Amaranthus tristis var. leptostachys 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

33. Amaranthus tristis var. leptostachys Moquin-Tandon (1849: 260) , syn. nov.

Type (lectotype here designated):— U.S.A. St. Thomas, 1827, Wydler 80 (P barcode P00609934 [digital image!], image of the lectotype is available at http://dsiphoto.mnhn.fr/sonnerat/LAPI/scanL/L20080424/P00609934.jpg).

= Amaranthus cruentus Linnaeus (1759a: 1269) .

Type (lectotype designated by Townsend 1974: 12):— CHINA. Habitat in China, Herb. Linn. No. 1117.25 (LINN [digital image!], image of the lectotype is available at http://linnean-online.org/11651/).

Nomenclatural notes: — Moquin-Tandon (1849: 260) cited, after the short diagnosis (“ foliis minoribus, spicis longis gracillimis, floribus viridescentibus ”), the specimen “ Wydler! n. 80 in h. DC. ”. One specimen was traced at P (barcode P00609934) bearing three labels of which one includes the annotation “ amaranthus n° 80 St. Thomas 1827 Wydler ”. Although the annotations on exsiccatum at P (locality of collection, collector and the collection number) completely match the data reported in the protologue, according to McNeill (2014) I cannot be sure that this specimen is the only one in extant. As a consquence I here designated the exsicatum P00609934 as the lectotype of the name Amaranthus tristis var. leptostachys .

Taxonomical notes:—The lectotype is represented by a terminal part of a plant (branched), axillary glomerules subtended by leaves, and two terminal spike-like synflorescences. The morpholgical characteristics of the holotype are: stem brown-whitish, ribbed; leaves petioled (petiole 2−4 cm long) with blade ovate [(0.5−)1.5−3.2 × (0.7−)0.9−1.8], margins entire, base cuneate, and apex obtuse or slightly emarginate, often with a terminal mucro; floral bracts with membranous borders abruptly interrupted about at the half of the total length of the bract (the median vein is clearly visible), 2−3 mm long; flowers with 5 tepals as long as or slightly shorter than the bracts, apex obtuse, mucronate; fruit ellipsoidal or subglobose, as long as or slightly shorter than tepals, dehiscent. This morphological configuration fits well with Am. cruentus as it has been currently recognized (see e.g., Mosyakin & Robertson 2003, Iamonico 2013); a reidentification, which I consider incorrect, in Am. dubius Mart. ex Thell. appears in a recent label on the bottom-right of the sheet. The examination of literature revealed that Amaranthus tristis var. leptostachys was synonymized with Am. tricolor (see e.g., The Plant List 2013), or Am. dubius (see e.g., Cabrera 2005: 19−20), while Thellung (1914: 266) proposed the variety rank for the Moquin’s taxon [ Am. dubius var. leptostachys (Moq.) Thell. ]. Am. tricolor has pistillate flowers with 3 tepals, while the Am. tristis var. leptostachys includes plants with 5 tepals [it is interesting to note that Moquin-Tandon (1849: 255, 260) listed Am. tristis (now considered as heterotypic synonym of Am. tricolor according to Iamonico 2014a) among the group “ …calyx 5-sepalus… ”, so deviating the Linnaean concept of this species. Concerning Am. dubius , it is characherized by having bracts clearly shorter than the tepals (1.5−2.0 mm long), while the Moquin’s variety has bracts as long as or slightly longer than the tepals (2−3 mm long). In conclusion, I here proposed to synonymize the names Am. tristis var. leptostachys with Am. cruentus (new synonymy).