On the biogeography of habitat islands: the importance of matrix effects, non-core species and source-sink dynamics

Habitat islands can be defined as distinct patches of habitat surrounded by less contrasting matrix types. In contrast to true island biogeography (traditionally the study of islands surrounded by water), there have been less efforts to synthesize the myriad habitat island biogeography studies that have been published, particularly syntheses that cover the full range of habitat island types. By building on previous work, I aim to provide a review of habitat island biogeography in order to provide a blueprint for future research on habitat islands, including both naturally and anthropogenically fragmented systems. The review is organized into three main parts. First, the differences between habitat and true islands are summarized. Second, the main theoretical frameworks currently used to analyze habitat island systems are reviewed. Third, the findings of habitat island studies focused on various biological patterns are synthesized. Drawing on this synthesis, I put forward two main points regarding improving our understanding of habitat island biogeography: first, increasing the integration of matrix properties (including matrix variation across space and time) into habitat island biogeographic models and, second, testing for, and understanding the implications of, the potential prevalence of mass effects and source-sink dynamics in habitat island systems.