Physiological Diversity, UFZ, Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318, Leipzig, Germany.
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103, Leipzig, Germany.
Ecology. 2018 Oct;99(10):2295-2307. doi: 10.1002/ecy.2447. Epub 2018 Aug 27.
Despite growing interest in incorporating intraspecific variation of functional traits in community-level studies, it remains unclear whether species classified into functional groups based on interspecific trait differences are similar regarding their variation in trait expression in response to varying plant diversity and composition in local communities. In a large biodiversity experiment (Jena Experiment) designed on a trait-based a priori definition of functional groups (grasses, legumes, small herbs, tall herbs), we studied means, extent of variation (coefficient of variation across communities) and plasticity to increased plant diversity (slopes over a logarithmic species richness ranging from 1, 2, 4, 8 and 16 to 60 species) for nine functional traits. Species means and extent of variation in traits related to nitrogen (N) acquisition and N use differed among functional groups and were more similar in phylogenetically closely related species than expected by chance. Species in the same functional group showed a weak phylogenetic signal and varied widely in means and extent of variation in traits related to shoot architecture and to a smaller extent in leaf traits related to carbon acquisition. This indicated that functional groups were less distinguishable in light than in nitrogen acquisition strategies. The direction and degree of trait plasticity to increasing species richness did not show a phylogenetic signal and were not different among functional groups, but varied largely among species within functional groups. Correlation structures in trait means, extent of trait variation and trait plasticity revealed functional tradeoffs in the acquisition of nitrogen and light across species. While correlations between trait means and extent of trait variation varied from trait to trait (positive, negative or unrelated), trait means and trait plasticity were mostly unrelated. Our results suggest that the concept of functional groups is viable, but context-specific trait measurements are required to improve our understanding about the functional significance of intraspecific trait variation and interspecific trait differences in local plant communities.
尽管人们对在群落水平的研究中纳入功能性状的种内变异越来越感兴趣，但仍不清楚基于种间性状差异将物种分类为功能群，它们在响应当地群落中植物多样性和组成变化的性状表达方面是否具有相似性。在一个基于功能群的先验性状定义（禾本科、豆科、小草本、高草本）设计的大型生物多样性实验（耶拿实验）中，我们研究了 9 个功能性状的平均值、变异程度（群落间的变异系数）和对植物多样性增加的可塑性（对数种丰富度从 1、2、4、8 和 16 到 60 种的斜率）。功能群之间的氮（N）获取和 N 使用相关性状的平均值和变异程度存在差异，并且在亲缘关系较近的物种中比随机预期更相似。同一功能群的物种在性状相关的性状平均值和变异程度上表现出较弱的系统发育信号，并且在与地上结构相关的性状和较小程度上与碳获取相关的叶片性状的平均值和变异程度上差异很大。这表明功能群在光获取策略方面比在氮获取策略方面不太明显。性状对物种丰富度增加的可塑性的方向和程度没有表现出系统发育信号，并且在功能群之间没有差异，但在功能群内的物种之间差异很大。性状平均值、性状变异程度和性状可塑性的相关结构揭示了物种间氮和光获取的功能权衡。虽然性状平均值和性状变异程度之间的相关性因性状而异（正相关、负相关或无关），但性状平均值和性状可塑性大多无关。我们的研究结果表明，功能群的概念是可行的，但需要针对具体情况进行性状测量，以提高我们对种内性状变异和种间性状差异在当地植物群落中的功能意义的理解。
