DOI: 10.5061/dryad.s2h01
title: Data from: Species richness, but not phylogenetic diversity, influences community biomass production and temporal stability in a re-examination of 16 grassland biodiversity studies

description: 1.Hundreds of experiments have now manipulated species richness of various
 groups of organisms and examined how this aspect of biological diversity
 influences ecosystem functioning. Ecologists have recently expanded this
 field to look at whether phylogenetic diversity among species, often
 quantified as the sum of branch lengths on a molecular phylogeny leading
 to all species in a community, also predicts ecological function. Some
 have hypothesized that phylogenetic divergence should be a superior
 predictor of ecological function than species richness because
 evolutionary relatedness represents the degree of ecological and
 functional differentiation among species. But studies to date have
 provided mixed support for this hypothesis. 2.Here, we re-analyze data
 from 16 experiments that have manipulated plant species richness in
 grassland ecosystems and examined the impact on aboveground biomass
 production over multiple time points. Using a new molecular phylogeny of
 the plant species used in these experiments, we quantified how the
 phylogenetic diversity of plants impacts average community biomass
 production as well as the stability of community biomass production
 through time. 3.Using four complementary analyses we show that, after
 statistically controlling for variation in species richness, phylogenetic
 diversity (the sum of branches in a molecular phylogenetic tree connecting
 all species in a community) is neither related to mean community biomass
 nor to the temporal stability of biomass. These results run counter to
 past claims. However, after controlling for species richness, phylogenetic
 diversity was positively related to variation in community biomass over
 time due to an increase in the variances of individual species, but this
 relationship was not strong enough to influence community stability. 4.In
 contrast to the non-significant relationships between phylogenetic
 diversity, biomass, and stability, our analyses show that species richness
 per se tends to increase the mean biomass production of plant communities,
 after controlling for phylogenetic diversity. The relationship between
 species richness and temporal variation in community biomass was either
 positive, non-significant or negative depending on which analysis was
 used. However, the increases in community biomass with species richness,
 independently of phylogenetic diversity, always led to increased
 stability. These results suggest that phylogenetic diversity is no better
 as a predictor of ecosystem functioning than species richness.
 5.Synthesis. Our study on grasslands offers a cautionary tale when trying
 to relate phylogenetic diversity to ecosystem functioning suggesting that
 there may be ecologically important trait and functional variation among
 species that is not explained by phylogenetic relatedness. Our results
 fail to support the hypothesis that the conservation of evolutionarily
 distinct species would be more effective than the conservation of species
 richness as a way to maintain productive and stable communities under
 changing environmental conditions.
description: DATA Dryad Venail et al.
 Functional Ecology