Individual Variation in Nectar Production and Its Effect on Fitness in Kalmia Latifolia

During summer 1986, we assessed the effect of individual variation in per flower nectar production rate on one component of plant reproductive success (percent fruit set) mediated through differential pollinator attractiveness. Thirty—two individual mountain laurels, Kalmia latifolia, were monitored for average 24—h nectar production in individual flowers, average per flower pollinator visitation rate, average floral density, and percent fruit set. Significant positive correlations occurred between (1) average 24—h nectar production by individual flowers and average visitation rate per flower, and (2) average visitation rate per flower and percent fruit set. Pollinators appeared to be differentially attracted to individual shrubs that produce larger quantities of nectar per flower, and the increase visitation rate promoted a higher percentage fruit set because K. latifolia is pollination limited. However, there was no correlation between an individual shrub's 24—h nectar production in 1986 and the same individual's 24—h nectar production in 1985. Thus, while pollinator behavior appears to influence this component of plant reproductive success in Kalmia, any selective advantage to individuals may vary between flowering seasons.