Maynard Daniel S, Bradford Mark A, Lindner Daniel L, van Diepen Linda T A, Frey Serita D, Glaeser Jessie A, Crowther Thomas W
School of Forestry and Environmental Studies, Yale University, 370 Prospect Street, New Haven, Connecticut 06511, USA.
US Forest Service, Northern Research Station, Center for Forest Mycology Research, 1 Gifford Pinchot Drive, Madison, Wisconsin 53726, USA.
Nat Ecol Evol. 2017 May 15;1(6):156. doi: 10.1038/s41559-017-0156.
Competition can profoundly affect biodiversity patterns by determining whether similar species are likely to coexist. When species compete directly for space, competitive ability differences should theoretically promote trait and phylogenetic clustering, provided that niche differences are otherwise minimal. Yet many sessile communities exhibit high biodiversity despite minimal reliance on niche differentiation. A potential explanation is that intransitive competition ('rock-paper-scissors' competition) not only promotes species richness but also fosters coexistence among highly dissimilar species with different competitive strategies. Here, we test this hypothesis using a combination of empirical and analytical approaches. In an experimental system comprising 37 wood-decay basidiomycete fungi grown in nutrient-rich agar media, pairwise displacement was maximized when species had widely different competitive traits and divergent evolutionary histories. However, when these interactions were embedded in models of species-rich communities, high levels of intransitivity ultimately overwhelmed the pairwise relationships, allowing the weakest and most dissimilar species to survive. In line with theoretical expectations, these multispecies assemblages exhibited reduced functional and phylogenetic diversity, yet the smallest losses were likewise observed in species-rich communities. By demonstrating that species richness can act as a self-reinforcing buffer against competitive exclusion, these results contribute to our understanding of how biodiversity is maintained in natural systems.
竞争能够通过决定相似物种是否可能共存来深刻影响生物多样性模式。当物种直接争夺空间时，理论上竞争能力的差异应该会促进性状和系统发育聚类，前提是生态位差异极小。然而，许多固着生物群落尽管对生态位分化的依赖极小，却展现出高生物多样性。一个可能的解释是，非传递性竞争（“石头-剪刀-布”竞争）不仅促进物种丰富度，还能促进具有不同竞争策略的高度不同的物种之间的共存。在此，我们结合实证和分析方法来检验这一假设。在一个由37种在营养丰富的琼脂培养基中生长的木腐担子菌组成的实验系统中，当物种具有广泛不同的竞争性状和不同的进化历史时，并对位移最大化。然而，当这些相互作用被纳入物种丰富的群落模型中时，高水平的非传递性最终压倒了成对关系，使最弱小和最不同的物种得以生存。与理论预期一致，这些多物种组合的功能和系统发育多样性降低，但在物种丰富的群落中也观察到了最小的损失。通过证明物种丰富度可以作为抵御竞争排斥的自我强化缓冲，这些结果有助于我们理解自然系统中生物多样性是如何维持的。
