A research report submitted in partial fulfilment of the requirements for the degree of Master of Science in Environmental Science (Coursework and Research Report) to the Faculty of Science, University of the Witwatersrand, Johannesburg, 2017. / Various studies have been conducted on the determinants of herbaceous vegetation composition and structure in savannas, but there is still no consensus on the extent of the role played by each. This is particularly so for disturbed savannas in communal rangelands. This study aimed to investigate the relative influence of rainfall, catenal position and distance from village on composition and structure of herbaceous vegetation in communal rangelands of Bushbuckridge, Mpumalanga Province in South Africa. The study used pre-existing data collected in 2012 in 56 plots located across nine villages in three rainfall zones: Low (<600 mm), Medium (600-700 mm) and High (>700 mm). In each zone, the communal rangelands of three villages were sampled in upslope and downslope positions and across three distance (disturbance) categories of, 0-599 m, 600-1799 m and >1800 m relative to nearest villages. The composition-related measures investigated were: absolute and relative abundance of species present, species richness, Simpson’s Diversity Index and relative abundance of perennial and annual grasses, as well as categories of forbs whilst the herbaceous structure measures used were distance in meters measured along transect line to perennial grass tuft and grass basal cover. Both individual and interactive effects of the rainfall zone, landscape position, and distance from village on herbaceous composition and structure were investigated using bivariate and multivariate statistics. Both grass species richness and Simpson’s Diversity Index were significantly higher in the high rainfall zone than in the low and medium rainfall zones. Perennial grasses in all rainfall zones heavily dominated the herbaceous layer, with the mean percentage perennial grass contribution being lowest in the high rainfall zone whilst the low rainfall zone had the highest. The percentage composition of annual grasses was highest in the medium rainfall zone and lowest in the low rainfall zone whilst it was intermediate in the high rainfall zone. The mean distance to perennial grass, which is an index of density of perennial grass tufts, was significantly higher in the high rainfall zone than in the low rainfall zones. The mean percentage grass basal cover was higher in low rainfall zone than in high rainfall zone. The mean species richness in the upslope and downslope catenal positions was not significantly different which was contrary to what was expected. Mean Simpson’s Diversity Index was higher on the downslope position than on the upslope catenal position. The relative abundance of perennial grasses between the upslope and downslope catenal position was not significantly different. The proportion of perennial grasses was more than that of annual grasses and other life forms sampled. Neither mean distance to perennial grass nor basal cover differed significantly between catenal positions. It was established in this study that closest plots to villages had 22% more species than the plots between medium and far plots from the villages. Near the villages (0-599 m), the species richness was found to be higher than in the medium (600-1799 m) and (>1800 m) distance categories. The mean Simpson‘s Diversity Index in all distance (disturbance) categories were found to be not significantly different. There was no significant difference in the percentage of perennial grass among the disturbance gradient categories. The perennial grasses were consistently dominant over the annual grasses along the disturbance gradients. The distance to perennial grass indicated no difference across all distance gradients. Percentage basal cover decreased with increasing distance from settlements. The composition and occurrence of grass species were associated with different environmental gradients studied. There was significant interactive effect due to a combination effect of rainfall, topographical gradients and distance gradient on the distance to perennial grass. However, the mean distance to perennial was lower at distance and rainfall combination, though was not significant. The interactive effect on basal cover due to a combination effect of rainfall, catenal position and distance gradient was found to be not significant. Overall, the herbaceous composition and structure was more strongly impacted by rainfall zone than by catenal position. The herbaceous composition and structure was affected by disturbance gradient specifically on species richness and grass basal cover only, while there was no effect on Simpson’s Diversity Index, perennial grass percentage, and distance to perennial grass as measured along transect line. It was also established that there was association of species with environmental gradients. It is recommended that in future a multi-year study on the same variables that have been studied here be undertaken in order to establish long-term trends on the effect of the gradients on herbaceous vegetation. It must be ensured also that there be representativity of disturbance gradients samples when designing sampling programme. It will also be beneficial to establish the density per village or stocking rates of different villages and the management aspects of the stock and how it is related to herbaceous composition and structure. Such studies will provide further knowledge on the extent of human induced disturbance like grazing in the communal rangelands given a set of environment gradients. / LG2018

No description available.

Dissertation (PhD)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Twenty five years after the last major morphological revision, phylogenetic relationships were inferred on the basis of a new DNA dataset for the African orchid subtribe Disinae, which includes the large genus Disa and the small genus Schizodium. One nuclear gene region (ITS) and two plastid gene regions (trnLF and matK) were sequenced for 136 ingroup, representing 70% of all known Disinae species, as well as for 7 outgroup taxa. The combined data matrix contained 4094 characters and was analysed using parsimony and Bayesian inference. The generic status of Schizodium can no longer be supported, as it is deeply embedded within the genus Disa. Furthermore, the currently recognised subgenera do not reflect the phylogenetic relationships. Several of the currently recognised sections are monophyletic, others contain misplaced elements, while some are polyphyletic. These results necessitate a re-classification of the Disinae. A monotypic subtribe Disinae and a subdvision of Disa into eighteen sections is formally proposed. These sections are monophyletic, well-supported, morphologically distinguishable and are delimited to maximize the congruence with the previous classification. All currently known species are enumerated and assigned to sections. Likelihood optimisation onto a dated molecular phylogeny is subsequently used to explore the historical biogeography of Disa, as well as of three other Cape lineages (Irideae p.p., the Pentaschistis clade and Restionaceae), to find out where these lineages originated and how they spread through the Afrotemperate region. Three hypotheses have been proposed: (i) a tropical origin with a southward migration towards the Cape; (ii) a Cape origin with a northward migration into tropical Africa and (iii) vicariance. None of these hypotheses, however, has been thoroughly tested. In all cases, tropical taxa are nested within a predominantly Cape clade and there is unidirectional migration from the Cape into the Drakensberg and from there northwards into tropical Africa. Dating estimates show that the migration into tropical East Africa has occurred in the last 17 million years, consistent with the Mio-Pliocene formation of the mountains in this area. The same technique is then utilised to reconstruct the temporal occurrence of ancestral ecological attributes of the genus Disa. The first appearance of species in the grassland and savanna biomes, as well as in the subalpine habitat, are in agreement with the existing, reliable geological and paleontological information. This suggests that phylogenies can be used to date events for which other information is lacking or inconclusive, such as the age of the fynbos biome and the start of the winter rainfall regime in southern Africa. The results indicate that these are much older than what is currently accepted and date back to at least the Oligocene. / AFRIKAANSE OPSOMMING: Vyf-en-twintig jaar na die laaste groot morfologiese hersiening, is die filogenetiese verwantskappe van die Afrika orgideë subtribus Disinae, wat die groot genus Disa en die klein genus Schizodium insluit, in hierdie studie op grond van ‘n nuwe DNA datastel afgelei. Daar is van 136 binnegroep, wat 70% van alle bekende Disinae spesies verteenwoordig, sowel as sewe buitegroep taksa geenopeenvolgings van een nukleêre geen streek (ITS) en twee plastiedgeen streke (trnLF en matK) bepaal. Die gekombineerde data matriks het 4094 karakters bevat en is met die parsimonie en Bayesian metodes ontleed. Die generiese status van Schizodium kan nie hieruit ondersteun word nie, en is diep ingebed binne die genus Disa. Die huidiglik aanvaarde subgenera word ook nie deur hierdie filogenie ondersteun nie. Verskeie van die huidiglik herkende seksies is bevind om monofileties te wees, ander bevat verkeerd geplaasde spesies, terwyl ander polifileties blyk te wees. ’n Monotipiese subtribus Disinae en ’n onderverdeling van Disa in agtien seksies word formeel voorgestel. Dié seksies is monofilities, goed ondersteun, morfologies onderskeibaar en omskryf om maksimaal ooreen te stem met die vorige klassifikasie. Alle huidiglik bekende spesies word gelys en toegewys aan seksies. Waarskynlikheidsoptimalisering op ’n gedateerde molekulêre filogenie is dan gebruik om die historiese biogeografie van Disa te ondersoek, tesame met drie ander Kaapse groepe (Irideae p.p., die Pentaschistis klade en Restionaceae), om te bepaal waar hierdie groepe hulle oorsprong gevind het en hoe hulle na die “Afrotemperate“ streek versprei het. Drie hipoteses word voorgestel: (i) ’n tropiese oorsprong met ’n suidwaartse migrasie na die Kaap; (ii) ’n Kaapse oorsprong met ’n noordwaartse migrasie na tropiese Afrika, en (iii) vikariansie. Geen van hierdie hipoteses is egter vantevore deeglik getoets nie. In alle gevalle is bevind dat die tropiese taksa oorwegend binne ’n Kaapse klade gesetel is, en dat daar ’n eenrigting migrasie is van die Kaap na die Drakensberge en van daar noordwaarts na tropiese Afrika. Dateringsskattings toon dat die migrasie na tropiese Oos-Afrika in die laaste 17 miljoen jaar plaasgevind het, ooreenstemmend met die Mio-Plioseen vorming van die berge in die area. Dieselfde tegniek is daarna aangewend om die temporale voorkoms van voorvaderlike ekologiese eienskappe van die genus Disa te rekonstrueer. Die eerste voorkoms van die spesies in die grasveld en savanna biome, sowel as die subalpiene habitat, is in ooreenstemming met bestaande, betroubare geologiese en paleontologiese informasie. Dit suggereer dat filogenieë gebruik kan word om gebeurtenisse te dateer waarvoor daar informasie ontbreek of nie beslissend is nie, soos die ouderdom van die Fynbos bioom en die begin van die winterreënval stelsel in suider-Afrika. Die resultate dui daarop dat dit heelwat ouer is as wat tans aanvaar word en terugdateer na ten minste die Oligoseen.

Call number: LD2668 .T4 1984 L39 / Master of Arts

This thesis addresses the consequences of the last glaciation on the distribution and genetic diversity of arctic flora. The principal aim is to infer the full-glacial and postglacial migrational history of Dryas integrifolia M. Vahl. (Rosaceae) from the intraspecific phylogeny of cpDNA haplotypes along with pollen and macrofossil distribution data. The results suggest that four refugia existed during the last glaciation and that each served as significant sources of recolonization when the ice retreated. The two most important refugia are located in the northwestern Arctic (Beringia and the High Arctic), with two other refugia located southeast of the ice sheet and along the coastal regions of the eastern Arctic. High genetic substructure among populations is likely attributable to past vicariance and recent recolonization events, whereas high local diversity is probably indicative of recolonization from several sources and high gene flow in recent time.

The Great Escarpment forms a semi-continuous mountain system 5 000 km long, stretching from Angola in the north-west, south through Namibia, and into western, southern and eastern South Africa, including Lesotho and Swaziland. It is composed of a wide variety of geological suites but is unified in representing the edge of the African plateau and the passive Gondwanan continental margin. The Great Escarpment falls into all major climatic zones on the subcontinent, is a repository of palaeo- and neo-endemics, hosts more than half of southern Africa‟s centres of plant endemism, and has a rich suite of endemic fauna. In addition, the Great Escarpment is believed to be both a refugium and corridor for biological diversity. Despite the biological richness of the Great Escarpment, research to date has been fragmented and many sections of the Great Escarpment have not been studied. The aim of this study is to contribute to research on the Great Escarpment by undertaking a detailed floristic study of the southern Great Escarpment (the Sneeuberg, Nuweveldberge and Roggeveldberge). Together these mountains comprise approximately 1 000 km (one fifth) of the Great Escarpment, and occupy a transition zone between the summer rainfall zone in the east and the winter rainfall zone in the west. They are also the sections of Great Escarpment most closely situated to the Cape Floristic Region (CFR) and would thus be involved in hypothesised migration routes for lineages that also occur further north through the Drakensberg Alpine Centre (DAC) to the East African mountain chain. Detailed fieldwork of the southern Great Escarpment was undertaken over a period of four years in all seasons. Approximately 8 000 specimens were collected. Particular emphasis was placed on areas that may represent refugia, i.e. the highest plateaux and peaks, mesic areas and cliff-lines. An overview of each mountain range, together with their endemic plant species and phytogeography, is provided. Approximately ten new species have been discovered during this study, two of which have been described to date. Numerous endemics only known from their types have also been rediscovered. The Sneeuberg is defined as a new centre of plant endemism on the Great Escarpment (endemism of 2.3%), and the role of the Boschberg and Groot-Bruintjieshoogde (part of the Sneeuberg) as a nexus for floristic migration routes is discussed. The Nuweveldberge is shown to have low endemism despite a floristic tally similar to the Sneeuberg, while the Roggeveldberge are confirmed to be the most endemic-rich section of the southern Great Escarpment. The field data collected was augmented by available data in taxonomic revisions, and floras for the Sneeuberg, Nuweveldberge and Roggeveldberge were compiled. In order to floristically compare the southern Great Escarpment with other sections of the Great Escarpment and the CFR, a database of some 12 000 taxa was created using available floristic data for the CFR, DAC and Great WinterbergAmatolas, together with the data collated for the Sneeuberg, Nuweveldberge and Roggeveldberge. These data were analysed using phenetic methods and Parsimony Analysis of Endemicity (PAE). The results indicate stronger linkages in the east, particularly between the Sneeuberg and Nuweveldberge, and between the Sneeuberg and the Great WinterbergAmatolas. The relationship of the Roggeveldberge with the rest of the southern Great Escarpment remains ambiguous. In order to refine notions of connectivity and migration routes, 19 well-sampled phylogenies were assessed for sister-taxon disjunctions to explore CFRGreat Escarpment connections. Palaeo-connectivity between the CFR and southern Great Escarpment is most strongly supported for the south-eastern (SE) connection, and less so for the north-western (NW) and Matjiesfontein connections. There is support for the current (or recent) use of these three connections from numerous species that occur on both sides of the connections. Results of these analyses indicate that the southern Great Escarpment is a palaeo-corridor, the functioning of which has been broken by the aridification of the Nuweveldberge since the Last Glacial Maximum (LGM). Floristic connectivity is strongest in the east, from the Nuweveldberge to the DAC, and is less so in the west between the Nuweveldberge and the Roggeveldberge a finding attributed to the transition from a reliable winter rainfall regime on the Roggeveldberge to an unpredictable moisture regime on the Nuweveldberge. The mountains of the southern Great Escarpment are thus a series of refugia from a previous moister, cooler climate and are a corridor between the eastern and western components of the Great Escarpment. The SE connection is the primary link between the CFR and the eastern Great Escarpment Afromontane region in southern Africa. The implications of this research are that accurate conservation assessments and Red Data listings for many of the previously poorly-known endemics can now be made, and appropriate conservation measures implemented. Climate change remains the primary threat to these endemics and montane taxa in general, while degradation of wetlands is the primary threat to the water catchment service provided by the southern Great Escarpment. Future detailed research on the Great WinterbergAmatolas and Stormberg and a comprehensive flora of the HantamRoggeveldberge will further enhance our understanding of the floristics of the southern Great Escarpment, and provide the necessary data for comprehensive GIS-based models of proposed climate change scenarios for local, regional and national conservation planning.

No description available.

The dispersal of plants with particular attention to the roles birds play as dispersal agents was studied in the southwestern Cape, South Africa from 1983 to 1985. The research was organized as ten inter-related studies, each with an independent data base. Each chapter focused on a different scale of plant dispersal processes ranging from regional assemblages of plant species to individual species. At the largest scale, the seven vegetation types commonly occurring in the southwestern Cape were examined for incidence of vertebrate-dispersed plants. Coastal Thicket and Afromontane Forest were found to be the richest in these species. The colonization of vertebrate-dispersed plants was examined in an artificially cleared area of Mountain Fynbos vegetation. Enhanced densities of vertebrate-dispersed species were found in areas where perches had been provided. The seasonal availability of vertebrate-dispersed species was found to be most continuous in Coastal Thicket vegetation. Fruit displays of vertebrate-dispersed indigenous plants were found to vary from those that were sporadic and inconspicuous, to those that were conspicuous and predictable, whereas those of alien plants were usually large and conspicuous. Avian use of these fleshy fruits in Coastal Thicket was examined and found to be proportional to their availability. A study of fruit presentation in relation to leaf number and stem thickness suggested that sessile, stem attached fruits have fewer local leaves at time of ripening than fruits which are presented in panicles. This may enhance accessibility and conspicuousness of stem attached fruits for dispersal by birds. Four autecological studies tested certain predictions arising from models developed to describe fruit/frugivore interactions. The dispersal of the alien Acacia cyclops seeds by the indigenous Black Korhaan Eupodotis afra suggested that successful fruit/frugivore relationships are not necessarily the product of reciprocal evolution. The study on Chrysanthemoides monilifera found that efficient dispersal systems are not limited to plants producing small quantities of lipid-rich fruits and to dispersal by obligate frugivores. The abiotic dispersal of Quercus robur was found to be efficient in relation to vertebrate-dispersal. The study on Protasparagus aethiopicus found that the morphology of fleshy fruits may also reflect attempts to overcome the effects of non-dispersing seed predators. 1It is concluded that a gradient from a predictable to unpredictable fruit availability provides a better basis for studying fruit/frugivore interactions than the coevolutionary models. previously presented.