Floral color change and insect pollination: A dynamic relationship

Flowers in a wide range of angiosperm taxa (at least 456 species in 253 genera and 78 families) undergo dramatic ontogenetic color changes that serve as signals to their insect pollinators. The changes affect a diversity of floral parts, involve all three major classes of floral pigments, and produce a broad spectrum of initial and final colors. A diverse array of insect pollinators (in at least 21 families in four orders) recognize and respond to floral color phases, visiting pre-change flowers preferentially, relative to their contribution to the total floral display. A variety of hypotheses have been proposed to explain the functional significance of floral retention and color change. Experimental results demonstrate that in some cases retention of older flowers on the plant results in increased visitation by pollinators from a distance, while at close range, color change directs visitors towards the rewarding and sexually viable younger flowers. The interaction does not require a long coevolutionary association: both native and exotic insect species discriminate between floral color phases on native and introduced plant species. This flexibility is based at least in part on learning by the insect, although innate color preferences may also be important.