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Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift?
Aloidendron dichotomum is predicted to undergo a south and south-eastern range shift in response to anthropogenic climate warming. Despite this, its range is suggested to be limited by low temperature extremes at the cool range edge and no such range shift has yet been confirmed. However, eco-physio...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2020
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| _version_ | 1867613344243908608 |
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| access_status_str | Open Access |
| author | Grey, Kerry-Anne |
| author2 | Cunningham, Susan |
| author_browse | Cunningham, Susan Grey, Kerry-Anne |
| author_facet | Cunningham, Susan Grey, Kerry-Anne |
| author_sort | Grey, Kerry-Anne |
| collection | Thesis |
| description | Aloidendron dichotomum is predicted to undergo a south and south-eastern range shift in response to anthropogenic climate warming. Despite this, its range is suggested to be limited by low temperature extremes at the cool range edge and no such range shift has yet been confirmed. However, eco-physiological knowledge necessary to predict and detect this range shift is lacking. This study aimed to determine whether physiological performance of A. dichotomum differs at a regional and local scale, and if so, whether regional and local temperatures explain physiological differences. Performance metrics and temperature data were collected during summer at 14 microsites in two sites at the cool range edge of A. dichotomum. Microsites were stratified by aspect and elevation. This study confirmed that A. dichotomum is performing CAM photosynthesis at its cool range edge. Further, the results provide evidence for the temperature dependence of A. dichotomum’s physiological performance. Higher performance was associated with warmer nights and the warmer north facing slopes. This is in keeping with our hypothesis that A. dichotomum individuals at the cool range edge would take advantage of higher temperatures more typical of their core range areas. Opposing this, higher carbon gain was found at Gannabos - the cooler of the two study sites. This may be due to the less variable rainfall pattern at Gannabos. Furthermore, performance was higher on the flats where temperatures were also cooler. This may be due to lower water runoff on the flats compared to the slopes. As a result, I suggest that the cool range edge of A. dichotomum is limited both by low temperatures and rainfall variability and that, with warming, constraints on these populations are being removed. This is substantiated by the observed high levels of juvenile recruitment in these populations relative to others, and in time, is likely to lead to range expansion in the region. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/31142 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:34:39.078Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2020 |
| publishDateRange | 2020 |
| publishDateSort | 2020 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/31142 Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift? Grey, Kerry-Anne Cunningham, Susan Midgley, Guy Foden, Wendy biological sciences Aloidendron dichotomum is predicted to undergo a south and south-eastern range shift in response to anthropogenic climate warming. Despite this, its range is suggested to be limited by low temperature extremes at the cool range edge and no such range shift has yet been confirmed. However, eco-physiological knowledge necessary to predict and detect this range shift is lacking. This study aimed to determine whether physiological performance of A. dichotomum differs at a regional and local scale, and if so, whether regional and local temperatures explain physiological differences. Performance metrics and temperature data were collected during summer at 14 microsites in two sites at the cool range edge of A. dichotomum. Microsites were stratified by aspect and elevation. This study confirmed that A. dichotomum is performing CAM photosynthesis at its cool range edge. Further, the results provide evidence for the temperature dependence of A. dichotomum’s physiological performance. Higher performance was associated with warmer nights and the warmer north facing slopes. This is in keeping with our hypothesis that A. dichotomum individuals at the cool range edge would take advantage of higher temperatures more typical of their core range areas. Opposing this, higher carbon gain was found at Gannabos - the cooler of the two study sites. This may be due to the less variable rainfall pattern at Gannabos. Furthermore, performance was higher on the flats where temperatures were also cooler. This may be due to lower water runoff on the flats compared to the slopes. As a result, I suggest that the cool range edge of A. dichotomum is limited both by low temperatures and rainfall variability and that, with warming, constraints on these populations are being removed. This is substantiated by the observed high levels of juvenile recruitment in these populations relative to others, and in time, is likely to lead to range expansion in the region. 2020-02-18T08:37:00Z 2020-02-18T08:37:00Z 2019 2020-02-18T08:11:00Z Master Thesis Masters MSc http://hdl.handle.net/11427/31142 eng application/pdf Department of Biological Sciences Faculty of Science |
| spellingShingle | biological sciences Grey, Kerry-Anne Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift? |
| thesis_degree_str | Master's |
| title | Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift? |
| title_full | Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift? |
| title_fullStr | Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift? |
| title_full_unstemmed | Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift? |
| title_short | Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift? |
| title_sort | are local range expansions in southerly populations of aloidendron dichotomum early indicators of a future range shift |
| topic | biological sciences |
| url | http://hdl.handle.net/11427/31142 |
| work_keys_str_mv | AT greykerryanne arelocalrangeexpansionsinsoutherlypopulationsofaloidendrondichotomumearlyindicatorsofafuturerangeshift |