Kergunteuil Alan, Descombes Patrice, Glauser Gaetan, Pellissier Loïc, Rasmann Sergio
Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000, Neuchâtel, Switzerland.
Landscape Ecology, Institute of Terrestrial Ecosystems, ETH Zurich, Zurich, Switzerland.
Oecologia. 2018 Jun;187(2):561-571. doi: 10.1007/s00442-018-4162-y. Epub 2018 May 17.
Predicting variation in plant functional traits related to anti-herbivore defences remains a major challenge in ecological research, considering that multiple traits have evolved in response to both abiotic and biotic conditions. Therefore, understanding variation in plant anti-herbivore defence traits requires studying their expression along steep environmental gradients, such as along elevation, where multiple biotic and abiotic factors co-vary. We expand on plant defence theory and propose a novel conceptual framework to address the sources of variations of plant resistance traits at the community level. We analysed elevation patterns of within-community trait dissimilarity using the RaoQ index, and the community-weighted-mean (CWM) index, on several plant functional traits: plant height, specific leaf area (SLA), leaf-dry-matter-content (LDMC), silicium content, presence of trichomes, carbon-to-nitrogen ratio (CN) and total secondary metabolite richness. We found that at high elevation, where harsh environmental conditions persist, community functional convergence is dictated by traits relating to plant growth (plant height and SLA), while divergence arises for traits relating resource-use (LDMC). At low elevation, where greater biotic pressure occurs, we found a combination of random (plant height), convergence (metabolite richness) and divergence patterns (silicium content). This framework thus combines community assembly rules of ecological filtering and niche partition with plant defence hypotheses to unravel the relationship between environmental variations, biotic pressure and the average phenotype of plants within a community.
鉴于多种植物功能性状是在非生物和生物条件共同作用下进化而来的，预测与抗食草动物防御相关的植物功能性状变异仍是生态研究中的一大挑战。因此，要了解植物抗食草动物防御性状的变异，就需要研究其在陡峭环境梯度（如海拔梯度）上的表达情况，因为在这些梯度上多种生物和非生物因素会共同变化。我们拓展了植物防御理论，并提出了一个新颖的概念框架，以探讨群落层面植物抗性性状变异的来源。我们使用RaoQ指数和群落加权平均（CWM）指数，分析了几种植物功能性状在群落内部性状差异的海拔格局，这些性状包括：株高、比叶面积（SLA）、叶干物质含量（LDMC）、硅含量、是否有毛状体、碳氮比（CN）以及次生代谢物总丰富度。我们发现，在高海拔地区，恶劣环境条件持续存在，群落功能趋同由与植物生长相关的性状（株高和SLA）决定，而与资源利用相关的性状（LDMC）则出现分化。在低海拔地区，生物压力更大，我们发现了随机（株高）、趋同（代谢物丰富度）和分化模式（硅含量）的组合。因此，这个框架将生态过滤和生态位划分的群落组装规则与植物防御假说结合起来，以揭示环境变异、生物压力与群落内植物平均表型之间的关系。
