A new look at functional beta diversity

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. In this paper, we propose to decompose this variability into three additive components: i) the standard similarity in the (relative) abundances of 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, or beta redundancy. These three components can be used to portray the functional resemblance among sites on a ternary diagram. 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. 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.