The effect of niche filtering on plant species abundance in temperate grassland communities

1. Niche filtering predicts that abundant species in communities have similar traits that are suitable for the environment. However, niche filtering can operate on distinct axes of trait variation in response to different ecological conditions. Here, we use a trait-based approach to infer niche filtering processes and (1) test if abundant and rare species in grassland communities are differently positioned along distinct axes of trait variation, (2) determine if these trait variation axes, as well as phylogenetic and functional similarities, drive species relative abundance (aboveground cover) within communities, and (3) explore if these relationships vary across grassland types and macro-climatic gradients. 2. We analysed species abundance in a set of ~2,000 vegetation plots from temperate grasslands in Central Europe as a function of species position along three axes of trait variation: the 'Plant Size Spectrum' (PSS), the 'Leaf Economics Spectrum' (LES), and the 'Lifespan/Clonality Spectrum' (LCS). We also used phylogenetic and functional similarities in the multi-dimensional trait space as predictors of species abundance. We compared our results among alpine, wet, mesic, and dry grasslands and tested if the effect of the predictors on species abundance was significant across macro-climatic gradients. 3. Compared to abundant species, rare species in grassland communities were more commonly annual and non-clonal, had lower stature and smaller leaves and seeds, and relied on more acquisitive leaf economics. Our predictors significantly explained species abundance in approximately one-third of the plots. LES was the most important predictor across all plots, with the most prominent effect in alpine and dry grasslands and areas with more extreme temperatures. In contrast, in mesic and wet grasslands and grasslands located in warmer and less seasonal regions, species abundance was best predicted by phylogenetic similarities between species, with Poaceae species becoming more abundant. 4. Our study explored trait-abundance relationships for different community types across a large area and broad macro-climatic gradients. We conclude that niche filtering, and particularly resource-acquisition trade-offs, drives species abundance in temperate grassland communities of Central Europe. Our findings emphasize the interaction between local environmental conditions and plant function in determining community assembly.The dataset contains 3 files: 1. "metadata.xls": It contains the necessary information to interpret the other files. 2. "sites_x_species.csv": It contains the list of species and their abundances in sampled vegetation plots. 3. "sites_x_predictor.csv": It contains the macroclimatic variables (PCA axes) in each vegetation plot, and their classification into grassland vegetation types. Funding provided by: Grantová Agentura České RepublikyCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001824Award Number: 19-28491