The impact of nectar-robbing ants on the pollination system of Asclepias curassavica.
Asclepias curassavica, a widespread annual herb in the American tropics and subtropics, is pollinated by the monarch and queen butterflies (Danaus plexippus and Danaus berenice) as well as a variety of other Lepidoptera, Hymenoptera and Diptera. However, ants frequently visit the flowers, reducing the amount of nectar available to the legitimate pollinators. Therefore, butterflies visit more flowers, spending less time on each flower with the result that the level of pollinia insertion drops. Nectar-robbing by ants therefore appears to be a maladaptive force resulting in reduced pollinator effectiveness for A. curassavica.