Contribution of mitochondrial cox1 intron sequences to the phylogenetics of tribe Orchideae (Orchidaceae): Do the distribution and sequence of this intron in orchids also tell us something about its evolution?

In this paper, we use the mitochondrial region cox1 to assess the usefulness of this marker in addressing evolutionary relationships within the tribe Orchideae. Despite the low overall variation uncovered in this region, one good phylogenetic marker was identified. A large group I intron was shared across subtribe Orchidinae and some species of Habenariinae sensu Dressler. The clades identified in the cox1 tree were weakly supported, but consistent with previous studies based on nuclear ribosomal spacers (nrITS). Moreover, the phylogenetic analysis of the combined cox-HITS data matrix allowed us to highly improve the resolution of the ITS-only analysis and confirm several previously controversial relationships. A second purpose of this study was to analyse the evolution of the group I cox1 intron in Orchideae. This intron has a patchy distribution in angiosperms that has been claimed to be mostly due to horizontal transfer events. Our results suggest that, despite the differences observed in the co-conversion tracts in the tribe, vertical transfer is more consistent with the observed phylogenetic trees.