University of South Carolina, South Carolina, United States
Background/Question/Methods
More widespread species tend to be more locally abundant, both for the population dynamics of a single species across a network of habitat patches (intraspecific) and for many species sampled at a single point in time (interspecific). These abundance-occupancy relationships are fairly well-supported in observational studies, but the underlying factors driving them are less clear. For instance, variation in demographic rates, dispersal, and spatial habitat network structure could all influence resulting abundance-occupancy relationships. We propose a simple simulation model to explore intraspecific and interspecific relationships. We create spatial habitat networks of variable size and dispersal connectivity, and simulate population dynamics across spatial networks by starting from entirely neutral communities, then systematically incorporating complexity in the form of (co)variation in species demographic rates and dispersal processes.
Results/Conclusions
We find that intraspecific abundance-occupancy relationships are quite weak and unaffected by the incorporation of demographic or dispersal rate variation or network structure. However, interspecific abundance-occupancy relationships were quite strong and sensitive to the spatial network structure and (co)variation in demographic and dispersal rates. This identifies a clear difference between the two forms of the relationship, as intraspecific abundance-occupancy relationships rely on temporal variation in environmental conditions independent of species trait variation, while interspecific abundance-occupancy relationships require species trait differences. Together, we provide a clear, spatially-explicit framework to explore the potential drivers of abundance-occupancy relationships, with potential extensions to many other macroecological relationships.
