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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Local, regional and monographic approaches to Cyrtandra (Gesneriaceae)

Bramley, Gemma L. C. January 2003 (has links)
A local revision reviewed collections of <i>Cyrtandra </i>from Mount Kerinci, Sumatra, recognising thirteen species, three of which are newly described: <i>C. aureotincta, C. patentiserrata, </i>and <i>C. stenoptera</i>. In a regional approach covering species from Peninsular Malaysia, nine species of <i>Cyrtandra </i>(Gesneriaceae) were recognised. Three [<i>C. cupulata, C. pendula, C. wallichii</i>] are common and occur more or less throughout the area; four [<i>C. dispar, C. gimlettei, C. patula, C. suffruticosa</i>] have more restricted distributions, and two [<i>C. lanceolata, C. stonei</i>] are local endemics. Three species and one variety are reduced to synonymy: <i>C. barbata</i> (= <i>C. cupulata</i>), <i>C. falcata </i>(= <i>C suffruticosa</i>), <i>C. rotundifolia </i>(= <i>C. pendula</i>), and <i>C. cupulata </i>var. <i>minor </i>(=<i> C. cupulata</i>). A phylogenetic approach involved a monographic revision of <i>Cyrtandra </i>section <i>Dissimiles. </i>Eleven species were reviewed, one of which is newly described (<i>C. fulvisericea</i>); one species, <i>C. producta </i>(= <i>C. trisepala</i>) is reduced to synonymy. Phylogenetic analyses of sequences of the internal transcribed spacer (ITS) region of 18-26S nuclear ribosomal DNA of <i>Cyrtandra </i>species from one community on Mount Kerinci, Sumatra, suggest that this community is an assembly of three distinct phyletic lineages, resulting from a gradual accumulation of diversity through time, although one lineage shows evidence of more recent, continuing speciation than the other two. Phylogenetic analyses of a second, larger sample of <i>Cyrtandra </i>ITS sequences suggest that Peninsular Malaysian <i>Cyrtandra</i> species have affinities with Sumatran and Bornean species, following previously recognised floristic patterns. These affinities can be explained historically, as periods of lower sea levels of the Pleistocene exposed land bridges between the Malay Peninsula, Sumatra and Borneo. A smaller sample of <i>Cyrtandra</i> species was sequenced for the <i>trn</i>L-F region of the choroplast gene, and phylogenetic analyses recognised major groups represented in the ITS phylogeny, suggesting congruence between the ITS and <i>trn</i>L-F data, and that the ITS phylogeny is an approximation of true evolutionary history.

A global reassessment of the generic relationships in the bellflower family (Campanulaceae)

Eddie, William M. M. January 1997 (has links)
This study was undertaken to determine the phylogenetic relationship of the genera of the Campanulaceae and to discover the major factors determining the evolution of the family, particularly the origins of the higher taxa. It was also an attempt to utilise evolutionary data in order to produce a general purpose phylogenetic system of classification while simultaneously avoiding unnecessary nomenclatural changes or disturbances to patterns of overall similarity. An extensive introduction to the family is provided, dealing with morphology, ecology and geographical distribution as well as a detailed account of the historical classifications of the Campanulaceae and its global relationships. Some particular difficulties associated with patterns of variation encountered in the family Campanulaceae are outlined. Philosophical issues such as the historical treatment of the genus, generic concepts, homology and methodologies are extensively discussed. A pluralistic or eclectic approach was taken for the taxonomic analyses which involved the construction of five principal data sets (higher taxa, flowers and fruits, pollen, seeds, and molecular characters). Cytological and biogeographical data were also taken into consideration. Methodologies were varied, involving both phenetic and cladistic approaches and the problems of handling multiple data sets were discussed. A new phylogenetic classification of the higher taxa to the subtribal level of the Campanulaceae is presented and some guidelines for the recognition of genera are suggested. A general outline of the phylogenetic evolution of the family is given and the major factors which have influenced this evolution are discussed. Conservation measures and the areas for priority research are briefly outlined and an extensive list of literature citations is provided.

Cytotaxonomic studies in Muscari sensu Lato

Stuart, David Christopher January 1966 (has links)
No description available.

Molecular evolution of nuclear ribosomal DNA in Aeschynanthus and Streptocarpus (Gesneriaceae)

Denduangboripant, Jessada January 2001 (has links)
Molecular phylogenetics using internal transcribed spacer (ITS) sequences of 50 <i>Aeschynanthus </i>species was carried out using PCR cloning and RNA secondary-structure analysis techniques to help solve ITS intra-individual sequence variation problems in this genus. It is suggested that intra-individual variation in <i>Aeschynanthus</i> is the result of low molecular drive and the clone variation, although persistent, is found not to predate the divergence of <i>Aeschynanthus </i>species. RNA secondary-structure analysis reveals an insertion/deletion hotspot in the ITS2 sequences that is difficult to align, especially on the terminal part of arm 1 which is probably functionally superfluous. By contrast the base of the arm is relatively conserved and may function as an exonuclease recognition site. The phylogeny of <i>Aeschynanthus</i> reveals two major clades with different but overlapping geographic distributions: one occurs primarily in mainland SE Asia and the other in Malesia. This pattern is interpreted as indicating an ancient vicariance event followed by dispersal and plate fusion. The phylogeny also reflects the classification based on seed testa and seed appendage morphology; that is, clade I has some species of section <i>Microtrichium</i> forming a basal group with sections <i>Haplotrichium</i> sens. str., a putative section <i>X, Diplotrichium, </i>and <i>Polytrichium</i> being polyphyletic or paraphyletic, and clade II has section <i>Aeschynanthus</i> nested within the paraphyletic, basal <i>Microtrichium.</i> In <i>Streptocarpus</i>, a length difference between ITS2 of <i>S. dunnii </i>and <i>S. rexii</i> rDNA was used as a genetic marker to study the inheritance of rDNA in hybrids between the two species. The <i>Streptocarpus</i> rDNA gene is found to have additive inheritance without any detected recombination and there are apparently two rDNA loci. A PCR silent allele was detected as a band-intensity difference in <i>S. dunnii</i> ITS2. This phenomenon was reproducible and persistent in backcrosses. I suggest that an rDNA pseudogene is possibly present as an allele at one locus of <i>S. dunnii.</i>

Taxonomy and adaptive radiation of the Pnigma brome-grasses of Europe

Fraile Martin, Carmen January 1994 (has links)
Perennial species of <I>Bromus </I>(Gramineae) embracing section <I>Pnigma </I>in Europe were investigated. Four groups were compared as a working hypothesis. The objective of this research was twofold: first, to make a formal taxonomic assessment of all the putative taxa and second, to contribute to the understanding of the evolutionary trends occurring among them. In the most recent taxonomic account of this group in <I>Flora Europaea </I>(Smith 1980), 9 species and 8 subspecies were recognised. The final view of the relationship amoung different taxa can be summarised as 24 taxa, 5 species and 19 subspecies. New taxa or combinations were reported, <I>B. parilicus, B. caprinus, B. condensatus </I>subsp. <I>microtrichus, B. condensatus </I>subsp. <I>moellendorffianus, B. riparius </I>subsp. <I>macedonicus, B. cappadocicus </I>subsp. <I>crassipes, B. pannonicus </I>subsp. <I>vernalis, B. erectus </I>subsp. <I>montenegrinus, B. erectus </I>subsp. <I>longiflorus, B. erectus </I>subsp. <I>laxus, </I>and <I>b. erectus </I>subsp. <I>aurouzensis </I>(the latter being a novel subspecies in <I>Pnigna </I>brome-grasses). Several techniques were brought to bear on the problems including: micro and macromorphology, anatomy, cytology, taximetric analysis, as well as the formal herbarium study. Significant results were obtained. The chromosome counts here reported agreed with other researchers' work. The intuitive view of taxonomy of the taxa studied clashed to some extent with the results obtained from the taximetric analysis, probably because of the limited amount of information manipulated by the computer. Nevertheless, greater confidence was felt in the "intuitive" classification than in those generated taximetrically. Research on sheath morphology was also carried out. Different kinds of sheath (used as states of a pivotal taxonomic character) were shown to have different functional characteristics. Thus they may be pivotal characters in explaining the evolutionary divergence of different species groups.

Molecular markers in conservation genetics : chlorolast DNA variation in natural Scottish Pinus sylvestris L

Helgason, Thorunn January 1993 (has links)
Scottish <I>P. sylvestris </I>populations have been extensively researched, using monoterpene and isozyme markers, but differentiation among populations is too low to identify origins or gene flow. Protocols were developed for the analysis of chloroplast DNA (cpDNA) Restriction Fragment Length Polymorphisms (RFLP) in <I>P. sylvestris </I>to determine whether cpDNA markers could be used for these purposes. Nine populations from throughout the range of pine in Scotland were sampled. Two individuals from each of these populations were surveyed using seven restriction enzymes and 13 probes from <I>P. contorta, </I>a total of 91 probe/enzyme combinations. The cpDNA genome of <I>P. sylvestris </I>was found to be about 119 kilobase pairs in length. 100% of the length of the genome was sampled, and 0.52% of the sequence length. No variation was found in any individual. These results were compared with a survey of <I>P. sylvestris </I>from China, Sweden and Turkey. There is no evidence that the cpDNA genotype of Scottish pine differs in any way from these varieties, suggesting that the cpDNA genome of <I>P. sylvestris </I>is homogeneous over a large part of the species' range. A survey of 191 individuals for 1 probe/enzyme combination revealed one variant individual, which appeared to be heteroplasmic for two cpDNA haplotypes. It was not possible to determine whether this was due to biparental inheritance of somatic mutation within that individual. The implications of these results for further research on the structure and inheritance of cpDNA in gymnosperms, the use of cpDNA as a genetic market in <I>P. sylvestris,</I> and the conservation of Scottish populations of this species are discussed. Finally, it is suggested that an increased collaboration between molecular biologists and ecologists is the best way to approach studies using sophisticated molecular techniques to measure genetic diversity in natural populations. In this way, the potential of this approach to improve the management of genetic resources can be fully realised.

Taxonomic studies in the Zingiberaceae, with special reference to vegetative characters

Olatunji, Olanrewaju Adebayo January 1970 (has links)
No description available.

A systematic study and phylogenetic investigation of the genus Berlinia (Caesalpinioideae: Leguminosae)

Mackinder, Barbara January 2006 (has links)
<i>Berlinia</i> is here enumerated as comprising 20 species, of which four were discovered and described during the course of the study. The existence of another new species is postulated. Red data assessments made according to IUCN categories show that ten species qualify for a category of threat, eight are Vulnerable, one is Endangered and one is Critically Endangered. The genus is almost exclusively west and west-central African, with a centre of diversity in coastal Gabon. A single species is confined to coastal East Africa. Typically, <i>Berlinia</i> species are trees of lowland forest including swamp and gallery forest formations. Separate phylogenetic analyses of nucleotide sequence data from the <i>trn</i>L region and <i>psb</i>A-<i>trn</i>H regions of the chloroplast confirmed that <i>Berlinia</i> was a member of tribe Macrolobieae and combined analyses of the two regions showed <i>Isoberlinia</i> and <i>Anthonotha</i> to be its closest relatives. <i>Berlinia</i> species were placed into two major clades. One clade contained species better able to tolerate relatively dry conditions than the other, had longer branches, was better resolved and better supported than the other clade, which was composed of eight of the ten most hygrophilous species in the genus, and had shorter branches with poor resolution. The short branches of the “wetter clade” indicate a significant proportion of <i>Berlinia</i> diversity is of recent (Pleistocene) origin. ITS data indicated that B. <i>confusa</i> as currently circumscribed may be a polyphyletic assemblage of two or more cryptic species. Within the long-branched clade, B. <i>orientalis</i>, the sole east African species was sister to the remaining species and may be a relic of a previous continuous west-east forest cover which was disrupted by the late Miocene aridification of Africa that followed the closure of the Tethys Sea, and the subsequent uplift of the central African Plateau.

Studies on some British species of Atriplex L

Hulme, Barbara A. January 1957 (has links)
No description available.

Taxonomic studies in the Cruciferae of the Near East

Dudley, Theodore R. January 1963 (has links)
No description available.

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