Abstract
The headwaters of five large African river basins flow through the Bié Plateau in Angola and still remain faunistically largely unexplored. We investigated fish fauna from the Cuanza and Okavango-Zambezi river systems from central Angola. We reconstructed molecular phylogenies of the most common cichlid species from the region, Tilapia sparrmanii and Serranochromis macrocephalus, using both mitochondrial and nuclear markers. We found evidence for ichthyofaunal contact and gene flow between the Cuanza and Okavango-Zambezi watersheds in the Bié Plateau in central Angola. Waterfalls and rapids also appeared to restrict genetic exchange among populations within the Cuanza basin. Further, we found that the Angolan Serranochromis cichlid fishes represent a monophyletic lineage with respect to other haplochromines, including the serranochromines from the Congo and Zambezi rivers. This study represents an important initial step in a biodiversity survey of this extremely poorly explored region, as well as giving further understanding to species distributions and gene flow both between and within river basins.
Highlights
Natural geographical barriers separating watersheds, such as mountain ranges that divide river basins (‘‘inter-basin barriers’’), dictate the distributions of freshwater organisms
We investigate the biogeographical distribution of two cichlid species, the tilapiine Tilapia sparrmanii, and the serranochromine Serranochromis macrocephalus, focusing within the Bie Plateau in central Angola
The hypothesis of correspondence of the revealed biogeographic pattern to the recent river system separation was rejected since the specimens from the adjacent Cuchi (Okavango) and Cuquema subsystems (Cuanza) represent together one monophyletic lineage in both studied species Serranochromis macrocephalus, and Tilapia sparrmanii (Fig. 2A, B)
Summary
Natural geographical barriers separating watersheds, such as mountain ranges that divide river basins (‘‘inter-basin barriers’’), dictate the distributions of freshwater organisms. Barriers within the rivers, such as waterfalls and rapids zones can influence species distribution patterns (‘‘intra-basin barriers’’) [1,2,3]. Such barriers can limit the gene flow and even initiate speciation [4,5,6,7]. In conjunction with inter- and intra-basin barriers, geological history can strongly impact distribution patterns of freshwater ichthyofauna. African rivers are generally characterized by high frequencies of rapids and waterfalls, when compared to the rest of the world’s rivers [10]
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