Connectivity between habitat patches is often seen as binary, with patches considered either connected or not. In reality, however, connections between habitat patches are dynamic; variability in external conditions may change the strength of links between patches or lead to patches periodically connecting and reconnecting. We used a network-based single-species metapopulation model to evaluate how population persistence and patch occupancy are affected by different forms of temporal dynamism in connectivity. In metapopulations the ratio between the rate at which patches suffer extinction and are recolonised predicts overall metapopulation extinction. Under a wide range of extinction-colonisation ratios we simulated scenarios with: (i) the weakening of patch connections and (ii) connectivity between patches varying over time as a function of structural characteristics such as connection length or network importance.
Results/Conclusions
Our modelling shows that metapopulation dynamics are sensitive to both the magnitude of change in habitat connectivity and the temporal structure of these changes. In all cases there are abrupt thresholds in the extinction-colonisation ratio beyond which metapopulation persistence collapses. Simply considering connectivity in a non-binary way (by weighting links between patches as a function of distance) strongly affected metapopulation dynamics and persistence. The loss of a constant fraction of total links at each time-step had less effect, presumably because changes in connectivity occurred more quickly than the underlying population dynamic. However, temporal autocorrelation in connectivity loss (e.g. many rapid changes vs. fewer but more persistent ones) decreases the extinction-colonisation threshold at which extinction occurred and interacted most strongly with the specific links between habitats that were lost. If we are to understand the dynamics of spatially separated populations we need to see connectivity as a dynamic landscape property. That metapopulation dynamics are affected not only by the amount of connectivity loss but also the temporal dynamics of that loss and its location is important for efforts that seek to increase landscape connectivity.