Asymmetries in population growth regulated by intraspecific competition: Empirical studies and model tests

The linearity assumption in the logistic model of population growth is violated for nearly all organisms. Two simple models, the θ-logistic and the θ-Ricker, are shown to account for asymmetric patterns of population growth for 27 species of Drosophila and for a variety of other organisms, where the data were derived from the literature. These models are developed so as to aid laboratory and field ecologists to anticipate the dynamics of various experimental organisms. Potential problems of data gathering and model applications for experimental ecologists and wild life management biologists are identified. Intraspecific asymmetries offer alternative explanations to the "habitat selection" model, and the "higher order interactions" or coalitions model, for interspecific competition.