Function and Morphology
Functional diversity, as it is commonly used, is a subset of trait diversity. Functional traits are commonly morphological traits differentiated by the effects the trait has on an ecosystem (Petchey and Gaston 2006). Some ecologists have rejected the need to associate 'functional' traits to ecosystem effects and treat function diversity as a synonym of morphology. Evan Weiher (2011) in his summary of functional diversity measures states, “Some have suggested the term 'functional diversity' be restricted to measures of trait diversity that affect the functions of ecosystems (Tilman et al. 2001; Petchey and Gaston 2006). We should be wary of unnecessarily restrictive definitions for terms that are conceptual, general, or useful” (pg. 175). He further notes that general morphological trait space can be differentiated without reference to a schematic for differentiating traits. The dizzying range of mathematical measures for dividing morphological space include: distance measures, dendrogram-based measures, variance-based measures including abundances, trait evenness, convex hull mathematics to measure trait volume, and graph theory (See Weiher 2011).
Genetic diversity is considered by many to be the lowest level of a nested hierarchy of diversity comprising of genetic diversity, species diversity, and community diversity (Culver et al. 2011). Culver et al. suggest that genetic variation is “the essence of all biodiversity” (p. 208). Genetic barcoding of populations has become increasingly common due to the efficiency of new sampling techniques and the increase in computational power. Clearly, there will in the future be more genetic information available to researchers that will aid, not just our understanding of genetic difference, but also our assessments of other forms of diversity such as species diversity and phylogenetic diversity. Despite its clear practical importance, it is implausible that genetic diversity should underpin a general measure of biodiversity. This is partly because genes vary greatly in their effects so that the amount of raw genetic difference between two populations tells you relatively little about the extent to which they differ functionally and ecologically. It is also partly due to the undoubted importance of non-genetic factors in both ecology and evolution (Laland et al. 1999; West-Eberhard 2003; Jablonka and Lamb 2005).