DNA Barcoding Of Epinephelinae In Coastal Waters Of China

The subfamily Epinephelinae (Serranidae:Perciformes) is commonly known as groupers, which is economically important and highly valued marine fishes in the world. These bottom-associated fishes are widely distributed in tropical and subtropical waters in the Pacific, the Indian and the Atlantic Ocean, and most species occur on coral or rocky reefs. In recent years, the number of groupers is sharply decreased due to the human activities such as marine environment pollution, habitat destruction, and overfishing. Many groupers are mainly identified based on color patterns, body shape and other morphological charaters. As the juveniles of the same species may look quite different from the adults, different species may look alike morphorlogically, and the color patterns of lines and spots in their body are easily altered by their surrounding environments, it is difficult to identify species of groupers morphologically.Recently, DNA Barcoding is becoming more and more attractive to biologists as a rapid and simple method for animal species identification. The present study involved in totally 381 fish's COI sequences (652bp) which belongs to 60 species,10 genus of groupers. Of which sequences of 106 fish from 36 species,10 genus were determined in the present study and other data were downloaded from Genbank. The validity of DNA barcoding in groupers species'identification and their utility in phylogenetic reconstruction were discussed. The main results are as follows:1) Contrasting to the average interspecies K2P distance (9.66%) within the same genera, the average intraspecies distance was only 0.65%, the ratio of interspecies vs intraspecies genetic distance was 14.9, hence the partial mitochondrial COI gene(652bp) is a good DNA barcoding marker in groupers identification.2) Most sequences of the same species were clustered together in NJ tree, however some sequences of the same species did not, which might be mainly resulted from false identification, and evolutionary radiation, nuclear mitochondrial DNA segments, and introgressive hybridization may also other reasons. For example, E.malabaricus, E.tauvina, E.awoara and E.coioides might be the production of evolutionary radiation. E.diacanthus HQ589272 was resulted from the mitochondrial DNA integrated into the nuclear genes. C.boenak and C.igarashiensis, C.boenak and C.formosa, C.sonnerati and C.argus, E.malabaricus, E.awoara might be due to introgressive hybridization. Besides, the genetic distance within species such as Eamblycephalus, E.fasciatus, A.leucogrammicus were much higher than 2%, suggesting the existence of cryptic species.3) DNA barcoding region contains some phylogenetic information, for example, A.leucogrammicus, T.dermopterus and C.altivelis were embedded in the genus of Epinephelus, supporting the paraphyly of the genus Epinephelus. T.dermopterus, E.acanthistius and E.ergastularius formed a clade. Cephalopholis was independent from the genus Epinephelus, indicating its validity as a genus rather than a subgenus within Epinephelus. However the 652 bp sequences in DNA barcoding region contains too few phylogenetic information to resolve the complicated phylogenetic relationships of the groupers.