The population dynamics of a metapopulation are affected by factors beyond the within-patch dynamics of its constituent subpopulations, including its network topology, which can be characterized by the distance and degree of connectivity between subpopulations. Habitat patches may be connected by many dispersal pathways or few. In addition to mean degree of connectivity, metapopulations can vary in the way in which dispersal pathways are clustered across the landscape, ranging from entirely homogeneous metapopulations, in which dispersal pathways are spaced very evenly and all subpopulations are equally connected to their neighbors, to strongly heterogeneous metapopulations, in which dispersal pathways are more clustered in space and most subpopulations are connected to only one or two neighbors while a few “hub” subpopulations are more highly connected. A highly connected subpopulation may be recolonized by many neighboring populations, increasing its probability of persistence through time. A metapopulation containing such subpopulations, therefore, is also expected to have a higher probability of persistence than a metapopulation with fewer highly connected subpopulations. I tested these expectations by culturing the bacterium Pseudomonas syringae in Metapopulation Microcosm Plates, which are similar to standard 96-well plates in size and shape, but contain corridors that can connect the wells in any configuration desired. I compared population growth between treatments that varied in the spatial clustering of dispersal corridors and rate at which subpopulation re-colonization could occur.
Results/Conclusions
Spatial clustering of dispersal corridors and rate of subpopulation re-colonization had strong and interacting effects on metapopulation persistence. Metapopulations with a highly clustered dispersal corridors had greater variance in subpopulation size and persistence, but higher metapopulation persistence overall, while increasing the rate of re-colonization decreased variance in subpopulation size and persistence and increased metapopulation persistence.