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4. The significance of r and K

As can be seen above, the two parameters of the Lotka-Volterra model determine how the population growth is controlled. The growth term, r, is typically the excess of fecundity (reproductive output) over mortality over the lifetime of an individual. High values of r imply high initial growth rate and, consequently, a rapid change in population growth rate as the carrying capacity is approached. Organisms with high values of r are successful in the initial colonization of a habitat, because the achieve their optimum population rapidly.

The value of K represents the number of organisms that a habitat can sustain. In established habitats, where the rate of population growth (characterised by high r) is less important, success is measured by carrying capacity, that is high value of K. These are very simplistic distinctions, but they have been used to contrast the ecological strategies of responsive species in dynamic habitats ('r-strategists') and dominant species in established habitats ('K-strategists').