亚高山草地土壤原生生物群落结构和多样性海拔分布格局

Community structures and diversity patterns of the soil protist communities along an altitudinal gradient in a subalpine grassland

生物多样性分布格局与维持机制即群落构建机制,是群落生态学研究的热点领域。微生物生态学中的一个关键问题是量化确定性过程和随机过程对微生物群落构建的相对贡献。尽管原生生物是土壤微生物群落中重要的组成部分,在微生物食物链中扮演着关键角色,但与细菌和真菌相比,目前对原生生物群落构建机制知之甚少。运用Illumina Miseq高通量测序技术,分析了五台山亚高山草地生态系统(海拔2000—3061 m范围内)土壤原生生物群落组成和多样性维持机制。结果表明,四个海拔梯度的土壤共获得有效序列520673条,分属于8个超群、24个门、65个纲、125个目、222个科和350个属。门水平上,丝足虫门(Cercozoa)、褐藻门(Ochrophyta)、纤毛门(Ciliophora)和顶复门(Apicomplexa)为主要优势类群。LEfSe分析显示,17个生物标志物对海拔梯度非常敏感,不同海拔梯度富集了不同的原生生物种群。尽管海拔对土壤原生生物群落的α多样性没有显著影响,但非度量多维尺度分析(NMDS)和相似性分析(ANOSIM)结果表明,原生生物群落组成和结构在海拔梯度上存在显著的差异(P<0.05)。冗余分析(RDA)显示海拔、土壤含水量、总氮和植物丰富度指数与原生生物群落结构存在显著相关性(P<0.05)。方差分解分析(VPA)和偏Mantel分析表明环境因子和空间变量对原生生物群落海拔分布格局均有显著影响,但是环境因子的相对作用(7.9%)明显大于空间变量(1.8%)。土壤原生生物群落之间的Bray⁃Curtis距离与海拔距离呈显著正相关关系(P<0.05),说明选择过程可能是亚高山草地土壤原生生物群落分布格局的主要驱动因素。零模型分析进一步证实了确定性过程在原生生物群落构建中的相对作用大于随机过程。总之,五台山亚高山草地土壤原生生物群落组成和结构沿海拔梯度具有显著的变化格局,群落构建主要由确定性过程和随机过程驱动,但确定性过程占主导地位。

The distribution pattern and maintenance mechanism of biodiversity,namely community assembly are critical issues for the community ecology.A key issue in microbial ecology is quantifying the relative contributions of deterministic processes and stochastic processes to microbial community assembly.Although protists are an important part of the soil microbial communities and play a key role in the microbial loop,compared with bacteria and fungi,we know very little about the elevational distribution patterns and assembly mechanisms of soil protist community.In this paper,we used Illumina Miseq high⁃throughput sequencing technology to comprehensively analyze the community composition and diversity maintenance mechanism of soil protist community in the subalpine grassland ecosystem of Mount Wutai(altitude of 2000—3061 m above sea level).In total,520673 valid sequences,which belong to 8 supergroups,24 phyla,65 classes,125 orders,222 families and 350 genera,were obtained from the soil of the four altitudinal gradients.Cercozoa,Ochrophyta,Ciliophora and Apicomplexa were the dominant soil protist phyla in the study area.LEfSe analysis showed that 17 biomarkers were very sensitive to elevation gradients,and different elevation gradients enriched different protist populations.The altitude had no significant effect on theα⁃diversity of soil protist community,but non⁃metric multidimensional scaling(NMDS)and similarity analysis(ANOSIM)indicated that the compositions and structures of protist communities were significantly different among the elevation gradients(P<0.05).Redundancy analysis(RDA)showed that elevation,soil water content,total nitrogen and plant richness were significantly correlated with protists community structure(P<0.05).Variance partitioning analysis(VPA)and partial Mantel analysis showed that both environmental factors and spatial variables had significant effects on the altitudinal gradient distribution pattern of protist communities,and the relative effect of environmental factors(7.9%)was significantly greater than that of spatial variables(1.8%).The Bray⁃Curtis distance between soil protist communities was significantly and positively correlated with the elevation distance(P<0.05),indicating that the selection process may be the main driving factor for the distribution pattern of soil protist communities in subalpine grassland.The Null⁃model analysis further confirmed that the relative role of deterministic processes in the assembly of soil protist communities was greater than that of stochastic processes.In conclusion,there were significant differences in the structure and composition of soil protist communities in Mount Wutai subalpine grassland along the elevation gradient,and the assembly mechanism was mainly determined by deterministic processes.