Individual Variation and Population Dynamics

Abstract

A lot of classical ecological theory is based on the postulate that populations consist of identical individuals (Kingsland 1985, McIntosh 1991). Even though modeling something as complex as ecological systems necessitates some simplifications, this seems at odds with the fact that natural and laboratory populations typically exhibit large amounts of both genetic and non-genetic variation in life-history traits and demographic parameters. During the last decade, much interest in the population effects of individual variation has arisen (e.g., Sibly and Smith 1985, Lomnicki 1988, Chesson 1991, DeAngelis and Gross 1992). One theme in these studies is that individual variation promotes stable dynamics (e.g., Begon 1984, Lomnicki 1988). This conclusion of variability enhancing stability is weakened by the inherent complexity of the two-dimensional consumer-resources models employed. It is not easy to generalize the results to other forms of individual variation or other systems. In this paper we design models that are analogous to the standard deterministic one-species models commonly used, but which include individual variation. We use the models to investigate the possibility of making generalizations about the role of individual variation in population dynamics.