天山一号冰川前沿生态系统真菌群落结构演替及分布格局

Community structure and succession of fungi in the forefront of Tianshan No. 1 glacier, China

摘要:

[目的]分析真菌群落结构和多样性随着一号冰川退缩前沿年代序列的变化，揭示真菌群落的演替轨迹及环境因子对群落组成的影响。[方法]采用宏基因组学研究方法，结合生物信息学和统计学分析技术，对取自一号冰川末端表面冰尘，底部和前沿14个样品进行总DNA的提取，ITS基因的扩增并使用Illumina Miseq平台测序，通过相关生物地理化学特性综合分析在不同年代序列下真菌群落结构及其演替规律。[结果]经测序，筛选和质控分析获得185103条raw reads，占78.3%的非单序列在97%的相似度聚类分析共得到300个操作分类单元（OTU），共划分为6个门：子囊菌门（Ascomycota，52.7%）、担子菌门（Basidiomycota，16.9%）、壶菌门（Chytridiomycota，15.1%）、接合菌门（Zygomycota，2.4%）和球囊菌门（Glomeromycota，1.2%）。从演替初期到后期阶段虽然子囊菌的序列数逐渐下降而担子菌出现缓慢上升趋势，但子囊菌随着土壤年代序列的增加始终为优势类群，壶菌在冰川底部和前沿基层普遍存在且丰度仅次于子囊菌和担子菌。我们在缺乏植被的最新退缩基层发现依靠自养型宿主存活的活体营养菌，如Taphrinomycetes、Urediniomycetes和Ustilaginomycetes。从冰川底部和前沿基层检测到丰度较高的酵母菌，而粪生真菌（coprophilous fungi）仅仅出现在冰川前沿基层，共23个操作分类单元。球囊菌仅在前沿部分样品中存在，有着十分狭小的生态位分布。[结论]一号冰川前沿随着年代序列的增加真菌群落存在明显的演替轨迹和多样性的显著变化，不同生态位真菌类群组成的相似性较低且都存在明显的指示性真菌类群。

Abstract:

[Objective] The objective of this study was to evaluate the influence of environment factors on fungal communities during succession periods along the chrono-sequence in forefront of Tianshan No. 1 glacier.[Methods] Fungal community composition in oligotrophic environment on the forefront of a receding glacier was analyzed by sequencing of 18S rRNA gene fragment of DNA samples from cryoconite and sub-and proglacial sediment near the glacier terminus.[Results] Fungal sequences obtained from zone represented 5 fungal phyla:Ascomycota (52.7%), Basidiomycota (16.9%), Chytridiomycota (15.1%), Zygomycota (2.4%) and Glomeromycota (1.2%). Although the proportion of Ascomycota outclass Basidiomycota-related sequences was identified in younger substrate, Basidiomycota sequences related to Microbotryomycetes, Tremellomycetes and Agaricomycetes increased gradually along the chrono-sequence. Representative sequences related to parasitic, pathogenic and airborne fungal lineages showed deposition of ecdemic fungi and anthropogenic activities directly or indirectly influenced fungal composition and spatial distribution in glacier ecosystem.[Conclusion] Our results suggest the forefront of Tianshan No. 1 glacier provide a favorable platforms for diversity and community succession of fungi adapted to oligotrophic, no vegetated and cold conditions. The different community structure was observed during succession periods along the chrono-sequence in forefront of Tianshan No. 1 glacier.