洪泽湖野生河蚬(Corbicula fluminea)线粒体COⅠ基因序列的遗传多样性分析

Genetic Diversity of Wild Corbicula fluminea Population in the Hongze Lake Analyzed by Mitochondrial DNA CO I Gene Sequence

关键词:  河蚬  细胞色素氧化酶亚基Ⅰ  遗传多样性  洪泽湖

Key words:  Corbicula fluminea  Cytochrome coxidase subunit Ⅰ  Genetic diversity  Hongze Lake

摘要:

利用线粒体细胞色素氧化酶亚基Ⅰ(COⅠ)分子标记对洪泽湖河蚬(Corbicula fluminea)野生种群的遗传多样性水平进行分析。采集洪泽湖野生河蚬50个个体，对COⅠ基因序列片段进行PCR扩增和序列测定。结果显示，长度为614 bp的COⅠ基因片段中，碱基A、T、G和C的平均含量分别为22.6%、42.4%、21.0%和14.0%，A+T的含量(65.0%)显著高于G+C的含量(35.0%)。COⅠ基因序列中有67个核苷酸变异位点，总变异率为10.9%，其中简约信息位点63个，单一信息位点4个。50条COⅠ基因序列共定义了15个单倍型，单倍型多样性指数(h)和核苷酸多样性指数(π)分别为0.870和0.045，平均碱基差异数(K)为27.370，单倍型序列间的遗传距离为0.002−0.095。采用邻接法(NJ)和最大简约法(MP)构建COⅠ单倍型系统进化树，15个单倍型聚为两个明显分支，表明洪泽湖河蚬种群出现了遗传分化。中性检验结果和歧点分布图显示，洪泽湖河蚬种群大小保持相对稳定，未经历种群扩张。本研究结果表明，洪泽湖河蚬种群具有较高的遗传多样性水平，该结果可为合理开发、利用及保护洪泽湖河蚬野生种质资源提供科学参考。

Abstract:

Corbicula fluminea is a common macrozoobenthos in the freshwater of the Hongze Lake, which plays an important role in the cycle of mass and energy fluxes of fresh water ecosystem. However, the wild source of C. fluminea has sharply decreased recently due to over-fishing and water pollution. The genetic diversity of C. fluminea in the Hongze Lake has not been widely investigated. The present study analyzed the genetic diversity of C. fluminea population in the Hongze Lake using mitochondrial DNA cytochrome coxidase subunit Ⅰ (COⅠ) gene molecular marker. The mitochondrial DNA COⅠgene fragments were amplified and sequenced from 50 individuals of wild C. fluminea in the Hongze Lake. The contents of A, T, G and C in the 614-base pair fragments of COⅠgene were 22.6%, 42.4%, 21.0% and 14.0%, respectively, and the content of A+T was significantly higher than that of G+C. Sixty-seven polymorphic sites were detected, accounting for 10.9% of the total sequences, and of which sixty-three were parsimony- informative sites and four were singleton sites. Fifteen haplotypes were defined in 50 individuals of C. fluminea. The mean haplotype diversity, nucleotide diversity, and the average number of nucleotide difference in the C. fluminea population were 0.870, 0.045 and 27.370, respectively. The genetic distance among fifteen haplotypes ranged from 0.002 to 0.095. Neighbor-joining (NJ) and maximum-parsimony (MP) trees divided fifteen haplotypes into two clades, suggesting that C. fluminea populations had significant genetic difference. Mismatch distribution analysis showed a multiple type, and Tajima’s D value (2.724) of neutrality test is positive but significantly different, demonstrating that C. fluminea in the Hongze Lake hadn’t experience a recent population expansion. These results suggest that the genetic diversity of C. fluminea population in the Hongze Lake is high, which provides scientific information for the conservation and sustainable exploitation of C. fluminea.