Thesis (PhD)--University of Pretoria, 2011. / Genetics / Unrestricted

Plant nectar is a simple food and is easily digested by many different species of pollinators. Many compounds make up the composition of floral nectars, but the most abundant are sugars, generally dominated by sucrose and the hexoses, glucose and fructose. Nectar sugars have been measured for many plant species visited by hummingbirds, sunbirds and other passerines, revealing a range of concentrations. The nectars of passerine-pollinated flowers are generally dilute compared to those of bee-pollinated flowers. The question why bird nectars are so dilute has been addressed in many studies. Many hypotheses have been proposed, among them the relationship between viscosity and drinking by birds. The viscosity of sugar solutions increases exponentially with increasing concentration, and capillarity is inversely proportional to viscosity. Nectarivorous birds imbibe nectar by capillarity, and high sugar concentrations could impose constraints on their feeding efficiency. Feeding in nectarivorous birds, especially hummingbirds, has been mostly devoted to assessing sugar type preferences. However, concentration preferences have received less attention, and the effect of viscosity on feeding has not been examined separately from sugar concentration for any bird species. Do nectarivorous birds show a preference for specific concentrations at a broad and a fine scale of difference, given a specific sugar type? Does viscosity impose a feeding limitation on nectarivorous birds? Does it affect their feeding behaviour? Sunbirds and other nectar-feeding birds can choose amongst various flowering plant species at any one time. Their feeding responses may have important consequences on pollination ecology. In this study, concentration preferences of white-bellied sunbirds were examined using paired solutions of either sucrose or equicaloric 1:1 mixtures of glucose and fructose, at a both a broad and a fine scale of difference between pairs over the concentration range of 0.25 to 2.5 M. I hypothesized that sunbirds would prefer concentrations of 1 M and higher on sucrose solutions, while preferring concentrations less than 1 M on hexose solutions. On both sugar types at the broad scale, the higher concentration was significantly preferred up to 1 M, suggesting a preference for 1 M sugar solutions. At a finer scale, white-bellied sunbirds were able to discriminate 0.03 and 0.05 M (1 and 2% w/w) concentration differences between sucrose and hexose solutions respectively. This discrimination is similar to that reported at low concentrations for other passerine nectar-feeders, and at higher concentrations for hummingbirds. To determine if high viscosity nectars limit the sugar intake of avian nectar consumers, white-bellied sunbirds were exposed to three different test series of sucrose solutions: control series (CS, pure sucrose 0.25 – 2.5 M), constant viscosity series (CVS, 0.25 – 0.7 M with increased viscosity equivalent to that of 1 M sucrose) and constant concentration series (CCS, 1 M with increased viscosities equivalent to that of 1.5, 2 and 2.5 M sucrose). Viscosities were artificially altered with Tylose®. The sunbirds had reduced intake rates and gained less energy on more viscous sucrose solutions. Also, sunbirds did not alter their feeding behaviour (feeding frequency, feeding duration, total feeding duration and feeding interval) in any significant way when feeding on more viscous sucrose solutions. This lack of change in feeding behaviour led to lower sugar intake rates and sugar consumption. These results suggest that sunbirds suffer a preingestional limitation when consuming nectars with viscosities higher than those due to sugar concentration alone. / Dissertation (MSc)--University of Pretoria, 2010. / Zoology and Entomology / unrestricted

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Within an ecological community, interactions between species in a community occur directly, through physical contact, and indirectly, via other species or through abiotic environmental modification. Genetic variation within a species has the ability to alter the outcome of interactions between species. In other words, the specific genotypes of the interacting individuals are important for the outcome of the interaction. In this thesis, I begin by showing that indirect interactions between a soil rhizobacteria (Pseudomonas aeruginosa) and a parasitoid wasp (Aphidius rhopalosiphum) are mediated by genotypic interactions between the two linking species, aphids (Sitobion avenae) and barley (Hordeum vulgare). This means that the magnitude and direction of the indirect effect of rhizobacteria (presence/absence) on the wing size of the parasitoid wasp was different, depending on the combination of interacting aphid and barley genotypes. If such interactions were to have an evolutionary effect, there would need to be non-random association between the aphid and barley genotypes. In the next chapter, I demonstrated that different aphid genotypes actively choose (no effect on reproductive rate) to colonize particular barley genotypes. I then showed that host preference of an aphid genotype could be altered by the presence, and sometimes genotypic identity, of another competing aphid genotype. I confirmed that these interactions were indirect, via the plant, by showing that aphid growth rate can be reduced when a plant is pre-conditioned with a different aphid genotype. Further investigation, using microarrays, showed that the different aphid genotypes induced differential gene expression in a single barley genotype. Many of these sequences belonged to known plant defense pathways and suggest a possible mechanism for the observed genotypic interactions between aphid and barley. In order to further understand the influence of within-species genetic variation on species interactions there is a need to consider these interactions in a natural system. I therefore investigated the influence of genetic variation within a single tree species on the associated plant and invertebrate communities in a complex, natural tropical ecosystem. I found that more closely related trees were host to more similar communities of epiphytic plants, leaf litter invertebrates around the base of the tree and trunk-dwelling invertebrates. This shows that even in a highly diverse, naturally occurring ecosystem the effect of genetic variation within a species can be an important factor for the structure of associated communities of both plants and animals.Research on the influence of within-species genetic variation on species interactions at a community level has wide applications for understanding how communities and ecosystems function, which can benefit agriculture, disease management and conservation practices.

In the next century, the world’s ecosystems are going to change dramatically. Within the Mississippi Delta, shrinking swamps, degraded wetlands, and invasive species of current day southern Louisiana will only continue to evolve. Plant distribution and range, weather patterns and storm frequencies, and uncontrollable growth of weeds are expected to have a huge impact on our environment. Weeds, any non-planned plant, are expected to grow more fiercely with rising levels of pollution, a warmer climate, and higher CO2 levels. Some consider weeds as being at the heart of environmental ruination; they must must be eradicated and they must be destroyed. Arguably, human impact plays a more significant role concerning the integrity of the environment. These are constructed and now changing ideas surrounding nature. In many cases, weeds and invasive species are detrimental. But these plants are also perfectly acclimated to their surroundings, offering the opportunities of phytoremediation, erosion control, storm water control, and even habitat creation with no use of resources and at no monetary cost. The Louisiana landscape has been irrevocably changed through geographical and climatic processes as well as human intervention. Its permanent transformation is expected with not only its shifting ecology but rising sea levels, erosion, and saltwater intrusion. Complete submersion is imminent in the next few centuries. Like the act of keeping New Orleans dry, there is tension between releasing human control over larger environmental systems and saving what we know and understand. Rather than working against nature, an architecture of awareness and acknowledgement of present circumstances and an anxious future can be established. This thesis seeks to investigate the evolving landscape of the future Louisiana coast through the design of a mutually beneficial system that is conscious of both the destruction and benefits of invasive plants. How can the existing and expected landscape occupants be productive and useful? How can the elements that make southern Louisiana so special be adapted for our changing ecologies? And what is the role of architecture in an evolving landscape on the brink of collapse? This thesis hopes to illuminate the ways in which something (sometimes seemingly) destructive can be positive, productive, and conscious. Considering shifting ecologies, how can architecture merge with the new landscapes and adapt to our present preservation needs now and environmental concerns in the future? / 0 / SPK / specialcollections@tulane.edu

The main aim of this study was to find a plant extract or isolated compound that could be used to combat aspergillosis in animals. Aspergillus fumigatus is one of the most common pathogenic fungal species in humans and animals. A. fumigatus is also an economically important fungus in the poultry industry. Current treatment of the disease is hampered by drug resistance of the organism to conventional antifungals and also its widespread toxicity to the animals. Seven tree species that had good antifungal activity against Cryptococcus neoformans in the Phytomedicine Programme database were selected for further work. These tree species were: Combretum vendae A.E. van Wyk (Combretaceae), Commiphora harveyi (Engl.) Engl. (Burseraceae), Khaya anthotheca (Welm.) C.DC (Meliaceae), Kirkia wilmsii Engl. (Kirkiaceae), Loxostylis alata A. Spreng. ex Rchb. (Anacardiaceae), Ochna natalitia (Meisn.) Walp. (Ochnaceae) and Protorhus longifolia (Bernh. Ex C. Krauss) Engl. (Anacardiaceae). The antimicrobial activity of leaf extracts of the selected plant species were determined against four important nosocomial bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa) and five important animal fungi (Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Microsporum canis and Sporothrix schenckii) using a serial microplate dilution method. The minimal inhibitory concentrations (MIC), of an acetone extract of Loxostylis alata was the lowest against Aspergillus fumigatus with an MIC value of 0.05 mg/ml. The number of antifungal compounds in extracts was determined by bioautography. The acetone extract of L. alata had the most active zones (10). The antioxidant, antiplatelet and cytotoxic effects of the seven plant species were evaluated using established in vitro assays. All the extracts had comparably low toxicity except for the extract of C. harveyi that had high haemagluttination assay titre value, which indicates toxicity. The extracts of P. longifolia, K. wilmsii, O. natalitia, L. alata, C. harveyi and C. vendae contained antioxidant compounds in the qualitative assay using DPPH. In the quantification of antioxidation using ABTS, only the extracts of P. longifolia, L. alata, and C. vendae had substantial antioxidant activity with respective TEAC value of 1.39, 1.94 and 2.08. Similarly, in the quantitative DPPH assay, L. alata. (EC50, 3.58 ± 0.23 μg/ml) and K. wilmsii (EC50, 3.57 ± 0.41 μg/ml) did not differ significantly (p ≤ 0.05) from the positive control (L-ascorbic acid). K. anthotheca had a much lower antioxidant activity (EC<su>50 176.40 ± 26.56 μg/ml), and differed significantly (p ≤ 0.05) from all the other extracts and control. In addition, the extract of C. vendae and C. harveyi had significant (p ≤ 0.05) antiplatelet activity and did not differ from the control (aspirin) with EC50 of 0.06 ± 0.01 μg/ml, 0.19 ± 0.00 μg/ml, respectively. Lower EC50 values in the antioxidant and antiplatelet studies are indicative of superior activity of the plant extract against oxidation and platelet aggregation. Based on the results obtained L. alata was selected for further examination. To simplify the isolation of the antifungal compounds from the L. alata fractions the acetone extract was first separated into six different fractions based on polarity in a mild solvent-solvent fractionation process. The fractions were aqueous methanol, butanol, carbon tetrachloride, chloroform, hexane and water fractions. The antimicrobial activities of the fractions as well as other relevant pharmacological tests on the different fractions were carried out. The number of antimicrobial compounds present in the aqueous methanol (AM), butanol (BT), carbon tetrachloride (CCl4), chloroform (CC), hexane and water fractions was determined by bioautography. The CCl4 extract was active against six out of the 9 microbial strains used and was particularly active against S. aureus, E. faecalis, A. fumigatus, C. albicans, C. neoformans and M. canis with MIC of 0.04, 0.04, 0.1, 0.1, 0.06 and 0.03 mg/ml, respectively. Microsporum canis was the most sensitive organism with the lowest average MIC of 0.16 mg/ml. Qualitative antioxidation using DPPH and quantitative assay using both ABTS and DPPH radicals revealed the presence of several antioxidant compounds in the AM, BT and water fractions of Loxostylis alata. This supported the usefulness of L. alata in treating fungal diseases, as aspergillosis and most fungal infections are associated with immune depression of the host. Antioxidants may reverse several conditions associated with immune deficiencies, resulting in increased levels of interleukin-2, elevated numbers of total lymphocytes and T-cell subsets. Loxostylis alata is used in southern African traditional medicine to control labour pain and to boost the immune system. Extracts and compounds isolated from leaves of Loxostylis alata were therefore also evaluated for their in vitro antimicrobial, anti-inflammatory (cyclooxygenase-1 and -2) activities and evaluated for their potential toxic effects using 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) and Salmonella typhimurium tester strains TA98 and TA100. Antimicrobial activity was evaluated using a serial microdilution assay. The bacterial strains used were Staphylococcus aureus (ATCC29213), Enterococcus faecalis (ATCC 29212), Pseudomonas aeruginosa (ATCC 27853) and Escherichia coli (ATCC 25922). The fungal strains used were Cryptococcus neoformans, Sporothrix schenckii, Aspergillus fumigatus, Microsporum canis and Candida albicans. A bioassay guided fractionation of the crude extract yielded two antimicrobial compounds namely, Lupeol and μ-sitosterol Lupeol had the most pronounced zone of inhibition against S. aureus and A. fumigatus., When MICs of the 2 compounds were determined, only lupeol had relatively good activity with MICs values ≤ 100 μg/ml against 8 out of 10 of the tested pathogens. However, β-sitosterol had activity against only S. aureus and E. coli with MICs values of 90 and 110 μg/ml, respectively. In addition β-sitosterol had selective inhibition of COX-1 (IC50 = 55.3 ± 2) None of the compounds isolated were toxic in the Salmonella typhimurium/microsome assay and MTT cytotoxicity test. The isolation of these two compounds is reported for the first time from Loxostylis alata. It was disappointing that the two antifungal compounds isolated from L. alata had such a low activity against Aspergillus fumigatus. This inhibits the development of a single compound that can be used therapeutically. Because the crude extract had very good activity we decided to investigate the safety and potential use of this extract in target animal species. At a dose of 300 mg/kg, the chicks had some signs of intoxication, but not at a dose of 200 mg/kg. Aspergillosis was induced experimentally, in broiler chicks. The degree of infection was assessed by comparing degree and severity of clinical signs, lesion scores and fungal re-isolation from treated chicks with those from infected chicks not treated with the extract. The extract at a dose of 100 and 200 mg/kg reduced significantly (p ≤ 0.05) the lesions due to aspergillosis and the amount of Aspergillus fumigatus isolated from infected chicks in an excellent dose related response.. The crude extract of L. alata leaves was as active as the commercially used ketoconazole against avian aspergillosis. It appears likely that the crude acetone extract could be produced at a much lower cost than ketoconazole or other chemical antimicrobial products. If these results can be confirmed in larger studies and if the crude extract does not have a negative effect on the production of the poultry the crude extract of L. alata may prove to be a viable and cost effective alternative to using current antimicrobial products. This study proves that it may be worthwhile to invest human and financial resources in searching for plant related products than can increase animal health and productivity. Copyright / Thesis (PhD)--University of Pretoria, 2009. / Paraclinical Sciences / unrestricted

This thesis investigates the influence of nonrandom species loss on the structure and functioning of trophic floodplain lagoons. Two experiments were conducted based on different realistic scenarios of biodiversity loss using multitrophic fish assemblages derived from long-term survey data. Loss of fish diversity influenced overall ecosystem multifunctionality of these lagoons through complex multitrophic interactions throughout the aquatic food web. These results indicate that biodiversity loss from diverse multitrophic ecosystems can influence ecosystem structure and function and likely deviate from simplified food chain dynamics or patterns that emerged from single trophic level studies.

Leptographium is an anamorph genus within the Ophiostomatoid group of fungi and represents a unique case for molecular applications. The genus has a near complete sequence data available for three genes across all known species. This characteristic makes it a perfect test group for investigating applications of new diagnostic techniques within ascomycetes. Probes and primers, for microarrays, are designed from phylogenetically useful gene regions and are fabricated onto a solid substrate using printing technology. The sample is prepared using PCR and is hybridised to the probes under stringent conditions. The resulting fluorescent pattern is rigorously analysed to distinguish species from each other. Diagnostic PCR uses primers that are designed in similar way to the way probes are designed for microarrays and indicate the presence of a species through positive amplification. This research methodology will be applied to Leptographium to evaluate the efficacy of microarray technology for discriminating species within that genus. The data gained from this research study will be used in applications for other genera using microarray technology. / Dissertation (MSc)--University of Pretoria, 2009. / Genetics / Unrestricted

Hypoxis (commonly known as African potato, Ilabatheka, Inkomfe, sterretjie or yellow starflowers and also as monna wa maledu or thitidi) is a genus of the family Hypoxidaceae. The rootstocks of Hypoxis species, particularly H. hemerocallidea, are well-known to be used in traditional medicine for the treatment of different ailments, such as urinary tract infection, epilepsy, prostate cancer and onset diabetes. Several visits have been made to the Faraday Medicinal Market and Abey Bailey Nature Reserve in Johannesburg to determine the availability of Hypoxis plant materials. From these visits, it was discovered that different Hypoxis species are harvested and sold as the same plant commonly referred to as the African potato, and the treatment with these plants might be questionable as the secondary metabolites might differ. This was proven when a number of rootstocks bought from the medicinal market grew into plants showing distinct morphological differences when planted at the Agricultural Research Council (Roodeplaat, Pretoria). It is possible that the plants sold are used as the substitutes for the commonly main plant, which is H. hemerocallidea and a reality is that many of the problems related to the quality of medicinal plants are based on the substitution of the declared plants and when the substitution occurs the quality of the plants becomes compromised leading to the risks of public health. It is however, not known whether the substitution is done deliberately or unintentionally since the outward morphology of Hypoxis species are not the same except their bright yellow flowers. The similarity within these species is on their underground rootstock. The dosage and toxicity of plant preparations is extremely important and, therefore adulteration is a concern where plant preparations are taken orally and the information about the plants used not being accurate. The aim of this study was to compare the secondary metabolite content of four Hypoxis species namely, H. acuminata, H. hemerocallidea, H. iridifolia and H. rigidula Thin Layer Chromatography (TLC) and High Performance Liquid Chromatography (HPLC) were used to analyze the secondary metabolite content of the plant extracts. Differences were also noted as one green compound was observed only in H. acuminata and H. rigidula. The HPLC results showed major differences in retention time in fresh material. The antibacterial activity of extracts of all four Hypoxis species showed similar results, although the activity differed amongst the microorganisms. The species showed high level of antioxidant activity that increased with increasing concentration in all four Hypoxis species. The species also showed no toxicity when tested in vitro on Vero cells however, they seemed to be toxic to cancer cells (Hela cells) but with a higher concentration. Hypoxoside was isolated and identified as the purple colour band on the TLC fingerprint and was confirmed in all the species. It might be possible to replace or substitute different Hypoxis species for H. hemerocallidea for medicinal use as the chromatograms of the other three species correlate well with the chromatograms of H. hemerocallidea after storage. / Dissertation (MSc)--University of Pretoria, 2010. / Plant Science / unrestricted

Seven plants native to the moist habitats of the pine savannas, woodlands, and Hillside Bog natural area at the Crosby Arboretum, Picayune, MS, were evaluated under laboratory and nursery conditions to determine seed germination percentage, optimal germination temperature, and the effect of substrates on germination. These native plants include: titi (Cyrilla racemiflora L.), buckwheat tree (Cliftonia monophylla Britt.), flameflower (Macranthera flammea (Bartr.) Pennell), deertongue (Carphephorus odoratissimus (Gmel.) Herb. var. odoratissimus), pink coreopsis (Coreopsis nudata Nutt.), tall ironweed (Vernonia angustifolia Michx.), and swamp bay (Persea palustris (Raf.) Sarg.). Laboratory experimentation concluded with germination and determination of optimal temperature regimes. Tall ironweed had the highest rate of success in the nursery. Black Kow compost had suboptimal performance compared to Sunshine Mix 1 and pine bark / sand under nursery conditions. Several of the species tested had minimal germination and require further research to optimize germination and nursery growth.