The mismeasure of islands: implications for biogeographical theory and the conservation of nature

The importance of islands for our understanding of evolution, ecology, and biogeography cannot be overstated. Although MacArthur & Wilson’s (1967) classic monograph and foundation for the Equilibrium Theory of Island Biogeography (ETIB) has been largely invalidated and superseded by new field data and more realistic concepts, there are still key aspects of the ETIB paradigm that continue to influence basic biogeographical thinking and its application in conservation science today. It is the purpose of this paper to re-examine the concept of insularity and its use and application in recent biogeographical literature as well as in contemporary conservation biology. The specific objectives are (1) to evaluate the interpretation of biogeographical data from an island-centric rather than from a taxon dispersal perspective, (2) to propose the application of functional geographical criteria to distinguish islands from spatial entities on mainlands, and (3) to reflect on the application of biogeographical concepts in conservation science. My aim is to reconceptualize the field of island biogeography. In particular, I wish to add evidence on the nature of oceanic islands, to contrast oceanic life to that of continents, and to discourage the application of ETIB concepts to the increasingly triage-pressured field of conservation biology.