Implications of Differences Between Hermaphrodite and Female Flowers for Attractiveness To Pollinators and Seed Production

Echium vulgare is a gynodioecious species; hermaphrodite and female individuals occur in the same population. Flowers of the female individuals are smaller and produce less nectar. Female and hermaphrodite plants were equally frequently approached by bumblebees. After an approach the bumblebees visited more flowers on hermaphrodite plants. As a result, individual flowers on hermaphrodite plants received 50% more visits. In contrast, flowers on female plants produced more seeds, suggesting that the relation between seed set and number of visits was influenced by resource availability. Per visit bumblebees removed 16.5% of the pollen present in the anthers. In contrast to the common assertion in the literature, our data do not indicate that the number of bumblebee visits was limiting pollen transport to other plants in this situation.