Browsing by Subject "biological sciences"

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    An assessment of critical carbon services and water resources in South Africa’s terrestrial protected area network
    (2022) Plaistowe, Jonathan; Foden, Wendy; O'Farrell, Patrick; Hoffman, Michael
    Conservation planning can more greatly emphasise the importance of considering ecosystem services alongside biodiversity features to improve the planet's climate change resilience. Protected Areas (PAs) are a form of area-based conservation that successfully protects biodiversity and may conserve ecosystem services important for societal climate change resilience. This study assesses the performance of South Africa's protected area network in protecting strategic carbon and water services, which are important for climate change resilience. My first question investigated how well the country's PAs perform regarding the area coverage of carbon stocks and Strategic Water Source Areas (SWSA). My second question investigated whether the country's PAs have effectively protected the carbon stocks inside their borders. I hypothesised that the carbon stock values would be higher in PAs, given that PAs have successfully prevented the loss of natural land cover inside their borders. I also compared the effectiveness of PAs in protecting carbon stocks in terms of their management authority, province and land cover classes. I used existing datasets of PAs, environmental variables, SWSAs and carbon stocks for this study. Using the total organic carbon (TOC) and South Africa's Natural Land Cover, I calculated natural Strategic Total Organic Carbon Areas (STOCA). Then I used the STOCAs and SWSAs to assess the PA coverage of these two strategic ecosystem service areas and their overlapping areas. For the second question, I investigated the carbon stock values inside and outside PAs while controlling for environmental variables. I also investigated the effect of natural land cover, provincial designations and management authorities. Results indicate that South Africa's PAs cover 9.8% of the country's mainland but protect 14.8% of SWSAs, 21.7% of STOCAs and 28.5% of the SWSA & STOCA areas. The PAs have greater TOC, Total Soil Organic Carbon (TSOC) and Total Biomass Organic Carbon (TBOC) values inside their borders than outside. Natural areas inside PAs are higher in TOC, TSOC and TBOC values than outside natural or transformed areas. These results provide evidence that South Africa's PAs are effectively protecting their carbon stocks. Therefore, there is evidence that PAs are important for climate change mitigation and may be important for Nature-based Solutions (NbS) in increasing climate change resilience. Eastern Cape, KwaZulu-Natal, Limpopo, and Western Cape PAs should be studied to improve other PAs' management. Although the PA network is strategically placed to protect the country's ecosystem service areas, the extent of this protection is short of international PA targets. There are many more strategic ecosystem service areas available for protection. Considering the effectiveness of Eastern Cape and KwaZulu-Natal PAs and the availability of strategic ecosystem service areas for protection, policy-makers and conservation managers should consider these provinces for PA expansion. Limpopo should also be considered for PA expansion, given the high carbon stock values outside PAs. This study shows the importance of South Africa's protected area network for climate change resilience and provides information on where its necessary expansion can best be planned for. It also offers a potential set of metrics and targets for monitoring in the future.
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    Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift?
    (2019) Grey, Kerry-Anne; Cunningham, Susan; Midgley, Guy; Foden, Wendy
    Aloidendron dichotomum is predicted to undergo a south and south-eastern range shift in response to anthropogenic climate warming. Despite this, its range is suggested to be limited by low temperature extremes at the cool range edge and no such range shift has yet been confirmed. However, eco-physiological knowledge necessary to predict and detect this range shift is lacking. This study aimed to determine whether physiological performance of A. dichotomum differs at a regional and local scale, and if so, whether regional and local temperatures explain physiological differences. Performance metrics and temperature data were collected during summer at 14 microsites in two sites at the cool range edge of A. dichotomum. Microsites were stratified by aspect and elevation. This study confirmed that A. dichotomum is performing CAM photosynthesis at its cool range edge. Further, the results provide evidence for the temperature dependence of A. dichotomum’s physiological performance. Higher performance was associated with warmer nights and the warmer north facing slopes. This is in keeping with our hypothesis that A. dichotomum individuals at the cool range edge would take advantage of higher temperatures more typical of their core range areas. Opposing this, higher carbon gain was found at Gannabos - the cooler of the two study sites. This may be due to the less variable rainfall pattern at Gannabos. Furthermore, performance was higher on the flats where temperatures were also cooler. This may be due to lower water runoff on the flats compared to the slopes. As a result, I suggest that the cool range edge of A. dichotomum is limited both by low temperatures and rainfall variability and that, with warming, constraints on these populations are being removed. This is substantiated by the observed high levels of juvenile recruitment in these populations relative to others, and in time, is likely to lead to range expansion in the region.
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    Assessing conservation measures for five Southern African endemic shark species
    (2024) Cottrant, Emy; Underhill, Leslie; McCord, Meaghen
    The South African coast has one of the greatest diversity of Chondrichthyan species in the world with more than 190 species recorded, including 111 species of sharks. Many of these species are endemic to southern Africa (defined as the coastlines of Namibia, South Africa and Mozambique) but are poorly studied, despite their classifications of concern according to the International Union for the Conservation of Nature (IUCN) Red List. However, South Africa continues its efforts to protect the marine environment with a network of 42 Marine Protected Areas established; the Second National Plan for the Protection of Sharks was published in 2022. Sharks, which are characterized by slow growth and maturity at an advanced age, have undergone a rapid decrease in population sizes due to overfishing and habitat loss since the 1970s. To help fill the knowledge gap on endemic shark species, I used long-term datasets to study movement ecology and behaviour in marine protected areas. Study species are dark shyshark Haploblapharus pictus, puffadder shyshark Haploblepharus edwardsii, pyjama shark Poroderma africanum, leopard catshark Poroderma pantherinum and spotted gully shark Triakis megalopterus. Datasets were composed of non-lethal sampling comprised of mark-recapture, baited remote underwater videos (BRUVs) and acoustic telemetry. Results are then used to assess current protection status of those species and give advice to adapt management policies. The analysis of capture-recapture data made it possible to determine the distribution areas of each species in the study area as well as the differences in the size and location of these areas between different sexes and maturities. The efficacy of an MPA was discussed for the protection of those species, especially relevant for the puffadder shyshark, classified as “Endangered” on the IUCN Red List. Furthermore, a comparison between growth rate of wild and captive pyjama sharks helped assessing if captive data can be transposed to wild population in order to study endangered species. Study of the movements of T. megalopterus along the coasts of the Western Cape revealed that this species does not specifically use marine protected areas, regardless of sex or sexual maturity. This characteristic suggests that in the future, if the population declines, which is a potential consequence of being caught as bycatch in longline fisheries, it would be difficult for this population to recover. We also attempted to classify the different areas used by spotted gully sharks in order to identified priority areas for conservation such as nursery areas. The analysis of the BRUVs revealed that the classic analysis techniques were sometimes not adequate to study the relationships between species. The majority of published analyzes are based on MaxN, an estimate of the abundance of each species, often to estimate the effectiveness of marine protected areas and sometimes by extrapolating on the relationships between species within the food chain. During this project, we tested a new alternative metric (visual co-occurrence) that could be included in future analyzes of this type of video, the goal being to obtain a more refined view of reality and potentially increase knowledge about the role that a specific species plays within the ecosystem. Overall, the combination of the databases analysed during this project made it possible to increase knowledge on five endemic species of South Africa and southern Africa, specifically on their movement and differences between sexes in habitat use. The protection measures in place remain effective in maintaining these populations but, like H. edwardsii, do not allow these species to grow in abundance and thus change their IUCN status. In addition, a potential future decline for these populations due to global warming or anthropogenic impact, causing habitat loss, could be fatal for these species without specific protection measures for each species. Since 2022, several projects aim to increase the area of coastal zone covered by marine protected areas in South Africa, so the results of this study have a direct impact on future conservation and management measures for these species.
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    Comparative studies on Macrocystis pyrifera and Ecklonia maxima (Laminariales) in South Africa; investigating the use of M. pyrifera as abalone feed in South African aquaculture and assessing the vulnerability of these two species to Marine Heat Waves
    (2019) Fleischman, Michael J; Bolton, John J; Rothman, Mark D
    Macrocystis pyrifera is a kelp species found along many rocky temperate coastlines throughout the world. This species has been the focus of much research in recent decades, owing to its important ecological role, as well as its many commercial uses. Along the South African coastline M. pyrifera exists in eight known populations, over a limited ca. 200 km distribution. South African M. pyrifera differs from other global populations, as it is shorter in length and develops as small populations, often inshore of populations of the widely distributed and commercially valuable Ecklonia maxima. Very little research has been carried out on South African M. pyrifera. This thesis comprises two comparative studies on South African M. pyrifera, carried out with the aim of increasing our knowledge about the species in South Africa. South African abalone aquaculture has been increasing for many years and farmers are continually searching for new sustainable sources of abalone feed. As more abalone farms are built and existing farms expand, farms that use kelp as a feed, will likely require increased fresh kelp biomass in the future. The first study investigated M. pyrifera as a potential alternative source of supplementary fresh kelp feed for the South African abalone aquaculture industry. A six month comparative abalone feed inclusion trial and growth study was carried out, where the commercially farmed abalone species, Haliotis midae, was provided a diet of either E. maxima (the primary fresh kelp diet in the industry) + SAF 3000® formulated feed or M. pyrifera + SAF 3000® formulated feed. Haliotis midae fed with M. pyrifera + SAF 3000® displayed comparable growth rates to abalone fed a diet of E. maxima + SAF 3000®. No significant differences in the resultant mean Specific Growth Rate (M. pyrifera- 0.19 ± 0.01, E. maxima- 0.18 ± 0.01 % body weight.day-1 ; F= 0.180, df1= 1, df2= 192, p= 0.672), Daily Increment in Shell Length (M. pyrifera- 31.19 ± 2.59, E. maxima- 24.64 ± 2.31 μm.day-1 ; F= 0.853, df1= 1, df2= 192, p= 0.357) and mortality rate (t(10)= 0.263, p= 0.789) were identified between the two diets provided. Mean abalone Condition Factor also showed no significant differences among diets (M. pyrifera- 1.37 ± 0.01, E. maxima- 1.40 ± 0.01 g.mm-1), with the exception of month 2 (F= 4.014, df1= 1, df2= 224, p< 0.05). Additionally, H. midae consumed significantly less M. pyrifera (31.76 ± 2.83 %) than E. maxima (72.70 ± 1.26 %) (t(18)= 13.218, p< 0.05), suggesting potential differences in the Feed Conversion Ratio and/or kelp nutritional composition amongst these two kelp species. Macrocystis pyrifera could thus serve as a possible alternative supplementary kelp feed for the South African abalone industry. However, a sustainable source of M. pyrifera would be required. Moreover, further studies that examine the Feed Conversion Ratio, nutritional content and other important parameters relative to the use of M. pyrifera in aquaculture, should be established to reinforce these findings. At present, anthropogenic climate change arguably poses the largest threat to the world’s oceans. Rising ocean temperatures will increase climatic variability, leading to increases in the frequency, duration and intensity of extreme climatic events such as storms and Marine Heat Waves (MHW’s). The second study investigated the impact of MHW’s on both M. pyrifera and E. maxima recruits. Recruits of both species were exposed to an experimentally simulated MHW for a 72 hour period. Recruits were subjected to four temperature treatments: 15, 17.5, 20 and 22.5 °C. The impact of the simulated MHW on the samples was measured via photosynthetic oxygen production. Evidence of thallus deterioration in the samples was also recorded. The findings demonstrated that the thermal tolerance ranges and optima varied among the two species, with M. pyrifera displaying a greater sensitivity to the simulated MHW. Both species indicated minimal thallus deterioration at 15 °C and 17.5 °C. However, at 20 °C, 80 % of the M. pyrifera recruits and 40 % of the E. maxima recruits displayed signs of thallus deterioration. This increased to 100 % of M. pyrifera recruits and 80 % E. maxima recruits in the 22.5 °C treatment, exhibiting thallus deterioration. Mean oxygen production by M. pyrifera was greatest at 15 °C (1.42 ± 0.12 mg O2.g-1 DW.h1), with oxygen production significantly declining above 17.5 °C (F= 18.410, df1= 3, df2= 16, p< 0.05). Therefore, temperatures just above 17.5 °C likely lie at the upper end of the thermal tolerance range of South African M. pyrifera, with a thermal optima potentially existing at a lower temperature than what was tested. Mean oxygen production by E. maxima was greatest at 17.5 °C (1.92 ± 0.19 mg O2.g-1 DW.h-1) and was significantly reduced at 22.5 °C (F= 4.987, df1= 3, df2= 16, p< 0.05). Ecklonia maxima thus possesses a larger thermal tolerance range in comparison with M. pyrifera, with temperatures between 20 and 22.5 °C representing the upper limit of thermal tolerance for this species. The findings of this study highlight the threat of MHW’s to South African M. pyrifera and E. maxima. Furthermore, the findings assist in explaining the limited distribution of M. pyrifera along the South African coastline. However, further research is required to fully understand the implications of MHW and other warming events on the persistence of these two species in a climate change future.
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    Dedicated dads: a study on the nesting behaviour of Spondyliosoma emarginatum (Telostei: Sparidae)
    (2021) Faure, Beaulieu Nina; Attwood, Colin G
    Fish display the most diverse parental care behaviours within the animal kingdom. These behaviours are important from evolutionary and conservation perspectives as parental care is critical for the development and survival of the young. This study used video monitoring to uncover the nesting behaviour of an endemic southern African species of the Sparidae family, Spondyliosoma emarginatum (steentjie). S. emarginatum has evolved a nesting strategy by which males create nests on the seafloor for females to lay their eggs in. The eggs are fertilised and guarded by the male until they hatch. This species is particularly interesting as it has evolved a life-history strategy unique to the Sparidae, a combination of protogyny (female to male sex change) and male parental care. A compound nesting site with over 50 nests was discovered in 9 to 14 m depth in False Bay, South Africa. A large diversity in nest size and habitat was uncovered. The first nest with eggs appeared on the 3rd of September and this number gradually increased to a maximum of 26 nests on the 3rd of October. Eggs took from seven to nine days to hatch. During nesting, males were affected by stochastic weather events in the form of south-easterly gales. Nesting sites are likely limited to sheltered bays along South Africa's mostly exposed coast, and the optimal depth is probably a tradeoff between storm exposure and temperature. Deeper nests are expected in the east where the water is warmer. Nests were filmed daily to reveal how male behaviour changes before egg deposition and during egg development. After egg deposition, males increased their time on the nest from 30 to 52 minutes per hour. Nest defence included the regular clearing of invertebrate invaders (brittle stars, hermit crabs, sea cucumbers, and sea stars), and chasing away other fish species (sand gobies, Roman, and hottentot) and neighbouring male steentjies. Energy intensive behaviours such as clearing the nest and fanning the eggs remained constant irrespective of egg presence. In addition, males do not feed when guarding eggs, which explains the drop in male condition during spring. The revelation of this nesting site is useful for conservation and fishery management as the nests and nesting males are vulnerable to both fishing and seabed disturbances. Spondyliosoma spp. fulfil the requirements of the size-advantage model of protogyny. Their short life-span, in particular, their even shorter egg-laying life-span, classifies this species as an opportunist. This strategy may explain its success and numerical dominance in a wide range of biogeographic zones. The nesting behaviours shares much in common with freshwater opportunistic fish species and set it apart from the bulk of the Sparidae.
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    Elephant impacts on woody vegetation around artificial waterholes in Zambezi National Park, Zimbabwe
    (2020) Wilson, Luke; Hoffman, Timm; Cumming, David
    Elephant are renowned for their ability to substantially alter vegetation. However, as they need to drink regularly, surface water exerts a strong influence over the distribution and magnitude of elephant impacts on vegetation. This study was conducted in Zambezi National Park, a 560 km2 unfenced protected area in northwest Zimbabwe. It aimed to investigate the impacts of elephant on woody vegetation, particularly in relation to artificial waterholes. Sampling plots were located at different distances from four pumped waterholes in teak (Baikiaea) and Terminalia woodlands, the two main woody vegetation types recognised in the study area. Plots were set at 200, 500, 1000, 2000 and 4000 m from waterholes in the teak woodland. Due to the close proximity of waterholes, a lower maximum distance of 2500 or 3000 m from waterholes had to be used in the Terminalia woodland, but sampling intervals from 200-2000 m were otherwise the same. Assessment of elephant browsing and a series of measurements were performed on trees and shrubs within these plots, with plants assigned to one of three height classes (0.2 - < 1 m; 1 - <3 m and ≥3 m). Elephant dung counts were also conducted in these plots, to provide a measure of elephant occupancy. A clear decline in elephant browsing with distance from waterholes was evident in both the teak and Terminalia woodlands. However, elephant browsing was consistently higher in the latter woodland type. Averaged across all plant height classes, elephant had removed 30-45% of plant canopies in most Terminalia woodland plots. More moderate canopy removal of 10- 30% was found in most teak woodland plots. Plants ≥3 m were particularly highly browsed in the Terminalia woodland, with over 50% of their canopy volume removed in most plots. Elephant browsing impacts were also considered at the species level, which revealed clear differences in browsing levels among species. Some uncommon and highly browsed species were flagged as being potentially vulnerable to disappearance from the area, even in the teak woodland where overall elephant browsing was lower. The effects of elephant browsing on vegetation structure at different distances from artificial waterholes were also investigated. Little change was apparent in the teak woodland, where the only noted impact was a reduction in the density and canopy volume of plants 1 - <3 m tall, limited to within 1 km of waterholes. More pronounced structural impacts were evident in the Terminalia woodland. Substantial declines in the basal area and canopy volume of trees (i.e. plants ≥3 m) occurred closer to waterholes, with widespread conversion of woodland to shrubland evident. Reductions in both tree and shrub canopy volumes closer to waterholes also suggested a reduction in browse availability in the Terminalia woodland. Finally, elephant dung declined with distance to waterholes, confirming that elephant were found in higher densities closer to waterholes. However, dung counts did not reveal different levels of elephant occupancy between the two vegetation types, despite higher browsing in the Terminalia woodland. This finding suggests elephant might be using the teak woodland for purposes other than just browsing, such as for shade. The study thus provided evidence that waterholes have had a significant impact on vegetation in the area, particularly on the favoured Terminalia woodland. Acknowledging the tourism value of retaining waterholes in the area, it is suggested that distances between waterholes should be increased, through only continuing pumping at waterholes with viewing platforms. This could result in a more heterogeneous elephant browsing regime across the highly impacted Terminalia woodland in particular, and lessen further homogenisation of this vegetation type towards a shrubland.
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    Fluctuating human activity and associated anthropogenic food availability affect behaviour and parental care of Red-winged Starlings
    (2018) Catto, Sarah; Cunningham, Susan; Amar, Arjun; Sumasgutner, Petra
    Increased food availability associated with urbanisation is widely recognised as one of the key factors influencing avian demography. Temporal fluctuations in food availability, tied to variation in human presence, are of particular interest as they occur frequently in urban environments, but their impacts on the survival and reproduction of birds have not been particularly well-studied. In this study, I explored whether breeding Red-winged Starlings at a university campus in Cape Town, South Africa alter their behaviour and parental care of nestlings in response to fluctuating numbers of people and associated food over a relatively short timescale. I used data from nest watches and behavioural observations collected during both incubation and nestling periods to test whether differences in food availability due to day status (week days with thousands of students present versus weekends with substantially fewer students) affected a number of behaviours related to parental care. I found that, with less available food on weekends, parent birds appeared to trade off feeding their offspring for maintaining their own energetic requirements, meaning that nestlings received less food on weekends. I also found that parents preferentially fed their nestlings natural food on week days, despite an increased availability of anthropogenic food. This suggests that, with increased food availability, birds in this system may use anthropogenic food to supplement their own diets, allowing them to prioritise the feeding of natural food to their chicks. These results provide evidence that fluctuating food resources impact the behaviour and parental care of starlings, but it is still unclear what effect they have on the individual health of adult birds and their developing young. To further enhance our understanding of some of the ecological implications of urbanisation, future research should prioritise understanding the potential health impacts such a variable urban diet may have on the birds exploiting it.
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    Geographic range dynamics of South Africa's bird species
    (2014) Loftie-Eaton, Megan; Underhill, Les; Altwegg, Res
    A key issue in species conservation is a knowledge of the geographic ranges of species, and how these are changing through time. For birds there is a special opportunity to undertake studies of range changes, making use of the data collected by the First and Second Southern African Bird Atlas Projects (SABAP1 and SABAP2), which are separated in time by about two decades. In this thesis, I first describe the strengths and the weaknesses of the databases collected by these two citizen science projects, and therefore discuss the limitations placed on the analyses. We then undertake two sets of analyses, one focused on species, and one focused on areas. I show that, across all species, the Family to which the species belongs is an explanatory variable which explains approximately 45% of range expansion or contraction of a species. Diet and mass are also significant explanatory variables. For the analyses by areas, we demonstrate that the general encroachment of shrubs and trees in the savanna biome appears to have had a profound impact on the occurrence and abundance of a large suit of bird species, with the small insectivores and frugivores showing the largest increases.
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    Giraffa camelopardalis: limb bone histology through ontogeny
    (2020) Smith, Caitlin Caryl Danielle; Chinsamy-Turan, Anusuya; van Sittert, Sybrand
    Although there are many studies on mammalian bone histology, there are only a few that have examined the bone histology of artiodactyls, or focused specifically on osteohistological changes during ontogeny. The current study investigates the microanatomy and histology of giraffe limb bones through ontogeny. Mid-diaphyseal sections of humeri, radii, metacarpals, femora, and tibiae of 14 individuals representing individuals of known sex, as well as at different ontogenetic stages (foetal, juveniles, subadults, and adults). Thin sections were prepared for all the bones, and microanatomical (using Bone Profiler) and histological analyses were conducted on each of the sections. The study examined three main aspects, 1) Crosssectional shape changes in limb bones through ontogeny, 2) Histological changes through ontogeny in each of the limb bones, and 3) Histovariability among skeletons. The results of the study show that the foetus and juvenile individuals have round cross-sections, with small vacant medullary cavities, while cross sections of older individuals tend to be oval with variable amounts of cancellous bone surrounding the medullary cavity. The highest bone compactness values were obtained for the humerus and femur of the foetus, whereas the radius, metacarpal, and tibia bone compactness values are similar across the age classes. In terms of histology, this study found that the earlier ontogenetic stages had highly vascularised fibrolamellar bone in their cortices, which contrasts with that of the subadults and adults where more slowly deposited bone tissue occurs. These observations indicate that after rapid initial growth during early ontogeny, osteogenesis (and overall growth) slows down. This research also documents the fusion of the metacarpal III and IV, and the associated changes that occur in the histology. The study also highlights that the tibia is the only bone that has long radial vascular canals in the cortex. Overall the results of this study have provided a much better understanding of the bone histology of giraffes during ontogeny and has therefore filled an important gap in our knowledge of mammalian bone tissues. Furthermore, this study has direct implications for any future palaeohistological studies of fossil giraffids from Langebaanweg in South Africa.
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    Habitat correlates of pulse parameters in the highly specialised acoustic system of Chiroptera
    (2021) Finger, Nikita Maxine; Jacobs, David S; Holderied, Marc
    High Duty Cycle echolocating bats use high frequency echolocation pulses that have limited range but are clutter resistant i.e. can detect targets in dense clutter (the number of echoes produced other than those from the target of interest). A specialised echolocation pulse design (consisting of a constant frequency and frequency modulated components) facilitates foraging for prey in habitats characterised by dense vegetation or clutter. The constant frequency component, along with an acoustic fovea and Doppler Shift Compensation, allows them to distinguish small moving targets from stationary background objects. The frequency modulated components are thought to be used for depth resolution (i.e. ranging acuity). In contrast to their clutter specialist status, these species are found in a variety of biomes including open desert. A negative correlation between level of environmental clutter and frequency has been established for some species. The Foraging Habitat Hypothesis (FHH) proposes that the evolution of echolocation frequency is linked with changes in habitat clutter. In High Duty Cycle bats, the FHH predicts areas of low clutter should select lower frequency pulses because they are less susceptible to atmospheric attenuation making them more suited to long distance prey detection. Previous research has therefore focused on the methods by which bats vary the frequency of their pulses to achieve optimal propagation distances. However, the source levels of these signal emissions are also under control of the bat and must play a major role in signal propagation and therefore in detection of prey. My study tested the FHH by combining both an observational and experimental approach to determine how habitat clutter influences echolocation pulse divergence in High Duty Cycle bats. My focal species was Rhinolophus capensis, which has previously been shown to use different pulse frequencies apparently associated with differences in habitat structure. I focused on two populations, R. capensis in the fynbos (pulse frequency: 84 kHz) and R. capensis in the desert (pulse frequency: 74 kHz). Bats were recorded using a multiple microphone array in their natural habitat and in a flight room experiment where they were exposed to both a cluttered (simulating the fynbos biome) and open (simulating the desert biome) flight room. The experiment determined whether observed differences were a result of possible selection (as proposed by the FHH) or behavioural flexibility. A congeneric species, iii R. damarensis, was used as a control and additional test of the FHH because it inhabits the same desert biome as R. capensis but echolocates at a higher frequency (equivalent to the frequency used by R. capensis in the fynbos). In accordance with this hypothesis, I also tested if there were differences in the frequency modulated components of R. capensis pulses between biomes and whether these differences were due to possible selection for optimal ranging acuity in response to the degree of clutter in each biome. My results suggest the use of lower frequency echolocation pulses in R. capensis in the desert could have evolved for increased detection distance (as proposed by the FHH) but that lower frequencies may not be a prerequisite for successful foraging in open biomes. In R. capensis the greatest differences in prey detection between biomes was a product of both frequency and source level. However, higher source levels used by R. capensis in the desert had a greater contribution to observed differences in detection distances both within (emergence versus foraging area, cluttered versus open flight room) and between biomes (desert versus fynbos) than frequency. In addition, on average R. damarensis did not compensate for higher frequencies with higher source levels resulting in lower average detection distances than R. capensis in the desert. However, a few measurements of source levels for R. damarensis were the highest recorded and resulted in the largest prey detection distances recorded in my study. These findings support recent findings that suggest that SLs are energetically costly. In both biomes, bats used lower source levels when exposed to a cluttered versus open flight room. In the desert biome, bats actively lowered their source levels (compared to the source levels they use in the field) when exposed to a level of clutter that they do not experience naturally (cluttered flight room treatment). Unlike source levels, frequency (of the constant frequency component) was conserved during the flight room treatments. Frequency differences between R. capensis in the different biomes can therefore be attributed to possible selection rather than behavioural flexibility. The conservation of frequency prompted bats to vary their source levels to achieve appropriate detection distances when exposed to different environmental stimuli. Source level flexibility may therefore be the key to the capability of specialist clutter foragers to successfully hunt and survive in harsh open environments. To the same extent that source levels facilitate foraging in open environments, the frequency modulated components of High Duty Cycle bat pulses may facilitate the orientation and foraging of these bats in cluttered biomes. In accordance with the FHH, a strong correlation was found between the frequency (i.e. number of occurrences)/bandwidth of these components and the level of environmental clutter both within iv (between the two treatments of the experiment) and between biomes. The findings in my study highlight the importance of environmental pressures, such as clutter, in shaping the echolocation pulse parameters of bats.
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    Insular adaptations in the appendicular skeleton of Sicilian and Maltese dwarf elephants
    (2020) Scarborough, Matthew Edward; Chinsamy-Turan, Anusuya; Palombo, Maria Rita
    This thesis investigates the evolution of Pleistocene insular proboscideans from the centralwestern Mediterranean (Palaeoloxodon species from Sicily, Malta, Favignana) and a mammoth (Mammuthus lamarmorai) from Sardinia, with a particular emphasis on the anatomy of the limbs. Differences in the morphology of the limbs are examined across a tenfold reduction in mass (from 3,5m-tall P. antiquus from Germany to 1,2 m-tall P. ex gr. P. falconeri from Spinagallo Cave, Sicily), revealing insights into significant morphological changes in the long and foot-bones, particularly appendicular changes evident in SiculoMaltese P. ex gr. P. falconeri. Notable morphological differences between P. antiquus and its insular descendent P. ex gr. P. falconeri include the functional morphology of the ankle-joint (especially the calcaneus' articular facet for the tibia). Furthermore, morphological similarities found between the femur of young continental elephants (P. antiquus and L. africana) and adult insular dwarfs (P. ex gr. P. falconeri and its probable ancestor Palaeoloxodon sp. from Lparello Fissure, Sicily) suggest evidence of paedomorphism in the limbs. Similarly, comparisons of the ontogenetic allometry of the tibia in L. africana and P. ex gr. P. falconceri include changes which are also consistent with paedomorphism, although other factors could not be ruled out. In the humerus large differences are evident in the morphology of the deltoid tubercule between co-generic insular Palaeoloxodon species, suggesting interspecific differences in the musculo-skeletal system. Furthermore, on the basis of dimensions, morphology and stratigraphy, the large Palaeoloxodon sp. remains from Luparello Fissure, north-western Sicily are suggested to belong to the ancestral chronospecies of P. ex gr. P. falconeri from Sicily, which may have subsequently colonized Malta during the reduced sea-levels of a Middle Pleistocene glacial lowstand (following a corridor with reduced distances between the two islands). Additionally, morphological differences in the calcanei of elephants from Luparello Fissure, Sicily, and Benghisa Gap, Malta may be the result of allopatric speciation between similar-sized elephants during the Middle Pleistocene, or alternatively relate to ecomorphology. These findings suggest that the morphology of the calcaneus may be more informative than hitherto recognised for resolving systematics and taxonomy among the Elephantini. Furthermore, although the absolute chronology of SiculoMaltese elephants remains poorly constrained, preliminary U-Th dating at Alcamo Quarry, western Sicily suggests a tentative early Middle Pleistocene age for Palaeoloxodon sp.
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    Open Access
    Intergrative taxonomy and biogegraphy of ants in the genus Anoplolepis (Hymenoptera: Formicidae) in Southern Africa
    (2022) Ndaba, Abusisiwe; Janion-Scheepers, Charlene; Mbanyana-Nhleko, okuthula; Munyai, Caswell; van Noort, Simon
    Taxonomy has played an important role in biodiversity assessments. It provides an understanding of biodiversity components, data that are essential for making decisions on conservation and sustainable use and is also a foundation for phylogenetic studies. Although this field of study has played an important role in identifying and describing biodiversity, the issue of cryptic species has posed many taxonomic challenges. In most taxonomic groups, species with subtle differences and high intraspecific variation are often misidentified when morphological data is not supported by other methods, for example, genetic data. The genus Anoplolepis is one of several polymorphic groups of ants. Although this genus is widely distributed in the Afrotropical region, it is understudied. This study aimed to: 1) resolve taxonomic challenges of the ant genus Anoplolepis in southern Africa, including the production of updated identification keys for the species and the description of new species; 2) resolve taxonomic challenges of the ant genus using molecular data; 3) to understand and update the geographical distribution of species within Anoplolepis; 4) verify the existing distributional records for the invasive species, A. gracilipes in South Africa and monitor the main introduction pathways; and 5) to assess the overall changes in ant assemblages of ants collected between harbours and provinces and test the effectiveness of the pitfall trapping and baiting method in sampling ants. Material from various institutions and organisations were used to conduct this study, as well as new material collected. By using a combination of traditional morphological taxonomy and DNA barcoding, a total of 16 species were identified. Of these, 11 species were determined using morphological features and phylogenetic analysis based on molecular data, with the five remaining species being identified using only morphological features. Based on morphological assessment, one species (Anoplolepis sp. nov. 12) was deemed to be new to science. This study showed that the DNA barcoding method (CO1) was not efficient to delimit some of the species in this genus, highlighting the need to prioritize more fine-scale molecular markers, especially when working with polymorphic or cryptic species. Overall, the distribution of species in this genus shows that this genus is widely distributed across southern Africa. The invasive species A. gracilipes was not detected across all the sampled harbours, nor from any of the material housed at the Iziko Museums of South Africa, loaned from other institutions and organisations in South Africa and other countries used for this study. This is a positive outcome for conservation authorities. This species is highly invasive elsewhere in the world, and if introduced outcompetes native fauna and may result in ecosystem collapse. Although A. gracilipes was not detected in the samples from this study, early detection and eradication of this species should be prioritized. This can be done through existing pest monitoring programs at harbours, and thorough biosecurity measures. This study contributed to developing scarce skills such as the taxonomic identification and the descriptions of new species, increasing the barcoding database of ants in South Africa, and the overall revision of this economically and ecologically important ant genus.
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    Lion population status and ecology in a seasonally-flooded wetland, the Okavango Delta
    (2022) Kotze, Christen Robynne; O'riain, Justin; Loveridge, Andrew J
    The Okavango Delta in north-western Botswana, is a population stronghold for the African lion (Panthera leo). As lion populations are declining, there is a pressing need to develop conservation plans that can secure the future for lion populations in natural environments that face increasing anthropogenic pressure. The Okavango Delta is a dynamic wetland that undergoes significant ecological change in response to an annual flood pulse, the extent of which is determined by both short-and long-term climatic variation. The resulting fluctuations in landscape structure and resource availability affect all trophic levels. However, their effects on apex predators are not well understood. In this thesis, I examined which ecological and anthropogenic factors underpin population processes such as population density, home range size and resource selection of lions in the Okavango at various temporal and spatial scales, in order to better inform conservation plans for this population. As lions can be difficult to count, a situation made more challenging by a seasonally flooded environment, I first looked at camera trapping as a potential survey method for lions. With high resolution images, lions could be individually identified from trap images and spatiallyexplicit capture-recapture applied to produce reliable population estimates. Furthermore, spatial variation in density could be linked to environmental and anthropogenic covariates. Lion densities were highest along the floodplains, and were correlated strongly with vegetation productivity, but decreased with proximity to human settlements, suggesting an edge effect along the boundaries of the wildlife management areas. This edge effect may result from retaliatory killing in response to livestock predation by lions in adjacent community areas but could also be the effect of prey depletion from bushmeat harvesting along the Okavango's boundaries. As flooding can induce significant changes in landscape structure, I examined what effect this had on lion home range size at minimum and maximum flood extent. When floods were at their lowest, home range sizes of males were larger than those of females, which is typical of large carnivores. Females appeared to minimize the area used by prioritizing access to prey, and home range was also negatively correlated with habitat heterogeneity and island size and connectivity. Male home range sizes, however, were not affected by prey availability, but instead were negatively correlated with habitat heterogeneity and proportion of woodland, both of which are considered indices of high-quality habitat in this landscape. As higher quality habitat may result in higher female density, males may instead be trying to maximize access to areas which would have a higher density of females. At peak flood, however, males and females had similar range sizes, and home range sizes were positively correlated with dry land fragmentation. During high flood phases, lower availability of dry land, together with the need to increase home range size as land fragments, could exacerbate intraspecific competition for space, and potentially increase conflict with adjacent communities as floods displace lions towards the boundaries of the wildlife management areas. However, in extended phases of low flood, which could result from prolonged drought, rising 2 temperatures or excessive water abstraction for human use, habitat heterogeneity may decline, with potential negative effects on herbivore and lion populations. Consequently, both scenarios are predicted to ultimately reduce the carrying capacity for resident lions. Lastly, I examined seasonal resource use at a finer scale, and focused on how changes in flooding could affect the size of population cores in the Okavango and connectivity between these, and connectivity from the Okavango to surrounding areas. Seasonal habitat selection by lions mimicked shifts exhibited by large herbivores in other studies on the Okavango, and habitat selection was therefore likely driven by seasonal prey availability. After translating resource selection into resistance maps, I found that seasonal permeability of the landscape to movement differed significantly based on the flood levels. During maximum flood, the lion population within the Okavango becomes fragmented - the population cores in the central, southern and western Delta decrease in size and become isolated from the rest of the Okavango Delta. During both seasons, lions avoided areas close to people, and as a result, connectivity from the Okavango moving outwards to the south and west was limited. Connectivity towards Chobe National Park to the east, however, remained intact. Therefore, restoring connectivity with neighbouring sub-populations to the south and to the west of the Okavango, and reducing anthropogenic pressure on lions in these regions during high flood phases, will help build resilience for the Okavango's lion population and should be considered a conservation priority. Ultimately, the consequences of low and high flood scenarios for lions can serve as a proxy for protracted periods of 'dry' and 'wet' environmental conditions that could result from climate change or upstream water extraction. This study shows that both flood extremes, in the long-term, can be detrimental to the Okavango lion population. It also provides a framework for long-term monitoring of lions in this wetland to be able to detect population changes. The future of the Okavango lion population depends largely on compensating for impacts of climate change by minimizing upstream water offtake to maintain natural flood cycles and reducing other anthropogenic pressures. The results of this study may also provide insights into conservation challenges impacting big cat populations in wetlands elsewhere around the world.
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    Long-term ecosystem dynamics of contrasting grasslands in South Africa
    (2022) Dabengwa, Abraham Nqabutho; Gillson, Lindsey; Bond, William John
    Rainfall, fire, and grazing all control changes in vegetation and soil in grassland and savanna ecosystems. In these ecosystems, wetlands are key resource areas because they keep moisture and collect nutrients that support grass production. The grass production supports high grazer densities in landscapes, especially during dry climatic periods.
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    Mammalian and avian diversity in a coastal nature reserve and an adjacent eco-estate
    (2022) Ross, Michael; O'riain, Mannus Justine; Bronner, Gary
    The burgeoning human population is placing increasing pressure on natural resources, including undeveloped land, for a variety of human activities including residential housing. Despite making up only a small percentage (5.4 %) of transformed land, urban areas have had a disproportionate impact on biodiversity with many cities having been founded in biodiversity hotspots at the confluence of marine, freshwater and terrestrial ecosystems. A growing trend worldwide and particularly in countries with a large wealth gap is the development of low density private residential estates. Although primarily conceived to improve home security, private estates are nevertheless regarded as a form of geographical escapism, and they are increasingly being marketed as eco- and lifestyle estates. While no formal definition of an eco-estate exists nor what ecological criteria must be satisfied to qualify for the status of an “ecological estate,” increasingly such estates make bold claims concerning their contributions to the conservation of native flora and fauna. Currently, little is known about the impacts of eco-estates on the ecology and wildlife of an area, particularly when compared to natural land. To date, most research on estates has focused on comparing their impact with transformed, agricultural or even urban land uses. In this study I compare select elements of the fauna within a golfing eco-estate (Atlantic Beach Estate), located 25 km north of Cape Town to the neighbouring Blaauwberg Nature Reserve, from which the estate was originally cleaved. I used live trapping, camera trapping and point counts for small mammals, medium/large mammals and birds respectively to compare the fauna in both the estate and reserve. For birds I was able to include a before and after comparison with a similar study in the early phases of the estate's development. All fieldwork was conducted between September and November 2019. Small mammal diversity was similar within the estate and the reserve, but the former included an exotic invasive (the house rat (Rattus rattus)) while the latter supported the vulnerable white-tailed rat (Mystromys albicaudatus). Medium sized mammal species composition varied significantly between the estate and reserve with the latter having more native species and the estate having three domestic species in addition to an introduced, extralimital wild species, the springbok (Antidorcas marsupialis). Bird communities were similar, with marked overlap in species between the two land uses. The addition of permanent water and private gardens with both native and non-native flora has increased both the niche breadth and food availability within the estate which was reflected in a higher avian diversity than in the neighbouring, more homogenous, reserve. In addition to supporting almost all the species found in the reserve, the estate was able to support multiple fynbos-endemic species not found in the nature reserve, as well as species closely associated with water. The presence of the eco-estate does not appear to have negatively impacted the bird community as the additional resources provided by the estate allow both urban exploiters and urban tolerators/avoiders to persist. In summary the estate has adversely impacted medium sized mammals more than both small mammals and birds with the latter taxon arguably benefiting from the increased habitat heterogeneity. Improving medium sized mammal richness would require increasing the permeability of the estate boundary but this will compromise both the safety of residents from external human threats and mammals within the reserve from domestic animals originating from the estate. Restricting domestic animals to private property, eliminating exotic species, improving connectivity between patches of natural habitat and naturalizing the edges of the golf course are all attainable goals that may improve small mammal and bird communities within the estate. However medium and large mammals are seldom compatible with human habitation and are thus likely to be the faunal component most adversely impacted by eco-estates with their limited size and impermeable edges. Ultimately while eco-estates may offer habitat for some species, they are not uniformly suitable for all species, and particular attention must be given to characteristics of prevailing species which might preclude them from an estate before estate construction. Given the increasing popularity of eco-estates and increased pressure on wildlife these are important findings which can help improve conditions for wildlife on current eco-estates and help facilitate site selection for any future eco-estate construction.
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    Molecular phylogenetics, systematics, reproductive safeguarding and chromosome evolution of the genus Lachenalia (Asparagaceae: Scilloideae)
    (2025) Duncan, Graham; Verboom, Tony; Ellis, Allan; Forest, Félix
    The genus Lachenalia, comprising 142 species and belonging to the monocotyledonous family Asparagaceae, is morphologically diverse and the most species-rich member of the family in southern Africa. Past attempts to infer a well-resolved and robustly supported phylogenetic tree using Sanger sequencing of candidate loci and/or morphological characters have been largely unsuccessful. A new phylogenetic hypothesis for Lachenalia is presented, using multi-locus sequence data sampled from living material of 132 taxa via maximum likelihood and coalescent-based species tree estimation (ASTRAL), as applied to 378 hybrid enrichment loci. This resolves species-level relationships with good support, thereby providing a sound basis for a new infrageneric classification, revealing several new taxa which are described here, and, most importantly, establishing a solid framework for downstream evolutionary studies. A dated version of the multi-locus phylogenetic tree is employed here to test the hypothesis that pollen limitation, resulting from a low abundance of insect pollinators, promotes the evolution of reproductive safeguarding traits (self compatibility, autonomous selfing, bird pollination and clonal propagation) in low insect abundance contexts (i.e., infertile fynbos heathland, and species which flower outside of the austral spring season). Ancestral state reconstructions identify an association with non-fynbos vegetation and spring-flowering as ancestral, with the transition to fynbos and non-spring flowering having taken place multiple times. Ordinary and phylogenetic regressions suggest that bird pollination and self-compatibility are selected for in fynbos and in non-spring flowering lineages, with autofertility being positively associated with non-spring flowering. These patterns support interpretation of these traits as reproductive safeguarding adaptations under reduced insect pollinator abundance. The dated multilocus phylogenetic tree is also used to explore the evolution of cytotype and genome size in Lachenalia. Novel genome size data for 124 species are reported and reconciled with existing karyotype data to show that genome size variation is largely a product of polyploidization, with polyploidy yielding lineages that are mostly short-lived and recent. By contrast, dysploid change, which is frequent in Lachenalia but has little impact on genome size, yields lineages that persist through time and diversify. Lachenalia describes a dysploid reduction series with a high ancestral base number.
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    Phylogeny and biogeography of Southern African limpets in the genus Siphonaria in the context of a global phylogeny
    (2022) De Coito, Paula Marie; Branch, George; Hedderson, Terry Albert
    Abundant, diverse and ecologically important, the 'false-limpet' genus Siphonaria has a near world-wide distribution. However, arising from uniformity of shell shape among species and its plasticity within species, frequent synonymisations and changes of names have created uncertainty about the number of species that exist and the names that should be applied. In this thesis I pursue three lines of genetic research to address this. First, I resolve the species that exist in two South African complexes: the Siphonaria carbo complex and the S. concinna/oculus complex. Second, I examine what is currently accepted as S. compressa from the only two South African localities where it has been recorded, to determine if the two populations are conspecific. Finally, I compare the genetics of a selection of species from around the world to place the South African species within, and contribute to, a world phylogeny for the genus and analyse geographic patterns of clades emerging from this phylogenetic reconstruction. With respect to the 'S. carbo' complex, Teske et al. (2007), using mitochondrial and nuclear sequence data on Siphonaria nigerrima, S. anneae, and S. tenuicostulata, failed to discern distinct monophyletic lineages, and concluded that these species, together with S. dayi, are different colour morphs of a single species, merged under the name S. nigerrima. This contrasts with a previous systematic revision by Chambers & McQuaid (1994), which considered these to be four separate species. An added complication is that the name S. nigerrima has been synonymised with S. carbo by various authors and in a range of data bases. Using phylogenetic analyses based on COI and 16S ribosomal RNA genes and incorporating additional GenBank sequences of east coast species, I confirm that S. nigerrima and S. dayi comprise a single species, to be merged under the name S. nigerrima because of its priority, and because examination of the type material of S. carbo indicates that it is unlikely that that species is present in South Africa. However, I also show that within the 'S. nigerrima complex' there exist four or possibly even five clades that warrant recognition at a specific level, two of which constitute undescribed and unnamed species (nov. sp. 1 and nov. sp. 2) while the other three can be accommodated under the names S. nigerrima sensu stricto, S. tenuicostulata and S. anneae. Using the same approach, I examined the distinction between S. oculus and S. concinna, which has become blurred in the literature, with only the latter being recognised by Teske et al. (2011). Both my molecular analyses and a consideration of shell features provide evidence that the two are distinguishable and valid species. Siphonaria compressa was first described by Allanson (1958) from specimens found in Langebaan Lagoon on the West Coast of South Africa, where it is associated with the seagrass Zostera capensis. In 2005 a population of what was considered the same species was recorded in Knysna Lagoon on the South Coast. On the basis of COI and 16S analyses coupled with shell morphometrics I found that the two populations have no shared haplotypes and are clearly diverged; IMa2 estimates indicate there has been no migration between these populations and the split between them occurred around 730 000 years ago. Evidence points towards recently expanding populations at both sites. Uni-, bi- and multivariate analyses of 13 morphometric variables revealed that the means for most variables are significantly different and clear differences in shell shape, size and weight exist between the two populations. I thus recognise two geographically delimited species, and in this thesis I distinguish the Knysna population as Siphonaria nov. sp. 3. The fact that the populations are considered separate species has important ramifications for conservation. The third aspect of my thesis was to integrate the southern African species that I now recognised into the most recent global phylogeny of the genus (Dayrat et al. 2014), which focussed strongly on the Indo-West Pacific species and omitted all South African species. I sequenced 120 individuals collected from 51 localities including 11 southern African species - three of which I consider to be undescribed species - and 42 other species from around the world, nine of which were not previously included in any published phylogeny, thus adding a total of 20 species to the global phylogeny. In total, incorporating GenBank sequences, I analysed 272 mtDNA sequences (16S + COI, 1202 nucleotide characters) within a Bayesian framework. Sacoglossans were used as the outgroup as per Bouchet et al. (2017). Similar to Dayrat et al. (2014), two major clades, A and B, were recovered. The South African species were not monophyletic but their positions were clear and distinct and did not influence the original division of the genus into two major clades. The inclusion of the South African species led to a rearrangement of the tree topology, especially within clade A, where all bar one of the South African species were recovered, with the the highly divergent S. serrata occurring in the second major clade B. Within clade A all bar two of the South African species were retrieved in one clade. The exceptions were S. compressa and Siphonaria nov. sp. 3 which fell elsewhere within clade A and were more closely related to Pacific Ocean species. The contents of clade B remained similar to the previously published phylogeny with the exception of a significant rearrangement of the basal species. Although many species remain unnamed, six previously unidentified molecular units in the global phylogeny are identified here and assigned species names. I also explored biogeographic patterns for all recognised species in the genus. There were strong latitudinal trends evident in species richness with high diversity in the lower latitudes, but with a dip at the equator, in contradiction to the prevailing paradigm of greatest diversity at the equator. Species with direct rather than planktonic development had both smaller geographic and smaller average latitudinal ranges. Overall, this thesis encompassed a view of the genus from the small-scale withinspecies population genetics of the highly endangered and range-restricted S. compressa and its sister taxon Siphonaria nov. sp. 3, through the broader geographic delimiting of the species contained within two southern African species complexes, to the placement of all the southern African species within a global context by updating the world phylogeny of the genus.
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    Quantifying land-based sources of plastic pollution in South Africa
    (2020) Weideman, Eleanor A; Ryan, Peter
    It is widely claimed that at least 80% of the plastic litter entering marine environments comes from land-based sources, yet there is little empirical evidence to support this. Most studies to date predict the flux of litter from land to sea using global models based on a handful of field studies conducted mostly in developed, Northern Hemisphere countries; others use proxies such as per capita waste generation and proportion of mismanaged waste to predict litter loads entering the sea. It thus remains unclear how accurate these predictions are, particularly for African countries where few field studies have been conducted. Due to its rapidly growing human population, Africa is expected to become a much more significant source of litter into the sea. It is therefore important to identify major land-based sources of litter from the continent so as to implement effective mitigation strategies aimed at stopping this leakage of waste plastics into the marine environment. In this thesis I investigate two possible land-based sources of plastic pollution in South Africa. In Chapter 2 I show that stormwater run-off from Cape Town, a large coastal city, is a significant land-based source of litter into Table Bay. By placing nets over three stormwater outlets, each draining a different land-use type in the city, I estimate that some 70-630 tonnes of plastic litter are released as part of urban runoff from Cape Town each year which is a similar order of magnitude as estimates based on run-off litter collected in the 1990s and stranded beach litter. Overall, 40- 78% of litter items by count and 52-64% by mass was plastic, of which most was single-use packaging. Compared to a similar survey of the same three stormwater outlets conducted in 1996, litter densities by count decreased by 50% in two of the three catchments but increased threefold in the commercial/residential area. It is clear that urban run-off is a significant source of litter into Table Bay, but the total amount is considerably less than model predictions that identified South Africa as the 11th worst source of marine plastics from land-based sources globally. While several of South Africa's large cities are on the coast, the largest industrial centre and most densely populated part of the country is inland in the Gauteng Province. Much of this province lies within the catchment of the Orange-Vaal River system, which flows west across the country to eventually drain into the Atlantic Ocean. In Chapter 3 I present the results of two extensive field surveys to assess the amounts of plastic debris transported by the Orange-Vaal River system into the sea. By sampling for micro- and macro-plastics at 33 bridges spanning the lengths of both the Orange and Vaal rivers I show that densities of larger plastic items were highest at sites in the densely populated and highly urbanised upper reaches of the Vaal River, while microfibres were particularly abundant in the arid, sparsely populated lower reaches of the Orange River at the end of the wet season. It therefore appears that the Orange-Vaal River system may be a source of microfibres to the Atlantic Ocean, but most larger plastic items are retained near point sources in the upper reaches of the Vaal River. The Orange-Vaal River system thus does not appear to be a major source of plastics into the Atlantic Ocean and there is considerably less than the 0.095 tonnes·yr-1 predicted to be washed out of the Orange River by global models. I also investigated whether dams retain microplastics and microfibres within their reservoirs by collecting bulk water and neuston net samples from above and below the walls of the five major dams in the Orange-Vaal River system. I present these results in Chapter 4 and show that microplastic and microfibre concentrations were highest in dams on the densely populated Vaal River during dry conditions, whereas the opposite pattern occurred at dams farther downstream or on the sparsely populated Orange River during wet conditions. Overall, microplastic and microfibre densities were similar at sites collected above versus below dam walls and there was no significant correlation between microplastic and microfibre densities at a site and the distance from the site to the dam wall. Dams therefore do not appear to trap floating microplastics and microfibres, although the data were noisy (average CV = 184%) and so provide only a rough estimate of differences in plastic densities among sites. Lastly, in Chapter 5 I summarise the main results from the previous chapters and present recommendations for future research. Combining the findings from Chapters 2 and 3 I make a first, very crude estimate of the amount of plastic entering the sea from land-based sources in South Africa and compare this to the 0.09-0.25 million tonnes predicted by Jambeck et al. (2015) based on national estimates of waste production and management. I conclude that actual plastic emissions are some 1-2 orders of magnitude less than the global model estimate, which concurs with estimates based on beach litter data.
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    Terrestrial-aquatic transfers by hippopotamus (Hippopotamus amphibius): effects on food web and benthic community structure of the St Lucia Estuary, iSimangaliso Wetland Park, World Heritage Site, South Africa
    (2019) Dawson, Jessica; Pillay, Deena
    Africa’s last extant aquatic megaherbivore, the hippopotamus, facilitates linkages between terrestrial and aquatic systems at scales, frequencies and intensities that are probably unmatched by any other natural process. Through defaecation of terrestrial grasses into aquatic habitats, hippos disproportionately enhance boundary permeability across the aquaticterrestrial divide. Little, however, is known about the ecological ramifications of these transfers for recipient communities and broader functioning in aquatic ecosystems, with equivalent knowledge for estuaries being virtually non-existent. Using a combination of in situ (1) experiments manipulating hippo dung inputs, (2) assessments of carbon and nitrogen stable isotope ratios and (3) fatty acid analyses, I aimed to quantify the influence of hippo dung on food web and benthic community structure in the St Lucia Estuary - a subtropical estuarine lake on the east coast of South Africa. It was hypothesized that experimental dung enrichment at high levels would result in significant declines in benthic community metrics and that food web components in biotopes with contrasting hippo numbers would differ in isotopic and fatty acid signatures. Results from experiments revealed that effects of hippo dung on benthic assemblages were assemblage specific. Microphytobenthic biomass was reduced by up to 70 %; macrobenthic abundance, biomass and richness declined by 76, 56 and 27 % respectively, while meiofauna were negligibly impacted by experimental dung enrichment. Results therefore suggest a greater resilience of meiofauna to high dung inputs relative to microphytobenthos and macrofauna. Comparisons of food web components from biotopes with contrasting hippo numbers (the Narrows: hippos dense; Charter’s Creek: hippos rare) indicated distinct consumer isotopic and fatty acid profiles, suggesting different dietary sources. Contrary to expectations, stable isotope mixing models revealed a greater reliance on hippo dung as a food source by consumers in Charter’s Creek (i.e. where hippos were rare). Fatty acid biomarkers suggested that in the presence of heavy dung loading, consumer diets incorporated VI less benthic diatoms, more bacteria, and generally reflected stronger dependence on terrestrial food sources. Overall, this study demonstrates the potential for hippo dung to influence consumers and trophic interactions due to its role as a trophic resource and modifier of abiotic conditions. However, findings of in situ experiments also show that in high amounts, dung inputs can lead to declines in benthic metrics. Apart from enhancing understanding of the broader roles hippos play in aquatic ecosystems, this study highlights considerations relevant to managing hippo populations and dung inputs, especially under drought conditions. This is central to maintenance of ecological functioning in a system that is regarded as a biodiversity hotspot and key tourist attraction. Specifically, it is important that water levels are managed to prevent dung accumulation and deleterious effects, particularly on the benthos.
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    The effect of supplementary nectar feeders on bird-plant mutualisms in the Cape Fynbos, South Africa
    (2021) Du Plessis, Monique; Coetzee, Anina; Seymour, Colleen; Spottiswoode, Claire
    Across the world, people feed birds to interact with nature. A variety of feeder types have been developed over the years to target a broad bird community. Attracting nectarivorous birds to gardens using supplementary nectar feeders is a popular human activity across the globe, but few studies have explored its effects on birds and the plants they pollinate. Nectar feeders may have positive effects, facilitating the urban adaptation of nectarivorous birds, and supplementing their diets when floral resources are scarce. However, supplementary feeders may also lure birds away from indigenous vegetation, affecting the rate of visits to bird-pollinated plants, with consequences for seed set. This study is the first to investigate the effect of nectar feeders on an African plantpollinator mutualism. Given that many plant species in the fynbos biome are bird pollinated, this study was conducted in residential gardens and natural vegetation along the urban edge of the Cape Peninsula, South Africa. I carried out a feeding experiment with a matched paired design to answer two main questions: (1) Do nectar feeders affect bird abundance and distribution ranges? If so, (2) do these affect their visitation rates to bird-pollinated plants? I conducted bird surveys to compare relative bird abundance and local distribution patterns for three feeding guilds (i.e., nectar-specialists, nectar-opportunists and non-nectarivores) between feeder and control treatments (Chapter 2). I then tested whether the presence of nectar feeders in gardens affected sunbird visitation rates to two bird-pollinated Erica species (Erica plukenetii subsp. plukenetii and Erica abietina subsp. atrorosea) in the neighbouring vegetation compared to control sites (Chapter 3). In chapter 2, I found that nectar feeders attracted higher densities of avian nectarivores (but not non-nectarivores) to gardens relative to natural vegetation, and decreased their densities in the neighbouring fynbos, even when floral abundance in the neighbouring vegetation was high. In chapter 3, I found that the consequent changes to sunbird distribution patterns (the main pollinators of ericas) seemed to have no influence on visitation rates to E. abietina, but decreased visitation to E. plukenetii flowers within 300 m of gardens with feeders. Thus, nectar feeders may have positive effects for birds themselves by reducing their urban sensitivity but may also have negative effects on the surrounding fynbos ecosystem. Given that nectar feeders appear to compete with the flowers of E. plukenetii, and perhaps those of other birdpollinated species, supplementary feeding may inadvertently threaten bird-plant pollination networks. This issue is particularly concerning in biomes such as the Cape Floristic Region where many bird-pollinated plants occur near urban edges.