PARENT SESSION
Monday, August 7, 8:00-11:30 am
COS 15 - Ecological modeling I: populations, communities, and ecosystems
L-5, L-6, L-7, Lobby Level, Cook Convention Center
Presiders: S Railback and M Calef
Ecosystem engineers: runaway growth and multiple basins of attraction.
Cuddington, Kim*,1, Wilson, Will2, Hastings, Alan3, 1 Ohio University, Athens, OH2 Duke University, Durham, NC3 University of California - Davis, Davis, CA
ABSTRACT- All species modify their abiotic environment to some extent: ecosystem engineers are species where the magnitude of modification is sufficiently large that it needs to be accounted for in making predictions about population, community or ecosystem dynamics. We present a simple, general model of ecosystem engineers which assumes that there is direct feedback between the abiotic state and the engineer population. We relate our findings to invasive species that have large environmental impacts. There is little data which describes the functions that relate population density of engineers to abiotic environmental changes. Therefore, we present an analysis of four plausible functions for this relationship (linear, saturating, sigmoid and peaked). The effect of the engineer will depend on the characteristics of the environment. Highly resilient environments may return to their original state so quickly that engineering effects have no impact. In environments subject to significant modification, feedback that decreases density-dependence of the engineer population can allow species with Allee effects to persist at low density. Such modification can also lead to runaway growth of the engineer species, where the alteration of the abiotic environment is described by a linear function. For saturating relationships between environmental state and population density, engineers may reach a stable state with a population density much higher than that predicted by logistic growth. In some cases, multiple basins of attraction exist and perturbed populations can switch between stable equilibria and runaway growth.
Key words: ecosystem engineers, model, population ecology