Evolution of semelparous and iteroparous perennial plants:: Comparison between the density-independent and density-dependent dynamics

The evolution of the frequency of reproduction in perennial plants is analyzed using the Lefkovitch matrix model. The model describes a population dynamics with a stage-specific pattern of reproduction and mortality of plants. Both the density-independent and density-dependent models are analyzed, and the results of the two models are compared. In the density-independent model, the invasible condition depends on the survival rate at juvenile stage, the emergence rate of seeds and the trade-off curve between the number of seeds and the survival rate of mature plants. The result is qualitatively similar to the studies by Schaffer & Gadgil (1975, in:Ecology and Evolution of Communities.Cambridge, MA: Belknap Press.) and Pianka (1976,Am. Zool.16,775–784). However, in the density-dependent model, the invasible condition does not depend on those parameters, but on only the trade-off curve. Therefore, the trade-off between the number of seeds and the adult survival rate, and the density-dependence of the dynamics, play an important role in the evolution of the frequency of reproduction. However, there is no significant difference between the results derived from the stage- and the age-structured population models.