The implications of asymmetric dispersal for metapopulation dynamics and conservation.

摘要

Variations in movement have broad implications for many areas of ecology and evolution. For instance, in metapopulation theory, movement plays an important role promoting (meta)population persistence over time. Most metapopulation modeling approaches describe patch connectivity using pair-wise Euclidean distances resulting in the simplifying assumption of a symmetric connectivity pattern. Symmetric connectivity may be rarely observed in nature where organisms move responding to environmental cues or advection sources through heterogeneous landscapes. Assuming symmetric dispersal when movement is asymmetric may result in biased estimates of colonization, extinction and persistence, which has important implications for management and conservation. Here I studied the implications of asymmetric connectivity for patch colonization and extinction. I leveraged a long-term, time-series on colonization-extinction dynamics in the wind-dispersed orchid Lepanthes rupestris and found that models that accounted for these asymmetries had better fit. The implications of asymmetric connectivity to metapopulation dynamics may be contingent on the driving mechanism behind them. I used a combination of an observational study of individual movements and translocation experiments to test for possible mechanisms of directed movement in the cactus-feeding insect, Chelinidea vittiger and found that variations in patch size were the most important driver of directed movements in this species. I also developed a novel site selection model that optimally selects patches that will best preserve connectivity given a worst-case disturbance scenario.