The Genetic Diversity In Pseudosciaena Polyactis, Trichiurus Lepturus, Eupleurogrammus Muticus And The Molecular Phylogenyof Eight Sciaenoid Species In The Neritic Waters Of China

The thesis mainly contains three parts as fallowings: Part one: The genetic diversity in Pseudosciaena polyactisP. polyactis is a commercially important fish species and widely distributed in the Bohai Sea, the Yellow Sea and the northern part of the East China Sea. For the purpose of conservation and sustainable utilization of this valuable species, it was necessary to investigate the genetic diversity of P. polyactis. Using 20 out of 40 decamer random primers, random amplified polymorphic DNA (RAPD) was applied to analyze the diversity of 48 individuals of P. polyactis from five sampling areas in the Yellow Sea and the East China Sea. A total of 145 RAPD loci were obtained, of which 132 loci (91.03%) were polymorphic. Genetic diversity quantified by Shannon index varied from 1.50 to 2.44 with an average of 1.93; Partition of genetic variability indicated that 69% was distributed within, and 31% among stocks. The average genetic similarity and genetic distance were 0.9139 and 0.0861 respectively. Cluster analysis by UPGMA methods indicated that these five stocks might be divided into three clusters. Results of RAPD analysis suggested that extensive genetic diversity was detected in this species and the geneticdivergence among stocks was relatively high; UPGMA phylogenetic tree showed there existed three geographic populations of P. polyactis in the Yellow Sea and the East China Sea, which supported the previous conclusion by morphological and ecological methods.Part two: The genetic diversity between Trichiurus lepturus and Eupleurogrammus muticusRandom amplified polymorphic DNA (RAPD) technique was applied to 12 individuals from each species of the hairtail fishes Trichiurus lepturus and Eupleurogrammus muticus collected from the Yellow Sea. The percentage of polymorphic sites, degree of genetic polymorphism and genetic distance were compared and the phylogenetic tree was constructed by Neighbor-joining method. The partial mitochondrial 16S rRNA gene was amplified by polymerase chain reaction (PCR) and the PCR products were directly sequenced after purified. These sequences, together with the homologous sequences of another Trichiuridae species Lepidopus caudatus obtained from GenBank were used to analyze nucleotide difference and to establish a UPGMA phylogenetic tree by means of biological informatics. As analyzed, (1) the RAPD technique is highly sensitive to investigating genetic diversity in T. lepturus and E. muticus. T. lepturus exhibits lower polymorphism and genetic diversity than E. muticus; (2) according to the analysis of the partial mitochondrial 16S rRNA gene sequences, a very low intraspecific variation and considerably high divergence among species were found, which reveals adual nature of conservatism and variability in mitochondrial 16S rRNA gene; (3) five primers generate the species-speeific RAPD sites and these sites can be served as the molecular markers for species identification and (4) it can be proved at DNA variation level that T. lepturus and E. muticus are of two species respectively pertainiag to different genera, which supported the Nelson taxonomic conclusion.Part three: The molecular phytogeny of Sciaenoid speciesPolymerase chain reaction (PCR) was used to amplify the partial mitochondrial 16S rRNA gene of eight Sciaenoid species from six genera distributed in the neritic waters of China, and the PCR products were directly sequenced after purified. By means of several bio-softwares, sequence differences and base composition were analyzed, and some genetic information indices were calculated, including genetic distance, average number of nueleptide difference between species and average number of nucleotide substitution per site between species etc. These sequences, together with the homologous sequences of Pomadasys maculates (Outgroup) obtained from GenBank were used to construct four phylogenetic trees (UPGMA, NJ, ME and MP). As analyzed, Johnius belengerii derived from Sciaeninae firstly, earlier than Nibea albiflora and Argyrosomus argentatus, whi...