Phylogeny of the genera Karroochloa, Merxmuellera and Schismus (Poaceae)
| dc.contributor.advisor | Spies, J. J. | |
| dc.contributor.advisor | Venter, H. J. T. | |
| dc.contributor.author | Malan, André Francois | |
| dc.date.accessioned | 2017-04-20T06:46:35Z | |
| dc.date.available | 2017-04-20T06:46:35Z | |
| dc.date.issued | 2002-12 | |
| dc.description.abstract | English: In southern Africa, the Poaceae include 194 genera and 967 species and intraspecific taxa, of which 329 are endemic, 847 indigenous and 115 naturalised (Gibbs RusseIl 1985). The classification, at present, is based on non-Kranz leaf anatomy and morphology of the spikelet (Clayton & Renvoize 1986). The Arundinoideae are difficult to characterize because they are heterogeneous with numerous isolated or weakly linked genera, whose relationships are highly conjectural. Most of the species of Merxmuellera and Karroochloa were previously part of the genus Danthonia (Nees & Essenbeck 1841, Steudel 1855, Durand & Schinz 1895). A number of species of Danthonia were recently allocated to the new genera Karroochloa and Merxmuellera (Conert & Turpe 1969, Conert 1971). For a long time, the genus Schismus was regarded as very closely related to Danthonia and more recently to the genus Karroochloa. One Schsimus species was originally assigned to Danthonia (Conert & Turpe 1974). The genus Karroochloa consists of four species, two perennials and two annuals. At present, 20 species are recognised in Merxmuellera, 18 are from southern Africa and two species are from the mountains of Madagascar (Barker 1994). The type species of Schismus, namely S. barbatus grows in southern Africa as well as in northern Africa and Europe. The closely related species, S. arabicus also occurs in the Northern Hemisphere and the other three species in this genus are all endemic to South Africa. The high level of genetic variability allows the grasses to take advantage of new habitats (Ehrendorf 1980). In this investigation, the species M. stricta and M. disticha revealed wide distribution patterns which overlap and may indicate that these two species are of hybrid origin and, therefore, well adapted to a wide range of climatic conditions, soil types, rainfall and altitude. In the genus Merxmuellera, morphologically distinct groups of species can be identified. The genera Karroochloa and Schismus form monophyletic groupings and the distance data indicates that morphologically, Schismus lies between Merxmuellera and Karroochloa. Previous cytogenetic studies have indicated that the genus Merxmuellera has basic chromosome numbers of six and seven (Spies et al. 1990). In this investigation no indications of a basic chromosome number of seven was found and Merxmuellera is thus considered to have a basic chromosome number of six. This genus reveals high ploidy levels that indicate an old polyploid complex was dealt with. In the case of the other two genera Karroochloa and Schismus young polyploid complexes were dealt with. Only diploids were studied although there are reports on polyploids (Spies & Du Plessis 1986b, 1988). The chromosome behaviour indicates that M. stricta and M. disticha could be of hybrid origin. Embryo sac studies of nine species indicate that all these species are of the Polygonum-type and that Merxmuellera indicates a variety of embryo sac formations. Karroochloa, Merxmuellera and Schism us can be distinguished clearly on embryo sac structure. The peR based RAPD procedure was applied to resolve and investigate the three genera and their species. A strong relationship between the Merxmuellera species, M. ruie, M. decora and M. lupulina was clearly illustrated by the RAPD data. The ITS analysis indicated conflicting clustering of some species as well as expected clustering of other species. Ultimately the following argument is applicable: gene trees may not necessarily represent species trees (Doyle 1992). In this study the percentage lacking data in the combined analysis was too large to be used in the combined analysis. Therefore all the data sets were analysed separately and then compared to each other to make the final conclusions in this thesis. The close relationships between M. ruie, M. decora and M. lupulina are evident. Therefore, it is suggested that the three species should be combined into one species and be regarded as a polyploid complex, rather than three separate species. It is clear that all the summer rainfall Merxmuellera species are related and the most practical systematic treatment appears to be upholding only two species namely M. stricta and M. disticha. The validity of the species S. pleuropogon must be investigated because only one specimen, the type specimen, was collected and described by Stapf (1916) and no further specimens were found. Therefore, S. pleuropogon may have become extinct or it may have been a once-off hybrid. Although the genus Karroochloa consists of four species, the final analysis indicates that these species are very closely related and that the annual status of K. schismoides should be carefully investigated. Such an investigation will indicate whether Karroochloa includes four of three species. | en_ZA |
| dc.description.abstract | Afrikaans: Die Poaceae bestaan uit 194 genera en 967 spesies en intra spesifieke taksa in suiderlike Afrika. Van hierdie spesies is 329 endemies, 847 inheems en 115 genaturaliseer (Gibbs Russeil 1985). Die klassifikasie berus tans op nie-kransige blaaranatomie en morfologie van die blompakkie (Clayton & Renvoize 1986). Die Arundinoideae is 'n moeilike groep om te identifiseer, aangesien daar verskeie geïsoleerde en swak gekoppelde genera bestaan waarvan die verwantskappe onder verdenking is. Meeste van die spesies in die genera Merxmuellera en Karroochloa was voorheen in die genus Danthonia gegroepeer (Nees & Essenbeck 1841, Steudel 1855, Durandt & Schinz 1895). Van die spesies is of hergroepeer, of nuut ingesluit in die genera Merxmuellera en Karroochloa (Conert & Turpe 1969, Conert 1971). Die genus Schismus is deurentyd as naverwant aan die genus Danthonia en onlangs aan die genus Karroochloa beskou (Conert & Turpe 1974). Die genus Karroochloa bestaan uit vier spesies waarvan twee eenjarig en twee meerjarig is. Op die oomblik is daar 20 spesies bekend in die genus Merxmuellera waarvan 18 spesies in suider-Afrika, en twee in die berge van Madagaskar voorkom (Barker 1994). Die tipe spesie van die genus Schismus, naamlik S. barbatus kom in suider-Afrika en in noord-Afrika sowel as Europa voor. Die naverwante spesie S. arabicus, kom net in die noordelike halfrond voor, terwyl daar nog drie spesies van die genus is wat endemies tot suider- Afrika is. Die hoë vlak van genetiese variasie bevoordeel die grasse in die benutting van nuwe habitatte (Ehrendorf 1980). In hierdie studie het twee spesies wat ondersoek is, nl. M. stricta en M. disticha 'n wye verspreiding getoon. Hierdie verspreiding is 'n aanduiding dat ons moontlik met basters te doen het wat goed aangepas is vir 'n wye verskeidenheid van klimaatstoestande, grondtipes, reënvalomstandighede en verskeie hoogtes bo seespieël. Die genus Merxmuellera toon verskeie morfologiese groeperings. Die genera Karroochloa en Schismus het elk 'n monofiletiese groep gevorm en die afstandsdata het aangetoon dat Schism us morfologies tussen die genera Karroochloa en Merxmuellera lê. Vorige genetiese studies het aangetoon dat die genus Merxmuellera 'n basiese chromosoomgetal van ses en sewe het (Spies et al. 1990). In hierdie studie is geen aanduidings van 'n basiese chromosoomgetal van sewe gevind nie en daarom word aangeneem dat Merxmuellera slegs ses as basiese chromosoomgetal het. In die geval van Karroochloa and Schism us is slegs diploïedes ondersoek alhoewel daar in die verlede melding gemaak is van poliploïede in die genera (Spies & Du Plessis 1986b, 1988) Kiemsakke van nege spesies is bestudeer en almal was van die poligonum-tipe. Die genus Merxmuellera het 'n verskeidenheid van kiemsakvorms aangetoon. Dit is ook uit die studie duidelik dat ons tussen die kiemsakke van Karroochloa, Merxmuellera en Schism us kan onderskei. Die RAPD peR-prosedure is van die metodes wat gebruik is om die drie genera te ondersoek. Die RAPD data het ook die noue verband tussen die spesies M. ruta, M. decora en M. lupulina aangetoon. Met die ITS analise is teenstellende groeperings, sowel as ooreenstemmende groeperings van spesies opgemerk. Die argument van Doyle (1992) geld dus naamlik dat 'n geneboom nie noodwendig die spesieboom ondersteun nie. 'n Geneboom kan dus nie onomstootlik die evolusionêre geskiedenis van spesies bewys nie (Doyle 1993). In die studie was afwesige data 'n te groot persentasie en dus kon die gesamentlike analise nie in die studie gebruik word nie. Die data is afsonderlik geïnterpreteer en is daarna in vergelyking met mekaar gebruik om die finale gevolgtrekkings te maak. Vanuit die studie is dit duidelik dat die spesies M. ruie, M. decora en M. lupulina, naverwant is en in een spesie gekombineer behoort te word en voortaan eerder as In poliploide kompleks behandel behoort te word. Dit is ook duidelik dat die Merxmuellera spesies van die somerreënvalgebied almal onderling verwant is en dat hier ook In samevoeging behoort plaas te vind met net twee spesies M stricta en M. disticha met talle variëteite. Daar moet ook indringend gekyk word na die geldigheid van die spesie, S. pleuropogan, aangesien slegs een eksemplaar deur Stapf (1916) versamel is wat die aanvanklike beskrywing gedoen het en nog geen verdere eksemplare versamel is nie. Die kans is dus goed dat die spesie uitgesterf het of In eenmalige baster kon gewees het. Alhoewel die genus Karroochloa uit vier spesies bestaan, is die spesies baie na aan mekaar verwant en moet die spesie K. schismoides ondersoek word om te bepaal of hulle werklik eenjarig is al dan nie. So In ondersoek sal aantoon of Karroochloa uit vier of drie spesies bestaan. | af |
| dc.identifier.uri | http://hdl.handle.net/11660/6128 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Karroochloa | en_ZA |
| dc.subject | Merxmuellera | en_ZA |
| dc.subject | Schismus | en_ZA |
| dc.subject | Phylogeny | en_ZA |
| dc.subject | Grasses -- Phylogeny | en_ZA |
| dc.subject | Grasses -- Cytogenetics | en_ZA |
| dc.subject | Thesis (Ph.D. (Plant Sciences (Genetics))-- University of the Free State, 2002 | en_ZA |
| dc.title | Phylogeny of the genera Karroochloa, Merxmuellera and Schismus (Poaceae) | en_ZA |
| dc.type | Thesis | en_ZA |