Abstract
Aim African freshwater fishes serve as important biogeographical indicators of geomorphological and hydrological history across the continent. However, research focusing on the phylogeny, biogeography and diversification of African fishes, particularly in central Africa, is relatively scarce. Here, we evaluate three geological hypotheses regarding the formation of the contemporary Congo basin: (1) the dominance of the Ogooué and Kouilou rivers along the western continental margin during the Cretaceous, (2) an eastward‐flowing Congo‐Zambezian system forming the Rufiji Delta during the Paleogene and (3) river basin capture resulting in the formation of the Lower Congo River during the Pliocene. To do this, we reconstructed the phylogeny of featherfin tetras of the genus Bryconaethiops using their mitochondrial genomes, estimated diversification chronology, and detected biogeographic transitions in Central Africa. Location Afrotropical rivers of Nilo‐Sudan, Lower Guinea, Congo and Malagarasi‐Tanganyika. Time Period Oligocene, Neogene and Quaternary. Taxon Bryconaethiops (Teleostei: Characiformes: Alestidae). Methods Analysis of a molecular matrix of complete mitochondrial genomes comprising 13 protein‐coding genes totaling 14,869 bp for 36 Bryconaethiops and related alestid taxa. Phylogenetic analyses included maximum likelihood, Bayesian fossil calibration, and parametric biogeographic reconstructions. Support for generic monophyly was evaluated using internal and external anatomy with microcomputed tomography (μCT) and conventional morphometric/meristic analyses. Data from museum specimens provided updated distributional ranges for each Bryconaethiops species. Results Time‐calibrated phylogenetic and biogeographic analyses suggest initial diversification of Bryconaethiops occurred in Lower Guinea during the Oligocene ( ca. 25 Ma), followed by transitions to the Nilo‐Sudan and Middle Congo regions during the Early Miocene ( ca. 19–17 Ma). Three distinct Pleistocene dispersal events to the Lower Congo ( ca. 0.7–0.05 Ma) and three to the Upper Congo and Malagarasi of Tanganyika ( ca. 1.5–0.1 Ma) were detected. Morphological analysis reveals four generic synapomorphies associated with modification of the upper and lower jaws, dentition and elongation of dorsal‐fin lepidotrichia, in addition to evidence for revalidation of B. mocquardianus (Thominot, 1886) from Atlantic coastal rivers of the eastern Gulf of Guinea. Main Conclusions Genetic and biogeographical analysis of Bryconaethiops supports the hypothesis that an expansive, centrally situated lowland proto‐Congo was captured by the modern Lower Congo during the Plio‐Pleistocene. Sympatric occurrences of sister taxa point to a complex scenario of allopatric speciation followed by secondary contact and/or resource partitioning across the Congo basin.