Data from: Competition and coexistence in plant communities: intraspecific competition is stronger than interspecific competition

Theory predicts that intraspecific competition should be stronger than interspecific competition for any pair of stably coexisting species, yet previous literature reviews found little support for this pattern. We screened over 5400 publications and identified 39 studies that quantified phenomenological intraspecific and interspecific interactions in terrestrial plant communities. Of the 67% of species pairs in which both intra- and interspecific effects were negative (competition), intraspecific competition was, on average, four to five-fold stronger than interspecific competition. Of the remaining pairs, 93% featured intraspecific competition and interspecific facilitation, a situation that stabilizes coexistence. The difference between intra- and interspecific effects tended to be larger in observational than experimental data sets, in field than greenhouse studies, and in studies that quantified population growth over the full life cycle rather than single fitness components. Our results imply that processes promoting stable coexistence at local scales are common and consequential across terrestrial plant communities.

理论预测，对于任意一对稳定共存的物种，种内竞争 (intraspecific competition) 应强于种间竞争 (interspecific competition)，但此前的文献综述鲜有证据支持这一规律。我们筛选了超过5400篇文献，最终纳入39项针对陆地植物群落 (terrestrial plant communities) 中现象学层面种内与种间相互作用的定量研究。在67%的物种对中，种内与种间作用均为负值（即竞争作用），此时种内竞争的平均强度是种间竞争的4至5倍。剩余的物种对中，93%呈现种内竞争与种间促进并存的格局，该情形可稳定物种共存。种内与种间作用的差值在观测数据集而非实验数据集中、在野外而非温室研究中、在量化种群全生命周期增长而非单一适合度组分 (fitness components) 的研究中往往更大。本研究结果表明，维持局域尺度物种稳定共存的生态过程在陆地植物群落中普遍存在且具有重要意义。