Genetic variation and lack of hybridization in five cichlid fish species in the Malagarasi River basin, Tanzania

Among the most widely cultured groups of freshwater fish species are tilapiine cichlids. This has contributed to introduction of cichlid fish species in area where they were not native. Consequently, has contributed to negative ecological effects on local species and their habitats through competition, habitat alteration and loss of unique population genetic structures due to hybridization. This research study aimed to assess the genetic status of five cichlid fish species red listed by the International Union for Conservation of Nature (IUCN) as least concerned species. A mitochondrial Cytochrome Oxidase Subunit I (COI) gene fragment from 112 individuals collected from three sampling sites were used to determine the present genetic diversity of the cichlid species inhabit the Malagarasi River system which discharge water into Lake Tanganyika. The highest nucleotide diversity (0.02 ± 0.01) and haplotype diversity (0.94 ± 0.04) were recorded from Haplochromis pharyngalis. The lowest levels of nucleotide and haplotype diversity were recorded from Oreochromis leucostictus. The Analysis of Molecular Variance (AMOVA) resulted into statistically significant genetic differences (Φst: 0.96, P < 0.001) among the cichlid species studied. The minimum spanning haplotype network and maximum-likelihood phylogenetic analyses support the AMOVA findings as no species is sharing any haplotype with other species. The values of neutrality tests suggested that the studied cichlid fish species are stable and not expanding. These findings highlight the necessity of conservation interventions in the area especially for the species which displayed low nucleotide and haplotype diversity.