Data from: The rise and fall of arbuscular mycorrhizal fungal diversity during ecosystem retrogression

Ecosystem retrogression following long-term pedogenesis is attributed to phosphorus (P) limitation of primary productivity. Arbuscular mycorrhizal fungi (AMF) enhance P acquisition for most terrestrial plants, but it has been suggested that this strategy becomes less effective in strongly-weathered soils with extremely-low P availability. Using next generation sequencing of the large subunit ribosomal RNA gene in roots and soil, we compared the composition and diversity of AMF-communities in three contrasting stages of a retrogressive >2-million-year dune chronosequence in a global biodiversity hotspot. This chronosequence shows a ~60-fold decline of total soil P concentration, with the oldest stage representing some of the most severely P-impoverished soils found in any terrestrial ecosystem. The richness of AMF operational taxonomic units was low on young (1000′s of years), moderately P-rich soils, greatest on relatively old (~120,000 years) low-P soils, and low again on the oldest (>2,000,000 years) soils that were lowest in P availability. A similar decline in AMF phylogenetic diversity on the oldest soils occurred, despite invariant host plant diversity and only small declines in host cover along the chronosequence. Differences in AMF community composition were greatest between the youngest and the two oldest soils, and this was best explained by differences in soil P concentrations. Our results point to a threshold in soil P-availability during ecosystem regression below which AMF diversity declines, suggesting environmental filtering of AMF insufficiently adapted to extremely low P availability.长期成土作用后的生态系统退演，通常归因于初级生产力受磷（P）限制。丛枝菌根真菌（Arbuscular Mycorrhizal Fungi，AMF）可促进多数陆生植物获取磷素，但有研究表明，在磷素有效性极低的强风化土壤中，这一策略的效果会显著减弱。本研究通过对根系与土壤中的大亚基核糖体RNA基因进行下一代测序，对比了全球生物多样性热点地区中一处超过200万年的沙丘退演时间序列的三个不同退演阶段的AMF群落组成与多样性。该时间序列的土壤总磷浓度下降约60倍，最老阶段的土壤属于所有陆生生态系统中磷素匮乏最严重的类型之一。AMF操作分类单元（Operational Taxonomic Units，OTU）的丰富度在年轻（数千年历史）、磷素相对丰富的土壤中较低，在约12万年历史的低磷老土壤中达到峰值，而在最古老（>200万年）、磷素有效性最低的土壤中再次降低。尽管宿主植物多样性保持不变，且沿该时间序列的宿主植物盖度仅出现小幅下降，但最老土壤中的AMF系统发育多样性同样出现了类似的下降趋势。AMF群落组成的差异在最年轻土壤与另外两个较老土壤之间最为显著，这一差异可通过土壤磷素浓度的差异得到最佳解释。本研究结果表明，生态系统退演过程中存在一个土壤磷素有效性阈值，低于该阈值时AMF多样性会出现下降，这暗示着对极低磷素环境适应性不足的AMF类群受到了环境过滤作用。