Phylogenetic differentiation of wild and cultured Nile tilapia (Oreochromis niloticus) populations based on phenotype and genotype analysis

Abstract

Variation in phenotype based on morphometric character indices and meristic counts and in genotype based on random amplified polymorphic DNA (RAPD) fingerprinting among different wild and cultured Nile tilapia (Oreochromis niloticus) populations were analyzed phylogenetically to study and compare the amount of differences in phenotype with the amount of differences in genotype and to help assess the degree of phenotypic plasticity shown by these populations. The results revealed that there were significant differences (P≤0.05) in most of morphometric character indices and meristic counts among different wild and cultured Nile tilapia populations tested. Data of genetic similarity coefficients among four populations of Nile tilapia based on RAPD data of all primers used, showed the highest interpopulation genetic similarity (64%) exhibited between Manzalah and Edku Lake populations, while the lowest genetic similarity (37%) was recorded between Manzalah Lake and cultured populations. The hierarchical cluster analysis based on each phenotype and genotype analysis grouped the four populations into two major category groups: Edku Lake, Manzalah Lake and Nile river populations group and cultured population group. Within these major grouping, wild Nile tilapia were grouped close together. Also, Edku Lake population appears to be more similar to that of Manzalah Lake population than that of Nile river population. Moreover, the great concordance between each phylogeny based on phenotype and genotype analysis revealed that the phenotypic plasticity may not be found in the different Nile tilapia populations tested and the relationship among them considered as intraspecific.