Azteca protection of Cecropia: ant occupation benefits juvenile trees.

In this 15 month investigation I experimentally demonstrated that sapling Cecropia aff. obtusifolia in lowland western Ecuador grow more vigorously when occupied by the ant Azteca constructor than when the ants have been removed. Thus the interaction is directly beneficial to Cecropia juveniles. The difference in growth is associated with differences in herbivory and vine cover. Removal of ants significantly increases nocturnal Coleoptera herbivory on unoccupied plants. In contrast to the influence on beetle numbers, Azteca are ineffective against Homoptera and cecidomyiid gall flies. Although ant-occupied saplings had less chewing herbivore damage throughout the study, the ants were more effective protectors in the dry season than in the rainy season, when herbivore pressure increased. In addition to reducing herbivory, Azteca efficiently remove vines from occupied saplings.