Genetic diversity patterns and species differentiation among three tilapia species from Nigeria based on the mitochondrial D-loop and morphological markers

Abstract

Tilapia are vital aquaculture species with great potential for enhancing food security in Nigeria. This study investigated the genetic diversity and species differentiation of three tilapia species (Oreochromis niloticus, Oreochromis aureus and Oreochromis mossambicus) from five rivers in the South-South geopolitical zone of Nigeria, between 5 May and 9 August 2022. Mitochondrial D-loop sequencing was used to assess genetic variation, along with morphological and meristic analyses. Major water physico-chemical parameters, including pH, conductivity, total dissolved solids and temperature, were also measured to evaluate their impact on fish performance. The results revealed robust genetic diversity, with nucleotide and haplotype diversities averaging 0.162 ± 0.005 and 0.931 ± 0.008, respectively, and O. niloticus showing the highest haplotype diversity (0.982 ± 0.010). Significant genetic differentiation among species was confirmed, with a fixation index ranging from 0.550 to 0.738. Morphological assessment showed significant variations, particularly favouring O. niloticus. Water quality was strongly correlated with growth performance, with lower total dissolved solids and conductivity supporting growth. This research demonstrates the importance of integrating molecular, morphological and environmental data for effective tilapia breeding programmes, suggesting that proper management of water quality and genetic resources can enhance aquaculture practices and contribute to food security in Nigeria.