Introduction

Abstract

The distribution of biodiversity is a, if not the, major focus of ecologists. Specifically, ecologists often investigate the spatial or temporal trends in biodiversity levels within a particular study region or across the planet. The study of biodiversity has traditionally focused on quantifying patterns of species diversity or species richness across some type of gradient and determining the potential processes that have produced the observed pattern. This approach is a cornerstone of ecological investigations and thinking regarding biodiversity. However, there are two clear limitations to this species-centric approach. First, biodiversity is not simply species diversity. Biodiversity also includes the phylogenetic, genetic, and functional diversity in an assemblage [1]. Indeed, species diversity may even be the least informative of all of these dimensions of biodiversity. For example, regions could have the same exact species diversity, but very different levels of phylogenetic and functional diversity and therefore very different levels of biodiversity. Or they could have very similar levels of functional and phylogenetic diversity despite large differences in their species richness [2--5]. Thus, attempting to determine the processes that produce biodiversity cannot be obtained by examining only one component of biodiversity. A second challenge for the species-centric approach to studying biodiversity that is perhaps more important than the first one is that species names are relatively information poor. While they are fundamental to biology, they convey little information regarding the function or evolutionary history of species, and such information is critical for determining the processes that have combined to produce the observed levels of biodiversity. These inherent limitations of a species-centric approach suggest that a more pluralistic approach to studying biodiversity is needed in order to obtain a mechanistic understanding of how patterns of biodiversity are formed [6--13]. In particular, a biodiversity synthesis will necessarily require the consideration of the interrelationships between the three primary components of biodiversity---species diversity, functional trait diversity, and phylogenetic diversity [1]. Ecologists are now embracing this reality and have altered their research programs accordingly. The number of phylogenetic- and functional trait-based analyses in ecology has skyrocketed in recent years resulting in hundreds of publications. Indeed, entirely new fields in ecology have formed such as community phylogenetics, and new grant programs have sprung up such as the United States National Science Foundation's Dimensions of Biodiversity program.