Including intraspecific variability in functional diversity

Abstract

Linking species and ecosystems often relies on approaches that consider how the traits exhibited by species affect ecosystem processes. One method is to estimate functional diversity (FD) based on the dispersion of species in functional trait space. Individuals within a species also differ, however, and an unresolved challenge is how to include such intraspecific variability in a measure of functional diversity. Our solution is to extend an existing measure to variation among individuals within species. Here, simulations demonstrate how the new measure behaves relative to one that does not include individual variation. Individual-level FD was less well associated with species richness than species-level FD in a single trait dimension, because species differed in their intraspecific variation. However, in multiple trait dimensions, there was a strong association between individual- and species-level FD and richness, because many traits result in a tight relationship between functional diversity and species richness. The correlation between the two FD measures weakened as the amount of intraspecific variability increased. Analyzing natural plant communities we found no relationship between species richness and functional diversity. In these analyses, we did not have to specify the source of intraspecific variation. In fact, the variation was only among individuals. The measure can, however, include differences in the amount of intraspecific variation at different sites, as we demonstrate. Including intraspecific variation should allow a more complete understanding of the processes that link individuals and ecosystems and provide better predictions about the consequences of extinctions for ecosystem processes.

Influence of fire history and soil properties on plant species richness and functional diversity in a neotropical savanna

“…An attribute is the particular value taken by the trait at any place and time (Violle et al 2007). In this case, functional information was site-specific, because we considered the individuals sampled at each site separately, which allowed us to include intraspecific differences among sites (Cianciaruso et al 2009). We measured stem specific density, leaf nitrogen content, and leaf phosphorus content for five individuals per species.…”

Secreted enzymatic activities of ectomycorrhizal fungi as a case study of functional diversity and functional redundancy

“…The ecological literature about the measurement of functional diversity, which captures how functional trait composition varies among assemblages, has grown during the last decade (i.e., Thompson et al 2005;Barnett and Beisner 2007). Functional diversity can be expressed as the measurement of the branch length of a dendrogram based on similarities between functional traits Gaston 2002, 2009;Cianciaruso et al 2009). …”

No correlation between the diversity and productivity of assemblages: evidence from the phytophage and predator assemblages in various cotton agroecosystems

“…The diversity index of Shannon-Weaver [32] has been extensively used as a measure of assemblage diversity. All proposed functional diversity measures have assumed that individuals in a given assemblage are equally important, even if they make disproportionate contributions to assemblage function [34]. However, several studies have reported on how variation among individuals of the same species is important for assemblage function [35,36].…”

“…However, several studies have reported on how variation among individuals of the same species is important for assemblage function [35,36]. Up to this point, none of the methods proposed for estimating functional diversity [37] give a clear approach to incorporating information about individuals [34]. Our previous research deduced the diversity index of energy flow based on the Shannon-Wiener index by ecological energetics, as a measure of the functional diversity index, which includes measures that incorporate information about the abundance, age structure, life history, and mortality of each species in a assemblage [18].…”