Temporal phenotypic heterogeneity as a substrate for selection.

The interaction of temporal phenotypic heterogeneity with a population level fitness function was explored through the use of a simple model. The model, based upon experimental data, assumes that the exploitation of pollinators, and seed-set within plant populations are dependent upon the frequency of a pink flower morph in populations composed of pink and white morphs. An increase in pink frequency is accompanied by an increase in seed-set for both morphs. The model also assumes that seed-set within a population is the same for pink and white individuals. In perennials and annuals with long-lived seeds, fluctuations in morph balance from one season to another may lead to reproductive pulses or drags, depending upon which morph was in excess. The reproductive differential which stems from different levels of pollinator service leads to an increase in pink frequency and an attendant fitness gain. The perennial habit and long-lived seeds provide a population with a memory which permits the current population image to compete with images of previous years. As a consequence, fitness gains may be achieved in the absence of interplant or interpopulation selection.