Thesis (PhD (Botany and Zoology))—University of Stellenbosch, 2009. / The genus Oxalis forms a major part of the flora of southern Africa, in particular the Cape Floristic Region (CFR) at the southwestern tip of the continent, but the current taxonomy is outdated and ecological knowledge of the lineage is sadly incomplete. In this thesis I set out to address several aspects of Oxalis systematics that urgently require attention. Firstly, the current macro-morphological taxonomy requires phylogenetic testing, as it is acknowledged to be incomplete and artificial. I address this need by providing a DNA sequence-based phylogeny of three markers, using three different inference methods, for nearly three quarters of the indigenous species. This phylogeny confirmed both the monophyly of the southern African taxa, and the artificiality of the current classification system. It is congruent with previous sequence-based reconstructions of smaller groups of southern African Oxalis species, and with the palynological classification proposed for the genus. Secondly, previous phylogenetic work on the southern African members could not resolve basal relationships within the southern African clade. I attempt to address this problem by sequencing three extra chloroplast markers for a select group of taxa, followed by separate and combined (total evidence) molecular phylogenetic analyses. This approach did increase resolution at the base of the southern African lineage, but many clades still showed poor resolution and support despite the use of more than 7 000 bases of sequence data. Resolving these clades within the southern African Oxalis phylogeny remains a challenge, and should prove a fertile field for future research. Thirdly, the ages (and thus duration of presence) of many Cape plant lineages within the CFR are of major interest, given that the CFR represents a global biodiversity hotspot. The age of the genus in the Cape is estimated by analyzing combined sequence data for all sampled taxa under both a Bayesian Relaxed Clock and a semiparametric Penalised Likelihood method, using calibration points inferred from Relaxed Clock analyses of the entire order Oxalidales, for which fossil data are available. In an attempt to account for known problems with divergence time estimation, I explored the potential bias introduced by method used, marker genome source and different calibrations on the root. The results indicate substantial variation in the age of crown southern African Oxalis over a nearly twenty million year period, varying according to source data, calibration estimate and methodology employed in the reconstruction. Despite this major variability, all average estimates are older than iv 18 million years, which agrees with a growing body of evidence that there has been a gradual accumulation of floristic diversity in the CFR, rather than a rapid, recent burst of speciation. Fourthly, as the produced phylogenies conclusively show the artificial nature of the current taxonomy, I propose a new, almost completely different classification for southern African Oxalis taxa. Although a significant improvement, this classification is considered informal due to the complete disagreement between the old and proposed new taxonomies, poor resolution in some of the proposed lineages, and a need to confirm proposed groups (clades) with the identification of morphological synapomorphies. Potential synapomorphies for various clades are proposed and discussed, which should guide future research. Fifthly, the presence of bulbs in this genus is of great interest as a potential preadaptation for seasonally arid climates. The evolution of the bulbous habit in Oxalis is here explored for the first time. I address the sequence of major morphological character state changes leading to the suite of characters corresponding to the bulbous habit. The homology of basal leaf petioles, fleshy leaf scales and tunics is discussed, and it is shown that many bulb characters present in the southern African lineage are also found in the close relatives of this lineage, and are thus older than this lineage. The ecological and evolutionary implications of bulb geophytism in the CFR Oxalis are also discussed. Finally, I address certain taxonomic issues that arose during the course of this study. Co-authors and I describe the new species O. saltusbelli and O. ericifolia. We also clarify issues surrounding the tremendously variable group species O. flava and propose some nomenclatural changes and synonyms for related taxa. We also address the taxonomic position of the rare species O. purpurata, which was located too late in the course of this study to include in the main analyses.

Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The systematics of the southern African members of the genus Oxalis L. (Oxalidaceae) is in a state of flux. The bulbs of these species contain potential taxonomically important characters and therefore require detailed study (Salter, 1944). A pilot study assessed the homology of bulbs among southern African Oxalis species (Gebregziabher, 2001), and found that they are all homologous structures. This pilot study also emphasized the range of potentially informative characters from different bulb parts. The aim of the present study was to assess the taxonomic significance of bulb morphology in selected southern African Oxalis species. As far as possible, efforts were made to represent both the taxonomic (Salter, 1944) and palynological diversity (Dreyer, 1996) present in the genus. Detailed bulb morphological studies of 30 species of southern African Oxalis species revealed 41 potentially informative characters. Different bulb-types were identified based on these characters. Bulb-type affinities of taxa included in this study, as well as bulb descriptions from the pilot study (Gebregziabher, 2001), were discussed. Comparison with the current taxonomic classification (Salter, 1944), palynological classification (Dreyer, 1996) and a preliminary phylogeny based on the non-coding plastid trnL-trnF DNA region (Oberlander, 2003), were also made. Bulb morphology conflicted with the current taxonomic classification (Salter, 1944), but showed greater congruence with both the palynological groupings and the trnL-trnF based phylogeny. Based on this study, bulb morphology is found to be taxonomically significant. Further studies on the bulb morphology and anatomy of southern African Oxalis species are merited. Key words: bulb morphology, Oxalis, informative characters, basal plates, fleshy leaves, tunics / AFRIKAANSE OPSOMMING: Die sistematiek van die suider Afrikaanse lede van Oxalis L. (Oxalidaceae) is labiel. Die bolle van hierdie spesies sluit potensieel taksonomies belangrike kenmerke in, en behoort daarom in detail bestudeer te word (Salter, 1944). In Loodsstudie het die homologie van die bolle van die suider Afrikaanse Oxalis spesies ge-evalueer (Gebregziabher, 2001), en gevind dat hulle homoloë strukture is. Resultate van hierdie loodsstudie het ook die reeks van potensieel informatiewe kenmerke van verskillende boldele beklemtoon. Die doel van hierdie studie was om die taksonomiese belang van boImorfologie in geselekteerde suider Afrikaanse Oxalis spesies te ondersoek. Pogings is aangewend om, sover moontlik, beide die taksonomiese (Salter, 1944) en die palinologiese (Dreyer, 1996) diversiteit van die genus in die studie in te sluit. Gedetailleerde bol-morfologiese studies van 30 suider Afrikaanse Oxalis spesies het 41 potensieel informatiewe kenmerke uitgewys. Gebaseer op hierdie kenmerke, is verskillende bol-tipes geïdentifiseer. Verwantskappe tussen die bol-tipes van die spesies ingesluit in hierdie studie, sowel as beskrywings van bolle volgens die loodsstudie (Gebregziabher, 2001), word bespreek. Vergelykings met die huidige taksonomiese klassifikasie (Salter, 1944), palinologiese klassifikasie (Dreyer, 1996) en In voorlopige filogenie gebaseer op die niekoderende plastied trnL-F DNA-streek (Oberlander, 2003) is ook getref. BoImorfologie weerspreek die huidige taksonomiese klassifikasie (Salter, 1944), maar toon groter ooreenstemming met beide die palinologiese groeperings en die trnL-F gebaseerde filogenie. Hierdie studie het bevind dat bolmorfologie van taksonomiese waarde is. Verdere studies op die bolmorfologie en -anatomie van die suider Afrikaanse Oxalis spesies word aanbeveel.

Thesis (PhD (Botany and Zoology))--University of Stellenbosch, 2010.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 5 uppsatser.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Only a limited number of systems involving anther-smut fungi have been studied, usually due to the economic significance of their crop plant hosts. A smut fungus of the genus Thecaphora has been discovered infecting Oxalis hosts in South Africa. This pathogenic fungus, Thecaphora capensis, produces dark-coloured spores in the anthers of host flowers, rendering it an anther-smut fungus. The host genus is the seventh largest plant genus in the Cape Floristic Region (CFR) and the largest geophytic genus of this region. Nine Oxalis species that host T. capensis have been identified across a wide distribution in the CFR of South Africa. A preliminary assessment of T. capensis infections of Oxalis was conducted in 2009, which provided a foundation for further research into the ecological and evolutionary consequences of hosting this fungus. In this study, a comprehensive host diversity assessment was conducted to determine the extent of infected Oxalis individuals within the CFR. Three new Oxalis host species for Thecaphora capensis were discovered. This brings the total number of known hosts to twelve. The morphological and reproductive effects of the fungus were assessed on two host species (O. incarnata and O. lanata) by comparing healthy and infected individuals of these species. Infection by Thecaphora capensis had a significantly negative effect on both of these factors. Host resources appear to be co-opted for fungal spore production, since floral morphological characters of infected individuals were reduced in size. Furthermore, infection by T. capensis ensured near-universal sterility in both hosts. Differences in floral characters and pollinator preferences for healthy Oxalis incarnata and O. lanata individuals from disease-free and diseased populations were compared to determine the evolutionary influence of Thecaphora capensis infections. It was shown that this pathogen can have a significant evolutionary influence on its hosts, showing its ability to shape flower size and pollinator activity in O. lanata, but not in O. incarnata. A need has therefore been identified to assess these evolutionary forces independently for each host and its pathogen before making erroneous assumptions for conservation practices. Plant pollinators play an integral role in plant fitness. Pollinator movements within a population are important when between-flower spore transfer by pollinators increases the likelihood of new infections. Pollinator movements may be influenced by host density and the frequency of diseased individuals, amongst other factors. Pollinators were found to mediate Thecaphora capensis spore transfers within diseased Oxalis populations. Host density and disease frequency affected the number of spores transferred under field and standardized conditions. More research is required to investigate confounding factors in these complex systems. This study highlighted the complexities of a fungal-plant-insect relationship, the evolutionary consequences of such fungal infections and the various factors influencing the likelihood of new infections. This research adds to the limited body of knowledge on multi-organismal interactions in the CFR and provides a base for more detailed future studies on this intriguing system. / AFRIKAANSE OPSOMMING: 'n Brandswam, wat deel is van die Thecaphora genus,is ontdek in 'n Oxalis blom waar dit die gasheer plant se blom gebruik om spore in te produseer. Die swam, Thecaphora capensis, produseer donker gekleurde spore in die helmknoppe van die blomme van gasheer plante, daarom word dit geklasifiseer as 'n brandswam van die helmknop. Die gasheer plante van die swam is deel van die genus Oxalis, die sewende grootste plant genus in die Kaapse Floristiese Streek (KFS) en die grootste geofitiese genus in die streek. Nege Oxalis species is al klaar identifiseer as gasheer plante van T. capensis. Hulle is versprei oor 'n groot area van die KFS van Suid Afrika. 'n Primêre ondersoek van T. capensis infeksies op Oxalis is in 2009 onderneem. Hierdie ondersoek het gelei tot meer vrae oor die sisteem en het 'n goeie fondasie geskep vir verdere navorsing rakende die ekologiese koste verbonde daaraan om as gasheer plant vir 'n swam op te tree. 'n Deeglike ondersoek is in die KFS aangepak om die Oxalis gasheer plante van die brand swam te identifiseer en om voort te bou op die basiskennis wat in die primêre ondersoek daargestel is. Drie nuwe Oxalis gasheer plante van Thecaphora capensis is ontdek. Die totale aantal gasheer plante staan nou op twaalf. Gesonde en geinfekteerde individuele gasheer plante is gebruik om die morfologiese en reproduktiewe effekte van die swam te toets in twee Oxalis spesies (O. incarnata en O. lanata). Die negatiewe gevolge om 'n gasheer plant van die brand swam te wees was duidelik toe gesonde en geinfekteerde individuele met mekaar vergelyk is. Dit kom voor asof gasheer plante se hulpbronne vir spoor produksie gebruik word, want hulle is morfologies kleiner en meestal steriel. Die evolusionêre effek van Thecaphora capensis op 'n populasie is getoets met gesonde individuele in populasies van twee Oxalis spesies. Blomkenmerke en insek bestuiwers van gesonde individue in gesonde en geinfekteerde populasies is ondersoek om die effekte van T. capensis op populasies te toets. Daar is suksesvol gedemonstreer dat swamme sterk evolusionêre kragte uitoefen, en die vermoë het om plantpopulasies te vorm en te verander, ofskoon nie in alle gevalle ewe sterk nie. Daarom is dit belangrik om die evolusionêre kragte vir elke gasheer plant en sy patogeen onafhanklik te assesseer, sonder om algemene aannames te maak in bewaringspraktyke. Plantbestuiwers speel 'n belangrike rol in die fiksheid van plante. Hulle kan hul fiksheid verbeter deur bestuiwers te lok met blomme en deur aspekte geassosieer met blomme. Die bewegingspatrone van plantbestuiwers is baie belangrik indien hulle helmknop-geproduseerde spore van brandswamme vervoer instede van stuifmeel, want dit vergroot die kanse vir nuwe infeksies. Die bewegingspatrone van plantbestuiwers word, onder andere, beinvloed deur die digtheid en frekwensie van geinfekteerde individue. Plantbestuiwers speel 'n belangrike rol in die vervoer van Thecaphora capensis spore in geinfekteerde Oxalis populasies. Die digtheid en frekwensie van geinfekteerde blomme het die vervoer van spore geaffekteer onder veld en gestandardiseerde kondisies, alhoewel baie veranderlikes so 'n komplekse natuurlike sisteem beinvloed. Hierdie studie beklemtoon die kompleksiteit van 'n fungus-plant-insek verhouding, die gevolge van so 'n interaksie en die verskeie faktore wat die waarskynlikheid van nuwe infeksies beinvloed. Tot dusver is daar 'n beperkte aantal sisteme soos hierdie bestudeer waarin 'n brandswam van die helmknop betrokke is, en die enkele beskikbare studies is onderneem meestal as gevolg van hulle ekonomiese effekte op landboukundig belangrike gasheer plante. Hierdie studie verteenwoordig 'n belangrike byvoeging tot die inter-organismiese studies in die KFS. 'n Holistiese ekologiese oorsig soos hierdie verskaf 'n belangrike basis vir toekomstige studies en bewarings- en bestuurspraktyke.

Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2005. / The family Oxalidaceae has a worldwide distribution, but is most common in tropical and subtropical regions. Oxalis L. is the largest genus of the family comprising ca. 800 of the 900 species. Oxalis species are annual or perennial herbs or rarely subshrubs or trees. The current study assesses on the taxonomic placement of O. furcillata Salter. Currently this species, comprising two varieties, O. furcillata var. furcillata and O. furcillata var. caulescens Salter, is placed in section Foveolatae. Members of this section have endospermous seeds and fleshy leaflets. However, both in terms of leaf morphological and seed characters the two varieties of this species appear to be misplaced within this section. In addition O. furcillata var. caulescens has a unique pollen type, different from both the typical variety and the rest of the section. Both lines of evidence thus suggest that O. furcillata var. caulescens may be misplaced within this section. The present study thus sets out to assess the placement of O. furcillata in general, and the placement of O. furcillata var. caulescens in particular. A multi-disciplinary approach was followed, which included analyses of macro-morphological (including LM and SEM analyses), biogeographical and palynological characters. The variability of quantitative characters was assessed using the STATISTICA 6.0 software package. Leaf dimensions, plant height, bulb length, petiole length and palynology showed sufficient differences between the two taxa to confirm the separate identity of these two varieties as separate species. O. furcillata var. caulescens was thus raised to specific status as O. caulescens (Salter) Bissiengou. The results suggest two different options in terms of the taxonomic placement of the species O. furcillata and O. caulescens. They can either remain in section Foveolatae, best placed near O. senecta and O. densa or may moved to the highly variable section Latifoliolatae. But retaining them within the section Foveolatae appeared to be the better alternative. The correct position will be established both through further morphological analyses and correlation to the trnL-F and ITS sequence-based phylogeny of the southern African members of Oxalis.

Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2005. / At present a proper systematic classification of the southern African members of Oxalis L. (Oxalidaceae) does not exist. The most recent and comprehensive revision of the genus based on macro-morphological characters is out-dated (published 60 years ago (Salter, 1944)). The external morphology of the flowers of the southern African Oxalis species is reasonably wellstudied, but little is known about the anatomy thereof. A pilot study of fruit and seed morphology and anatomy of nine selected southern African Oxalis species (Obone, 2003) already revealed some trends to demarcate two main groups. This confirmed the systematic value of some of the characters already proposed by Salter (1944). The aim of the present study was to assess the potential systematic value of fruit and seed morphology and anatomy of 32 Oxalis species. The selection was done such that the included species would represent the main sections proposed by Salter (1944), the pollen types proposed by Dreyer (1996) and the different clades revealed by the phylogenetic tree compiled by Oberlander et al. (2004). Although the species sampling was very low (20% of the southern African taxa), 35 potentially informative characters were identified in fruit and seed morphology and anatomy. These characters may be grouped into three character types, namely autapomorphic characters, randomly distributed characters and systematically informative characters. The first two character types were particularly useful in species-specific characterization. The third group of linked characters could be used to demarcate two major groups of species, those producing endospermous seeds and those producing exendospermous seeds. The three types of characters may prove to be taxonomically informative if more species-inclusive studies are performed. The cluster analysis strongly supported the demarcation of endospermous and exendospermous groups with 100% bootstrap support. Low bootstrap values were observed for subgroups within each of the major groups. This is probably due to low taxon sampling. Therefore clustering based on fruit and seed morphology should be considered with extreme caution within the two groups. Despite these limitations of sample size, fruit and seed morphological and anatomical characters have proven to be systematically informative at the infra-generic level.

La llegada de plantas exóticas fuera de su rango de distribución original y su posterior asentamiento en ecosistemas naturales no es una excepción en las Islas Baleares. En la actualidad tenemos 308 especies no nativas naturalizadas y subespontáneas que representan el 16% del total de la flora Balear. En esta tesis se ha evaluado el estado de la cuestión a nivel global y local. Se ha confeccionado el primer catálogo de flora introducida y se ha analizado cuales de ellas son más abundantes y peligrosas; así como también qué ecosistemas son más vulnerables a la introducción de éstas. También se ha profundizado en el conocimiento de dos de las especies exóticas más peligrosas en el litoral Balear: Carpobrotus edulis y C. affine acinaciformis. Se ha evaluado su influencia sobre la polinización, su tasa de crecimiento bajo diferentes escenarios ambientales, se ha confeccionado un modelo de crecimiento y se ha evaluado su impacto sobre la composición y estructura de las comunidades nativas. / L'arribada de plantes exòtiques fora del seu rang de distribució original i el seu posterior assentament a ecosistemes naturals no és una excepció a les Illes Balears. A l'actualitat tenim 308 espècies no natives naturalitzades i subespontànies que representen el 16% del total de la flora Balear. En aquesta tesi s'ha avaluat l'estat de la qüestió a nivell global i local. S'ha confeccionat el primer catàleg de flora introduïda i s'han analitzat quines d'elles són més abundants i perilloses; així com també quins ecosistemes són més vulnerables a la introducció d'aquestes. També s'ha profunditzat en el coneixement de dues de les espècies exòtiques més perilloses del litoral Balear: Carpobrotus edulis y C. affine acinaciformis. S'ha avaluat la seva influència damunt els vectors de pol·linització, la taxa de creixement a diferents escenaris ambiental, s'ha confeccionat un model de creixement, i s'ha avaluat el seu impacte damunt la composició i estructura de les comunitats natives. / The constant arrival of exotic plants into areas outside their original distribution range and further settlement in natural ecosystems is not an exception in the Spanish Balearic archipelago. At the moment we have 308 non native species (naturalized and casual), the 16% from the total Balearic flora. This thesis has evaluated the exotic plant problematic at global and local level. We have elaborated the first exotic plants list, its distribution and abundance, as well as its degree of impact on the more vulnerable environments. We went deeply into the knowledge of two very invasive plants along the coast of the Balearic islands: Carpobrotus edulis y C. affine acinaciformis. We have evaluated its influence over pollen transmission, its growth rate at different environmental conditions, we have too elaborated a non liner growth model and its impact on composition and structure in natural communities