Data from: Complementarity in both plant and mycorrhizal fungal communities are not necessarily increased by diversity in the other

1. Higher species diversity can improve community performance within a species guild when different species complement each other in their use of the available niche, such as through resource partitioning. However, species in one guild of organisms may act as resources for another such that the diversity in one guild alters the realized niche for species in another. Yet, it remains largely untested as to whether diversity in one guild of organisms influences species complementarity in another. 2. The productivity and diversity in plant and arbuscular mycorrhizal (AM) fungal communities can be positively associated with each other through their typically mutualistic exchange of resources. Here we utilized these two interacting species guilds to determine whether greater diversity in one influences species complementarity in the other. This was done by creating monocultures and a mixture of a grass, forb, and legume in a full factorial design with monocultures and a mixture of four AM fungi. 3. The presence of AM fungi reduced differences in the performance among plant species and greater diversity of fungi generally improved plant productivity over the average of the fungal monocultures. However, plant species complementarity was not greatest with a higher diversity of fungi and was only positive with a particular fungal monoculture. 4. AM fungal abundance was not affected by plant diversity, but was greatly reduced in the grass monoculture compared to the other plant communities. Variation in fungal complementarity among plant communities was low overall and was little influenced by plant diversity. 5. Synthesis. Using a model plant-mycorrhizal system our results suggest that the composition rather than the diversity of species within one guild may be more influential in determining how species function within an associated species guild. However, our model system does not represent a broad gradient of diversity in either plant or fungal communities and only assesses the initial growth phase. Nonetheless our results highlight that changes in species compositions in one species guild can affect the functioning of species diversity in another.

1. 当不同物种在利用现有生态位时存在互补关系（例如通过资源分隔），较高的物种多样性可提升单一物种功能群内的群落表现。然而，某一功能群中的生物可充当另一功能群的资源，使得该功能群的多样性会改变另一功能群物种的实际生态位。但目前学界尚未充分验证：某一功能群的生物多样性是否会影响另一功能群的物种互补性。
2. 植物与丛枝菌根（arbuscular mycorrhizal, AM）真菌群落的生产力与多样性，通常可通过二者间的互利资源交换形成正向关联。本研究利用这两类存在互作关系的物种功能群，旨在探究某一功能群的更高多样性是否会影响另一功能群的物种互补性。实验采用全因子设计，分别构建了草本、非禾本科草本及豆科植物的单种栽培与混合栽培体系，同时设置了4种AM真菌的单种栽培与混合栽培体系。
3. AM真菌的存在可降低不同植物物种间的表现差异，且相较于真菌单种栽培的平均水平，更高的真菌多样性总体上可提升植物生产力。但植物物种的互补性并未在真菌多样性更高的处理中达到最高，仅在某一特定的真菌单种栽培处理中呈现正向效应。
4. AM真菌的丰度不受植物多样性的影响，但相较于其他植物群落，草本植物单种栽培体系中的AM真菌丰度显著降低。不同植物群落间的真菌互补性总体变异程度较低，且几乎不受植物多样性的调控。
5. 综合分析：本研究依托模式植物-菌根系统所得结果表明，相较于物种功能群内的物种多样性，物种组成或许对关联功能群内的物种功能发挥具有更显著的调控作用。但本研究的模式系统未能覆盖植物或真菌群落多样性的广泛梯度，且仅评估了植物生长初期阶段。尽管如此，本研究结果仍凸显出：某一物种功能群的组成变化，可影响另一功能群的物种多样性功能效应。