Print PageVarious mechanisms have been proposed to explain how species richness enhances the temporal stability of community properties but these mechanisms make unique predictions about the effects of richness on the temporal stability of populations. Additionally, different mechanisms are expected to be more or less important under constant or variable environments and in single or multiple-trophic level communities. We conducted a mesocosm experiment designed to explore the effects of zooplankton richness on population and community stability in aquatic food webs. We manipulated richness under either constant or variable environments and collected time series data for population, community, and ecosystem properties spanning many generations. We used various statistical techniques to test for different diversity-stability mechanisms that included negative covariance (increased asynchronicity), statistical averaging, overyielding, selection effects, facilitation, and weak interactions.
Results/Conclusions
Our results show that zooplankton population and community stability increases in species-rich communities but that stability was not affected by environmental variability. We found evidence for increased negative covariance, statistical averaging, and weak interactions which appeared to operate simultaneously to enhance stability at the community level in these aquatic food webs. Our results suggest that some stabilizing mechanisms such as the sampling effect and overyielding which can be important in single trophic level studies may not be as important in multi-trophic food webs, whereas mechanisms such as weak interactions may become more important in food webs and can counteract the destabilizing effect that other mechanisms have on populations. In summary, predicting the effects of richness and environmental variability on population and community stability will ultimately require knowledge of the relative contributions of various mechanisms under different environmental scenarios.
