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Ecological meta-analyses often produce unwarranted results
Scott D Peacor1, Chao Song2, James R Bence1
1Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan, USA.
Ecology
|December 8, 2025
Summary
Ecologists often overlook nonindependence in meta-analysis (MA), where results from the same paper can be too similar. This study shows ignoring this issue, called within-paper nonindependence, can lead to incorrect ecological conclusions.
Area of Science:
- Ecology
- Statistical Methods
Background:
- Meta-analysis (MA) is crucial in ecology for synthesizing research findings.
- Ecologists are increasingly aware of nonindependence issues, similar to pseudoreplication in experiments.
- Within-paper nonindependence, where multiple effect sizes originate from a single study, has been largely neglected in MA.
Purpose of the Study:
- To evaluate the impact of within-paper nonindependence on ecological meta-analyses.
- To assess whether standard methods adequately account for nonindependence in MA.
Main Methods:
- Obtained original data from 20 published ecological meta-analyses.
- Reconstructed analyses for 14 MAs that did not account for a paper effect.
- Employed three approaches: adding 'nonsense' variables, a random dummy variable, and incorporating random paper effects.
Main Results:
- Nonsense variables and random dummy variables were statistically significant more often than expected (25%-50% and 38% vs. 5%), indicating significant within-paper nonindependence.
- Adding random paper effects to 14 MAs revealed significant nonindependence in 12, often altering original conclusions.
- Even with random effects, nonindependence issues persisted, suggesting complexity beyond simple modeling.
Conclusions:
- Within-paper nonindependence poses substantial problems in ecological meta-analyses.
- Failure to properly account for nonindependence can lead to unwarranted conclusions.
- Addressing nonindependence requires careful consideration of dependencies among effect sizes within studies.
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