| Unionidae is an important group of freshwater benthos. Due to the convergence phenomenon of freshwater mussels, there is still much controversy in the classification of Chinese Unionidae. In China, most studies on freshwater mussels were emphasized on their resource investigation, biology and morphology, while it is weak in the field of genetics, and deficient in the aspects of population genetic structure and genetic diversity of freshwater mussels. Companied by the aggravation of contamination of the inland waters such as lakes and rivers, disturbance of habitats and overexploitation of resource of freshwater mussels by human hi the late years, genetic diversity of mussels was damaged to some extent and natural resources of some economic mussels have been increasingly decreasing or even are on the verge of extinction, hi order to further understand the status of genetic diversity of different species, it is essential to investigate the molecular phylogenetic relationship of Unionidae on the basis of molecular genetics.Therefore, RAPD markers was used to detect genetic diversity of twenty populations of eighteen species from ten genera in Chinese Unionidae, its phylogeny were studied employing the combined analyses of RAPD markers, rDNA ITS1 sequence analysis and shell morphometrics. The main results are as follows:1. Two DNA extracting methods based on phenol-chloroform were used to extract genomic DNA from soft part tissues of freshwater mussels. The results show that the DNA extraction method based on Sambrook's method is relatively simple and easy to obtain high quality genomic DNA from freshwater unionid species. The contrast experiments indicate that adductor muscle and mantle tissues are ideal materials and suitable for genomic DNA extraction of freshwater mussels, in which the digestive time in 55 water incubation is about five to seven hours and the concentration of proteinase K is about 100~120g/L.2. The genomic DNA of Unio douglasiae, collected from Suya Lake, Henan Province, was used as template DNA to optimize the RAPD-PCR reaction conditions including the concentration of DNA template, random primer, dNTPs, Mg2+ and Taq DNA polymerase and the annealing temperature for thermal cycle. The optimized reaction systems for RAPD amplification are as follows: For a 25ul reaction system, the optimal condition included 10 X Taq Reaction buffer 2.5 u 1, 2.0mmol/L MgCl2, 0.1% Triton X-100, 0.2mmol/L dNTPs, 1.5U Taq DNA polymerase, 30ng template DNA, 0.2 v. mol/L (about 15ng) Primer. The optimal program for efficient amplification included 45 cycles of denaturation at 94 for 1 min (94 for 5 min for the first cycle), annealing at 37 for 1 min and extension at 72 for 2 min (10 min for the final cycle), and the last products were finally stored at 43. Random amplified polymorphic DNA (RAPD) markers was used to detect geneticVIIdiversity of twenty populations of ten genera in Chinese Unionidae. Sixteen random primers, which were screened from 80 primers of groups OPI, OPP, OPG and OPM, were used for RAPD amplifications and the polymorphism of amplified loci were analyzed. The results demonstrate that the percents of amplified polymorphic loci for various populations range from 34.5% to 78.1%, the mean Shannon's genetic diversity indices range from 0.1891 to 0.4233, the mean intra-population genetic distance ranges from 0.0708 to 0.2169, and the genetic diversities of various populations measured by these three indices are basically consistent. In all twenty populations, the genetic diversity for Unio douglasiae is the largest, Solenaia oleivora takes the second place, and the percents of RAPD amplified polymorphic loci for both populations are all larger than 70%. The percents of RAPD amplified polymorphic loci for Lanceolaria grayana and Anodonta fluminea are lower than 40%; the intra-population Shannon's genetic diversity index is 0.1891 and intra-population genetic distance is 0.0708, and they are the lowest in all populations. For three geographic populations of Crist aria plicata in Zhangdu...
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