In nature, environmental conditions are forever changing, and movement by organisms across space can link disparate local habitats. The interplay of temporal variation and movement can generate surprising emergent properties in ecological systems. In their article in the August 2005 issue of The American Naturalist, Manojit Roy, Robert D. Holt, and Michael Barfield consider populations inhabiting "sink" habitats, where conditions are so poor that, on average, populations decline towards extinction, so that persistence requires external immigration from an external "source."
Prior studies have demonstrated that temporal variation in local growth rates with a positive autocorrelation (i.e., short-term predictability, with "runs" of good years and bad years) can increase the average abundance of sink populations a phenomenon dubbed the "inflationary effect." Here, the authors show that the inflationary effect can permit an array of sink populations coupled by migration to persist, even with no immigration from a persistent external source.
Total metapopulation abundance can be large given a high autocorrelation and large movement rates. Because there are many reasons to expect positive autocorrelation in growth rates in natural environments, these results may help explain a puzzle in conservation biology how some species seem able to persist in harsh environments with low average growth rates.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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