On plot-to-plot dissimilarity measures based on species functional traits

There are many different metrics for expressing the dissimilarity between two samples or plots. The large majority of these dissimilarity measures attempt to summarize different aspects of plot-to-plot dissimilarity based either on species presences and absences within plots or on species abundances. Here, we propose a new parametric measure of plot-to-plot functional dissimilarity that incorporates information about the degree of functional dissimilarity between species. This measure is obtained from the combination of Hurlbert's 'expected species diversity' with one dissimilarity coefficient of the 'Bray-Curtis family' and calculates the expected functional dissimilarity between the species in plot A and their functional nearest neighbors in plot B if m individuals are chosen randomly with replacement from each of the two plots. Due to its parametric nature, the proposed measure has a different sensitivity to the presence of rare and abundant species within plots as a function of the selected parameter value.