Phylogenetic relationships of the subtribe Oncidiinae (Orchidaceae) inferred from structural and DNA sequences (matK, ITS): a combined approach

Abstract

With the aim of exploring the significance of structural characters in phylogeny estimation of subtribe Oncidiinae, a combined parsimony analysis based on leaf foliar-anatomical, morphological and DNA sequence data of the matK and ITS regions was carried out. Two equally parsimonious trees were obtained which differ only in the position of 1 taxon. Oncidiinae was recovered as monophyletic and characterized by the presence of abaxial and adaxial leaf papillae. Seven structural synapomorphies define 5 clades with strong support, including: 1) the Lockhartia clade defined by a conduplicate leaf blade, 2) the Trichocentrum clade, defined by a blade anphistomatic and 2 or more strata of vascular bundles, 3) a clade composed of the genera Fernandezia, Ornithocephalus and Telipogon, grouped by the absence of stegmata in the vascular bundles and by their monopodic growth, 4) a large clade composed of most derived clades of Oncidiinae, defined by the presence of 2 strata on the adaxial hypodermis, 5) Tolumnia clade, defined by a marginally conduplicate leaf blade. Most of the additional clades are supported by structural character combinations; the Miltonia y Trichopilia clades, as well as the terminal branches of clades with intermediate position in the trees are not supported by structural characters. The most derived clades are supported only by structural characters resolved as reversals.