OOS 46-8: Well-connected but empty on the inside: Active dispersal can reduce the species richness of accessible habitat patches
Gareth J. Russell1, James I. Watling2, Tomás Santos3, José Luis Tellería3, Karina Aliaga4, and Temipote Brotherson4. (1) New Jersey Institute of Technology and Rutgers University, (2) Washington University in St. Louis, (3) Universidad Complutense, (4) New Jersey Institute of Technology
Background/Question/Methods We modify MacArthur and Wilson's theory of island biogeography, which implicitly assumes ‘passive' dispersal and population dynamics, by adding choice-based immigration and emigration functions that both vary with isolation. We ﬁt the models to a large number of existing biogeographic datasets.
Results/Conclusions We show that in many cases, the modiﬁed models are preferable to the original model even given their increased complexity. For many datasets involving birds, there is evidence for a strong tendency to leave those patches that are closest to larger patches — a tendency that overwhelms the original model's assumption of a higher (passive) colonization rate and results in expectedly impoverished species richness. If real, this phenomenon has disturbing implications for conservation-oriented landscape planning. Habitat corridors, in particular, might in some circumstances have the opposite eﬀect from the one intended, leaving connected fragments worse oﬀ than before.