ABSTRACT
The dynamics of a size-structured population in which adult fertility correlates with body size, and in which adult body size at maturation is dependent (through competitive effects) upon population density during juvenile growth, are studied. A simple discrete model for a population with one juvenile size class and two adult size classes, one consisting of larger and more fertile individuals than the other, is derived and analyzed. The competitive effects on juvenile growth are separated into those due to competition from other juveniles and those due to adults. Parameter regions are determined in which the dynamics equilibrate, approach 2-cycles, or result in chaotic oscillations. The results suggest that intra-specific competition of this kind between juveniles and adults is destabilizing for either small or very large inherent net reproductive rates, strong competitive effects tending to result in a synchronous 2-cycle in which juveniles and adults avoid competition. For intermediate values of the inherent net reproductive rate, however, intra-specific competition has a stabilizing influence, promoting equilibration where there would otherwise be chaotic oscillations.
