Browsing by Author "Proches, Serban Mihai."

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Assessing the invasiveness of alien aroids using modelling techniques and ecological assessments.
(2016) Moodley, Desika.; Proches, Serban Mihai.; Wilson, John R.
Biological invasions represent one of the main drivers of the present decline in biodiversity worldwide and are difficult and costly to control. Consequently, identifying which factors allow a small proportion of species to successfully invade is a key area of research in invasion biology and is essential for effective management. In this thesis, I studied invasion patterns of the Araceae family, explored some of their ecological drivers, and unravelled mechanistic relationships that caused species to become successful. There are several emerging generalizations in invasion biology, but often the factors determining invasiveness are group-specific. Therefore the primary aim of this thesis was to establish whether general patterns of invasion biology also applied to Araceae. At a global scale, I found that, similar to other plant families, species with large native ranges and those that have been widely introduced were more likely to become invasive. What is unique to the family is the great diversity of growth forms, some of which are more likely to become invasive than others. I identified nine lineages in the family that have a greater tendency to invasiveness and recommended a precautionary approach be taken for these clades. At a regional scale, I used Epipremnum aureum as my case study species, because of the detection of the species in the country, as well as knowledge on its invasive cogener. In the KwaZulu-Natal province of South Africa, I found 78 naturalized E. aureum populations and 321 cultivated populations, of which the naturalized populations covered nearly 3 hectares in total. Disturbance played a major role in facilitating invasions and species distribution models indicated that E. aureum has a high probability of expanding its current range. Due to the invasion threat of this species, I recommended that all plants outside cultivation be removed. Lastly, I assessed a unique case where a widely planted species, Monstera deliciosa, has not yet become a global invader. I explored whether introduction history drives invasiveness in the Monsteroideae subfamily. I found that long residence times and high propagule pressure facilitated invasiveness in this subfamily. This was followed by as a local scale approach to identify factors influencing invasion success. The naturalization of Monstera deliciosa was largely driven by anthropogenic effects in Limpopo, South Africa, despite the plants‟ occurence in suitable habitat. Therefore, I concluded that M. deliciosa poses a low invasion risk to South Africa. Overall, this thesis demonstrated the importance of using a taxonomic group to identify the contribution of multiple factors in the success of invasive species, but that species-specific assessments will still be required for effective management.
The biogeography and ecology of the secondary marine arthropods of Southern Africa.
Proches, Serban Mihai.; Marshall, David J.
Abstract available in PDF file.
Challenges in resolving and protecting biodiversity in a developing city : the case of the Cato Ridge grasslands, Durban.
(2017) Styles, David Gordon Alexander.; Proches, Serban Mihai.
The area of Cato Ridge has been identified as a key node for future industrial and commercial development within the eThekwini Municipal Area, with a Local Area Plan approved to guide it. However, it also includes large areas of natural vegetation, including some of the best remaining instances of grassland in the city. These grasslands have been mapped as Ngongoni Veld but parts on Natal Group sandstone have contrarily been mapped as KwaZulu-Natal Sandstone Sourveld by the eThekwini Municipality’s Environmental Planning and Climate Protection Department. KwaZulu-Natal Sandstone Sourveld is considered endangered and deserving of greater conservation attention. However, little information is available about either of these grassland types. This thesis is based on surveying of 236 plots each of 100 m2 situated in better quality grassland throughout Cato Ridge, focusing on the herbaceous component. Plots were surveyed widely in order to determine and compare species richness and composition on different geological substrates (mainly Dwyka Group tillite and Natal Group sandstone), and different aspects and slopes, including respective occurrence of endemic and biogeographically important species and Cape floristic elements. Dwyka Group tillite plots were found to contain higher species richness. Both these plots and those on Natal Group sandstone were found to contain endemics, biogeographically important and Cape floristic element species. These results are used to interpret the question whether grassland on different geological substrates is to be referred to as Ngongoni Veld or KwaZulu- Natal Sandstone Sourveld. I conclude that, contrary to what has often been suggested in the past, under natural conditions Ngongoni Veld is neither a species-poor grassland type, nor does it lack distinctive species and deserves greater conservation attention. All occurrences of all grassland in better condition are mapped and compared with the land uses set out in the Local Area Plan. From this it is apparent that the plan enables their significant reduction and degradation, and requires amendment if this is not to occur.
Cities as hotspots for invasions: the case of the eThekwini Municipality.
(2019) Padayachee, Ashlyn Levadia.; Proches, Serban Mihai.
Increased anthropogenic activities (trade and travel) have caused an increase in the introduction of biological organisms outside of their native range. Biological invasions result in serious negative ecological, economic and social impacts in their invaded range and are responsible for a decline in native biodiversity. These negative impacts become more prominent in highly transformed environments, such as those found in cities which are often the first points of introduction for alien species. Durban (eThekwini) is situated on the east coast of South Africa and is one of the largest port cities on the African continent, making it an important economic centre for the country. It is the third most populated city in South Africa and is a major contributor towards tourism. Additionally, Durban is located in the Maputaland-Pondoland Albany, one of thirty-four global hotspots of biodiversity. This study focuses on the patterns, processes and drivers of biological invasions in Durban. I investigated three important aspects of alien species responses in urban environments: 1) precaution through the prevention of alien species introduction; 2) prioritisation through using a combination of early warning systems and techniques to identify potentially high-risk alien species; and 3) preparedness and response for a potential incursion event of Solenopsis invicta in Durban. I investigated the importance of preventing alien species introductions by identifying the pathways which facilitate the highest number of introductions for prioritisation for prevention efforts. Furthermore, I identified vectors responsible for secondary spread of alien species in cities. The majority of alien species were either released into nature or escaped from captivity and spread within cities through unaided dispersal. It is difficult to control the natural spread of species, therefore preventing alien species introductions is paramount. However, preventing the introduction of all alien species to a new area is difficult to achieve. Therefore, prioritising alien species for prevention efforts is an essential component of responding to biological invasions which will allow decision makers to more carefully allocate limited resources and time to species with the potential to result in severely negative impacts. Incorporating a holistic prioritisation approach based not only on alien species with a high-risk of invading new areas, but also the pathways which facilitate their introduction and the areas which are most at risk of being invaded is beneficial for decision makers in targeting priority species for prevention efforts. I developed a methodology, integrating these three aspects (species, pathways and sites), to select priority species to target for prevention efforts and identified areas most at risk of being invaded by these species using climatic suitability modelling to select priority targets for prevention efforts. Additionally, I used climatic models and pathway information to identify potential points of first introduction and sites of first naturalisation to target for active and passive surveillance endeavours. Solenopsis invicta Buren (the red imported fire ant) was identified as a potentially high-risk species posing serious ecological and socio-economic threats for Durban. I then explored opportunities for strategic response planning for Solenopsis invicta for Durban, South Africa. In doing so, I identified key priorities to help decision makers initiate strategic response planning for a potential incursion of this species to Durban. The research presented in this study outlines approaches that can assist with the prevention, prioritisation, and preparedness in responding to alien species in urban environments.
The ecology of ungulates in the Waterberg Plateau National Park, Namibia.
(2019) Kasiringua, Evert A.; Proches, Serban Mihai.; Kopij, Gregory.
Although ungulate species form an important component of Namibia’s economy through tourism, their population sizes vary substantially in relation to irregular rainfall, poaching, predation and competition, amongst other reasons. Understanding the ecology of ungulates is the key to adaptive ecosystem management and wildlife conservation in semi-arid savanna ecosystems. The study was conducted at Waterberg National Park, to determine habitat preferences, seasonal variation in population structure, daily drinking activities of twelve ungulate species and population dynamics of ungulates over a period of 33 years (1980-2013). The data used included road counts in all four vegetation types in the park (Terminalia sericea- Melhania acuminata vegetation, Terminalia sericea-Thesium megalocarpum, Terminalia sericea-Blepharis integrifolia, and the rock-inhabiting Peltophorum africanum community), waterhole counts, and pre-existing aerial counts. The probability of occurrence of large and medium ungulates was influenced by distance from the waterholes and from the roads. The population structure of seven herbivores varied in intricate ways between species and seasons. Smaller herds of ungulates were recorded most during the dry season as compared to larger herds observed during the wet season. Overall, the most frequent drinking times were between 15:00-22:00 with 18:00-19:00 being the conspicuous peak of the drinking activity, with 15% of animals in attendance. Four groups of ungulates were identified as per their drinking activity patterns: 1) day drinkers (warthog, giraffe, roan, and sable), 2) day/night drinkers (dik-dik, steenbok and common duiker), 3) evening/night drinkers (white rhino, black rhino and buffalo) and 4) night/morning drinkers (eland, gemsbok and kudu). The buffalo and eland population densities comprised together more than half of all ungulates recorded. Roan and sable antelope, kudu and warthog were also fairly common (with 5-12% of all ungulates recorded). White rhino, black rhino, giraffe, and gemsbok were classified as uncommon (together 11.9%), whilst the remaining seven species were rare (together 1.9%). Population size in eland showed a weak positive relationship with the annual average rainfall between the years 1981 - 2013, whereas population sizes in kudu, sable, gemsbok and roan showed a weak negative relationship with the amount of rain. No relationship was detected in giraffe, buffalo and hartebeest populations. The efficient management of wildlife resources that are economically and socially important necessitates regular surveys to monitor population trends in order to develop applicable management options. Thus, monitoring methods which are practical and efficient and provide accurate data are required for sound wildlife management. The results generated from this study provide novel contributions to strengthening management and conservation efforts of ungulates in Waterberg National Park and other wildlife parks in Namibia. More studies in the area of diet analysis of grazers and browsers as well as their preferences for particular plant species, with emphasis on inter- and intra- species competition is recommended.
The influence of the distance to running water or standing water bodies on rural household income.
Naidoo, Youkita.; Hoque, Muhammad Ehsanul.; Proches, Serban Mihai.
Rural areas in South Africa are characterised by a lack of formal authority and inadequate basic services such as water and sanitation. As a result, deficiencies here include, but are not limited to, poor access to health facilities, inferior infrastructure and unreliable water availability. The lack of sufficient water remains a prevalent issue in these rural areas, impairing appropriate environmental, hygiene, food and personal practices. Over large areas, the main sources of water continue to be rivers and fountains, which is used for the running of households. Water cuts through the centre of any development work within any community, and it is not unreasonable to assume that in communities where no piped water is available, living standards may be affected by the distance that household members have to cover to access water from natural sources. Yet stressing the provision of piped water has meant that research towards understanding the effects of distance to water sources has been lacking, while provision often continues to lag. A further factor to consider is the variation in income and the way human settlements are positioned in relation to water, relating to environmental and cultural factors, which vary across provinces. This study takes a quantitative approach to identify the data sources relevant to measuring the distance from water to households, as well as income in the relevant communities. It seeks patterns in the positioning of households in relation to water and focuses on establishing if there is, in fact, a relationship between the distance of households to water bodies and income in rural South Africa. The sample included nine villages across three provinces: Eastern Cape (Ntaboduli, Mdakeni, Matshona), KwaZulu-Natal (Vongunzana, Dinsi, Sangweyana Estate) and Limpopo (India, Sekwati, Ga-mohwibidu). The distance from 30 households in each of the nine communities to their nearest standing or running water was ascertained using Google Earthᵀᴹ. Thereafter, with the use of census data, the average household income of each village was plotted against the distance from water in metres. An inverse relationship matched the expectation that, as distance increases, income decreases, which can be linked to the amount of time spent collecting water. The relationship was not significant, but this is likely attributable to the small sample size and lack of income data at household scale. The researcher suggests that the more time is spent having to collect water, the less time is left available to earn a living. The research also identified some patterns in household distribution in relation to water by province and village, which are likely linked to practical, but also cultural, factors. This study recommends investing in proper water infrastructure for rural villages in South Africa.
An investigation of the bacterial profile recovered from the oral cavity of sharks, on the coast of KwaZulu-Natal, South Africa.
(2016) Khan, Nasreen.; Proches, Serban Mihai.; Bester, Linda Antionette.; Singh, Sanil Duleep.
Shark attacks are a rare occurrence globally; however quick treatment of a contaminated wound is imperative. Failure to treat infections in a timely manner may result in fatalities as marine bacteria have opportunistic qualities. In addition, limited knowledge is available on antibiotic resistance of bacteria associated with marine top-predators. A cross-sectional study was, therefore, performed to investigate the bacterial profile of a shark’s oral cavity. During 2012 to 2013, oral swabs were taken from sharks caught in protective gill-nets along the KwaZulu-Natal coastline in South Africa. Isolates were characterised by Gram-stain morphology and identified using biochemical tests and MALDI-ToF MS (Matrix assisted laser desorption/ionisation time-of-flight mass spectrometer). MICs (minimal inhibitory concentration) were performed using agar dilution against clinically important antibiotics. Data presented includes 205 isolates from 34 sharks. A total of ten species of sharks were caught. Ragged-tooth Carcharias taurus was the most frequently caught at 24% (8/34), the least frequent was smooth hammerhead Sphyrna lewini and copper Carcharhinus brachyurus at 3% (1/34). The highest prevalence of bacterial isolates were found in great white, Carcharodon carcharias (20%), scalloped hammerhead Spyrna lewini (16%) and mako Isurus oxyrhincus (14%) sharks. A Pearson correlation was used to calculate the similarities between sharks based on bacterial assemblages and shark-phylogeny. A trend was seen, however, no statistical significance was found. A plausible connection could be established with a higher sample number. In this study Micrococcus, Staphylococcus, Vibrio and Pseudomonas species rank among the four most frequently found bacteria in sharks. MICs revealed bacterial resistance of 50% to cefuroxime, 38% to ampicillin, 18% to nalidixic acid, 14% to tetracycline, 11% to erythromycin, 10% to ceftriaxone and lowest is 2% to ciprofloxacin. No resistance to gentamicin was found, highlighting its value in wound management. This primary data suggests the presence of clinically important bacteria in sharks transferable to humans, requiring specific treatments regimes.
Mapping the distributions of ancient plant and animal lineages in Southern Africa.
(2014) Padayachee, Ashlyn Levadia.; Proches, Serban Mihai.
Southern Africa boasts a wealth of endemic fauna and flora. The focus of this study was to identify ancient biological lineages (faunal and floral lineages of Eocene age or older) endemic to southern Africa, and map the distributions of these lineages across the region. Seventy-four operational geographic units (OGUs) were delimited for distribution mapping. Twenty-seven ancient lineages were identified (seventeen plants and ten animals). For each of these lineages, individual distribution maps were generated. Total endemism and corrected weighted endemism maps were also generated collectively for all lineages. Four stages of cluster analysis were used to illustrate clusters of OGUs with similar lineage composition, using UPGMA agglomerative hierarchical clustering. Characteristic lineages were determined for clusters at each stage, and similarities between these clusters and previously recognised biogeographic units were discussed. A comparison between ancient endemic lineages and their sister lineages was conducted. Sister lineages were found to be often widespread and differed from ancient lineages in the types of habitat occupied and, in some cases, niche differences were noted. The mechanisms of ancient lineage survival in the region were investigated, and their importance for conservation in southern Africa emphasised.
The origin and dynamics of Wakkerstroom Vlei, Mpumalanga Province, South Africa.
(2009) Joubert, Rebecca.; Proches, Serban Mihai.; Ellery, William Nolan.
The formation and common occurrence of riparian wetlands within the semi-arid Highveld interior of South Africa, a landscape setting undergoing extensive long-term fluvial incision, is an enigma and the underlying controls on the formation and hydrogeomorphological dynamics of these wetlands has not been widely investigated. Wakkerstroom Vlei is one such enigma in that it is a large (~ 1000 ha) Highveld system comprising extensive reaches of unchanneled valley-bottom wetland with considerable (up to 2 m deep) peat deposits. Accommodation space for wetland formation is thought to be controlled by the superimposition of the main (Wakkerstroom/Thaka) river upon an erosion-resistant Karoo dolerite sill at the toe of the system, which forms a stable local base-level along the rivers course. As a result, the river has carved broad (up to 1300 m), gently sloping (average slope ~ 0.17 %) valleys along softer shale valley reaches upstream of the dolerite barrier. Examination of the valley fill along these valley-bottom wetland reaches, together with analysis of historic aerial photography, reveals that continuous tracts of meandering river and floodplain wetlands formerly existed, and that the wetland experienced an abrupt shift to valley-bottom wetland conditions where surface flow of water is diffusive. Following the creation of accommodation space along the main river valley, lateral tributary streams began to deposit substantial amounts of course sediment into the main valley via alluvial fans. Several of these fans have coalesced to form multiple coalescing alluvial fan complexes that historically were able to extend far across the floodplain from either side of the valley, resulting in main river valley impoundment. This has promoted flood-out formation, along the main valley which, together with the denser growth of vegetation across the floodplain, has created conditions suitable for organic sedimentation and peat accumulation. The formation and evolution of Wakkerstroom Vlei has thus been controlled by the complex interaction between geological, geomorphological and biotic processes. Understanding the role of these factors in shaping both the short- and long-term hydro-geomorphic dynamics of the system is essential in implementing effective management and conservation strategies both within Wakkerstroom Vlei and other large valley-bottom wetlands within the South African Highveld interior.
Patterns of animal endemism in the Maputaland-Pondoland-Albany biodiversity hotspot.
(2013) Perera, Merennage Sandun Jayalal.; Proches, Serban Mihai.
The Maputaland-Pondoland-Albany (MPA) hotspot, as is the case of all such global biodiversity hotspots, has primarily been recognised based on its high floristic endemism and delimited intuitively. Boundaries of global biodiversity hotspots have seldom been empirically tested in terms of species distribution patterns and only a few have been examined for patterns of animal endemism. This thesis presents the results of a zoogeographical study of all five major vertebrate groups and selected invertebrate groups in south-eastern Africa, refining the delimitation of the MPA hotspot and identifying areas and centres of endemism within and around it. It also provides zoogeographical regionalisation schemata for the whole of south-eastern Africa. The study employed methods of, (a) preliminary qualitative identification of “Endemic Vertebrate Distributions”, (b) phenetic clustering of operational geographical units based on species incidence matrices, using the Jaccard’s coefficient of similarity and the Unweighted Pair-Group Method using Arithmetic means (UPGMA) clustering algorithm, (c) Parsimony Analysis of Endemicity, and (d) ArcGIS-based mapping of various measures of endemism (e.g. narrow endemism and weighted endemism). The results reveal that the MPA hotspot, though defined so due to its exceptional floristic endemism, is a hotspot for the endemism of animals too, especially for the herpetofauna and invertebrate groups like the velvet worms, land snails and many others. But the current boundary of the hotspot is arbitrarily defined and not exactly matching the patterns of animal endemism (and, likely, neither those in plants). Hence, a greater Maputaland-Pondoland-Albany (GMPA) region of animal endemism is proposed as a broad priority region of conservation concern, while centres of endemism within the GMPA are identified and patterns of quantitative measures of endemism are mapped. The study also proposes a zoogeographical regionalisation placing the GMPA and Highveld regions at the province rank in the global zoogeographical hierarchy, within the south east African dominion, also describing zoogeographical districts and assemblages nested within each. Results from the vertebrate and invertebrate analyses reveals the possibility of a common zoogeographical regionalisation for south-eastern Africa. The study emphasises the importance of quantitative biogeographical methodologies in conservation biogeography, in addition to their uses in the theoretical/descriptive biogeography.
Regional representativeness hotspots for world's tetrapod vertebrate genera.
(2021) Govender, Chanelle Ornella.; Proches, Serban Mihai.
As anthropogenic stress and resulting habitat degradation put pressure on biodiversity, there is a need for urgent and innovative conservation strategies. The integration of the biogeographical concept of bioregionalisation into conservation planning is critical for the successful protection of biodiversity on a global scale. This study looked at zoogeographic regions taken one by one, and combined based on their evolutionary histories, climate, and overall spatial interactions. Representative genera were selected, and their richness calculated for these single and combined regions. Representative genera for a region include genera which exhibit high levels of endemism and regional filling of that region. Regional representativeness hotspots were combined to produce a global hotspot scheme. Combinations of regions such as the Neo-Caribbean, Holarctic and Neotropic-Nearctic included significant numbers of ecoregions with hotspot status. Combinations including the Australian Zoogeographic Region and gradually larger numbers of neighbouring regions resulted in varying spatial hotspot patterns relevant to global regionalisation attempts. Theories and hypotheses, including continental drift, vicariance and dispersal events, and the influence of paleoclimates all contribute important explanations towards shaping the distribution of genera and the delineation of zoogeographic regions. Regional representativeness hotspots can be biogeographical units for robust conservation strategies, representing a proactive approach to the conservation of representative genera and co-occurring taxa worldwide.
The relationship between the length of flowering periods and the distribution ranges of plant species in eastern South Africa.
(2012) Mahadeo, Nikara.; Ramdhani, Syd.; Proches, Serban Mihai.
Flowering is one of the most important stages in determining the successful survival and spread in plants. The duration of the flowering period is closely associated with successful reproduction, making it essential to understand the importance and effects of the length of flowering on various macroecological variables across plant species. The effects of the length of flowering periods on the distribution range size of species have seldom been investigated. This project aims to identify any macroecological relationship that may exist between the length of flowering periods and the distribution ranges of plant species endemic to the eastern part of South Africa, a region well known for its floral diversity. Range size and flowering phenology data were collected for several genera that are centred in the region (Cussonia, Gymnosporia, Searsia, Streptocarpus, Pavetta, Plectranthus, Crinum, Eulophia, Gladiolus, Kniphofia, Satyrium, Watsonia and Zantedeschia). At genus level, the relationship varied considerably. While significant correlations between the two variables were retrieved in four genera, the meaning of these patterns differed. In some cases, these suggested that a larger range was achieved through successful pollination due to extended flowering periods, whereas in others, it is probably just an effect of different flowering seasons in different areas where the range is large enough to comprise diverse climates. When incorporating variables such as growth form (narrowly and broadly-defined) and genus identity in analyses of covariance between flowering durations and various measures of distribution, the association of genera was far greater than that of growth form. It can be concluded that both range size and the length of the flowering season are the result of numerous factors acting jointly, which differ across plant groups and are likely to be susceptible to changes in climate and biological invasions. This means that the relationship between range size and flowering period is driven by different factors in different genera, suggesting that the conservation of plant diversity in the face of global change will have to consider the complexity of flowering patterns, and it is likely that lineage-specific approaches for different plant groups will be necessary.
A study of air quality issues at the Bulbul Drive Landfill, South Africa.
(2015) Perumal, Sarisha.; Proches, Serban Mihai.
A landfill impacts on the environment through various pathways. However, it is through the air that those living near the site experience most of these impacts. The Bulbul Drive Landfill is a hazardous waste disposal facility near Chatsworth and Umlazi in the eThekwini Municipality. The aim of this study is to assess ambient air quality issues in the region neighbouring the Bulbul Drive Landfill. Ambient air quality parameters were measured using passive sampling. H₂S concentrations were found to be below threshold levels and it is likely that odour issues are attributed to other components of landfill gas. These include benzene, 1, 2, 4-trimethyl1-ethyl-2-methyl; decane; heptane and tetrachloroethylene benzene, toluene, ethylbenzene, xylene, dichloroethylene, dichloromethane, trichloroethylene, tetrachloroethylene and vinyl chloride (Berger & Mann, 2001). The concentrations of gaseous pollutants did not exceed the relevant ambient air quality standards but cumulative effects and the applicability of averaging times need to be considered further. There was an incidence of non-compliance with the South African National Dust Control Regulation implying that fallout dust in the Bulbul Drive Landfill area has a negative impact on ambient air quality. An elemental analysis of dust samples revealed that there is a potential for heavy metal contamination on a larger scale. The results of the household survey showed that there were diverse and complex perceptions of air pollution amongst the residents of Chatsworth and Umlazi. Most respondents experienced dust, odour and poor visibility but the nature of this experience varied from Chatsworth to Umlazi. The presence of the Bulbul Drive landfill was acknowledged as a negative aspect of both neighbourhoods, respondents were happy that the landfill was closing. However, emission of pollutants from a landfill, be they solid or gaseous in nature, can be produced for 30 – 300 years after a landfill has closed. The communities of Chatsworth and Umlazi will continue to bear the burden of air quality risks associated with the Bulbul Drive landfill. Despite a shift in environmental governance in South Africa and attempts to address the uneven distribution of environmental risk, air quality management remains a challenge. An interdisciplinary approach is required to address the inequitable distribution of risks associated with air pollution. Policy makers and practitioners alike need to augment technical measurements with an understanding of the social dimension of air pollution.