EVOLUTION OF MIXED MATURATION STRATEGIES IN SEMELPAROUS LIFE-HISTORIES - THE CRUCIAL ROLE OF DIMENSIONALITY OF FEEDBACK ENVIRONMENT

We study the evolution of age at maturity in a semelparous life histor y with two age classes. An individual may either breed in the first ye ar of its life and die, or delay breeding to the second year. In this setting a mixed strategy means that a fraction of the individual's off spring breed in the first possible breeding event, while the remaining fraction delay breeding. Current theory seems to imply that mixed str ategies are not evolutionarily stable strategies (ESSs) under a steady -state population dynamical regime. We show that a two-dimensional fee dback environment may allow the evolution of mixed age at maturity. Fu rthermore, different phenotypes need to perceive the environment diffe rently. The biological reasoning behind these conditions is different resource usage or predation pressure between two age classes. Thus, th e conventional explanations for the occurrence of mixed strategies in natural populations, environmental stochasticity or complex dynamics, are not needed.