水库瘤棘砂壳虫分子系统地理学研究

Free-living protozoa are an important and diverse component of aquatic ecosystem and play fundamental roles in material cycles and energy transfer due to their small size and high abundance and diversity. Difflugia tuberspinifera is an endemic species of China and is common in freshwater reservoirs of south China. However, the population genetic diversity and molecular biogeography of this species are largely unknown. Therefore, this project will use single-cell molecular biological technologies and modern multiple statistical methods to study the morphology and DNA sequences based on over 10000 individual isolates from 20 typical reservoirs in the Yangtze River, Minjiang River, Jiulong River and Pearl River watersheds. The objects of this project are: 1) to investigate the population resource of D. tuberspinifera among different regions, and reveal the distribution pattern of genetic diversity based on both nuclear ribosomal ITS and mitochondrial COI sequences; 2) to quantify the relationships and contributions of region geographical, local ecological and biological factors to population structure and spatial genetic divergence on different spatial and temporal scales; 3) to illustrate the evolutionary relationships between the spinose type and spineless type of D. tuberspinifera, and reveal the dominance mechanism of spinose population in Yangtze River and Pearl River watersheds on ecological and evolutionary views. This project will provide new evidences for the diversity and biogeography of the single-celled animals, and scientific data for the water resource protection, environment monitoring, paleoenvironment reconstruction.

瘤棘砂壳虫是我国特有原生动物，广泛分布于我国南方水库，具有重要的生态功能，面临富营养化等严重威胁。然而，我们对瘤棘砂壳虫遗传多样性时空分布格局和种群遗传分化过程与影响因子的认知还属于空白。本项目拟以长江、闽江、九龙江、珠江流域30座水库作为研究区，以分子系统地理学为核心，运用单细胞分子生物学技术和多元统计新方法对瘤棘砂壳虫进行研究：1）基于形态结构、细胞核ITS序列和线粒体COI序列研究种群遗传多样性，区域尺度上揭示瘤棘砂壳虫的地理分布格局；2）定量评估瘤棘砂壳虫种群结构变化和遗传分化与地理因子、环境因子的关系，揭示地理和环境因子对种群结构和基因流的贡献比例；3）综合基因组、多基因序列阐释不同形态型之间的进化关系，揭示瘤棘砂壳虫种内系统地理格局形成过程与演化机制。本研究将为单细胞动物多样性和生物地理学提供新证据，并为水生态保护、环境监测、古环境重建等提供基础资料和科学依据。

瘤棘砂壳虫是东亚特有原生动物，广泛分布于我国东南地区水库。然而，我们对瘤棘砂壳虫种群时空分布格局及其生态影响因子的认知还非常有限。本项目通过对我国典型流域30座水库瘤棘砂壳虫的采集，综合利用壳体形态特征和DNA序列分析了瘤棘砂壳虫的地理分布，研究了有壳虫等微型生物群落对环境变化的响应。主要结果如下：1）首次成功实现了瘤棘砂壳虫的室内传代培养；2）基于COI基因序列揭示了瘤棘砂壳虫种群遗传多样性，发现瘤棘砂壳虫种群和遗传多样性时空分布与温度密切相关；3）利用转录组方法探究了瘤棘砂壳虫对温度适应的分子机制，比较分析了差异表达基因；4）基于长期观测数据解析了河流水库系统有壳虫、变形虫的群落构建机制，强调了中性过程对群落构建的重要作用；5）评估了过去2500年自然和人为变化对泸沽湖有壳虫群落的影响；6）对澳洲砂壳虫进行了描述；7）揭示了蓝藻水华发生和消退过程中稀有浮游生物的动态及其重要作用。截止到2020年12月，本项目资助下已经在Microbiome、The ISME Journal、Water Research、Environment International、European Journal of Protistology等期刊累计发表SCI论文14篇（包括1区TOP期刊论文8篇），授权发明专利1项，提交会议摘要25篇；培养博士生5名、硕士生1名。本项目研究结果为单细胞生物多样性和微生物限制性地理分布提供了新证据，对稀有种的研究拓展了微食物网浮游生物生态的内容，为水生态保护、环境监测、环境重建等提供了基础资料和科学依据。