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Allee effects, invasion pinning, and species' borders Open Access


Author or creator
Keitt, T. H.
Lewis, M. A.
Holt, R. D.
Additional contributors
Species' Borders
Range Limits
Critical Phenomena
Allee Effects
Type of item
Journal Article (Published)
All species’ ranges are the result of successful past invasions. Thus, models of species’ invasions and their failure can provide insight into the formation of a species’ geographic range. Here, we study the properties of invasion models when a species cannot persist below a critical population density known as an “Allee threshold.” In both spatially continuous reaction-diffusion models and spatially discrete coupled ordinary-differential equation models, the Allee effect can cause an invasion to fail. In patchy landscapes (with dynamics described by the spatially discrete model), range limits caused by propagation failure (pinning) are stable over a wide range of parameters, whereas, in an uninterrupted habitat (with dynamics described by a spatially continuous model), the zero velocity solution is structurally unstable and thus unlikely to persist in nature. We derive conditions under which invasion waves are pinned in the discrete space model and discuss their implications for spatially complex dynamics, including critical phenomena, in ecological landscapes. Our results suggest caution when interpreting abrupt range limits as stemming either from competition between species or a hard environmental limit that cannot be crossed: under a wide range of plausible ecological conditions, species’ ranges may be limited by an Allee effect. Several example systems appear to fit our general model.
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© 2001 University of Chicago. This version of this article is open access and can be downloaded and shared. The original author(s) and source must be cited.
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Keitt, T. H., Lewis, M. A., & Holt, R. D. (2001). Allee effects, invasion pinning, and species' borders. The American naturalist, 157(2), 203-216. doi: 10.1086/318633.
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File title: Allee Effects, Invasion Pinning, and Species Borders.
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