Data from: Mycorrhizal diversity, seed germination and long-term changes in population size across nine populations of the terrestrial orchid Neottia ovata

In plant species that rely on mycorrhizal symbioses for germination and seedling establishment, seedling recruitment and temporal changes in abundance can be expected to depend on fungal community composition and local environmental conditions. However, disentangling the precise factors that determine recruitment success in species that critically rely on mycorrhizal fungi represents a major challenge. In this study, we used seed germination experiments, 454 amplicon pyrosequencing and assessment of soil conditions to investigate the factors driving changes in local abundance in 28 populations of the orchid Neottia ovata. Comparison of population sizes measured in 2003 and 2013 showed that nearly 60% of the studied populations had declined in size (average growth rate across all populations: −0.01). Investigation of the mycorrhizal fungi in both the roots and soil revealed a total of 68 species of putatively mycorrhizal fungi, 21 of which occurred exclusively in roots, 25 that occurred solely in soil and 22 that were observed in both the soil and roots. Seed germination was limited and significantly and positively related to soil moisture content and soil pH, but not to fungal community composition. Large populations or populations with high population growth rates showed significantly higher germination than small populations or populations declining in size, but no significant relationships were found between population size or growth and mycorrhizal diversity. Overall, these results indicate that temporal changes in abundance were related to the ability of seeds to germinate, but at the same time they provided limited evidence that variation in fungal communities played an important role in determining population dynamics.

对于依赖菌根共生（mycorrhizal symbioses）完成萌发与幼苗建成的植物类群而言，幼苗招募（seedling recruitment）及其种群丰度的时间动态变化，理应取决于真菌群落组成与局域环境条件。然而，对于严格依赖菌根真菌的物种而言，厘清决定其招募成功的精准因素仍是一项重大挑战。本研究通过种子萌发实验、454扩增子焦磷酸测序（454 amplicon pyrosequencing）以及土壤条件测定，探究了驱动兰科植物卵叶鸟巢兰（Neottia ovata）28个局域种群丰度变化的影响因素。对比2003年与2013年测定的种群大小发现，近60%的研究种群出现了规模缩减（所有种群的平均增长率为-0.01）。对根与土壤中的菌根真菌进行调查后，共鉴定出68种疑似菌根真菌：其中21种仅存在于根组织中，25种仅分布于土壤，剩余22种则同时在土壤与根组织中被检出。种子萌发率偏低，且与土壤含水量、土壤pH值呈显著正相关，但与真菌群落组成无显著关联。种群规模较大或增长率较高的种群，其种子萌发率显著高于小型种群或规模缩减的种群；但种群大小、增长率与菌根真菌多样性之间并未发现显著关联。综合来看，本研究结果表明，种群丰度的时间动态变化与种子萌发能力相关，但同时也仅提供了有限证据，证明真菌群落的变异对种群动态具有重要调控作用。