基于eDNA技术的渭河浮游动物多样性及关键种生态位特征

环境DNA（eDNA）技术作为水生态系统生物多样性监测的新手段，能够从微观角度对生物群落结构特征进行分析.基于渭河干流eDNA浮游动物OTUs分类信息数据及水环境参数，采用多样性指数、非度量多维尺度分析、聚类分析和关联网络分析等方法，探究了浮游动物的多样性和群落结构变化特征，揭示了关键种的生态位分化及其环境适应性.结果表明，浮游动物群落在物种组成、丰度、多样性和空间异质性方面均存在显著差异（P<0.01）.Chao1指数、ACE指数、Shannon指数和Simpson指数的均值分别为22.25、22.38、2.32和0.68，下游生物多样性明显高于上游.群落中的关键种与其他物种间连接度较高，具有高节点度、中心性和模块化特征.关键种（类）的OTUs生态位宽度B_i变化范围为0.38~0.80，中生态位种类占全部关键种（类）的63%，生态位重叠程度总体较高.水环境要素与浮游动物群落结构和生态位变化密切相关，其中总氮和水温是其主要限制因子，对浮游动物群落结构变化具有重要影响.

Diversity of Zooplankton and Niche Characteristics of Keystone Species in the Weihe River Based on eDNA

Environmental DNA(eDNA), a new tool for monitoring the biodiversity of aquatic ecosystems, is able to analyze characteristics of biodiversity from a microscopic perspective. Based on eDNA data collected from the Weihe River, diversity indexes, non-metric multidimensional scaling, cluster analysis, and correlation network analysis were employed to explore the diversity and community structure of zooplankton focusing on the niche differentiation of keystone species and environmental adaptability. The eDNA approach identified three types of zooplankton including Rotifera, Cladocera, and Copepoda, among which the dominant species was Brachionus calyciflorus. The zooplankton community shows significant differences in species composition, abundance, diversity and spatial distribution characteristics(P<0.01). The average values of the Chao1 index, ACE index, Shannon index, and Simpson index were 22.25, 22.38, 2.32, and 0.68, respectively. The downstream biodiversity is significantly higher than in the upstream area. Non-metric multidimensional scale analysis and hierarchical cluster analysis further showed that the zooplankton community structure shows distinct regional differences. The keystone species in the community have a high degree of connection with other species, with a high node degree, centrality, and modularity. The niche breadth(B_i) of the operational taxonomic units(OTUs) of the keystone species varied from 0.38 to 0.80. The medium niche species accounted for 63% of all keystone species. The average niche overlap index(Q_ik) was 0.72, and the degree of overlap was generally high. RDA analysis further identified that water environmental variables were closely related to changes in the zooplankton community structure and niche differentiation. For example, total nitrogen and water temperature were the main limiting factors, which play important roles in shaping the zooplankton community structure.