Amaranthus tristis var. xanthostachys Moquin-Tandon (1849: 260)

Iamonico, Duilio, 2016, Nomenclature survey of the genus Amaranthus (Amaranthaceae). 5. Moquin-Tandon’s names, Phytotaxa 273 (2), pp. 81-114 : 104-105

34. Amaranthus tristis var. xanthostachys Moquin-Tandon (1849: 260)

Type (neotype here designated):—UNKNOWN ORIGIN. s.d., s. coll . (Heb. Requien) s.n. (P 04021942 [digital image!], image of the neotype is available at http://mediaphoto.mnhn.fr/media/14494899601942MO7c2qCCiZJWunt).

= Amaranthus dubius Martius ex Thellung (1912: 203) .

Type: not designated 6.

6 The typification of the name Amaranthus dubius is part of an ongoing study by the author of the present paper (Iamonico in prep.).

Nomenclatural notes:— Moquin-Tandon (1849: 260) provided a short diagnosis (“foliis et paniculis conformibus, floribus flavescentibus”), without specimens cited on it. I found a single sheet at P (barcode 04021942) bearing a plant and two labels on the bottom-right: “ Amaranthus incomptus | herb. Requien ”, and “ Amaranthus tristis Linn. | Prodr. 13, 2, p. 263 | var. β xanthostachys Prodr. loc. cit. ”. In the absence of useful data (e.g., the collection date on the label, or a reference to the Requien’s collection as reported in the protologue), I cannot be sure that this specimen is part of the original material so I prefer to avoid its use for the lectotypification purpose. According to the Art. 9.7 of the ICN, I here designated the P 04021942 as the neotype of the name Amaranthus tristis var. xanthostachys .

Taxonomical notes:—The Moquin-Tandon’s concept of Am. tristis appears to be very broad. The names cited in synonymy refer, in fact, to different taxa according to the current concept of Amaranthus : “Blitum Indicum 2 Rumph. Herb. Amb. 5, p. 231, t. 82, f. 2” ( Rumphius 1747, image of the Rumphius’ illustration available at http://bibdigital. rjb.csic.es/ing/Libro.php?Libro=5311& Pagina =320), “ Amaranthus tristis Willd. Amarant. p. 21, n. 14, t. 5 (Willdenow 1790: 21, Tab. 5, fig. 10, image of the Willdenow’s illustration available at http://bibdigital.rjb.csic.es/ing/Libro.php?Li bro=5802& Pagina =52), “f. 10”, and “... Wight ic. t. 51, 4” (Wight 1843: 514, image of the Wight’s illustration available at http://www.biodiversitylibrary.org/item/1857#page/241/mode/1up) are to be recognized as Am. tricolor (see Iamonico 2014a), while “ A. dubius Mart. Hort. Erlang. 1814, p. 197 ” ( Martius 1814) is currently known as Am. dubius Martius ex Thellung (1912: 203) . Am. tristis (now Am. tricolor ) and Am. dubius can be easily distinguished each other from the morphological point of view. A main character is the flower structure: Am. tricolor shows bracts as long as the perianth and 3 tepals, while Am. dubius has bracts shorter that the perianth and 5 tepals. Mosyakin & Robertson (1996: 278) proposed to treat Am. dubius into a separate sect. Dubia Mosyakin & K.R.Robertson (subgen. Amaranthus ), while Am. tricolor belongs to the subgen. Albersia sect. Pyxidium . On the basis of the neotype designated in the present paper, Am. tristis var. xanthostachys shows features that characterize Am. dubius as currently circumscribed (see e.g., Mosyakin & Robertson 2003, Iamonico 2013), and the two names can be proposed as heterotypic synonyms.Although the Moquin-Tandon’s variety was published earlier than Am. dubius (1849 vs. 1912 by Thellung), according to the Art. 11.2 of the ICN, the var. xanthostachys has no priority on Am. dubis because of different rank. Correct name at species rank is Am. dubius . If this taxon will be accepted in future at variety or subspecies rank, the Moquin-Tandon’s name should be re-considered.