Patterns and Processes of Divergence in African Marine SystemsImplications for Conservation and Management

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Student thesis: Doctoral ThesisDoctor of Philosophy

Original languageEnglish
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Award date2019
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Abstract

Through investigating the spatial distribution of genetic diversity and phylogeographic partitioning, this thesis aimed to assess the roles of ecological, environmental and climatic factors in shaping microevolution, adaptation and speciation in a number of marine taxa distributed across the African coastline, with a particular focus on the eastern Atlantic and the South West Indian Ocean (SWIO). Data for a number of taxa (Chapter 2.2, 2.3, 3.2) adds to evidence that the Benguela Upwelling System (BUS) represents a long standing biogeographic boundary that has fundamentally shaped divergence between Atlantic and Indian Ocean gene pools. However, evidence of historical permeability permitting historical gene flow events from South Africa into southern Angola, was reported for several species (Chapter 2.3, 3.2). Most strikingly among Sepia species (Chapter 2.3) this permeability has facilitated complete species hybridisation in Angolan waters. The data also revealed the novel genetic composition for many fish groups along the west and north African coasts and in doing so highlights this area as a biodiversity blind spot and suture zone for divergent genetic
lineages (Chapter 4). In contrast to the eastern Atlantic the SWIO was shown to be a high gene flow region, with a number of fish exhibiting high connectivity throughout the region (Chapter 5.1, 5.2), superimposed upon which was a pattern of chaotic genetic patchiness due to stochastic recruitment heterogeneity. Phylogenetic analysis also revealed that two commercially important and hitherto considered distinctive Lethrinus species in the SWIO each comprised two cryptic species (Chapter 5.1, 5.2). From an evo-to-eco perspective the research provides evidence of non-neutral evolution of mitochondrial DNA in Sepia species (Chapter 2.3) and unusually slow mutation
rates in horse mackerel (Chapter 4). By resolving patterns and processes from an ecological to evolutionary perspective this research also provides resources and information pertinent to the management and future study of marine biodiversity in both understudied regions.