Genetic Structure Of Rhinogobio Ventralis Endemic To The Upper Yangtze River

Rhinogobio ventralis is a kind of small and economic fish belonging to Gobioninae (Cyprinidae), and endemic to the upper Yangtze River in China. However, the hydroelectricity development in the upper Yangtze River has changed the river basin’s original bio-environment and influenced the existence and development of R.ventralis populations. In order to make a better understanding of the genetic diversity and differentiation of this species,6R.ventralis populations which were sampled in the main stream and tributaries of the upper Yangtze River were investigated by two kinds of molecular markers systems:mitochondrial DNA and microsatellite DNA. The main results are as follows:1. Genetic structure of R.ventralis based on mitochondrial genome1) A total of107sequences of R.ventralis based on Cytb gene were analysised, eighteen polymorphic sites and eighteen haplotypes were found and identified, the haplotype diversity and nucleotide diversity were0.709and0.00143, respectively; A total of116sequences of R.ventralis based on control region were analysised,32polymorphic sites and41haplotypes were found and identified, the haplotype diversity and nucleotide diversity were0.814and0.00165, respectively. Compared with Coreius heterodon、Coreius guichenoti、Myxocyprinus asiaticus、Glyptosternum maculatum and Trachurus japonicus, the genetic diversity of R.ventralis was relatively low.2) Mismatch distribution pattern and Fu’s Fs Neutral test result based on Cytb gene indicated the R.ventralis population had experienced a population expansion in history, but Neutral test result didn’t support the conclusion; while, Mismatch distribution pattern and Fu’s Fs、Tajima’s D Neutral test results based on control region all indicated that the R.ventralis population had experienced a population expansion in history.3) The neighbor-joining tree and network of haplotypes showed no relationship between the distribution of haplotype and sampled sites, and suggested a single population.Gene flow and the Analysis of Molecular variance (AMOVA) based on Cytb gene and control region indicated that there are widely gene flows among populations, the most genetic variation was distributed within populations. However minor residual variation remains at the sample site scale.2. Development of the microsatellite markers and populations genetic structure analysis1) Microsatellite markers were isolated through FIASCO protocol. A total of165clones were sequenced,92(55.8%) of which contained repeat motifs and suitable for designing primer,55primer pairs were designed using the Primer Premier5.0software.10pair primers were polymorphic and amplified successfully.8polymorphic microsatellite loci, excepted RV-4and RV-6, were identified202alleles totally; the number of alleles per locus varied from5(RV-2) to48(RV-7) with an average of25.25; polymorphism information content (PIC) value ranging from0.38585(RV-2) to0.907583(RV-7). Out of these8polymorphic microsatellites, only1loci (RV-2) significantly deviated from Hardy-Weinberg equilibrium in the RVJ and RVN populations (P<0.1). Therefore the other7loci can be used for studing on population genetics as available microsatellite markers.2) The number of alleles of the6populations varied from5.25(RVC) to18(RVJ);The observed heterozygosity(Ho)value ranging from0.7021(RVN) to0.8875(RVS), expected heterozygosity (He) value ranging from0.8304(RVC) to0.8586(RVS) and polymorphism information content (PIC) value ranging from0.6805(RVC) to0.8218(RVJ).3) The analysis of molecular variation variance (AMOVA) showed that the most genetic variation was distributed within populations, the genetic differentiation among populations was not statistically significant. Pairwise Fsr and Nei’s genetic distance also demonstrated the low genetic differentiation and the small genetic distance among6R.ventralis populations. R.ventralis was suggested in situ conservation as a single evolutionarily significant unit(ESU), and protection of the rare and endemic allele should be taken seriously.