三峡水库蓄水运行对中华鲟种群生存力影响的遗传随机性分析

Since the construction of Gezhouba Dam, the number of individuals in Chinese sturgeon breeding population in the Yangtze River has markedly declined year by year. Moreover, changes in hydrological regime induced by the impoundment of the Three Gorges Reservoir might cause more negative effects on the natural reproduction of Chinese sturgeon. In order to develop effective measures for Chinese sturgeon conservation, it is necessary to assess the ecological effects of its environmental stressors. Population Viability Analysis is a method for analysis of how random factors affect the extinction of small populations. It is developed rapidly in the last decade and has been used widely. This study intends to quantify the genetic stochasticity to the Population Viability Analysis of Chinese sturgeon. We will establish a method based on genetic similarity contrast to reconstruct kinship of Chinese sturgeon breeding population and estimate breeding population size. Genetic dynamic model will be built for assessing the effects of inbreeding depression and genetic drift on Chinese sturgeon population within a certain time. In addition, we will conduct a sensitivity testing using hydrological regime parameters for analyzing its correlation with natural reproduction of Chinese sturgeon. This testing will provide an indirect scientific basis for exploring the mechanisms of how Chinese sturgeon breeding population responds to environmental stress caused by the impoundment of the Three Gorges Reservoir.

自葛洲坝截流后，长江中华鲟繁殖群体的数量逐年减少，而三峡水库蓄水运行后造成的水文情势变动，则可能对中华鲟的自然繁殖产生叠加的生态效应。为了制定有效的中华鲟物种保护措施，应首先实现对其环境胁迫因子的生态效应的准确评估。种群生存力分析是目前国内外常用的用于分析评估随机干扰因素对小种群的生态效应的技术手段。本项目拟将遗传随机性量化到中华鲟种群生存力分析。首先，建立基于遗传相似度比对的中华鲟天然繁殖群体家系区分方法，获得天然繁殖群体遗传背景和繁殖群体规模。之后，构建长江中华鲟种群生存力的遗传动态模拟模型，分析近交衰退和遗传漂变等因素对种群在一定时间内的存活状况及进化潜力的影响。最后，利用模型中的灵敏度分析研究中华鲟自然繁殖情况和坝下江段水文情势变动的相关耦合程度，探讨繁殖群体对三峡水库蓄水运行导致的环境胁迫的响应机制。

利用7对遗传背景和倍性清晰的微卫星分子标记研究了中华鲟4个繁殖家系的遗传信息传递模式，进一步对71尾中华鲟天然繁殖群体样本进行了遗传家系区分，划分结果显示71尾中华鲟繁殖群体样本属于6个亲属团体。同时，利用中华鲟线粒体D-LOOP引物分析了124份中华鲟卵DNA样品，结果显示其至少来源于16尾中华鲟雌鱼个体。综合采用水下摄影、水下声呐探测、解剖食卵鱼等多种途径开展了2013-2015年度中华鲟自然繁殖状况监测，连续3年均未监测到中华鲟自然繁殖行为。初步建立了中华鲟环境DNA检测方法，并成功应用于混合循环水养殖水样和中华鲟半人工池塘水样中。基于2000-2015年的监测结果，构建VORTEX模型对两个场景下长江中华鲟未来的种群动态进行模拟，结果表明，在最佳生存力场景下，中华鲟种群在39年后完全灭绝；在最差生存力场景下，中华鲟种群在26年后完全灭绝。对不同年度中华鲟自然繁殖状况对流量、水温过程和泥沙含量之间的响应开展了分析，结果表明中华鲟自然繁殖对水文条件变化的响应主要表现在水温过程的响应。