title: A phylogenetic investigation of Begonia L. section knesebeckia (Klotzsch) a.dc
Creators: name: Badcock, Zoe
Publisher: name: University of Glasgow
Year: 1998
Subjects: subject: Begonia, Knesebeckia.

description: This thesis uses morphological and molecular data to address the phylogeny of Begonia and in particular section Knesebeckia. Begonia is a species rich genus containing an estimated 1400 species distributed throughout the tropics and subtropics although none are present in Australia and New Zealand. Despite its horticultural importance few studies of the genus have been made and there is no published phylogeny for Begonia. Begonia section Knesebeckia is the only section from the c. 80 sections in Begonia to be currently recognised as containing species from more than one continent. There are 77 species (33 American and 44 Asian) currently attributed to Knesebeckia. With the prospect of an interesting biogeographic study, the aim of this research was to test the monophyly of Knesebeckia. A cladistic analysis of the morphology of Begonia was conducted using a sample of 86 taxa representing the morphological and geographical variation in Begonia. This analysis included all the available American Knesebeckia and 11 Asian Knesebeckia. A total of 66 macro- and micro-morphological characters was included in the analysis and resulted in 5340 trees contained in two islands of equally most parsimonious trees. From these results several conclusions were able to be made: 1) Knesebeckia is not monophyletic; 2) B. dichroa and B. olbia are not closely affiliated to other American Knesebeckia and are contained in a clade which is sister to a clade containing species with fleshy indehiscent fruit, mainly from Africa; 3) groupings of species suggested for the remainder of the American Knesebeckia include some species which may better be represented in section Begonia-, a clade centred around B. incarnata, the type of Knesebeckia; and a clade centred around B. boissieri for which the section Quadriperigonia should be reinstated; 4) several species were suggested as being closely related to section Gireoudia, e.g. B. peltata, and representatives from sections with a chromosome number of 2n = 28 (e.g. Gireoudia and Weilbachia) are recommended for inclusion in any future study of American Knesebeckia', 5) Asian Knesebeckia are shown to be paraphyletic, with representatives from sections Alicida, Diploclinium, Lauchea, Monophyllon, Parvibegonia, Putzeysia and Trilobaria nested in the clade of Asian Knesebeckia; 6) section Diploclinium is shown to be polyphyletic; species groups centred around B. putii and B. rubella are recommended for consideration in the context of any future analysis of Asian Knesebeckia. A cladistic analysis of sequence data for 30 species of Begonia from the noncoding chloroplast DNA region trnC - trnD was compared to an analysis of the morphology for the same 30 species. The results were not congruent and it was argued that the molecular phylogeny is more reliable than the morphology phylogeny for these 30 species and that combining the data sets for a "total evidence" view is not conducive to the production of a reliable and conservative estimate of the phylogeny of Begonia. The molecular phylogeny corroborates the conclusion in the larger morphological study that Knesebeckia is not monophyletic. The implications of the molecular phylogeny for the phylogeny of Begonia are discussed. The properties and evolution of this region of noncoding chloroplast DNA are investigated and compared to previous studies of other noncoding regions. The region is found to be AT rich with many insertions and deletions (indels). These indels are shown to be phylogenetically informative, exhibiting little homoplasy. A review of the literature relating to Knesebeckia indicate that B. grandis, an Asian species included in Knesebeckia from its inception, is the type of section Diploclinium. Eleven Asian species are provided with updated descriptions and admitted to section Diploclinium. Some existing species are placed as synonyms of these species and one new combination is made.