A classical measure of phylogenetic dissimilarity and its relationship with beta diversity

Rao developed the DISC dissimilarity coefficient to summarize the dissimilarity between pairs of plots based on speciesabundances and interspecies dissimilarities. In this paper, we review the potential of the DISC coefficient for assessing plot-to-plot phylogenetic dissimilarity. First, the relationship between plot-to-plot dissimilarity and additive beta diversity is discussed.Next, we show that additive diversity decomposition can be interpreted in terms of a sum of classical Euclidean distances. Basedon this geometrical interpretation of additive diversity decomposition, we then suggest an alternative way for calculating ananalog of the DISC coefficient directly from the centroids of two species plots in multivariate phylogenetic space. The key to thismethod is that the centroids can be easily calculated by applying a principal coordinate analysis (PCoA) to the correspondingspecies phylogenetic distances. Finally, to show the potential of the DISC coefficient for analyzing the relationship betweencommunity structure and ecosystem functioning, we used the proposed measure by comparing phylogenetic and functionalchanges in plant communities along a primary succession on a glacier foreland in northern Italy. Our results show that changesin Grime’s CSR functional classification of plant assemblages as competitors (C), stress-tolerators (S) and ruderals (R) along thesuccessional gradient are also reflected in phylogenetic changes, indicating that species sorting by environmental filtering tendsto favor the co-occurrence of phylogenetically related species. From a more theoretical viewpoint, the relationship between theproposed measure and the DISC coefficient helps in shedding new light on the additive decomposition of biological diversityinto alpha, beta and gamma components.