Influence of Azteca alfari ants on the exploitation of Cecropia trees by a leaf-cutting ant

Abstract

The foraging activity of the leaf-cutting ant Atta laevigata in an early successional area near Manaus, Brazil, was monitored over a period of 18 mo. Four Cecropia species were growing in that area and all were associated with the ant Azteca alfari. Unoccupied trees (those in which there was no ant response to mechanical disturbance of the stem) were attacked by leaf-cutting ants more often than were trees occupied by A. alfari colonies. Cecropia ulei was the most frequently attacked species. However, leaves of C. ulei were the least preferred ones during assays in which detached leaves of the four Cecropia species were placed alongside the foraging trails of leaf-cutting ant colonies. C. ulei had the largest number of unoccupied trees compared to the other species. In addition, A. alfari colonies associated with C. ulei were smaller than those associated with C. distachya. These data suggest that A, alfari was influencing the selection of Cecropia species by A. laevigata, which harvested more from species that were less defended by the ants (with a higher proportion of unoccupied trees or trees hosting smaller ant colonies), although these were less preferred.