PREMISE Orchids depend primarily on mycorrhizal fungi to obtain nutrients throughout their life cycle. Epiphytic orchids account for 69% of orchid diversity. The unstable availability of water and nutrients in their arboreal habitats often results in severe water and nutrient stresses. Consequently, mycorrhizal associations may be important for the survival of epiphytic orchids, but our understanding thereof remains limited. Here, we investigated the mycorrhizal community in a single epiphytic orchid species, using more samples than in any previous study. METHODS We assessed the mycorrhizal communities of Thrixspermum japonicum, one of the most common epiphytic orchids in the temperate region of Japan. In total, 144 individuals were collected from 28 host tree species at 20 sites across 1300 km. The mycorrhizal fungi were identified based on nuclear ribosomal DNA internal transcribed spacer sequences and assigned operational taxonomic units (OTUs) based on 97% sequence similarity. RESULTS We obtained 24 OTUs; 9 belonged to the Ceratobasidiaceae and 15 to the Tulasnellaceae. These OTUs are widely distributed throughout the phylogenetic trees of the two fungal families. However, a single Ceratobasidiaceae OTU accounted for 49.7% of all fungal sequences and was predominant in samples from 15 host tree species and 12 sites. CONCLUSIONS Our results imply that despite having a broad range of mycorrhizal partners, T. japonicum was predominantly associated with a single fungal taxon at most of the sites among the host-tree species investigated. These findings contribute to elucidating mycorrhizal symbiosis in epiphytic habitats.

中文翻译：

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尽管有多种真菌伙伴，但附生兰花 Thrixspermum japonicum 的菌根群落强烈偏向于单一的 Ceratobasidiaceae 真菌

前提兰花主要依靠菌根真菌在其整个生命周期中获取营养。附生兰花占兰花多样性的 69%。其树栖栖息地的水和养分供应不稳定，通常会导致严重的水和养分压力。因此，菌根关联可能对附生兰花的生存很重要，但我们对此的理解仍然有限。在这里，我们调查了单一附生兰花物种中的菌根群落，使用的样本比之前的任何研究都多。方法 我们评估了日本温带地区最常见的附生兰花之一 Thrixspermum japonicum 的菌根群落。总共从 1300 公里范围内的 20 个地点的 28 个寄主树种中收集了 144 个个体。菌根真菌是基于核核糖体 DNA 内部转录间隔序列确定的，并根据 97% 的序列相似性分配操作分类单位 (OTU)。结果我们获得了24个OTU；9 属于 Ceratobasidiaceae 和 15 属于 Tulasnellaceae。这些 OTU 广泛分布在两个真菌科的系统发育树中。然而，单个 Ceratobasidiaceae OTU 占所有真菌序列的 49.7%，并且在来自 15 个寄主树种和 12 个地点的样本中占主导地位。结论 我们的结果表明，尽管具有广泛的菌根伙伴，但在所研究的寄主树种中的大多数地点，日本木霉主要与单一真菌分类群相关。这些发现有助于阐明附生生境中的菌根共生。