基于线粒体DNA控制区序列的珠江和长江水系光倒刺鲃群体遗传变异分析

【目的】明确珠江和长江水系不同光倒刺鲃地理群体的遗传变异及进化关系，为其种质资源保护和可持续开发利用提供科学依据。【方法】从珠江水系（增江、流溪河、北江、连江、漓江、柳江和郁江）和长江水系（阊江、赣江和湘江）的10个支流（群体）采集347尾光倒刺鲃样本，扩增并测定其线粒体DNA（mtDNA）控制区序列；通过MEGA 6.0、DnaSP 6.10和Arlequin 3.5等在线软件统计序列碱基组成、变异位点、遗传距离、核苷酸多样性（π）、单倍型多样性（H_d）及遗传分化系数（F_st），并进行分子变异分析（AMOVA）、核苷酸错配分布分析、中性检验，以及构建单倍型的系统发育进化树和网络结构图。【结果】光倒刺鲃mtDNA控制区序列长度为519 bp，其中T、C、A、G占比平均值分别为32.57%、19.16%、32.16%和16.11%。在所有mtDNA控制区序列中共检测到62个变异位点，34个单倍型；10个光倒刺鲃群体的H_d平均为0.917，π平均为0.0359，遗传距离为0.0018~0.0790，F_st为-0.0007~0.9978。光倒刺鲃mtDNA控制区序列63.46%的分子遗传变异来自各地理分组间；单倍型网络结构图和系统发育进化树均显示，10个光倒刺鲃群体聚类为三大支系，除了有个别交集外，东江水系、西江水系、赣江水系+湘江水系的光倒刺鲃群体分布在3个不同的独立分支上，而北江+流溪河水系群体分别与东江水系群体和西江水系群体有较多交集。10个光倒刺鲃群体的Fu’s Fs为-1.339~23.759，平均为9.857，但P均大于0.05；Tajima’s D为-2.613~2.824，仅有3个群体的Tajima’s D为显著性负值（P<0.05）；其核苷酸错配分布图谱呈多峰形式，即珠江和长江水系光倒刺鲃群体尚未发生过种群扩张。【结论】珠江和长江水系光倒刺鲃群体遗传多样性总体上偏低，应加强其种质资源保护，尤其是北江水系群体野生资源相对较丰富宜作为重点保护单元。复杂的地形地貌导致珠江和长江水系光倒刺鲃群体形成明显的地理隔离，群体间已发生明显分化，且受各种人为活动干扰导致其种群收缩，因此亟待采取有效防护措施以保证光倒刺鲃种质资源的可持续利用。

Analysis of genetic variation among Spinibarbus hollandi in the Pearl River and the Yangtze River based on mitochondrial DNA control region sequences

【Objective】 To characterize the genetic structure and phylogeographic pattern of different populations of Spinibarbus hollandi in the Pearl River and the Yangtze River, in order to provide the scientific basis for the conservation and sustainable utilization of S. hollandi populations resources.【Method】 In this study, 347 S. hollandi samples were collected from 10 populations in the Pearl River(the Zengjiang, Liuxi, Beijiang, Lianjiang, Lijiang, Liujiang and Yujiang rivers) and the Yangtze River(the Changjiang, Ganjiang and Xiangjiang rivers). The mitochondrial DNA(mtDNA) control region sequences from each individual were identified and analyzed. According to the MEGA 6.0, DnaSP 6.10 and Arlequin 3.5 software, the base composition, the locus of variation, genetic distance, nucleotide diversity(π), haplotype diversity(H_d) and genetic variation value(F_st) were calculated. In addition, molecular variation analysis(AMOVA), nucleotide mismatch distribution analysis, neutral test, the construction of a haplotype phylogenetic evolutionary tree and network diagram were also carried out.【Result】 The sequence length of the mtDNA control region was 519 bp, in which T, C, A and G accounted for 32.57%, 19.16%, 32.16% and 16.11%, respectively. A total of 62 mutated loci and 34 haplotypes were detected in the sequences. The average haplotype diversity, nucleotide diversity, genetic distance and F_st were 0.917, 0.0359, 0.0018-0.0790 and -0.0007-0.9978, respectively. 63.46% of the molecular genetic variation of the mtDNA CR was observed in the distinct geographical groups. According to the haplotype phylogenetic evolutionary tree and network diagram, ten S. hollandi populations were divided into three groups, with the populations in the Dongjiang River, Xijiang River and Ganjiang River plus Xiangjiang River distributed in three independent branches. However, the Beijiang River and Liuxi River populations had more overlaps with the Dongjiang River and Xijiang River populations. Among the ten populations, the Fu'S Fs ranged from -1.339 to 23.759, with an average of 9.857, but all P values were greater than 0.05. Tajima's D ranged from -2.613 to 2.824 and was significantly negative in only three populations(P< 0.05). The map of nucleotide mismatch distribution showed a multi-peak pattern, indicating that population expansions did not occur in the Pearl River and Yangtze River.【Conclusion】 The genetic diversity of S. hollandi population is generally low. Therefore, the protection of germplasm resources needs improvement, and populations from the Beijiang River should be taken as a key protection unit. The complex landform results in the obvious geographical isolation of S. hollandi populations in the Pearl River and the Yangtze River, and the obvious differentiation among the populations, and the population shrinkage caused by anthropogenic activities had being formatted. Therefore, it is urgent to take effective protective measures to ensure the S. hollandi resources.