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Masters Degrees (Biological Sciences)

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    The marine aquarium trade in South Africa: a vector for alien invasive species?
    (2019) Wehr, Gitte Kirsten.; Macdonald, Angus Hector Harold.; Sink, Kerry.
    Biological invasions are increasingly recognized as a primary threat to biodiversity. Global transport and trade play an important role in the movement of alien species around the world, and as transport and trade have intensified over the decades, so too has the number of alien species introductions. As preventing the introduction of harmful species is a more cost-effective and efficient method to managing biological invasions, it is imperative that scientific studies are aimed at identifying the pathways responsible for introductions. The marine aquarium trade is an ever-growing business globally and only up until recently has been identified as a major pathway for the introduction of alien species. Except for the notorious cases of the invasive lionfish, Pterois volitans, and seaweed, Caulerpa taxifolia, the role of the aquarium trade towards the introduction of alien marine organisms has been largely unevaluated. With popularity rising for the marine aquarium hobby in South Africa, it is of concern that the trade remains predominantly unregulated. This study aims to investigate the risk posed by the marine aquarium trade as a pathway for the introduction of alien invasive species in South Africa. One such vector examined in this study is live rock: any type of rock or dead coral skeleton encrusted with, and containing within its crevices, a wide variety of marine organisms, including colourful sessile invertebrates and encrusting algae. A combination of morphological and DNA barcoding molecular identifications, based on the phylogenetic inference of mitochondrial cytochrome c oxidase subunit 1 (COI) and internal transcribed spacer region (ITS) sequence data, was used to assign identifications to 174 taxa harvested from imported Indonesian and Kenyan live rock. Of the 6 diverse phyla identified, one alien species was flagged as harmful due to its successful invasion of other ecosystems in the world: the glass sea anemone Aiptasia pulchella. Non-target DNA amplification of live rock associated taxa exposed the coral pathogenic bacteria Vibrio spp., further suggesting that the marine aquarium trade is also a pathway for the introduction of pathogens. A second component of the study involved the assessment, via formal survey, of the role that pet stores and hobbyists play in the introduction and transmission of marine organisms around South Africa. Irresponsible aquarium pest disposal methods and informal trading pathways were revealed highlighting the need for an education intervention to promote responsible aquarium ownership skills. The third part of the study entailed a national stock inventory of marine aquarium traded fish and revealed that the number of species traded is vast (n = 228) and that 60 % are alien to South African waters. Although the strength of this vector was not defined, this study confirms that the marine aquarium trade is a pathway for the introduction of alien and potentially invasive organisms and serves as the foundation for future research into marine aquarium trade vectors in South Africa. The findings and conclusions presented here should be considered by biosecurity monitoring and management initiatives.
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    Microbial community study of brine evaporation ponds: identification and analysis of the total organic carbon problem.
    (2021) Rambaran , Vrishthi.; Nemukula, Aluwani.; Joslin, Paul Anthony.; Naidoo, Yougasphree.
    Salt is an important compound as it is used by humans for everyday life. Salt production can occur from two processes: the use of seawater which is evaporated leaving the salt behind or the use of brine which is obtained from underground sources and undergoes the same process of evaporation as the seawater. The focus for this research will be on the microorganism population in salt produced from underground brine sources such as the source used by Botswana Ash (Pty) Ltd (Botash) which is the salt works that provided the samples for this research paper. The most important microorganism found in salt evaporation ponds is the green algae Dunaliella salina (D. salina) as discovered by previous studies. The main focus of this study was the identification of the microorganisms that are found within the salt evaporation ponds and the effect that the dominant D. salina population will have on the salt production process and also whether the dominant D. salina species can be used for production of important by-products to generate another source of income. The population genetics study on the samples from the various evaporation ponds at Botash has revealed the presence of many different microorganisms such as the bacterium Salinabacter, and the green algae Dunaliella salina which was revealed to be the dominant species. Other species such as archaea were also discovered within the salt evaporation ponds at Botash. The green algae D. salina was focused upon due to its dominance within the higher salinity ponds where it serves as the primary producer. The growth rate of the dominant D. salina species was observed in different conditions such as saline concentrations and different nitrogen sources. The results found that D. salina grows best at 3M salinity with NO3 or Urea as the nitrogen source. A study of the growth of D. salina when environmental factors were controlled showed that D. salina prefers high temperatures and high saline conditions for growth. D. salina also produces high value products such as beta carotene and Extra Polysaccharides (EPS). The production of these compounds are linked to the environmental conditions as it was found that beta carotene production is optimized when the cells are placed under stress during nitrogen starvation. EPS production occurs under all environmental conditions. The results from this research paper show that if the microbial community is controlled and optimized useful by-products can be produced, whilst minimal harm is done to the quality of salt produced.
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    Identification of Macrourus species (Teleostei: Gadiformes) found near Prince Edward Islands in the Southern Ocean using molecular and morphological analyse.
    (2021) Shadamorgan, Vineshree.; Miya , Tshoanelo Portia.
    The genus Macrourus belongs to the family Macrouridae that consist mainly of deep-sea fish. Macrourus contains five species that have a polar distribution, with one species, M. berglax, found in the Atlantic Ocean, and the other four species, M. carinatus, M. holotrachys, M. whitsoni and M. caml, found in the Southern Ocean. The species found in the Southern Ocean are morphologically similar to each other and have overlapping distributional patterns, as a result there have been instances of misidentifications within this genus. Based on morphological characteristics, previous studies have grouped the Southern Ocean Macrourus species into two pairs, viz M. carinatus and M. holotrachys, and M. whitsoni and M. caml. Despite overlapping occurrence elsewhere, morphological studies conducted in the Prince Edward Islands (PEIs) located in the Southern Ocean, have identified only one Macrourus species, M. carinatus. Since there are known cases of species misidentification using morphological identification and distribution overlap within this genus, there is a need for a molecular study that will complement the morphological data. There are no published molecular studies that reviewed species identification in these islands. This study aimed to identify Macrourus specimens found near the PEIs using molecular and morphological analyses. This assessment was done by sequencing the cytochrome c oxidase subunit 1 gene, and by measuring and counting morphometric and meristic characters. The BLAST search which had a sequence similarity of 99 – 100%, showed that there are two species represented in this dataset which were identified as M. carinatus and M. holotrachys. This observation was supported by both the phylogenetic and haplotype network trees, which formed two distinct clades. On the other hand, the morphological data did not separate the two species, supporting previous studies that discovered high levels of morphological similarity between M. carinatus and M. holotrachys, which ultimately led to their grouping and/or misidentification. It can therefore be concluded that there are at least two Macrourus species inhabiting waters around PEIs, which are morphologically similar.
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    Phytochemical and pharmacological analyses of Embelia ruminata (E.Mey. ex A.DC.) Mez.
    (2021) Rambaran, Neervana.; Naidoo, Yougasphree.; Baijnath, Himansu.
    The discovery of novel phytoconstituents to treat a plethora of ailments has become urgent as the demand for phyto-resourced products has intensified. To complement the search for new phytoceutical products, the current dissertation propelled an investigation into the phytochemical and biological potential of a South African plant, Embelia ruminata (E.Mey. ex A.DC.) Mez. The vegetative structures (leaf and stem bark) and the reproductive organs (fruit and seed) of E. ruminata were sequentially extracted using hexane, chloroform and methanol. The subsequent phytochemical analyses, which included phytochemical tests, Fourier transform infrared (FTIR) and gas chromatography-mass spectroscopy (GC-MS) of the crude extracts revealed the presence of various pharmacologically bioactive compounds. Furthermore, the data from the radical scavenging investigations demonstrated that the methanolic seed and stem bark extracts (IC50 of 3.54 and 37.47 μg/mL, respectively) displayed potent scavenging activities compared with the standard butylated hydroxytoluene (IC50 of 91.09 μg/mL). Evidently, the radical scavenging results corroborated with the cytotoxic effects of the crude extracts, which indicated that the methanolic seed and stem bark extracts had strong anticancer activities against the cancer cell lines, i.e., breast cancer (MCF-7) and human lung cancer (A549). Additionally, silver nanoparticles (AgNPs) using the aqueous extracts of the leaf, stem bark and fruit of E. ruminata were synthesised and characterised by adopting a series of standard tests. The antibacterial potential of both the AgNPs and the crude extracts were evaluated and were distinctively more effective against the Gram-positive than the Gram-negative bacterial strains, with the AgNPs of fruit extracts synthesised at room temperature (23±2 °C) and the methanolic stem bark crude extracts showing the most promising activity. Two biomonitor strains, Chromobacterium subtsugae CV017 (short chain) and Chromobacterium violaceum ATCC 12472 (long chain), were used to test the quorum sensing (QS) violacein inhibition capacity of the respective extracts. Overall, the AgNPs and crude extracts displayed more effective QS inhibition against the long chain than the short chain biomonitor strain. Interestingly, the chloroform leaf, hexane and methanol seed extracts showed QS violacein inhibitory activities against both biomonitor strains, indicating the potential of these extracts against multiple bacterial strains. These findings provide evidence that E. ruminata is a possible source of potential medicinal compounds.
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    Feeding dynamics of invasive (Tarebia granifera) and native (Melanoides tuberculata) freshwater gastropods.
    (2020) Naidoo, Senine.; Carrasco, Nicola Kim.; Miranda, Nelson Augusto Fernandes.
    Tarebia granifera has invaded several South African estuaries, outnumbering native gastropods such as Melanoides tuberculata. Comparative feeding dynamics can aid in estimating and understanding invasion impacts. This study aimed to explore the feeding dynamics of these gastropods with the use of two different approaches. Stable Isotope Analyses (SIAs) were used to investigate the dietary preferences and niche overlaps in the St Lucia Estuary, while Functional Response Experiments measured the relationship between the consumption rate of a food resource and its availability. These experiments were run both with and without the presence of heterospecific chemical cues (secondary metabolites secreted by either species) to determine whether chemical cues influence the functional responses of T. granifera and M. tuberculata. Mixed species experiments were also conducted to observe individual behaviour (active, inactive and feeding) over time and measure resource consumption when both species are placed together under high and low food availability. The SIA showed that both gastropods exhibited generalist diets, however, due to niche partitioning, there was no significant difference in their dietary niche overlap. In the FR experiments, both species exhibited Type II FRs and had similar feeding rates. However, in the presence of heterospecific chemical cues, M. tuberculata exhibited a higher feeding rate at high food availabilities, whereas T. granifera showed efficient feeding dynamics under limited food resources. In the mixed species experiments, T. granifera spent more time feeding under low food availability while M. tuberculata spent more time feeding under high food availability. This study showed that in certain conditions (e.g. high resource availability) the alien species did not always have a feeding advantage. A multiple method approach is recommended when assessing ecological impacts of invasive species.
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    Decadal changes in rocky shore communities in KwaZulu-Natal and survey methods for future monitoring.
    (2020) Mvula, Philile Emelda.; Macdonald, Angus Hector Harold.; Pfaff, Maya Catherine.
    Intertidal rocky shores form part of the sea during high tides and part of the land during low tides. They are therefore subjected to diverse anthropogenic pressures, including climate change, pollution, coastal erosion and harvesting. Due to their accessibility, rocky shores are among the most heavily exploited marine ecosystems. The rocky shores of the East and the South coasts of South Africa have been exploited for thousands of years. With growing coastal populations, they require management practices that ensure their ecological integrity and function. Rocky shore community structure along the KwaZulu-Natal (KZN) coast has been well studied between the years 1996 and 2000 when surveys were conducted at 39 sites. A monitoring Programme has since been established by Ezemvelo KwaZulu-Natal Wildlife in partnership with the Department of Environmental Affairs, Forestry and Fisheries (DEAFF) to inform the management of these heavily impacted ecosystems. This study aimed to contribute to the monitoring Programme in two ways: Firstly, by characterising and evaluating changes in rocky shore communities that have occurred since 2000, which was done by resurveying historical sites and comparing community structure and diversity between decades. Secondly, by comparing and evaluating different rocky shore sampling methods to identify the most suitable sampling protocol for a long-term monitoring programme of KZN rocky shores. This required statistical analyses of parallel surveys conducted using different methods. Significant changes in the community structure were observed with increased species richness and evenness. A decline in the abundance of harvested mussels was also noted, coupled with an increase in coralline algae and the arrival of two species of alien barnacles. Even though more long-term studies will be required to determine the status of the intertidal communities under anthropogenically induced change, the current study can be used to initiate better managementpractices in order to maintain species diversity and distribution.
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    Population connectivity of stylophora pistillata and sinularia brassica between KwaZulu-Natal marine protected areas.
    (2021) Gilmore, Jessica Rose.; Pearton, David James.; Macdonald, Angus Hector Harold.
    Marine Protected Areas are a valuable tool for ecosystem protection and to enhance resilience in the face of global stressors such as global warming and ocean acidification. There is currently an incomplete understanding regarding the level to which MPAs in KwaZulu-Natal protect existing biodiversity and provide benefits beyond their boundaries. The focus of this study was to determine the extent to which the current MPA network acts to facilitate connectivity of sessile benthic species, the role of oceanographic processes, and whether these processes will persist under global change. The population connectivity of two coral species, a hard coral (Scleractinia), Stylophora pistillata, and a soft coral (Alcyonacea), Sinularia brassica, within and between the MPA network on the east coast of South Africa was studied using both traditional markers and RADSeq, a reduced representation genomic sequencing technique. Sampling locations were selected in three existing MPAs and on a representative reef located in the “gap” in between. These MPAs span the tropical Delagoa and subtropical Natal Bioregions. Stylophora pistillata in South Africa is split into two non-hybridizing clades with clear differences in distribution. Clade 2 was confined to the subtropical Delagoa bioregion whereas clade 3 was found throughout the study region from the tropical Delagoa bioregion down to the southern boundary of the warm temperate Natal bioregion. ITS data indicated that there is a complex population structure of the clade 2 potentially driven by a combination of currents, ecological selection, and distance. A subset of Stylophora clade 2 samples was analysed using a RADSeq approach which clarified the structure suggested by the ITS data and clearly identified three distinct populations across four reefs (Leadsman Shoal, Blood Reef, Aliwal Shoal and Aliwal Deep) spanning the Delagoa/Natal biogeographic break. These populations did not appear to be structured solely by geographic distance, with one population comprising samples from two sites (Blood Reef and Aliwal Deep) that were non-adjacent and at different depths (12-18 m vs >30 m), while a geographically adjacent population (Aliwal Shallow) at 12-18 m constituted a distinct population. This suggests that ecological selection might be involved in structuring the population over short distances for this coral. Sinularia brassica was not found south of the iSimangaliso Wetland Park in this study, despite it being recorded in the southern sites in previous surveys. Analyses of COI and mtMutS sequences revealed that there are potentially multiple clades present in the IWP population and that there is a poleward decrease in genetic diversity. Neither of these clades showed any clear geographical or genetic population structure between the reef complexes but additional studies using RADSeq may help to clarify the situation.
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    Morphological and molecular characterization of Fasciola hepatica and Fasciola gigantica phenotypes from Mpumalanga and KwaZulu-Natal provinces of South Africa.
    (2020) Haridwal, Sayurika.; Mukaratirwa, Samson.
    Fascioliasis is a food- and waterborne disease. It is one of the most common helminthic infections in domesticated ruminants. The disease is caused by liver flukes, Fasciola hepatica and Fasciola gigantica. Increased attention has been geared toward studying these flukes due to their ever-expanding geographical distribution, enormous economic impact, increased human infections, increased resistance to treatment and the existence of hybrid forms. Both these species are co-endemic in the Mpumalanga and KwaZulu-Natal provinces of South Africa and even though, hybrids have been reported in other areas where both species exist it has not been attempted in South Africa. Therefore, this study was conducted to determine the existence of Fasciola hybrids in South Africa using morphological and molecular characterization. A total of 71 flukes were collected from naturally infected cattle slaughtered at abattoirs located in Enhlazeni and Nelspruit in Mpumalanga province and Pietermaritzburg in KwaZulu-Natal province of South Africa as well as control samples from Zimbabwe (Bulawayo abattoir) where only F. gigantica exist. The samples were categorized morphologically as either F.hepatica, F.gigantica, or Fasciola sp. The morphometrics (body length, body width, and length/width) were analyzed through a PCA and produced three distinct groups. A one-way ANOVA indicated that the length and length/width could be used to differentiate the species (P < 0.05) and the width was not useful in differentiating the species (P > 0.05). Molecular analysis based on ITS-1/5.8S/ITS2 marker showed that specimens morphologically identified as Fasciola sp were F.gigantica, with one sample morphologically identified as F.gigantica was molecularly identified as Fasciola sp. Similar results were observed with the CO1 marker, however, one sample came up as unknown, this sample however, formed a well-supported sister clade to F. gigantica. . It was also observed that aspermatic specimens are not only limited to hybrids, as some individuals that were molecularly identified as F. hepatica lacked sperm in their seminal vesicles. This study confirms species identification of F. hepatica and F.gigantica cannot be solely based on morphological characters where both these species are co-endemic. This was also the first study to report the existence of hybrid Fasciola spp. in South Africa.
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    The evaluation of the health status of Clarias gariepinus from the Inanda and Nagle dams in KwaZulu-Natal, South Africa.
    (2021) Mdluli, Siphosakhe.; Lebepe, Jefferey.; Vosloo, Dalene.
    The uMgeni River is one of the most polluted freshwater ecosystems in KwaZulu-Natal. This river is home to about 48 fish species. The study aims to determine the effects of water quality on the health of Clarias gariepinus from the Nagle and Inanda dams. Water variables were measured in situ using a YSI meter. Water and sediment samples were collected at three sites in each dam. Fish were collected and euthanized by severing the spinal cord. Different fish biometrics were measured. Fish tissues were preserved based on the analysis to be carried out. Neutral to alkaline water pH was recorded at both dams. Although the Inanda Dam exhibited higher total nitrogen concentration, both dams were mesotrophic, whereas the phosphate concentration at the Inanda Dam was eutrophic. Generally, the Nagle Dam showed good quality water compared to the Inanda Dam. The Inanda Dam fish population showed a relatively higher prevalence of alterations in the gills and liver than fish from the Nagle Dam. The degree of alterations showed some variability within each population, however, there was no significant difference (p>0.05) between the two populations. Both populations exhibited organ indexes less than 20, hence, moderate alterations. Fish ovaries and testis showed slight alterations at both dams. Acetylcholinesterase (AChE) brain activity recorded no significant difference in between the dams (p>0.05). Male populations recorded no significant difference in vitellogenin (VTG) induction between the dams (p>0.05). Despite, AChE activity and VTG induction showing no significant difference between the two populations, there was a great variability within each population. The lowest AChE activity as well as the highest VTG level were observed in the Inanda Dam fish populations. Both histopathologic and biochemical biomarkers are signs of increased pollution effect at the Inanda Dam. Nevertheless, it is evident that the uMgeni River system which is supposed to be providing sanctuary to aquatic biota is becoming deteriorated. These findings provide baseline data or a point of reference for future studies as it is the first of its kind in this river system.
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    Morphology, phytochemistry, and medicinal properties of South African Mangifera indica L. leaves for summer and winter seasons.
    (2021) Maharaj, Arvish.; Naidoo, Yougasphree.; Dewir, Yaser Hassan.
    Herbal preparations of plants continue to present mankind with novel remedies as many of these plants contain important secondary metabolites. Plant species of the family Anacardiaceae are rich in bioactive phytochemicals. Mangifera indica (Anacardiaceae) is an introduced and naturalised species to South Africa. Herbal use of this plant has not been fully documented; however, it is used in traditional medicine. This study aimed at characterizing the morphology, phytochemistry, and biological activity of Mangifera indica leaves harvested in winter and summer. The foliar biology of the plant was conducted by various microscopy techniques such as stereo- and Scanning electron microscopy. The length and diameter of the different trichome types were measured using ImageJ. The non-glandular trichome lengths range between 70 - 200 μm. The peltate gland trichomes consist of 2 rows of 8 oblong cells each with a size ranging from 32- 48 μm. Morphological observations using stereo- and SEM revealed the presence of non-glandular trichomes with cuticular warts and glandular peltate trichomes on the leaves of Mangifera indica. Transmission electron micrographs showed the presence of numerous mitochondria, starch grains, plastoglobuli, and plastids. The results for summer and winter leaves resembled somewhat similar-to-identical morphological characteristics on all fronts. For the phytochemical and biological assays, this study aimed to investigate some of the phytochemical and biological properties using different solvents (hexane, chloroform, and methanol) for extraction of the leaves of Mangifera indica for the summer and winter seasons. Preliminary phytochemical screening for the hexane, chloroform and methanolic extracts was done using a reflux extraction apparatus to uncover the presence of different metabolites and the anti-oxidant screening was done by the radical scavenging activity, which was established using the 2,2-diphenyl-1-picrylhydrazyl assay. Potent radical scavenging activity was exhibited for both summer and winter seasons with hexane and methanolic extracts for summer (IC50 of 19.53 μg/mL and 12.71 μg/mL respectively) and winter (22.32 μg/mL and 14.35 μg/mL respectively) in comparison to the control ascorbic acid which produced an IC50 of 3.20 μg/mL. The summer extracts had better radical scavenging IC50 capacity than winter extracts. The antibacterial activity of the methanolic leaf extracts for summer and winter of Mangifera indica were evaluated against the bacterial species: Gram-negative Escherichia coli (ATCC 25922) and Gram-positive: Staphylococcus aureus (ATCC ATCC 43300). For S. aureus (ATTC 43300), the summer crude extract displayed lower antibacterial activity than the control streptomycin, the summer extracts had a zone of inhibition of 14.17 mm while streptomycin had a 16.67 mm zone of inhibition. winter extracts had a zone of inhibition of 12 mm while streptomycin had a 13.67 mm zone of inhibition. For E. coli (ATCC 25922), the summer crude extract displayed higher antibacterial activity than the control gentamycin; the summer extract had a zone of inhibition of 18.05 mm while gentamycin had a 17.5 mm zone of inhibition. The winter extracts had a zone of inhibition of 8.5 mm. while gentamycin had a 14.5 mm zone of inhibition. Between seasons, summer had better antibacterial activity compared to winter for both Gram-positive and Gram-negative bacteria. Phytochemical screening showed the presence of phenols, flavonoids, tannins, and terpenoids, alkaloids, phytosterols, saponins, steroids, and carbohydrates. Potent radical scavenging activity was exhibited for the hexane and methanolic extracts for summer and winter, indicating that Mangifera indica is a potential source of medicinally important compounds. Antibacterial screening showed positive results with antibacterial properties for both summer and winter samples revealing its valuable biological activities. Summer overall performed better than the winter season. Future studies on this plant species are recommended to advance the use of indigenous herbal medicine or produce novel drug leads. To our knowledge, this study represents the first recent investigation in South Africa describing key foliar micromorphological features, phytochemicals, and biological activities of Mangifera indica L.
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    Spatio-temporal patterns of hover fly (Diptera: Syrphidae) diversity across three habitat types in KwaZulu-Natal, South Africa.
    (2022) Mva, Luhlumelo.; Van der Niet, Timotheus.; Midgley, John.; Jordaens, Kurt.
    Hover flies (Diptera: Syrphidae) are poorly studied in southern Africa and as a result, little is known about their abundance throughout the year. Hover fly abundance is generally expected to vary according to vegetation types, due to differences in the type and diversity of floral resources, but this has not yet been investigated in South Africa. This study aims to investigate temporal and spatial patterns of hover flies across three different, but adjacent habitats (forest, grassland, and plantation) in KwaZulu-Natal (South Africa). This was done in two ways, first, by analysing occurrence data from the Global Biodiversity Information Facility’s (GBIF) database across months of the year. Second, by quantifying fly presence and abundance using Malaise traps set up in three different habitats and supplemented with hand-netting data. The Malaise traps were set up from October 2020 - September 2021 and were generally serviced weekly. Hover flies were sorted and identified using available keys at the KwaZulu-Natal Museum. The KZN GBIF database contained 11 tribes that represented three distinct phenological patterns. The Karkloof GBIF dataset contained seven tribes that represented two distinct phenological patterns. The field collection dataset contained eight tribes that represented two distinct monthly patterns, although these slightly differed from the patterns found in the GBIF data. Most records were from January, September and December whereas few records were from May, June and July. Minimum-minimum, average-minimum, average maximum and average temperature showed a positive correlation with hover fly abundance. In terms of spatial patterns, grassland had the highest number of adult hover fly individuals (154), followed by forest (106) and plantation (20). There was an overall effect of habitat type on both the mean number of species and the number of individuals per trap per week. In addition, Shannon’s diversity showed variation among the three habitat types whereas Simpsons Evenness index showed no variation. The results show that hover fly populations remain active throughout the year, but with distinct fluctuations in their abundance. They also show that heterogeneous indigenous habitats such as grassland and forest represent high abundance, diversity, evenness and richness of hover flies and this may be due to the diversity in available microhabitats, compared to the plantation, which is a modified habitat that lacks microhabitat diversity. Nonetheless, further studies should be undertaken in different regions of South Africa to better understand the monthly patterns as well as the effect of habitat type on hover fly diversity.
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    The importance of sunbirds as pollinators of the southern African plants Alberta magna and Streptocarpus dunnii.
    (2023) Jansen, Cally Julia.; Johnson, Steven Dean.; Cozien, Ruth Jenny.
    Bird pollination is important for plant reproduction and is found in about 65 flowering plant families. I studied putative bird pollination systems of two southern African plant species, Alberta magna (Rubiaceae), which grows above cliffs and Streptocarpus dunnii (Gesneriaceae), which occurs among boulders in open grassland. A special emphasis of this study was to test the utility of close-focusing motion-activated camera traps for documenting bird pollination of plant species that are rare and occur in habitats that present challenges for conventional bird pollination studies. The aims of this project were to 1) quantify floral traits for comparison with other bird-pollinated species; 2) establish the breeding systems, including reliance on pollinators for reproduction; 3) identify floral visitors and measure their contribution to reproductive success; and 4) determine if seed production is pollen limited. Floral traits of S. dunnii, including large volumes of dilute nectar and long tube lengths, also aligned with an ornithophilous pollination syndrome. In naturally-pollinated plants, overall fecundity was high, with 80% of flowers developing fruits with large numbers of seeds. Malachite sunbirds (Nectarinia famosa) were the only legitimate visitor to flowers of S. dunnii. Greater double-collared sunbirds (Cinnyris afer), which have shorter bills than malachite sunbirds, occasionally rob flowers of nectar. Streptocarpus dunnii was found to be fully self-compatible but does not self-autonomously. Selective exclusion experiments showed that the species is almost entirely reliant on birds for seed production. The species did not experience pollen limitation, indicating that sunbirds are effective pollinators. Measured floral traits of A. magna, including large volumes of dilute nectar and long tube lengths, were consistent with an ornithophilous pollination syndrome. Motion triggered cameras and observations showed that southern double-collared sunbirds (Cinnyris chalybeus) and olive sunbirds (Cyanomitra olivacea) were the most common visitors to A. magna, while amethyst sunbirds (Chalcomitra amethystina) were occasional visitors. Selective exclusion experiments showed that bird visitors are important for reproductive success which was found not to be pollen-limited. The low levels of fecundity in A. magna indicate that there may be other potential factors that limit seed production in this species and the degree of self-compatibility in this species was not firmly established. I conclude that both species are specialized for pollination by sunbirds and that close-focusing camera traps are effective for documenting bird pollination systems of rare plant species which occur in habitats that are challenging for conventional human observations.
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    Assemblages of surface-active arthropods in pristine and disturbed savannah.
    (2022) Mavasa, Risuna Wain.; Tsvuura, Zivanai.; Yekwayo, Inam.; Mwabvu, Tarombera.
    Savannahs are structurally complex ecosystems rich in biodiversity, and the conversion of savannahs into human-modified landscapes poses a significant risk to organisms with limited dispersal abilities. Surface-active arthropods have limited dispersal abilities and are sensitive to changes in their environment; as a result, they are restricted to specific habitats with the resources that they need. Surface-active arthropods are essential in ecosystem processes, such as playing a direct or indirect role in water infiltration into the soil and its storage, decomposition of plant and animal matter, nutrient cycling, humification and biological pest control. Many landscapes of natural vegetation in South Africa have been transformed into croplands, residential and commercial areas. In Mpumalanga province, croplands (including fruit plantations) dominate the landscape where savannah vegetation occurred previously. This study investigated the influences of disturbance (transformed savannah vs pristine savannah) and season on the diversity of four groups of surface-active arthropods (ants, beetles, millipedes and spiders) in the savannah biome in Mpumalanga province. The objectives of the study were to determine 1) whether flightless arthropod assemblages differ between disturbed and pristine savannah, and 2) whether functional guilds of flightless arthropod assemblages differ between summer and winter. Field sampling using pitfall traps was done to collect the surface-active arthropods in pristine and disturbed savannah during summer and winter. All samples were sorted into morphospecies and identified into family or genus where possible and then assigned into functional guilds. Functional guilds were allocated based on the feeding habits of the surface-active arthropods, resulting in three distinct functional guilds (detritivores, herbivores and carnivores) being identified. Surface-active arthropods with diverse feeding habits were lumped to form a fourth functional guild, the “diverse functional guild”. I found significant differences in the species composition of ants, beetles and spiders between disturbed and pristine savannahs. The species richness and abundance of ants was significantly greater in the disturbed than pristine savannah, while beetles and spiders had similar species richness and abundance between the two habitat types. The number of unique species of the surface-active arthropods in the disturbed savannah were two times more than those in the pristine savannah. The species richness and composition of all functional guilds of the surface-active arthropods differed between summer and winter, with greater species richness in summer than in winter. Herbivorous and carnivorous arthropods had significantly higher abundance in summer than in winter, while the abundance of detritivores and the “diverse functional guild” was similar between the two seasons. This study shows that different vegetation types support different compositions of surface-active arthropods and that there may be a positive relationship between vegetation structure and the assemblages of surface-active arthropods in the savannah. Furthermore, the study highlights a potentially positive relationship between the assemblages of herbivorous and carnivorous arthropods. I recommend that it may be essential to consider both disturbed and pristine habitat types in the conservation of surface-active arthropods, especially in South Africa where most of the land is outside of formal conservation areas. This assertion is supported by the greater number of unique species of surface-active arthropods found in the disturbed than in the pristine savannah. My study provides relevant baseline information because little is known about the assemblages of surface-active arthropods in savannah landscapes dominated by croplands. Furthermore, my study gives some insight on how the assemblages of surface-active arthropods may respond to disturbance in the savannah.
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    Effects of high light intensity and desiccation stress on moss species.
    (2021) Mbatha, Sikhethile.; Beckett, Richard Peter.
    Bryophytes are desiccant tolerant non-vascular plants, capable of growing and surviving in extreme conditions. They are divided into three groups: liverworts, hornworts, and mosses. Most mosses grow in shady and moist environments, although some formpart of arid soil crusts where they protect soil from erosion. The moss flora of the Afromontane vegetation around Pietermaritzburg is dominated by two acrocarpous mosses, Atrichum androgynum, and Dicranella subsubulata. A. androgynum tends to grow in wetter, more shaded habitats and is a rather delicate species, while D. subsubulata grow in open, drier habitats and is more robust. Rarely, the species grow together, for example at the transition of a shaded indigenous woodland to plantations. We hypothesized that the more robust species has higher stress tolerance and has largely constitutive stress tolerance mechanisms. By contrast, we hypothesized that the more delicate species is less tolerant and may have inducible tolerance mechanisms. In the present study, desiccation tolerance and tolerance to high light stress were investigated in A. androgynum and D. subsubulata. Results confirmed that D. subsubulata was more tolerant of high light stress than A. androgynum. Exposure to moderate light intensities did not increase tolerance to subsequent high light stress in either species. Similarly, D. subsubulata was more desiccation tolerant than A. androgynum. Not consistent with our original hypothesis, mild desiccation, and treatment ABA-induced tolerance to desiccation in both species. Furthermore, detailed studies of the antioxidant enzyme peroxidase showed that enzyme activity was induced during slow drying in both D. subsubulata than A. androgynum. It appears that inducible tolerance mechanisms are present in both species. The work presented here represents a contribution to the autecology of two important mosses in the KwaZulu-Natal midlands Afromontane vegetation.
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    The curious case of the Satyrium neglectum complex: a taxonomic, ecological, and phylogenetic study.
    (2021) Rule, Matthew James.; Van der Niet, Timotheus.; Johnson, Steven Dene.
    Classical herbarium taxonomy uses a combination of morphological features from pressed specimens and distribution information as data in species delimitation. Whilst morphology is critical to species delimitation, additional information on phylogenetic relationships and fieldbased studies of ecology can inform taxonomic decisions. Satyrium neglectum Schltr. is a highly variable taxon currently comprising two subspecies, ssp. neglectum (Schltr.) A.V. Hall and ssp. woodii (Schltr.) A.V. Hall both of which are widely distributed in subtropical southern and eastern Africa. Variation in morphology and differences in apparent pollination systems, both between the subspecies, and within ssp. neglectum suggests the presence of two taxa within the current concept of the latter. This information, as well the exclusive reliance on herbariumbased taxonomy in the most recent species revision, formed the background to this re-evaluation of the systematics of the complex. A combination of detailed morphometrics and molecular phylogenetics demonstrated that the current concept of S. neglectum ssp. neglectum is inaccurate. A principal components analysis using traits measured from herbarium records from across the range, and ethanol-preserved flowers from South Africa, confirmed the presence of two morphologically distinct clusters within ssp. neglectum. Representatives from these two forms are separated along an elevation gradient. Bayesian inference using a combination of plastid and nuclear DNA sequence data revealed incongruent topologies. The nuclear topology is not consistent with current taxonomic boundaries, and revealed a separation between the high-elevation form and the low-elevation form of S. neglectum ssp. neglectum as well as ssp. woodii. The plastid data set also confirmed the separation of the high-altitude form of ssp. neglectum, but otherwise the topology reflects geography, as southern African accessions are separate from eastern African accessions. Floral scent was investigated in combination with published and novel pollinator observations in the Satyrium neglectum species complex. Floral scent composition and emission rates are mostly representative of associated pollination syndromes in previously published pollination work, with the exception of the high-elevation form. Published observations of ssp. woodii indicate that the species is pollinated by amethyst and the greater-double-coloured sunbirds, and the scent composition and emission rate is largely reflective of this. In addition, published observations showed a system of butterfly pollination in the low-elevation form of ssp. neglectum and long-proboscid fly pollination in the high-elevation form. However, new night time observations revealed additional pollination by settling moths in the high elevation form. These observations make sense in the context of the scent profile, which is dominated by compounds typically associated with moth pollination, such as phenylethyl alcohol and eugenol. In addition, two settling moths showed electroantennographic responses to the two dominant compounds in the scent bouquet of the high-elevation form. The compounds that dominate the scent of the butterfly-pollinated low elevation form are hexan-1-ol, octan-1-ol and benzyl alcohol, while previously published work on ssp. woodii showed that it is virtually unscented, and has emission rates that are markedly lower than other taxa pollinated by insects. Based on the morphological, phylogenetic and scent chemistry analyses, a case was made for the high-altitude form to be considered a separate taxonomic entity. This is formally described under the new name Satyrium basutorum. The analyses suggest that ssp. neglectum and ssp. woodii should be retained as subspecies, but a further investigation is required to identify the status of the eastern African synonyms Satyrium sceptrum and S. neglectum var. brevicalcar.
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    Varying soil nutrition in grassland and savanna ecosystems affect plant-microbe symbiosis, nitrogen nutrition and growth of Pisum sativum L.
    (2019) Zungu, Ntuthuko Sifiso.; Magadlela, Anathi.; Khoza, Thandeka Ntokozo.; Mathabe, Patricia Mmatshetlha Kgomotso.
    Abstract available in pdf.
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    Foliar secretory cavities of Vepris lanceolata (Lam.) G. Don (Rutaceae): micromorphology and chemical composition of the secretion.
    (2017) Nxumalo, Nozipho Ntombikayise.; Naidoo, Yougasphree.; Naidoo, Gonasageran.
    Secretory structures such as ducts, trichomes and cavities consist of cells that are primary sites synthesizing essential oils and other phytochemical compounds with medicinal properties. Little is known about the micromorphology of secretory structures and the composition of the chemical constituents. There was no information documented on the micromorphology of secretory structures of Vepris lanceolata (Lam.) G. Don (Rutaceae family). The aim of this research was to investigate the micromorphological characteristics of foliar secretory cavities, the chemical composition of the secretion, and the antibacterial activity of leaf extracts of Vepris lanceolata. Scanning electron microscope (SEM) images by chemical fixation and freeze drying revealed no external secretory structures on the surfaces of leaves. SEM images by freeze-fracture showed secretory cavities present in the leaf blade. The cavities were embedded amongst palisade and spongy parenchyma cells, next to the vascular bundle. Cavities were made up of the lumen surrounded by varying layers of epithelial cells, depending on the secretory phase of the cavity. Semi-thin and ultra-thin sections showed that foliar cavities develop schizo-lysigenously, i.e. cavities develop by both separation and degradation of epithelial cells. Transmission electron microscope (TEM) sections showed that during the secretory stage, secretory cells contained oil droplets, vacuoles and vesicles indicating active secretion. Histochemical assays of fresh leaves showed the localization of phytochemical compounds. Cavities turned orange red when stained with Sudan III indicating the presence of lipids and pink with NADI reagent to show essential oils. Cavities also stained positive for polysaccharides, sugars, phenolic compounds, proteins and alkaloids. Phytochemical screening showed the presence of alkaloids, glycosides, carbohydrates, proteins, tannins, phenolic compounds, flavonoids, fixed oils and fats. Preliminary thin layer chromatography (TLC) showed separation of bands indicating groups of active compounds in leaf extracts. Crude (ethanolic and methanolic) and water extracts of leaves showed antibacterial activity against gram positive bacteria Staphylococcus aureus (ATCC 25923) and methicillin-resistant Staphylococcus aureus (ATCC BAA-1683); and five strains of gram-negative bacteria: Escherichia coli (ATCC 25922), Escherichia coli (carbapenem-resistant) (ATCC BAA 2340), Klebsiella pneumonia (ATCC 314588), Pseudomonas aeruginosa (ATCC 27853), as well as Salmonella typhimurium (ATCC14026) according to the disc diffusion method. Leaf extracts have tannins, alkaloids, flavonoids, essential oil and flavonoids responsible for the antimicrobial activity of the plant.
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    Histo-phytochemical evaluation and characterisation of the foliar structures of Tagetes minuta L. (Asteraceae).
    (2018) Rikisahedew, Jesamine Jöneva.; Dewir, Yaser Hassan.; Naidoo, Yougasphree.
    Plants have been used as ethnomedicine for millennia. In recent years, there has been an upward surge of interest in the use of plants as medicine due to the interest in drugs with fewer side effects as well as the fight against antibiotic resistance. This study is based on Tagetes minuta, an aromatic essential herb that is cultivated for its high percentage essential oils which have been used in the treatment of various ailments. In addition, T. minuta contains a myriad of secondary metabolites that serve in numerous industrial and clinical applications. The aim of this study was to characterise the foliar structures responsible for the production, storage, and exudation of these useful compounds, as well as to examine the chemical constituents of the crude organic solvents derived from the leaves of T. minuta. The potential for green synthesis of silver nanoparticles from the crude methanolic extract and its potential as an antibacterial was also determined. Stereomicroscopy and scanning electron microscopy revealed the presence of uniseriate non-glandular trichomes on the foliar surfaces, as well as large pellucid secretory cavities. Histochemical analyses on the non-glandular trichomes showed that they are capable of storing various bioactive compounds, which is a novel discovery for this species. The development of the subdermal secretory cavities show that the cells undergo autolysis in order to form a schizolysigenous cavity in mature leaves, which was revealed using light microscopy. The ultrastructure of the secretory epithelium within the secretory cavity was analysed using transmission electron microscopy, which displayed the changes of the plastids to contain lipid molecules as well as an increase in vesicles indicating the presence of essential oils. Phytochemical analysis on the crude organic solvents derived from the leaves of T. minuta revealed the presence of alkaloids, sterols, saponins, terpenoids, phenols, and lipids. Gas-chromatography mass-spectrometry was carried out to reveal that the constituents with the highest percentage were 9-octadecen-1-ol (4.51 %), β-sitosterol (6.07 %), olean-12-en-3-one (7.47 %), and 3-methyl-1-butanol (14.77 %), all of which cause bacterial growth inhibition, as well as showing acaricidal activity, and anticancer properties in studies focussed on clinical applications. Silver nanoparticles were successfully synthesised from the methanolic leaf extract, which was confirmed using UV-visible spectroscopy and energy dispersive x-ray analysis. UV–visible spectrum of synthesised silver nanoparticles showed maximum peak at 442 nm, and transmission electron microscopy revealed the silver nanoparticles to be spherical in shape, ranging from 10 to 50 nm in diameter. Preliminary antimicrobial activity was determined using the agar well diffusion method, which showed growth inhibition against E. coli, S. aureus, methicillin-resistant S. aureus, B. subtilis and P. aeruginosa. This study has shown that T. minuta contains numerous bioactive compounds that have pharmacological and medicinal uses, as well as characterising the non-glandular trichomes present on the adaxial and abaxial leaves for the first time. The synthesis of silver nanoparticles from the methanolic extract of T. minuta in this study is novel, and shows promise for cheaper, more effective, and less risky nanotechnological applications.