One large, several medium, or many small?

The optimal configuration (number and size) of nature reserves has been addressed in a large number of empirical and theoretical studies, but no coherent conclusion has yet been arrived at. In this paper, we study this problem in the context of metapopulation dynamics by simulation and with a concern for the target species that is subjected to an Allee effect. The results indicate that the metapopulation survival time increases first and then decreases as the number of reserves increases and the size of each reserve decreases. An intermediate reserve number exists which is optimal for metapopulation persistence when the Allee effect of the corresponding local population is moderate. But the metapopulation cannot persist for long no matter how many reserves there are, if the Allee effect is too severe. The extinction probability and migration rate also seriously affect the metapopulation persistence and the optimal number of reserves. In addition, the optimal configuration of reserves for long-term persistence is more rigorous for a small habitat area. The results in this paper may provide important implications for nature conservation.