Fluctuation-Dependent Mechanisms
Fluctuation-dependent mechanisms are
those that require fluctuations over time either in population
densities or environmental factors for their operation. In the
study of species coexistence, the storage
effect and nonlinear
competitive variance are fluctuation-dependent mechanisms of
species coexistence. Naturally, these are to be contrasted with
fluctuation-independent
mechanisms. This distinction was first presented in Chesson
(1994), and discussed in more detail in Chesson (2000). The
related concepts to do with spatial variation are termed
variation-dependent,
and variation-independent
mechanisms. The
old distinction between equilibrium and nonequilibrium, as
discussed in Chesson and Case (1986), has become the modern distinction
between fluctuation-dependent and fluctuation-independent
mechanisms. The reason for the change in terminology is discussed
in Chesson (2000): equilibrium means different things to different
people. In Chesson and Case (1986), the equilibrium was a point
equilibrium, but some people point out that limit cycles and stationary
probability distributions are in a certain sense equilibria too. So the
terms were changed to contain common words with less labile
meaning.
References
Chesson, P.L.,
Case, T.J. 1986. Nonequilibrium community theories: chance,
variability, history, and coexistence. Pp 229-239 in J. Diamond and T.
Case, eds, "Community Ecology," Harper and Row
Chesson, P. 2000.
Mechanisms of maintenance of species diversity. Annual Review of
Ecology and Systematics 31, 343-66.