阻隔和生境萎缩对长江上游圆口铜鱼有效群体大小的生态学影响

The largemouth bronze (Corieus guichenoti), is a typical fish of river migratory in the upperstream of the Yangtze River. Owing to strong dependence to flowing-water habitat in the life history, C.guichenoti shows ecological sensitivity to damming and habitat fragmentation. Thus, it is important to assess ecological influence caused by hydropower projects. However, lacking of sufficient information of population biology and genetics may lead to inaccurate evaluation on negative effects of hydropower projects on this species during different stages of its life history. Although there have been some studies on conservation of population diversity and genetics, further studies research are still needed. In the study, our research take the breeding stock of C.guichenoti as our targets. Using highly polymorphic SSR loci, genetic structure of these breeding stocks were diagnosed. And effective population sizes (Ne) that can significantly determine population genetic diversity and evolutionary potential were also assessed. Meanwhile, combing with some ecological hydrological factors (temperature, flow velocity and discharge) and some key genetic index (genetic diversity, gene flow, and effective population size), influence of damming barrier on genetic diversity of C.guichenoti were comprehensively analyzed using Isolation-By-Distance model and correlation theory. The study can provide a new methods and perspective to assess and predict ecologcial effects on C. guichenoti under construction of cascaded hydropower projects. Also, it is promising not only to promote utilization of population genetics in eco-hydrology, but also to provide supportive information for the germplasm protection, population restoration, the artificial reproduction and releasing of endemic fishes.

圆口铜鱼是长江上游典型的河道洄游性鱼类，其繁殖群体对流水生境具有较强的依赖性，因此，该物种对水利工程引起的阻隔与生境萎缩等胁迫效应具有独特的生态敏感性。国内在圆口铜鱼物种保护与研究方面已有一定基础，但缺乏生物学和遗传学基础资料的长期积累，无法准确地描述工程对圆口铜鱼关键生活史阶段的影响程度。本项目以长江上游圆口铜鱼繁殖群体为研究对象，利用微卫星标记对繁殖群体遗传结构进行分子诊断，估算对种群遗传多样性维持有重要作用的有效群体大小。在此基础上，利用距离隔离IBD模型和相关性分析原理，开展微观遗传数据（有效群体大小和关键遗传参数）与宏观水文因子（水文、流速、流量等）的关联性分析，并结合其生活史特征，探讨圆口铜鱼繁殖群体对工程建设和运行的响应机制。该项目为评估和预测梯级水利工程对圆口铜鱼物种生存的影响提供一种新的分析方法和研究实例，研究结果对圆口铜鱼等长江上游特有鱼类的物种保护具有现实意义。

圆口铜鱼是长江上游典型的河道洄游性鱼类，对流水生境具有较强的依赖性，对水利工程引起的阻隔与生境萎缩等胁迫效应具有独特的生态敏感性。本项目以长江上游特有鱼类圆口铜鱼为研究对象，采用微卫星分子标记对种群遗传结构开展研究，估算对种群遗传多样性维持其主要作用的有效群体大小。取得的主要研究结果如下：.（1）分离鉴定了44个圆口铜鱼多态性微卫星位点。经过群体有效性检验，全部位点的观测杂合度和期望杂合度范围分别为0.09-0.94和0.15-0.92，仅有2个位点偏离哈迪-温伯格平衡；44个位点中，有32个位点具有高度多态性特征，为今后开展圆口铜鱼遗传变异研究提供了有力的工具。.（2）开展了金沙江中下游及雅砻江干流圆口铜鱼4个不同江段群体（268个个体）的遗传特征研究，测定了群体间基因流水平（Nm为8.33-13.91，平均值为9.19）、群体变异来源（98.94%的变异来源于群体内）以及遗传分化水平（Fst=0.0260），结果表明圆口铜鱼种群的遗传多样性水平较高，尚未因工程阻隔和生境萎缩而表现出显著的遗传分化。项目还采用距离隔离模型开展了圆口铜鱼群体的遗传距离和地理距离相关性研究，结果显示遗传距离和地理距离无显著相关，这些结果均可为圆口铜鱼保护和种群恢复提供数据支撑。.（3）开展了圆口铜鱼4个不同江段群体（268尾个体）的有效群体大小研究，初步估算了雅砻江金河江段群体、金沙江格里坪江段群体、金沙江皎平渡江段群体和金沙江永善江段群体的有效群体大小分别为1062、1608、840以及1148尾。该结果将在选育圆口铜鱼繁殖群体数量方面具有一定的实用价值。.本研究表明，维持一定量的有效群体大小数量，将有利于圆口铜鱼遗传多样性水平的维持。加强金沙江中下游自然群体和圈养群体的持续监测，获得种群遗传结构年际变化的基础数据，建立遗传信息数据库，深入开展有效群体大小和繁殖群体的遗传管理研究将是圆口铜鱼保护与研究的主要方向之一。