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Conservation of melanistic girdled lizards in the Saldanha area and reference to background colour-matching and sexual dimorphism
Thesis (M. Sc.) -- University of Stellenbosch, 1995.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613891266084864 |
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| access_status_str | Open Access |
| author | Cordes, Imke Gesa |
| author2 | Mouton, P. le F. N. |
| author_browse | Cordes, Imke Gesa Mouton, P. le F. N. |
| author_facet | Mouton, P. le F. N. Cordes, Imke Gesa |
| author_sort | Cordes, Imke Gesa |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (M. Sc.) -- University of Stellenbosch, 1995. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/58651 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:20.403Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/58651 Conservation of melanistic girdled lizards in the Saldanha area and reference to background colour-matching and sexual dimorphism Cordes, Imke Gesa Mouton, P. le F. N. Van Wyk, J. H. Stellenbosch University. Faculty of Science. Dept. of Botany & Zoology. Lizards -- South Africa -- Saldanha Bay Region Lizards -- Color Wildlife conservation -- South Africa -- Saldanha Bay Region Melanism Sexual behavior in animals Sexual selection in animals Saldanha Bay (South Africa) -- Environmental conditions Dissertations -- Zoology Thesis (M. Sc.) -- University of Stellenbosch, 1995. The conservation status of the Saldanha-Langebaan lizard fauna, which is presently under pressure through urban development, was assessed. Relict melanistic populations of two gjrdled lizard species, C. niger and c. polyzonus, and a contact zone between C. niger and a closely related, nonmelanistic species, c. cordylus, occur here. Owing to the importance of these elements for studies of evolutionary biology, they need to be conserved. The investigation revealed that a melanistic population of a third species, Acontias m. meleagris, may also be a relict. The exact boundaries of the C. niger and C. polyzonus ranges were established. Three isolated c. niger populations occur in the Saldanha-Langebaan area and are restricted to rocky habitat in the cool coastal belt. The range of the melanistic form of c. polyzonus roughly corresponds with that of c. niger, but extends further inland where temperatures are higher. No additional zones of contact between c. niger and C. cordylus were identified. At Mauritz Bay, their ranges overlap up to 70 m wide along a zone of 220-240 m. The contact zone and the c. niger populations have not been directly affected by urban development at present, but are under pressure through new developments in the area. State-owned areas, which are presently fairly undisturbed, should be conserved, and the public should be made aware of the unique lizard fauna. The cryptic significance of melanism in two Cordylus species was evaluated by comparing melanistic forms with closely related, non-melanistic forms. A simple photographic technique, measuring colour density, was used for non-invasive colour quantification. The difference between the colour density of the lizard and the substrate was used as an indication of background colour-matching. It was found that the non-melanistic populations show a significantly higher degree of colour-matching than the melanistic populations. The primary function of melanism is therefore not a cryptic one, but probably thermoreregulatory. It is suggested that black body colour may not be disadvantageous in the avoidance of predators, as it may blend in well with shadows in the background when seen from a distance. Differences in sexual dimorphism caused by sexual selection between the cold-adapted, melanistic C. niger and the warm-adapted, non-melanistic C. cordylus were investigated. Samples of both species were collected in the cool Saldanha Bay area, and one sample of c. cordylus in the more temperate Gansbaai area. Both species display sexual dimorphism, but in different characters: c. niger in mean body size and head length, and c. cordylus in head width, head length and number of epidermal glands. The difference in sexual dimorphism is most probably owing to different evolutionary histories of the species. No geographical variation in sexual dimorphism was observed in c. cordylus. Individuals are, however, smaller in the Saldanha area than at Gansbaai. It is suggested that sexual dimorphism in both species is mainly the result of differential energy allocation by females, and not of sexual selection. Masters 2012-08-27T11:39:04Z 2012-08-27T11:39:04Z 1995 Thesis http://hdl.handle.net/10019.1/58651 en Stellenbosch University 147 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Lizards -- South Africa -- Saldanha Bay Region Lizards -- Color Wildlife conservation -- South Africa -- Saldanha Bay Region Melanism Sexual behavior in animals Sexual selection in animals Saldanha Bay (South Africa) -- Environmental conditions Dissertations -- Zoology Cordes, Imke Gesa Conservation of melanistic girdled lizards in the Saldanha area and reference to background colour-matching and sexual dimorphism |
| title | Conservation of melanistic girdled lizards in the Saldanha area and reference to background colour-matching and sexual dimorphism |
| title_full | Conservation of melanistic girdled lizards in the Saldanha area and reference to background colour-matching and sexual dimorphism |
| title_fullStr | Conservation of melanistic girdled lizards in the Saldanha area and reference to background colour-matching and sexual dimorphism |
| title_full_unstemmed | Conservation of melanistic girdled lizards in the Saldanha area and reference to background colour-matching and sexual dimorphism |
| title_short | Conservation of melanistic girdled lizards in the Saldanha area and reference to background colour-matching and sexual dimorphism |
| title_sort | conservation of melanistic girdled lizards in the saldanha area and reference to background colour matching and sexual dimorphism |
| topic | Lizards -- South Africa -- Saldanha Bay Region Lizards -- Color Wildlife conservation -- South Africa -- Saldanha Bay Region Melanism Sexual behavior in animals Sexual selection in animals Saldanha Bay (South Africa) -- Environmental conditions Dissertations -- Zoology |
| url | http://hdl.handle.net/10019.1/58651 |
| work_keys_str_mv | AT cordesimkegesa conservationofmelanisticgirdledlizardsinthesaldanhaareaandreferencetobackgroundcolourmatchingandsexualdimorphism |