Potential use of low-copy nuclear gene Xdh at lower taxonomic levels based on phylogenetic analysis of the nominal section of Dendrobium

Dendrobium is a large group of Orchidaceae, counting more than 1,100 species, whose classification, both within the genus and individual sections, is not straightforward. Therefore, the aim of our study was to perform phylogenetic analyses for representatives of a nominal section of Dendrobium and to test the usefulness of a low-copy nuclear gene encoding a xanthine dehydrogenase protein for reconstructing phylogeny. We also wish to compare the utility of two nuclear markers, Xdh and ITS. To realize this, we analyzed the diversity of the two markers and the reliability of the resulting trees. Our results indicate that the nuclear ITS region shows higher variability and clade credibility in trees, in closely related species, and between sections than the low-copy nuclear gene. Xdh may be more reliable at higher taxonomic levels, but confirmation of this requires further research.