Electrophoretic identification and phylogenetic relationships of indigenous tilapiine species of Zimbabwe

In order to characterize Zimbabwean tilapias 34 populations of seven species, two in the genus Tilapia and five in Oreochromis , were analysed using horizontal starch gel electrophoresis. Twenty-seven loci were polymorphic while five were monomorphic but had fixed allelic differences among some species and six were monomorphic for the same allele in all species. No fixed allelic differences were found between O. mossambicus and O.mortimeri , and only one locus distinguished O. andersonii from O. mossambicus and O. mortimeri . Pairwise comparisons of O. mossambicus or O. mortimeri populations of genetic distances frequently showed a greater degree of difference within the species than was evident in some O. mossambicus O. mortimeri pairs. This study failed to distinguish O. mortimeri as a distinct species from O. mossambicus . The Tilapia species formed distinct clusters from Oreochromis in both consensus eighbourjoining and distance Wagner topologies. Oreochromis ossambicus, O. mortimeri and O. andersonii clustered together consistently. Although some differences from the taxonomic arrangement of Trewavas are discussed, the principal relationships revealed in our analysis are consistent with most recent studies.