POLLINATOR VISITATION PATTERNS, FLORAL REWARDS AND THE PROBABILITY OFTRANSMISSION OF MICROBOTRYUM-VIOLACEUM, A VENEREAL-DISEASE OF PLANTS

1 We investigated patterns of pollinator visitation to plants of the w hite campion, Silene alba, and related these to floral nectar rewards in healthy female and male plants and in plants diseased with the anth er smut disease Microbotryum violaceum (= Ustilago violacea). 2 Pollin ators preferred plants with large floral displays, and also preferred males to females and healthy to diseased plants. Male plants consisten tly produced nectar with higher sugar concentration, thereby offering higher quality floral rewards than either females or diseased plants. 3 Variation in nectar production was also found among individual plant s and different plant families, suggesting that more attractive plants may be predisposed to infection since pollinating insects also serve as vectors for this fungal disease. 4 Such patterns of pollinator pref erence could affect the dynamics of disease transmission within popula tions by influencing the probability that insect visitors make transit ions between diseased and healthy plants. This vector transmitted dise ase may therefore modify the course of selection on floral traits by i mparting a cost to pollinator attraction.