Stabilizing fluctuations in the number of individuals in fragmented populations of threatened species is an important concern in conservation biology. Theoretical studies indicate that localized perturbations, such as adding a constant number of individuals every generation, can stabilize such fluctuations in networks of local populations that are connected to each other by migration (metapopulations). If they work, such perturbations could prove to be a useful tool for managing fragmented and unstable populations. Sutirth Dey and Amitabh Joshi of Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India used laboratory metapopulations of fruitflies in the first experimental test of whether a constant localized perturbation can stabilize a real biological metapopulation.

Dey and Joshi showed that constant addition of fruitflies every generation to a particular population in the network does stabilize that population locally, but does not have any detectable effect on the dynamics and stability of the fruitfly metapopulation as a whole. Computer simulations of the experimental system using a simple and widely applicable model of population dynamics were able to recover most of the experimental results, indicating that their results are likely to be generalizable to other species. The simulations also indicated that the basic finding of no detectable effect of constant local perturbation on metapopulation dynamics and stability was robust across a much wider range of ecological scenarios than the precise conditions of their fruitfly experiment.

The study of Dey and Joshi sounds a cautionary note for ecologists and conservation biologists trying to stabilize fragmented populations in nature because it indicates that, contrary to theoretical predictions, localized perturbations are unlikely to affect the dynamics of real metapopulations.

This study will be published on February 21, 2007 in PLoS ONE, the international, peer
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Contact: Amitabh Joshi
ajoshi@jncasr.ac.in
Public Library of Science
20-Feb-2007

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