POPULATION-DYNAMIC CONSEQUENCES OF COMPETITION WITHIN AND BETWEEN AGECLASSES

We investigate the population dynamics of a semivoltine species whose juvenile development takes two years to complete, and is followed by a very short reproductive adult stage. Reproduction is synchronized so at any given time the juvenile population consists of two cohorts. Coe xistence of the two cohorts requires that the strength of intra-cohort competition exceeds that of inter-cohort competition, an extension of the competitive exclusion principle. The population may exhibit popul ation cycles with low integer period. We identify two mechanisms for t wo-year cycles, and note that four-year cycles are a natural consequen ce of overcompensation. Three year cycles can occur and we discuss the mechanisms involved.