水淹厌氧环境丛枝菌根真菌多样性维持机制

Understanding the mechanisms that maintain biodiversity has long been a central aim in ecological research, and attentions have been paid on debates and integration of niche process and neutral process. Recently studies showed that while aerobic arbuscular mycorrhizal fungi are widespread under anaerobic, waterlogged conditions, the mechanisms structuring arbuscular mycorrhizal fungal communities under waterlogged conditions remains unclear. Based on previous studies, we hypothesized that "niche variation is more important than neutral processes in maintaining arbuscular mycorrhizal fungal diversities under waterlogged conditions". In this study, plant roots will be sampled under waterlogged conditons in a marshland along a waterlogging time gradient. Influences of waterlogging on AMF species composition and abundance will be identified with 454 pyro-sequencing. Plant communities and soil physical and chemical properties will also be investigated. The relative importance of niche variation and neutral processes in structuring arbuscular mycorrhizal fungal communities will be identified basing on taxonomic diversity and phylogenetic diversity. Models such as zero-sum multinomial (ZSM) distribution, partitionin of β-diversity, Mantel tests and RDA, together with community phylogenetic structure will be used to identify whether niche process or neutral process is more important in maintaining AMF community. Results of this project will reveal mechanisms of arbuscular mycorrhizal fungal community construction and biodiversity maintenance under waterlogged conditions, and will provide new insights into ecological community construction theory.

生物多样性维持机制居于生态学研究的重要地位，生态位过程与中性过程的争论与整合引起了广泛关注。最新研究表明好氧的丛枝菌根真菌在淹水厌氧环境广泛分布，其多样性维持机理有待揭示。基于国内外研究和申请者前期调查，申请者提出假设"水淹胁迫驱动AMF多样性维持机制由中性过程转换为生态位过程"。本项目计划在野外季节性水淹滩地，沿水淹时间梯度进行取样，通过454 测序的手段分析淹水滩地 AMF 群落物种组成及多度，揭示水淹驱动 AMF 群落的变化方向，结合环境因子和宿主植物群落信息，从分类多样性和谱系多样性两方面入手，利用中性理论和生态位理论相关模型(零和模型，β多样性指数的分解、Mantel test 和 RDA 等)，以及分析群落物种间谱系亲缘关系，阐明生态位过程和中性过程在 AM真菌多样性维持中的相对重要性。研究结果将揭示淹水胁迫下 AMF 群落构建和稳定维持机理，丰富生物多样性维持机制的理论体系。

本项目主要期望解决AMF 群落物种组成响应水淹的变化规律及多样性维持机制的问题。本研究通过解析滩地涨水前后AMF群落结构，基于多度模型拟合的方法和群落进化关系的方法，研究了水淹前后AMF 群落构建机制的变化。研究结果明确了水淹前后AMF群落发生显著变化，揭示水淹前后AMF群落构建过程发生了由中性过程向生态位过程的转变。在经历一个短期的（15天）水淹后，植物根内AMF物种丰富的是升高的，这与一般认为的“水淹厌氧环境抑制好氧的丛枝菌根真菌”的观点不一致，其原因可能在于，水淹之后，对氧气具有较强竞争能力的AMF受到抑制，而对氧气竞争能力不强、但具有较强耐受性的AMF则趁机发展起来，即竞争释放（competitive release）作用导致了水淹之后AMF物种丰富度的升高。这些结果丰富了物种多样性维持机制理论。