The primitive Epidendroideae (Orchidaceae): Phylogeny, character evolution and the systematics of Psilochilus (Triphoreae)

Considering the significance of the basal Epidendroideae in understanding patterns of morphological evolution within the subfamily, it is surprising that no fully resolved hypothesis of historical relationships has been presented for these orchids.; A morphological matrix of 40 taxa and 30 characters was constructed and a phylogenetic analysis was performed. The results support many of the traditional views of tribal composition, but do not fully resolve relationships among many of the tribes. A robust hypothesis of relationships is presented based on the results of a total evidence analysis using three molecular loci, gap characters and morphology. Palmorchis is placed at the base of the tree, sister to Neottieae, followed successively by Triphoreae sister to Epipogium, then Sobralieae. Tropidieae form a clade with the advanced Epidendroideae, and this sister to Nervilieae and Gastrodieae. Diceratostele gabonensis groups within this clade. These results support a primitive condition of plicate leaves with absent or reduced leaves evolving a minimum of five times. An objective of this study was to investigate anther evolution. Among the basal members we find anthers that are erect or exhibit varying degrees of incumbency. It is clear that the erect anthers of some orchids evolved independently from those observed in the Orchidoideae, and the primitive condition among the basal Epidendroideae is suberect/subincumbent. Epidendroid incumbency is achieved via combinations of bending in different regions of the anther, with the primitive condition being in the column region and to a lesser extent, the basal region of the anther. The primitive condition for pollinia is free monads with tetrads evolving twice, and sectile pollinia four times. Some authors have suggested that the type III stigma of Cephalanthera, possessing other primitive features, was evidence that it was intermediate between Neottieae and advanced Epidendroideae. Given its position in the Neottieae, this condition in Cephalanthera is a case of convergence.; Based on the results of other studies using nonorchids, it was expected that we would find higher rates of nucleotide substitutions and divergence rates in taxa that lack chlorophyll when compared to green relatives. This study confirms this for both nuclear ITS and mitochondrial nad1 for which there were significant numbers of achlorophyllous taxa represented. These taxa had lower transition:transversion ratios (TI:TV) than chlorophyllous taxa in the same clade and generally lower than other taxa.; As part of the study of the basal Epidendroideae, a monograph of the orchid genus Psilochilus (Triphoreae) was prepared in order to better understand the natural variation within the genus. Based on this work, there are seven species recognized, of which one is a newly described species, Psilochilus ecuadoriensis, from lowlands of western Ecuador. A molecular phylogenetic study of the genus, representing five of the seven species, was performed using the plastid trnL-F intergenic spacer. Psilochilus physurifolius is at the base of the genus. A grouping is formed between Psilochilus modestus and P. macrophyllus and a clade of P. mollis and P. ecuadoriensis.; Conditions of the labellum and vegetative leaf characters were mapped onto the strict consensus of the parsimony analysis including gaps. In the Triphoreae the primitive condition is to have clasping or apetiolate ovate leaves and a labellum with acute lateral lobes and three calli. Psilochilus has two calli and a petiolate leaf, with apetiolate leaves evolving again in P. macrophyllus; elliptic leaves evolved in P. physurifolius. The lateral lobes of the labellum are acute in most of the taxa with rounded or blunted lateral lobes evolving in the clade of P. mollis and P. ecuadoriensis. The clade of Psilochilus modestus and P. macrophyllus is distinguished from the clade of P. mollis and P. ecuadoriensis by a labellum with acute lateral lobes and ovate leaves...