A central concept in evolutionary biology is to understand how new species arise and are maintained. Studying the temporal and spatial distribution of genealogical lineages provides insight into evolutionary processes which govern diversification while the study of disease vectors has additional implications for human health. Within Africa, medically important Aedes mosquitoes provide an interesting case in which to study evolutionary processes because they are behaviourally and morphologically diverse. These mosquitoes are also inherently dependent of forests and so provide an ideal study organism in which to test the refuge hypothesis of historical climate change, which has been suggested as a pivotal force in species evolution. Before their evolutionary history can be determined, reliable identification of target species is required. In Chapter 3, we have developed a PCR mediated method to distinguish between isomorphic species of the Simpsoni Complex and use this method to provide inferences on ecology and species distributions; findings reveal an east-west difference in the distribution of the yellow fever vector Ae. bromeliae and non-vector Ae. lilii across the African continent, while these species meet in Uganda where they use the same larval habitats. In Chapters 4 and 5 we use a standard phylogeographic approach coupled with Approximate Bayesian Computation to uncover the evolutionary history of Aedes mosquitoes. Analysis reveals common phylogeographic signals within Aedes species which show populations have been subject to historical lineage diversification, admixture and recent demographic structure, in accordance with the refuge hypothesis of climate induced vicariance and secondary contact. Findings suggest that recent climate change throughout the late Pleistocene and early Holocene was important in generating African biodiversity. We find additional differences in the population structure of species between East and West Africa which could reflect more general biodiversity patterns within Africa. As the region connecting East and West African populations, Central Africa could be an important area regarding the diversification of species, including diseases and their vectors. We have identified a putative role for ecological speciation; for example in Chapter 4 we have provided additional evidence that worldwide populations of Ae. aegypti stem from a particularly successful source, indicating these mosquitoes possessed a trait integral for range expansion. In Chapters 4 and 5 we find that historical admixture within Africa characterises populations of Aedes mosquitoes and so may have played a key role in their evolutionary success. Since admixture can combine novel combinations of genetic material and raise adaptive potential, admixture may have been selectively advantageous for Aedes mosquitoes. Similarly, climate related secondary contact is likely to have been an important force for the evolution of other forest dependent species within Africa.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:764399 |
| Date | January 2015 |
| Creators | Bennett, Kelly |
| Contributors | Walton, Catherine ; Robertson, David |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/evolutionary-processes-generating-african-biodiversity-a-case-study-on-aedes-mosquitoes(155ae971-cb53-45fc-81f4-50a4db4fe46c).html |
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