Why are metapopulations so rare?

Background/Question/Methods

Roughly forty years after its introduction, the metapopulation concept is central to population ecology. The notion that local populations and their dynamics may be coupled by dispersal is without any doubt of great importance for our understanding of population-level processes.

A metapopulation describes a set of subpopulations linked by (rare) dispersal events in a dynamic equilibrium of extinctions and recolonizations. In the large body of literature that has accumulated the term “metapopulation” is often used in a very broad sense - most of the time simply implying spatial heterogeneity. A number of reviews have recently addressed this problem and have pointed out that, despite the large and still growing popularity of the metapopulation concept, there are only very few empirical examples that conform with the strict classical metapopulation (CM) definition.

In order to understand this discrepancy between theory and observation, we use an individual-based modelling approach which allows us to pinpoint the environmental conditions and the life-history attributes required for the emergence of a CM structure.

Results/Conclusions

We find that CM dynamics are restricted to a specific parameter range at the border between spatially structured but completely occupied and globally extinct populations. Considering general life-history attributes our simulations suggest that CMs are unlikely to be observed in vertebrates but may eventually occur in arthropod species.

Since the specific type of spatial population structure determines conservation concepts, our findings have important implications for conservation biology - a research area which relies heavily on the metapopulation approach for deriving conservation strategies.