随机过程主导吕梁不同生态系统土壤真菌群落构建

Stochastic processes dominate the assembly of soil fungal communities in different ecosystems of Lüliang

摘要:

【背景】 群落构建机制是微生物生态学关注的热点问题，得出的结论在局域尺度下是否完全适用仍不确定。【目的】 在较小的局域尺度下对群落构建机制进行验证，补充相关理论的适用性。【方法】 以山西吕梁地区分布的森林、灌丛和草地生态系统中土壤真菌群落作为研究对象，探究不同生态系统真菌群落组成结构和构建机制的变化。【结果】 通过高通量测序和统计分析，表明土壤真菌群落在不同生态系统间表现出独特的生物地理分布格局，森林生态系统的Sobs、Ace和Chao1指数分别为699.50、835.22和838.36，显著高于其余2个生态系统(P<0.05)；通过网络分析及Zi-Pi值的计算，表明网络模块具有地区差异性，不同生态系统间关键物种数量和种类均出现显著变化。通过回归分析、中性群落模型构建，以及βNTI、RCbray值的计算，|βNTI|<2，森林、灌丛和草地生态系统的群落层面迁移率为0.003、0.001和0.001，出现显著的距离-多样性衰减分布格局(R=-0.059, P=0.018)，由此推断随机过程是本研究区真菌群落构建的主要驱动因子。【结论】 相较于优势物种[绿僵菌属(Metarhizium)、赤霉属(Gibberella)等]，关键物种[地孔菌属(Geopora)、木霉属(Trichoderma)等]参与了共生网络形成和群落构建过程，拥有更广泛的功能，对不同生态系统的适应性更强；在该局域尺度下，确定过程和随机过程均参与了群落构建，但随机过程占主导。本研究旨在为黄河流域吕梁地区不同生态系统间的保护措施提供一定的科学依据，为宏观生态学中理论应用的普适性提供更多的线索。

关键词:扩散限制;确定过程;真菌群落;群落构建;生态系统类型

Abstract:

[Background] The mechanism of community assembly is a hot topic in microbial ecology, and it remains uncertain whether the conclusions are completely applicable on a local scale. [Objective] To verify the community assembly mechanism on a small local scale and evaluate the applicability of relevant theories. [Methods] We compared the composition and assembly mechanisms of soil fungal communities in the forest, shrub, and grassland ecosystems in Lüliang, Shanxi. [Results] The results of high-throughput sequencing and statistical analysis indicated that the soil fungal communities presented different biogeographic distribution patterns in different ecosystems. The Sobs, ACE, and Chao1 indices of soil fungi in the forest ecosystem were 699.50, 835.22, and 838.36, respectively, which were higher than those of the other two ecosystems (P<0.05). The network analysis and Zi-Pi values showed that the network modules had regional differences, and the number and composition of keystone species were different among different ecosystems. According to the regression results, neutral community model analysis results, |βNTI|<2, RCbray values, the community migration rates are 0.003, 0.001 and 0.001, and a significant distance-delay distribution pattern (R=-0.059, P=0.018), we hypothesized that stochastic processes dominated the assembly of fungal communities in this study area. [Conclusion] The keystone species (Geopora, Trichoderma, etc.) are involved in the symbiotic network formation and community assembly and demonstrate broader functions and stronger adaptability to different ecosystems than the dominant species (Metarhizium, Gibberella, etc.). On this local scale, both deterministic and stochastic processes drive community assembly, with the former being dominant. This study aims to provide a scientific basis for the protection of different ecosystems in Lüliang of the Yellow River basin and enrich the clues for the universal application of theories in macroecology.

Key words:diffusion limitation;deterministic process;fungal community;community assembly;ecosystem types