Quality of meta-analyses in freshwater ecology: A systematic review

1. Given the increasing use of systematic reviews and meta-analyses in ecology, their protocols should be closely followed to ensure quality. Several checklists are available to guide researchers towards a high-quality meta-analytic study. Freshwater ecology studies have a tradition of using experimental studies, which provide the ideal data to test hypotheses using meta-analysis. 2. Here, we evaluated the quality of 114 meta-analyses in freshwater ecology and 86 meta-analyses in ecology and evolution for comparative purposes. 3. We found that many studies are still using the term meta-analysis incorrectly and that this error persisted over time. The quality of the studies that did conduct a formal meta-analysis has improved. Thus, we speculate that available guidelines are being effective in improving the quality of meta-analytic studies. Quality was not associated with the impact factor of the journal where the meta-analyses were published or with the average number of citations. 4. In addition to the incorrect use of the term, we found that many studies failed to: report heterogeneity statistics, evaluate temporal changes in effect size, conduct publication bias analyses, address the collinearity among moderators, and provide the data. In general, meta-analyses in ecology and evolution have only a slightly better average score than meta-analyses in freshwater ecology. 5. Although the quality of meta-analyses in freshwater ecology has improved over time, there is much room for improvement. Authors should not label their studies as meta-analyses if these methods were not used. Compliance with checklists should be widely fostered as meta-analyses are increasingly being used to summarise findings in different areas of ecology. Authors, reviewers, and editors should use checklists to improve the quality of meta-analyses in freshwater ecology.