Data from: Linking species abundance and overyielding from experimental communities with niche and fitness characteristics

1) So far, the principal force shaping local plant abundance patterns remains unclear. Rarity can result from poor competitive ability or from small vegetative or generative reproduction, but also from strong self-limitation. The same mechanisms can drive species-specific overyielding, i.e. increased species productivity at high community diversity. Rare species can then benefit more (i.e. overyield to a larger extent) from growing in species-rich communities because of altered competitive hierarchies or smaller conspecific frequencies. Here we test which mechanism is the most important determinant of species rarity and of species-specific productivity across a diversity gradient ranging from one- to 60-species plots.
2) For that we measured vegetative growth, competitive ability (competitive effect), and negative frequency dependence for 49 perennial grassland species from Central Europe. We then linked these characteristics with species abundance (measured as species biomass from 60-species plots) and with species-specific overyielding in The Jena Experiment.
3) Species with higher rates of vegetative growth (when grown without neighbors) were also more abundant in the Jena Experiment. Larger species-specific overyielding was then associated with a stronger negative frequency dependence. As species with greater vegetative growth were also more self-limited, larger overyielding in species-rich communities was characteristic for common rather than for rare species, refuting our initial hypothesis. Finally, path analysis indicated that species with poor capacity to suppress neighbors also profited more from growing in diverse communities.
4) Synthesis. Our results identify key mechanisms driving abundance and productivity of species in synthetic communities differing in species richness. While vegetative reproduction was closely associated with abundance, intraspecific interactions (strength of negative frequency dependence) shaped species productivity across a richness gradient. Our study sheds light on the abundance patterns of species and their influence on community functions, such as biomass production, of species-rich and -poor vegetation.

1) 迄今为止，塑造本地植物多度格局的核心驱动力仍未明确。物种稀有性可源于竞争能力不足、营养繁殖与有性繁殖能力低下，亦可能源自强烈的种内自限作用。上述机制同样可驱动物种特异性超产效应（species-specific overyielding），即群落在高多样性水平下物种生产力提升的现象。由于竞争格局发生改变或同种个体频率降低，稀有物种在物种丰富的群落中生长时，往往能获得更多收益（即超产幅度更大）。本研究针对从单物种到60物种的样地多样性梯度，检验何种机制是决定物种稀有性以及物种特异性生产力的核心因素。
2) 为此，我们针对49种中欧多年生草原物种，测定了其营养生长速率、竞争能力（即竞争效应）以及负频率依赖效应（negative frequency dependence）。随后，我们将这些性状与物种多度（以60物种样地中的物种生物量衡量）以及耶拿野外实验（Jena Experiment）中的物种特异性超产效应进行关联分析。
3) 在耶拿野外实验中，营养生长速率更高（即无邻株生长时）的物种通常多度更高。更强的物种特异性超产效应与更显著的负频率依赖效应呈显著正相关。由于营养生长更旺盛的物种同时也面临更强的种内自限作用，因此在物种丰富群落中表现出更大超产效应的往往是常见物种而非稀有物种，这与我们的初始假说相悖。最后，路径分析（path analysis）结果显示，抑制邻株生长能力较弱的物种，在多样落环境中生长时同样能获得更多收益。
4) 研究综合。本研究明确了驱动不同物种丰富度人工合成群落中植物多度与生产力的核心机制。尽管营养繁殖与物种多度密切相关，但种内相互作用（即负频率依赖效应的强度）决定了物种在丰富度梯度下的生产力水平。本研究揭示了植物物种的多度格局，及其对物种丰富与贫乏群落的群落功能（如生物量生产）的影响。