Trait‐based ecology suggests that abiotic filtering is the main mechanism structuring the regional species pool in different subsets of habitat‐specific species. At more local spatial scales, other ecological processes may add on giving rise to complex patterns of functional diversity (FD). Understanding how assembly processes operating on the habitat‐specific species pools produce the locally observed plant assemblages is an ongoing challenge. Here, we evaluated the importance of different processes to community assembly in an alpine fellfield, assessing its effects on local plant trait FD. Using classical randomization tests and linear mixed models, we compared the observed FD with expectations from three null models that hierarchically incorporate additional assembly constraints: stochastic null models (random assembly), independence null models (each species responding individual and independently to abiotic environment), and co‐occurrence null models (species responding to environmental variation and to the presence of other species). We sampled species composition in 115 quadrats across 24 locations in the central Pyrenees (Spain) that differed in soil conditions, solar radiation and elevation. Overall, the classical randomization tests were unable to find differences between the observed and expected functional patterns, suggesting that the strong abiotic filters that sort out the flora of extreme regional environments blur any signal of other local processes. However, our approach based on linear mixed models revealed the signature of different ecological processes. In the case of seed mass and leaf thickness, observed FD significantly deviated from the expectations of the stochastic model, suggesting that fine‐scale abiotic filtering and facilitation can be behind these patterns. Our study highlights how the hierarchical incorporation of ecological additional constraints may shed light on the dim signal left by local assembly processes in alpine environments.

中文翻译：

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淡淡的苍白阴影：在强烈过滤的植物群落结构上揭示了局部装配过程的微弱特征

基于特征的生态学表明，非生物过滤是构成特定栖息地物种不同子集中区域物种库的主要机制。在更局部的空间尺度上，其他生态过程可能会增加功能多样性（FD）的复杂模式。理解在栖息地特定物种库上进行的组装过程如何产生本地观察到的植物集合是一项持续的挑战。在这里，我们评估了不同过程对一个高山塌陷区的社区组装的重要性，并评估了其对当地植物性状FD的影响。使用经典的随机检验和线性混合模型，我们将观察到的FD与来自三个空模型的期望值进行了比较，这三个空模型在层次上合并了附加的装配约束：随机空模型（随机装配），独立无效模型（每个物种对个体和非生物环境做出响应）和共现无效模型（对环境变化和其他物种的存在做出响应的物种）。我们在比利牛斯山脉中部（西班牙）的24个位置的115个正交体中采样了物种组成，其土壤条件，太阳辐射和海拔不同。总体而言，经典的随机测试无法发现观察到的功能模式与预期功能模式之间的差异，这表明强大的非生物过滤器可以筛选出极端区域环境中的植物，从而模糊了其他局部过程的信号。但是，我们基于线性混合模型的方法揭示了不同生态过程的特征。就种子质量和叶片厚度而言，观察到的FD显着偏离了随机模型的期望，表明精细的非生物过滤和促进可能是这些模式的背后。我们的研究强调了生态附加约束的等级合并如何可以揭示高山环境中局部组装过程留下的暗淡信号。