The Portulacaceae, Basellaceae, Cactaceae, and Didiereaceae form a monophyletic group within the Caryophyllales, and evidence exists that the first may be paraphyletic if the latter three are recognized at the familial level. Several taxonomic treatments of the Portulacaceae based on morphological features have failed to produce consensus regarding infrafamilial relationships. The present paper employs sequences of the chloroplast gene ndhF to produce a molecular phylogeny of the portulacaceous cohort, focusing on the relationship among major lineages of the Portulacaceae and the three families potentially derived from within them. Results of this analysis supported two major clades within the monophyletic cohort. The first included Portulaca, Anacampseros and its relatives, much of Talinum, Talinella, and Cactaceae; the second, weakly supported, included the remaining genera of Portulacaceae, Basellaceae, and Didiereaceae. This phylogeny also showed that several generic circumscriptions remain inadequate, particularly that of Talinum sensu lato, which was polyphyletic in this analysis, and that all present classifications of the Portulacaceae include demonstrably non-monophyletic tribes.

Communicating Editor: Kathleen A. Kron