A new look at functional beta diversity

1. The variability in species composition among a set of sampling sites, or beta diversity, is considered a key signature of the ecological processes that shape the spatial structure of species assemblages. 2. In this paper, we propose to decompose this variability into three additive components: i) the standard compositional similarity between individuals of the same species among sites, ii) the degree of functional dissimilarity between individuals of distinct species among sites, and iii) the degree of functional similarity between individuals of distinct species among sites. These three components can be used to portray the functional resemblance among sites on a ternary diagram. 3. The potential of this method is shown with real data on the functional turnover of Alpine species along a primary succession on glacial deposits in northern Italy. 4. Synthesis. With the resulting ternary diagram of ‘functional resemblance’ we can relate various aspects of taxonomic and functional variability among sites to community assembly processes more completely than just looking at individual components.