Assessing the role of the Benguela Current as a major biogeographic barrier to marine coastal fishes

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Student thesis: Doctoral ThesisDoctor of Philosophy

Original languageEnglish
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Award date2016
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Abstract

Contemporary biodiversity has been shaped by interactions between intrinsic characters of organisms and extrinsic environmental features that often cannot be reliably predicted. Regions where many species boundaries coincide represent intriguing systems to disentangle factors underpinning eco-evolutionary divergence with relevance to the understanding of how species may respond to climate change. Such regions often harbour complex patterns of inter- and intra-specific biodiversity that are taxonomically challenging. The Benguela cold upwelling system (BCS) has emerged as a major biogeographic barrier promoting and maintaining differences between the Atlantic Ocean and Indo-Pacific Ocean coastal fauna. This research assessed nuclear and mitochondrial DNA variation and applying population genetic and phylogeographic analytical frameworks assessed divergence across the BCS in a number of coastal Sea Bream species (Sparidae). In conjunction with available morphological and ecological data, the results support species level divergence across the BCS in what were previously regarded as conspecific populations in both Spondyliosoma and Diplodus cervinus / hottentotus and direct taxonomic rearrangement. The data also support the potential inadequacy of mtDNA COI barcoding for species discovery in the region due to variable interspecific coalescent depths. Lithognathus mormyrus and Sarpa salpa revealed similar phylogeographic patterns with (1) distinct African and Atlantic / Mediterranean and (2) divergence across the BCS. Phylogenetic analysis supported the
ancestral status of African clades and the potential of an Angolan glacial refuge. A salient feature of the results was the signature of historical and largely asymmetric gene flow across the BCS from South Africa to Angola. This episodic permeability has implications for unexpected species’ responses to climate change which are discussed. Collectively, this study provides new insights into the dynamic role of the BCS in shaping marine biodiversity in both the Atlantic and Indo-Pacific regions

Keywords

  • marine habitats, Benguela Current