Short-term instabilities and long-term community dynamics (original) (raw)

Competition in a temporally variable environment leads to sequences of short-term instabilities that in some cases are the mechanism of long-term coexistence; in other cuses they promote long-term instability. Recent work associates long-term stability with a positive relationship between environmental and competitive effects and with population growth rates that are buffered against iointly unfavorable environmental and competitive events. Buffered growth rates arise from population subdivision over life-history stages, microenvironments or phenotypes. A distinct but related mechanism of longterm stability relies on population growth rates that are nonlinear functions of competition. New ways of understanding and investigating species diversity follow from these results. Shorkterm Instabilities and Longterm Community Dynamics Although it is recognized that the stability of an ecological community depends on the temporal scale on which it is viewed, it is not well-appreciated that in some systems long-term stability may be a consequence of short-term instabilities. As viewed here, long-term stability is the tendency of a community to recover from extreme perturbations of the densities of any of its component species'. Short-term instabilities are trends on a short timescale that would lead to extinctions if extrapolated into the future (Box 11. We review models that demonstrate the potential for short-term instabilities to contribute to long-term coexistence of species, and we discuss data that are consistent with these models.