How the equilibrium assumption is addressed in empirical tests of major ecological theories
Data files
Oct 16, 2025 version files 85.85 KB
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equilibrium_conundrum_papers_final.csv
83.61 KB
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README.md
2.24 KB
Abstract
The idea that natural systems tend to be at equilibrium dates back to the origin of the field of ecology and continues to underlie most ecological theory. However, empirical evidence for equilibrium dynamics in nature and in experiments is surprisingly elusive. Here, we address this conundrum by first exploring the history of equilibrium in ecological theory and the evidence for equilibrium dynamics in natural systems. We then search the literature to quantify how empiricists deal with equilibrium in their research, and we address barriers to integrating equilibrium into empirical work by providing step-by-step instructions for determining whether a population is at equilibrium. Next, we lay out three ways that equilibrium is embedded in theory, and for each, outline when meeting the equilibrium assumption in empirical tests is critical for scientific inference, and when it is possible to relax this assumption. And finally, we present concrete steps that empiricists and theoreticians can each take in order to meet in the middle when it comes to equilibrium. We hope that this paper will stimulate new discussions from researchers from across the theory-empirical divide about this longstanding issue.
Tess N. Grainger, Keila Stark, Chuliang Song, Matthew A. Barbour, Rachel M. Germain
https://doi.org/10.5061/dryad.5hqbzkhgb
Context
The equilibrium concept is ubiquitous in ecology, yet the ways in which it is considered and applied in different ecological theories varies significantly. We investigated how often the top-cited papers in common ecological theories acknowledge and address the equilibrium assumption.
We conducted a Web of Science search on July 24th, 2024, of the top cited articles that test five major equilibrium-based ecological theories: Modern Coexistence Theory, Tilman’s Resource Ratio (R*) Theory, the Metabolic Theory of Ecology, Metapopulation Theory, and Neutral theory. We developed search strings iteratively, adding in additional terms specific to each theory (e.g., "stabilizing niche differences" for Modern Coexistence Theory) in order to capture a substantial portion of the literature. Abstracts were screened to verify that the papers described direct empirical tests of the theory’s predictions (i.e., no meta-analyses or purely modelling papers). We retained 10 top-cited papers for each theory, for a total of 50 papers listed in the enclosed data file (equilibrium_conundrum_papers_final.csv.
Description of the data and file structure
The CSV file contains the following information:
Citation information:
Columns for "Publication Year", "Author(s)", "Title", "Journal", "Pages", "Issue", "Volume"
Which major ecological theory the paper tested ["Theory"]
mte = Metabolic Theory of Ecology (Brown et al. 2004)
mct = Modern Coexistence Theory (Chesson 2000)
metapopulation = Metapopulation Theory (Levins 1969)
neutral = Unified Neutral Theory of Biodiversity (Hubbell 2001)
R* = Tilman's Resource Ratio Theory (Tilman 1982)
Whether the equilibrium assumption is acknowledged ["Mentions equilibrium criterion?"]
yes/no
If equilibrium assumption is acknowledged, how the authors address it in their study ["How they engage with equilibrium"]
Modelling approach
Verbally assumed
Observed system or proxy variable at equilibrium
Violation of equilibrium explains results
This dataset is the outcome of a Web of Science search on July 24th, 2024 of the top cited articles that test five major equilibrium-based ecological theories: Modern Coexistence Theory, Tilman’s resource ratio (R* theory), the Metabolic Theory of Ecology, Metapopulation Theory, and Neutral theory. We developed search strings iteratively, adding in additional terms highly specific to those theories (e.g., "stabilizing niche differences" for Modern Coexistence Theory) in order to capture a substantial portion of the literature. Abstracts were screened to verify that the papers involved empirical tests of the theory’s predictions, and we retained 10 papers for each theory, for a total of 50 papers.