Nomenclatural survey of the genus Amaranthus (Amaranthaceae). 11. Dioecious Amaranthus species belonging to the sect. Saueranthus

A nomenclatural study of Amaranthus names, linked to the dioecious taxa belonging to the sect. Saueranthus (subgen. Acnida), was carried out. All studied names are validly published but in need of nomenclatural clarifications. Lectotypes are designated for A. greggii var. muelleri (NY), whereas for A. ambigens, A. annectens, A. arenicola, A. myrianthus, and A. watsonii holotypes were cited (deposited at US, BM, GH, and US). Isotypes where found for A. ambigens (one specimen at NY), A. myrianthus (five specimens at GH, M, MO, RM, and US), and A. arenicola (three specimens at KSC, MO, and US), whereas for A. watsonii two isotypes were traced at US. A new synonymy, A. arenicola = A. myrianthus, is proposed, the latter name having nomenclatural priority to the former one. Based on preliminary taxonomic observations, two varieties are recognized under A. greggii, var. greggii and var. muelleri, which differ from each other on the ratio tepals/fruit (about 2/3 in var. muelleri vs. about 1 in var. greggii).