The Analysis Of Genetic Structure On Glyptothorax Laosensis Fowler In Lancang River

Glyptothorax laosensis belonging to family Sisoridae and order Siluriformes, is one of the Glyptothorax catfish species. It is distributed in China only in Lancang River basin. With the development of hydroelectric project in this basin, the habitat of the fish is ecpected to change tremendously. In this study, we used two kinds of molecular genetic systems, mitochondrial DNA and microsatellite DNA, to search the genetic diversity and structure of G. laosensis from 8 sampled sites. Our goal was to provide and report baseline data on the genetic structure of this sensitive species. The main results were as following:1 The genetic structure of G. laosensis based on mitochondrial genome(1)A total of 129 specimens were sampled from eight sites in the basin of Lancang River. Genes of cytochrome b and control region in mitochondrial DNA were amplified by Polymerase China Reaction and sequenced on both chains. In cytochrome b, sixteen polymorphic sites were found from the aligned sequences, and fifteen haplotypes were identified among 129 sequences. There were 35 mutation sites in control region sequence, and 42 haplotypes were identified. We used neighbor-joining tree and network of haplotypes analysis to show that no relationship between the distribution of haplotype and sampled sites, and suggested a single population.(2)The Analysis of Molecular variance (AMOVA) indicated that the variation within sample is greater than the variation between samples. This suggests that G. Laosensis exchange genes across our entire study area, however minor residual variation remains at the sample site scale.(3)Mismatch distribution pattern indicated that the wild population had experienced a population expansion in history by the Cytb gene sequences dated to 0.88-1.47 Ma BP. But the control region data show that the mismatch distribution is double summit style, and the Neutral test results are not significant indicated no range expansion, therefore, our results were inconccosive concerning past range expansions.(4)Because our results provided evidence for a single population with active gene exchange, in situ conservation actions that presence gene flow would be beneficial.From now on, the scale of wild population is still modest,there are not population variation. It will be right to protect the population in situ conservation.2 Character and isolation of microsatellite sequence (1) Microsatellite markers were developed from an enriched genomic library. After library screening,220 clones containing microsatellite sequence (two or three bands in PCR results),38 clones were randomly selected to sequence. Twenty sequences were designed in 20 pair primers, there were twelve pair primers successfully amplified products while eight were polymorphic.(2) The number of alleles were 40 with an average of 5, the Polymorphism Information Content ranged from 0.3457 to 0.9056, with an average of 0.7528, The range of expected heterozygosity(He) varied from 0.1667 to 1.0000 with an average of 0.7736. The observed heterozygosity (Ho) ranged from 0.4787 to 0.9608. All data show that the locus is highly polymorphism, therefore it can be used as an available microsatellite marker.(3) The analysis of molecular variation variance (AMOVA) showed that the variation is from the within population, FST=0.02148 also indicate that the genetic variation is from within the population mainly. Mega analysis demonstrated the genetic distance is small.