Impacts of Quaternary Climatic Changes on the Diversification of Riverine Cichlids in the Lower Congo River.

This article investigates the influence of Quaternary paleoclimatic changes on the diversification and gene flow of endemic lamprologine cichlid fishes in the lower Congo River, a region noted for its hydrological complexity and high fish endemism. Using genome-wide SNP data and demographic modeling based on reduced representation sequencing (2RADseq), the study estimates that these cichlids diverged primarily during the Early-Middle Pleistocene transition (approximately 0.6–1.0 million years ago), a period marked by intensified glacial–interglacial cycles and associated fluctuations in river discharge. Gene flow analyses reveal temporally constrained pulses of migration between populations and species, often correlating with interglacial periods of higher river discharge, supporting the hypothesis that climatic-driven hydrological changes shaped evolutionary processes in this riverine system. The findings highlight the synergistic roles of paleoclimate, river hydrology, and geomorphology in generating the lower Congo River’s hyper-diverse fish assemblages and underscore the importance of understanding historical climate impacts to anticipate future biodiversity responses amid ongoing climate change.