Data from: Resource stoichiometry and consumers control the biodiversity-productivity relationship in pelagic metacommunities

Recent theory suggests that biodiversity and productivity are both constrained by resource supply rates and ratios, and that resource stoichiometry is the key to understand the relationship between biodiversity and productivity. We experimentally tested this theory using pelagic metacommunities. We amended existing predictions by explicitly considering evenness as biodiversity aspect and consumer instead of competitive control of algal biomass. The metacommunities received different phosphorus (P)-supply, the three patches within each metacommunity differed in nitrogen (N)-supply to create different N:P ratios (2, 16, 128). All patches were inoculated with a phytoplankton assemblage consisting of 5 species, half of the metacommunities received 2 ciliate species as consumers. At the level of the entire metacommunity, algal biomass increased whereas species richness and evenness decreased with increasing P-supply. Without consumers, resource use efficiency (RUE, realized biomass per unit P) increased with increasing richness and evenness. Consumer presence reduced overall biomass and richness and precluded a correlation between RUE and biodiversity. At the patch level, local evenness correlated to higher RUE at both imbalanced N:P ratios (2 or 128) but not at balanced N:P. In conclusion, overall P-supply constrained realized biomass and altered diversity, whereas resource stoichiometry shaped the relationship between biodiversity and RUE.最新理论指出，生物多样性与生产力均受资源供给速率及配比的制约，而资源化学计量学（resource stoichiometry）是解析二者间关联的关键。我们借助浮游集合群落（pelagic metacommunities）对该理论开展了实验验证。我们对既有预测模型进行了修正，明确将均匀度（evenness）纳入生物多样性维度，并以消费者调控替代了原有的藻类生物量竞争调控机制。各集合群落接受不同梯度的磷（P）供给；每个集合群落内的三个斑块设置差异化的氮（N）供给，以构建不同的氮磷比（N:P）（2、16、128）。所有斑块均接种由5个物种组成的浮游植物群落（phytoplankton assemblage），其中半数集合群落额外接入2种纤毛虫作为消费者。在整个集合群落尺度上，藻类生物量随磷供给提升而增加，而物种丰富度与均匀度则随磷供给提升而降低。在无消费者的实验组中，资源利用效率（resource use efficiency, RUE，即单位磷对应的实际生物量）随物种丰富度与均匀度的提升而升高。消费者的存在会降低整体生物量与物种丰富度，并阻断了资源利用效率与生物多样性之间的关联。在斑块尺度下，当氮磷比失衡（2或128）时，局域均匀度与更高的资源利用效率呈正相关，但在氮磷比平衡的情况下无此关联。综上，整体磷供给制约了实际生物量并改变了群落多样性，而资源化学计量学则调控了生物多样性与资源利用效率之间的关联。