Structure and distribution of the slope fish community in the vicinity of the sub-Antarctic Prince Edward Archipelago

Demersal fish community structure, distribution and trophic relationships on the slope (depth range 200–1500 m) of the sub-Antarctic Prince Edward Islands and surrounding sea rises were investigated during a pilot survey conducted in April 2001 onboard fishing vessel MV Iris. A total of 56 fish taxa were collected during the survey, of which 44 were identified to the species level, seven to the genus level and five to the family level. Among the identified taxa, 36 constituted new records for the area investigated. Total catch per unit effort (cpue) during the survey ranged from 1•1 to 241•2 individuals h 1. Both average fish diversity and total cpue positively correlated with trawling depth. Overall, mean sampling depth and near-bottom temperature explained 56% of total fish cpue. Hierarchal cluster analysis identified three distinct fish assemblages with pronounced dominant species. Major shifts in fish community composition occurred at 500–600 m and 800–900 m depth strata and could probably be a result of physical and biological vertical zonation. Analysis of the diet of selected fish species showed that they were generalist feeders, consuming predominantly pelagic, including epipelagic, meso- and benthopelagic, prey. Diets of six species and nitrogen stable isotope signatures of 22 species revealed that with a few exceptions most fishes occupied the fourth trophic level and were tertiary consumers. Wide variability in carbon isotopic signatures is discussed with respect to alternative, e.g. possible importance of high Antarctic and chemoautotrophic v. photoautotrophic sub-Antarctic primary production, organic matter sources at the base of deep-sea food webs

Studying the impact of ocean eddies on the ecosystem of the Prince Edward Islands: DEIMEC ll

The Dynamics of Eddy Impacts on Marion’s Ecosystem Study (DEIMEC) programme was begun in 2002 with the aim of understanding the importance of the oceanic, upstream environment to the ecosystem of the Prince Edward Islands. This island group consists of two small volcanic islands and provides many opportunities for studying ecological and evolutionary processes, for monitoring ecological changes in relation to global climate change and for conserving a unique component of the planet’s biological diversity

Using a classroom library to promote extensive reading in a Grade 8 class in a Fort Beaufort District School, Eastern Cape : an action research case study.

This thesis reports on a collaborative action research case study with Grade 8 learners in a rural high school in Fort Beaufort District, Eastern Cape, South Africa. The goals of the case study were firstly, to understand best practices for promoting extensive reading using a classroom library, and secondly, to use these insights to put an extensive reading programme in place with a view to improving my practice as a language teacher and to gain better understanding of ways of enhancing my Grade 8 learners’ literacy skills. The following qualitative methods were used to collect data: observation, semi-structured interviews, class discussion, questionnaires, journal reflections and document analysis. Analysis of data involved identification of emerging themes and patterns. The findings suggest that the strategies used in the extensive reading intervention improved my learners’ levels of engagement with reading. Putting these strategies into practice, and reflecting critically on how to refine them helped enrich my own professional insight and development in relation to the implementation of extensive reading programmes. Since action research is usually designed in spirals of action, this research serves as a first spiral and a foundation upon which to build second and subsequent spirals (which do not form part of this research). The study highlighted the fact that certain challenges that emerged (for example, shortage of books at the learners’ level, and a lack of parental cooperation) need to be addressed in a second spiral of intervention. The study further suggested that the implementation of effective extensive reading programmes by teachers in the middle and upper phases of secondary schooling requires further investigation

Critical indirect effects of climate change on sub-Antarctic ecosystem functioning

Sub-Antarctic islands represent critical breeding habitats for land-based top predators that dominate Southern Ocean food webs. Reproduction and molting incur high energetic demands that are sustained at the sub-Antarctic Prince Edward Islands (PEIs) by both inshore (phytoplankton blooms; "island mass effect"; autochthonous) and offshore (allochthonous) productivity. As the relative contributions of these sustenance pathways are, in turn, affected by oceanographic conditions around the PEIs, we address the consequences of climatically driven changes in the physical environment on this island ecosystem. We show that there has been a measurable long-term shift in the carbon isotope signatures of the benthos inhabiting the shallow shelf region of the PEIs, most likely reflecting a long-term decline in enhanced phytoplankton productivity at the islands in response to a climate-driven shift in the position of the sub-Antarctic Front. Our results indicate that regional climate change has affected the balance between allochthonous and autochthonous productivity at the PEIs. Over the last three decades, inshore-feeding top predators at the islands have shown a marked decrease in their population sizes. Conversely, population sizes of off-shore-feeding predators that forage over great distances from the islands have remained stable or increased, with one exception. Population decline of predators that rely heavily on organisms inhabiting the inshore region strongly suggest changes in prey availability, which are likely driven by factors such as fisheries impacts on some prey populations and shifts in competitive interactions among predators. In addition to these local factors, our analysis indicates that changes in prey availability may also result indirectly through regional climate change effects on the islands' marine ecosystem. Most importantly, our results indicate that a fundamental shift in the balance between allochthonous and autochthonous trophic pathways within this island ecosystem may be detected throughout the food web, demonstrating that the most powerful effects of climate change on marine systems may be indirect

Genetic diversity and pathogenicity of sorghum-associated Fusarium species

Doctor of PhilosophyDepartment of Plant PathologyChristopher R. LittleUnderstanding the genetic structure of fungal pathogens enables the prediction of evolutionary forces that drive pathogen evolution, which assists informed decision-making regarding disease management. The genetic structure of Fusarium thapsinum and F. andiyazi, two important pathogens that cause grain mold and stalk rot of sorghum (Sorghum bicolor), are little understood. The genetic structure and pathogenicity of a F. thapsinum population from sorghum in Kansas were evaluated with amplified fragment length polymorphisms (AFLPs), vegetative compatibility groups (VCGs), sexual cross-fertility, and seedling pathogenicity. Two sympatric populations and a genetically intermediate "hybrid" group were identified in Kansas. Seedling pathogenicity of strains ranged from non-pathogenic to pathogenic, which may be partially attributable to genetic variability in the F. thapsinum populations. Genetic relatedness between populations of F. thapsinum from sorghum in Kansas, Australia, Thailand, and three African countries (Cameroon, Mali, and Uganda) were evaluated with AFLP markers and sexual crosses. Genetic diversity was high in all locations, but female fertility is very low. These results are consistent with the hypothesis that both sexual and asexual modes of reproduction are important components of the life cycle of F. thapsinum in these populations. More strains from Kansas and Africa were available for analysis than from Australia and Thailand, so the Kansas and Africa populations dominated the genetic structure observed. The two smaller populations from Australia and Thailand were more closely related to the Kansas population than they were to the African population. The three non-African populations contained information from the African population and from other, as yet unidentified, source population(s). Identifying the population(s) from which this genetic diversity originated is an important unanswered question. Stalk rot of sorghum was evaluated by inoculating stalk rot sensitive and stalk rot resistant sorghum lines with six genetically diverse F. thapsinum strains from Kansas under field and greenhouse conditions. One susceptible line (Tx7000) and two resistant lines (SC599 and BTx399) were evaluated in the field but only Tx7000 and SC599 were evaluated in the greenhouse. Disease severity was measured by major lesion length and the number of nodes crossed by the lesion. There were differences in aggressiveness amongst the F. thapsinum strains in both the greenhouse and field evaluations. This study provides the first evidence for differences in stalk rot aggressiveness amongst F. thapsinum strains and highlights the importance of challenging germplasm with well-characterized strains that represent the genetic spectrum of the entire population. The genetic diversity within F. andiyazi populations and some closely related strains was evaluated with AFLP markers. Phylogenetic and STRUCTURE analyses of the AFLP markers grouped the 81 F. andiyazi strains into three distinct clusters. The clusters were not based on the geographic origin of the strains. These results indicate the presence of at least one and possibly two undescribed sister taxa of F. andiyazi. More work is needed to further characterize these sister species of F. andiyazi and to understand their role in sorghum pathogenicity. There is genetic variation in global populations of F. thapsinum and the observed variation could be associated with variation in both seedling and adult plant pathogenicity. The study of F. andiyazi populations validated the need to properly identify and characterize Fusarium spp. associated with sorghum from different regions of the world

Effect of Rooibos and Honeybush Tea Extracts Against Botrytis cinerea

Green tea extracts from the indigenous South African rooibos (Aspalathus linearis) and honeybush (Cyclopia species)plants were evaluated as potential antifungal agents against the plant pathogen Botrytis cinerea. When applied at 10mg/ml, the tea extracts stimulated biomass production in B. cinerea by more than 3-fold after 24 hrs. This inductioncould not be linked directly to the presence of selected micro- and macronutrients or antioxidants in the extracts,suggesting a complex set of yet unidentified factors that may act synergistically to enhance cell growth. However,when applied at 100 mg/ml, the A. linearis and C. genistoides extracts reduced spore germination of B. cinerea by33.3% and 16.7%, respectively. This suggests that the tea extracts contain active compounds that should be furtherinvestigated for their potential as natural anti-fungal agents

Effect of rooibos and honeybush tea extracts against Botrytis cinerea

The original publication is available at http://www.sasev.org/.Green tea extracts from the indigenous South African rooibos (Aspalathus linearis) and honeybush (Cyclopia species) plants were evaluated as potential antifungal agents against the plant pathogen Botrytis cinerea. When applied at 10 mg/ml, the tea extracts stimulated biomass production in B. cinerea by more than 3-fold after 24 hrs. This induction could not be linked directly to the presence of selected micro- and macronutrients or antioxidants in the extracts, suggesting a complex set of yet unidentified factors that may act synergistically to enhance cell growth. However, when applied at 100 mg/ml, the A. linearis and C. genistoides extracts reduced spore germination of B. cinerea by 33.3% and 16.7%, respectively. This suggests that the tea extracts contain active compounds that should be further investigated for their potential as natural anti-fungal agents.Publishers' versio

Native Fusarium species from indigenous fynbos soils of the Western Cape

Thesis (MSc (Microbiology))--Stellenbosch University, 2008.The genus Fusarium contains members that are phytopathogens of a number of agricultural commodities causing severe diseases such as wilts and rots. Fusarium species also secrete mycotoxins that have devastating effects on humans and animals. The ability of Fusarium species to change their genetic makeup in response to their immediate environment allows these fungi to exist in diverse habitats. Due to the ubiquitous nature of Fusarium, it forms part of the fungal communities in both agricultural and native soils. Fynbos is the major vegetation type of the Cape Floristic Region (CFR), which is a region that is renowned for its high plant species diversity and endemism. In this study, the occurrence and distribution of Fusarium species in indigenous fynbos soils and associated plant debris is investigated. In addition, the phylogenetic relationships between Fusarium species occurring in this particular habitat are evaluated. Fusarium isolates were recovered from soils and associated plant debris, and identified based on morphological characteristics. The morphological identification of isolates was confirmed using Polymerase Chain Reaction (PCR) based restriction fragment length polymorphism (RFLP) analyses of the translation elongation factor 1 alpha (TEF-1α) and internal transcribed spacer (ITS) regions. Furthermore, phylogenetic relationships between Fusarium species were based on the TEF-1α, ITS and β-tubulin gene regions. One-hundred-and-twenty-two (122) Fusarium strains were isolated from the fynbos soils in the Cape Peninsula area (Western Cape). Based on both morphological and molecular identification, the most prevalent Fusarium species in the fynbos soils were F. oxysporum Schlecht. emend. Snyd. and Hans., F. solani (Martius) Appel and Wollenw. emend. Snyd. and Hans., F. equiseti (Corda) Sacc. and an undescribed Fusarium species. Fusarium oxysporum was the dominant species in fynbos soils and strains of this species displayed significant genetic variability. Some strains of both F. oxysporum and F. solani showed close phylogenetic affinities to formae speciales (strains pathogenic to specific plant hosts) in the phylogenetic analyses. However, no diseased plants were observed in and within the vicinity of our sampling sites. In the third chapter, the undescribed Fusarium strains are described as Fusarium peninsulae prov. nom. Morphologically these strains are characterized by falcate macroconidia produced from brown sporodochia. The macroconidia are pedicellate, falcate to curved with hooked apical cells. Also, this fungus produces apedicellate mesoconidia on polyphialides in the aerial mycelium and forms microconidia sparsely. Chlamydospores are formed abundantly on aerial mycelium and submerged hyphae. All these morphological characteristics closely relate this fungus to F. camptoceras species complex in Fusarium section Arthrosporiella. However, phylogenetic analysis based on the ITS sequences differentiate these strains from F. camptoceras and other related species in section Arthrosporiella. Considering the fact that both as phytopathogens and saprophytic fungi, Fusarium species secrete a variety of cell wall degrading enzymes such as cellulases and xylanases. These enzymes allow the fungi to degrade the plant cell wall components to obtain nutrients. In Fusarium, notably endoxylanases play a role in phytopathogenesis of these fungi. Endoxylanase enzymes from F. oxysporum f. sp. lycopersici, F. verticillioides and F. graminearum have been characterized. In this final chapter, the use of the endoxylanase encoding gene, as a molecular marker in phylogenetic analysis was evaluated using F. graminearum (Fg) clade species as model. Degenerated primers were designed and the endoxylanase region amplified by PCR, cloned and sequenced. PAUPgenerated neighbour-joining analysis of the endoxylanase (XYL) region enabled all species to be distinguished and was as informative as the analysis generated with UTPammonia ligase (URA), phosphate permase (PHO), reductase (RED) and trichothecene 3- О-acetyltransferase (TRI101). Furthermore, the results of the phylogenetic analysis of XYL showed better species resolution in comparison to the analysis of the structural genes (TEF-1α and histone H3). Overall, the results demonstrated that phylogenetic analysis of XYL combined with other functional genes (URA, PHO, RED and TRI101) clearly distinguished between the Fg clade species far better than the analysis of structural genes (TEF-1α and histone H3)

Partial endoxylanase gene as a molecular marker for phylogenetic analysis and identification of Fusarium species

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A new species of Fusarium from fynbos soils of the Western Cape Province, South Africa

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