International Biometric Society Measuring both functional and phylogenetic complexity: a new challenge for ecologists

At the heart of ecology lies the notion of variability and even complexity. The term biodiver-sity has thus been imagined to encompass ”the variety within and among living organisms, assemblages of living organisms, biotic communities, and biotic processes, whether naturally occurring or modified by humans [...]. It can be observed and measured at any spatial scale ranging from microsites and habitat patches to the entire biosphere ” [1]. Biodiversity was first measured by taxonomic indices such as species richness and species evenness. Ecologists have then integrated the historical relationships among species through phylogenies [2]. There is now an upsurge in research on functional diversity [3]. Hotspots have been defined regarding the number of species (as a measure of diversity) and the number of endemic species (as a measure of rarity). However within a community, a species can be a unique or rare source of diversity. Two concepts have thus completed ’diversity’: uniqueness and originality [4]. The uniqueness of a species will be said to be high if it displays a high amount of unique character states. The originality of a species is the average rarity of all its character states. Uniqueness and originality can be measured from phylogenies or from the functions of the species in ecosystems [5]. These components (diversity, uniqueness an