" More than 40 years ago in their compendium of fish diversity in the lower Congo River (LCR), T. R. Roberts and D. J. Stewart posed the question, “Why does the LCR harbor so many cichlids?” Here we seek an answer through a synthesis of the last 40+ years of research on cichlid diversity, ecology, and speciation. Our review suggests a key role for the unique geomorphology and hydrology of the river itself and its history of connectivity to other African freshwater ecosystems. In contrast to the river upstream of Pool Malebo, the LCR channel is entirely bedrock, and littoral habitats are mostly rocky and rock-strewn. In situ measurements have recorded dramatic changes in channel topology, fluctuating bed bathymetry, and regions of extreme depth. A combination of high annual discharge, steep elevational decline, and fluctuating channel width and depth result in extraordinarily high-energy flow regimes throughout the LCR. In-stream hydraulics and bathymetry appear to play a key role in isolating cichlid populations and are likely powerful drivers for micro-allopatric isolation and speciation, often over remarkably small geographical scales. Moreover, this hydrologically extreme environment is the evolutionary backdrop for an unusual array of cichlid morphologies, including the only known blind cichlid (Lamprologus lethops) "
Classification: Ecology and environment, West Africa.
Stiassny, Melanie & S.E. Alter. 2021. "Evolution in the Fast Lane: Diversity, Ecology, and Speciation of Cichlids in the Lower Congo River". The Behavior, Ecology and Evolution of Cichlid Fishes. Abate, M.E., Noakes, D.L.G. (Editors.). pp. 107-133. DOI: 10.1007/978-94-024-2080-7_4 (crc11689) (abstract)