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

by Rothacker, Erik Paul

Abstract (Summary)
Considering the significance of the basal Epidendroideae in understanding patterns of morphological evolution within the subfamily, it is surprising that a robust hypothesis of historical relationships has not been presented for these orchids. This is the first study to improve both taxon and character sampling. The phylogenetic study of the basal Epidendroideae consisted of two components. A molecular phylogeny using three loci representing each of the plant genomes including gap characters is presented for the basal Epidendroideae. The results of the morphological analysis results support many of the traditional views of tribal composition, but do not fully resolve relationships among many of the tribes. A robust hypothesis is presented based on the results of a total evidence analysis (TEA) using three molecular loci, gap characters and morphology. Palmorchis is sister to Neottieae, followed successively by Triphoreae sister to Epipogium, then Sobralieae. Tropidieae is sister to the advanced Epidendroideae, and this sister to Nervilieae and Gastrodieae. Diceratostele gabonensis groups within this clade. Morphology is studied mapped onto the TEA and discussed. 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 trn L-F intergenic spacer. Psilochilus physurifolius is at the base of the genus. Psilochilus modestus and P. macrophyllus form a clade and this sister to P. mollis and P. ecuadoriensis. Morphological characters that were useful for species delimitations were mapped onto this tree. Psilochilus is monophyletic based on sequence data, and is supported by the presence of two calli on the labellum and petiolate leaves.
Bibliographical Information:

Advisor:

School:The Ohio State University

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:character evolution epidendroideae morphology psilochilus triphoreae phylogeny orchidaceae systematics total evidence

ISBN:

Date of Publication:01/01/2007

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