The biology of insularity: an introduction

Insular environments, ranging from oceanic islands to fragments of once-contiguous natural systems, have long been used by biologists to test basic principles of ecology, evolution and biogeography. More recently, insular environments have figured prominently in conservation ecology, where the aim has usually been to conserve species or assemblages unique to isolated habitats. Improving the level of communication among the evolutionary biologists, theoretical ecologists and conservation biologists who study insular biotas will work to the benefit of all. This volume was inspired by a recent conference on the ecology of insular biotas, in which participants from a wide range of disciplines came together to compare ecological processes across a variety of taxonomic groups inhabiting a wide range of isolated environments. In this introduction, we point out the themes underlying these very diverse contributions. First we elaborate on the value of islands for elucidating processes underlying ecosystem functioning, population dynamics of reintroduced species, and restoration of disturbed habitats, and emphasize those areas where the use of islands could be expanded. The second section focuses on the link between ecology and evolutionary processes in insular systems and includes examples from oceanic islands, naturally patchy habitats and recently fragmented habitats. The third section illustrates some of the ways that invasive alien species on oceanic islands affect plant-animal mutualisms, particularly seed dispersal and pollination. The final section, on consequences of habitat fragmentation, focuses mainly on studies that describe the consequences that fragmentation has for plants and animals as they are forced into artificially insular environments. We close with a study that points out the differences among types of insular systems and identifies gaps in our knowledge of insular biotas, particularly the importance of explicitly incorporating patch type, age and patch-matrix contrasts in research. Finally, we recommend a greater emphasis on linking ecological theory and applied research, and improving communication between those who ask basic ecological questions and those who use insular systems for conservation.