Functional and phylogenetic diversity as predictors of biodiversity–ecosystem-function relationships

TLDR

Phylogenetic diversity has been used to predict biodiversity effects on ecosystem functioning, yet its predictive power relative to functional diversity has not been compared across experiments. The study aimed to determine how variability in ecologically important traits reflects evolutionary divergence and to assess the relative influence of phylogenetic and functional diversity on biodiversity effects on biomass production. The authors compiled data from 29 grassland plant experiments that provided well‑described phylogenies and extensive trait measurements, enabling a comparative analysis of phylogenetic and functional diversity. They found that functional trait variation was only partially correlated with phylogenetic distances, but both phylogenetic and functional diversity predicted biodiversity effects on biomass with similar strength, with two‑ or three‑trait combinations yielding the strongest predictive power, indicating that both evolutionary history and trait diversity are valuable predictors of ecosystem functioning.

Abstract

How closely does variability in ecologically important traits reflect evolutionary divergence? The use of phylogenetic diversity (PD) to predict biodiversity effects on ecosystem functioning, and more generally the use of phylogenetic information in community ecology, depends in part on the answer to this question. However, comparisons of the predictive power of phylogenetic diversity and functional diversity (FD) have not been conducted across a range of experiments. To address how phylogenetic diversity and functional trait variation control biodiversity effects on biomass production, we summarized the results of 29 grassland plant experiments where both the phylogeny of plant species used in the experiments is well described and where extensive trait data are available. Functional trait variation was only partially related to phylogenetic distances between species, and the resulting FD values therefore correlate only partially with PD. Despite these differences, FD and PD predicted biodiversity effects across all experiments with similar strength, including in subsets that excluded plots with legumes and that focused on fertilization experiments. Two- and three-trait combinations of the five traits used here (leaf nitrogen percentage, height, specific root length, leaf mass per unit area, and nitrogen fixation) resulted in the FD values with the greatest predictive power. Both PD and FD can be valuable predictors of the effect of biodiversity on ecosystem functioning, which suggests that a focus on both community trait diversity and evolutionary history can improve understanding of the consequences of biodiversity loss.