Cytochrome oxidase 1 gene sequence analysis in six flatfish species (Teleostei, Pleuronectidae) of Far East Russia with inferences in phylogeny and taxonomy

Abstract

Mitochondrial DNA at the cytochrome oxidase 1 (Co-1) gene region was sequenced for six flatfish species (in total, 11 sequences of at least 539 base pairs) from the Far East of Russia and compared with other sequences of Pleuronectiformes, comprising altogether 26 flatfish sequences and two outgroup sequences (Perciformes). An analysis of the protein-coding Co-1 gene revealed a statistically substantiated bias in (T+C):(A+G) content, supporting earlier findings. Average scores of the p-distances for different scales of the evolutionary history at the Co-1 gene revealed a clear pattern of increased nucleotide diversity at four different levels: (1) intraspecies, (2) intragenus, (3) intrafamily, and (4) intra-order. Scores of average p-distances of the four categories of comparison in flatfishes were (1) 0.17 ± 0.09%, (2) 10.60 ± 1.57%, (3) 12.40 ± 0.27%, and (4) 19.93 ± 0.05%, respectively (mean ± standard error). These data jointly with current knowledge support the concept that speciation in the order Pleuronectiformes mostly follows a geographic mode through accumulation of numerous small genetic changes over a long period of time. A phylogenetic tree for 26 sequences of flatfishes and two other fishes belonging to ray-finned fishes (Actinopterigii) was developed using the Co-1 gene and four different analytical approaches: neighbour-joining, Bayesian (BA), maximum parsimony (MP), and maximum likelihood. The analysis revealed a monophyletic origin for the representatives of Pleuronectidae, which is the principal flatfish family investigated (73–100% support level in our MP and BA analyses).

According to the current and literary data, the monophyletic origin for the six compared flatfish families was well supported. Species identification on a per-individual basis (barcoding tagging) was high.

• Molecular phylogeny
• taxonomy
• sequence
• p-distance
• cytochrome oxidase 1
• flatfish

Acknowledgements

The authors are very grateful to Mrs I. A. Barsegova for proofreading the manuscript. This work was also supported in part by Far Eastern Branch of Russian Academy of Science (FEB RAS; grant number 07-III-B-06-035, FEB RAS grant number 08-III-B-06-031) and the Russian Foundation for Basic Research (grant number 07-04-00186, grant number 08-04-91200).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.