Gallien Laure, Zurell Damaris, Zimmermann Niklaus E
Swiss Federal Research Institute WSL Birmensdorf Switzerland.
Centre for Invasion Biology Department of Botany and Zoology Stellenbosch University Matieland South Africa.
Ecol Evol. 2018 Jan 22;8(4):2171-2181. doi: 10.1002/ece3.3855. eCollection 2018 Feb.
Disentangling the different processes structuring ecological communities is a long-standing challenge. In species-rich ecosystems, most emphasis has so far been given to environmental filtering and competition processes, while facilitative interactions between species remain insufficiently studied. Here, we propose an analysis framework that not only allows for identifying pairs of facilitating and facilitated species, but also estimates the strength of facilitation and its variation along environmental gradients. Our framework combines the analysis of both co-occurrence and co-abundance patterns using a moving window approach along environmental gradients to control for potentially confounding effects of environmental filtering in the co-abundance analysis. We first validate our new approach against community assembly simulations, and exemplify its potential on a large 1,134 plant community plots dataset. Our results generally show that facilitation intensity was strongest under cold stress, whereas the proportion of facilitating and facilitated species was higher under drought stress. Moreover, the functional distance between individual facilitated species and their facilitating species significantly changed along the temperature-moisture gradient, and seemed to influence facilitation intensity, although no general positive or general negative trend was discernible among species. The main advantages of our robust framework are as follows: It enables detecting facilitating and facilitated species in species-rich systems, and it allows identifying the directionality and intensity of facilitation in species pairs as well as its variation across long environmental gradients. It thus opens numerous opportunities for incorporating functional (and phylogenetic) information in the analysis of facilitation patterns. Our case study indicated high complexity in facilitative interactions across the stress gradient and revealed new evidence that facilitation, similarly to competition, can operate between functionally similar and dissimilar species. Extending the analyses to other taxa and ecosystems will foster our understanding how complex interspecific interactions promote biodiversity.
理清构建生态群落的不同过程是一项长期挑战。在物种丰富的生态系统中，迄今为止，大部分重点都放在了环境过滤和竞争过程上，而物种之间的促进性相互作用仍未得到充分研究。在此，我们提出了一个分析框架，它不仅能够识别促进物种和被促进物种的配对，还能估计促进作用的强度及其沿环境梯度的变化。我们的框架结合了共现和共丰度模式的分析，使用沿环境梯度的移动窗口方法来控制共丰度分析中环境过滤的潜在混杂效应。我们首先针对群落组装模拟验证了我们的新方法，并在一个包含1134个植物群落样地的大型数据集上例证了其潜力。我们的结果总体表明，促进强度在冷胁迫下最强，而促进物种和被促进物种的比例在干旱胁迫下更高。此外，单个被促进物种与其促进物种之间的功能距离沿温度 - 湿度梯度显著变化，并且似乎影响促进强度，尽管在物种之间没有明显的普遍正向或普遍负向趋势。我们这个稳健框架的主要优点如下：它能够在物种丰富的系统中检测促进物种和被促进物种，并且能够识别物种对中促进作用的方向性和强度及其在长环境梯度上的变化。因此，它为在促进模式分析中纳入功能（和系统发育）信息提供了众多机会。我们的案例研究表明，在整个胁迫梯度上促进性相互作用具有高度复杂性，并揭示了新的证据，即促进作用与竞争作用类似，可在功能相似和不同的物种之间发挥作用。将分析扩展到其他分类群和生态系统将增进我们对复杂种间相互作用如何促进生物多样性的理解。
