The dimensionality of biological diversity revisited

Biodiversity can be represented by a variety of different dimensions (e.g. taxonomic diversity [operationalized mainly as species richness], functional diversity, phylogenetic diversity, genetic diversity). While the many different representations of biodiversity can lead to a more complete understanding of its variability across scales, they also lead to some degree of 9fragmentation9 of the concept, and do not provide insight into the intrinsic multidimensionality embedded in biodiversity. Developing a unified measure that integrates all the known dimensions of biodiversity is a theoretical solution for this problem; however, it remains an operationally utopian task. In this study we explore the concept of dimensionality of biological diversity and propose a way to integrate different dimensions. We define dimensionality of diversity as the number of dimensions needed to effectively describe biological diversity. We also provide an operational framework to quantify the concept and an example of the proposed framework using South American small mammal communities (cricetids and marsupials). Our results demonstrate that the taxonomic dimension of diversity captures most of the variation among these communities across space, in detriment to the functional and phylogenetic dimensions of diversity. We conclude by highlighting the need for considering two components of dimensionality — the correlation among dimensions and variance — in the same framework.