Spatial spread of ecosystem engineers: The race is not always to the swift

Background/Question/Methods

We develop a simple model of the spatial spread of a species that is an ecosystem engineer.  The model assumes that the environment is described as a series of discrete patches laid out along one dimension.  We focus on the role played by the dispersal kernel for the engineer and by the spatial and temporal scale of the effect of engineering, in determining the rate of spatial spread.  In typical models of spatial pread, an organism that disperses farther, as measured by the mean square displacement of individuals, will always spread faster. 

Results/Conclusions

In contrast, in our model, the fastest spatial spread of the population occurs for an intermediate mean (squared) distance of spread.  We discuss how this result depends on the temporal and spatial scales that are an inherent part of the action of ecosystem engineers, and compare and contrast the work to simpler models for Allee effects.  Several specific examples, such as plants in the genus Spartina which accrete sediment are used to illustrate the application of our results.  We also demonstrate how the effect considered here would affect the design of control strategies for engineering species.