Kennedy Peter, Nguyen Nhu, Cohen Hannah, Peay Kabir
Department of Plant Biology, University of Minnesota , St. Paul, MN , USA ; Department of Biology, Lewis & Clark College , Portland, OR , USA.
Department of Plant Biology, University of Minnesota , St. Paul, MN , USA.
PeerJ. 2014 Dec 16;2:e686. doi: 10.7717/peerj.686. eCollection 2014.
A number of recent studies suggest that interspecific competition plays a key role in determining the structure of ectomycorrhizal (ECM) fungal communities. Despite this growing consensus, there has been limited study of ECM fungal community dynamics in abiotically stressful environments, which are often dominated by positive rather than antagonistic interactions. In this study, we examined the ECM fungal communities associated with the host genus Alnus, which live in soils high in both nitrate and acidity. The nature of ECM fungal species interactions (i.e., antagonistic, neutral, or positive) was assessed using taxon co-occurrence and DNA sequence abundance correlational analyses. ECM fungal communities were sampled from root tips or mesh in-growth bags in three monodominant A. rubra plots at a site in Oregon, USA and identified using Illumina-based amplification of the ITS1 gene region. We found a total of 175 ECM fungal taxa; 16 of which were closely related to known Alnus-associated ECM fungi. Contrary to previous studies of ECM fungal communities, taxon co-occurrence analyses on both the total and Alnus-associated ECM datasets indicated that the ECM fungal communities in this system were not structured by interspecific competition. Instead, the co-occurrence patterns were consistent with either random assembly or significant positive interactions. Pair-wise correlational analyses were also more consistent with neutral or positive interactions. Taken together, our results suggest that interspecific competition does not appear to determine the structure of all ECM fungal communities and that abiotic conditions may be important in determining the specific type of interaction occurring among ECM fungi.
最近的一些研究表明，种间竞争在决定外生菌根（ECM）真菌群落结构方面起着关键作用。尽管这一共识日益增强，但对于非生物胁迫环境中外生菌根真菌群落动态的研究却很有限，这类环境中往往以积极而非对抗性相互作用为主导。在本研究中，我们调查了与桤木属宿主相关的外生菌根真菌群落，这些宿主生长在硝酸盐和酸度都很高的土壤中。利用分类单元共现和DNA序列丰度相关分析评估了外生菌根真菌物种相互作用的性质（即对抗性、中性或阳性）。在美国俄勒冈州一个地点的三个单优势红桤木样地中，从根尖或网袋中采集外生菌根真菌群落样本，并使用基于Illumina的ITS1基因区域扩增进行鉴定。我们总共发现了175个外生菌根真菌分类单元；其中16个与已知的与桤木相关的外生菌根真菌密切相关。与之前关于外生菌根真菌群落的研究相反，对总数据集和与桤木相关的外生菌根数据集进行的分类单元共现分析表明，该系统中的外生病根真菌群落并非由种间竞争构建。相反，共现模式与随机组装或显著的正向相互作用一致。成对相关分析也更符合中性或正向相互作用。综上所述，我们的结果表明，种间竞争似乎并不能决定所有外生菌根真菌群落的结构，非生物条件可能在决定外生菌根真菌之间发生的特定相互作用类型方面很重要。
