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Functional diversity is a component of biodiversity that concerns what organisms do, rather than, for example, their taxonomic identity (Tilman 2001, Naeem and Wright 2003, Hooper et al. 2005, Petchey and Gaston 2006). What kinds of resources do organisms exploit, where do they exploit them, and when do they exploit them? Each of these characteristics, and many others, can be a component of functional diversity. Since ecosystem processes ultimately result from the actions of organisms, knowing about these actions and summarizing them in a measure of diversity should inform about ecosystem processes (Tilman 2001, Hooper et al. 2005). Therefore, functional diversity has the potential to link morphological, physiological, and phenological variation at the individual level to ecosystem processes and patterns. One critical reason that functional diversity might link organisms and ecosystems is that it implicitly contains information about how species will compensate for the loss of another. For illustration, consider some species that are functionally rather similar, and some that are rather dissimilar. The similar species each access the same pool of resources. If one of these species is lost, no reduction in the use of that resource pool results, as the other species are present and will accordingly simply increase their use of that same resource. There will also be only a small loss of functional diversity, since the lost species was not very unique in its functional characteristics. If, however, the lost species was quite dissimilar to others in its functional traits, both functional diversity and use of the resource pool will decline in concert. Other changes …