CONSERVATION OF FRAGMENTED POPULATIONS

In this paper we argue that landscape spatial structure is of central importance in understanding the effects of fragmentation on population survival. Landscape spatial structure is the spatial relationships am ong habitat patches and the matrix in which they are embedded Many gen eral models of subdivided populations make the assumptions that (I) al l habitat patches are equivalent in size and quality and (2) all local populations (in the patches) are equally accessible by dispersers. Mo dels that gloss over spatial details of landscape structure can be use ful for theoretical developments but will almost always be misleading when applied to real-world conservation problems. We show that local e xtinctions of fragmented populations are common. From this it follows that recolonization of local extinctions is critical for regional surv ival of fragmented populations. The probability of recolonization depe nds on (1) spatial relationships among landscape elements used by the population, including habitat patches for breeding and elements of the inter-patch matrix through which dispersers move (2) dispersal charac teristics of the organism of interest, and (3) temporal changes in the landscape structure For endangered species, which are typically restr icted in their dispersal range and in the kinds of habitat through whi ch they can disperse, these factors are of primary importance and must be explicitly considered in management decisions.