Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv & Cons Biol)

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A comparative study of degeneration of the posterior limbs and girdles of some scelotes species.
(University of the Western Cape, 1981) Wilson, Brain .A; Skinner, J.H; Leonard, C.J
The genus Scelotes was instituted by Fitzinger in 1826 and is represented by nineteen species and subspecies in Southern Africa (Fitzsimons, 1943) . Valuable contributions have been made to our knowledge of the Lacertilia by pioneers such as Gadow (1881) , Cope (1892) , El-Toubi (1938) , King (1964) and Tiedeman et al . (1975) who investigated the osteology and myology. Essex (1927) , Stokely (1947) , Lande (1978) and Leonard (1979) dealt with the evolution of limb loss and pelvic girdle degeneration in the lizards , and especially in the skinks. van der Klaauw (1948), Snyder (1952; 1954) and Gans (1962; 1966; 1973) studied the ecology and behaviour of limbless tetrapods, while De Witte and Laurent (1943) and Greer (1970) contributed to our knowledge on the systematics of the skinks. Partial or complete loss of limbs and degeneration in the pelvic arch have possibly evolved independently in a variety of tetrapods. The genus Scelotes exhibits a full range of degeneration - from fully pentadactyle tetrapodous forms to limbless species. The question arises : Can a general pattern of devolution be observed in this genus? Al though many of the Scelotes species have already been described, it will here for the first time be attempted to compare the different stages of degeneration as exhibited in this genus. A major objective of this work will , therefore be to analyze the pattern of degeneration in Scelotes. Firstly, the osteology of the pelvic girdle and hindlimbs of the Scelotes species will be described and, secondly, these structures will be compared. Thirdly, an attempt will be made to graphically reflect the major trends associated with limb regression by employing morphometric data obtained from the limited number of specimens available
Evaluation of quantitative motility and zona pellucida binding of human spermatozoa in an assisted reproductive programme
(University of the Western Cape, 1994) Kaskar, Khalied; der Horst, G. van
Male factor disorders affect more than 30% of infertile couples. Thus, it has become important to perform a andrological consultation and a basic semen evaluation in all male partners of couples consulting for infertility. The advent and development of assisted reproductive technologies has not only improved clinical results but also enhanced our basic understanding of the physiology of sperm and sperm preparation methods. Assisted reproduction has become among the more successful therapeutic modalities for a wide variety of sperm function disorders e.g. artificial insemination and in vitro fertilization (IVF) (Acosta et al. 1989). It is clear from recent experience that patients with male infertility showing oligozoospermia, asthenozoospermia, teratozoospermia (sometimes in combination), male immunological factor (antisperm antibodies) or ejaculatory problems as well as congenital abnormalities, can be successfully treated with IVF and embryo transfer. Prerequisite pre-fertilization changes by sperm, termed "capacitation" (Austin 1952) provides sperm with the capacity to fertilize eggs. These processes are generally regarded as encompassing all pre-fertilization changes occurring in sperm up 'to, but not including, loss of the acrosome (Bedford 1970). The endpoints of capacitation are often described as the acrosomal loss as well as changes in the motion characteristics. Capacitation alters the pattern of motility exhibited by freely swimming sperm, changing from a fairly rigid flagellar beat pattern to one of extreme flexure, often associated with increased thrust (Johnson et al. 1981) , which is referred to as hyperactivated motility (Yanagimachi 1981). without the transition to hyperactivated motility, sperm are unable to penetrate the zona pellucida (Fraser 1981), and possibly unable to fertilize eggs. Hyperactivation per se is marked by increased curvature in swimming trajectories and/or increased lateral displacement of the sperm head along their path (Burkman 1984). However, the physiological role of this change in motility is not clearly understood because almost all relevant data have been obtained under in vitro conditions. The association of specific seminal characteristics (sperm concentration, percentage motile cells and percentage normal sperm morphology) with the success rate of assisted particular has been The analysis of 1984; the reproductive techniques and IVF in under great scrutiny (Mahadevan and Trounson relationships between conventional semen parameters and fertilization rates in vitro has shown that sperm motility, concentration and morphology must be considered in estimating opportunities for successful intervention, as in the case of IVF and gamete intrafallopian transfer (GIFT) (Oehninger and Hodgen 1991). A reduction in the percentage of progressive motility alone does not seem to have a significant impact on IVF results unless it is below a threshold value of 10%. The semen sample should have an acceptable sperm concentration and morphology and/or that at least 1.5 X 106 motile spermatozoa can be recovered after swim-up separation (Acosta et al. 1989).
The effect of maternal nicotine exposure on the quantity and quality of neonatal rat lung connective tissue
(University of the Western Cape, 1994) Dolley, Larry; Maritz, G
The infants of smoking mothers (compared to non-smoking mothers) have been shown to have a lower birth mass, a lower brain mass, an increased perinatal mortality rate as well as a predisposition to respiratory abnormalities in later life. Evidence suggests that one of the reasons for the latter is abnormal lung structure due to changes in the connective tissue skeleton. This study evaluated the in vivo effects of maternal nicotine exposure (lmg/kg/day subcutaneously - designated the experimental group), which is equivalent to smoking 32 cigarettes per day, on the connective tissue status of the neonatal (7, 14 and 21 day old) wistar rat lung. The control group received sterile saline as a placebo. The specific aspects investigated were: (1) the morphological changes in lung structure and connective tissue (collagen, elastic tissue and reticulin) distribution by means of light microscopy. (2) the quantities of collagen and Emphysema-like morphological changes are present at all ages. The histochemical appearance of collagen is not affected while reticular fibres appear to be abnormal in structure. On day 7 there appears to be no elastic tissue in the nicotine-exposed lung compared to the control lung. This difference is notelastic tissue in the lung. (3) the ultrastructure of the lung connective tissue skeleton by means of scanning electron microscopy. noticeable on days 14 and 21. Biochemical quantitation indicated that, for the three age groups studied, there was no significant difference in collagen content between experimental and control animals. Elastic tissue was significantly higher in 7 day old experimental lungs than in the control group, contradictory to the results of the histochemical studies. This difference was not significant for 14 and 21 day old lungs Ultrastructural studies of the lung connective tissue skeletons hoed abnormal fibres in the experimental group. Changes included fibre breaks, a beaded appearance of certain fibres and a deficiency in normal fibre arrangement due to the direct or indirect effects of nicotine The effects of nicotine on neonatal rat lung after maternal nicotine exposure is described. The direct mechanisms for these events are still not known but speculation as to this are presented here. Further studies which could explain these mechanisms are also suggested.
The reproductive physiology of The south african pilchard.
(UWC, 1995) Leaner, JJ
Epipelagic fish species form an integral component of the world's supply of protein. The most abundant of these fish belong to the order Clupeiformes (clupeoids) which include sardine, pilchard, sardinella, sprat, and herring. This multi-species group has been estimated to have contributed up to 20% of the world's marine catch in the 1980's (Armstrong and Thomas, 1989). The economic importance of the clupeoids was not only realized by the world's commercial pelagic fishing industry, but the energy was soon directed into experimental research on the multi-species group, both locally and internationally.
Detection of phycotoxins along the South African coast: a comparison of three different biological assay systems and instrumental analysis by high performance liquid chromatography
(University of the Western Cape, 1998) Myburgh, Carolyn l.; Gibbons, Mark
In recent years, harmful algal blooms have been of growing concern in many parts of the world. These blooms often result in deterioration in water quality, large-scale mortalities in marine life, and shellfish poisonings which can adversely affect local mariculture industries, coastal tourism and fisheries. Because of problems related to some of the methods that are currently used to detect phycotoxins (e.g. false positives), it has become necessary to explore new approaches, especially for routine monitoring. In this study, High Performnance Liquid Chromatography was used as an instrumental method for detecting Paralytic Shellfish Poisoning in mussel samples. Three bioassays were also examined, viz. the luminescent bacteria assay (LUMIStox kit), the Artemia larvae assay (Artox kit), and the sea urchin gamete test. The bioassays were assessed as to their suitability, reliability and practicality in detecting phycotoxins in water and mussel samples. HPLC was used to establish toxin profiles of mussel samples from South Africa, where Alemndrium catenella was present in the water. The three bioassays were found to be unsuitable for detection of toxins in mussel samples. However, based on the results obtained in this study, the Artox kit seems to be the most suitable, sensitive and practical bioassay for the detection of PSP toxins in water samples.
Studies of foraminifera associated with gelidium pristoides (turner) keutzing (gelidiales: rhodophyta)
(University of the Western Cape, 2002) Toefy, R; McMillan, K; Gibbons, M.J
Our understanding of the macrofauna of hard intertidal substrata around South Africa is fairly comprehensive, and we have a good understanding of the environmental factors responsible for structuring macrofaunal communities (McQuaid & Branch, 1985; Bustamante et al., 1996; Emanuel et al., 1992). The same cannot be said for meiofaunal communities of rocky shores, which despite their neglect are known to play an important role in the functioning of many intertidal systems (Gibbons & Griffiths, 1986). While macrofauna may dominate rocky shores in terms of biomass, meiofauna are generally more abundant, and because they have faster turnover rates they make an important contribution to secondary production (Gibbons & Griffiths, 1986).
Chytridiomycosis in amphibian populations in the Western Cape, South Africa
(University of the Western Cape, 2002) Hopkins, Samantha; Channing, Alan
There have been many cases reported of amphibian populations declining. These are often due to anthropogenic factors such as habitat destruction and pollution. However, some declines have not had an obvious cause and many of these have been investigated and found to be due to pathogenic disease. Batrachochytrium dendrobatidis is a recently described pathogen of frogs. The population declines that have been associated with chytridiomycosis have occurred in relatively undisturbed areas such as national parks. The declines tend to occur at higher altitudes or in colder climates. This is thought to be because of the frog immune system being slower at lower temperatures. Chyt1id fungus has been found in frog populations throughout the world. Little research has been carried out in Africa although, chytridiomycosis has already been seen in Kenya and South Africa. In this project frogs were sampled from selected transects in the Western Cape and three sites in the Northern Cape. The effect of altitude on the occurrence of infection was tested in the Western Cape. It was found that 18 frogs were infected in the Western Cape and the effect of altitude was not significant. Large numbers of dead and dying frogs were found in two of the Northern Cape sites and the incidence of chytridiomycosis was high in these populations. Chytrid was found in two Bufogariepensis from the Eastern Cape and in Xenopus petersii from Kasanka National Park, Zambia. More research is needed on chytridiomycosis in these populations. The frogs in the Western Cape seem to survive with chytrid fungus infection whereas, the frogs in the Northern Cape are dying. This suggests another factor acting on the Northern Cape frog populations.
The effect of exogenous growth regulators on salinity tolerance in Erucastrum strigosum
(University of the Western Cape, 2003) Gxaba, Nomagugu; Raitt, L. M.
Randomized block experiments were conducted to examine the putative amelioratory effects of kinetin or gibberellic acid at concentrations (0, 4, 12.5, 40, and 125 μM) in Erucastrum strigosum plants subjected to a salinity series (0, 100, 200, 300, and 400 mM NaCl) in the greenhouse. When the highest salinity concentration (increased stepwise) was reached, growth effects in relation to water and cation content of the plants were evaluated. Growth and water content were reduced progressively with salinity treatments. Na+ concentration accumulated with salinity treatments to levels that were much higher than that of other cations (K+, Ca2+ and Mg2+) in both organs. However, it is noteworthy that Na+ distribution was more in shoots than in roots. In kinetin treated plants, shoot growth decreased whilst root growth increased with moderate hormonal treatments.
Species delimitation and assessment of genetic variability in Carpobrotus (Aizoaceae): evidence from amplified fragment length polymorphisms
(University of the Western Cape, 2004) Khunou, Angeline; Reeves, Gail
During the course of this thesis, AFLP technique was successfully applied to the Aizoaceae taxa. This study involved a substantial component of laboratory work including generating and analysing AFLP data, the operation of an ABI377 automated DNA sequencer, and use of GeneScan and Genotyper software (Applied Biosystems). The initial motivation for this study was to reconstruct relationships between species of the genus Carpobrotus. However, it soon became clear that this would be impossible via the use of DNA sequence data. This was due to the inability to find DNA regions with sufficient variable characters for phylogenetic reconstruction. Therefore applying the AFLP fingerprinting technique to the question of species-level relationships in Carpobrotus resulted in individuals of the same species not forming distinct groups. This has subsequently led to the conclusion that gene flow is common across species boundaries in Carpobrotus as a result of hybridisation. An alternative ved may be that current species delimitations in this group are not well defined. These results also concord well with isozyme studies taxa in the Mediterranean Basin. Increased sampling of species other than C. acinaciformis and C. edulis would allow further investigation into the genetic delimitation and affinities of Carpobrotus, and shed light on the In the biotechnological age the use of molecular techniques has has the potential to greatly improve the bio-prospecting process. This has particular relevance to plants with medicinal properties, such as Carpobrotus, whereby targeted selection of genotypes with well-characterised medicinal properties may increase efficiency. Genetic and phylogenetic information can also help to identify closely related species and genera that may share similar metabolic pathways and properties. These issues are quickly coming to the forefront in the new South Africa, with the opening up of traditional knowledge systems, and subsequent integration and contact with the biotechnology community. 79
Specias delimitation and assessment of genetic variability in Carpobrotus (Alzoaceae): evidence from amplified fragment length polymorphisms
(University of the Western Cape, 2004) Khunou, Angeline; Reeves, Gail; Weitz, Frans
Species of Carpobrotus (Aizoaceae: Ruschioideae) are widely spread throughout South Africa and are commonly used for their medicinal properties. The genus consists of 13 species of which seven occur in South Africa, five in Australia and one in Chile. A number of investigations on South African species have demonstrated that some taxa exhibit anti-microbial activity. Using AFLPs (amplified fragment length polymorphisms) this study was undertaken with the primary aim of resolving relationships between Carpobrotus species in South Africa, and determining species limits by assessing their genetic distinctness. In addition, levels of genetic variability among populations of two South African species, C. acinaciformis and C. edulis werc assessed in more detail. AFLPs were not able to resolve conflict surrounding species boundaries, perhaps due to extensive hybridization. However, major groupings within South African species were identified, although no geographical structuring of these populations was evident. From a bio-prospecting perspective caution needs to be taken when sampling Carpobrotus due to difficulty in identifying species possibly as a result of hybridization.
The water quality and ecological status of the Diep river catchment, Western Cape, South Africa
(University of Western Cape, 2004) Ndiitwani, Tovhowani Brenda; Knight, Richard; Jonker, Lewis
The study illustrates the current ecological integrity of the Diep River system, based on the recent river health assessment using the South African Scoring System version 5 (2000-2003) and the water quality data (1996-2002). Some of the major land-use impacts on the river system are highlighted.
The effect of copper on the growth, development and chemical composition of some dryland wheat cultivars
(University of the Western Cape, 2005) Gordon, Julie Johannes; Aalbers, J; Raitt, L M; Faculty of Science
Heavy metal accumulation in arable land as a result of mining activities, pesticides and fertilisers has become a global concern. Steinkopf and Concordia in the Northern Cape are well-known for subsistence farming, but just as well-known for the nearby copper mining industry. Very little research has been done on heavy metal toxicity in these areas, thus it was of importance to assess the wheat cultivars (Triticum aestivum) historically used in the study areas, to ensure the viability of wheat farming. The nine wheat cultivars screened were Flameks, Knoppies, Rooiwol, Rooigys, Yecoro Royo, Charchia, Witwol, Kariega and Losper. A comparative study was done by determining the concentration levels of Cu, Fe, Zn, Mn, K, Mg, Ca, Na, N and P in the roots and shoots of sensitive and tolerant wheat cultivars. It was established that Witwol and Rooigys were the most tolerant to these adverse conditions. Kariega and Rooiwol were most sensitive. Their tolerance was achieved by excluding copper from the roots and limiting the translocation of copper to the shoots. This trend to exclude copper uptake in Witwol and Rooigys, warrants further investigation on a molecular level to explain these adaptive mechanisms.
Seasonal movement and activity patterns of the endangered geometric tortoise, psammobates geometricus
(University of the Western Cape, 2005) Van Bloemestein, Ulric Patrick; Hofmeyr, Margaretha D.; Henen, Brian T.; Dept. of Biodiversity and Conservation Biology; Faculty of Science
Due to the critical status of Psammobates geometricus and the vulnerability of their habitat, there is a need to allocate areas for their protection. The aim of this study was to provide information on the space requirements and activity level of geometric tortoises to facilitate future conservation efforts. The thread-and-spool method was used to compare short-term movements, habitat utilisation, and activity patterns of male and female tortoises over 15 and 20 days respectively, in autumn and spring. Through radiotelemetry, the long-term movements of 10 male and 11 female tortoises were evaluated from April 2002 to April 2003. Locality data for the short-term and long-term studies were used to calculate the size of activity areas and home ranges as minimum convex polygons and fixed kernel estimates. Male and female geometric tortoises were active throughout the year, and maintained a high level of activity in autumn and in spring. However, females were more active than males were in spring. Females may require more resources, particularly food, in spring when they produce eggs. Although males and females travelled similar distances in autumn and in spring, males displaced further than females displaced in both seasons. The movement path for males was often linear, perhaps because this path may enhance their opportunities to encounter females. Geometric tortoise males were substantially smaller than females, which may explain why the distances that males moved and displaced in spring were negatively correlated to environmental temperature. In autumn, when temperatures were lower than in spring, the distance travelled by males was not correlated to temperature. However, in autumn female displacement showed a positive correlation with environmental temperature. Geometric tortoises showed large inter-individual variation in home range size, which may contribute to the fact that home range size did not differ among the three different habitat types: mature renosterveld, burned renosterveld and the old agricultural fields. Average home range size was 11.5 ha for 95% fixed kernel estimates, and 7.0 ha for minimum convex polygon estimates. Body size influenced the home range size of female geometric tortoises, but had no effect on the home range size of male tortoises. Females had larger home ranges than male tortoises had, possibly because females were larger, but reproductive requirements of females may have played a role. During the dry season, home range size increased when compared to the wet season. The larger home range during the dry season, which is associated with high temperatures, may be related to a reduction in resource availability. The fewer resources available, the greater the distance the tortoises would need to travel in order to acquire the necessary resources. The small home range in the wet season may indicate an abundance of resources, but it may also be that large pools of standing water restrict the movements of tortoises. Understanding the spatial and habitat requirements of P. geometricus will help to assess the viability of populations in disturbed and highly fragmented areas, and contribute to the conservation efforts for this endangered species.
Rehabilitation as a method of understanding vegetation change in Paulshoek, Namaqualand
(University of the Western Cape, 2005) Simons, Liora-lee; Allsopp, Nicky; Knight, Richard; Faculty of Science
Heavy grazing of rangelands in the succulent karoo has placed the biodiversity of these areas at risk. In Paulshoek, overgrazing has resulted in the removal of much of the palatable vegetation from low lying areas. The remaining vegetation is dominated by Galenia africana, an unpalatable shrub. Loss of favourable microsites, competition from Galenia africana, as well as loss of seed banks, may be the cause of poor seedling establishment of palatable species. I explored how high grazing pressure has changed this system by comparing with surrounding private farms, which have a history of less concentrated grazing pressure. I found that heavy grazing increased the seed bank of Galenia africana in the soil and reduced that of palatable perennials. Vegetation cover was significantly lower (p<0.0001) under heavy grazing and consisted mainly of Galenia africana and few palatable perennials. The aim of this study was to test techniques that could restore this area to a more productive palatable shrubland. I propose that rehabilitation can be used to gain an understanding of the ecological factors that may be sustaining this altered vegetation state. My methodology involved biophysical interventions to manipulate this system. Grazing pressure was removed from the study area and vegetation changes were monitored under grazed and protected regimes. No change in plant cover was found after two years. However, there was an increase in cover of palatable perennials in relation to overall cover. I physically manipulated the environment by introducing microcatchments and brushpacks to act as traps for water, seed and organic material. These interventions resulted in few changes, however, I found higher soil moisture levels in microcatchments and under brushpacks than open positions. Cover of ephemerals was also significantly higher (p<0.001) in areas that had been brushpacked. In the absence of a seedbank, I tested whether the introduction of seed would result in recruitment. Seed of four palatable perennial species was sown into open, packed and tilled soil. A low number of seeds germinated in the first year and most seedlings died. Further germination occurred after a rainfall event in the second year, but still in very low numbers. Various microhabitats were implemented to assess seedling establishment requirements. Seedlings were transplanted in microcatchments and open positions; in areas cleared of Galenia, under adult Galenia and brush packs and in bare soil. Microhabitats did not facilitate seedling establishment, and few seedlings survived. Survival of seedlings was influenced by the size of seedling at transplantation and site differences. I conclude that the factors underlying vegetation change are complex. Individual physical and biological interventions offered no immediate change in vegetation cover and composition. However, a combination of interventions may over time and under favourable climatic conditions allow the return of a viable palatable shrubland.
Monitoring of heavy metals in the Bottelary River using Typha capensis and Phragmites australis
(University of the Western Cape, 2005) Ma, Ying; Raitt, Lincoln; Faculty of Science
The aim of this study was to use plants to determine the degree of heavy metal contamination in water and sediments in order to effectively monitor and provide possible recommendation to improve the water quality in the aquatic ecosystem of the Bottelary River.
Adequacy of existing protected areas in conserving biodiversity at global and regional levels in relation to socio-economic conditions
(University of the Western Cape, 2005) Gaika, Lindiwe; Knight, Richard; Faculty of Science
At a meeting of worl leaders at the United Nations Conference on Environment and Development in Rio de Janeiro in 1992, it was recognized that because of the tremendous increase in the size of the global populations (which now is estimated to exceed six billion), there were concerns that global biodiversity was at risk if insufficient land were not put aside for conservation within formal Protected Areas. The primary aim of this study was to compare investment in Protected Areas in relation to socio-economic conditions at global and regional levels.
Temporal and spatial variability in copepod abundance, distribution and community structure off Walvis Bay in the northern Benguela Current, 1979-1981
(University of the Western Cape, 2005) Tsotsobe, Sakhile Vincent; Gibbons, M.J; Verheye, H.M
The zooplankton samples used for retrospective analysis in this study form part of the historical SWAPELS (South West African Pelagic Egg and Larva Survey) collection from January 1972 to December 1989, which covered the entire Namibian shelf. The SWAPELS Programme was initiated following the collapse of the Namibian sardine fishery during the late 1960s and early 1970s. This study investigates variability in the temporal and spatial distribution of total zooplankton (non-gelatinous) biomass, total copepod abundance, as well as copepod community structure off the coast of Walvis Bay along, primarily, transect 70 (23° S), and secondarily, transects 66 (22°67 S) and 74 (23°33 S), over the period 1979- 1981. Included in the data set are sea surface temperatures (SSTs) and surface salinities, allowing for spatio-temporal trends in the hydrology of this region to be examined. Despite extensive variability in SST (1 1.27- 18.15 °C), the most frequently occurring SSTs were in the 15-16 °C range. In 1979 salinities ranged mostly between 35.1 and 35.2, whereas in 1980 and 1981 modal salinities fell within the 35.0-35.1 and 35.2- 35.3 ranges, respectively. A clear seasonal pattern in the cross-shelf distribution of SST and salinity was observed in 1979-80, when, generally, warm , high-salinity water covered most of transect 70 (23° S) in summer to early autumn. In spring the cool inshore water extended seaward, to recede again into summer. The existence of cool inshore surface water from mid-winter to mid-spring, warming up into summer and extending offshore, was indicative of a typical upwelling cycle off Walvis Bay.
The relationship between sediment composition and infaunal polychaete communities along the southern coast of Namibia
(University of the Western Cape, 2005) Clarke, Dylan Thomas; Gibbons, Mark; Paterson, Gordon; Faculty of Science
This study examined the relationship between sediment structure and infaunal polychaete communities off the southern coast of Namibia from two separate sets of data, and a total of ninety-two samples. It also examined whether a selected group of organisms (polychaetes) could provide the same level of information regarding community structure, as the entire fauna, at a number of taxonomic resolutions. A total of 44 samples were collected by De Beers Marine (Pty) Ltd in 1999 off the southern coast of Luderitz from depths between 40 m and 90 m. The sediments varied from soft muds (45 μm) to gravel (> 710 μm). Forty-three morpho species of polychaetes were distinguished, of which only 28 known species of polychaetes could be positively identified, which suggests that more information on the diversity of polychaetes in the region is needed. The fauna was dominated by species in the Ampharetidae, Capitellidae, Maldanidae, Spionidae, Lumbrineridae, Flabilligeridae, Nephtyidae, Pectinariidae and Onuphidae. Multi-variate analyses using PRIMER indicated that communities were structured by mud (45 μm) and very fine sand (45 - 63 μm) and gravel (> 710 μm). Mud and gravel, although selected by the BIOENV procedure as accounting for some of the variation in the polychaete assemblage structure, explained no more of the data (in combination) than did mud on its own. As similar clustering of samples was observed when the data were analysed at both the family and species-level, suggesting that the same level of information was being gained at the two taxonomic levels. The results of the BIOENV analyses were also broadly similar for both taxonomic levels of analyses, in terms of both the proportion of the variation in assemblage structure explained by the selected environmental variables and the choice of selected variables. These results suggested the information gathered at the polychaete family-level were equally clear when they are collected at the family-level for the entire infauna. The use of polychaetes (to the family-level) as surrogates, using sediment structure and depth was independently investigated from a total of 48 samples that were collected by De Beers Marine (Pty) Ltd in 2001, from depths between 20 m and 110 m. The sediment varied from mud (< 63 μm) to gravel (> 710 μm). Twenty-two families of polychaetes were distinguished, the fauna showing an abundance of Capitellidae, Cirratulidae, Flabilligeridae, Lumbrineridae, Magelonidae, Nephtyidae, Paraonidae, Pilargiidae, Onuphidae, Syllidae and Spionidae. Striking differences were found in the amount of variation accounted for in the biological samples by the environmental data. Interestingly, depth in combination with a particular sediment size fraction featured very strongly in structuring both sets of communities. The biotic patterns in the family-level total infauna were not similar for the polychaetes (at the same taxonomic resolution). These results suggested that one group of organisms (polychaetes at the family-level) may not be useful as a proxy for the entire infauna (at the family-level). Because of the contrasting results that were obtained in 1999 and 2001, the biological data in 1999 were pooled and the environmental data (sediment size fractions) were adjusted accordingly (i.e. some of the differences in the results may reflect differences in the methods used to collect data). Consequently the results still did not adequately explain why there was a low level of similarity between the total infauna and polychaete family-level biotic patterns in 2001. It seemed that pooled data improved the taxonomic resolution (amount of variation obtained), but when the sediment size fraction data were adjusted, it lowered the amount of taxonomic resolution. The results suggest that comprehensive and standardized samples must be collected to fully understand the relationships between biotic patterns and environmental variables. This is potentially important given the costs involved and the potentially long lasting value of the material collected. These sediment and biological samples were collected by industry (for baseline biological monitoring in the mining industry, and not academic purposes). Proper protocols need to be established which allow industry-related monitoring programs to make a real contribution to our understanding of the biodiversity and ecology of the area.
Patterns of resource use by livestock during and after drought in a communal rangeland in Namaqualand
(University of the Western Cape, 2006) Samuels, Mogamat Igshaan; Allsop, Nicky; Faculty of Science
Pastoralists in Africa have developed complex mechanisms by which they can alleviate the threat of drought. They practice mobility as one of the strategies to avoid the worst effects of natural stress and disperse grazing pressure. In the past in South Africa, the indigenous Nama people occupied large areas of land and moved around extensively to exploit seasonal differences in the availability of forage and water. With the settlement of the Europeans in the Cape the indigenous people lost most of their land to the colonists. The Nama people were, therefore, restricted to smaller rangelands and their patterns of rangeland use had to adapt to the spatial constraints. Descendants now herd livestock from semi-permanent stockposts that are scattered throughout the commons. Herders use a range of practices to manage their livestock. The aims of this study was to assess the agro-ecological knowledge of livestock keepers; assess the condition of the rangeland during drought; determine the herding strategies of herders during drought.
Granivores as ecosystem regulators of woody plant increasers in semi-arid Savannas of the Lowveld, South Africa
(University of the Western Cape, 2006) Petersen, Leif Michael; Moll, Eugene; Faculty of Science
In recent years, a global trend of increasing woody vegetation densities in semi-arid savanna habitats has been recorded, commonly described in South Africa as 'bush encroachment'. The shrubs and trees that do this (Increasers) have wrought significant economic and ecological impacts upon carrying capacities of large areas of savannas. This occurs, as suitable grazing areas are incrementally engulfed in shrubs and trees establishing new equilibria, from open savannas (essentially grasslands with scattered trees) into closed woodlands (treelands with scattered grasses). This thesis demonstrated a link between grass biomass, small mammal abundance and diversity, and their potential increaser seed/seedling predatory activities in the semi-arid Lowveld Savannas of South Africa.

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