Abstract
BackgroundTwo decades of research showing that increasing plant diversity results in greater community productivity has been predicated on greater functional diversity allowing access to more of the total available resources. Thus, understanding phenotypic attributes that allow species to partition resources is fundamentally important to explaining diversity-productivity relationships.Methodology/Principal FindingsHere we use data from a long-term experiment (Cedar Creek, MN) and compare the extent to which productivity is explained by seven types of community metrics of functional variation: 1) species richness, 2) variation in 10 individual traits, 3) functional group richness, 4) a distance-based measure of functional diversity, 5) a hierarchical multivariate clustering method, 6) a nonmetric multidimensional scaling approach, and 7) a phylogenetic diversity measure, summing phylogenetic branch lengths connecting community members together and may be a surrogate for ecological differences. Although most of these diversity measures provided significant explanations of variation in productivity, the presence of a nitrogen fixer and phylogenetic diversity were the two best explanatory variables. Further, a statistical model that included the presence of a nitrogen fixer, seed weight and phylogenetic diversity was a better explanation of community productivity than other models.ConclusionsEvolutionary relationships among species appear to explain patterns of grassland productivity. Further, these results reveal that functional differences among species involve a complex suite of traits and that perhaps phylogenetic relationships provide a better measure of the diversity among species that contributes to productivity than individual or small groups of traits.
Highlights
For nearly two decades, researchers have tested the prediction that community productivity is positively related to plant diversity [1,2,3,4,5,6]
Evolutionary relationships among species appear to explain patterns of grassland productivity. These results reveal that functional differences among species involve a complex suite of traits and that perhaps phylogenetic relationships provide a better measure of the diversity among species that contributes to productivity than individual or small groups of traits
The species in the functional diversity (FD) dendrogram did not produce the same sister pairings as in the molecular phylogeny (Fig. 1), while the nonmetric multidimensional scaling (NMDS) dendrogram shows species clustering more similar to the molecular phylogeny (Fig. 1)
Summary
Researchers have tested the prediction that community productivity is positively related to plant diversity [1,2,3,4,5,6]. Researchers have advocated measuring diversity in functional attributes relevant to those critical limiting resources and assumed that this should be the best predictor of community productivity and ecosystem functioning [11,12,13]. The removal or addition of ‘‘functionally redundant’’ species may have effects on community dynamics and processes [15,16,17], indicating that there are important functional differences not captured by broad groupings. The second reason is that functional group richness tends to predict only a limited amount of variation in productivity [18] and may even explain less variation than having randomly assigned groups [19]. Two decades of research showing that increasing plant diversity results in greater community productivity has been predicated on greater functional diversity allowing access to more of the total available resources. Understanding phenotypic attributes that allow species to partition resources is fundamentally important to explaining diversity-productivity relationships
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