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Dissertation zugänglich unter
Phylogeny of the Genus Masdevallia Ruiz & Pav. (Orchidaceae) based on morphological and molecular Data
Phylogenie der Gattung Masdevallia Ruiz & Pav. basierend auf morphologischen und molekularen Daten
Abele, Analisa Daniela
Dokument 1.pdf (26.058 KB)
Freie Schlagwörter (Deutsch):
Masdevallia , Orchidaceae , Phylogenie , nrDNA ITS , Morphologie , Biogeographie
Freie Schlagwörter (Englisch):
Masdevallia , Orchidaceae , Phylogeny , nrDNA ITS , morphology , biogeography
42.38 , 42.07 , 42.13 , 42.57 , 42.21
Rohwer, Jens G. (Prof. Dr).
Tag der mündlichen Prüfung:
Kurzfassung auf Englisch:
The genus Masdevallia is one of 28 genera in subtribe Pleurothallidinae, with approximately 500 species distributed from southern Mexico to southern Brazil Masdevallia species are characterized by coriaceous leaves borne on short ramicauls. The inflorescence emerges with an annulus a considerable distance below the abscission layer of the leaf; and the sepals are variously connate and commonly have tails. The taxonomy of Masdevallia is mainly based on floral structures. Although revisions of several sections of Masdevallia have been published during the last century, the delimitation of infrageneric taxa is still problematic, due to the lack of clear morphological synapomorphies. The naturalness and relationships of the subgenera, sections and subsections of Masdevallia was not previously examined in a phylogenetic context. The aims of this study are to 1) address the subgeneric and sectional relationships in Masdevallia with molecular data, 2) to correlate molecular with morphological data in order to establish morphological synapomorphies for clades well supported by molecular data and, 3) to correlate molecular with geographical data in order to evaluate the possible speciation histories and processes. Macro-morphological and micro–morphological character data were collected for 85 species of Masdevallia. These data were subjected to a maximum parsimony analysis. Maximum parsimony analyses and Bayesian analyses were also performed with sequences of the non-coding internal transcribed spacer (ITS) of the nuclear ribosomal DNA for 104 species. Maximum parsimony analyses of combined data were also performed. In the phylogenetic analysis of the genus Masdevallia based on morphological data, most groups are not supported by many characters. The lack of resolution obtained in this analysis suggests that detailed classifications at the infrageneric level are not well supported by morphological evidence. The phylogenetic relationships of the genus Masdevallia and of several groups within the genus are well resolved using ITS sequences.The strict consensus tree of the combined data was partly congruent with the ITS topology. The resulting phylogenetic tree obtained by maximum parsimony analyses of nuclear rDNA ITS sequences indicates that the genus Masdevallia is a well-supported monophyletic group. The infrageneric classification of the genus Masdevallia is only in part supported by the analysis of molecular data. Of the 11 subgenera of Masdevallia considered in this study, three forms strongly supported monophyletic groups in the analysis: subgenera Cucullatia, Meleagris and Fissia; the monospecific subgenera Teagueia, Scabripes and Volvula are of course monophyletic as well. Subgenera Masdevallia, Pygmaeia and Polyantha are not monophyletic. Subgenera Nidificia and Amanda form a clade with almost no internal resolution. Four major clades were resolved within Masdevallia. Clade A included Luerella pelecaniceps, which is endemic to Panama, at an altitude of 800 to 1 000 m above the sea level, and M. erinacea, which is found throughout the whole geographical range. Clade B included subgenus Pygmaeia section Zahlbrucknerae, subgenus Masdevallia sections Triotosiphon, Reichenbachianae, Minutae, Coriaceae, and Dentatae, subgenus Polyantha sections Alaticaules and Polyanthae, M. chimboensis and M. mentosa. A synapomorphy of this group is a verrucose (to papillose) epichile. Species of this group are found throughout the whole geographical as well as altitudinal range. Clade C grouped subgenus Pygmaeia sections Amaluzae and Aphanes, subgenus Masdevallia section Masdevallia, section Durae, section Racemosae, M. caudivolvula, M. macrura, M. hoeijeri, and M. bicornis. Lateral sepals connate without the formation of a broad mentum or a secondary mentum with the column-foot are characteristic for most species of clade C. Species of this group are restricted to the southern part of the geographical range, with most species found at higher elevations. Clade D grouped subgenera Teagueia, Cucullatia, Nidificia, Amanda, Fissia, Meleagris, and Dracula xenos. Synapomorphies of the species grouped in this clade are the arcuate sepaline tubes and the featureless disc of the lip. Species of clade D grow mainly in the Andes, at an altitude of 450 to 3 100 m above sea level.
The characters that have been used as rapid identifiers for diagnosing subgenera, sections and subsections within Masdevallia were plotted on one of the most parsimonious trees. The cross section of the peduncle, the anthesis of the flowers, the type of floral bract, the ovary smooth or with some external features such as crests or papillae, the grade of connation between the sepals, and the presence or absence of a division in the lip appear to be good synapomorphies for major clades in Masdevallia. Long tail-like appendages at the apex of the sepals appear to have evolved repeatedly in parallel and appear not to be phylogenetically informative.