| S.chuatsi and S.kneri (Sinipercinae:Serranidae:Perciformes) endemic to East Asia, commonly known as mandarin fish, are rare freshwater fishes with important economic, ecological and scientific values. Affected by climate change, overfishing, river pollution, dams building and environmental changing factors, the population of wild mandarin fish has been increasingly decreased and the germplast resources degraded, therefore, it is urgent to protect the valuable fish. S. chuatsi and S. kneri are very similar morphologically, and transitional types are difficult to distinguish, so we've got to determine their species status and have a clear understanding of the genetic variation. In the present study, sequences of complete mitochondrial control region of 163 mandarin fish from 9 different locations in the Yangtze River drainage were determinined with S.chuatsi and S.kneri topotype as references. Results were obtained as following:1.72 variable sites (accounting for 9.4% of the total number of nucleotides),57 parsimony informative sites and 15 sites of a single variable were detected in the totally In the 840bp control region. ETAS, CSB-F, CSB-E, CSB-D, CSB1, CSB2, CSB3 zone structures were determined.2. In the molecular phylogenetic tree, S.chuatsi, S.kneri and transitional type didn't clustered together separately, showing scattered, irregular distribution in the tree. There were no obvious geographical structure and pedigree structure. Interspecific genetic distances among S.chuatsi, S.kneri and transitional type were 0.008, and intraspecific genetic distances were 0.008,0.007 and 0.008 respectively, i.e. Interspecific and intraspecific distance were at the same level. AMOVA (Analysis of Molecular Variance) showed that the differences between S.chuatsi, S.kneri and transitional type were 91.15% within populations and only 0.38% between populations, so there were no significant genetic differentiation between S.chuatsi, S.kneri and transitional type. Although S.chuatsi and S.kneri have been regarded as having certain morphological distinction, there are some transitional types, and they could not be separated as two sub-species or even species at the molecular level, indicating that they might be the same species.3. In 163 individuals of mandarin fish collected from the Yangtze River drainage,66 haplotypes were found. The average haplotype (hd) and nucleotide diversity (Pi) were 0.962±0.007 and 0.00717±0.00037 respectively, indicating high haplotype diversity and low nucleotide diversity pattern. 16 haplotypes were shared among populations, which accounted for 24.24% of the total haplotypes. The genetic distance within and among groups was from 0.007 to 0.010 and from 0.006 to 0.009 respectively. AMOVA analysis showed that the differences among geographical populations were mainly within group. Fst between Nanchong population to the remaing populations is the largest (more than 0.05), indicating its genetic differentiation to other populations. The highest nucleotide diversity was 0.00851±0.00128 in Yun County population, and the genetic distance between Yun County population and other populations was the largest(from 0.009 to 0.010), indicating that the genetic relationship of Yun County population to other populations were relative far, therefore Yun County and Nanchong populations were recommended to be protected in priority. As Yueyang populations (Dongting Lake) located near the main stream also had relatively more abundant genetic diversity, it might be better protected too. it is necessary to take measures to recover genetic diversity in Taihu population (lowest in Yangtze River). When 9 populations in the Yangtze River were analyzed as a whole or sperately, neutral detection of Tajima's D value were negative but not significant except Taihu population, and Fu'F value were partlty negative but also not significant. At the same time, two mountains derived from the nucleotide mismatch distribution diagram showed that Mandarin fish in the Yangtze River had not experienced population expansion as a whole or separate population. |
