A novel phylogeny-based generic classification for Chenopodium sensu lato, and a tribal rearrangement of Chenopodioideae (Chenopodiaceae)

Molecular phylogenetic analysis of the subfamily Chenopodioideae of the goosefoot family (Chenopodiaceae), with the addition of matK/trnK sequences to an existing trnL-F data set, indicates that Chenopodium as traditionally recognised consists of six independent lineages. One of these, the Dysphania-Teloxys clade, had already been recognised previously as a separate tribe Dysphanieae. Of the five others, Chenopodium is here re-defined in a narrow sense so as to be monophyletic. The C. polyspermum, C. rubrum and C. murale clades are successive sisters of a lineage constituted by Atripliceae s.str. plus Chenopodium s.str. Consequently, the long forgotten genera Lipandra (for C. polyspermum) and Oxybasis (for C. rubrum and relatives) are revived, and the new genus Chenopodiastrum (for C. murale and relatives) is published. The afore-mentioned five clades, taken together, are a monophylum corresponding to an enlarged tribe Atripliceae (a name that has priority over Chenopodieae). Last, the Linnaean genus Blitum (for C. capitatum and relatives), enlarged to include C. bonus-henricus, is the sister group of Spinacia in the tribe Anserineae (a name that has priority over Spinacieae). The aromatic species of Dysphania, the related genus Teloxys, as well as Cyclocoma and Suckleya form the enlarged tribe Dysphanieae. Building upon phylogenetic results, the present study provides a modern classification for a globally distributed group of plants that had suffered a complex taxonomic history due to divergent interpretation of single morphological characters for more than two hundred years. The seven genera among which the species traditionally assigned to Chenopodium are now distributed are defined morphologically and keyed out; for four of them (Blitum, Chenopodiastrum, Lipandra, Oxybasis) the component species and subspecies are enumerated and the necessary nomenclatural transfers are effected.