Consistency vs. contingency of trait–performance linkages across taxa

An important approach to generalizing across different taxa and systems is to focus on functional traits rather taxonomic identity. However, this approach assumes, usually implicitly, that the same value of the same trait will have the same effect in all taxa. This assumption is probably never true in the strictest sense, but it is less clear to what extent even the direction and shape of trait–performance relationship are consistent among taxa. Wildova et al. (Oikos 116:836–852, 2007) addressed this question by manipulating traits in a highly calibrated model of clonal plants, parameterized for six sedge species. They found traits connected to growth and allocation were largely consistent in their performance effects across taxa, while morphological and architectural traits were much more contingent. This result suggests that traits not directly related to resource acquisition and use should show much less consistent patterns across systems and be less susceptible to ecological generalizations.