An investigation into the influence of the physical distribution concept on the performance of certain South African manufacturers of consumer products
- Authors: Staude, G E
- Date: 1981
- Subjects: Physical distribution of goods Industrial productivity -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1191 , http://hdl.handle.net/10962/d1004606
- Description: The "Physical Distribution Concept" is being increasingly recognised as a vitally important business philosophy for those firms for which efficient physical distribution is critical to marketing success. Manufacturers of products which are perishable, easily substitutable; and/or quickly obsolescent are some which fall into this category. In a competitive business environment, factors such as the " availability" of the product, and not simply its price or quality, begin to exert a significant influence on the purchasing decision. The "Physical Distribution Concept" comprises three elements, namely, consumer orientation; organizational integration and profit orientation. "Physical Distribution Orientation" refers to the predisposition of the firm and its employees to these three elements. For the Physical Distribution Concept to serve as an effective guide to management action, a physical distribution orientation on the part of all those concerned with marketing and physical distribution-related activities in a firm, is a pre-requisite. The chief executive, in particular, should adhere to this business philosophy, regardless of the functional route he followed to his position. In his leadership role, theory holds that he exerts considerable influence on his subordinates, and consequently on his firm's way of doing business. This thesis is concerned with an analysis of the Physical Distribution Concept. It focuses on the chief executives of firms manufacturing consumer convenience goods, as well as consumer shopping goods. As such, it is primarily concerned with determining the extent to which the chief executives are physical distribution oriented and whether there is a statistically significant relationship between their extent of physical distribution orientation and their companies' performance. The thesis is also concerned with the extent to which any pattern of organizational arr angements for physical distribution exists.
- Full Text:
- Date Issued: 1981
- Authors: Staude, G E
- Date: 1981
- Subjects: Physical distribution of goods Industrial productivity -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1191 , http://hdl.handle.net/10962/d1004606
- Description: The "Physical Distribution Concept" is being increasingly recognised as a vitally important business philosophy for those firms for which efficient physical distribution is critical to marketing success. Manufacturers of products which are perishable, easily substitutable; and/or quickly obsolescent are some which fall into this category. In a competitive business environment, factors such as the " availability" of the product, and not simply its price or quality, begin to exert a significant influence on the purchasing decision. The "Physical Distribution Concept" comprises three elements, namely, consumer orientation; organizational integration and profit orientation. "Physical Distribution Orientation" refers to the predisposition of the firm and its employees to these three elements. For the Physical Distribution Concept to serve as an effective guide to management action, a physical distribution orientation on the part of all those concerned with marketing and physical distribution-related activities in a firm, is a pre-requisite. The chief executive, in particular, should adhere to this business philosophy, regardless of the functional route he followed to his position. In his leadership role, theory holds that he exerts considerable influence on his subordinates, and consequently on his firm's way of doing business. This thesis is concerned with an analysis of the Physical Distribution Concept. It focuses on the chief executives of firms manufacturing consumer convenience goods, as well as consumer shopping goods. As such, it is primarily concerned with determining the extent to which the chief executives are physical distribution oriented and whether there is a statistically significant relationship between their extent of physical distribution orientation and their companies' performance. The thesis is also concerned with the extent to which any pattern of organizational arr angements for physical distribution exists.
- Full Text:
- Date Issued: 1981
Biotic and abiotic factors promoting the development and proliferation of water hyacinth (eichhornia crassipes (Mart.) Solms-Laub.) in the Wouri Basin (Douala-Cameroon) and environs, with implications for its control
- Voukeng, Sonia Nadege Kenfack
- Authors: Voukeng, Sonia Nadege Kenfack
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/7644 , vital:21281
- Description: The Wouri River, situated in the Wouri Basin, is one of the main rivers of the Littoral Region in the city of Douala in Cameroon. It is a source of income and food for the population living around these areas. Since the 1990s, the fishing, transportation, irrigation and sand extraction activities have been impeded by the invasion of aquatic plants, specifically water hyacinth (Eichhornia crassipes [Mart.] Solms-Laubach: Pontederiaceae). Introduced in 1997 to the shore of Lake Chad, water hyacinth has invaded almost 114 ha of the Wouri Basin. Furthermore, Douala, the economic capital of the Cameroon and location for more than 70% of the country’s industries, uses the Wouri River and its tributaries to deposit its effluent and waste, which has worsened the problem of water hyacinth. This thesis examined the ecological and socio-economic impacts of water hyacinth in the Wouri Basin and its possible control. An increase in the nutrients in the water has provided water hyacinth with appropriate conditions for its fast growth during both the rainy and dry seasons. The availability of nutrients in these areas is enhanced by the constant, daily tidal fluctuation of water, providing enough water to the plant for easy nutrient uptake. A survey of the impacts of water hyacinth on aquatic plant communities in the Wouri Basin showed that this plant is able to out-compete native species. Assessment of the impact of water hyacinth on the abundance and diversity of plant communities indicated that at some invaded sites, 65% of the vegetation consisted of water hyacinth. Species found in association with water hyacinth with a high level of abundance-dominance were Pistia stratiotes L. (Araceae) (another invader), Commelina benghalensis L. (Commelinaceae) and Echinochloa pyramidalis (Lam.) Hitchc. & Chase (Poaceae). This component of the study also showed that habitats rich in water hyacinth were poor in diversity, while habitats without water hyacinth were rich in diversity, thus raising awareness of the importance of monitoring invasive aquatic weeds along the Wouri Basin, and of implementing correct control management of all invasive aquatic weeds. Communities living along the invaded rivers are well aware of the range of problems caused by the weed; because as the rivers and water bodies used for fishing, transportation, and sand extraction are progressively invaded by the weed, the riparian population is the first to feel the impact. The impact on people has been noticeable, with an increase in diseases, such as malaria, cholera, diarrhoea, typhoid, filariasis, schistosomiasis, scabies and yellow fever increasing the need for a medicine and hospitalization. Economic losses due to the management of invasive aquatic weeds were recorded, and the Ministry of Environment spent an estimated US$1 200 000 between 2010 and 2015 to manage this scourge. In 2016, an amount of US$160 000 was transferred to these regions to manage invasive aquatic weeds, especially water hyacinth, although manual clearing is still the only method used to control this weed. Isolation of fungi from diseased water hyacinth plants in the Wouri Basin revealed several fungal species, most of which have been isolated from water hyacinth species in water bodies elsewhere, which showed a higher diversity during the dry season than during the rainy season. These fungi included Acremonium zonatum (Sawada). W. Gams (Hypocreaceae), Alternaria eichhorniae Nag Raj & Ponnappa (Pleosporaceae), Chaetomium sp., Colletotrichum sp., Curvularia pallescens Boedjin (Pleosporaceae), Curvalaria sp., Epicoccum nigrum Link (Pleosporaceae), Fusarium sp., Pithomyces chartarum fBerk. & M. A. Curtis) M. B. Ellis (Montagnulaceae), to a lesser extent Myrothecium roridum Tode ex Fr. (Incertae sedis) and Nigrospora sp. Although never released in Cameroon, arthropod biological control agents (Neochetina eichhorniae Warner (Coleoptera, Curculionidae) and N. bruchi Hustache (Coleoptera, Curculionidae)) were present, but their populations were relatively low. The slow spread of the insect population was explained by several factors, among them the tidal fluctuation of water, which has an impact on the population growth of the weevils. Whilst adults may be able to survive tidal fluctuations, larvae are severely impacted by them, contributing to the slow success of biological control. In this study, a significant increase in pathogen-induced disease severity and incidence was noted when Neochetina eichhorniae weevils were present, possibly because larvae tunnelling on the petiole created openings for the penetration of fungal spores. This study highlights the negative impacts of water hyacinth, on the environment, people, and thus economy of Cameroon. The presence of biological control agents and pathogens offers Cameroon the possibility of initiating and properly implementing the biological control option, or an integrated management solution, to manage water hyacinth in the Wouri Basin, and in the rest of Cameroon.
- Full Text:
- Date Issued: 2017
- Authors: Voukeng, Sonia Nadege Kenfack
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/7644 , vital:21281
- Description: The Wouri River, situated in the Wouri Basin, is one of the main rivers of the Littoral Region in the city of Douala in Cameroon. It is a source of income and food for the population living around these areas. Since the 1990s, the fishing, transportation, irrigation and sand extraction activities have been impeded by the invasion of aquatic plants, specifically water hyacinth (Eichhornia crassipes [Mart.] Solms-Laubach: Pontederiaceae). Introduced in 1997 to the shore of Lake Chad, water hyacinth has invaded almost 114 ha of the Wouri Basin. Furthermore, Douala, the economic capital of the Cameroon and location for more than 70% of the country’s industries, uses the Wouri River and its tributaries to deposit its effluent and waste, which has worsened the problem of water hyacinth. This thesis examined the ecological and socio-economic impacts of water hyacinth in the Wouri Basin and its possible control. An increase in the nutrients in the water has provided water hyacinth with appropriate conditions for its fast growth during both the rainy and dry seasons. The availability of nutrients in these areas is enhanced by the constant, daily tidal fluctuation of water, providing enough water to the plant for easy nutrient uptake. A survey of the impacts of water hyacinth on aquatic plant communities in the Wouri Basin showed that this plant is able to out-compete native species. Assessment of the impact of water hyacinth on the abundance and diversity of plant communities indicated that at some invaded sites, 65% of the vegetation consisted of water hyacinth. Species found in association with water hyacinth with a high level of abundance-dominance were Pistia stratiotes L. (Araceae) (another invader), Commelina benghalensis L. (Commelinaceae) and Echinochloa pyramidalis (Lam.) Hitchc. & Chase (Poaceae). This component of the study also showed that habitats rich in water hyacinth were poor in diversity, while habitats without water hyacinth were rich in diversity, thus raising awareness of the importance of monitoring invasive aquatic weeds along the Wouri Basin, and of implementing correct control management of all invasive aquatic weeds. Communities living along the invaded rivers are well aware of the range of problems caused by the weed; because as the rivers and water bodies used for fishing, transportation, and sand extraction are progressively invaded by the weed, the riparian population is the first to feel the impact. The impact on people has been noticeable, with an increase in diseases, such as malaria, cholera, diarrhoea, typhoid, filariasis, schistosomiasis, scabies and yellow fever increasing the need for a medicine and hospitalization. Economic losses due to the management of invasive aquatic weeds were recorded, and the Ministry of Environment spent an estimated US$1 200 000 between 2010 and 2015 to manage this scourge. In 2016, an amount of US$160 000 was transferred to these regions to manage invasive aquatic weeds, especially water hyacinth, although manual clearing is still the only method used to control this weed. Isolation of fungi from diseased water hyacinth plants in the Wouri Basin revealed several fungal species, most of which have been isolated from water hyacinth species in water bodies elsewhere, which showed a higher diversity during the dry season than during the rainy season. These fungi included Acremonium zonatum (Sawada). W. Gams (Hypocreaceae), Alternaria eichhorniae Nag Raj & Ponnappa (Pleosporaceae), Chaetomium sp., Colletotrichum sp., Curvularia pallescens Boedjin (Pleosporaceae), Curvalaria sp., Epicoccum nigrum Link (Pleosporaceae), Fusarium sp., Pithomyces chartarum fBerk. & M. A. Curtis) M. B. Ellis (Montagnulaceae), to a lesser extent Myrothecium roridum Tode ex Fr. (Incertae sedis) and Nigrospora sp. Although never released in Cameroon, arthropod biological control agents (Neochetina eichhorniae Warner (Coleoptera, Curculionidae) and N. bruchi Hustache (Coleoptera, Curculionidae)) were present, but their populations were relatively low. The slow spread of the insect population was explained by several factors, among them the tidal fluctuation of water, which has an impact on the population growth of the weevils. Whilst adults may be able to survive tidal fluctuations, larvae are severely impacted by them, contributing to the slow success of biological control. In this study, a significant increase in pathogen-induced disease severity and incidence was noted when Neochetina eichhorniae weevils were present, possibly because larvae tunnelling on the petiole created openings for the penetration of fungal spores. This study highlights the negative impacts of water hyacinth, on the environment, people, and thus economy of Cameroon. The presence of biological control agents and pathogens offers Cameroon the possibility of initiating and properly implementing the biological control option, or an integrated management solution, to manage water hyacinth in the Wouri Basin, and in the rest of Cameroon.
- Full Text:
- Date Issued: 2017
Science teachers' transformative and continuous professional development : a journey towards capacity-building and reflexive practice
- Authors: Ngcoza, Kenneth Mlungisi
- Date: 2013-07-16
- Subjects: Curriculum change -- South Africa Science -- Study and teaching (Secondary) -- South Africa -- Grahamstown Science teachers -- In-service training -- South Africa -- Grahamstown Educational change -- South Africa -- Grahamstown Education -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1953 , http://hdl.handle.net/10962/d1008258
- Description: This study was conducted in Grahamstown in the Eastern Cape, South Mrica. Triggered by the demands of South Mrican post-apartheid curriculum transformation, the study focused on establishing a sustainable science teachers' trans formative and continuous professional development (TTCPD) network with the view to improving their practice. It is premised on the assumption that teachers are capable of taking responsibility for their own professional development. It is a case study carried over a period offour years with a group of eight teachers. Rooted in the socially critical-emancipatory orientation in conjunction with the participatory action research approach, and located in the qualitative and interpretive research paradigms, it focuses on doing research in democratic and egalitarian ways through working with teachers rather than on them. Such a stance supposes a collaborative partnership and a dialogic relationship viewed as being both reciprocal and mutually enriching for the teachers who were seen as co-learners and co-researchers in this study. Two main goals of the study may be identified. For the first goal, the actors in this study established a sustainable and participative approach to professional development. This was explored through the formation of a TTCPD network which was informed by the actor-network theory framework. Our focus was on co-construction of scientific knowledge utilising the development and adaptation of learning and teaching support materials (LTSMs) as a catalyst to drive the process. The second goal was to examine how the TTCPD network enhanced the teachers' subject-content knowledge, pedagogical-content knowledge as well as individual and collaborative reflections. The research process evolved into three mam phases: The initial phase involved adapting and modifying LTSMs which were initially used in conjunction with microscale science kits and pilot tested with a group of Grade 10 students. This led to the second phase of the research project, which was aimed at gaining insights into the science teachers' capabilities in developing teaching and learning units of work. ii \ The second phase focused on the development of a collaborative orientation to the development of LTSMs and culminated in the formation of sub-networks responsible for certain tasks within the broader network. AB common ground, we focused on developing teaching and learning units of work on the following science topics: electrostatics, electricity, and electrochemistry, to illuminate and foster integration within science. The third phase was concerned with gaining insights into the science teachers' practice in their classrooms. This phase focused on putting theory into practice through the collaborative implementation of teaching and learning units of work. Feedback on the lessons was discussed during our workshops as an attempt to further enhance collaborative reflections. Data was generated usmg workshop discussions with reflective notes; active interviews; focus group discussions; co-teaching, participant observation and videotaped lessons with reflective notes; and a research journal. A variety of data generation techniques were employed to enhance validity and quality of the research. Techniques for validation and trustworthiness of data included triangulation; member checks orface validity; prolonged engagement; catalytic validity and peer validation. The study exposed the underlying historical, ideological and epistemological contradictions of the teachers' past educational backgrounds. It emerged that the ways in which they were taught were at times an inhibitor to innovativeness, perpetuating transmissive approaches to teaching and learning. Lack of professional development and support, and the tensions between policy formulation and implementation exacerbated this. Reflections from the teachers' experiences further revealed that, for teachers to be effective agents of change in the reform process, empowerment opportunities are vital. AB a result, exposure to the TTCPD network was useful in capacitating the teachers with the development of LTSMs, which led to the enhancement of their pedagogical, and science content knowledge conceptual development as well as collaborative reflections.The main findings of this study is that, science teachers' transformative and continuous professional development based on participative approaches and mutual collegial support are indispensable, and that teachers' socio-cultural contexts and experiences should be taken into consideration during this process. Teachers should be regarded as central in the process, and mutual respect and dialogical relationships are pivotal. A further recommendation of this study is that capacity-building is critical for quality teaching and learning, and there is a need to move beyond the rhetoric of complacency to pro-activism, supporting ongoing development of teachers in professional transformative networks. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Ngcoza, Kenneth Mlungisi
- Date: 2013-07-16
- Subjects: Curriculum change -- South Africa Science -- Study and teaching (Secondary) -- South Africa -- Grahamstown Science teachers -- In-service training -- South Africa -- Grahamstown Educational change -- South Africa -- Grahamstown Education -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1953 , http://hdl.handle.net/10962/d1008258
- Description: This study was conducted in Grahamstown in the Eastern Cape, South Mrica. Triggered by the demands of South Mrican post-apartheid curriculum transformation, the study focused on establishing a sustainable science teachers' trans formative and continuous professional development (TTCPD) network with the view to improving their practice. It is premised on the assumption that teachers are capable of taking responsibility for their own professional development. It is a case study carried over a period offour years with a group of eight teachers. Rooted in the socially critical-emancipatory orientation in conjunction with the participatory action research approach, and located in the qualitative and interpretive research paradigms, it focuses on doing research in democratic and egalitarian ways through working with teachers rather than on them. Such a stance supposes a collaborative partnership and a dialogic relationship viewed as being both reciprocal and mutually enriching for the teachers who were seen as co-learners and co-researchers in this study. Two main goals of the study may be identified. For the first goal, the actors in this study established a sustainable and participative approach to professional development. This was explored through the formation of a TTCPD network which was informed by the actor-network theory framework. Our focus was on co-construction of scientific knowledge utilising the development and adaptation of learning and teaching support materials (LTSMs) as a catalyst to drive the process. The second goal was to examine how the TTCPD network enhanced the teachers' subject-content knowledge, pedagogical-content knowledge as well as individual and collaborative reflections. The research process evolved into three mam phases: The initial phase involved adapting and modifying LTSMs which were initially used in conjunction with microscale science kits and pilot tested with a group of Grade 10 students. This led to the second phase of the research project, which was aimed at gaining insights into the science teachers' capabilities in developing teaching and learning units of work. ii \ The second phase focused on the development of a collaborative orientation to the development of LTSMs and culminated in the formation of sub-networks responsible for certain tasks within the broader network. AB common ground, we focused on developing teaching and learning units of work on the following science topics: electrostatics, electricity, and electrochemistry, to illuminate and foster integration within science. The third phase was concerned with gaining insights into the science teachers' practice in their classrooms. This phase focused on putting theory into practice through the collaborative implementation of teaching and learning units of work. Feedback on the lessons was discussed during our workshops as an attempt to further enhance collaborative reflections. Data was generated usmg workshop discussions with reflective notes; active interviews; focus group discussions; co-teaching, participant observation and videotaped lessons with reflective notes; and a research journal. A variety of data generation techniques were employed to enhance validity and quality of the research. Techniques for validation and trustworthiness of data included triangulation; member checks orface validity; prolonged engagement; catalytic validity and peer validation. The study exposed the underlying historical, ideological and epistemological contradictions of the teachers' past educational backgrounds. It emerged that the ways in which they were taught were at times an inhibitor to innovativeness, perpetuating transmissive approaches to teaching and learning. Lack of professional development and support, and the tensions between policy formulation and implementation exacerbated this. Reflections from the teachers' experiences further revealed that, for teachers to be effective agents of change in the reform process, empowerment opportunities are vital. AB a result, exposure to the TTCPD network was useful in capacitating the teachers with the development of LTSMs, which led to the enhancement of their pedagogical, and science content knowledge conceptual development as well as collaborative reflections.The main findings of this study is that, science teachers' transformative and continuous professional development based on participative approaches and mutual collegial support are indispensable, and that teachers' socio-cultural contexts and experiences should be taken into consideration during this process. Teachers should be regarded as central in the process, and mutual respect and dialogical relationships are pivotal. A further recommendation of this study is that capacity-building is critical for quality teaching and learning, and there is a need to move beyond the rhetoric of complacency to pro-activism, supporting ongoing development of teachers in professional transformative networks. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
Systematics, morphology, phylogeny and historical biogeography of the Mayfly family Prosopistomatidae (Ephemeroptera: Insecta) of the world
- Barber-James, Helen Margaret
- Authors: Barber-James, Helen Margaret
- Date: 2011
- Subjects: Mayflies Mayflies -- Classification Mayflies -- Morphology Mayflies -- Phylogeny Mayflies -- Geographical distribution Ephemeridae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5785 , http://hdl.handle.net/10962/d1005473
- Description: The diversity, classification and historical biogeography of the mayfly family Prosopistomatidae are explored. First, the higher classification of the Ephemeroptera is reviewed, focussing on the phylogenetic placement of the Prosopistomatidae relative to other mayfly families. All relevant literature from 1762 to 2010 is synthesized. Baetiscidae are established as the probable sister lineage of Prosopistomatidae, the two constituting the superfamily Baetiscoidea. Next, qualitative morphological variation within the Prosopistomatidae is reviewed and revised, emphasizing nymphs because imaginal specimens are few. The labium and associated structures and the hypopharynx of nymphs, and the highly-derived wing venation of the imaginal stages, are re-interpreted. The structure of the male tarsal claws changes considerably between subimago and imago, which, together with deeply scalloped ridges on male imaginal forelegs and unusual pits on the female thorax, are interpreted as providing an unusual mating mechanism. These structures provide morphological characters for species definition and phylogenetic analyses. Two approaches to species delimitation are explored. First, morphometric variation is analysed using Principal Component Analysis, revealing groupings that can be interpreted as species, although there is some overlap between them. Discriminant Function Analysis shows that head width and carapace shape have the most value in identifying nymphs of different species. The carapace of Prosopistoma nymphs is shown to grow allometrically and gradually, in contrast with that of Baetisca, indicating a difference in early ontogeny. Second, an Artificial Neural Network algorithm applied to nymphal morphological characters accurately identified species. This computer-driven artificial intelligence method has power to provide future easy-to-use electronic identification aids. Phylogenetic analysis of nymphal morphology using the parsimony method shows two clades of Prosopistomatidae, one sharing characters with the type species, Prosopistoma variegatum and the other predominating in Africa, although also occurring in Asia; these clades are named the “P. variegatum” and “African” clades, respectively. Parsimony analysis of adult morphology supports these two clades, but supertree analysis obscures the relationships, nesting the “P. variegatum” lineage within the other clade. Preliminary molecular phylogenetic analysis of the 16S rRNA, (mitochondrial) 18S rRNA and Histone-3 genes using Bayesian Inference methods does not support the two clades shown by morphology. Instead, there is a strong relationship between the European species and one African species, with the single Asian representative being most distantly related. These results are limited by lack of fresh material, patchy taxon sampling, and problems with finding suitable primers. A molecular clock program, BEAST, calibrated using fossils, suggests divergence times for the oldest crown-group Prosopistoma clade, represented by the Asian P. wouterae, of about 131 Ma, with the youngest species, the African P. crassi, of 1.21 Ma. Stem-group relationships are analysed using parsimony analysis, focussing on wing characters of the Baetiscoidea, other extant mayfly lineages, and extinct stem-group lineages. This suggests that the Baetiscoidea diverged from main-line Ephemeroptera earlier than any other extant mayfly lineage. This approach expands upon ideas hinted at by earlier scientists. Finally, historical biogeographical analysis of the distribution of known Baetiscoidea s.s. stem-group fossils implies a once Pangean distribution of the lineage. Changing palaeo-climate, catastrophic extinction events and plate tectonic movements in relation to the distribution of crown-group species are reviewed. Other approaches to historical biogeography that build on both morphological and molecular phylogenies are used to interpret disperalist and vacarianist arguments. Distribution patterns of eight unrelated freshwater organisms which share a similar distribution pattern are compared, assuming that shared patterns indicate similar historic biogeographic processes. The distribution of recent Prosopistoma species is seen to be the product of evolution resulting from both vicariance and dispersal. In conclusion, this thesis encompasses a variety of disciplines. It successfully recognises new characters and distinguishes previously unknown species. It uses new approaches to delimiting species and known methods to determine phylogeny from several angles. The analysis of stem-group relationships offers an insight into possible early lineage splitting within Ephemeroptera. Interpretation of historical biogeography allows for both a Gondwanan origin of Prosopistomatidae, with rafting of species on the Deccan plate to Asia, and for subsequent dispersal from Asia down to Australia and across to Europe, and possibly back to Africa.
- Full Text:
- Date Issued: 2011
- Authors: Barber-James, Helen Margaret
- Date: 2011
- Subjects: Mayflies Mayflies -- Classification Mayflies -- Morphology Mayflies -- Phylogeny Mayflies -- Geographical distribution Ephemeridae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5785 , http://hdl.handle.net/10962/d1005473
- Description: The diversity, classification and historical biogeography of the mayfly family Prosopistomatidae are explored. First, the higher classification of the Ephemeroptera is reviewed, focussing on the phylogenetic placement of the Prosopistomatidae relative to other mayfly families. All relevant literature from 1762 to 2010 is synthesized. Baetiscidae are established as the probable sister lineage of Prosopistomatidae, the two constituting the superfamily Baetiscoidea. Next, qualitative morphological variation within the Prosopistomatidae is reviewed and revised, emphasizing nymphs because imaginal specimens are few. The labium and associated structures and the hypopharynx of nymphs, and the highly-derived wing venation of the imaginal stages, are re-interpreted. The structure of the male tarsal claws changes considerably between subimago and imago, which, together with deeply scalloped ridges on male imaginal forelegs and unusual pits on the female thorax, are interpreted as providing an unusual mating mechanism. These structures provide morphological characters for species definition and phylogenetic analyses. Two approaches to species delimitation are explored. First, morphometric variation is analysed using Principal Component Analysis, revealing groupings that can be interpreted as species, although there is some overlap between them. Discriminant Function Analysis shows that head width and carapace shape have the most value in identifying nymphs of different species. The carapace of Prosopistoma nymphs is shown to grow allometrically and gradually, in contrast with that of Baetisca, indicating a difference in early ontogeny. Second, an Artificial Neural Network algorithm applied to nymphal morphological characters accurately identified species. This computer-driven artificial intelligence method has power to provide future easy-to-use electronic identification aids. Phylogenetic analysis of nymphal morphology using the parsimony method shows two clades of Prosopistomatidae, one sharing characters with the type species, Prosopistoma variegatum and the other predominating in Africa, although also occurring in Asia; these clades are named the “P. variegatum” and “African” clades, respectively. Parsimony analysis of adult morphology supports these two clades, but supertree analysis obscures the relationships, nesting the “P. variegatum” lineage within the other clade. Preliminary molecular phylogenetic analysis of the 16S rRNA, (mitochondrial) 18S rRNA and Histone-3 genes using Bayesian Inference methods does not support the two clades shown by morphology. Instead, there is a strong relationship between the European species and one African species, with the single Asian representative being most distantly related. These results are limited by lack of fresh material, patchy taxon sampling, and problems with finding suitable primers. A molecular clock program, BEAST, calibrated using fossils, suggests divergence times for the oldest crown-group Prosopistoma clade, represented by the Asian P. wouterae, of about 131 Ma, with the youngest species, the African P. crassi, of 1.21 Ma. Stem-group relationships are analysed using parsimony analysis, focussing on wing characters of the Baetiscoidea, other extant mayfly lineages, and extinct stem-group lineages. This suggests that the Baetiscoidea diverged from main-line Ephemeroptera earlier than any other extant mayfly lineage. This approach expands upon ideas hinted at by earlier scientists. Finally, historical biogeographical analysis of the distribution of known Baetiscoidea s.s. stem-group fossils implies a once Pangean distribution of the lineage. Changing palaeo-climate, catastrophic extinction events and plate tectonic movements in relation to the distribution of crown-group species are reviewed. Other approaches to historical biogeography that build on both morphological and molecular phylogenies are used to interpret disperalist and vacarianist arguments. Distribution patterns of eight unrelated freshwater organisms which share a similar distribution pattern are compared, assuming that shared patterns indicate similar historic biogeographic processes. The distribution of recent Prosopistoma species is seen to be the product of evolution resulting from both vicariance and dispersal. In conclusion, this thesis encompasses a variety of disciplines. It successfully recognises new characters and distinguishes previously unknown species. It uses new approaches to delimiting species and known methods to determine phylogeny from several angles. The analysis of stem-group relationships offers an insight into possible early lineage splitting within Ephemeroptera. Interpretation of historical biogeography allows for both a Gondwanan origin of Prosopistomatidae, with rafting of species on the Deccan plate to Asia, and for subsequent dispersal from Asia down to Australia and across to Europe, and possibly back to Africa.
- Full Text:
- Date Issued: 2011
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