PHYLOGENETIC ASSESSMENT AND REVISED CIRCUMSCRIPTION OF CISTANTHE SPACH (PORTULACACEAE)

Reexamination of Carolin's cladistic analysis of Portulacaceae confirms that Cistanthe Spach should be segregated from Calandrinia Kunth and should include Philippiamra Kuntze. Calyptridium Nutt. in Torrey & A. Gray (including Spraguea Torrey) cannot be excluded from Cistanthe on phylogenetic grounds and is therefore recognized as a section therein. In all, Cistanthe includes 45-50 western American species in five sections, including Cistanthe sect. Cistanthe, C. sect. Amarantoideae (Reiche) Carolin ex Hershkovitz, C. Calyptridium (Nutt. in Torrey & A. Gray) Hershkovitz, C. sect. Philippiamra (Kuntze) Hershkovitz, and C. sect. Strophiolum (B. Mathew) Hershkovitz. The phylogenetic relationship of Cistanthe to other Portulacaceae indicated in Carolin's cladogram is, upon reanalysis, equivocal, and the relationships among the sections remain poorly understood. Biogeographic understanding of the taxa here included in Cistanthe has been obscured by earlier, unnatural, and sometimes erroneous classifications of these plants.