A direct measure of pollinator effectiveness.

A direct measure of pollinator effectiveness, relying on seed set, is proposed, where: [Formula: see text] P i =mean number of seeds set/flower by a plant population receiving a single visit from species i Z=mean number of seeds set/flower by a population receiving no visitation.U=mean number of seeds set/flower by a population receiving unrestrained visitation.The utility and limitations of the proposed measure are discussed and exemplified with a population of Ipomoea trichocarpa (Convoculaceae).