MOLECULAR EVIDENCE FOR THE SYSTEMATIC PLACEMENT OF ECHINOCEREUS-PENSILIS (BRANDEGEE,K.) PURPUS,J. (CACTACEAE)

Data obtained from the study of chloroplast DNA (cpDNA) restriction si te variation was used to determine the phylogenetic affinities of the Baja California endemic cactus, Echinocereus pensilis. Previous studie s of morphological characters associated this species with members of the tribe Hylocereeae, while others included this species within the g enus Echinocereus. Variation in cpDNA restriction sites for twelve res triction enzymes disclosed 83 variable restriction sites; cladistic ev aluation of these data placed E. pensilis as the most basal member of the genus Echinocereus. Members of the tribe Hylocereeae sampled (incl uding Aporocactus) were found to be within a distinct, monophyletic li neage, unrelated to E. pensilis.