HABITAT DETERIORATION, HABITAT DESTRUCTION, AND METAPOPULATION PERSISTENCE IN A HETEROGENOUS LANDSCAPE

Levins's unstructured metapopulation model predicts that the equilibri um fraction of empty habitat patches is a constant function of the fra ction h of suitable patches in the landscape and that this constant eq uals the threshold value for metapopulation persistence. Levins's mode l thus suggests that the minimum amount of suitable habitat necessary for metapopulation persistence can be estimated from the fraction of e mpty patches at steady state. In this paper we construct several more realistic structured metapopulation models that include variation in p atch quality and the rescue effect, These models predict both positive and negative correlations between the fractions of suitable patches a nd empty patches. The type of correlation depends in an intricate mann er on the strength of the rescue effect and on the quality distributio n of the patches to be destroyed, Empty patches can be considered as t he resource limiting metapopulation growth. Our results demonstrate th at the correlation between the fractions of suitable patches and empty patches is positive if and only if the average value of the resource decreases as the number of patches increases. (C) 1997 Academic Press.