An excess of niche differences maximizes ecosystem functioning

Oscar Godoy,Luis Matías,Eric Allan,Ignacio M Pérez-Ramos,Lorena Gómez-Aparicio

doi:10.1038/s41467-020-17960-5

Abstract

Ecologists have long argued that higher functioning in diverse communities arises from the niche differences stabilizing species coexistence and from the fitness differences driving competitive dominance. However, rigorous tests are lacking. We couple field-parameterized models of competition between 10 annual plant species with a biodiversity-functioning experiment under two contrasting environmental conditions, to study how coexistence determinants link to biodiversity effects (selection and complementarity). We find that complementarity effects positively correlate with niche differences and selection effects differences correlate with fitness differences. However, niche differences also contribute to selection effects and fitness differences to complementarity effects. Despite this complexity, communities with an excess of niche differences (where niche differences exceeded those needed for coexistence) produce more biomass and have faster decomposition rates under drought, but do not take up nutrients more rapidly. We provide empirical evidence that the mechanisms determining coexistence correlate with those maximizing ecosystem functioning.

Highlights

Ecologists have long argued that higher functioning in diverse communities arises from the niche differences stabilizing species coexistence and from the fitness differences driving competitive dominance
Niche and fitness differences are defined for pairs of species[18] in the annual plant model, but complementarity and selection effects are commonly measured at the community level[10]
Pairwise differences in selection effects were larger when niche differences were small and generally when fitness differences were large, the opposite trend was found for soil N under control conditions (Fig. 2)

Summary

Introduction

Ecologists have long argued that higher functioning in diverse communities arises from the niche differences stabilizing species coexistence and from the fitness differences driving competitive dominance. Empirical support for these connections is currently lacking because studies have not quantified selection and complementarity effects together with the determinants of competitive outcomes (i.e., niche and fitness differences) Both the two biodiversity effects and the two determinants of coexistence can be driven by multiple underlying mechanisms: complementarity and niche differences for instance can be driven by interspecific differences in resource use, the action of specialist natural enemies or facilitation, amongst other processes[15]. Negative selection effects arise when low-yielding species increase their functioning in mixtures, which could be driven by them experiencing lower inter than intraspecific competition and this should drive niche differences between them Given this interdependence of coexistence mechanisms[21], a question worth asking is what combination of niche and fitness differences maximizes functioning. Comparing these two possibilities will allow us to determine the link between the determinants of competitive outcomes and ecosystem functioning

Methods

Results

Conclusion