(Georgia Institute of Technology, 2009-11)
Jiang, Lin; Pu, Zhichao
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 between theoretical predictions, and, particularly, the paucity of empirical studies. Here we used meta‐analyses to synthesize results of empirical studies published primarily in the past 2 decades on the relationship between species diversity and temporal stability. 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 multitrophic systems, with diversity stabilizing both population and community dynamics in multitrophic but not single‐trophic communities. These patterns were broadly equivalent across experimental and observational studies as well as across terrestrial and aquatic studies. We discuss possible mechanisms for population stability to increase with diversity in multitrophic systems and for diversity to influence community‐level stability in general. Overall, our results indicate that diversity can affect temporal stability, but the effects may critically depend on trophic complexity.
(Georgia Institute of Technology, 2009-03)
Jiang, Lin; Joshi, Hena; Patel, Shivani N.
Ecologists disagree on how diversity affects stability. At the heart of the controversy is the relationship between diversity and
population stability, with conflicting findings from both theoretical
and empirical studies. To help reconcile these results, we propose that this relationship may depend on trophic complexity, such that
positive relations tend to emerge in multitrophic but not singletrophic
communities. This hypothesis is based on the premise that stabilizing weak trophic interactions restrain population oscillations
associated with strong trophic interactions in diverse multitrophic
communities. We tested this hypothesis using simple freshwater bacterivorous
protist communities differing in diversity with and without
a predatory protist species. Coupling weak and strong trophic
interactions reduced population temporal variability of the stronginteracting
species, supporting the stabilizing role of weak interactions.
In keeping with our hypothesis, predation altered the overall
effect of diversity on population temporal stability and, in particular,
caused a reversal of the diversity-stability relationship (negative without
predators and positive with predators) for the strong-interacting
species. A similar role of predation was also observed when examining
the relationship between diversity and temporal stability of
community biomass. Together, these findings demonstrated strong
interactive effects of trophic interactions and diversity on temporal
stability of population and community properties.