PHYLOGENETIC ASSESSMENT Mark A. Hershkovitz2AND REVISEDCIRCUMSCRIPTION OFCISTANTHE SPACH(PORTULACACEAE)'ABSTRACT Reexamination of Carolin's cladistic analysis of Portulacaceae confirms that Cistanthe Spach should be segregatedfrom Canlandrinia 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 recognizedas a section there n. In ail, Cistanthe includes 45-50 western Arnerican species in five sections, including Cistanthesect. 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 thetaxa here included in Cistanthe has been obscured by earlier, unnatural, and sometimes erroneous classifications ofthese plants. Cistanthe Spach is a putatively monophyleticgenus of Portulacaceae comprising five sectionsand perhaps 45-50 western American species for-merly classified in Calyptridium Nutt. in Torrey& A. Gray, Phi'ippiamra Kuntze (= Silvaea Phi-lippi), Spraguea Torrey, five sections of Calan-drinia Kunth, and one subgenus of Lewisia Pursh(see Table 1 for sectional key, citations, and syn-onymy). In the present paper, I describe the tax-onomic history of Cistanthe, evidence for its nat-uralness as a genus, its relationship to otherPortulacaceae, evidence on phylogenetic relation-ships among the species, and its biogeography.TAXONOMIC HISroRY Spach (1836) segregated the Chilean speciesCalandrinia grandiflora Lindley, C. glaucaSchrader, C. discolor Schrader, and C. speciosaLehm. into a new genus, which he named Cis-tanthe. Virtually ail subsequent workers (e.g., Franz,1908; Kelley, 1973; McNeill, 1974; Nyanyano,1986, 1990; Pax & Hoffmann, 1934; Reiche,1897, 1898) continued to recognize these speciesin Calandrinia sensu lato (see Carolin, 1987).Calandrinia in the broadest sense includes morethan 100 species of western North America, west-ern South America, and Australia (Carolin, 1987,in press; Kelley, 1973). Reiche (1897, 1898), in a revision of ChileanPortulacaceae, recognized 12 sections of Calan-drinia s.]., including Calandrinia sect. Cistanthe,which corresponded to Spach's (1836) generic cir-cumscription of Cistanthe. Reiche's (1897, 1898)keys and descriptions make evident a close inter-relationship among Calandrinia sects. Andinae,Arenariae, Cistanthe, and Rosulatae (collective-ly, Cistanthe sect. Cistanthe) based on the com-mon presence of distinctive, resinous-appearing,black bract and sepal markings (Carolin, 1987)and often pubescent seeds (Kelley, 1973). Reichedid not propose a common category comprisingthese four sections, which differ primarily withrespect to plant size and branching habit (Carolin, ' This manuscript was adapted from the first of five that constitute a doctoral dissertation in botany completed atthe University of California, Davis, California. This study was funded, in part, by two Jastro-Shields Scholarships fromthe University of California, Davis, a Smithsonian Graduate Student Fellowship, a Smithsonian Short-term VisitorAward, a Smithsonian Pre-doctoral Fellowship, and two travel awards from the Department of Botany, University ofCalifornia, Davis. Varied forms of assistance from the following individuals are gratefully acknowledged: J. A. Doyle,R. H. Eyde, D. 1. Ford, P. Hershkovitz, W. A. Kelley, B. J. McCaskill, J. W. Nowicke, G. F. Russell, R. Schmid,J. L. Strother, G. L. Webster, and S. Yankowski.ANN. MISSOURI BOT. GARD. 78: 1009-1021. 1991.