海岸带盐沼湿地线虫多样性的纬度梯度研究

Global patterns in biodiversity and their underlying mechanisms are among the most exciting topics for modern ecology and biogeography. Understanding whether and how community structure changes with latitude will become an important predictive tool for assesing how these communities will respond to climatic changes in the future. Although soils are recognized as one of the most species rich animal habitats on earth and soil organisms play important roles in regulating ecosystem-level processes, most biodiversity research has focused on aquatic and aboveground organisms and few attempts to know about geographic patterns of soil organisms and their environmental determinants. Nematodes are the most abundant metazoan taxon, which are assumed to function as regulators of decomposition and mineralization processes and play a central role in the detrital food web. In order to reveal the latitudinal gradients in diversity of soil nematodes living in coastal salt marshes, this project is planned to examine nematodes from 20 salt marshes along the coast of China. We will combine DGGE analysis and traditional morphological identi?cation technique to assess the community phylogenetic diversity and analyze the species and function diversity. In this study we will also explore the environmental determinants for nematode diversity. These results have implications for predicting potential impacts of climate change on diversity patterns.

生物多样性大尺度分布格局及其成因是宏观生态学和生物地理学研究的核心内容之一，对于理解生物群落组成及多样性与区域环境之间的联系，揭示全球变暖对生物的潜在影响具有十分重要的意义。土壤生物类群庞大，在很大程度上调节着生态系统功能，然而有关土壤生物多样性的纬度变异研究相对欠缺。线虫是土壤生态系统中种类繁多、数量巨大的优势动物类群，发挥着重要的生态功能。本项目将以我国海岸带盐沼土壤线虫为研究对象，采用形态分类与分子技术相结合的方法，分析各纬度线虫群落的遗传谱系结构、物种多样性和功能群组成，多层次研究土壤线虫多样性的纬度分布格局，探讨其与气候等环境因子的关系，为进一步完善全球生物多样性分布格局的理论体系提供重要的基础资料，为预测全球气候变化的影响提供参考。

为揭示我国海岸带盐沼湿地土壤线虫的谱系多样性、物种多样性和功能群结构的纬度梯度格局及其成因，我们以太平洋沿岸20 °N 到40 °N之间16个地点的盐沼湿地土壤线虫为研究对象，采用经典形态分类与现代分子技术相结合的方法，对其谱系结构、生态宽度和生活史对策进行多层面的研究，并采用多元回归和相关分析，探讨线虫纬度格局与气候等环境因子的关系。研究发现我国海岸带盐沼湿地线虫的谱系多样性指数（AvTD和AvPD）随纬度的增加而增加，而物种多样性随纬度的增加而降低，表明在低纬度地区盐沼湿地线虫群落内部物种间的亲缘关系更为相似。随着纬度的升高，线虫中选择性沉积食性类群的相对丰度降低，而非选择性沉积食性类群的相对丰度增加。同时，线虫群落内机会主义者所占比例随纬度的增加而下降，但拓殖者的纬度格局与此相反。上述结果表明，在低纬度地区海岸带盐沼湿地线虫的摄食生态位宽度更为狭窄，食性更为特化；而高纬度区域由于环境变化剧烈，则更有利于生活史长、生存竞争能力强的k-对策者在群落内占据优势。相对于植被类型，各纬度的年均温以及土壤pH对于线虫群落结构的影响更为重要。本项目首次从摄食选择性和生活史对策角度探讨线虫的纬度格局，揭示相对于高纬度而言，生活于低纬度的生物群落对生境和气候变化的反映更为敏感，这为完善全球生物多样性的分布格局的理论体系提供了重要资料，也为预测全球气候变化和生物多样性保护提供了重要启示。