Probing Into The Genetic Structure Of Black-spotted Frog Located In The Yangtze River Based On Microatellite And Mitochondrial Control Region

Pelophylax nigromaculata is the most widely distubuted anuran amphibians in mainland China.In recent years, due to habit destruction, environmental pollution, hunting and the other reasons, the species has been experiencing rapid recession (Xie,2006). On the other hand, the characteristics of widely distribution, limited capacity and easy sampling make anuran amphibians an ideal species for the study of phyloge-ography (Zeisset and Beebee,2008). In this study, we select12cities along the Yangt-ze River basin for samples collection. We set sampling point in the north and south sides of the Yangtze River in every city. Finally, a total of24geographic populations are got. Then, we use the microsatellite and the mitochondrial as molecular marks to detect the genetic structure of the population. The main findings are as follows:(1) The detection of genetic diversity based on microsatellite and mitochondrial control regionThe analysis results of the two marks show that the genetic diversity of the pel-ophylax nigromaculatat population along the Yangtze River basin is maintained at a high level, but the diversity distribution is uneven.The results based on microsatellite show that, the mean number of alleles, the mean expected heterozygosity, the mean Polymorphism Information Content of upriver population, midriver population and downriver population as follow:21.38.0.851.0.833;8.00.0.860.0.839;19.38.0.872.0.853.The results based on mitochondrial control region show that, the number of detected individuals, the number of haplotype, the haplotype polymorphism of upriver population, midriver population and downriver population as follow:176.62.0.752;51.46.0.995;33.27.0.983.(2)The detection of genetic differentiation among populations based on microsat-ellite and mitochondrial control regionIn the analysis based on microsatellite, we get276FST value, of which91.7%FST>0.05. The average value is0.188. For upriver population, we get91FST value, of which94.5%FST>0.05; for midriver population, we get15FST value, of which 80%FsT>0.05; for downriver population, we get6FST value, of which66.7%FST>0.05.In mitochondrial analysis,276FST value are got, of which58.7%FST>0.05. For upriver population, we get91FST value, of which65.9%FST>0.05; for midriver population, we get15FST value, of which20%FST>0.05; for downriver population, we get6FST value, of which33.3%FST>0.05.Two markers display a relatively limited exchange between different populations Mantel test results based on two marks show that there is no significant correl-lation between the genetic differentiation among populations and the geographic distance. This implies that the terrain factors may play an important role in affecting the genetic structure of the Pelophylax nigromaculatat population along Yangtze River basin.(3) To explore population phylogenetic relationship based on microsatellite and mitochondrial control regionStructure Cluster analysis doesn’t show obvious clustering results. The NJ tree and the ML tree based on118mtDNA control region haplotypes don’t form a distinct phylogenetic pedigree. This shows that there is a certain degree of gene flow among the populations, at the same time, the genetic difference amog the popularions revealed by mitochondrial is not significant, especially for the midriver and the downriver population; on the other hand, the climate change in Pleistocene glacial-interglacial is likely to make the Pelophylax nigromaculatat population experience repeated contraction-expansion, making the degree of differentiation between populations have not yet reached the significant testing standard.(4) The detection of population bottleneck effect based on microsatellite marker The results show that a total of15populations have experienced significant or extremely significant bottleneck effect when using different detection model. These populations which recently experienced a population bottleneck effect do not gather in adjacent region, and distribute along the entire Yangtze River. This may imply the main cause of the Pelophylax nigromaculatat population decline may be the hunting or the habitat destruction. Because of the recession caused by the disease or climate change always displays a regional populations full-blown recession (Wake and Vredenburg,2008).(5) Explore the dynamic history of Pelophylax nigromaculatat population along the Yangtze River based on mitochondrial control regionWhen regarding24populations as a large population, the Tajima’s D values and Fu’s Fs value are all less than0, but the former does not reach a significant level (P=0.11), while the latter reach a significant level (P=0.002), which shows that the population accumulated many low-frequency mutations. Mismatch distribut-tion analysis shows multi-peaks, but this does not prove the group is in a state of equilibrium, this may also be the reason of the dynamic history of different populations within the group is different.