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Citation. Tilman, D. 1989. Discussion: Population dynamics and species interactions. Pages 89-100 in J. Roughgarden, R. M. May and S. A. Levin, Eds., Perspectives in Ecological Theory. Princeton University Press.   [1171  LTER]

Introduction. Ecology is the scientific discipline that attempts to determine the causes of patterns in the distribution, abundance, and dynamics of the earth's biota. The earth's ecosystems are complex. In any given habitat, there are tens to hundreds or even thousands of different species. These influence each other both through direct pairwise interactions and through indirect interactions mediated by intermediate species, processes, or substances (Levine 1976; Holt 1977; Vandemeer 1980; Schaffer 1981). Because it is impractical, if not impossible, to observe all the potential interactions among all species and processes, ecological research involves the simplifying assumption that much of the complexity of nature is either unimportant or can be subsumed within a few summary variables. Schaffer (1981, p. 383) defined such simplifications as the process of ecological abstraction: "Accordingly, when the empiricist fits data to equations describing the growth rates of particular species, he has, in a sense, 'abstracted' these species from a more complex matrix of interactions in which they are embedded. Nevertheless, because the species studied, as opposed to the variables in the abstracted equations, continue to interact with the remaining, unspecified components of the ecosystem, the parameter values obtained perforce reflect, in part, the species and interactions omitted from the model."

Keywords. ecology, population dynamics, species interactions

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