Flower Constancy: Definition, Cause, and Measurement

Abstract

A pollinator that restricts its visits to one flower type, even when other rewarding types are accessible, can be said to exhibit flower constancy. This usage distinguishes constancy from fixed preference or labile preference for the most rewarding flower type; I discuss a quantitative constancy index that is insensitive to preference changes. Because a constant visitor avoids flowers with acceptable rewards, the behavior is inefficient unless there are constraints such as an inability to learn quickly or to remember simultaneously how to deal with many flower types. If such constraints are the basis for constancy, it should be most pronounced when flowers in a mixture differ strongly in morphology or color. I observed bees foraging in outdoor flower arrays and found that constancy always increased with increasing differences among flower types; similar results can be gleaned from one other study. The available experimental evidence thus suggests that constancy reflects behavioral constraints.