Phylogertetic Relationships among Dracaenoid Genera (Asparagaceae: Nolinoideae) Inferred from Chloroplast DNA Loci

The global evolutionary pattern among the dracaenoid plant genera Dracaena, Pleomele, and Sansevieria has remained ambiguous. Their classification has been disputed due to different taxonomic interpretation and the difficulty in morphological characterization of the species and genera. This study explores the phylogenetic analysis of 95 species representing all three genera using four combined chloroplast intergenic spacer DNA regions (trnL-trnF, ndhF-rpl32, trnQ-rps16, and rp132-trnL). The combined dataset was analyzed using parsimony, maximum likelihood, and Bayesian analysis. Results show that 1) dracaenoids are monophyletic; 2) the Hawaiian Pleomele species are the sister group to the remainder of the dracaenoid clade; 3) species of Dracaena and the remaining Pleomele are intermixed; 4) Sansevieria is monophyletic, but nested within Dracaena; 5) the Central American species D. americana and D. cubensis are the sister group to the remainder of the non-Hawaiian dracaenoid species. The Hawaiian Pleomele are morphologically and phylogenetically distinct from the remaining dracaenoids and are recognized as a distinct genus, Chrysodracon, and new species combinations are made. Dracaena is paraphyletic in regards to Sansevieria and those species should be recognized as species of Dracaena. The polyphyletic status of Pleomele species nested within Dracaena confirms previous morphology based studies that combined these genera.