Masters Degrees (Botany and Zoology)

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Browsing Masters Degrees (Botany and Zoology) by browse.metadata.advisor "Bellstedt, D. U."

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    An assessment of the subgeneric classification of Zygophyllum (Zygophyllaceae) in Southern Africa : evidence from noncoding trnL-trnF chloroplast DNA sequences
    (Stellenbosch : Stellenbosch University, 2001-04) Makwarela, Azwimpheleli M.; Bellstedt, D. U.; Dreyer, L. L.; Marais, E. M.; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: Sequence data from the intron and the spacer of the trnL-F chloroplast DNA region were used to study the phylogenetic relationships of the genus Zygophyllum L. (Zygophylloideae: Zygophyllaceae) in the southern African region. The chloroplast DNA was extracted from both herbarium and silica-gel dried material. Closely related genera, i.e. Augea Thunb., Fagonia L. and Tetraena Maxim. within the subfamily Zygophylloideae and more distantly related genera Seetzenia R.Br. ex Decne and Tribulus L. were used as outgroups. Sequences revealed length variation mainly due to the presence of indels (insertions and deletions). Phylogenetic analysis using parsimony revealed two distinct lineages for southern African members of Zygophyllum, corresponding to the proposed subgeneric classification (Van Huysteen 1937; Van Zyl 2000). There is a strong monophyly support for the sections within the subgenus Agrophyllum (Neck.) Endl. However, the transference of the monotypic section Grandifolia Engl. from subgenus Zygophyllum to Agrophyllum is not confirmed, because material of Z. stapffii Schinz. was not available. Despite the morphological evidence for the subdivision of the subgenus Zygophyllum, the molecular data did not confirm the monophyly for its sections. This could be the result of biased sampling, since all the species used in the analyses, except Z. cordifolium L.f. and Z. morgsana L., belong to section Capensia Engl. The trnL region data support the transfer of the mono typic section Morgsana Huysst. from subgenus Agrophyllum to subgenus Zygophyllum. The molecular data also seem to have implications for the biogeography of Zygophyllum. The southern African Agrophyllum representatives are related to East African and Middle East Zygophyllum species, whereas the southern African subgenus Zygophyllum members are closely related to Australian Zygophyllum species.
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    A molecular phylogenetic assessment of Oxalis L. section Angustatae subsection Lineares using trnL-trnF sequence data
    (Stellenbosch : Stellenbosch University, 2003-03) Oberlander, Kenneth; Dreyer, L. L.; Bellstedt, D. U.; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: The phylogenetic relationships and taxonomic status of South African Oxalis L. species are highly unresolved, both regionally and with regard to precise placement within the genus as a whole. Studies based exclusively on morphological and palynological characteristics have hitherto proved only partially successful in resolving natural groupings among the indigenous taxa of the region. Recent studies involving a few native taxa have indicated the plastid trnL-trnF non-coding DNA region as useful for the purposes of reconstructing phylogenetic relationships within the genus. The present study addressed the taxonomic monophyly and relationships of the highly unresolved section Angustatae subsection Lineares, using DNA sequence data. The phylogenetic reconstruction of southern African Oxalis species renders five of the subsections of section Angustatae sensu Salter (1944) polyphyletic, three of them conclusively so. The members of subsection Lineares are split between three clades, two of them with strong bootstrap support. None of these three clades consists exclusively of species of subsection Lineares. Likewise four of the seven assemblages of related taxa within subsection Lineares sensu Salter (1944) are not retrieved as monophyletic. Pollen data sensu Dreyer (1996) supports the clades retrieved in this study, whereas very few morphological characters could be plotted as potential synapomorphies for these clades. The resultant phylogenetic reconstruction thus supports palynological data of this subsection, and indicates the urgent need for a revision of the current morphological classification of Salter (1944).
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    Molecular phylogeny, radiation patterns and evolution of life-history traits in Ursinia (Anthemideae, Asteraceae)
    (Stellenbosch : Stellenbosch University, 2008-12) Swelankomo, Nonkululeko; Mucina, Ladislav; Bellstedt, D. U.; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    Sequence data from the Internal Transcribed Spacer (ITS) of the nuclear ribosomal DNA were used to study the phylogenetic relationships in the genus Ursinia Gaertn. (Asteraceae, Anthemideae) in the southern African region. Closely related genera, i.e. Cotula L., Osteospermum L. and Agoseris Raf., were used as outgroups. The study also included maximum parsimony and principal component analyses. The taxa within the genus Ursinia had previously been classified into two subgenera, Ursinia and Sphenogyne R.Br., mainly on the basis of distinct cypsela characters. The maximum parsimony, principal component and the phylogenetic analyses revealed two subgenera, corresponding to the existing subgeneric classification. Principal component analysis shows that the pappus, the number of pappus bristles and the colour of the cypsela are the most informative characters. However, the low number of phylogenetically informative characters of the ITS sequences, the poor resolution in the consensus tree, and low branch support values indicate that the ITS data contain weak phylogenetic signals. The low bootstrap values for many nodes suggest that one should be cautious in using the ITS region alone to make final conclusions about the origin and evolution of taxa. In maximum parsimony analysis, the RI, CI and bootstrap values are low; principal component analysis values are also low. Furthermore, there is a lack of resolution in subgenus Sphenogyne. In the literature, Ursinia is divided into seven series but they were not retrieved as monophyletic in this study, probably because of short branch lengths in the phylogeny. Further molecular data are therefore required to be able to support or reject the present classification. Maximum parsimony, principal component and molecular analyses show that U. trifida f. calva Prassler and U. trifida (Thunb.) N.E.Br. f. trifida are not sister taxa, supporting the recognition of these two taxa as separate species. The Ursinia taxa from the summer-rainfall region are not monophyletic and are sister to a clade of Cape species. This supports a hypothesis that Ursinia migrated from the Cape into the Drakensberg which has been shown for a number of other Cape groups that have Drakensberg relatives.
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    Preliminary investigations into the phylogenetic relationships in the genus Erica L.
    (Stellenbosch : University of Stellenbosch, 2006-12) Lester, Ntsikelelo Blessings; Bellstedt, D. U.; Dreyer, L. L.; University of Stellenbosch. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: Erica is a genus of about 860 species world wide, with 700 of these found in South Africa’s southwestern and southern Cape, making it by far the most speciose genus in the Cape Floristic Region. This poses a particular challenge in the construction of a molecular phylogeny of the genus. The choice of suitably variable gene regions is a crucial decision on which the successful phylogenetic reconstruction of this important genus is critically dependent. The aim of this project was therefore to determine which DNA regions, both chloroplast and nuclear, would be sufficiently variable to give adequate informative characters that may be useful at the species level phylogenetic reconstruction. A subset of 30 species, representing the range of morphological diversity and pollinator preference within Erica, was selected for study. For each of these species the variability in eight chloroplast regions (trnL-F, matK, trnS-G, rps12- rpl20, psbAtrnH, trnC-D, rps4-trnT and trnT-L) and the nuclear ITS region was investigated. The psbA-trnH, trnC-D, rps4-trnT and trnT-L chloroplast regions were found to be problematic to amplify and to possess too few Parsimony Informative Characters to be of use in phylogenetic reconstruction. Four of the chloroplast regions, trnS-G, trnL-F, matK and rpS12-rpL20 and the nuclear ITS region could be amplified and sequenced with success. The ITS region was found to be reasonably variable, with the chloroplast genes showing less variability. The DNA extraction method employed showed itself to be of critical importance in the success of the study. Two DNA extraction protocols, both modified from the original Doyle and Doyle (1987) method, were tested. The one included double the amount of β-mercaptoethanol and Polyvinylpyrrolidone (PVP) and the other included an extended phenol: chloroform: isoamylalcohol step. These variables, together with the effectiveness of these methods on fresh vs. silica dried plant samples, were investigated to determine which of the two would yield high quantities and qualities of DNA and result in the best method for the extraction of DNA from Erica species.