热带海草泰来草沉积物真菌的群落结构、功能与分子生态网络研究

Community structure,function,and molecular ecological network of fungi in the tropical seagrass Thalassia hemprichii sediment

真菌是海草床生态系统的重要组成部分,它们在维持海草健康和生态系统碳氮等营养元素循环方面发挥着重要作用。为了阐明海草床生态系统真菌的群落结构及功能,文章以热带海草泰来草(Thalassia hemprichii)沉积物为主要研究对象,通过Illumina Miseq高通量测序技术分析海南岛和西沙群岛两个研究区域泰来草沉积物真菌的群落结构与物种多样性,并利用FUNGuild数据库对真菌营养类型进行预测和功能注释。研究结果表明,子囊菌门(Ascomycota)(相对丰度24.30%~76.20%)和担子菌门(Basidiomycota)(相对丰度4.98%~52.24%)为两个研究区域的共同优势种群,但是子囊菌门真菌的相对丰度在两个研究区域间存在显著性差异(p<0.05),两个区域内共有的海草沉积物真菌分类操作单元(operational taxonomic units,OTUs)数量占比为5.15%,其相对丰度为31.19%。两个研究区域泰来草沉积物真菌群落的α多样性指数中的香农指数(Shannon)和系统发育多样性(phylogenetic diversity)以及β多样性之间都存在显著性差异(p<0.05)。FUNGuild功能预测分析表明,大部分真菌的营养类型尚未确定(72.11%~91.92%),其中能够确定的主要营养类型为共生营养型(symbiotroph)、腐生营养型(saprotroph)和病理营养型(pathotroph),3种营养型可以进一步分为41个生态功能群。基于随机矩阵理论(random matrix theory,RMT)构建的两个研究区域海草泰来草沉积物真菌分子生态网络结果显示,海南岛泰来草沉积物真菌网络结构更加复杂,其平均聚类系数更高、平均连通度更高、密度更高,该真菌群落可能对外界环境变化更为敏感,而西沙群岛海草沉积物真菌群落的模块化程度更高,其中粪壳菌纲(Sordariomycetes)为分子生态网络中的关键类群。

Fungi are essential components of seagrass ecosystems,and they play important roles in maintaining seagrass health and nutrient cycling in the ecosystem.To elucidate the fungal community structure and their functions in seagrass sediment,we used Illumina MiSeq high-throughput sequencing technique to investigate the fungi in sediments of tropical seagrass Thalassia hemprichii in Hainan Island and Xisha Islands,respectively.FUNGuild database was introduced to predict fungi trophic types and annotate fungi guilds.Results showed that phylum Ascomycota(relative abundance 24.30%~76.20%)and Basidiomycota(relative abundance 4.98%~52.24%)were the dominant phyla in the two study areas,but the relative abundance of phylum Ascomycota was significantly different between the two study areas(p<0.05).The percentage of OTUs numbers in seagrass sediment fungi shared in the two regions was 5.15%,and their relative abundance was 31.19%.In addition,there were significant differences between the Alpha diversity index(Shannon and Phylogenetic diversity)and Beta diversity of the fungal communities of seagrass sediments in the two study areas(p<0.05).The FUNGuild functional prediction analysis revealed that the main fungal trophic types were undetermined(relative abundance 72.11%~91.92%).The trophic types of the rest fungi were Symbiotroph,Saprotroph,and Pathotroph,and these three trophic types could be further divided into 41 functional guilds.Network analysis for fungal groups based on random matrix theory(RMT)showed that the fungi network structure of seagrass T.hemprichii sediment in Hainan Island was more complex,with higher average clustering coefficients,longer average path lengths,and higher densities.These fungal communities may be more sensitive to environmental change.While the fungal communities of seagrass T.hemprichii sediment in Xisha Islands were more modulized,the fungus belonging to Class Sordariomycetes was the key taxon in the molecular ecological network.This study provides essential primary data and theoretical support for further study on the structure and function of fungi in seagrass ecosystems,microbial resource mining,and ecological applications.