Contributions to the systematics and ecology of Tulista Raf(Asphodelaceae subfam. Alooideae)
- Authors: Molteno, Steven Martin
- Date: 2020
- Subjects: Plant ecology -- South Africa , Plant ecology -- Comparative method Biodiversity , Species diversity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49182 , vital:41608
- Description: The subject of this study is the taxonomy, morphology, distribution and ecology of Tulista Raf. (Asphodelaceae subfam. Alooideae), a genus of succulent plants that are endemic to South Africa. A lack of clarity on the taxonomy of this genus, coupled with an incomplete understanding of the distribution, ecology and habitat preferences of the constituent species, risks hampering the conservation of Tulista species, two of which are endangered species. The purpose of this study is therefore to address the need for a more detailed and consistent treatment of Tulista taxonomy and morphology, complemented by a study of the plants’ distribution and ecology. The work first provides a review of the relevant taxonomy and nomenclature, concluding with the presentation of the validly published names referring to Tulista. A detailed morphometric study resulted in strong support for one species, Tulista marginata (Lam.) G.D.Rowley, as well as for a grouping comprising Tulista pumila (L.) G.D.Rowley and Tulista minor (Aiton) Gideon F.Sm. & Molteno, with further moderate support for the distinction between the latter two species. The fourth out of the currently recognised species, Tulista kingiana (Poelln.) Gideon F.Sm. & Molteno, was only weakly characterised by the morphometric results, which suggested that its closest morphological affinity may be with hybrid plants that are sometimes found near T. marginata populations. The characterisation of some more controversial taxa was not supported in the results. Some changes to the circumscription of currently recognised Tulista species are also suggested by the results. In addition, field work conducted during the course of the study resulted in an expanded set of distribution data for the genus, together with certain habitat variables identified as potentially significant for the distribution and ecology of Tulista species.
- Full Text:
- Date Issued: 2020
- Authors: Molteno, Steven Martin
- Date: 2020
- Subjects: Plant ecology -- South Africa , Plant ecology -- Comparative method Biodiversity , Species diversity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49182 , vital:41608
- Description: The subject of this study is the taxonomy, morphology, distribution and ecology of Tulista Raf. (Asphodelaceae subfam. Alooideae), a genus of succulent plants that are endemic to South Africa. A lack of clarity on the taxonomy of this genus, coupled with an incomplete understanding of the distribution, ecology and habitat preferences of the constituent species, risks hampering the conservation of Tulista species, two of which are endangered species. The purpose of this study is therefore to address the need for a more detailed and consistent treatment of Tulista taxonomy and morphology, complemented by a study of the plants’ distribution and ecology. The work first provides a review of the relevant taxonomy and nomenclature, concluding with the presentation of the validly published names referring to Tulista. A detailed morphometric study resulted in strong support for one species, Tulista marginata (Lam.) G.D.Rowley, as well as for a grouping comprising Tulista pumila (L.) G.D.Rowley and Tulista minor (Aiton) Gideon F.Sm. & Molteno, with further moderate support for the distinction between the latter two species. The fourth out of the currently recognised species, Tulista kingiana (Poelln.) Gideon F.Sm. & Molteno, was only weakly characterised by the morphometric results, which suggested that its closest morphological affinity may be with hybrid plants that are sometimes found near T. marginata populations. The characterisation of some more controversial taxa was not supported in the results. Some changes to the circumscription of currently recognised Tulista species are also suggested by the results. In addition, field work conducted during the course of the study resulted in an expanded set of distribution data for the genus, together with certain habitat variables identified as potentially significant for the distribution and ecology of Tulista species.
- Full Text:
- Date Issued: 2020
Terrestrial alien ferns (Polypodiophyta): a global assessment of traits associated with invasiveness and their distribution and status in South Africa
- Authors: Jones, Emily Joy
- Date: 2019
- Subjects: Biodiversity -- South Africa , Alien plants -- South Africa , Botany -- South Africa , Plant ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39995 , vital:35643
- Description: Globally, invasive alien plants (IAPs) are one of the greatest threats to biodiversity, ecosystems and ecosystem services. The threats posed by IAPs have prompted inventory compilations and screening exercises which aim to understand why some taxa become invasive and others do not. Ferns are a diverse taxon that appear to have a high invasive potential, however ferns have been vastly understudied in the field of invasion biology. This study aimed to establish a basic understanding of terrestrial alien true ferns (Polypodiophyta, hereafter ‘alien ferns’) at both global and national (South African) scales. We developed a global inventory of alien ferns comprising 157 species using published literature and online inventories. Our global inventory indicated that there are significantly more alien fern species than previously estimated (60 species). We used generalised linear models with binomial response variables to determine which traits influenced the probability that an alien fern would become naturalised or invasive. Our models explained 30-40 % of the variance associated with invasiveness and showed that ground-dwelling life forms, reproductive plasticity, tolerance to disturbances and varied light conditions, and a broad introduced range (interpreted as high environmental tolerance and popularity in horticulture) were important determinants of invasiveness in alien ferns. Ultimately, we found that the probability of alien ferns becoming naturalised or invasive is more than 50 %. We further established which geographic regions and fern families had the highest incidences of alien ferns and identified species that were invasive over extensive introduced ranges. For the national scale study, we aimed to assess the distribution, abundance, invasion status, and habitat associations of terrestrial alien fern species present outside of cultivation in South Africa. Field surveys were conducted across the country in habitats suitable for ferns, guided by pre-existing records of alien fern occurrences. Thirteen species occurred outside of cultivation, all of which were classified as invasive, and among these, approximately 5000 plants were recorded across 300 localities. Species richness and abundance peaked along the Indian Ocean Coastal Belt and the Afro-montane phytogeographical regions. A multiple correspondence analysis revealed that alien ferns in South Africa were most strongly associated with indigenous forest habitats and the majority of species selected for shaded conditions, close to water. Only two species were closely associated with open habitats under high light conditions, with plantations also infrequently selected by alien ferns. Habitat generalists were closely associated with disturbance, but avoided open habitats, far from water. Compared to the most prominent angiosperm invaders in South Africa, alien ferns have a lower potential for widespread ii invasion and range expansion, probably due to their habitat specificity. We identified four species as potential targets for eradication and which should be listed as Category 1a under the Alien and Invasive Species regulations of the National Environmental Management: Biodiversity Act of South Africa. The remaining species should be listed as Category 1b since they occupied an extensive geographic range. The most prominent ferns included Adiantum raddianum, Sphaeropteris cooperi, Deparia japonica and Cyrtomium falcatum. Our study informed appropriate regulation for several species of alien ferns that were deemed to be data deficient and in need of assessment by a recent report on the status of biological invasions in South Africa. A risk analysis completed for S. cooperi confirmed that the species has a high invasion risk in South Africa and should be listed as Category 1b. Given that the outcomes of the risk analysis completed for S. cooperi matched the findings from our field surveys, this study supported risk analysis as a reliable (literature-based) method to evaluate IAPs. The findings of our assessments at the global and national scale corresponded in that various traits that promoted invasiveness in alien ferns globally were also facilitating invasion in South Africa. Additionally, of the eleven species found to be invasive over extensive introduced ranges at global scale, only two (Lygodium microphyllum and Angiopteris evecta) were not yet recorded in South Africa. Since horticulture was established as the primary pathway for the introduction of alien ferns, the management of alien ferns (globally and in South Africa) should focus on regulating trade. The sources of cultivation and the pathways of dissemination across the globe also need consideration. Basic environmental and biological associations of alien ferns were evident in this study, but to fully understand their invasive potential further research should focus on niche-based modelling to predict potential invasion ranges, the effects of biological traits on invasiveness, and the potential ecological impacts of these species.
- Full Text:
- Date Issued: 2019
- Authors: Jones, Emily Joy
- Date: 2019
- Subjects: Biodiversity -- South Africa , Alien plants -- South Africa , Botany -- South Africa , Plant ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39995 , vital:35643
- Description: Globally, invasive alien plants (IAPs) are one of the greatest threats to biodiversity, ecosystems and ecosystem services. The threats posed by IAPs have prompted inventory compilations and screening exercises which aim to understand why some taxa become invasive and others do not. Ferns are a diverse taxon that appear to have a high invasive potential, however ferns have been vastly understudied in the field of invasion biology. This study aimed to establish a basic understanding of terrestrial alien true ferns (Polypodiophyta, hereafter ‘alien ferns’) at both global and national (South African) scales. We developed a global inventory of alien ferns comprising 157 species using published literature and online inventories. Our global inventory indicated that there are significantly more alien fern species than previously estimated (60 species). We used generalised linear models with binomial response variables to determine which traits influenced the probability that an alien fern would become naturalised or invasive. Our models explained 30-40 % of the variance associated with invasiveness and showed that ground-dwelling life forms, reproductive plasticity, tolerance to disturbances and varied light conditions, and a broad introduced range (interpreted as high environmental tolerance and popularity in horticulture) were important determinants of invasiveness in alien ferns. Ultimately, we found that the probability of alien ferns becoming naturalised or invasive is more than 50 %. We further established which geographic regions and fern families had the highest incidences of alien ferns and identified species that were invasive over extensive introduced ranges. For the national scale study, we aimed to assess the distribution, abundance, invasion status, and habitat associations of terrestrial alien fern species present outside of cultivation in South Africa. Field surveys were conducted across the country in habitats suitable for ferns, guided by pre-existing records of alien fern occurrences. Thirteen species occurred outside of cultivation, all of which were classified as invasive, and among these, approximately 5000 plants were recorded across 300 localities. Species richness and abundance peaked along the Indian Ocean Coastal Belt and the Afro-montane phytogeographical regions. A multiple correspondence analysis revealed that alien ferns in South Africa were most strongly associated with indigenous forest habitats and the majority of species selected for shaded conditions, close to water. Only two species were closely associated with open habitats under high light conditions, with plantations also infrequently selected by alien ferns. Habitat generalists were closely associated with disturbance, but avoided open habitats, far from water. Compared to the most prominent angiosperm invaders in South Africa, alien ferns have a lower potential for widespread ii invasion and range expansion, probably due to their habitat specificity. We identified four species as potential targets for eradication and which should be listed as Category 1a under the Alien and Invasive Species regulations of the National Environmental Management: Biodiversity Act of South Africa. The remaining species should be listed as Category 1b since they occupied an extensive geographic range. The most prominent ferns included Adiantum raddianum, Sphaeropteris cooperi, Deparia japonica and Cyrtomium falcatum. Our study informed appropriate regulation for several species of alien ferns that were deemed to be data deficient and in need of assessment by a recent report on the status of biological invasions in South Africa. A risk analysis completed for S. cooperi confirmed that the species has a high invasion risk in South Africa and should be listed as Category 1b. Given that the outcomes of the risk analysis completed for S. cooperi matched the findings from our field surveys, this study supported risk analysis as a reliable (literature-based) method to evaluate IAPs. The findings of our assessments at the global and national scale corresponded in that various traits that promoted invasiveness in alien ferns globally were also facilitating invasion in South Africa. Additionally, of the eleven species found to be invasive over extensive introduced ranges at global scale, only two (Lygodium microphyllum and Angiopteris evecta) were not yet recorded in South Africa. Since horticulture was established as the primary pathway for the introduction of alien ferns, the management of alien ferns (globally and in South Africa) should focus on regulating trade. The sources of cultivation and the pathways of dissemination across the globe also need consideration. Basic environmental and biological associations of alien ferns were evident in this study, but to fully understand their invasive potential further research should focus on niche-based modelling to predict potential invasion ranges, the effects of biological traits on invasiveness, and the potential ecological impacts of these species.
- Full Text:
- Date Issued: 2019
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