The question of how species diversity affects ecological stability has long interested ecologists and yet remains largely unresolved. Historically, attempts to answer this question have been hampered by the presence of multiple, potentially confounding, stability concepts, confusion over responses at different levels of ecological organization, discrepancy among theoretical predictions, and particularly the paucity of empirical studies. A sufficient number of empirical diversity-stability studies have emerged in the past decade. Here we used meta-analyses to synthesize results of empirical studies that have examined the relationship between species diversity and temporal stability.
Results/Conclusions

We show that the overall effect of increasing diversity was positive for community-level temporal stability, but neutral for population-level temporal stability. There were, however, striking differences in the diversity-stability relationship between single- and multi-trophic systems, with diversity stabilizing both population and community dynamics in multi-trophic but not single-trophic systems. These patterns were broadly equivalent across experimental and observational studies as well as across terrestrial and aquatic studies. We suggest that observed diversity-stability patterns at the community level may be influenced by those at the population level, and discuss plausible mechanisms for population stability to increase with diversity in multi-trophic systems. Together, these results indicate that diversity can affect temporal stability, but the effects may critically depend on system trophic complexity.