- Title
- Assessing the invasive status of the Oenothera species (evening primroses) in South Africa
- Creator
- Scott, Zimbini
- Subject
- Evening primrose
- Subject
- Invasive plants -- Biological control -- South Africa
- Subject
- Ecological assessment (Biology)
- Date
- 2023-10
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10353/28414
- Identifier
- vital:74321
- Description
- Oenothera species (Myrtales: Onagraceae), commonly known as evening primroses, were introduced to South Africa for various purposes, where they established alien populations and expanded their distribution nationwide. Although some of these species are listed as emerging invaders in South Africa, their invasive status is currently unclear. This study assessed the invasive status of eight Oenothera species listed as emerging invaders in South Africa, namely, O. biennis, O. glazioviana, O. laciniata, O. indecora, O. stricta, O. jamesii and O. rosea. The study also focused on the biotic interactions of Oenothera with native arthropod species to assess any potential ecological impacts. The distribution of the eight Oenothera species was mapped using available occurrence records from sources such as the SAPIA database, herbarium records, and BRAHMS database. Additional records were collected by conducting field surveys in KwaZulu- Natal and Eastern Cape provinces. The distribution of these species was mapped using QGIS. Most Oenothera species were found in the Eastern Cape, KwaZulu-Natal, Gauteng, Free State, Mpumalanga and Western Cape provinces, while North-West, Northern Cape, and Limpopo provinces had fewer species. The grassland, savanna and fynbos biomes had more Oenothera species than other biomes in South Africa. The results indicated that O. biennis, O. glaziviana, and O. rosea are spreading at a preceding rate. In South Africa, the species flower predominantly in the spring and summer seasons. Species distribution modelling was conducted using Maxent to identify climatically suitable areas for establishing evening primrose populations. Species distribution models results show that the climatically suitable areas are concentrated in the central, eastern, and south-western regions of South Africa. The most considerable climatic variables contributing to the distribution of most Oenothera species were the annual mean temperature and precipitation during the driest month. To evaluate biotic interactions between native arthropods and Oenothera species and assess the potential ecological impacts, arthropods were collected from two Oenothera species (O. biennis and O. glazioviana) in different localities (only in Eastern Cape: East London and Fort Beaufort). The arthropods collected were identified, and diversity indices were calculated to determine the diversity of native arthropods collected in sites where these species are present. The overall number of individual arthropods collected was 768, belonging to six orders. These arthropod species belong to three feeding guilds: herbivores, predators, and palynivores. The ANOVA results showed that these species statistically differ in diversity for all the diversity indices. Overall, there were significant interactions between the arthropods’ orders and their feeding guilds. Lastly, the risk analysis framework assessed the potential for managing and listing two species (O. biennis and O. rosea) in the NEM: BA A&IS list. After considering all the likelihood elements, environmental, socioeconomic, and potential impacts, the risks posed by Oenothera biennis in South Africa were found to be high. The recommendation of this analysis suggests that O. biennis and O. rosea species be listed as category 1b in the NEMBA A & IS regulations list. The results of this study indicate that these congeners experience ecological differences, resulting in their varied distribution and invasion. Furthermore, they offer new insights regarding the geographical patterns and potential distribution of Oenothera species in South Africa. Moreover, it also provides recommendations for the management of the species in the South African context.
- Description
- Thesis (MSc) -- Faculty of Science and Agriculture, 2023
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (XVI, 195 leaves)
- Format
- Publisher
- University of Fort Hare
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- University of Fort Hare
- Rights
- All Rights Reserved
- Rights
- Open Access
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UFH Department of Zoology & Entomology
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Z Scott Final Thesis_corrected signed.pdf | 68 MB | Adobe Acrobat PDF | View Details Download |