Phylogenetic Relationships of Turbot Species (Scophthalmidae) Inferred from the Mitochondrial COIII Gene and Morphological Characters

In this study, the validity, distribution and structure of three turbot species, Scophthalmus maeoticus, S. maximus, S. rhombus, belong to Scophthalmidae family in Turkish, Bulgarian and Russian coastal waters were determined with mtDNA sequencing of Cytochrome c oxidase subunit III (COIII). The sequencing of the COIII region revealed 8 bp variable and 6 bp parsimony informative sites between all turbot species. The overall genetic and haplotype diversities among all turbot species were found to be 0.004109 and 0.7655, respectively. Genetic distance analysis showed that the highest nucleotide differences was observed between S. maximus and S. rhombus species with a value of 0.09620 and, the lowest value (0.02482) was observed between S. maximus and S. maeoticus species. Neighbor Joining and Maximum Parsimony phylogenetic approaches resulted in the similar tree topologies that S. maximus and S. maeoticus were found as sister group, whereas S. rhombus was more divergent from this group. The mtDNA COIII gene is a useful genetic marker for species specific identification of the genus Scophthalmus due to its inter-specific heterogeneity producing a species-specific pattern. In morphological analyses, S. rhombus was most differentiated from S. maximus and S. maeoticus. The genetic data was supported by the detected morphometric variations among the turbot species.