Macroevolutionary Patterns and Diversification Rates in West African Cichlid Fishes: A Phylogenomic Investigation

West African cichlid fishes exhibit remarkable ecological diversity across river systems and represent an underexplored model system for investigating macroevolutionary drivers of adaptive radiation in riverine ecosystems. This research investigates the macroevolutionary patterns, diversification rates, and ecological speciation processes in West African cichlids with particular emphasis on river systems connected to the Benue-Niger drainage of Nigeria. Whole-genome sequencing was performed on 240 individuals representing 60 cichlid species sampled from the River Niger, Benue, Cross, and Volta basins. Phylogenomic analysis was conducted using maximum likelihood and Bayesian inference on a 12,000-gene supermatrix. Diversification rate analysis employed BAMM and BiSSE models to test for rate heterogeneity and the association of ecological traits with speciation rates. Ancestral trait reconstruction was performed for trophic morphology, colour pattern, and depth preference. The resolved phylogeny recovered four major West African cichlid radiations, with the Benue-Niger system supporting the most recent rapid diversification event dated to 2.1 to 3.8 million years ago using fossil-calibrated molecular clocks. Diversification rate analysis identified a significant acceleration in speciation coinciding with Pleistocene climate cycling and drainage capture events between the Niger and Benue systems. Trophic niche breadth was negatively correlated with net diversification rate, supporting ecological specialisation as a driver of speciation. Convergent evolution of benthic-feeding morphotypes was documented in three independent lineages across different drainage basins. Gene flow analysis revealed recent secondary contact zones producing hybridisation in the Benue-Niger confluence. This research makes original theoretical contributions to the ecology and evolution of adaptive radiation in tropical riverine fishes. Keywords: cichlid diversification, phylogenomics, West Africa, adaptive radiation, macroevolution.