Density-dependent vital rates and their population dynamic consequences

We explore a set of simple, nonlinear, two-stage models that allow us to co mpare the effects of density dependence on population dynamics among differ ent kinds of life cycles. We characterize the behavior of these models in t erms of their equilibria, bifurcations, and nonlinear dynamics, for a wide range of parameters. Our analyses lead to several generalizations about the effects of life history and density dependence on population dynamics. Amo ng these are: (1) iteroparous life histories are more likely to be stable t han semelparous life histories; (2) an increase in juvenile survivorship te nds to be stabilizing; (3) density-dependent adult survival cannot control population growth when reproductive output is high; (4) density-dependent r eproduction is more likely to cause chaotic dynamics than density dependenc e in other vital rates; and (5) changes in development rate have only small effects on bifurcation patterns.