Taxonomic status of the black porgy, Acanthopagrus schlegelii (Perciformes: Sparidae) inferred from mitochondrial genes

The black porgy Acanthopagrus schlegelii (Bleeker, 1854) is a commercially important fish distributed in estuarine and coastal waters of the west Pacific Ocean. Based on body color pattern, two subspecies A. schlegelii schlegelii (dark-unicolored specimens) and A. schlegelii czerskii (striped specimens) were suggested by some taxonomists. However, due to the morphology similarity, the phylogenetic relationship between the two subspecies has been long-lasting confused. The purpose of this study was to evaluate the taxonomic status of the two subspecies by two mitochondrial genes, cytochrome oxidase subunit І (COI) and control region (CR). Eight A. schlegelii schlegelii and eight A. schlegelii czerskii were collected from the coastal waters of the Yellow Sea, the East China Sea and the South China Sea. The genetic diversity, genetic distance and phylogenetic relationship of the two subspecies were analyzed and compared. The genetic diversity indices were close to each other in COI, but more different in CR. The mean genetic distances between the two subspecies was 0.0015 in COI and 0.0051 in CR, respectively. These values are much lower than those found for interspecific COI and CR comparisons among some species of Acanthopagrus (0.0667 to 0.0954 in COI and 0.2267 to 0.2480 in CR). Moreover, haplotypes of the two subspecies did not form reciprocal monophyletic clades in the phylogenetic trees based on the two mitochondrial genes. These results indicate that the genetic distance between the two subspecies, A. schlegelii schlegelii and A. schlegelii czerskii, was at the intraspecies level; they should be classified into the same species: A. schlegelii. It is suggested that A. schlegelii schlegelii and A. schlegelii czerskii should be regarded as the junior synonyms of A. schlegelii.Key words: Acanthopagrus schlegelii schlegelii, A. schlegelii czerskii, mitochondrial DNA, molecular phylogeny, taxonomic status