The invasion ecology of Pontederia cordata L. (Pontederiaceae) in South Africa
- Authors: Wansell, Sage Nora-Lee
- Date: 2021
- Subjects: Plant invsions -- South AFrica , Invasive plants -- Ecology -- South Africa , Pontederiaceae -- South AFrica
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/172433 , vital:42200
- Description: Pontederia cordata L. (Pontederiaceae) is a tristylous invasive macrophyte – originating from North and South America – that has caused detrimental environmental, agricultural and socio-economic impacts in South Africa (SA). This novel study investigates the invasive ecology of P. cordata in SA by determining population genetics, pollination ecology and floral traits. Preliminary field surveys suggest that only one of three tristylous forms of P. cordata is invading SA and no seeds have been observed in any invasive populations. This study therefore determined the population genetics, mode of spread of P. cordata in SA and possible reasons for the lack of seed production, as well as providing suggestions for future control and management strategies. Inter Simple Sequence Repeats of leaf samples from invasive populations in SA and the native range of the United States of America (USA) were performed to determine the population genetics of P. cordata. The clarification of population structure of an alien invasive plant can provide insight into founder effects, introduction events and modes of spread and is important for the development of management plans such as biological control. Results from the genetic analyses indicated that P. cordata populations have low genetic diversity within and amongst invasive populations in comparison to native populations. This suggests that high gene flow and sexual reproduction is not present in invasive populations, and that only a single or very few introductory events have occurred in SA. Furthermore, invasive P. cordata populations shared the highest genetic similarity with native samples from Belle Haven, Virginia, USA, and thus further sampling and future genetic surveys should be conducted in this area to identify source populations to survey for potential biological control agents. Following these findings, I investigated whether sexual reproduction and seed production is absent from invasive P. cordata populations in SA as speculated. Floral traits from populations throughout all the invaded provinces were measured and, along with pollen grain measurements, it was determined that only short-morphed plants are present in SA. It was speculated that the absence of native pollinators in the invasive range may be responsible for the absence of sexual reproduction. However, a pollination study confirmed the presence of generalist insect pollinators. Thereafter, artificial pollination experiments on 8 865 flowers were conducted to determine whether an incompatibility system was present which prevented seed production. No seeds were produced and it was concluded that illegitimate pollination of the short-morphed plants prevented seed production and rhizomes are responsible for the invasion of P. cordata throughout SA. The implications of these findings and possible management strategies such as biological control is discussed in Chapter 4. These findings suggest that control programmes should target the plants rhizomes to prevent and reduce spread. Preventing the introduction of medium- and long-morphed plants into SA is crucial to prevent P. cordata from producing seeds and intensifying invasion further through both asexual and sexual spread.
- Full Text:
- Date Issued: 2021
- Authors: Wansell, Sage Nora-Lee
- Date: 2021
- Subjects: Plant invsions -- South AFrica , Invasive plants -- Ecology -- South Africa , Pontederiaceae -- South AFrica
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/172433 , vital:42200
- Description: Pontederia cordata L. (Pontederiaceae) is a tristylous invasive macrophyte – originating from North and South America – that has caused detrimental environmental, agricultural and socio-economic impacts in South Africa (SA). This novel study investigates the invasive ecology of P. cordata in SA by determining population genetics, pollination ecology and floral traits. Preliminary field surveys suggest that only one of three tristylous forms of P. cordata is invading SA and no seeds have been observed in any invasive populations. This study therefore determined the population genetics, mode of spread of P. cordata in SA and possible reasons for the lack of seed production, as well as providing suggestions for future control and management strategies. Inter Simple Sequence Repeats of leaf samples from invasive populations in SA and the native range of the United States of America (USA) were performed to determine the population genetics of P. cordata. The clarification of population structure of an alien invasive plant can provide insight into founder effects, introduction events and modes of spread and is important for the development of management plans such as biological control. Results from the genetic analyses indicated that P. cordata populations have low genetic diversity within and amongst invasive populations in comparison to native populations. This suggests that high gene flow and sexual reproduction is not present in invasive populations, and that only a single or very few introductory events have occurred in SA. Furthermore, invasive P. cordata populations shared the highest genetic similarity with native samples from Belle Haven, Virginia, USA, and thus further sampling and future genetic surveys should be conducted in this area to identify source populations to survey for potential biological control agents. Following these findings, I investigated whether sexual reproduction and seed production is absent from invasive P. cordata populations in SA as speculated. Floral traits from populations throughout all the invaded provinces were measured and, along with pollen grain measurements, it was determined that only short-morphed plants are present in SA. It was speculated that the absence of native pollinators in the invasive range may be responsible for the absence of sexual reproduction. However, a pollination study confirmed the presence of generalist insect pollinators. Thereafter, artificial pollination experiments on 8 865 flowers were conducted to determine whether an incompatibility system was present which prevented seed production. No seeds were produced and it was concluded that illegitimate pollination of the short-morphed plants prevented seed production and rhizomes are responsible for the invasion of P. cordata throughout SA. The implications of these findings and possible management strategies such as biological control is discussed in Chapter 4. These findings suggest that control programmes should target the plants rhizomes to prevent and reduce spread. Preventing the introduction of medium- and long-morphed plants into SA is crucial to prevent P. cordata from producing seeds and intensifying invasion further through both asexual and sexual spread.
- Full Text:
- Date Issued: 2021
The potential conflict of interest associated with the management of Rosa rubiginos L. (Rosehip) in South Africa
- Authors: Westwood, Timothy
- Date: 2021
- Subjects: Invasive plants -- South Africa , Biological invasions -- Economic aspects , Rose hips -- Economic aspects -- South Africa , Roses -- South Africa , Rose culture -- Economic aspects -- South Africa
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/172458 , vital:42204
- Description: Rosa rubiginosa L. is a category 1b invasive plant species in South Africa and must be controlled according to NEM:BA. However, R. rubiginosa has the potential to provide economic benefit in South Africa due to the expanding market for the shrubs fruit, rosehips. The shrub is not permitted to be cultivated in South Africa due to legislation, limiting the economic potential as the rosehips are only able to be collected from wild R. rubiginosa shrubs. In order to expand the rosehip market in South Africa a downgrade or removal of R. rubiginosa from the invasive species list would be required, as wild harvest is limited. This study aims to assess the benefits and cost associated with R. rubiginosa in order to determine whether the legislation should be altered allowing for the cultivation of the shrub in South Africa. Due to the limited literature surrounding R. rubiginosa three different questionnaires and a case study were used in order to assess the benefits and negatives associated with the shrub. Experts in the field of invasion biology were surveyed to bridge the gap in the R. rubiginosa literature. Landowners, where the shrub is abundant, were surveyed to determine the negative impacts of R. rubiginosa. Rosehip companies were surveyed in order to determine the current size and potential of the R. rubiginosa (rosehip) market. The case study looked at how a rosehip company would benefit if R. rubiginosa was allowed to be cultivated in South Africa. The study found R. rubiginosa to have great economic potential and market growth, with very little negative economic impact. The case study showed that one rosehip company would grow from 1500 tons of raw rosehip to 20 000 tons if cultivation was allowed, resulting in a growth in turnover from R57 million to R760 million ($1=R14.8). The findings in the study show that R. rubiginosa does not significantly affect landowners where it is abundant. Therefore, it is suggested that a change to the legislation should be considered allowing for the cultivation of R. rubiginosa should be implemented.
- Full Text:
- Date Issued: 2021
- Authors: Westwood, Timothy
- Date: 2021
- Subjects: Invasive plants -- South Africa , Biological invasions -- Economic aspects , Rose hips -- Economic aspects -- South Africa , Roses -- South Africa , Rose culture -- Economic aspects -- South Africa
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/172458 , vital:42204
- Description: Rosa rubiginosa L. is a category 1b invasive plant species in South Africa and must be controlled according to NEM:BA. However, R. rubiginosa has the potential to provide economic benefit in South Africa due to the expanding market for the shrubs fruit, rosehips. The shrub is not permitted to be cultivated in South Africa due to legislation, limiting the economic potential as the rosehips are only able to be collected from wild R. rubiginosa shrubs. In order to expand the rosehip market in South Africa a downgrade or removal of R. rubiginosa from the invasive species list would be required, as wild harvest is limited. This study aims to assess the benefits and cost associated with R. rubiginosa in order to determine whether the legislation should be altered allowing for the cultivation of the shrub in South Africa. Due to the limited literature surrounding R. rubiginosa three different questionnaires and a case study were used in order to assess the benefits and negatives associated with the shrub. Experts in the field of invasion biology were surveyed to bridge the gap in the R. rubiginosa literature. Landowners, where the shrub is abundant, were surveyed to determine the negative impacts of R. rubiginosa. Rosehip companies were surveyed in order to determine the current size and potential of the R. rubiginosa (rosehip) market. The case study looked at how a rosehip company would benefit if R. rubiginosa was allowed to be cultivated in South Africa. The study found R. rubiginosa to have great economic potential and market growth, with very little negative economic impact. The case study showed that one rosehip company would grow from 1500 tons of raw rosehip to 20 000 tons if cultivation was allowed, resulting in a growth in turnover from R57 million to R760 million ($1=R14.8). The findings in the study show that R. rubiginosa does not significantly affect landowners where it is abundant. Therefore, it is suggested that a change to the legislation should be considered allowing for the cultivation of R. rubiginosa should be implemented.
- Full Text:
- Date Issued: 2021
Development and calidation of the psychometric properties underpinning the Kwaito Music Attitude and Perception Scale (KMP)
- Authors: Williams, Akhona
- Date: 2021
- Subjects: Kwaito-music Attitude and Perception , Chronbach's alpha , Kwaito (Music) , Psychotherapy and music -- South Africa , Problem youth -- Rehabilitation -- South Africa , Attitude (Psychology) -- Testing -- South Africa , Perception -- Testing -- South Africa
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/172478 , vital:42208
- Description: Music holds a privileged position in enhancing therapeutic well-being, supporting life skills development in youth and adolescents, and shaping cultural identities. As such, music has been closely related to youth culture, especially as it pertains to youth rehabilitation and identity formation. Studies (e.g., Duffy and Fuller, 2000; Miranda et al, 2013; Strayhorn, 2011; Tomasello, 2016) highlight the value of utilising music in youth rehabilitation, and acknowledge the intrinsic value of music to facilitate psychological and social change for individuals who would not otherwise benefit from psycho-education, or other didactic modes of youth rehabilitation. That said, Tyson (2005) developed the RAP music scale to psychometrically validate the underlying constructs of youth’ attitudes and perception of rap music in the United States of America, in order to use the instrument for music-based youth rehabilitation programs. The development of the RAP music scale informed the creation and validation of the Kwaito-music Attitude and Perception (KMP) Scale, the subject of my Masters thesis. Following suggestions from Morrison (2014), my study sought to psychometrically validate the properties of the Kwaito-music Attitude and Perception (KMP) Scale. The KMP was found to be a reliable measure of kwaito music attitudes and perception amongst a sample of South African youth who listen to this genre of music. The internal consistency of the questionnaire revealed a Cronbach’s α (Alpha) value of 0.820. Limitations of the project including reduced factor extraction and sample size constrains are discussed. It is envisioned that results from this study will find resonance with youth-community programs, and rehabilitation projects utilising music as a medium of healing amongst South African youth.
- Full Text:
- Date Issued: 2021
- Authors: Williams, Akhona
- Date: 2021
- Subjects: Kwaito-music Attitude and Perception , Chronbach's alpha , Kwaito (Music) , Psychotherapy and music -- South Africa , Problem youth -- Rehabilitation -- South Africa , Attitude (Psychology) -- Testing -- South Africa , Perception -- Testing -- South Africa
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/172478 , vital:42208
- Description: Music holds a privileged position in enhancing therapeutic well-being, supporting life skills development in youth and adolescents, and shaping cultural identities. As such, music has been closely related to youth culture, especially as it pertains to youth rehabilitation and identity formation. Studies (e.g., Duffy and Fuller, 2000; Miranda et al, 2013; Strayhorn, 2011; Tomasello, 2016) highlight the value of utilising music in youth rehabilitation, and acknowledge the intrinsic value of music to facilitate psychological and social change for individuals who would not otherwise benefit from psycho-education, or other didactic modes of youth rehabilitation. That said, Tyson (2005) developed the RAP music scale to psychometrically validate the underlying constructs of youth’ attitudes and perception of rap music in the United States of America, in order to use the instrument for music-based youth rehabilitation programs. The development of the RAP music scale informed the creation and validation of the Kwaito-music Attitude and Perception (KMP) Scale, the subject of my Masters thesis. Following suggestions from Morrison (2014), my study sought to psychometrically validate the properties of the Kwaito-music Attitude and Perception (KMP) Scale. The KMP was found to be a reliable measure of kwaito music attitudes and perception amongst a sample of South African youth who listen to this genre of music. The internal consistency of the questionnaire revealed a Cronbach’s α (Alpha) value of 0.820. Limitations of the project including reduced factor extraction and sample size constrains are discussed. It is envisioned that results from this study will find resonance with youth-community programs, and rehabilitation projects utilising music as a medium of healing amongst South African youth.
- Full Text:
- Date Issued: 2021