Patches (large and small) as islands: All systems are not created equal

<>Ever since the publication of the MacArthur Wilson Theory of Island Biogeography patchy systems of all types have been defined as islands. From cushion plants and thistles to vernal pools and conservation refuges, island theory has been invoked to predict species diversity patterns. However, these systems differ from one another and from oceanic islands in both spatial and temporal relations and we argue that as a result, different predictions are expected for different systems. Using data from a study of microbiotic crusts in arid systems we demonstrate the importance of defining patches according to several traits: permeability of the surrounding matrix, time between disturbances and patch formation relative to the surrounding matrix. Of these three traits, only the last is actually a trait of the patch itself. The other two factors can only be determined based on the organisms associated with the patches. Once we move to an organism-centered understanding of these patches we may find surprising and novel comparisons that allow us to move across scales and inform our view of ecological patterns and processes. By incorporating non-equilibrium systems into a model of insularity, this work has general implications that go beyond the scope of cryptobiotic crusts to add to the current dialogue in biogeography and in conservation ecology.