A new species of Arthrocnemum (Salicornioideae: Chenopodiaceae-Amaranthaceae) from West Africa, with a revised characterization of the genus

Abstract

A new species Arthrocnemum franzii Sukhor. is described from the Republic of Cape Verde (Sal, Maio and Boa Vista islands). The species is recognized as distinct from Arthrocnemum macrostachyum (Moric.) K.Koch based on differences in the perianth shape, length of the anthers and style, and seed-coat ornamentation. No seed heteromorphism is observed within individuals of either species, despite differences in the size of the central and lateral flowers within each cyme (heteroanthocarpy). The North American Arthrocnemum subterminale (Parish) Standl. (syn. Salicornia subterminalis Parish) is morphologically distant from Eurasian Arthrocnemum or Salicornia/Sarcocornia group and should be excluded from these genera. The genus Arthrocnemum now comprises only two species (A. macrostachyum and A. franzii), distributed in the Mediterranean area, Macaronesia, West Tropical Africa and the Saharo-Arabian region. A generic description is here elaborated, clearly delimiting Arthrocnemum from morphologically similar species of Sarcocornia. A list of current species previously considered as Arthrocnemum is provided. It is argued that the taxonomic status of Salicornia mucronata Lag. (1817), mentioned in some references as a synonym of Salicornia macrostachya Moric. (1820) [≡Arthrocnemum macrostachyum (Moric.) K.Koch], is indeed a new synonym of Anabasis articulata (Forssk.) Moq. (subf. Salsoloideae). Both names merged with Arthrocnemum macrostachyum – Salicornia virginica Forssk. and Arthrocnemum glaucum (Delile) Ung.-Sternb. var. fasciculatum Sennen were lectotypified. The typification of the genus Arthrocnemum has so far been lacking and requires a special proposal with a conserved type.