Amaranthaceae - Systematics

Systematics

In the APG II system of 2003 (unchanged from the APG system, of 1998), the family is placed in the order Caryophyllales. It includes the plants formerly treated as the family Chenopodiaceae. The monophyly of this new, broadly defined Amaranthaceae has been strongly supported by both morphological and phylogenetic analyses.

The family Amaranthaceae was first published in 1789 by Antoine Laurent de Jussieu in Genera Plantarum, p. 87–88. The first publication of family Chenopodiaceae was in 1799 by Étienne Pierre Ventenat in Tableau du Regne Vegetal, 2, p. 253. The older name has priority and is now the valid scientific name of the extended Amaranthaceae (s.l. = sensu lato).

Many recent publications still refer to the family name Chenopodiaceae. Phylogenetic research revealed the important impact of the subfamily Polycnemoideae on the classification (see Cladogram): If Polycnemoideae are considered being part of Chenopodiaceae, then Amaranthaceae (s.str. = sensu stricto) have to be included, too, and the name of the extended family is Amaranthaceae. If Polycnemoideae would be separated as an own family, Chenopodiaceae and Amaranthaceae (s.str.) would form two distinct monophyletic groups and could be treated as two separate families.

Amaranthaceae Juss. (s.l.) include the former families Achyranthaceae Raf., Atriplicaceae Durande, Betaceae Burnett, Blitaceae T.Post & Kuntze, Celosiaceae Martynov, Chenopodiaceae Vent., nom. cons.', Corispermaceae Link, Deeringiaceae J.Agardh, Dysphaniaceae (Pax) Pax, nom. cons., Gomphrenaceae Raf., Polycnemaceae Menge, Salicorniaceae Martynov, Salsolaceae Menge, and Spinaciaceae Menge.

The systematics of Amaranthaceae are the subject of intensive recent research. Molecular genetic studies revealed the traditional classification, based on morphological and anatomical characters, often did not reflect the phylogenetical relationships.

The former Amaranthaceae (in their narrow circumscription) are classified in two subfamilies, Amaranthoideae and Gomphrenoideae, and contain about 65 genera and 900 species in tropical Africa and North America. The Amaranthoideae and some genera of Gomphrenoideae were found to be polyphyletic, so taxonomical changes are needed.

Current studies classified the species of former Chenopodiaceae to eight distinct subfamilies (the research is not yet completed): Polycnemoideae, which are regarded as a basal lineage, Betoideae, Camphorosmoideae, Chenopodioideae, Corispermoideae, Salicornioideae, Salsoloideae, and Suaedoideae.

In this preliminary classification, the Amaranthaceae s.l. are divided into 10 subfamilies with approximately 180 genera and 2,500 species.