Revisiting the dimensionality of biological diversity

Biodiversity can be represented by a variety of different dimensions (e.g. functional diversity, phylogenetic diversity, genetic diversity and taxonomic diversity). While the many different representations of biodiversity can lead to a more complete description of communities, they also lead to a degree of fragmentation of the biodiversity concept. Developing a unified measure that integrates all the dimensions of biodiversity is a theoretical solution for this problem, however, it remains an operationally utopian task. Alternatively, quantifying the dimensionality of biodiversity is a way to integrate the different dimensions of biological diversity. This concept is explored in the present study. We define the dimensionality of diversity as the number of different diversity metrics needed to effectively describe biodiversity. We provide a solution that joins the two components of dimensionality (correlation and the variation of each diversity metric) in the same framework, allowing us to quantify dimensionality. We show, through a simulation study, that considering the correlation among dimensions with the variation of each dimension offers important information that is neglected when only correlation information (the component used in the current methodology to measure dimensionality) is considered. We demonstrate how to apply the proposed framework by investigating the dimensionality of South American small mammal communities (cricetids and marsupials). Our example demonstrates that the taxonomic dimension of diversity captures most of the spatial variation among these communities. We conclude by highlighting the greater understanding of dimensionality that is obtained through this method, as well as the insights it provides into the importance of each diversity metric to the whole biodiversity space, insights which can not be obtained through the current common method.