Rudi Mai

Author    Correspondence author
International Journal of Aquaculture, 2025, Vol. 15, No.   
Received: 01 Jan., 1970    Accepted: 01 Jan., 1970    Published: 15 Oct., 2025

Oreochromis spp. (Tilapias) are commercially important fishes with extensive distribution in Africa and other tropical and subtropical regions. Due to morphological similarity, high incidence of hybridization, and complex domestication history, the phylogenetic relationships and taxonomic limits of tilapia species are disputed. In this study, mitochondrial DNA (mtDNA) sequences—COI, CYTB, and D-loop gene fragments—were resolved for some representative Oreochromis species and geographical populations. Phylogenetic trees were reconstructed using Neighbor-Joining (NJ), Maximum Likelihood (ML), and Bayesian Inference (BI) methods to infer evolutionary relationships. The analyses revealed clear genetic differentiation among tilapia species, while some local strains and hybrid populations contained admixed lineages or overlapping taxonomic signals. Genetic distances among populations generally corresponded to geographic separation, suggesting the combined effects of natural selection and human activity on genetic structure. Functional analysis of the variants of mitochondrial genes identified key loci with a putative association with energy metabolism and reproductive adaptation, suggesting their roles in ecological adaptation and phenotypic evolution. The study explains phylogenetic structure among Oreochromis species, verifies the feasibility of mtDNA in species identification, germplasm conservation, and molecular breeding, and provides basic data and theoretical basis for further study on tilapia molecular evolution and environmental adaptation.