On the value of nuclear and mitochondrial gene sequences for reconstructing the phylogeny of vanilloid orchids (Vanilloideae, Orchidaceae)

Most molecular phylogenetic studies of Orchidaceae have relied heavily on DNA sequences from the plastid genome. Nuclear and mitochondrial loci have only been superficially examined for their systematic value. Since 40% of the genera within Vanilloideae are achlorophyllous mycoheterotrophs, this is an ideal group of orchids in which to evaluate non-plastid gene sequences. Phylogenetic reconstructions for Vanilloideae were produced using independent and combined data from the nuclear 18S, 5 center dot 8S and 26S rDNA genes and the mitochondrial atpA gene and nad1b-c intron. These new data indicate placements for genera such as Lecanorchis and Galeola, for which plastid gene sequences have been mostly unavailable. Nuclear and mitochondrial parsimony jackknife trees are congruent with each other and previously published trees based solely on plastid data. Because of high rates of sequence divergence among vanilloid orchids, even the short 5 center dot 8S rDNA gene provides impressive levels of resolution and support. Orchid systematists are encouraged to sequence nuclear and mitochondrial gene regions along with the growing number of plastid loci available.