Relationship Of Population Genetic Diversity And Pleuronectiformes Fish Flounder

The AFLP technique was used to analyse the genetic diversity of Japanese flounder, Paralichthys olivaceus, including four geographic populations, one natural and one farmed stocks of Rongchen. And complete sequences of ITSl and 18s rDNA were amplified by PCR and sequenced to study the phylogenetic relationships of 9 flatfishes.1 110 individuals from four geographic populations were analyzed by using 7 AFLP primers. 775 bands ranging from 100bp to 1300bp were recorded and 58.32% of which were polymorphic. Genetic similarities within- and among-population were calculated from the binary matrices of presence-absence. Phylogenetic tree of four populations was constructed by using the UPGMA method. According to intrapopulation genetic similarities, Weihai of China population displayed the highest genetic diversity value and Korea population had the lowest genetic diversity value. As for the among-populations genetic distances, the distance between Weihai and Fujian of China populations (0.0747) was maxium and the distance between Weihai and Korea populations (0.0613) was minimum which possibly resulted from the farthest distance of weihai and Fujian of China compare to geographical distance between other locations of populations. The population differentiation coefficient Gst is 0.3565, showing a certain extent differentiation among four geographical populations.2 The genetic structure of the farmed population and the wild population from Rongcheng was analysed using 7 primers. The Genetic similarities and the average hererozygosity of them were 0.90, 0.89 and 0.1093, 0.1225, respectively, which showed the lower genetic diversity in farmed population because of the limited number of effective parents. The population differentiation coefficient Gst between these two populations was 0.1079, showing the genetic structure of farmed population was similar to the wild population because of the first stock of the wild population.3 A 750bp fragment of ITSl of Paralichthys olivaceus was amplified by PCR and sequenced. The G-C content was more than 60% showing a rich G-C framgent. In certain taxa, ITS is nearly exclusively used for population level, despite the frequent presence of divergent paralogs within individual genomes that can be phylogenetically misleading. For the first timewe investigated the utility of the ITSl for population genetic diversity of Paralichthys olivaceus by aligning the sequences of 12 individuals and 11 clones. Analysis of cloned PCR products from a single individual shows that numbers of repeats could vary within an individual. Phylogenetic analysis done by the distance methods (neighbour-joining, Kimura-2-parameter) in MEGA showed the variation between individual and clone was similar between individuals. As a molecular marker, ITSl is not suit to analyse the genetic diversity of populations in Paralichthys olivaceus.4 The nucleotide sequences of ITS 1 and 18S rDNA of 9 flatfish obtained by PCR and sequenced to address the phylogenetic relationships of Pleuronectiformes. The size of 18s rDNA and ITSl was ranged from 1841bp tol874bp, 566bp to 762bp, respectively. Comparative analysis of the nucleotide sequences revealing no obvious variation in 18S rDNA and obvious variation in ITSl proved the coding regions and spacer differ widely in their rate of evolution. The genetic distances and phylogenetic trees conducted by ITS1,18S rDNA and 18S rDNA+ITSl based on neighbor-joining method (NJ) and maximum parsimony method (MP) did not consist with the traditional phylogenetic relationships of 9 flatfish, which suggested that three of fragments could not be used to analyse the molecular evolutionary studies of Pleuronectiformes.