Molecular phylogenetic systematics in the Dendrobiinae (Orchidaceae), with emphasis on Dendrobium sect. Pedilonum

Abstract

Molecular phylogenetic systematics of the Dendrobiinae (Orchidaceae), with emphasis on Dendrobium section Pedilonum. Telopea 10(1): 247–298. Molecular systematic research using the internal transcribed spacer (ITS) region of the 18–26S nuclear ribosomal DNA repeat unit, on representatives of most taxonomic units within the Dendrobiinae has provided independent support, in addition to morphological and biological data, for the phylogenetic reassessment of the taxon. At a broad level, the Dendrobiinae is polyphyletic with Epigeneium forming an independent clade; Dendrobium section Oxystophyllum is deeply embedded within one of the outgroups, subtribe Eriinae: Podochileae; and the remaining taxa isolated into two major groups, viz the Asian and Australasian clades. A detailed study of part of the Asian clade, with emphasis on representatives of the morphologically based Dendrobium section Pedilonum, groups species into seven major clades. Dendrobium section Pedilonum is shown to be non-monophyletic with most species previously interpreted as belonging to it being well isolated from D. secundum, the designated type of that taxon, and interspersed amongst representatives of D. section Calcarifera, Calyptrochilus, Cuthbertsonia, Dendrobium, Dolichocentrum, Oxyglossum and Platycaulon. Dendrobium section Rhopalanthe, which separates the two major clades containing representatives of D. section Pedilonum, is itself paraphyletic with representatives of sections Aporum and Bolbidium embedded within it. These molecular results, combined with morphological data, provide a strong basis for a reassessment of the phylogeny of part of the study taxon. A reclassification of this part of the Dendrobieae and Podochileae is provided in Appendix 2, including: re-instatement of the genus Oxystophyllum (Eriinae: Podochileae); the recognition and description of subtribes Epigeneiinae and Grastidiinae (Dendrobieae); recognition or re-instatement of the genera Aporum, Callista, Ceraia, Coelandria, Eurycaulis, Distichorchis, Pedilonum as distinct from Dendrobium; the elevation of Anisopetala to generic status; and where necessary the transfer of the appropriate species from Dendrobium to these genera.