Spatial ecology and biological conservation

Introduction Spatial ecology and biological conservation Successful biological conservation eorts require ecologists and evolutionary biologists to simultaneously understand patterns and processes of landscape change, such as habitat loss and fragmentation, as well as detailed responses of individual populations and species to these broad-scale modi®cations. Combining these seemingly distant approaches oers the best hope for designing comprehensive conservation strategies that will maintain ecological and evolutionary processes in perpetuity. Research eorts in landscape ecology (e.g. Hobbs, 1994; Forman, 1995; Hansson et al., 1995) and population and community ecology (Levin and Paine, 1974; Wiens, 1976; Hanski and Gilpin, 1997) have recently converged into an explicit emphasis on ``spatial ecology'' (e.g. Tilman and Kareiva, 1997). Spatial ecology centers on how landscape spatial con®guration in¯uences population and community dynamics of organisms. Given increased recognition by ecologists, evolutionary biologists, and conservation biologists that ``space is important'', how can and should we practically integrate spatial information with biological conservation eorts? Habitat loss and fragmentation constitute the most ser- ious threats to earth's biological diversity, and understanding their consequences for persistence of native populations and communities remains a daunting chal- lenge for conservation biologists. The current theoretical focus on landscape spatial con®guration in ecology and conservation provides fertile conceptual background with which to enhance our understanding of the ecological and evolutionary consequences of habitat loss and fragmentation. Moreover, empirical research that emphasizes responses of organisms to spatially-structured habitats usefully links conservation biological research to practical mechanisms for conservation and restoration planning. This special issue provides innovative examples of the theoretical and practical importance of landscape spatial con®guration for biological conservation. Combin- ing ecological and evolutionary theory with empirical evidence on a range of issues crucial to biological conservation, papers in this issue focus on gene ¯ow and local adaptation, population demography and genetic variation, interspeci®c interactions, landscape heterogeneity, conservation planning, and ecological restoration. Invited papers include a mixture of ®eld studies and simulation modeling, perspectives from evolutionary, population, community, landscape, and restoration ecology, and an emphasis on plants and animals, vertebrates and invertebrates. The 13 original research articles in this issue are arranged logically into four groups. The ®rst group (Ray, Gibbs, and Petit et al.) includes both theoretical and empirical treatments of the consequences of landscape spatial heterogeneity for genetic processes within and among species populations. Ray's modeling eorts explore the in¯uences of various metapopulation struc- tures on genetic eective population size and population persistence, and she reaches the important conclusion that quantifying the scale of environmental correlation is crucial for predicting outcomes of population sub- division. Gibbs' contribution investigates how landscape structure and disturbance regimes in¯uence species demographic parameters and, ultimately, population genetic structure. Petit et al. describe the dis- tribution of genetic variation in two endangered plant species, and compare results obtained from allozymic markers and quantitative characters to assess the evolutionary potential of these restricted species. They emphasize that the type of genetic information used and the spatial scale of population isolation are crucial data for eectively designing reintroduction programs. The second group of papers (Wolf, Harrison et al., and Groom) emphasizes species dynamics in naturally- and experimentally-patchy landscapes, within the con- text of interspeci®c interactions such as plant competi- tion, herbivory, and pollination. Wolf investigates potential mechanisms for dierential reproductive suc- cess of two rare plant species in large versus small serpentine outcrops. Interestingly, she reports that pollinator eciency is higher on large than on small outcrops, due primarily to the spatial arrangement of plant patches on large outcrops. Harrison et al. observe that exotic annual grasses more easily invade small serpentine patches than large patches. They demonstrate that this spatial variation in exotic species abundance stems from proximity of propagules in the nonserpentine matrix to the edges of small serpentine patches, not from inherent dierences in habitat suitability among patches of dier- ent size. Groom shows, via experimental manipulations 0006-3207/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0006-3207(00)00201-9 Biological Conservation 100 (2001) 1±2 www.elsevier.com/locate/biocon

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Spatial ecology and biological conservation