Constant flower damage caused by a common stingless bee puts survival of a threatened buzz-pollinated species at risk

摘要

Illegitimate flower visitors may reduce the reproductive success of their host plants. Eriocnema fulva, a threatened Melastomataceae of the Atlantic Forest, Brazil, has pollen flowers with poricidal anthers that show frequent damage of floral parts. We identified the flower-damaging bees and determined their impact on fruit set. Bees of seven species visited their flowers, but only three species collected pollen by vibration. With only one visit to a flower patch per 12 h, the frequency of effective buzz pollinating bees was negligible, while flower-damaging workers of the stingless bee Trigona fulviventris (Apidae) accounted for 70% of the visits. During their lengthy visits, they cut anthers to access pollen, and often styles as well. We conclude that the direct negative consequence of flower damage by Trigona bees, as well as their indirect impact by making the flowers unattractive for effective pollinators is a major reason for the low fruit set (6.9%) of E. fulva. Considering the rareness of the plant species, these negative effects put the survival of E. fulva at risk.