Local scale spatial diversity patterns of ectomycorrhizal fungal communities in a subtropical pine-oak forest

This study aimed to describe local-scale spatial diversity patterns of ectomycorrhizal fungal (EMF) communities in a subtropical pine-oak forest in central Mexico. We hypothesized that, being in an environmentally heterogeneous region and a biogeographical realm transition, the study site would have high diversity and species turnover and spatially structured EMF communities. We established a spatially explicit nested square sampling design with three replicate plots divided into 64 subplots (10 x 10 m), and for each replicate half of the subplots were sampled Fungal sequences were recovered from soil samples by Illumina MiSeq sequencing of ITS2 region. EMF OTUs were determined using FUNGuild software. We found 674 EMF OTUs in 19,200 m2 and 65 OTUs on average per sampling point. Seventy percent of OTUs were detected in only 1-4 samples. Average community similarity was below 5% and did not decrease with increasing distance or area. We found one of the highest reported species-area relationships and beta diversity coefficients for soil fungi indicating that increasing area by a constant factor of four represented an increase in OTU richness by a factor of two. Altogether, the results support the value of preserving biodiversity in small forest fragments within productive land as part of an adaptation strategy to increase ecosystem resilience to human disturbance and climate change.

本研究旨在阐明墨西哥中部亚热带松栎林外生菌根真菌（ectomycorrhizal fungal, EMF）群落的局域尺度空间多样性格局。我们提出如下假说：鉴于研究区域兼具环境异质性与生物地理界过渡属性，样地内的外生菌根真菌群落将呈现较高的物种多样性、物种更替现象，且群落具有空间结构。本研究采用空间显性嵌套方形采样方案：设置3组重复样地，每一样地划分为64个10 m×10 m的小样方；每组重复样地中选取半数小样方开展采样。通过对土壤样本的ITS2区域进行Illumina MiSeq测序，成功获取真菌序列。利用FUNGuild软件界定外生菌根真菌的操作分类单元（Operational Taxonomic Unit, OTU）。本研究在19200 m²的样地内共检出674个外生菌根真菌OTU，每个采样点平均包含65个OTU。其中70%的OTU仅在1~4个样本中被检测到。群落平均相似性低于5%，且未随采样距离或样地面积的增加而降低。本研究观测到土壤真菌类群中已报道的最高物种-面积关系与β多样性系数之一：样地面积每恒定扩大四倍，OTU丰富度便提升一倍。综上，本研究结果证实，在生产性土地范围内留存小型森林片段以保护生物多样性，可作为提升生态系统对人类干扰与气候变化恢复力的适应性策略之一，其生态价值值得重视。