No description available.

No description available.

No description available.

This dissertation presents the results of studies of the generic concept of Senecio and the subsequent testing of the hypothes is: that many of the species of Senecio in Natal are congeneric with Senecio L. sensu stricto. The sample of taxa studied consisted of 87 Natal senecios, 5 Cape heterochromous senecios and 10 non-southern African senecios, including the type of the genus, S. vulgaris L. Also included in the study were 5 species from taxonomically closely related genera in the tribe Senecioneae and two senecios of uncertain taxonomic position. The phenotype of these taxa was investigated with respect to a large number of morphological and micromorphological characters (126) and the data obtained were analysed neurally and numerically. Aspects of the pollen micromorphology, of all the taxa studied, were also investigated using the scanning electron microscope. A review of the chemical complement of all the taxa studied. particularly with respect to terpenes and pyrrolizidine alkaloids, was also undertaken. Six characters were selected as being taxonomically significant with respect to elucidating the generic concept of Senecio. A further 31 characters and the aforementioned 6, were selected as .being taxonomically significant with respect to elucidating the interrelationships of the Natal senecios and all the senecios studied. The generic concept of Senecio has been re-circumscribed and the generic status of each of the senecios studied has been tested according to this concept of Senecio sensu Vincent. In the light of my concept of Senecio, the following species are excluded from Senecio sensu Vincent: S. barbertonicus Klatt, S. cissampelinus (DC.) Schultz Bipontinus, S. fulgens (J.D. Hooker) Nicholson, S. helminthioides (Schultz Bipontinus) Hilliard, S. hockii De Wild. & Muschl., S. medley-woodii Hutchinson, S. radicans (L.L) Schultz Bipontinus, S. syringifolius O.Hoffm., S. tamoides DC., S. transvaalensis Bolus and S. viminalis Bremekamp. Senecio brevilorus Hilliard, S. seminiveus Wood & Evans and S. tanacetopsis Hilliard are considered to be peripheral to Senecio s. str. sensu Vincent, and are included in Senecio s. lat. sensu Vincent. The hypothesis regarding the generic status of the Natal senecios has been accepted, subsequent to the circumscription of Senecio s. str. sensu Vincent. Estimates of the phenetic affinity of all the members of Senecio sensu stricto sensu Vincent, included in this study, have been made. The majority of the Natal senecios, while clearly being members of Senecio s. str. sensu Vincent, are distinct from virtually all the Cape and non-southern African senecios studied. Many of the non-yellow (purple) Natal senecios form clearly allied groups which are distinct from the groups (clusters) composed of yellow senecios. The taxonomic position of several taxa is questioned, in the light of the cluster analyses. The evidence from the palynological studies neither contradicts nor supports the proposed infrageneric interrelationships, with respect to the Natal members of Senecios. str. sensu Vincent. The evidence also neither contradicts nor supports the proposed interrelationships between the Natal, the Cape and the non-southern African members of Senecios. str. sensu Vincent. The terpene and pyrrolizidine chemistry of many of many of the senecios studied is characterised by the presence of furanoeremophilanes. Eremophilanes also occur and are particularly associated with a number of non-yellow (purple) senecios. Pyrrolizidine alkaloids are not ubiquitous amongst the senecios studied, while some senecios appear to only synthesise pyrrolizidine alKaloids. The review of the errpene and pyrrolizidine chemistry of the senecios investigated, illustrates how our knowledge at or near the level of analytic characters is far from complete. However, we have definitely progressed from the synthetic level of character use. Nevertheless, the relationships between the members of Senecios. str. sensu Vincent, could not be evaluated in the light of the individual chemical complement of terpenes and pyrrolizidine alkaloids, because of a lack of information. An hypothesis of the chemical evolution within the Senecioneae is tested with in Senecios. str. sensu Vincent . Before any taxonomic changes are made to t he current composition of Senecio L., the concept of Senecio L. s. str. sensu Vincent, needs to be tested against a far wider sample of the genus. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1984.

Thesis (PhD (Botany and Zoology))--University of Stellenbosch, 1988. / Thesis (PhD (Botany and Zoology))--University of Stellenbosch, 1988. / Microfiche format 470 leaves single sided printed, preliminary pages i-vi and numbered pages 1-466. Includes bibliography and a list of figures. Copied with a Kodak 2400 DSV-E microfiche reader and digitized at 300 dpi (OCR), used Bizhub 250. / Please refer to full text to view abstract.

Berkheya Ehrh. is a genus of daisies in the tribe Arctotideae, subtribe Gorteriinae with over 80 species, most of which occur in southern Africa. This genus has centres of diversity associated with the montane regions of South Africa, including the Drakensberg Alpine Centre and Mpumalanga escarpment regions. Previous molecular and morphological studies indicate that Berkheya is paraphyletic. I present phylogenies based on nrDNA (ITS; Internal Transcribed Spacer) and cpDNA (psbA-trnH) sequence data analysed with Bayesian Inference and Parsimony. A phylogeny of combined cp- and nrDNA is also presented. These phylogenies are used to assess generic limits and to investigate the biogeographic patterns of Berkheya and its allies. The ITS phylogeny shows five well supported clades of Berkheya, two of which (Clades I and 2) are monophyletic summer rainfall region clades. Clades 3 to 5 are all paraphyletic winter rainfall clades with Cullumia occurring in the third clade, Cuspida occurring in the fourth and Didelta in Clade 5. Both psbA-trnH and combined phylogenies show concordance with the clade distribution shown in the ITS phylogeny. The ITS phylogeny was used to analyse correspondence with Roessler’s (1959) Series. It was found that the phylogeny showed considerable agreement with Roessler’s series, but B. bipinnatifida and B. spinosa of Series Speciosae may require some revision as well as taxa of monotypic series Cruciatae and Angustae. It is suggested that the latter series be merged with Cullumia species to form a single series. Some consideration should be taken to include Didelta species into Series Fruticosae as Didelta occurs in subclade 5b of Clade 5 with other Series Fruticosae taxa. Achene morphology was examined from species from each of the five clades to investigate the relationships of Berkheya and its allies, as well as to determine if there were any consistent achene features for each clade. The structure of surface cells on the fruit, the presence, absence and morphology of twin hairs as well as the structure of the pappus scales were found to be most useful in reflecting phylogenetic relationships within the clades. When compared with the clades of the ITS phylogeny, achene morphology showed consistent characters between taxa occurring in the same clades. As the most comprehensive study involving Berkheya, this phylogenenetic investigation was able to confirm that Berkheya is a paraphyletic genus with Didelta, Cullumia and Cuspida needing to be subsumed into Berkheya. An alternative classification is that taxa of Clade 5 could possibly be erected as an expanded Didelta, separate and sister to Berkheya.