M.Sc. (Zoology) / Spiders of the genus Cyrtophora Simon, 1864 are commonly called tropical tent‒web spiders due to the unique shape of their webs. Forty three Cyrtophora species are known throughout the world and five of them have been recorded from Africa, but none formally from South Africa (SA). The only species of Cyrtophora so far suspected to occur in SA is the cosmopolitan species C. citricola (Forsskål, 1775). The South African Cyrtophora species show extensive morphologic variation, especially in colouration and abdominal characteristics. In SA they frequently make their webs in aloes and cycads and live solitary or in small to large aggregations. This social behaviour offers many advantages but also subjects the community to threats such as birds. A behavioural trait that is fairly uncommon in spiders, but is exhibited by Cyrtophora, is that the webs are only repaired when small holes, due to prey capture, are made; new webs are only built above the old webs in cases where extensive damage occurs. Morphologically, sexual dimorphism is prevalent, and juveniles vary greatly from adults. This causes several problems for traditional taxonomy. Both males and females have the ability to alter the degree of colour in the abdomen in response to the environment. This is usually a defence mechanism and is used for camouflage. DNA barcoding of the mitochondrial cytochrome c oxidase 1 (CO1) gene was done on fresh and museum specimens sampled from 2006‒2011. Barcoding of the nuclear histone H3 gene was done on some of the male and female specimens for use as a comparison. Analysis was done using the SPIDER programme. Morphological analysis of the genitalia was used to compare the species determined by the genetic results. Abdomen traits were observed to determine morphologic variation between and within species. General behaviour was recorded through observation of a study site and photographs previously taken around SA, noting specifically reproduction, prey capture, colour change and other general behavioural characteristics. Ecological patterns such as seasonality (phenology) and distribution patterns were recorded using collection data from museum and freshly collected specimens. Genetic results of the H3 gene indicate three species whereas the CO1 gene indicates 10 species. Both genes were concordant regarding two species, one of which was a specimen from Madagascar (and as this is a study on South African species was therefore not included in morphological analysis). A combined analysis of both gene datasets indicated three species. However, the CO1 gene had strong support but the H3 gene had poor resolution. For this reason the H3 gene was not recommended for analysis of Cyrtophora. Morphologically, the specimens showed diverse abdominal variation but genitalia assessment determined the presence of only two species. The two species indicated by genetics and morphology combined were C. citricola and an unidentified species from Malelane, Mpumalanga. In conclusion, it is evident that C. citricola is not the only species under this genus in SA. Even though morphology indicates only two species, the CO1 gene indicates a minimum of eight species, possibly 10. Comprehensive morphological and ecological study could show characteristics that correspond with the genetic results. This information will help to aid future biodiversity assessments and conservation programmes. The behavioural information obtained may also help initiatives such as the South African National Survey of Arachnida (SANSA) and red list authorities. The effectiveness of the CO1 gene for identification of this species will also help initiatives
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:7688 |
| Date | 24 July 2013 |
| Creators | Franzini, Philippa Zena Nel |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
Page generated in 0.0082 seconds