Density Dependence as Related to Life History Strategy

Both theory and empirical information support the conclusion that most density—dependent change occurs at high population levels (close to the carrying capacity) for species with life history strategies typical of large mammals. The reverse is true for species with life history strategies typical of insects and some fishes. Theoretical considerations that give rise to these conclusions involve natural selection and trophic dynamics. There is a large body of literature that contains descriptions of density dependence as based on empirical observations. These data, and the models used to represent them, indicate that species with high reproductive rates, short life—spans and populations held below the limits of environmental resources exhibit most density—dependent change at low population levels. Similar data for species with low reproductive rates, long life—spans and populations that are more limited by resources (large mammals in particular) indicate that most density—dependent changes in vital rates occur at levels of the population quite close to the carrying capacity.