Predicting Plant Reproductive Success from Models of Competition for Pollination

Abstract

Models of reproduction in plants competing for pollination were constructed on the basis of mechanisms of interaction. I first developed an analytical model that predicts influences of interspecific pollen movement and pollinator visit rate on fruit set. When the only form of competition is loss of pollen due to interspecific pollen movement, the relative intensity of competition diminishes as pollinator visit rate increases. Stigmatic interference from foreign pollen can markedly change this relationship, and with certain modes of interference fruit set may even drop as pollinators become very abundant. Application of the model using field measurements indicated that interspecific pollen loss alone can account for the lowered fruit set of the understory herb Stellaria pubera when competing with Claytonia virginica. Movements and pollen carryover of the observed insect pollinators of S. pubera were simulated on a computer. The program then utilized the observed relationship between seed set and pollen receipt to predict seed production. The simulations suggested that the effect of interspecific pollen movement is greatly reduced when plants are grouped into single-species patches, and that seed production depends on pollinator movement patterns and pollen carryover.