Amaranthus flavus var. bractealis Moquin-Tandon (1849: 258)

Iamonico, Duilio, 2016, Nomenclature survey of the genus Amaranthus (Amaranthaceae). 5. Moquin-Tandon’s names, Phytotaxa 273 (2), pp. 81-114 : 95

13. Amaranthus flavus var. bractealis Moquin-Tandon (1849: 258)

Type (lectotype here designated):— NEPAL. Nepalia , 1821, Wallich s.n. (P00606387 [digital image!], image of the lectotype is available at http://dsiphoto.mnhn.fr/sonnerat/LAPI/scanL/L20080229/P00606387.jpg).

= Amaranthus × wallichii Iamonico , hybr. nov. ( Amaranthus cruentus L. × Amaranthus hybridus L.)

Diagnosis:— Amarantho cruento similis, sed bracteis 1.7 vicis longioribus quam sepalis; A. hybrido similis, sed sepali nervo mediano luteo-castaneo.

Nomenclatural notes:—The taxon bractealis was described by Moquin-Tandon (1849: 258) as one of the three variety of Am. flavus . A short diagnosis (“ foliis lanceolatis, paniculis majoribus, floribus abortivis, bracteis luxuriantibus numerosissimis acutissimis ”), the provenance (“ In Nepalia ”), and the collector (“ Wall. [Wallich]”) were given. There is one specimen at P (barcode P00606387) bearing two pieces of the synflorescence and, separately, one leaf, plus the original label “ Amaranthus flavus Linn. var. δ bractealis Prodr. 13, 2, p. 2658 Nepalia 1821 cl. Wallich ”. The morphological characteristics of the exsiccatum match with the Moquin’s diagnosis. I here designated the specimens P00606387 as the lectotype of the name Amaranthus flavus var. bractealis .

Taxonomical notes:—The lectotype bears a label on the bottom-right including a Sauer’s re-identification (dated 1960) as Am. hypochondriacus L. (J. D. Sauer also indicated “ ( Amaranthus leucocarpus S. Wats. ) ”). Although Sauer (1967) has not cited any of the Moquin’s Am. flavus varieties in his taxonomic revision of the Grain Amaranths (including Am. powellii S.Watson , Am. hybridus L., Am. quitensis Kunth, Am. hypochondriaus , Am. cruentus L., and Am. caudatus L.), he treated Am. flavus L. as heterotypic synonym of Am.hypochondriacus , also listing Am.leucocarpus S.Watson.As a consequence, Sauer (1967: 111) had probably in mind the synonymization of the var. bractealis with Am. hypochondriacus . Iamonico (2014a), by the typification of the Linnaean Am. flavus , showed that this name is actually a later heterotypic synonym of Am. cruentus . Morphological differences between Am. hypochondriacus , and Am. cruentus concern the structure of the synflorescence and the shape of bracts. Am. hypochondriacus has synflorescences often moniliform, with main florescence (1.5−)2.0− 2.5 cm wide, and bracts with membranous borders narrowing to apex, while Am. cruentus has synflorescences never moniliform, with main florescence narrower, and bracts with membranous borders abruptly interrupted at the half (so the apex is clearly awned) [see e.g., Iamonico 2016a, and Mosyakin & Robertson 2003 (“ bracts…subspinescent ” for Am. hypochondriacus , and “ Bracts…apex…spinescent ”, for Am. cruentus )]. The lectotype here designated for the var. bractealis shows bracts clearly awned with membranous border abruptly interrupted, so it is more similar to Am. cruentus than Am. hypochondriacus . However, the length of the bracts is about 5.0 mm (about 1.7 times the length of the tepals), while in Am. cruentus bracts are as long as or sligthly longer (up to 1.5 times) than the perianth. The var. bractealis so partially appears to be similar to Am. hybridus (see e.g. Mosyakin & Robertson 2003, Iamonico 2015). On the basis of the description by Moquin-Tandon (1849: 258), a character (that cannot be seen on the lectotype) refers indeed to Am. cruentus : the colour of the flower. Moquin-Tandon (l.c.) stated “ flores….flavescentes….flavido-aurei ”, probably referring to the colour of the median veins of the perianth segments not of the bracts (for which Moquin-Tandon reported “ bracteaea…carinâ viridi ”). Tepals have usually the median vein yellow-brown coloured in Am. cruentus , Am. hybridus has tepals with median vein usually dark-green. All things considered, Am. flavus var. bractealis apperas to be intermediate between Am. cruentus , and Am. hybridus . Further and important information given by Moquin-Tandon (1849: 258) in the protologue is: “ floribus abortivis ”. This characteristic leds to think for an hybrid origin of the Wallich’s plant. Actually, the two parts of synflorescences of the lectotype show a typical structure of Amaranthus sterile plant, dispaying a high number of bracts that are densely packed due to the low number of fertile female flowers. This synflorescence configuration usually characterizes the hybrids (see e.g., Costea & al. 2005).

In conclusion, it seems that the Moquin’s variety can be considered a heterotypic synonym of the hybrid Am. cruentus × Am. hybridus , but any name appears to be formally published and described. I here propose to dedicate the putative hybrid between Am. cruentus and Am. hybrydus to N. Wallich wo first collected the plant of the new hybrid. Further studies (molecular ones) are necessary to verify the taxonomic value of the hybrid.