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Title: Disentangling bindweeds : systematics and evolution of tribe Merremieae (Convolvuceae)
Author: Simões, Ana Rita Giraldes
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2013
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Convolvulaceae is a family of lianas, herbs and subshrubs with a worldwide distribition. It has been a clearly defined monophyletic family, although the tribal and generic classification are still subject of debate. Recent studies have introduced the use of molecular data to clarify the phylogeny of Convolvulaceae, and authors have attempted to reach consistency of morphological characters with the newly available DNA sequences for some parts of the family; yet, tribal delimitation has remained uncertain. Tribe Merremieae, in particular, is problematic: its monophyly was rejected, and no synapomorphies exist to define it. The generic delimitation within the tribe is equally problematic, with its largest genus also not being monophyletic and morphologically ill defined. The present thesis aims at resolving the complicated systematics of this tribe, combining for the first time large morphological, palynological and molecular datasets. Molecular sampling is considerably expanded in comparison to previous studies and morphological and palynological data are broadly surveyed to fill in the gaps of information. Sampling successfully includes all genera in the tribe, and achieves to represent a wide range of geographic distribution and morphological variation across the taxa. Newly described variation is presented and new characters highlighted as potentially taxonomically informative. Evolutionary relationships are investigated by a combination of molecular phylogenetic methods: Maximum Parsimony, Maximum Likelihood and Bayesian inference. A new insight on relationships between the taxa is brought forward: the monophyly of the tribe is rejected, and genus Merremia is divided into several clades with high support and great morphological congruence. The classification of tribe "Merremieae" is for the first time thoroughly revised based on well resolved and high supported relationships, and clear synapomorphies are discovered to be used as diagnostic characters at generic level. The tribal concept is proposed here be discarded and new, better supported and morphologically clearly delimited, genera are described. As a conclusion, a taxonomic revision of one of the traditional genus in Merremieae is presented • Xenostegia. Two species (Merremia pinnata and Merremia sapinii) are included in the genus based on well supported relationships and congruent molecular, morphological and palynological evidence. This genus also has a long history of taxonomic and nomenclatural problems at specific level, which are here addressed. The present thesis, therefore, offers not only a well resolved and supported phylogeny of the "tribe" based on a large and diverse dataset, but also begins to address the taxonomic challenges that these newly discovered relationships have brought to light.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available