The influence of initial age structure on predator-prey interaction

Initial age structure influences the growth of a prey population and the outcome of the predator-prey interaction. In order to quantify that influence, we employed a simple numerical model using experimental data from the system Tetranychus urticae-Phytoseiulus persimilis. Four major points were drawn from the results: (1) A population created by young females grows much faster than a population created by the same number of females but distributed among the stable age structure. Final number of individuals after a few generations is then much higher than what a plant could support. Consequently, a stable age structure is probably never achieved under these conditions; (2) In the presence of a predator, such a population can persist for a sufficiently long time to overexploit its host plant and to produce enough individuals to allow dispersal; (3) The impact of the predator on the prey population is drastically different according to its own age structure at the beginning of the interaction; and (4) Predators disturb the prey age structure during the course of interactions and thus maintain the prey growth potential at a high level. These points constitute an important adaptation that determine the persistence of the prey and the predator at a metapopulation level. They bring a new insight on the adaptive characters of young female dispersal. (C) 1999 Published by Elsevier Science B.V. All rights reserved.