Plant Science and Conservation, Chicago Botanic Garden, Glencoe, IL, USA.
Adaptive Restoration LLC., 8864 Offerdahl Road, Mount Horeb, WI, 53572, USA.
Oecologia. 2021 Oct;197(2):459-469. doi: 10.1007/s00442-021-05024-4. Epub 2021 Sep 2.
Phylogenetic ecology uses evolutionary history to improve understanding of plant interactions. Phylogenetic distance can mediate plant interactions such as competition (e.g., via limiting similarity) and facilitation (e.g., via niche complementarity), influencing community assembly patterns. Previous research has found evidence both for and against a relationship between phylogenetic distance and the strength of plant interactions, and has found that other factors, such as trait differences, may be more influential. In addition to phylogenetic distance and species' traits, environmental conditions can also influence competition, with facilitative interactions-particularly among distantly related species-potentially becoming more pronounced under stressful, resource-limited conditions. We tested the prediction that greater phylogenetic distance is associated with decreased competition in a greenhouse experiment using plant species of the North American tallgrass prairie. We calculated the Relative Interaction Index for 81 species pairs using plant height, leaf length, and biomass as indicators of performance. We found that phylogenetic distance alone did not significantly affect competition. However, the interaction between phylogenetic distance and stressful conditions (sandier soils with low nutrient availability and water retention vs. resource-rich potting soil) altered plant traits and competition. Under stressful conditions, more distantly related species competed more strongly, leading to smaller plants. Conversely, under benign conditions more distantly related species pairs competed less and were larger. These results were contrary to our expectations that distant relatives would compete less under stressful conditions. Our experiment provides evidence that, while relatedness alone may not drive competition, phylogenetic distance can nonetheless be influential through interactions with environmental conditions.
系统发育生态学利用进化历史来增进对植物相互作用的理解。系统发育距离可以调节植物相互作用，如竞争（例如，通过限制相似性）和促进（例如，通过生态位互补），影响群落组装模式。先前的研究已经发现了系统发育距离与植物相互作用强度之间存在关系的证据，也发现了其他因素，如性状差异，可能更具影响力。除了系统发育距离和物种特征外，环境条件也会影响竞争，在资源有限、压力较大的条件下，促进作用（特别是在亲缘关系较远的物种之间）可能更为明显。我们通过温室实验检验了以下预测：在北美高草原中使用植物物种，系统发育距离越大，竞争就越低。我们使用植物高度、叶片长度和生物量作为性能指标，计算了 81 个种对的相对相互作用指数。我们发现，系统发育距离本身并不能显著影响竞争。然而，系统发育距离与胁迫条件（养分和水分保持能力较低的沙质土壤与资源丰富的盆栽土壤之间的相互作用）之间的相互作用改变了植物性状和竞争。在胁迫条件下，亲缘关系较远的物种竞争更激烈，导致植物变小。相反，在良性条件下，亲缘关系较远的种对竞争较少，体型较大。这些结果与我们的预期相反，即远缘亲属在胁迫条件下的竞争应该较少。我们的实验提供了证据表明，尽管亲缘关系本身可能不会驱动竞争，但通过与环境条件的相互作用，系统发育距离仍然可以产生影响。
