Evolutionary Distinctiveness and Conservation Prioritization of Nigeria’s Endemic Freshwater Fish Fauna

Nigeria's freshwater fish fauna includes a significant proportion of endemic species, particularly in the Niger Delta tributaries, the Cross River system, and the Lake Chad basin, yet the evolutionary distinctiveness of these endemics and their prioritization within conservation planning frameworks have not been rigorously examined. EDGE of Existence and evolutionary distinctiveness-based prioritization frameworks offer theoretically grounded approaches to identifying species that represent disproportionate shares of evolutionary history. This dissertation conducts a comprehensive evolutionary distinctiveness analysis of Nigeria's endemic freshwater fish fauna, combining original molecular phylogenetics, freshwater ecological assessment, and conservation status modelling. Tissue samples were collected from 58 endemic or near-endemic freshwater fish species across 14 Nigerian river basins during extensive field campaigns in South South, South East, North West, and North Central zones. Multi-locus molecular phylogenies were constructed using Bayesian and maximum likelihood methods, and evolutionary distinctiveness scores were calculated for each species. Conservation status was assessed using IUCN Red List criteria supplemented by systematic threat assessments. Results identify 12 species of extremely high evolutionary distinctiveness and significant threat overlap, warranting Evolutionary Distinct and Globally Endangered classification. The Cross River basin emerges as the highest-priority freshwater conservation unit based on combined evolutionary distinctiveness, endemism, and threat severity. Original contributions include a Nigeria-specific freshwater conservation priority index and the first comprehensive phylogenetic hypothesis for the country's endemic cyprinid fauna. Keywords: evolutionary distinctiveness, endemic freshwater fish, Nigeria, conservation prioritization, molecular phylogenetics