A constraint-based model reveals hysteresis in island biogeography

AimWe present a Constraint-based Model of Dynamic Island Biogeography (C-DIB) that predicts how species functional traits interact with dynamic environments to determine the candidate species available for local community assembly on real and habitat islands through time.\n\nLocationReal and habitat islands globally.\n\nMethodsWe develop the C-DIB model concept, synthesize the relevant literature, and present a toolkit for evaluating model predictions for a wide variety of \"island\" systems and taxa.\n\nResultsThe C-DIB model reveals that as islands cycle between phases of increasing or decreasing size and connectivity to a source pool, the dominant process driving species presence or absence switches between colonization and extinction. Both processes are mediated by interactions between organismal traits and environmental constraints. Colonization probability is predicted by a species ability to cross the intervening matrix between a population source and the island; population persistence (or extinction) is predicted by the minimum spatial requirements to sustain an isolated population. The non-random distributions of mammals on islands of the Sunda Shelf and Great Basin \"sky islands\" provide example study systems for evaluating the C-DIB model.\n\nMain conclusionsBecause different suites of traits impose constraints on the processes of colonization and extinction, similar environmental conditions can host different candidate species despite the same predicted richness. Thus, the model exemplifies the specific yet underappreciated role of hysteresis -the dependency of outcomes not only on the current system state -but also the historical contingency of environmental change in affecting populations and communities in insular systems.