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, Phytotaxa 576 (2), pp. 135-157 : 149-150

10. Amaranthus dubius Mart. ex Thell., Fl. Adv. Montpell. : 203. 1912

Type (neotype designated by Townsend 1974: 471–472):— GERMANY. Herbairum Regio Monacense, ex horto Erlangensis, s.d., s.c. s.n. (M0107382!, image of the neotype available at https://plants.jstor.org/stable/viewer/10.5555/al.ap.specimen. m0107382?loggedin=true) .

= Amaranthus tristis var. xanthostachys Moq., Prodr. [A. P. de Candolle] 13(2): 260. 1849 ≡ Amaranthus dubius var. xanthostachys (Moq.) Thell. in Asch. & Graebn., Syn. Mittel-Eur. Fl. 5: 266. 1914.

Type (neotype designated by Iamonico 2016c: 104): UNKNOWN ORIGIN. Herbarium Requien, s.d., s.coll. s.n. (P 04021942!, image of the neotype is available at http://mediaphoto.mnhn.fr/media/14494899601942MO7c2qCCiZJWunt).

Description:— Herbs 3–10 dm tall, monoecious, annual (therophyte). Stems erect, glabrous, green, branched. Leaves green, ovate, ± rhomboidal (2.0–)3.0–10.0 × (1.5–)2.0–6.0 cm, with entire margins, apex obtuse, mucronate, base cuneate, glabrous, petioled (petiole 0.8–5.5 cm long). Synflorescences terminal, panicle-like, green to yellowhish. Floral bracts greenish-yellowhish, lanceolate (1.2–2.0 mm long) shorter than the perianth, acute, awned, margin entire, glabrous. Staminate flowers with 5 tepals, ovate; stamens 5. Pistillate flowers with 5 tepals, oblong-spathulate (1.5–2.0) × 0.5–1.0 mm), with acute and mucronate apex; stigmas 3. Fruit brownish, ovoid (1.5–2.0 × 1.0– 1.5 mm), shorter than the perianth, smooth to slightly rugose, dehiscent. Seed lenticular (0.8–1.0 mm in diameter), dark-brown to black.

Iconography:— Bayón (2015: 280, Figura 8).

Phenology:— Flowering time february.

Habitat and elevation:— Human-made habitat (coastal plain), 5–15 m a.s.l.

Chromosome number:— 2n = 64 ( Behera & Patnaik 1982, Baquar & Olusi 1988, Ugborogho & Oyelana 1992, Greizerstein & Poggio 1994).

Alien status:— Neophyte species native to South America, it can be considered as casual in Saudi Arabia.

Occurrence in Saudi Arabia ( Fig. 12 ):— Our collections (Jizan) represent the first records of Amaranthus dubius in Saudi Arabia.

Nomenclatural notes on Amaranthus dubius :— The name Amaranthus dubius was published for the first time by Martius (1814: 197) who did not reported any diagnosis [only the symbols “*” (that means “ significat plantam, de qua anno 1813 non nisi semen adfuit ”), and “†” (that means “ nomen plantae nondum extra omnem dubitationem positum ”) were indicated (see Martius 1814: 3). As a consequence, Martius’ name is a nomen nudum and invalid from the nomenclatural point of view (Art. 38.2 Ex.1 of ICN). Moquin-Tandon (1849: 260), in his treatment of Amaranthaceae in Candolle Prodromus , reported “ A. dubius Mart. Hort. Erlang. 1814, p. 197 ” as synonym of A. tristis L. and, again, this name cannot be considered as valid according to the Art. 36.1b of ICN. Finally, Thellung (1912: 203) validly published the Martius’ name providing a diagnosis partially taken from Moquin-Tandon (1849, “ calyce vix bracteas superante…sepala oblonga, obtusa, mucronulata…Stam 5, interdum 4, raro 3 ”). Thellung (1912: 203) further indicated the provenance (“ Am. trop . … Indes occ. … Afr. trop . ... Afr. trop . … mais peut-être seulement à l’etat d’introduction récente ”) and a reference to Seubert’s Amaranthus tristis ( Seubert 1864: 237–238) . Note, however, that Seubert (1864) described A. tristis in having “bracteis perogonium subaequantibus” which is a character that contrasts the current concept of A. dubius . In fact, this latter species can be easily identified, among the species belonging to the subgen. Amaranthus sensu Mosyakin & Robertson (1996) , by the lenght of its bracts which are clearly shorter than the perianth (see also Mosyakin & Robertson 2003). According to the description given by Seubert (1864: 237–238), the species appears to be the real Linnaean A. tristis , a name that is currently considered as heterotypic synonym of A. tricolor (see Iamonico, 2014a: 148–149).

The typification of the name Amaranthus dubius has to be addressed in searching Martius’ collection which, according to HUH Index of Botanists (2013 -onwards), is preserved at the herbaria BR and M. No specimen of original material we traced at M. On the other hand, we traced three specimens at BR bearing labels reporting “HERBARIUM MARTII” (collected before 1806, July 20, 1827 and 1864). However, the “HERBARIUM MARTII” is in contrast with Martius’ so-called “private herbarium” which includes all specimens he received from others but not collected by him himself, and that was given to BR after his death (H. Esser pers. comm.). So, just because there is a label head “HERBARIUM MARTII”, it does not mean the specimen was collected by Martius, it just shows that it had been in his possession (H. Esser pers. comm.). As a consequence, we cannot be sure that the three BR specimens found are part of the original material for the name Amaranthus dubius . No further specimen, useful for the lectotypification purpose, were found. So, a neotypification is required according to the Art. 9.8 of ICN and we here confirm the proposal by Townsend (1974: 471–472) who neotypified the name using a specimen included in the Schwaegrichen’s collection at M (barcode M0107382).

Specimina visa selecta:— SAUDI ARABIA, Jizan, human-made habitat (coastal plain), 5–15 m a.s.l., 17 February 2021, leg. Masrhai et Al-shaye, det. Masrhai, conf. Iamonico (PNUH!, RO!; Fig. 13 ); ibidem (PNUH!, RO!) ; ibidem (PNUH!, RO!); ibidem (PNUH!, RO!).

Figures

FIGURE 12. Map of Amaranthus dubius.

FIGURE 13. Specimen of Amaranthus dubius collected at Jizan in february, 17 2021 by Y. Masrhai et al. (RO!).