A preliminary analysis of phylogenetic relationships in Cymbidium (Orchidaceae) based on nrITS sequence

The infrageneric classification currently in use for Cymbidium is based on gross morphology, with emphasis on the number of pollinia and state of fusion between lip and column. The sequences of nrDNA regions of 27 species and 3 cultivars of Cymbidium and 3 outgroup species (Eulophia graminea, Geodorum densiflorum, Amitostigma pinguiculum) were analyzed using PCR amplification and direct DNA sequencing. The phylogenetic trees generated from maximum parsimony analysis, however, show that the existing division among three subgenera (subgen. Cymbidium, subgen. Cyperorchis and subgen. Jensoa) should be evaluated with more data. Subgenus Cyperorchis was not a monophyletic group, with die unexpected nesting of C. dayanum (subgen. Cymbidium) within it; subgenus Jensoa also appeared paraphyletic, with C. lancifolium being die sister group to the remainder of the genus; species of subgen. Cymbidium appeared polyphyletic, being split into several clades and intermixed with the main subgen. Cyperorchis and subgen. Jensoa clades, respectively. However, because of the insufficiency of informative characters of ITS sequences, some of die clades identified, especially the major lineages of Cymbidium, received relatively low support; sectional delimitations were also not clear within each subgenus. Further study is needed for achieving a robust phylogeny of Cymbidium.