Shinohara Naoto, Ohsaki Haruna
Center for Ecological Research, Kyoto University, Otsu, Shiga, Japan.
Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan.
Ecology. 2025 Apr;106(4):e70075. doi: 10.1002/ecy.70075.
Most plant species exhibit spatially clustered distributions. Theory suggests such conspecific aggregation can delay competitive exclusion by sparing weak competitors. However, the extent to which spatial aggregation increases species performance and which species are likely to benefit from it remain largely unknown. In this study, we asked (1) whether spatial aggregation enhances plant performance and (2) whether the effects are biologically predictable. For the second question, we focused on "the competition-relatedness hypothesis" and the "competitive asymmetry hypothesis," which relate the effect of spatial arrangement to niche and competitive ability differences between species, respectively. We performed phylogenetic meta-analyses to investigate whether phylogenetic and ecological differences among competitors explain the effect of spatial arrangement. We found idiosyncratic responses of plant species to spatial aggregation. While some species performed better when conspecific individuals were aggregated, others did so when conspecifics and heterospecifics were randomly distributed. The non-negligible number of species benefiting more from intraspecific aggregation indicates that intraspecific competition is sometimes weaker than interspecific competition. Further, the result contrasts with the assumption of the competition-relatedness hypothesis, which postulates the strongest competition among conspecifics, suggesting that this hypothesis does not hold for at least these species. Although phylogeny did not predict the effect of spatial arrangement, interspecific plant height differences did: Species performed better in an aggregation treatment when they were smaller than competitors. Collectively, our results lend more support for the competitive asymmetry hypothesis that interspecific differences in competitive ability underpin the effect of spatial arrangement on plant performance. Moreover, they suggest that spatial processes, such as dispersal limitation, may play an important role in plant coexistence.
大多数植物物种呈现出空间聚集分布。理论表明，这种同种聚集可以通过使弱势竞争者免受竞争来延迟竞争排斥。然而，空间聚集在多大程度上提高物种表现以及哪些物种可能从中受益在很大程度上仍不清楚。在本研究中，我们探讨了两个问题：（1）空间聚集是否增强植物表现；（2）这些影响在生物学上是否可预测。对于第二个问题，我们聚焦于“竞争相关性假说”和“竞争不对称假说”，它们分别将空间排列的影响与物种间的生态位和竞争能力差异联系起来。我们进行了系统发育荟萃分析，以研究竞争者之间的系统发育和生态差异是否能解释空间排列的影响。我们发现植物物种对空间聚集有特异反应。虽然一些物种在同种个体聚集时表现更好，但另一些物种在同种和异种随机分布时表现更好。相当数量的物种从种内聚集受益更多，这表明种内竞争有时比种间竞争弱。此外，该结果与竞争相关性假说的假设相反，该假说假定同种个体间竞争最强，这表明至少对于这些物种来说，这个假说不成立。虽然系统发育不能预测空间排列的影响，但种间植物高度差异可以：当物种比竞争者矮小时，它们在聚集处理中表现更好。总体而言，我们的结果更支持竞争不对称假说，即种间竞争能力差异是空间排列对植物表现产生影响的基础。此外，它们表明诸如扩散限制等空间过程可能在植物共存中起重要作用。
