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 species abundances 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. Based on this geometrical interpretation of additive diversity decomposition, we then suggest an alternative way for calculating an analog of the DISC coefficient directly from the centroids of two species plots in multivariate phylogenetic space. The key to this method is that the centroids can be easily calculated by applying a principal coordinate analysis (PCoA) to the corresponding species phylogenetic distances. Finally, to show the potential of the DISC coefficient for analyzing the relationship between community structure and ecosystem functioning, we used the proposed measure by comparing phylogenetic and functional changes in plant communities along a primary succession on a glacier foreland in northern Italy. Our results show that changes in Grime's CSR functional classification of plant assemblages as competitors (C), stress-tolerators (S) and ruderals (R) along the successional gradient are also reflected in phylogenetic changes, indicating that species sorting by environmental filtering tends to favor the co-occurrence of phylogenetically related species. From a more theoretical viewpoint, the relationship between the proposed measure and the DISC coefficient helps in shedding new light on the additive decomposition of biological diversity into alpha, beta and gamma components.