Constraints and enablements on quality improvement in higher education
- Authors: Browning, Leanne Elizabeth
- Date: 2021-10-29
- Subjects: Education, Higher Aims and objectives South Africa , Education, Higher Evaluation , Quality assurance South Africa , Educational evaluation South Africa , Self-evaluation , Critical realism
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/294956 , vital:57273 , DOI 10.21504/10962/294956
- Description: This study contributes to the literature on quality improvement in higher education by examining the structural, cultural and agential constraints and enablements on a quality process at a university in South Africa. It examined four cases and developed an understanding of the complex interaction of structure, culture and agency and the mechanisms that enable or constrain quality improvement in higher education. The study drew on the literature on higher education quality for the theoretical basis for what is known contributes to the way in which quality assurance and improvement is implemented and its impact on the higher education context. Critical Realism provided the ontological framework and conceptual tools to understand and explore the complex social world within which the quality process took place. The literature on the morphogenetic approach provided the analytical framework for the data analysis and findings. The data consisted of a set of documents from a quality process that took place over a five-year period. The data analysis revealed that different departmental contexts impact on how mechanisms are activated. Each school context shapes the way in which people engage with the review process and consequently, processes and procedures are mediated in each context. This research therefore adds to the understanding of the way in which quality processes take place at a micro-level within an institutional context and informs the approach to quality improvement more broadly, nationally and internationally. The research contributes to the knowledge that will inform planning, policies and practices in quality improvement processes in higher education and the findings identify a number of factors (mechanisms) that should inform the way in which a quality process is facilitated, will enable effective self-evaluation and review processes, and consequently are more likely to lead to quality improvement. , Thesis (PhD) -- Faculty of Education, Centre for Higher Education Research, Teaching and Learning, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Browning, Leanne Elizabeth
- Date: 2021-10-29
- Subjects: Education, Higher Aims and objectives South Africa , Education, Higher Evaluation , Quality assurance South Africa , Educational evaluation South Africa , Self-evaluation , Critical realism
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/294956 , vital:57273 , DOI 10.21504/10962/294956
- Description: This study contributes to the literature on quality improvement in higher education by examining the structural, cultural and agential constraints and enablements on a quality process at a university in South Africa. It examined four cases and developed an understanding of the complex interaction of structure, culture and agency and the mechanisms that enable or constrain quality improvement in higher education. The study drew on the literature on higher education quality for the theoretical basis for what is known contributes to the way in which quality assurance and improvement is implemented and its impact on the higher education context. Critical Realism provided the ontological framework and conceptual tools to understand and explore the complex social world within which the quality process took place. The literature on the morphogenetic approach provided the analytical framework for the data analysis and findings. The data consisted of a set of documents from a quality process that took place over a five-year period. The data analysis revealed that different departmental contexts impact on how mechanisms are activated. Each school context shapes the way in which people engage with the review process and consequently, processes and procedures are mediated in each context. This research therefore adds to the understanding of the way in which quality processes take place at a micro-level within an institutional context and informs the approach to quality improvement more broadly, nationally and internationally. The research contributes to the knowledge that will inform planning, policies and practices in quality improvement processes in higher education and the findings identify a number of factors (mechanisms) that should inform the way in which a quality process is facilitated, will enable effective self-evaluation and review processes, and consequently are more likely to lead to quality improvement. , Thesis (PhD) -- Faculty of Education, Centre for Higher Education Research, Teaching and Learning, 2021
- Full Text:
- Date Issued: 2021-10-29
Culture, gender and forests: social differentiation in coping and adapting to climate change and other stressors in the south west and east regions of Cameroon
- Authors: Enokwena Baa, Ojongetakah
- Date: 2021-10-29
- Subjects: Climatic changes Cameroon , Differentiation (Sociology) Cameroon , Climatic changes Social aspects Cameroon , Cultural awareness Cameroon , Environmental justice Cameroon , Social justice Cameroon , Environmental risk assessment Cameroon , Political ecology Cameroon , Ecofeminism Cameroon , Social capital (Sociology) Cameroon , Community forests Cameroon , Deforestation Cameroon
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/295040 , vital:57284 , DOI 10.21504/10962/295040
- Description: Climate change adaptation scholars and practitioners are beginning to acknowledge that the impact of climate change and other related shocks and stressors will be felt, and reacted to, differently across genders and other types of intersecting social categories, such as age, wealth, and culture, in rural communities. However, to date, most research unpacking these differential impacts and responses has been limited to 'men' versus 'women'. Few studies go beyond this male-female dichotomy to include the different gender structures of households and the intersection with other social factors that contribute to marginalisation, such as ethnicity. This research aimed to explore how different gendered household types in two ethnically diverse communities, the Ejagham and the Baka communities in the SSouth West and East regions of Cameroon, experienced and responded to climate change and other stressors. The central argument of the study is that social differentiation present dynamics and complexities across intersecting identities which determines varied levels of vulnerabilities, adaptive capacity, and livelihood outcomes. The study thus sets out to examine cultural and gendered differentiation in household assets and livelihood activities, how multiple shocks and stressors are experienced, and the differentiated responses to these, focussing specifically on forest and social safety nets. The findings were used to develop an integrated understanding of the complex socially differentiated dimensions of vulnerability and adaptation within the two communities and the implications for more climate secure and equitable livelihoods. The study drew on social-ecological systems, social justice, and feminist political ecology as guiding theoretical lenses. The study further integrated the Moser gender planning and Harvard analytical frameworks as tools for unpacking gender inequality. It followed a mixed methods research design that included household surveys, key informant interviews, and focus group discussions that applied participatory exercises. Financial, human, and physical capital were arguably limited within all household types in both the Ejagham and the Baka communities. Social and natural capital were the most common form of assets that households relied on, with ‘savings groups’ in the Ejagham communities being particularly prevalent. Most households were involved in crop cultivation and forest product collection although there were gendered and cultural differences. Collection of wild fruits, medicinal plants, and condiments, for example, was a more common livelihood activity within the Baka communities and amongst female-headed households. Cultivation of pumpkins and vegetables was dominant amongst households in Ejagham, with these being grown mainly by women, while the cultivation of yams was done by men. Across both communities, female-headed households had less ownership of land compared to male-headed households. The current pressure on agricultural land in the Ejagham communities has decreased crop productivity, with female-headed households disproportionately affected by less ownership of land and thus, options to diversify agricultural activities. Similarly, the rise in individual and private land ownership, in response to resource scarcity and large-scale deforestation in East Cameroon, has further dispossessed female-headed households in the Baka communities, already marginalised by their ethnicity, of land. Inequitable access to assets and the disparity in ownership of these assets across the study communities was both a cause and effect of households' differential livelihood activities and responses to shocks and stressors. Several of the shocks and stressors households were exposed to differed across the two sites. The Ejagham communities, being predominantly agricultural, frequently identified warming temperatures as a climatic stressor and increased sensitivity to the impacts of these. The Baka faced similar climate stressors, although more frequent storms were mentioned as a shock by a significant number of households. The impacts of these storms include damage and destruction of houses due to the traditional construction methods used. Since women are often tasked with the building of houses this adds another layer of stress for them. In terms of idiosyncratic shocks, the death of the main breadwinner was most frequently reported in both communities as a non-climatic shock, although this was higher within the Ejagham communities than in the Baka communities, and particularly so for female-headed households. The varied experiences from multiple shocks and stressors resulted in households' differential coping and adaptation responses. Among the different response options, social and forest safety nets, especially the use and sale of forest products (NTFPs) remained the main response options used by households in both communities. Forest products further supported households during periods of food shortage, especially female-headed households in the Ejagham communities. Households further supported one another through social groups such as savings, farming, hunting (particularly for men) and NTFP collection (for women) groups. By exploring social-ecological interactions, the study highlights the complexities around gender inequalities, vulnerabilities, and responses across socially differentiated groups of people which should be considered in policy, practice, and research. Several of my findings challenge mainstream discourses that generally group women, for instance, as a homogenous category when looking at vulnerability. For example, findings revealed that it is possible for different types of households, both women and men, to be both advantaged and vulnerable at the same time, depending on the shock or stressor faced and the livelihood activities they engage in. The same also applies to ethnicity. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Enokwena Baa, Ojongetakah
- Date: 2021-10-29
- Subjects: Climatic changes Cameroon , Differentiation (Sociology) Cameroon , Climatic changes Social aspects Cameroon , Cultural awareness Cameroon , Environmental justice Cameroon , Social justice Cameroon , Environmental risk assessment Cameroon , Political ecology Cameroon , Ecofeminism Cameroon , Social capital (Sociology) Cameroon , Community forests Cameroon , Deforestation Cameroon
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/295040 , vital:57284 , DOI 10.21504/10962/295040
- Description: Climate change adaptation scholars and practitioners are beginning to acknowledge that the impact of climate change and other related shocks and stressors will be felt, and reacted to, differently across genders and other types of intersecting social categories, such as age, wealth, and culture, in rural communities. However, to date, most research unpacking these differential impacts and responses has been limited to 'men' versus 'women'. Few studies go beyond this male-female dichotomy to include the different gender structures of households and the intersection with other social factors that contribute to marginalisation, such as ethnicity. This research aimed to explore how different gendered household types in two ethnically diverse communities, the Ejagham and the Baka communities in the SSouth West and East regions of Cameroon, experienced and responded to climate change and other stressors. The central argument of the study is that social differentiation present dynamics and complexities across intersecting identities which determines varied levels of vulnerabilities, adaptive capacity, and livelihood outcomes. The study thus sets out to examine cultural and gendered differentiation in household assets and livelihood activities, how multiple shocks and stressors are experienced, and the differentiated responses to these, focussing specifically on forest and social safety nets. The findings were used to develop an integrated understanding of the complex socially differentiated dimensions of vulnerability and adaptation within the two communities and the implications for more climate secure and equitable livelihoods. The study drew on social-ecological systems, social justice, and feminist political ecology as guiding theoretical lenses. The study further integrated the Moser gender planning and Harvard analytical frameworks as tools for unpacking gender inequality. It followed a mixed methods research design that included household surveys, key informant interviews, and focus group discussions that applied participatory exercises. Financial, human, and physical capital were arguably limited within all household types in both the Ejagham and the Baka communities. Social and natural capital were the most common form of assets that households relied on, with ‘savings groups’ in the Ejagham communities being particularly prevalent. Most households were involved in crop cultivation and forest product collection although there were gendered and cultural differences. Collection of wild fruits, medicinal plants, and condiments, for example, was a more common livelihood activity within the Baka communities and amongst female-headed households. Cultivation of pumpkins and vegetables was dominant amongst households in Ejagham, with these being grown mainly by women, while the cultivation of yams was done by men. Across both communities, female-headed households had less ownership of land compared to male-headed households. The current pressure on agricultural land in the Ejagham communities has decreased crop productivity, with female-headed households disproportionately affected by less ownership of land and thus, options to diversify agricultural activities. Similarly, the rise in individual and private land ownership, in response to resource scarcity and large-scale deforestation in East Cameroon, has further dispossessed female-headed households in the Baka communities, already marginalised by their ethnicity, of land. Inequitable access to assets and the disparity in ownership of these assets across the study communities was both a cause and effect of households' differential livelihood activities and responses to shocks and stressors. Several of the shocks and stressors households were exposed to differed across the two sites. The Ejagham communities, being predominantly agricultural, frequently identified warming temperatures as a climatic stressor and increased sensitivity to the impacts of these. The Baka faced similar climate stressors, although more frequent storms were mentioned as a shock by a significant number of households. The impacts of these storms include damage and destruction of houses due to the traditional construction methods used. Since women are often tasked with the building of houses this adds another layer of stress for them. In terms of idiosyncratic shocks, the death of the main breadwinner was most frequently reported in both communities as a non-climatic shock, although this was higher within the Ejagham communities than in the Baka communities, and particularly so for female-headed households. The varied experiences from multiple shocks and stressors resulted in households' differential coping and adaptation responses. Among the different response options, social and forest safety nets, especially the use and sale of forest products (NTFPs) remained the main response options used by households in both communities. Forest products further supported households during periods of food shortage, especially female-headed households in the Ejagham communities. Households further supported one another through social groups such as savings, farming, hunting (particularly for men) and NTFP collection (for women) groups. By exploring social-ecological interactions, the study highlights the complexities around gender inequalities, vulnerabilities, and responses across socially differentiated groups of people which should be considered in policy, practice, and research. Several of my findings challenge mainstream discourses that generally group women, for instance, as a homogenous category when looking at vulnerability. For example, findings revealed that it is possible for different types of households, both women and men, to be both advantaged and vulnerable at the same time, depending on the shock or stressor faced and the livelihood activities they engage in. The same also applies to ethnicity. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Integrative systematic structuring of the widespread psammophiid snakes (Psammophiidae): a multi-evidence species delineation approach
- Authors: Keates, Chad
- Date: 2021-10-29
- Subjects: Psammophis South Africa , Herpetology , Herpetology Africa , Molecular biology , Psammophis Classification , Psammophis Genetics , Psammophis Morphology , Psammophis Phylogeny , Morphology Mathematics , Psammophylax
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/295077 , vital:57288 , DOI 10.21504/10962/295079
- Description: Species form the foundations upon which we build our understanding of the natural world. Although a focus of much scientific attention, our understanding of species is stunted by the intrinsic ‘fuzziness’ of boundaries within nature. Due to the complexity of the evolutionary process, coupled with an ever-changing abiotic landscape, species are hard to delineate, even at the best of times. Whilst various species concepts and sophisticated delimitation methods have helped scientists tease apart species, many species complexes persist. This is because taxonomy is a discrete ordering system imposed upon the continuous and intercalated structure of life. To improve our understanding of a wide-ranging family of snakes, I investigated the taxonomy and evolutionary structuring within Psammophiidae using both molecular and morphological approaches, employing phylogenetic, phylogeographic, and morphometric analyses on the group. The systematic complexity of the family (as evidenced by past research) coupled with the group’s widespread distribution and ecological importance, made the taxon an ideal candidate for a broad-sweeping multi-level systematic analysis using multiple species delimitation methods. Additionally, in this thesis I attempted to build on the ground-breaking work of Christopher Kelly by addressing several knowledge gaps identified within the family, and in so doing, produce the most thorough evolutionary and taxonomic study of Psammophiidae possible. Given the taxonomic uncertainty associated with the family, Chapter Two used a representative sampling from every available species (near complete taxon sampling approach) in the family. The chapter used both standard and time-calibrated phylogenetic modelling and distance/threshold-based species delimitation, to elucidate the finer-level structuring within the family. Geometric morphometrics was used to determine whether there were diagnosable differences in head structure between the different genera. The final phylogenetic tree incorporated 320 samples, representing the most comprehensive phylogenetic reconstruction of the family to date. By using a near-complete taxon sampling approach, I was able to resolve previously unsupported relationships within the family whilst also identifying several novel instances of an under- and over-appreciation of species diversity within the family. Geometric morphometrics also identified clear distinctions between genera based on head shape (head width and ‘beakedness’). This chapter showcased the importance of complete taxon sampling and robust methodology for species delimitation and the deleterious effect of species concepts when implemented in isolation. In Chapter Three, I narrowed the scope of the study to focus on the genus level. Psammophylax (Fitzinger 1843) is an abundant, yet poorly studied genus of grass snakes, endemic to Africa. The generalist nature of the genus and wide-spanning distributions of the constituent species has given rise to several subspecies and a poor understanding of the taxonomic structuring within the genus. The overlapping distributions (sympatry) of many of Psammophylax species, coupled with the potential for cryptic speciation via mechanisms such as convergent evolution, made the group the ideal candidate for a broad-sweeping systematic study (as evidenced in Chapter Two). By applying the suite of analyses used in Chapter Two to the generic level, we aimed to determine the effectiveness of a multi-evidence species delineation approach when tackling systematic problems at lower taxonomic levels. A genetic phylogeny of six of the seven species was estimated using multiple phylogenetic and distance/ threshold-based species delimitation methods. To support the molecular analyses, we conducted morphological analyses on the body (traditional morphology) and head (geometric morphometrics) separately. Phylogenetic analyses recovered a similar topology to past studies, but with better resolution and node support. I found substantial genetic structuring within the genus, supported by significantly different head shapes between Ps. a. acutus and other Psammophylax species. Psammophylax a. acutus was recovered as sister to its congeners, and sequence divergence values and morphometrics supported its recognition as a new genus. Increased sampling in East Africa (Tanzania, Kenya, and Ethiopia) revealed that Psammophylax multisquamis is polyphyletic, necessitating the description of a new, morphologically cryptic, species from northern Tanzania. The distribution of Ps. multisquamis sensu stricto is likely restricted to Kenya and Ethiopia. Within this chapter, taxon-specific phylogenetic analyses yielded stronger intrageneric support as compared to Chapter Two, allowing for more defensible conclusions about taxonomical amendments. Geometric morphometrics proved similarly useful (as compared to Chapter Two) in teasing apart genera within the family but lacked the robustness to delineate species within Psammophylax with confidence, highlighting the apparent convergence of form within the genus. In Chapter Four, I investigated the evolutionary structuring within the Southern African endemic Psammophylax rhombeatus. The structural and environmental heterogeneity within the region has given rise to many morphological forms distributed throughout the country, with previous studies neglecting the associated molecular significance of these forms. Irrespective of their small sample sizes, both Chapter Two and Three identified substantial phylogenetic structuring within the species, making Ps. rhombeatus the ideal candidate for a multi-faceted systematic review, using a combination of phylogenetics, geometric morphometrics and, for the first time in this species, phylogeographic analyses. By investigating a single species, in detail, I was able to assess the effectiveness of the methodologies implemented in previous chapters on systematic sorting using the multi-evidence species delineation approach. Phylogenetic and haplotype analysis retrieved four well-supported clades: southeast South Africa (SESA), southwest South Africa (SWSA), north-eastern South Africa (NESA) and western South Africa (WSA). Although not variable enough to warrant taxonomic re-evaluation, the clades represented important genetic hotspots, with relatively high intraspecific genetic divergence values separating them, irrespective of the small geographic distances separating populations. This is likely a product of the taxon’s habitat-generalist lifestyle, enabling them to bypass vicariant barriers that might otherwise cause speciation in less versatile species. The clades are also geographically distinct, with little overlap, indicating previous vicariance, a finding that is supported by the split of Ps. rhombeatus from Ps. ocellatus in the mid-Pliocene, followed by the diversification of Ps. rhombeatus into four clades throughout the Pleistocene. The genetic structuring observed in Ps. rhombeatus may be a product of population expansion following ancient refugial isolation (potentially Last Glacial Maximum [LGM]). The molecular distinctiveness of the clades was not replicated in the morphological component of this chapter, with neither dorsal nor lateral geometric morphometric analyses of head shape showing any discernible distinctiveness based on geography. Whilst head shape has not been shown to be an effective delineator of evolutionary units at the species level (within this taxon), body colour, scalation, and snout-vent length has been linked to morphotypes within the species based on the work of Broadley (1966). These morphological groupings are loosely attributable to the molecular clades identified in the phylogenetic analyses, highlighting the complex interplay of genetic and morphological characteristics in the process of speciation, and their representation in systematic accounts. This thesis represents the most thorough evolutionary and systematic study of the family currently possible. In addition to identifying and describing both a new genus and species, this thesis also highlighted several instances of an over- and under-appreciation of species diversity within Psammophiidae. By applying a multi-evidence species delineation approach to this thesis, I show the intricacy of the evolutionary process (at various taxonomic levels) and showcase the ease to which species boundaries can be confounded when species concepts are implemented in isolation. These findings also highlighted the importance of sample size, sample range, species delimitation method on the outcome of taxonomic analyses, and their interpretation. Lastly, this thesis addressed the knowledge gaps left by Christopher Kelly’s PhD work and investigated the findings of recent papers that attempted to do the same. Whilst this study answers the questions of old, the taxon-intensive focus revealed several new knowledge gaps within the family, highlighting how much we know about snake systematics, and furthermore, how much we still need to learn about evolutionary structuring. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Keates, Chad
- Date: 2021-10-29
- Subjects: Psammophis South Africa , Herpetology , Herpetology Africa , Molecular biology , Psammophis Classification , Psammophis Genetics , Psammophis Morphology , Psammophis Phylogeny , Morphology Mathematics , Psammophylax
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/295077 , vital:57288 , DOI 10.21504/10962/295079
- Description: Species form the foundations upon which we build our understanding of the natural world. Although a focus of much scientific attention, our understanding of species is stunted by the intrinsic ‘fuzziness’ of boundaries within nature. Due to the complexity of the evolutionary process, coupled with an ever-changing abiotic landscape, species are hard to delineate, even at the best of times. Whilst various species concepts and sophisticated delimitation methods have helped scientists tease apart species, many species complexes persist. This is because taxonomy is a discrete ordering system imposed upon the continuous and intercalated structure of life. To improve our understanding of a wide-ranging family of snakes, I investigated the taxonomy and evolutionary structuring within Psammophiidae using both molecular and morphological approaches, employing phylogenetic, phylogeographic, and morphometric analyses on the group. The systematic complexity of the family (as evidenced by past research) coupled with the group’s widespread distribution and ecological importance, made the taxon an ideal candidate for a broad-sweeping multi-level systematic analysis using multiple species delimitation methods. Additionally, in this thesis I attempted to build on the ground-breaking work of Christopher Kelly by addressing several knowledge gaps identified within the family, and in so doing, produce the most thorough evolutionary and taxonomic study of Psammophiidae possible. Given the taxonomic uncertainty associated with the family, Chapter Two used a representative sampling from every available species (near complete taxon sampling approach) in the family. The chapter used both standard and time-calibrated phylogenetic modelling and distance/threshold-based species delimitation, to elucidate the finer-level structuring within the family. Geometric morphometrics was used to determine whether there were diagnosable differences in head structure between the different genera. The final phylogenetic tree incorporated 320 samples, representing the most comprehensive phylogenetic reconstruction of the family to date. By using a near-complete taxon sampling approach, I was able to resolve previously unsupported relationships within the family whilst also identifying several novel instances of an under- and over-appreciation of species diversity within the family. Geometric morphometrics also identified clear distinctions between genera based on head shape (head width and ‘beakedness’). This chapter showcased the importance of complete taxon sampling and robust methodology for species delimitation and the deleterious effect of species concepts when implemented in isolation. In Chapter Three, I narrowed the scope of the study to focus on the genus level. Psammophylax (Fitzinger 1843) is an abundant, yet poorly studied genus of grass snakes, endemic to Africa. The generalist nature of the genus and wide-spanning distributions of the constituent species has given rise to several subspecies and a poor understanding of the taxonomic structuring within the genus. The overlapping distributions (sympatry) of many of Psammophylax species, coupled with the potential for cryptic speciation via mechanisms such as convergent evolution, made the group the ideal candidate for a broad-sweeping systematic study (as evidenced in Chapter Two). By applying the suite of analyses used in Chapter Two to the generic level, we aimed to determine the effectiveness of a multi-evidence species delineation approach when tackling systematic problems at lower taxonomic levels. A genetic phylogeny of six of the seven species was estimated using multiple phylogenetic and distance/ threshold-based species delimitation methods. To support the molecular analyses, we conducted morphological analyses on the body (traditional morphology) and head (geometric morphometrics) separately. Phylogenetic analyses recovered a similar topology to past studies, but with better resolution and node support. I found substantial genetic structuring within the genus, supported by significantly different head shapes between Ps. a. acutus and other Psammophylax species. Psammophylax a. acutus was recovered as sister to its congeners, and sequence divergence values and morphometrics supported its recognition as a new genus. Increased sampling in East Africa (Tanzania, Kenya, and Ethiopia) revealed that Psammophylax multisquamis is polyphyletic, necessitating the description of a new, morphologically cryptic, species from northern Tanzania. The distribution of Ps. multisquamis sensu stricto is likely restricted to Kenya and Ethiopia. Within this chapter, taxon-specific phylogenetic analyses yielded stronger intrageneric support as compared to Chapter Two, allowing for more defensible conclusions about taxonomical amendments. Geometric morphometrics proved similarly useful (as compared to Chapter Two) in teasing apart genera within the family but lacked the robustness to delineate species within Psammophylax with confidence, highlighting the apparent convergence of form within the genus. In Chapter Four, I investigated the evolutionary structuring within the Southern African endemic Psammophylax rhombeatus. The structural and environmental heterogeneity within the region has given rise to many morphological forms distributed throughout the country, with previous studies neglecting the associated molecular significance of these forms. Irrespective of their small sample sizes, both Chapter Two and Three identified substantial phylogenetic structuring within the species, making Ps. rhombeatus the ideal candidate for a multi-faceted systematic review, using a combination of phylogenetics, geometric morphometrics and, for the first time in this species, phylogeographic analyses. By investigating a single species, in detail, I was able to assess the effectiveness of the methodologies implemented in previous chapters on systematic sorting using the multi-evidence species delineation approach. Phylogenetic and haplotype analysis retrieved four well-supported clades: southeast South Africa (SESA), southwest South Africa (SWSA), north-eastern South Africa (NESA) and western South Africa (WSA). Although not variable enough to warrant taxonomic re-evaluation, the clades represented important genetic hotspots, with relatively high intraspecific genetic divergence values separating them, irrespective of the small geographic distances separating populations. This is likely a product of the taxon’s habitat-generalist lifestyle, enabling them to bypass vicariant barriers that might otherwise cause speciation in less versatile species. The clades are also geographically distinct, with little overlap, indicating previous vicariance, a finding that is supported by the split of Ps. rhombeatus from Ps. ocellatus in the mid-Pliocene, followed by the diversification of Ps. rhombeatus into four clades throughout the Pleistocene. The genetic structuring observed in Ps. rhombeatus may be a product of population expansion following ancient refugial isolation (potentially Last Glacial Maximum [LGM]). The molecular distinctiveness of the clades was not replicated in the morphological component of this chapter, with neither dorsal nor lateral geometric morphometric analyses of head shape showing any discernible distinctiveness based on geography. Whilst head shape has not been shown to be an effective delineator of evolutionary units at the species level (within this taxon), body colour, scalation, and snout-vent length has been linked to morphotypes within the species based on the work of Broadley (1966). These morphological groupings are loosely attributable to the molecular clades identified in the phylogenetic analyses, highlighting the complex interplay of genetic and morphological characteristics in the process of speciation, and their representation in systematic accounts. This thesis represents the most thorough evolutionary and systematic study of the family currently possible. In addition to identifying and describing both a new genus and species, this thesis also highlighted several instances of an over- and under-appreciation of species diversity within Psammophiidae. By applying a multi-evidence species delineation approach to this thesis, I show the intricacy of the evolutionary process (at various taxonomic levels) and showcase the ease to which species boundaries can be confounded when species concepts are implemented in isolation. These findings also highlighted the importance of sample size, sample range, species delimitation method on the outcome of taxonomic analyses, and their interpretation. Lastly, this thesis addressed the knowledge gaps left by Christopher Kelly’s PhD work and investigated the findings of recent papers that attempted to do the same. Whilst this study answers the questions of old, the taxon-intensive focus revealed several new knowledge gaps within the family, highlighting how much we know about snake systematics, and furthermore, how much we still need to learn about evolutionary structuring. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10-29
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