Wikipedia
Oreochromis is a large genus of tilapiine cichlids, fishes endemic to Africa and the Middle East. Several species from this genus have been introduced far outside their native range, and are important in aquaculture. Members of this genus, as well as those of the genera Tilapia and Sarotherodon, share the common name " tilapia".
The genus contains more than 30 species, and numerous undescribed forms exist. Judging from mtDNA sequence analysis, several clades seem to exist. In addition, some species (such as Oreochromis urolepis and the blue tilapia O. aureus) seem closer to Sarotherodon according to the mtDNA data. Research is hampered because hybridization runs rampant in these fishes, which confounds mtDNA data (see discussion at Wami tilapia), and the fast speed of evolution makes choice of appropriate nuclear DNA sequences difficult.