利用环境DNA 评估长江中下游濒危物种江豚的种群分布与退化

Environmental management of resources and wild species requires a comprehensive understanding of the distribution and abundance of individual species and patterns of their assembly into ecosystems. Making biodiversity assessments difficult however, is the reality that many taxa are difficult to detect in nature, especially when rare, during particular time periods (e.g. non-breeding season) or developmental stages, often with a high potential to bias study outcomes. Conventional monitoring efforts usually involve visual or sometimes acoustic detection, but these methods are labour-intensive, invasive, expensive, non-standardized, and prone to false-negative-detection rates. Aquatic ecosystems are among the most vulnerable to environmental degradation and global species extinctions yet lack sufficient data on species abundance and distribution, hindered predominately by costs incurred through traditional surveys. Nonetheless, a key component for understanding freshwater and marine ecosystems, and for implementing science-based management for such habitats, is comprehensive environmental monitoring programs. Thus more efficient, cost-effective, and sensitive methods would propel aquatic ecosystem biodiversity assessments and improve the efficacy and scope of baseline ecological data collection, helping to frame cogent policy and monitoring efforts such as ecological restoration. . Molecular genetic markers have proved invaluable for environmental management practices, and in recent years advances utilizing DNA from the environment (eDNA) has gained traction in the scientific community. Deposited by way of metabolic waste, sloughed cells, and carcasses, eDNA has been found to be an accurate indicator of contemporary habitat occupancy for a variety of taxa in myriad habitats. The use of eDNA to environmental and conservation management is still only in its infancy, with most applications being directed towards abundant and invasive species. Yet for endangered species, detecting localized populations and mapping their distributions in fine detail is of utmost important for the maintenance of species integrity, and here eDNA could assist scientists conducting environmental sampling.. For my research I propose to use eDNA to detect and monitor populations of the endangered Finless Porpoise (Neophocaena phocaenoides asiaorientalis) in the lower Yangtze. With full mitochondrion sequences already available online, and combined with innovative eDNA techniques to quantify species abundance, and co-occurring community constituents, this research has the potential to revolutionize environmental sampling, conservation management, and community assessments in China.

濒危水生物种分布和丰度等数据,对于水生生态系统生物多样性的评估以及物种保护具有重要意义。传统评估主要依赖于分类学知识和大量的人力、物力的投入，调查成本高,且容易出现片面的研究结果。eDNA技术可作为一种高效率、低成本和高灵敏度的方法，进行水生生态系统生物多样性的评估。eDNA在环境管理中应用仍处于起起步阶段，且大多数应用都集中于种群生物量的测定及入侵物种。本研究利用eDNA技术进行取样，对长江流域濒危物种江豚进行种群分布研究。研究将用eDNA监测长江下游的江豚，利用已有的完整线粒体序列和非侵害性的eDNA技术测量物种丰富度，再结合已知的群落组成，对长江流域的濒危物种江豚进行生物多样性评估，进一步阐明长江流域群落中江豚猎物种群数量的变化与江豚数量下降之间的关系。研究成果有望提升的现有群落评估方法，为江豚保护措施的制定提供科学依据。

环境DNA（eDNA）是一种收集环境样品和扩大生态系统内物种或群落遗传特征的方法。对于难以取样的地方（如水生环境）中稀有或隐蔽物种，这是一种特别有用的技术。虽然这种技术对于保护工作是有希望的，但它仍然是一种新方法，科学家正在针对不同的物种和情况进行优化。我的研究旨在设计、优化和验证eDNA方法，以帮助严重濒危的长江江豚（Neophocaena asiaeorientalis asiaeorientalis）的保护工作（发生，范围和栖息地使用）。我们成功地设计了12种可以与eDNA一起使用的物种特异性引物，然后着手验证这种方法在湖北天鹅洲自然保护区内的准确性，这个自然保护区大约有58只长江江豚。科学家越来越依靠保护区来协助保护生物多样性，但这些地区的功效很少得到系统的评估。尽管如此，适应性管理策略最大限度的保护成功往往依赖于了解其中的种群的时空动态。定量聚合酶链式反应（qPCR）检测eDNA可以提供关于生物丰度的信息。我们通过eDNA浓度来描述长江江豚在中国湖北省天鹅洲国家级自然保护区内整个季节和水文深度的发生、范围及使用情况。我们发现夏季深水中的eDNA浓度显著高于地表水体，而在繁殖季节（春季），eDNA信号具有特定的位置，并限制在保护区核心区域。然而，繁殖期后eDNA的浓度在保护区种广泛存在，包括以前被认为是该物种不常出现的位置。我们的结果展示了长江江豚在保护区中繁殖期后不同位置、深度、季节的出现情况，通过eDNA和qPCR，我们能够以更高效、节约成本的方式评估长江江豚对保护区的使用情况。关于长江江豚eDNA的研究我们正扩大到鄱阳湖和长江下游地区。 我们进一步致力于利用eDNA样本的基因组分析（metabarcoding）来调查种群丰度是否与猎物群落（如鱼类）丰度有关。 我的研究是通过eDNA阐明栖息地使用的细微差别，可能有助于为长江江豚和其他物种设定实用的保护目标。

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