Caroxylon, Thunberg, 1782

Mucina, Ladislav, 2017, Caroxylon (Chenopodiaceae s. str.) in continental southern Africa and Madagascar: a preliminary nomenclatural synopsis and biogeographical considerations, Phytotaxa 312 (2), pp. 151-178 : 154

Caroxylon as a taxonomic challenge

There are few widely distributed species in Caroxylon , alongside many species with limited or widely disparate distributions. The local refugial nature of some habitats (such as valleys of intermittently flowing rivers, edges of isolated salt pans or isolated coastal dune systems) may possibly support endemic lineages.

An alpha-taxonomic revision of the southern African taxa of Caroxylon is clearly overdue. There are 93 species and 2 varieties listed in this synopsis that belong to Caroxylon . Similarities in habit, the low number of easy-to-observe morphological traits (so typical for many groups within Chenopodiaceae ), poor collecting intensity (probably due to the season for optimal flowering being poorly targeted by collecting botanists) and the “general paucity of reliable identification traits notorious to some groups within Chenopodiaceae / Amaranthaceae ” makes the identification of taxa within Caroxylon particularly difficult. The works by Klopper (2000), Klopper & van Wyk (2001), Feodorova (2011), and (Feodorova & Samigullin (2015), who examined leaf anatomy and indumentum southern African Salsola s.l., are certainly steps in the right direction.

The morphological studies of living material as well as of the great majority of the types of the taxa formerly classified within the section Caroxylon (of genus Salsola ) from southern Africa (L. Mucina, in progress) have confirmed that the diagnostic characters clearly match the circumscription of the taxon formerly known as Salsola sect. Caroxylon (Thunb.) Fenzl in Ledeb. (1851: 809). All of the members belonging in this section were shown to be a clade, interpreted by Akhani et al. (2007) as the genus Caroxylon , which deserves, together with a number of other salsolid genera, a status of own tribe, i.e. Caroxyleae (“Caroxylonae” in Akhani et al. 2007) on morphological grounds (a fact corroborated by physiological and molecular studies, see above).

Facing the corroborative molecular, ecophysiological and morphological evidence, nomenclatural rectification in form of combinations of the woody taxa formerly considered in southern Africa as to belong to Salsola becomes necessary. This paper undertakes this task with an aim to provide a nomenclator serving as precursor to a regional revision of Caroxylon in the southern African region.

Preliminary indication of the upcoming nomenclatural changes in the southern African representatives of Salsola s.l. was published by Mucina & Snijman (2013: 233–235) as these authors have recognised the genus Caroxylon and suggested, using preliminary ‘phrase names’, reclassification of the original Salsola species to become Caroxylon .