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The human-mediated transfers of tilapia for aquaculture as a panacea for food insecurity in Africa have led to unprecedented and irreversible impacts on native ichthyofaunal biodiversity. Though aquaculture has been pointed to as the main gateway to species introductions in the Pangani system, formal documentation on how it has contributed to such colonization is anecdotal. The present study aimed to genetically identify, update the list of introduced tilapia taxa, and authenticate if aquaculture is the main gateway to their widespread. We genetically identified non-native tilapias from the Pangani Catchment and aquaculture facilities by genotyping partial Mitochondrial DNA Control region. Molecular analyses depicted the Pangani Catchment to be exclusively inhabited by six non-native tilapiine taxa, particularly Oreochromis niloticus, Oreochromis leucostictus, Coptodon rendalli, Oreochromis esculentus, Oreochromis spilurus, and Oreochromis urolepis hornorum. Oreochromis niloticus, O. leucostictus, and C. rendalli were also predominant in aquaculture and shared haplotypes with their counterparts from the Pangani Catchment. We identified commercial strains of O. niloticus that also shared haplotypes between the two systems. Such haplotype sharing proves aquaculture is the gateway to introducing non-native tilapias into the Pangani Catchment. Thus, fish farming in the region should adhere to regional and international legislation to prevent future spillage. [ABSTRACT FROM AUTHOR]

Available ecological information, an extensive distributional range, conflicting osteological data, and a proposed early Miocene origin provide the impetus for the present study which investigates genetic structuring, biogeographic, and phylogenetic relationships within the Aplocheilichthys spilauchen lineage. Through the analysis of the mitochondrial gene COI, species delimitation methods (ABGD, GB, GMYC, bPTP) were applied, recognizing 6–7 OTUs with absolute pairwise genetic distances ranging between 8 and 22%. The onset of diversification is estimated to be within the middle Miocene and both dispersal and vicariance-shaped A. spilauchen diversity and distribution, as suggested by time-calibrated and ancestral range reconstruction (S-DIVA) analyses. We report for the first time, a pattern of diversification within a lineage of brackish water fish that is concordant with the historical distribution of coastal mangroves forests, shaped by a series of historical events that likely affected forest cover since the middle Miocene (e.g. major climate shifts and sea-level fluctuations, onset of the modern Congo River outlet, increased volcanism in the Cameroon Volcanic Line). [ABSTRACT FROM AUTHOR]