Phylogeny, Biogeography And Systematics Of Dysphanieae (Amaranthaceae)

After a rather turbulent taxonomic history, Dysphanieae (Chenopodioideae, Amaranthaceae) were established to contain five genera, four of which are monospecific (Cycloloma, Neomonolepis, Suckleya, Teloxys) and geographically restricted, and the fifth genus, Dysphania, having a nearly worldwide distribution and comprising ca. 50 species. This study investigates the phylogeny, biogeography and taxonomy of Dysphanieae. We studied specimens from 32 herbaria to infer morphological differences and distribution areas of the species and sampled 121 accessions representing 39 accepted species of the tribe for molecular phylogenetic analyses. The molecular phylogeny tested generic relationships of the tribe and infrageneric relationships of Dysphania on the basis of two plastid DNA markers (atpB-rbcL spacer, rpl16 intron) and two nuclear ribosomal markers (ETS, ITS) and was also used for an ancestral area reconstruction with BioGeoBEARS. Three of the monospecific genera (Neomonolepis, Suckleya, Teloxys) form a basal grade and appear to be relictual lineages of the tribe, while Cycloloma is nested within Dysphania. The ancestral area reconstruction favors a widespread ancestry for Dysphanieae, and the relictual lineages in Asia (Teloxys) and North America (Neomonolepis, Suckleya) might be explained by a wide distribution across Beringia during the Late Oligocene/Early Miocene. Dysphania likely originated in North America; however, the simultaneous diversification into three major clades, an Asian/African, an American and an Australian/African clade, indicates a widespread ancestor at the crown node of Dysphania. Our taxonomic revision results in four accepted genera in Dysphanieae, Dysphania, Neomonolepis, Suckleya and Teloxys. The sectional subdivision for Dysphania is revised. We subdivide the genus into five sections, D. sect. Adenois (13 spp.), D. sect. Botryoides (10 spp.), D. sect. Dysphania (17 spp.), D. sect. Incisa (2 spp.) and D. sect. Margaritaria (4 spp.); three strongly deviating species remain unplaced and need further attention.