Browsing by Author "Muasya, A Muthama"

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    Open Access
    Aspalathus and Podalyria legumes balance acquisition of phosphorus and nitrogen for growth in nutrient poor fynbos soils
    (2015) Maistry, Pravin Mark; Chimphango, Samson B M; Muasya, A Muthama; Valentine, Alex J
    Legume species nodulate and grow successfully in the Core Cape Subregion, a Mediterranean-climate ecosystem with fynbos vegetation found on infertile soils. The physiological mechanisms enabling tolerance of low availability of phosphorus (P) are yet to be reported in Cape legume species such as Aspalathus linearis and Podalyria calyptrata; species that demonstrated traits typical of plants from nutrient poor soils. In the three research chapters of the thesis, it was anticipated that low P supply would limit plant growth and increase expression of traits for P acquisition.
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    Conserving living landscapes: investigating the impacts of livestock grazing and assessing rangeland restoration potential in Overberg Renosterveld, South Africa
    (2021) Poulsen, Zoë Chapman; Chimphango, Samson; Hoffman, Michael Timm; Anderson, Pippin; Muasya, A Muthama
    Biodiversity is declining faster than at any other time in the Earth's history, driven mostly by land use change and degradation. Overberg Renosterveld, some of the most species diverse mediterranean type shrublands, are no exception with about 95% of their original extent lost to agriculture. Historically, large herds of indigenous grazing mammals roamed these landscapes. Today the Overberg's agricultural lands are fragmented by land cover change and divided by fences. In the contemporary landscape animals, largely domestic livestock, and plant resources are closely coupled, and overgrazing of remaining renosterveld fragments a significant threat, with potential to cause irreversible damage. The Conservation of Agricultural Resources Act (CARA) (Act 43 of 1983) states that farmers must not exceed the grazing capacity of the veld unless it is protected against deterioration and destruction, and that any land that is degraded or denuded must be effectively restored or reclaimed. Despite this legislation, there is little empirical research on the impacts of livestock grazing on renosterveld, as well as on restoration of overgrazed areas. It was the aim of this thesis to contribute to this gap in understanding. The thesis assessed the role of grazing by different livestock types, namely cattle and sheep, on biodiversity, the soil seed bank, and the restoration potential of renosterveld vegetation from resting the veld. The effect of livestock grazing by sheep and cattle on plant species richness and diversity and growth form diversity was assessed using Modified Whittaker plots and presented in Chapter 3. It was hypothesised that livestock grazing by cattle would have less effect on species richness and diversity and growth form diversity than sheep grazing and that both cattle and sheep grazing would lead to a reduction in species richness and diversity in comparison to renosterveld sites with a treatment of no grazing. Thirty sites where either no grazing has taken place or that have been grazed by cattle or sheep were selected with sites being evenly distributed between Eastern, Central and Western Rûens Shale Renosterveld. At each of the thirty sites, vegetation data were collected from a series of nested subplots of ten 1 m2 , two 10 m2 and one 100 m2 subplots nested within a 1 000 m2 plot. One soil sample was also collected from each 1 000 m2 plot to a depth of 10 cm for nutrient analysis. Findings revealed that sites grazed by sheep had significantly lower plant species richness (median richness = 29 species, mean Shannon-Weiner = 3.39) and diversity when compared to sites with a treatment of no grazing (median richness = 49 species, mean Shannon Weiner = 3.83). Sites with a treatment of no grazing had significantly higher richness of geophyte species (mean = 14.7) than sites grazed by cattle (mean = 7.0) and sheep (mean = 7.1) during the study. The results obtained were in line with the hypothesis that livestock grazing by sheep resulted in a reduction in species richness and diversity and vegetation cover in Overberg Renosterveld in comparison to sites where no grazing has taken place. Sites with a treatment of no grazing showed higher species richness and vegetation cover of non-succulent shrubs, annual forbs and perennial forbs than sites grazed by sheep. It was concluded that livestock grazing of Overberg Renosterveld by sheep needs to be done with care. This can be done by adopting a passive adaptive management approach. Here one set of management protocols can be developed and implemented and through science-based monitoring to inform management, these can be adapted as needed based on the key findings. Chapter 4 investigated ecosystem resilience and the restoration potential of Overberg Renosterveld through an exploration of its soil seed bank as a source for potential recovery. A glasshouse germination experiment investigated the effect of livestock grazing by cattle and by sheep in comparison with a grazing treatment of no grazing on the soil seed bank in Overberg Renosterveld, as well as the similarity between the standing vegetation and the soil seed bank. It was hypothesised that cattle and sheep grazing would reduce species richness, species diversity and growth form diversity in the soil seed bank in comparison with sites with a treatment of no grazing. Soil samples were collected from 30 sites that were also used in Chapter 3. The soil was then spread on top of a 6 cm layer of compost in seed trays, and smoke treated to enhance germination. Seedlings were assigned to growth form categories including forbs, geophytes, annuals, graminoids, succulent shrubs and nonsucculent shrubs and then identified to family, genus or species level. The results of the soil seed bank study were correlated with the vegetation results from Chapter 3 to examine the relationship between the standing vegetation and the soil seed bank. A total of 48% of taxa in the standing vegetation had seed present in the germinable seed bank. However, there were no differences in species richness, species diversity or number of individuals between grazing treatments. The results indicated that livestock grazing has a far less significant impact on the composition, species diversity and growth form diversity of the soil seed bank in Overberg Renosterveld than hypothesised. Instead, the results showed that there was a well-developed seed bank comprising mainly indigenous species with a variety of different growth forms including palatable grasses and shrubs. This indicates that Overberg Renosterveld vegetation has high restoration potential. Chapter 5 showed results on the effects of livestock grazing by cattle and sheep over time on plant species richness, diversity and growth form diversity in comparison with sites protected from grazing. Following collection of a baseline dataset, four years of follow up data were collected. A total of 22 fenced plots across Western, Central and Eastern Rûens Shale Renosterveld had a baseline dataset collected prior to being monitored on an annual basis over four years in grazed/ungrazed paired plots. Results on vegetation recovery from the fenced exclosures showed a significant increase in plant cover over time at sites that were not grazed. Mean species richness increased from 20.6 species to 25.4 species at sites with no grazing. Mean vegetation cover increased from 71% at T0 (the baseline time step) to 120% at T4 (the final time step) at the end of the study. Sites grazed by sheep had a decrease in vegetation cover over time each year from T0 to T4 from 75% to 50%. Results from a linear mixed model revealed that species richness between grazing treatments was significantly different at all time steps in the study. However, the significant differences were primarily due to comparisons between grazed sites and sites with a treatment of no grazing. Therefore, livestock grazing by sheep has a significant effect on renosterveld vegetation over time. Findings from this component of the study indicates that Overberg Renosterveld degraded by continuous heavy grazing has significant passive restoration potential by fencing renosterveld patches to facilitate more effective grazing management. Most of the renosterveld of the Overberg has been lost through habitat transformation for agriculture, and the future of that which remains is uncertain. This thesis affirms concerns around the impact of livestock grazing and shows the importance of improved ecological understanding around grazing management. Grazing by sheep was shown to cause greater impacts on renosterveld than other domestic livestock studied and is therefore a threat to renosterveld. These findings warrant closer attention to management practices around sheep grazing. However, the state of renosterveld soil seed banks offer considerable hope. Findings revealed a diverse indigenous seed bank, showing that renosterveld degraded by overgrazing has high restoration potential. Furthermore, fencing renosterveld to exclude livestock improves species richness and diversity over time. These findings highlight the need for caution when grazing renosterveld. However, where the damage has been done, the potential for recovery is high. Harnessing the soil seed bank in combination with excluding livestock grazing by fencing are effective tools in this critically endangered vegetation for achieving restoration and conservation goals.
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    Consistent phenological shifts in the making of a biodiversity hotspot: the Cape flora
    (BioMed Central Ltd, 2011) Warren, Ben; Bakker, Freek; Bellstedt, Dirk; Bytebier, Benny; ClaSZen-Bockhoff, Regine; Dreyer, Leanne; Edwards, Dawn; Forest, Felix; Galley, Chloe; Hardy, Christopher; Linder, H Peter; Muasya, A Muthama; Mummenhoff, Klaus; Oberlander, Kenneth; Quint
    BACKGROUND: The best documented survival responses of organisms to past climate change on short (glacial-interglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. RESULTS: Forty-three distributional and phenological shifts consistent with past climatic change occur across the flora, and a comparable number of clades underwent adaptive changes in their flowering phenology (9 clades; half of the clades investigated) as underwent distributional shifts (12 clades; two thirds of the clades investigated). Of extant Cape angiosperm species, 14-41% have been contributed by lineages that show distributional shifts consistent with past climate change, yet a similar proportion (14-55%) arose from lineages that shifted flowering phenology. CONCLUSIONS: Adaptive changes in ecology at the scale we uncover in the Cape and consistent with past climatic change have not been documented for other floras. Shifts in climate tolerance appear to have been more important in this flora than is currently appreciated, and lineages that underwent such shifts went on to contribute a high proportion of the flora's extant species diversity. That shifts in phenology, on an evolutionary timescale and on such a scale, have not yet been detected for other floras is likely a result of the method used; shifts in flowering phenology cannot be detected in the fossil record.
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    Cyperaceae tribe Cyperae : phylogenetic relationships and evolutionary patterns of diagnostic characters
    (2007) Dludlu, Meshack N; Muasya, A Muthama
    Phylogenetic relationships in Cyperus and allied genera in the tribe Cypereae (family Cyperaceae) have been reconstructed using parsimony and Bayesian analyses of a combined data matrix, which consisted of plastid DNA (rbcL, trnL-F intergenic spacer, and rps16), nuclear ribosomal DNA (internal transcribed spacer ITS) sequences and morphological data. From both analyses, tribe Cypereae were resolved into a very strongly supported clade (Posterior probability =98%; Bootstrap= 100%) characterised by the Cyperus-type of embryo and the absence of perianth segments. Cyperus sensu stricto is not monophyletic as currently resolved as several cyperoid genera are embedded within it. The Cyperoid clade splits into two distinct clades which are diagnosed by the Eucyperoid (C₃) and Chlorocyperoid (C₄) anatomy. The evolution of key morphological characters used to diagnose genera is discussed and genera whose classification needs to be revisited are highlighted.
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    Ecological influences in the biogeography of the Austral sedges
    (2016) Viljoen, Jan-Adriaan; Muasya, A Muthama; Verboom, George Anthony
    The biogeographic history of a species is a result of both stochastic processes such as dispersal and habitat filters that determine where a population with a given set of biological requirements can become established. In this dissertation, I examine the geographical and ecological distribution of the sedge tribe Schoeneae in conjunction with its inferred speciation history in order to determine the pattern of dispersal and the environmental factors that have influenced establishment. The biogeographic reconstruction indicates numerous transoceanic dispersal events consistent with random diffusion from an Australian point of origin, but with a bias towards habitats with vegetation type and moisture regime similar to the ancestral conditions of the given subgroup (open and dry habitats in the majority of cases). The global distribution of the tribe also suggests a preference for low-nutrient soils, which I investigate at the local (microhabitat) scale by contrasting the distributions of the tribes Schoeneae and Cypereae on the Cape Peninsula along soil fertility axes. The relationships between the phenotypic traits of species and their soil nutrient levels are also examined to determine whether the coexistence of the two groups in the Cape can be attributed to differences in nutrient accumulation behaviour or strategy of biomass allocation to roots or structural organs vs. leaves. No robust patterns were observed to identify such adaptations or to distinguish the tribes ecologically, a result that is at least partly due to low statistical power in the data set collected, which constrains the analysis to the use of simple models less able to detect subtle patterns in the ecological history of these sedges.
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    Phenotypic characterization of rhizobia isolates and distribution of Burkholderia rhizobia in the Core Cape Subregion
    (2016) Sinyanya, Kolisa Yola; Chimphango, Samson B M; Muasya, A Muthama
    The Core Cape Sub-region is well known for its low nutrient, low pH soils which harbour a variety of alpha and beta- Proteobacteria associated with a diversity of legume species. Soil bacteria are important for ecological processes and are influenced mostly by edaphic factors such as salinity and pH, and climatic conditions such as temperature. Recent studies have shown that Burkholderia form nitrogen fixing molecular associations with members of, among others, tribes Crotalarieae, Podalyrieae and Indigofereae. Selected rhizobia that included Burkholderia and Mesorhizobia, the large genera in the isolated rhizobia, and representing beta- and alpha- Proteobacteria were phenotypically characterized to determine the tolerances of Cape isolates to abiotic conditions. In a second study, glasshouse trapping experiments were conducted using legume species Podalyria calyptrata and Indigofera filifolia grown in 13 soils collected from diverse localities of the CCR, to determine the phylogenetic distribution of Burkholderia species in diverse soils of the CCR. To phenotypically characterize rhizobia isolated from a previous study, 29 isolates from representative legume-nodules of 13 different localities were grown under laboratory conditions. Isolates were phenotypically characterized for colony morphology, growth temperature, carbon source, salinity and pH tolerance. Morphological results revealed that majority of the tested isolates were white opaque, rod shaped and fast growing. Exceptions were found in colour where five strains produced a milky pigment, two were watery translucent; observation of bacteriod-shape among six symbionts; and one isolate grew after 7 days.
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    Phylogenetic inference and macro-evolutionary patterns in Ficinia Schrad. (Cyperaceae)
    (2009) Francis, Caitlynne Melanie; Muasya, A Muthama
    The genus Ficinia Schrad. has its centre of diversity in the Cape Floristic Region and phylogenetic relationships within this genus have not been fully studied representing a gap in the body of work on the Cyperaceae. Phylogenetic analyses provide strong support for the sister relationship between Isolepis and Ficinia in both parsimony and Bayesian analyses (BP = 96; PP = 1). Isolepis marginata consistently resolved as more closely related to the Ficinia clade than to the rest of the species in Isolepis. Ficinia undosa was positioned outside its own genus (as well as the entire FiciniaIsolepis clade) rendering the genus paraphyletic. This species appears to be more closely related to members of the Scirpus falsus-Scoipoides clade. As in previous studies, the New Zealand monotypic genus Desmoschoenus is resolved as a member of Ficinia and is closely allied with Ficinia pallens (BP=43, PP=0.56). Macroevolutionary reconstruction of characters such as life form and the presence of a gynophore disk revealed interesting patterns within the genus as well. Perennial habit is a synapomorphy for Ficinia and distinguishes it from the generally annual sistergenus Isolepis. Though a young genus when compared with Isolepis, Ficinia has radiated in the CFR quite rapidly following the -shift toward Mediterranean climate in this region. While support across the tree is quite low, due perhaps to the slow mutation rate among recent and rapidly radiated perennials, several relationships within m the genus are resolved with moderate nodal support.
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    Phylogenetic relationships and the effects of edaphic heterogeneity on the distribution of Wiborgia (Fabaceae) in the Greater Cape Floristic region
    (2016) Moiloa, Ntwai; Muasya, A Muthama; Chimphango, Samson B M
    The Greater Cape Floristic Region (GCFR) is divided into two subregions, the Core Cape Subregion (CCR) and Extra Cape Subregion (ECR), which are mainly characterized by Fynbos and Succulent Karoo biomes, and are recognized among global biodiversity hotspots. The soils in the ECR are mostly shale derived and richer in nutrients compared to the CCR which is characterized by nutrient-poor sandstone soils mainly from the Cape System. The Fabaceae (Leguminosae) is the second largest family in the CCR with a total of about 764 species (belonging to 43 genera, of which 83% of the species are endemic to the CCR), and sixth largest in the ECR with about 140 species currently recognised with 39.3% of these species endemic to the ECR. Wiborgia Thunb. is a legume genus made up of 9 perennial shrub species of height 0.5-3.0 metres, with distinct ascending to erect habit, which share morphological similarities with some Lebeckia, especially sect. Viborgoides currently referred to as Wiborgiella. The aim of this dissertation was to understand the evolution and biogeography of the genus Wiborgia in the GCFR. This involved (i) inferring phylogenetic relationships within the genus using multiple molecular markers and testing the monophyly and the support of Dahlgren's (1975) morphological subgeneric classification; (ii) determining nutritional characteristics of soils occupied by different Wiborgia species and compare them with sites where Wiborgia species have not been recorded to occur and testing whether Wiborgia species occupy habitats with similar nutrient concentrations; (iii) evaluating the potential of Wiborgia species to grow and nodulate in soils from within and outside distribution range and characterizing of rhizobia nodulating Wiborgia species in field and glasshouse conditions. Phylogenetic relationships in Wiborgia were inferred using multiple molecular markers (ITS, rpl32-trnL, rps16, trnS-trnG, and trnT-trnL) and the data were analysed using model based approaches (Maximum Likelihood, Bayesian inference). Wiborgia was well supported as monophyletic and sister to both Wiborgiella and Aspalathus, with Wiborgiella humilis well supported as being part of the Wiborgiella clade. Within the Wiborgia clade, two strongly supported subclades were observed. In subclade 1, W. tetraptera was strongly supported as sister to W. fusca, whilst W. monoptera was strongly supported as sister to W. incurvata. In subclade 2, a novel well-supported sister relationship between W. mucronata and W. tenuifolia was observed. Wiborgia obcordata, the only species in Dahlgren's subgenus Wiborgia, was found to be embedded within subgenus Pterocarpia and thus the subgenera classification of Dahlgren was not supported. It was also identified that sister species pairs (W. incurvata and W. monoptera; W. fusca and W. tetraptera; W. tenuifolia and W. mucronata) all showed the tendency to co-occur or have overlapping distribution ranges, and showed subtle differences in floral morphology and habitats.
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    Phylogeny reconstruction of the Schoeneae (Cyperaceae) with a focus on southern African genera
    (2008) Henning, Jessica; Muasya, A Muthama; Verboom, George Anthony
    In this study both plastid and nuclear DNA sequences (rbcL, trnL-trnF, rps16, ITS and ETS) were analysed. New sequences were added to the matrix from Verboom (2006). Parsimony method was used for phylogeny reconstruction. Morphological characters were then optimised on the parsimony tree using both maximum likelihood and parsimony reconstruction. The Schoeneae is not monophyletic. Scleria may be included in the Schoeneae. Schoenus is probably not monophyletic as was suggested by morphological heterogeneity. It seems as though the Schoeneae ancestor probably had present leaf blades, leaves spread out wide along the stem and an open inflorescence. Further research needs to be done including the sampling of more taxa and more sequences. The monophyly of this tribe is still yet to be resolved. Lower taxonmic relationships need to be resolved further.
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    Plant growth, stress tolerant traits and regulation of heat activated proteins in Aspalathus linearis (Burm. f.) R. Dahlgren exposed to elevated temperature and drought
    (2020) MacAlister, Dunja; Muasya, A Muthama; Crespo, Olivier; Chimphango, Samson B M
    Climate change is increasingly becoming a concern on plant growth, as seen in the increased number of warmer days and nights as well as an increased occurrence of heat waves, and drought periods globally. The Intergovernmental Panel on Climate Change has stated that global surface temperatures are constantly increasing and are likely to exceed 2 °C, compared to average temperatures in 1900, by the end of the 21st century. Changes in precipitation will also become more erratic, with high latitude and mid-latitude areas expected to have increases and decreases in rainfall respectively, while already dry areas will have increased frequencies of drought. Regions with Mediterranean climates, such as the Western Cape in South Africa, are particularly vulnerable to these climate impacts, with models and studies showing that there are already significant increases in temperatures, shifts in later winter rainfall and an increased severity of flooding. These climatic changes will impact both natural and agricultural plant species growth and distribution due to the changes in suitable growing conditions and regions. Plants are already exposed to a wide variety of environmental factors, each of which influences the growth, and deviations from the optimal conditions is considered abiotic stress and negatively affects plant growth. Plants in the field are rarely affected by only one stress as they are frequently exposed to a combination of abiotic stresses and with the changes in climate, plants will likely be experiencing abiotic stress such as heat and drought stress simultaneously. The aim of this thesis was to determine the effects of heat and drought on the plant growth and physiological performance of one of the most important indigenous commercial crops in South Africa, Aspalathus linearis (Burm.f.) R. Dahlgren, better known as rooibos tea, known for its many health benefits. This was achieved by focusing on three objectives: (1) determining the effects of temperature on plant growth and identifying the thermotolerant traits of the plants grown in the field along a temperature gradient, (2) determining the heat activated proteins and associated mechanisms for heat tolerance in field grown plants and (3) determining the physiological and morphological responses of A. linearis grown under two moisture regimes and later exposed to drought. The results for objective one are presented in chapter two, where a field study was conducted to observe the effects of temperature on the growth and stress tolerant traits of A. linearis grown at four farms sites in the Cederberg, South Africa along a temperature gradient. The four sites represent the rooibos farming area, from coolest to warmest respectively; Aurora (alt. 93 m), Citrusdal (alt. 588 m), Clanwilliam (alt. 312 m) and Uitsig (alt. 344 m). Aurora was also situated closest to the coastline, ∼18 km, compared to the other farms. The traits observed were changes in gas exchange, carbohydrate concentrations, phenolics and pigments, along with biomass, over a two-year period. Aspalathus linearis plants showed evidence of transpirational leaf cooling during summer and this, combined with lower chlorophyll and high phenolic content, could be considered acclimatized adaptive changes allowing the plants to mitigate the heating effects of elevated temperatures. Chapter three presented the results for objective two where the proteome of A. linearis was analysed from field plants along a temperature gradient. Protein samples were collected from the plants concurrently with the physiological samples for the previous chapter. These protein samples were quantified and then functionally annotated using the OrthoDB and UniProt databases. Overall, a total of 180 proteins were differentially expressed in the plants during exposure to high temperatures in the field. Of these 180 proteins, 113 were more upregulated in the cooler sites, Aurora and Citrusdal, and 67 proteins were more upregulated in the hotter sites, Clanwilliam and Uitsig thus indicating that with increasing temperatures there is a downregulation of proteins expressed during heat stress. From the 180 proteins, there were six main proteins involved in photosynthesis or light harvesting in A. linearis, with four of the six proteins upregulated in plants grown at Aurora, the cooler site, and in the hottest site, Uitsig. This agrees with results from chapter two, where plants from Aurora had superior photosynthetic rates compared to the other plants therefore allowing them to grow and produce better biomass. The hotter sites upregulated heat shock proteins more than the cooler sites, suggesting that their expression could be enhancing the thermotolerance of A. linearis plants through their chaperone activity where they protect other proteins against denaturation. There were also numerous proteins expressed in the plants which were related to oxidationreduction processes and antioxidants, most of which were expressed in the hottest site, Uitsig. One of the main concerns for plants during heat stress is the oxidative damage brought on by reactive oxygen species, and the expression of these proteins indicates that these proteins are contributing to the plants' thermotolerance through the production of antioxidant phenolic compounds as was seen in chapter two. In chapter four, a glasshouse study was conducted where plants were grown at two different moisture regimes (field capacities, FC) and then exposed to drought and both physiological and morphological parameters were measured. Morphological parameters measured included plant biomass, root/shoot ratios, total root length, average root diameter, total root surface area and specific root length. Physiological parameters measured were gas exchange, carbohydrate and phenolic concentrations, pigment concentrations, leaf relative water content and water potential. During drought, the gas exchange, relative water content and nonstructural carbohydrates in leaves were all reduced, while chlorophyll concentrations remained constant. Aspalathus linearis plants also had reduced stomatal conductance and transpiration, increased root/shoot ratios, root length and antioxidants such as polyphenol in leaves under drought conditions. Overall, changes in soil nutrients, including boron, available phosphorus, manganese and copper, and increasing temperatures had a negative impact on crop biomass, however, the phenolic content, which is a measure of tea quality, did not vary with sites. This suggests that farmers who are planning on shifting their rooibos farming further south of Cederberg, could still achieve good growth and high yields without compromising the quality of the tea. It was also seen that A. linearis plants upregulated heat shock proteins, along with proteins involved in antioxidant compounds particularly in the hotter sites thereby playing a critical role in their acquired heat-stress tolerance. Plants in the cooler sites upregulated proteins involved in photosynthesis and chlorophyll production, therefore allowing them to have higher photosynthetic activity and subsequently higher productivity. The up and down regulation was based on comparing the warmer sites (heat-stressed) to the cooler sites (control). The plants grown at lower FC and then droughted, exhibited drought tolerant mechanisms which included higher root/shoot ratios as well as thinner roots, both of which are effective for water and nutrient uptake. Overall, plants in the 30 % FC treatment recorded lower Pmax, gs and E after three days in the drought conditions while 70 % FC plants were only affected after five days. Furthermore, plants grown under low moisture (30 % FC) conditions produced 50 % lower biomass compared to plants grown under adequate moisture (70 % FC) conditions. This implies that low rainfall and the occurrences of dry spells and drought, associated with climate change are likely to reduce the production of A. linearis in the Cederberg area. The combination of both field work and glasshouse studies have provided insight into how these plants are affected by both heat and drought stress, as well as declining soil nutrients such as calcium, magnesium, manganese iron, copper and potassium. Aspalathus linearis is tolerant to high temperatures as well as dry conditions, however, more needs to be explored with regards to their thresholds particularly since climate change is likely to continue in the near future and eventually moving farming south will no longer be an option for farmers.
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    Radiation and Repeated Transoceanic Dispersal of Schoeneae (Cyperaceae) Through the Southern Hemisphere
    (Botanical Society of America, 2013) Viljoen, Jan-Adriaan; Muasya, A Muthama; Barrett, Russell; Bruhl, Jeremy; Gibbs, Adele; Slingsby, Jasper; Wilson, Karen; Verboom, Anthony
    • Premise of the study: The broad austral distribution of Schoeneae is almost certainly a product of long-distance dispersal. Owing to the inadequacies of existing phylogenetic data and a lack of rigorous biogeographic analysis, relationships within the tribe remain poorly resolved and its pattern of radiation and dispersal uncertain. We employed an expanded sampling of taxa and markers and a rigorous analytic approach to address these limitations. We evaluated the roles of geography and ecology in stimulating the initial radiation of the group and its subsequent dispersal across the southern hemisphere. • Methods: A dated tree was reconstructed using reversible-jump Markov chain Monte Carlo (MCMC) with a polytomy prior and molecular dating, applied to data from two nuclear and three cpDNA regions. Ancestral areas and habitats were inferred using dispersal–extinction–cladogenesis models. • Key results: Schoeneae originated in Australia in the Paleocene. The existence of a “hard” polytomy at the base of the clade reflects the rapid divergence of six principal lineages ca. 50 Ma, within Australia. From this ancestral area, Schoeneae have traversed the austral oceans with remarkable frequency, a total of 29 distinct dispersal events being reported here. Dispersal rates between landmasses are not explicable in terms of the geographical distances separating them. Transoceanic dispersal generally involved habitat stasis. • Conclusions: Although the role of dispersal in explaining global distribution patterns is now widely accepted, the apparent ease with which such dispersal may occur has perhaps been under-appreciated. In Schoeneae, transoceanic dispersal has been remarkably frequent, with ecological opportunity, rather than geography, being most important in dictating dispersal patterns.
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    Taxonomy and evolutionary studies on the genus Psoralea L. (Psoraleeae, Fabaceae)
    (2016) Bello, Abubakar; Muasya, A Muthama; Chimphango, Samson B M
    Psoraleeae is a tribe of the papilionoid legumes in Fabaceae comprising ca. 223 species in nine genera. Members of Psoraleeae are distributed worldwide, though they mainly occur in the temperate biomes. Of these, ca. 60% of the species (mostly in Otholobium and Psoralea) are endemic to southern Africa predominantly in the Greater Cape Floristic Region (GCFR). The genus Psoralea, consisting of 75 species endemic to southern Africa, is the second most speciose legume in the GCFR after Aspalathus (280 species). This thesis, consisting of a literature review, three research chapters and synthesis, studies the taxonomy, evolutionary history and biogeography of Psoraleeae with an emphasis on Psoralea.
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    Thermo and drought tolerance markers and regulation of heat stress proteins for chickpea (Cicer arietinum L.; Fabaceae) production in NE South Africa
    (2020) Makonya, Givemore Munashe; Chimphango, Samson B M; Ogola, Ochanda JB; Muasya, A Muthama; Olivier, Crespo
    Chickpea (Cicer arietinum) is an important legume crop globally ranked third after dry bean (Phaseolus vulgaris) and field pea (Pisum sativum). It constitutes 20% of the total global pulse production and around 95% of its production and consumption takes place in developing countries. Major constraints to chickpea production in sub Saharan Africa (SSA) have broadly been related to abiotic stresses, particularly drought and heat stresses, predicted to increase due to the global climatic changes.Dueto the imperativeness of research for identifying heat tolerance markers for potential chickpea genotype selection, in chapter two of the thesis, the response of four chickpea genotypes to a natural temperature gradient in the field was assessed using chlorophyll fluorescence, non-structural carbohydrate, gas exchange and grain yield. Field experiments were carried out in two winter seasons at three locations with known differences in temperature in NE South Africa. Results showed two genotypes (Acc#3 and Acc#7) were tolerant to heat stress with an Fᵥ/Fₘ of 0.83-0.85 at the warmer site, while the two sensitive genotypes (Acc#RR-2 and Acc#8) showed lower Fᵥ/Fₘ of 0.78-0.80. Both chlorophyll fluorescence measurements: dark-adapted Fᵥ/Fₘ and Fq'/Fₘ' (where Fq' =Fₘ'–F) measured at comparable high light levels correlated positively with grain yield. The two tolerant genotypes also showed higher photosynthetic rates,starch, sucrose and grain yield than the sensitive genotypes at the warmer site. However, these parameters were consistently higher at the cooler than at the warmer sites. It was concluded that genotypes Acc#RR-3 and Acc#7 are heat tolerant and chlorophyll fluorescence and leaf carbohydrates are suitable tools for selection of heat tolerant chickpea genotypes under field conditions. The coolest site of Polokwane showed favourable conditions for chickpea production.Heat and drought stresses are two abioticfactors that often occur simultaneously and are predicted to increase, consequently hampering plant growth. Response of different species to either stresses is well documented but information on the response of the same genotypes to both stresses in chickpea is limited. We aimed to determine whether previously noted heat stress tolerant genotype (Acc#7) is drought tolerant and the heat sensitive (Acc#8) is drought sensitive, and whether intermittent moisture supply at vegetative stage would induce priming effect to later drought at flowering. At vegetative stage, plants were divided into three groups, non-stressed (watered to 75% field capacity (FC), severe water stress (moisture-withholding for 14 days) and treated to 40% FC throughout the experiment (mild-stress), with recovery for the severely stressed plants after which they were stressed (double-stress) at flowering. Drought treatments at vegetative and flowering growth stages decreased physiological parameters and biomass accumulation in both genotypesexcept low water supply at 40% FC that decreased biomass in Acc#7 but not Acc#8. Double drought stress resulted in priming effect in Acc#7, having higher biomass, chlorophyll fluorescence, stomatal conductance, net photosynthesis, and relative water content in comparison to the introduction of stress only at flowering growth stage, as well as in comparison to Acc#8. These results showed that both Acc#7 and Acc#8 are sensitive to drought whereas after priming Acc#7 is better acclimated to drought than Acc#8 associated with osmotic adjustment on leaf relative water content (RWC) and higher capacity to protect photosynthetic activity, making Acc#7 potentially ideal for areas associated with intermittent drought spells. This observation, however, disapproved the hypothesis that Acc#7 is more drought tolerant than Acc#8 but is rather better acclimated than Acc#8, because of its superiority only in primed plants and not those stressed only at either vegetative or flowering stages. The findings emphasise the importance of matching chickpea physiological performance to expected rainfall amounts and distribution in drought prone areas during genotype selection. Chapter four of the thesis was an interrogative proteome analysis of the differences in the heat tolerant and sensitive chickpea (Cicer arietinumL.; Fabaceae) genotypes along a temperature gradient under field conditions which will help in identifying the molecular mechanisms involved in the crop's tolerance. Few studies have thus far combined chickpea physiological and proteome analysis to elucidate the changes in abundance and/or activity of relevant enzymes and expression of heat responsive proteins. In this study, analyses of chlorophyll concentrations, gas exchange, flavonoids and anthocyanin concentrations from a chamber experiment, as well as proteomic parameters from field studies in both the heat tolerant and sensitive genotypes are presented. The heat tolerant genotype Acc#7 maintained unaltered physiological performance at flowering growth stage when exposed to high (35/30°C) and moderate (30/25°C) heat stress, under climate chamber conditions compared to the two heat susceptible genotypes (Acc#RR-2 and Acc#8). Results from the proteomic studies showed an up-regulation in proteins related to protein synthesis (e.g. ribulose bisphosphate carboxylase/oxygenase activase), intracellular traffic (e.g. mitochondrial dicarboxylate/tricarboxylate transporter DTC), defence (e.g. HSP70) and transport (e.g. GTP-binding protein SAR1A-like) in heat tolerant Acc#7 compared to the susceptible Acc#8. Results from KEGG analyses support the involvement of probable sucrose-phosphate synthase and sucrose-phosphate phosphatase proteins in the starch and sucrose pathway,that were up-regulated in the heat tolerant genotype Acc#7. This result was in support of our earlier report where tolerant genotype Acc#7 had higher leaf starch and sucrose concentrations in comparison to the susceptible genotype Acc#8. The presence of these differentially regulated proteins including HSP70, ribulose bisphosphate carboxylase/oxygenase activase, plastocyanin and protoporphyrinogen oxidase shows their potential role in field grown chickpea tolerance to heat stress at flowering growth stage. In conclusion, chlorophyll fluorescence (both Fᵥ/Fₘ and Fq'/Fₘ') and leaf carbohydrates were identified as selection markers that can potentially be used for chickpea phenotyping for heat stress under field conditions with the chlorophyll fluorescence parameters correlating positively with seed yield. Due to its higher biomass, chlorophyll fluorescence (Fᵥ/Fₘ), stomatal conductance, net photosynthesis and RWC, heat tolerant genotype Acc#7 was identified to have better adaptive tolerance to drought stress after priming through exposure to intermittent dry spells than Acc#8. Furthermore, under controlled climate chamber conditions, Acc#7 consistently showed characteristics of tolerance to heat stress while Acc#RR-2 and Acc#8 were heat susceptible. Higher chlorophyll fluorescence, grain yield, chlorophyll concentrations, gas exchange, flavonoids and anthocyanin concentrations for Acc#7 compared to Acc#8 in the climate chamber was further validated by the higher up-regulation of proteins involved in protein synthesis, intracellular traffic, defence and transport in Acc#7 compared to Acc#8. The incorporation of proteomics in heat and drought stress studies will potentially help further the understanding of mechanisms by which the crop responds to these stresses.
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    What environmental variables limit Typha expansion in Cape Flats wetlands?
    (2010) Kilian, Kay-Leigh; Muasya, A Muthama
    The explosive expansion of Typha capensis into the wetlands of the Cape Flats has resulted in decreased species diversity and habitat value. Several initiatives to control this expansion have had varied success and management of wetlands dominated by T. capensis remains a challenge. For effective rehabilitation, one needs to understand what the problem is and its origin before any action can be taken. This study aims to determine whether there are any factors that limit the expansion of T. capensis that may be used in rehabilitation efforts, with the hypothesis being that the distribution of T. capensis is determined primarily by hydrology, salinity and nutrients such that wetlands with T. capensis or specific T. capensis stands will have stable hydrological regimes, moist soils, low salinities and high nutrients. Six wetlands in Rondevlei with varying dominance of T. capensis, ranging from not having any to being dominated by the plant, were examined. Wetlands were classified into types depending on their dominance of T. capensis, with Typha dominant, Mixed and No Typha wetland types. In each wetland soil cores were taken to represent the main vegetation types, focusing on T. capensis, Ficinia nodosa and Isolepis rubicunda. These three species comprise the dominant species of the three vegetation types that were measured, with T. capensis forming its own group and then rush-like and mat-like vegetation types respectively. Environmental variables like hydrology were observed by field visits at the end of summer and in winter/spring, and the soils were analyzed in the laboratory for salinity, pH and nutrients.