不同菌根类型热带树木根系内生真菌多样性及其群落特征

Diversity and community characteristics of endophytic fungi in the roots of tropical trees with different mycorrhizal types

摘要:

树木可与菌根真菌形成互利共生体，不同菌根类型通过调控树木的生理和根系微环境对内生真菌群落结构产生影响，成为驱动热带森林土壤和微生物互作网络的关键环节。然而，目前关于不同菌根类型如何调控热带树木根系内生真菌的多样性及其群落组成尚未有清晰认识。目的 探究不同菌根类型对热带树木根系内生真菌多样性、群落结构及其驱动因素的影响，系统解析菌根类型如何通过调控根系性状和根际环境来影响内生真菌群落的组成与多样性，并识别其中的关键驱动因子。方法 以中国西双版纳热带森林中3个中国生态系统研究网络(China Ecosystem Research Network, CERN)研究站点的3 773组土壤及根系数据为基础，整合并构建了树种水平的分析数据集。该数据集包含119棵丛枝菌根(arbuscular mycorrhizas, AM)树下的54个AM树种、31棵外生菌根(ectomycorrhizas, ECM)树下的12个ECM树种的根系性状、土壤理化性质以及根系内生真菌操作分类单元(operational taxonomic unit, OTU)丰度，并以此为基础开展研究。结果 AM树木根系内生真菌的α多样性显著高于ECM树木(P<0.05)。菌根类型影响根系内生真菌群落的优势类群，子囊菌门(Ascomycota)在AM树木根系中占比最高，相对丰度为43.17%；担子菌门(Basidiomycota)在ECM树木根系中占比最高，相对丰度为65.17%。共现网络分析表明，AM树木根系内生真菌网络较为密集，ECM树木根系内生真菌网络更为模块化。土壤是驱动AM树木根系内生真菌群落的主导因子，而ECM内生真菌群落则主要受根系性状与土壤因子的共同调控。土壤磷是影响AM与ECM树木根系内生真菌群落的关键因子。结论 在热带森林生态系统中，AM驱动树木形成物种丰富、互作紧密的根系内生真菌群落，其构建过程主要受土壤因子调控；而ECM树木则形成专一化的共生真菌体系，其构建受宿主根系性状与土壤因子协同调控。此外，土壤磷是驱动2类树木根系内生真菌群落形成的关键因子。

Abstract:

Trees can form mutualistic symbionts with mycorrhizal fungi. Different mycorrhizal types affect the community structure of endophytic fungi by regulating tree physiology and root microenvironment, thus becoming a key link driving the interaction network between soil and microorganisms in tropical forests. However, the mechanisms by which different mycorrhizal types regulate the diversity and community composition of endophytic fungi in tropical tree roots are still not fully understood.Objective To explore the effects of different mycorrhizal types on the diversity and community structure of root endophytic fungi in tropical trees, as well as their key driving factors, systematically clarifying how mycorrhizal types affect the composition and diversity of endophytic fungal communities by regulating root traits and rhizosphere environment, and identifying the key driving factors.Methods On the basis of 3 773 sets of soil and root data collected from three research sites of Chinese Ecosystem Research Network (CERN) in Xishuangbanna tropical forest, China, we integrated and constructed a dataset at the tree species level. This dataset encompassed data of the root traits, soil physical and chemical properties, and the operational taxonomic unit (OTU) abundance of endophytic fungi in the roots of 119 trees (54 species) with arbuscular mycorrhizas (AM) and 31 trees (12 species) with ectomycorrhizas (ECM), and it was then used for the research.Results The alpha diversity of endophytic fungi in the roots of AM trees was higher than that of ECM trees (P<0.05). Mycorrhizal types affected the dominant groups of root endophytic fungi. Ascomycota had the highest relative abundance (43.17%) in the roots of AM trees, and Basidiomycota had the highest relative abundance (65.17%) in the roots of ECM trees. The co-occurrence network analysis showed that the endophytic fungal network was denser in the roots of AM trees and more modular in roots of ECM trees. Soil properties were the dominant driving factors for the endophytic fungal communities in the roots of AM trees, while the endophytic fungal communities in the roots of ECM trees were regulated jointly by root traits and soil properties. Soil phosphorus was a key factor affecting the endophytic fungal communities in the roots of AM and ECM trees.Conclusion In tropical forest ecosystems, AM drives trees to form species-rich and closely interacting endophytic fungal communities in the roots, and the assembly process is mainly regulated by soil factors. ECM trees form a specialized symbiotic fungal system, whose construction is regulated by both root traits and soil factors. In addition, soil phosphorus is the core factor driving the formation of endophytic fungal communities in the roots of the two types of trees.