The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH, UK.
New Phytol. 2014 Oct;204(2):386-96. doi: 10.1111/nph.12908. Epub 2014 Jul 2.
Facilitative effects of some species on others are a major driver of biodiversity. These positive effects of a benefactor on its beneficiary can result in negative feedback effects of the beneficiary on the benefactor and reduced fitness of the benefactor. However, in contrast to the wealth of studies on facilitative effects in different environments, we know little about whether the feedback effects show predictable patterns of context dependence. We reanalyzed a global data set on alpine cushion plants, previously used to assess their positive effects on biodiversity and the nature of the beneficiary feedback effects, to specifically assess the context dependence of how small- and large-scale drivers alter the feedback effects of cushion-associated (beneficiary) species on their cushion benefactors using structural equation modelling. The effect of beneficiaries on cushions became negative when beneficiary diversity increased and facilitation was more intense. Local-scale biotic and climatic conditions mediated these community-scale processes, having indirect effects on the feedback effect. High-productivity sites demonstrated weaker negative feedback effects of beneficiaries on the benefactor. Our results indicate a limited impact of the beneficiary feedback effects on benefactor cushions, but strong context dependence. This context dependence may help to explain the ecological and evolutionary persistence of this widespread facilitative system.
一些物种对其他物种的促进作用是生物多样性的主要驱动因素。这种施主对受益者的积极影响可能导致受益者对施主的负面反馈效应，并降低施主的适合度。然而，与不同环境中促进作用的大量研究相比，我们对反馈效应是否表现出可预测的情境依赖性知之甚少。我们重新分析了一个关于高山垫状植物的全球数据集，该数据集之前用于评估它们对生物多样性的积极影响以及受益物种对垫状植物施主反馈效应的性质，使用结构方程模型专门评估小规模和大规模驱动因素如何改变垫状相关（受益）物种对其垫状施主的反馈效应的情境依赖性。当受益物种多样性增加且促进作用更强时，受益物种对垫状植物的影响变为负面。本地尺度的生物和气候条件调节了这些群落尺度的过程，对反馈效应产生间接影响。高生产力的地点对施主的反馈效应表现出较弱的负面反馈效应。我们的结果表明，受益物种对施主垫状植物的反馈效应的影响有限，但具有强烈的情境依赖性。这种情境依赖性可能有助于解释这种广泛存在的促进系统在生态和进化上的持续性。
