Lidia I. Cabrera

Phylogenetic relationships of aroids and duckweeds (Araceae) inferred from coding and noncoding plastid DNA

Familial, subfamilial, and tribal monophyly and relationships of aroids and duckweeds were assessed by parsimony and Bayesian phylogenetic analyses of five regions of coding (rbcL, matK) and noncoding plastid DNA (partial trnK intron, trnL intron, trnL-trnF spacer) for exemplars of nearly all aroid and duckweed genera. Our analyses confirm the position of Lemna and its allies (formerly Lemnaceae) within Araceae as the well-supported sister group of all aroids except Gymnostachydoideae and Orontioideae. The last two subfamilies form the sister clade of the rest of the family. Monophyly of subfamilies Orontioideae, Pothoideae, Monsteroideae, and Lasioideae is supported, but Aroideae are paraphyletic if Calla is maintained in its own subfamily (Calloideae). Our results suggest expansion of the recently proposed subfamily Zamioculcadoideae (Zamioculcas, Gonatopus) to include Stylochaeton and identify problems in the current delimitation of tribes Anadendreae, Heteropsideae, and Monstereae (Monsteroideae), Caladieae/Zomicarpeae, and Colocasieae (Aroideae). Canalization of traits of the spathe and spadix considered typical of Araceae evolved after the split of Gymnostachydoideae, Orontioideae, and Lemnoideae. An association with aquatic habitats is a plesiomorphic attribute in Araceae, occurring in the helophytic Orontioideae and free-floating Lemnoideae, but evolving independently in various derived aroid lineages including free-floating Pistia (Aroideae).

Greenwoodiella, a New Genus of Spiranthinae (Orchidaceae) from North and Central America and the Greater Antilles, with a New Species from the Chihuahuan Desert

Abstract A new orchid species from the Chihuahuan Desert region in Tamaulipas, Mexico and Texas, U. S. A., is described and illustrated. The phylogenetic position of the new species was assessed by parsimony and maximum likelihood analyses of nuclear (ITS) and plastid (matK-trnK, trnL-trnF) DNA sequences of 61 species/35 genera of Spiranthinae and 15 additional species and genera of Cranichideae. The results indicate a close relationship of the new species to several species previously included in Schiedeella, especially S. wercklei, but our analyses also show that such a group does not belong to the clade that includes the type species of Schiedeella (S. transversalis), being instead sister to Mesadenus. A new genus, Greenwoodiella, is proposed to include the new species (G. deserticola) and its closest relatives (G. micrantha var. micrantha, G. micrantha var. garayana, and G. wercklei). The identity of Lexarzas Neottia micrantha is clarified, the other species belonging in this clade are discussed, and the required transfers made. An identification key to the three species and two varieties we recognize in the new genus is provided.