| Abstract | dc.description.abstract | Models of ecological communities are traditionally based on relationships between pairs of species,
where the strengths of per capita interactions are fixed and independent of population abundance. A
growing body of literature, however, describes interactions whose strength is modified by the density of
either a third species or by one of the species involved in a pairwise interaction. These modified interactions
have been treated as indirect effects, and the terminology addressing them is diverse and
overlapping. In this paper, we develop a general analytical framework based on a qualitative analysis
of community structure to account for the consequence of modified interactions in complex ecological
communities. Modified interactions are found to create both direct and indirect effects between species.
The sign of a direct effect can change in some instances depending on the magnitude of a key variable
or parameter, which leads to a threshold change in system structure and dynamics. By considering
alternative structures of a community, we extend our ability to model perturbations that move the
system far from a previous equilibrium. Using specific examples, we reinterpret existing results, develop
hypotheses to guide experiments or management interventions, and explore the role of modified interactions
and positive feedback in creating and maintaining alternative stable states. Through a qualitative
analysis of community structure, system feedback is demonstrated as being key in understanding
and predicting the dynamics of complex ecological communities. | en_US |
