Functional coexistence theory: Identifying mechanisms linking biodiversity and ecosystem function
Journal
Ecological Monographs
Journal Volume
95
Journal Issue
3
Start Page
e70033
ISSN
0012-9615
1557-7015
Date Issued
2025-10-21
Author(s)
Abstract
Theory and experiments show that diverse ecosystems often have higher levels of function (for instance, biomass production), yet it remains challenging to identify the biological mechanisms responsible. We synthesize developments in coexistence theory into a general theoretical framework linking community coexistence to ecosystem function. Our framework, which we term functional coexistence theory, identifies three components determining the total function of a community of coexisting species. The first component directly corresponds to the niche differences that enable pairwise species coexistence and to the complementarity component from the additive partition of biodiversity effects. The second component measures whether higher functioning species also have higher fitness under competition, providing a missing link between the additive partition's selection effect and modern coexistence theory's concept of equalization. The third component is least well studied: reducing functional imbalances between species increases niche difference's positive effect on function. Using a mechanistic model of resource competition, we show that our framework can link the structure and function of multispecies communities and that it can predict changes in coexistence and ecosystem function along gradients of resource availability. In particular, we expect the effect of resource level on biodiversity–function relationships to be limited in magnitude and variable in sign because it should be primarily mediated by fitness. Next, we confirm our theoretical expectations by fitting this model to data from a classic plant competition experiment. Finally, we apply our framework to simulations of multiple ecosystem functions, demonstrating that relationships between niche, fitness, and function also predict a community's multifunctionality, or ability to simultaneously show high levels of multiple functions. Taken together, our results highlight fundamental links between species coexistence and its consequences for ecosystem function, providing an avenue toward mechanistic and predictive understanding of community–ecosystem feedbacks.
Subjects
coexistence
complementarity
fitness difference
mechanistic model
multifunctionality
niche difference
selection
transgressive overyielding
Publisher
Wiley
Type
journal article