Maternal effects and the stability of population dynamics in noisy environments

1. It is widely appreciated that complex population dynamics are more likel y in systems where there is a lag in the density dependence. The transmissi on of maternal environmental conditions to offspring phenotype is a potenti al cause of such a lag. Maternal effects are increasingly found to be commo n in a wide range of organisms, and might thus be a frequent cause of noneq uilibrium population dynamics. 2. We show that a maternal effects' lag generally increases population vari ability This may result from the lag inducing cycles (or more complex dynam ics) in a deterministic environment or, in a stochastic environment, from t he lag interacting with environmental noise to produce more variable dynami cs than would otherwise occur. This may happen whether the underlying dynam ics are equilibrium, periodic or more complex. 3. Although maternal effects may generally destabilize dynamics there are a clear set of exceptions to this. For example, including a maternal lag may convert cycles to equilibrium dynamics, which may revert to cycles when ex ternal noise is added. 4. The influence of the maternal effect depends importantly on the details of the model, whether it is structured or unstructured, the life-history tr aits which are maternally affected, and the type of density dependence. 5. Our results indicate that, if maternal effects are possible, failure to include them in models used predictively may result in quantitatively, and perhaps qualitatively, poor predictions.