Orchidaceae has diversified in tree canopies and accounts for 68% of vascular epiphytes. Differences in mycorrhizal communities among epiphytic orchids can reduce species competition for mycorrhizal fungi and contribute to niche partitioning, which may be a crucial driver of the unusual species diversification among orchids. Mycorrhizal specificity—the range of fungi allowing mycorrhizal partnerships—was evaluated by assessment of mycorrhizal communities in the field (ecological specificity) and symbiotic cultures in the laboratory (physiological specificity) for three epiphytic orchids inhabiting Japan. Mycorrhizal communities were assessed with co-existing individuals growing within 10 cm of each other, revealing that ecological specificity varied widely among the three species, ranging from dominance by a single Ceratobasidiaceae fungus to diverse mycobionts across the Ceratobasidiaceae and Tulasnellaceae. In vitro seed germination tests revealed clear differences in physiological specificity among the three orchids, and that the primary mycorrhizal partners contributed to seed germination. In vitro compatibility ranges of three orchids strongly reflect the mycorrhizal community composition of wild populations. This suggests that differences in in situ mycorrhizal communities are not strongly driven by environmental factors, but are primarily due to physiological differences among orchid species. This study shows that the symbiotic strategy among the epiphytic orchid species varies from specialized to generalized association, which may contribute to biotic niche partitioning.

兰科植物在树冠上具有多样性，占维管束附生植物的 68%。附生兰花之间菌根群落的差异可以减少菌根真菌的物种竞争并有助于生态位划分，这可能是兰花之间异常物种多样化的关键驱动因素。通过对日本三种附生兰花的田间菌根群落（生态特异性）和实验室共生培养物（生理特异性）进行评估，评估了菌根特异性（允许菌根伙伴关系的真菌范围）。对彼此生长在 10 厘米以内的共存个体进行了菌根群落评估，结果表明，这三个物种之间的生态特异性差异很大，从单一的角担子科真菌占优势，到角担子科和土拉斯球菌科的多种真菌生物群占主导地位。体外种子发芽试验揭示了三种兰花之间生理特异性的明显差异，并且初级菌根伙伴有助于种子发芽。三种兰花的体外相容性范围强烈反映了野生种群的菌根群落组成。这表明原位菌根群落的差异并不是由环境因素强烈驱动的，而主要是由于兰花物种之间的生理差异造成的。这项研究表明，附生兰花物种之间的共生策略从专门的关联到广义的关联都有所不同，这可能有助于生物生态位的划分。