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Evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents, with respect to historical urbanization in Gauteng Province, South Africa
Dissertation (MSc (Zoology))--University of Pretoria, 2024.
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University of Pretoria
2024
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| _version_ | 1867613474873409536 |
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| access_status_str | Open Access |
| author2 | Chimimba, Christian Timothy |
| author_browse | Chimimba, Christian Timothy |
| author_facet | Chimimba, Christian Timothy |
| collection | Thesis |
| dc_rights_str_mv | © 2023 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MSc (Zoology))--University of Pretoria, 2024. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/99688 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:36:43.949Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2024 |
| publishDateRange | 2024 |
| publishDateSort | 2024 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/99688 Evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents, with respect to historical urbanization in Gauteng Province, South Africa Chimimba, Christian Timothy u16125119@tuks.co.za Hall, Grant Engelbrecht, Armand UCTD Sustainable Development Goals (SDGs) Invasive species Muridae Urbanization Stable isotope analysis Trophic ecology Dissertation (MSc (Zoology))--University of Pretoria, 2024. Natural history traits such as sex and ontogeny (i.e., age), environmental factors such as season, habitat, and time of sampling, and the nature and extent of urbanization may influence the trophic ecology of rodents. The current study used stable isotope analysis (SIA) of modern and historical samples to: 1) investigate the potential influence of natural history traits and environmental factors that also included metrics of urbanization on carbon (δ13C) and nitrogen (δ15N) isotope ratios in murid rodents from Gauteng Province, South Africa; and 2) evaluate their potential trophic ecological shifts due to urbanization over a historical time scale. SIA was conducted on biologically inert fur samples of modern and historical samples (i.e., museum-preserved samples collected over a time scale) of three invasive (Rattus rattus, R. norvegicus and R. tanezumi) and three indigenous (Aethomys ineptus, Mastomys coucha and Otomys angoniensis) murid rodents. Generalized linear models (GLM), analysis of variance (ANOVA) and Tukey’s post-hoc analyses showed that sex, age, and sampling year had minimal impact on δ13C and δ15N isotope ratios, but not sampling locality and season. These results were supported by the analysis of percentage trophic overlaps based on sample size-corrected standard ellipse areas (SEAc). Collectively, these results suggest that in the last century, short-term seasonal fluctuations accounted for a larger proportion of isotopic variation than long-term environmental changes. The results also showed that qualitative categorical land use data as a proxy for urbanization did not adequately account for changes in rodent isotope ratios. Consequently, an attempt was made to identify quantifiable potential sources of short-term variation in δ13C and δ15N stable isotope ratios in these rodents. The identified quantitative variables included monthly median temperature and monthly total rainfall as short-term metrics of environmental change and Normalized Difference Vegetation Index (NDVI) as a metric for vegetation cover and impervious surface area (ISA), both as proxies for urbanization over a historical time scale. The analyses found that both metrics of short-term environmental factors and proxies of urbanization had no impact on δ13C ratios in any of the three invasive and three indigenous murid rodent species investigated, while δ15N ratios of the insectivorous indigenous A. ineptus and M. coucha were found to be influenced by monthly median temperature and impervious surface area. Overall, the largest %SSQs were due to error (i.e., residual), suggesting that apart from the metrics analysed and the interaction between them, there may be other unexplained components that are also responsible for the variation. These results suggest that the murid rodent populations investigated may be shielded from the negative impacts of short-term environmental factors and urbanization through the availability of excess food resources in one of the most urbanized landscapes in South Africa. This has implications on potential knock-on effects in other aspects of the behaviour and ecology of these rodents that may represent an urgent direction of focus for future research initiatives. These results highlight the potential impact of urban landscapes on the trophic ecology of invasive and indigenous murid rodents and their negative impacts on the conservation of other threatened species within urban settings. South African Department of Science and Innovation-National Research Foundation (DSI-NRF) Centre of Excellence for Invasion Biology (CIB) South African National Research Foundation (NRF) Zoology and Entomology MSc (Zoology) Unrestricted Faculty of Natural and Agricultural Sciences SDG-02: Zero hunger SDG-15: Life on land 2024-11-29T08:22:18Z 2024-11-29T08:22:18Z 2025-04 2024-07 Dissertation * A2025 http://hdl.handle.net/2263/99688 10.25403/UPresearchdata.27928902 en © 2023 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Sustainable Development Goals (SDGs) Invasive species Muridae Urbanization Stable isotope analysis Trophic ecology Evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents, with respect to historical urbanization in Gauteng Province, South Africa |
| title | Evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents, with respect to historical urbanization in Gauteng Province, South Africa |
| title_full | Evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents, with respect to historical urbanization in Gauteng Province, South Africa |
| title_fullStr | Evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents, with respect to historical urbanization in Gauteng Province, South Africa |
| title_full_unstemmed | Evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents, with respect to historical urbanization in Gauteng Province, South Africa |
| title_short | Evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents, with respect to historical urbanization in Gauteng Province, South Africa |
| title_sort | evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents with respect to historical urbanization in gauteng province south africa |
| topic | UCTD Sustainable Development Goals (SDGs) Invasive species Muridae Urbanization Stable isotope analysis Trophic ecology |
| url | http://hdl.handle.net/2263/99688 |