Background and Aims Mycorrhizal fungi are a critical component of the ecological niche of most plants and can potentially constrain their geographical range. Unlike other types of mycorrhizal fungi, the distributions of orchid mycorrhizal fungi (OMF) at large spatial scales are not well understood. Here, we investigate the distribution and diversity of Ceratobasidium OMF in orchids and soils across the Australian continent. Methods We sampled 217 Ceratobasidium isolates from 111 orchid species across southern Australia and combined these with 311 Ceratobasidium sequences from GenBank. To estimate the taxonomic diversity of Ceratobasidium associating with orchids, phylogenetic analysis of the ITS sequence locus was undertaken. Sequence data from the continent-wide Australian Microbiome Initiative were used to determine the geographical range of operational taxonomic units (OTUs) detected in orchids, with the distribution and climatic correlates of the two most frequently detected OTUs modelled using MaxEnt. Key Results We identified 23 Ceratobasidium OTUs associating with Australian orchids, primarily from the orchid genera Pterostylis, Prasophyllum, Rhizanthella and Sarcochilus. OTUs isolated from orchids were closely related to, but distinct from, known pathogenic fungi. Data from soils and orchids revealed that ten of these OTUs occur on both east and west sides of the continent, while 13 OTUs were recorded at three locations or fewer. MaxEnt models suggested that the distributions of two widespread OTUs are correlated with temperature and soil moisture of the wettest quarter and far exceeded the distributions of their host orchid species. Conclusions Ceratobasidium OMF with cross-continental distributions are common in Australian soils and frequently have geographical ranges that exceed that of their host orchid species, suggesting these fungi are not limiting the distributions of their host orchids at large spatial scales. Most OTUs were distributed within southern Australia, although several OTUs had distributions extending into central and northern parts of the continent, illustrating their tolerance of an extraordinarily wide range of environmental conditions.

中文翻译：

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澳大利亚Ceratobasidium兰花菌根真菌的大陆尺度分布和多样性

背景和目的 菌根真菌是大多数植物生态位的重要组成部分，可能会限制它们的地理范围。与其他类型的菌根真菌不同，兰花菌根真菌（OMF）在大空间尺度上的分布尚不清楚。在这里，我们调查了 Ceratobasidium OMF 在整个澳大利亚大陆的兰花和土壤中的分布和多样性。方法 我们从澳大利亚南部的 111 种兰花中采集了 217 个 Ceratobasidium 分离株，并将这些与来自 GenBank 的 311 个 Ceratobasidium 序列相结合。为了估计与兰花相关的 Ceratobasidium 的分类多样性，对 ITS 序列基因座进行了系统发育分析。来自全大陆的澳大利亚微生物组计划的序列数据用于确定在兰花中检测到的操作分类单位 (OTU) 的地理范围，以及使用 MaxEnt 建模的两个最常检测到的 OTU 的分布和气候相关性。主要结果 我们确定了 23 种与澳大利亚兰花相关的 Ceratobasidium OTU，主要来自兰花属 Pterostylis、Prasophyllum、Rhizanthella 和 Sarcochilus。从兰花中分离出的 OTU 与已知的致病真菌密切相关，但又有所不同。来自土壤和兰花的数据显示，其中 10 个 OTU 出现在非洲大陆的东西两侧，而 13 个 OTU 记录在三个或更少的位置。MaxEnt 模型表明，两个广泛分布的 OTU 的分布与最潮湿地区的温度和土壤湿度相关，并且远远超过了它们寄主兰花物种的分布。结论 跨大陆分布的 Ceratobasidium OMF 在澳大利亚土壤中很常见，并且经常具有超过其寄主兰花物种的地理范围，这表明这些真菌并未限制其寄主兰花在大空间尺度上的分布。大多数 OTU 分布在澳大利亚南部，尽管一些 OTU 的分布范围延伸到该大陆的中部和北部，这表明它们对极其广泛的环境条件的耐受性。结论 跨大陆分布的 Ceratobasidium OMF 在澳大利亚土壤中很常见，并且经常具有超过其寄主兰花物种的地理范围，这表明这些真菌并未限制其寄主兰花在大空间尺度上的分布。大多数 OTU 分布在澳大利亚南部，尽管一些 OTU 的分布范围延伸到该大陆的中部和北部，这表明它们对极其广泛的环境条件的耐受性。结论 跨大陆分布的 Ceratobasidium OMF 在澳大利亚土壤中很常见，并且经常具有超过其寄主兰花物种的地理范围，这表明这些真菌并未限制其寄主兰花在大空间尺度上的分布。大多数 OTU 分布在澳大利亚南部，尽管一些 OTU 的分布范围延伸到该大陆的中部和北部，这表明它们对极其广泛的环境条件的耐受性。