LD2668 .T4 1950 C37 / Master of Science

Call number: LD2668 .T4 1950 I4 / Master of Science

Call number: LD2668 .T4 1952 A4 / Master of Science

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfilment of the requirements for the degree of Master of Science, 2017 / The African wild dog (Lycaon pictus) is one of South Africa’s most endangered carnivores. The species has suffered massive range shrinkages in the past few decades and population numbers have dropped significantly. Along with other factors responsible for its decline, one of the most notable threats to the African wild dog is conflict with humans. These carnivores are often persecuted by farmers for their alleged depredation of livestock and captive-bred game species, although doubt exists as to whether wild dogs are the avid depredators as suggested. My research therefore aimed to investigate the conflict between people and African wild dog, focussing on livestock depredation. Due to heterogeneous farming landscapes, the history and location of protected areas and the endangered status of the African wild dog, South Africa provides many opportunities to study this particular type of human-carnivore conflict. Firstly, I conducted a meta-analysis of human-carnivore conflict using published literature about African wild dog depredation of livestock and game and compared these to other African carnivores as well as non-African carnivores. Results indicated that African wild dog were less avid depredators than other African species such as lion (Panthera leo) and spotted hyena (Crocuta crocuta). Also evident was that high carnivore and livestock densities, coupled with poor communities with poor livestock husbandry practices, make people and carnivores in developing regions more vulnerable to human-carnivore conflicts. Secondly, I assessed actual African wild dog occurrence in relation to the location of farms, livestock density and several other anthropogenic and natural landscape features. This was achieved using GPS data from four collared African wild dog individuals from packs residing in the northeastern part of South Africa and resource selection functions. Results from these analyses suggested that, whilst African wild dog may occur in close proximity to farms, they established home ranges in areas of low livestock density and few farms, indicating predictive avoidance of areas where mortality may occur. Major roads were highlighted as a vulnerability for the African wild dog, whilst nature reserves and vegetation were also important predictors of wild dog occurrence. Other anthropogenic and natural landscape features varied in importance in determining wild dog occurrence. Knowledge about how the African wild dog selects its resources will enable us to identify vulnerabilities for these carnivores as well as areas where they are likely to occur, aiding in conservation planning. Though African wild dog have historically been reported to kill livestock such goats and cattle, my study seems to indicate that these carnivores are not avid stock-killers. Given the precarious survival status of the African wild dog and the food security needs of people in a developing region strongly suggests the need for cooperation of farmers and the education of communities to aid the recovery of this uniquely African carnivore. / XL2018

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfilment of the requirements for the degree of Master of Science. May 2013 / The purpose of the study was to isolate and identify indigenous nematode species and use them as model organisms for studying the responses of indigenous entomopathogenic nematodes (EPNs) to soil desiccation, soil rehydration, and also to study their behaviour with regards to the infection and location of insect larvae, Galleria mellonella in an 18cm column filled with sterilised sandy loamy soil. Two unknown nematodes were isolated from soil samples collected in Walkerville, South of Johannesburg and their sequences were found to have high affinity to Steinernema australe (accession number FJ235125) and Heterorhabditis bacteriophora isolate 56-C (FJ217351) when aligned with existing sequences in the NCBI database. Furthermore, a polymerase chain reaction was used to amplify the 16S rDNA region in order to identify bacterial symbiots of these EPNs. Symbiotic bacteria isolated from the Heterorhabditis spp had high affinity to Photorhabdus sp carborca (JF12345). Desiccation tolerance studies revealed that EPN5T and EPN3T were able to withstand desiccated conditions or continuous dehydration for 20 days. EPN5T caused 80% larval mortality after day 20 when the last row of Petri dishes was rehydrated. EPN3T caused only 60% larval mortality. All of the sandy controls gave 0% larval mortality by day 20. Comparative dose-response assays involved exposing G. mellonella insect larvae to different IJs concentrations (0, 5, 25, 100, 300 and 500 IJs/ml) were carried for both EPN5T and EPN3T. Larval mortality was recorded daily over a week. Insect mortality was high for both S. australe and H. bacteriphora, at 100IJs\ml, 300 IJs\ml and 500 IJs\ml. Mortality was observed within 48 to 96 hours and insects larvae showed signs of infection after 48hours. Significant differences were observed at EPN concentrations containing 5 IJs/ml and 25 IJs/ml. At these low IJ concentrations H. bacteriphora was able to kill 20% of the larvae by day 3 while S. australe displayed mortality only after day 4 and 5 for the two respective IJ concentrations. The significance of this observation was supported by the two-way Post-hoc analysis. Further studies were conducted to investigate the effect of soil humidity on EPNs behaviour in a column of soil. Results supported that humidity was crucial for EPNs locomotion or mobility and infection efficiency, as 100% mortality was observed in all columns by day 4. The study also investigated different IJ application concentrations in order to determine suitable field application doses. Even at the lowest IJ concentration of both EPNs 33.3% mortality was observed in each column. H. bacteriophora displayed increased mobility because high mortality percentage was obtained within 48hours in almost all three arenas of the column, proving that this species is an effective cruiser foraging deeper into the soil. S. australe was capable of cruising further down to 18cm searching for host as high mortality was observed even at the deeper or the bottom arena near the bottom of the soil column. Lastly field capacity was determined where the sandy loamy soil was saturated with water and allowed to drain so as to remove excess water from the 8 vertical columns for 48hours, resulting in a soil moisture content associated with the soil’s field capacity for water. Overall results of this study gave ideas for IJ formulation IJ storage and IJ application strategies of the identified EPNs which proved to have promising potential as biological control agents.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Year: 2016. / Entomopathogenic nematodes in the genera Heterorhabditis and Steinernema have emerged excellent as non-chemical alternatives for control of insect pest population. They have a specific mutualistic symbioses with bacterial symbionts in the genera Photorhabdus and Xenorhabdus, respectively. Native EPN species that are able to tolerate environmental stress including desiccation are of great interest for application. The aim of this study was to isolate indigenous EPN species from soil samples collected from Brits, North West province in South Africa, and to investigate their ability to tolerate desiccation stress. The second aim was to isolate the bacterial symbiont and sequence, assemble and annotate its whole genomic DNA. Insect baiting technique and White trap method proved useful in the recovery of nematodes from collected soil samples and infected cadaver, respectively. Molecular identification based on the amplification of the 18S rDNA and phylogenetic relationships revealed high affinity of the unknown EPN isolate 10 to Steinernema species and due to variation in evolutionary divergence distance, the unknown isolate was identified as Steinernema spp. isolate 10 . Isolates 35 and 42 revealed high similarity to Heterorhabditis zealandica strain Bartow (accession number: GU174009.1), Heterorhabditis zealandica strain NZH3 (accession number: EF530041.1) and the South African isolate Heterorhabditis zealandica strain SF41 (EU699436.1). Both Steinernema spp. isolate 10 and Heterorhabditis species could tolerate desiccation. Steinernema spp. isolate 10 was tolerant up to 11 days of desiccation exposure in loamy sand and up to 9 days of exposure in river sand, causing 26, 6% and 13, 4% cumulative larval mortality after 96 hours, post resuscitation by rehydration, respectively. Heterorhabditis spp. could tolerate desiccation up to 13 days of exposure and induced 26.6% cumulative larval mortality on both loamy and river sand after 96 hours post resuscitation. Swarming, aggregation, coiling and clumping behavioural characteristics were observed when Steinernema spp. isolate 10 was exposed to desiccation and Heterorhabditis species displayed no similar behavioural characteristics associated with desiccation tolerance. Morphological characteristics of the unknown Steinernema spp. isolate 10 have been described, and the thick cuticle and sheath which are both associated with tolerance to desiccation stress have been noted. The bacterial symbiont was isolated from larval hosts infected with Steinernema spp. isolate 10 and molecular identification through NCBI Blastn based on the 16S rDNA revealed high affinity to Xenorhabdus bacterial species. Phylogenetic relationships and evolutionary divergence estimates 16 revealed genetic variation and the species was identified as Xenorhabdus bacterial isolate. The genome assembly of Xenorhabdus bacterial isolate using CLC Bio revealed a total length of 4, 183, 779 bp with 231 contigs (>=400bp), GC content of 44.7% and N50 of 57,901 bp. Annotation of the assembled genome through NCBI PGAAP annotation pipeline revealed 3,950 genes (3,601 protein coding sequences (CDS) and 266 pseudogenes), 12 rRNAs and 70 tRNAs. RAST annotation revealed 55 of virulence, disease and defense subsystem features which are involved in the pathogenicity of Xenorhabdus bacterial isolate. The ability of EPNs to tolerate environmental stress is highly crucial and one of the determining factors for biocontrol potential and successful application, thus the indigenous desiccation tolerant EPN isolate, Steinernema spp. isolate 10 holds great potential as a biological control agent. The genome sequencing and annotation reveals insight to behavioural and physiological attributes of bacterial symbionts and this study will contribute to the understanding of pathogenicity and evolution of the bacteria–nematode complex. / GR 2016

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Bibliography: leaves 158-189. / x, 189 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1994