How to critically read ecological meta-analyses.

Meta-analysis offers ecologists a powerful tool for knowledge synthesis. Albeit a form of review, it also shares many similarities with primary empirical research. Consequently, critical reading of meta-analyses incorporates criteria from both sets of approaches particularly because ecology is a discipline that embraces heterogeneity and broad methodologies. The most important issues in critically assessing a meta-analysis initially include transparency, replicability, and clear statement of purpose by the authors. Specific to ecology more so than other disciplines, tests of the same hypothesis are generally conducted at different study sites, have variable ecological contexts (i.e., seasonality), and use very different methods. Clear reporting and careful examination of heterogeneity in ecological meta-analyses is thus crucial. Ecologists often also test similar hypotheses with different species, and in these meta-analyses, the reader should expect exploration of phylogenetic dependencies. Finally, observational studies not only provide the substrate for potential current manipulative experiments in this discipline but also form an important body of literature historically for synthesis. Sensitivity analyses of observational versus manipulative experiments when aggregated in the same ecological meta-analysis are also frequent and appropriate. This brief conceptual review is not intended as an instrument to rate meta-analyses for ecologists but does provide the appropriate framing for those purposes and directs the reader to ongoing developments in this direction in other disciplines.