基于线粒体COII基因序列的长江下游翘嘴群体遗传多样性分析

【目的】明确长江下游翘嘴鲌（Culter alburnus）群体遗传多样性的丰富程度和进化历史，为其育种及遗传改良打下基础。【方法】在长江下游水域（淀山湖、高邮湖、太湖、长荡湖及长江江苏段）设点捕获收集翘嘴鲌野生样本，基于线粒体COII基因序列分析5个翘嘴鲌野生群体的遗传多样性，使用DNASPv5计算群体单倍型并进行Tajima’s D和Fu’s Fs中性检验，运用Arlequin 3.5进行遗传多样性分析、群体分子方差分析（AMOVA）及计算遗传距离和基因流（Nm）。【结果】 5个翘嘴鲌野生群体197个个体的COII基因序列有效长度为425 bp，存在31个变异位点，变异率为7.29%；其碱基含量排序为T （29.61%） >C （28.03%） >A （24.19%） >G （18.17%），AT含量为53.8%，CG含量为46.2%。31个变异位点在197个个体中共定义出13种单倍型（hap1~hap13），单倍型多样性指数（H_d）为0.273~0.603，以长江群体和长荡湖群体的最高，太湖群体的最低；核苷酸多样性指数（P_i） 为0.001~0.017，以长荡湖群体的最高，淀山湖群体的最低。5个翘嘴鲌野生群体间的遗传距离为0.002~0.015，即群体间无显著差异；不同群体间的Nm为2.443~54.325，以太湖群体与淀山湖群体间的Nm最大（54.325），长荡湖群体与淀山湖群体间的Nm最小（2.443）； AMOVA分析结果显示，不同群体间的遗传变异为10.47%，而群体内的遗传变异为89.53%。在5个翘嘴鲌野生群体中，仅长江群体的Tajima’s D和Fu’Fs均为负值且具有显著意义，故推测该群体曾发生过群体扩张现象。【结论】长江下游翘嘴鲌群体表现出低单倍型多样性和高核苷酸多样性，遗传多样性较丰富，群体间存在遗传分化但分化程度差异不显著。因此，后续研究应增加野生翘嘴鲌群体的样品数量和调查水域，全面而系统地评估长江下游各水域翘嘴鲌的种质资源状况，为建立自然保护区及人工增殖放流提供科学依据。

Genetic diversity analysis of Culter alburnus populations in the lower reach of Yangtze River based on COII gene sequences

【Objective】To clarify the genetic diversity richness and evolutionary history of Culter(Culter alburnus) populations in the lower reach of Yangtze River, so as to a foundation for its breeding and genetic improvement.【Method】In the lower reach of Yangtze River waters(Dianshan Lake, Gaoyou Lake, Taihu Lake, Changdang Lake and Jiangsu section of the Yangtze River), wild Culter alburnus samples were collected, and the genetic diversity of 5 different geographic C. alburnus populations based on mitochondrial COII gene sequences. Population haplotypes were calculated with DNASPv5. Tajima's D and Fu's Fs neutrality tests were conducted. Genetic diversity analysis, population molecular variance analysis(AMOVA), and genetic distance calculation and gene flow(Nm) calculation were conducted by Arlequin 3.5.【Result】The results of sequencing analysis for detection of total 197 individuals of 425 bp COII sequences to 31 mutation sites. Ordination of base content was:T(29.61%) >C(28.03%) >A(24.19%) >G(18.17%). AT content was 53.8%, CG content 46.2%. A total of 13 haplotypes(hap1-hap13) were defined in 197 individuals, and the haplotype diversity index (H_d) was 0.273-0.603, with the highest in the Yangtze River population and the Changdang Lake population, and the lowest in the Taihu Lake population. The nucleotide diversity index(P_i) ranged from 0.001 to 0.017, with the highest in Changdang Lake and the lowest in Dianshan Lake. The genetic distance among the 5 populations ranged from 0.002 to 0.015, indicating that there was no significant difference among the populations. The Nm among different populations ranged from 2.443 to 54.325. The Nm between Taihu Lake population and Dianshan Lake population was the largest (54.325), and the Nm between Changdang Lake population and Dianshan Lake population was the smallest(2.443). AMOVA analysis showed that the genetic variation among different populations was 10.47%, while the genetic variation within populations was 89.53%. Among the 5 wild populations, only the Tajima's D and Fu' Fs of the Yangtze River population were negative and significant, so it was speculated that the population had experienced population expansion.【Conclusion】The population of C. alburnus in the lower reaches of the Yangtze River have low haplotype diversity and high nucleotide diversity, and the genetic diversity is abundant. There is genetic differentiation among the populations, but the degree of differentiation is not significant. Therefore, follow-up studies need to continue to increase the number of wild populations of C. alburnus samples and survey waters, a comprehensive and systematic assessment of the status of germplasm resources in the lower reaches of the Yangtze River, to provide a scientific basis for the establishment of nature reserves and artificial proliferation and release.