The metapopulation capacity of a fragmented landscape

Ecologists and conservation biologists have used many measures of landscape structure(1-5) to predict the population dynamic consequences of habitat l oss and fragmentation(6-8), but these measures are not well justified by po pulation dynamic theory. Here we introduce a new measure for highly fragmen ted landscapes, termed the metapopulation capacity, which is rigorously der ived from metapopulation theory and can easily be applied to real networks of habitat fragments with known areas and connectivities. Technically, meta population capacity is the leading eigenvalue of an appropriate 'landscape' matrix. A species is predicted to persist in a landscape if the metapopula tion capacity of that landscape is greater than a threshold value determine d by the properties of the species. Therefore, metapopulation capacity can conveniently be used to rank different landscapes in terms of their capacit y to support viable metapopulations. We present an empirical example on mul tiple networks occupied by an endangered species of butterfly. Using this t heory, we may also calculate how the metapopulation capacity is changed by removing habitat fragments from or adding new ones into specific spatial lo cations, or by changing their areas. The metapopulation capacity should rnd many applications in metapopulation ecology, landscape ecology and conserv ation biology.