Dispersal of Miconia argentea seeds by the leaf-cutting ant Atta colombica

While leaf-cutter ants are thought to collect mainly vegetative plant material, they have also been observed collecting seeds or fruit parts on the forest floor (Alvarez-Buylla & Martı́nez-Ramos 1990, Kaspari 1996). For example, leafcutter ants have been observed carrying considerable numbers of Brosimum alicastrum Sw. and Cecropia spp. seeds into their nests (Wirth 1996) and Leal & Oliveira (1998; pers. comm.) found them foraging on the fruits and seeds of 19 different species of Brazilian cerrado vegetation, including six Miconia species. Under some circumstances, seed removal and relocation by leaf cutter ants might even be sufficient to affect local recruitment patterns of trees. For example, in Costa Rica, Atta cephalotes can remove all fallen fig fruit from beneath a Ficus hondurensis crown in a single night (Roberts & Heithaus 1986), while in Venezuela, seedling recruitment of the savanna tree Tapirira velutinifolia was positively associated with the seed harvesting and seed cleaning activities of the ant Atta laevigata (Farji Brenner & Silva 1996). Clearly leaf-cutter ants may be important seed predators and secondary dispersers of small seeded species in tropical forests, just as are litter ants (Byrne & Levey 1993, Horvitz & Schemske 1994, Kaspari 1993, Levey & Byrne 1993, Perry & Fleming 1980). Although non-foliar plant material, such as fruits, flower parts and fig stipules can represent c. 30% of the total annual biomass intake of an Atta colombica (Guerin) (Hymenoptera: Formicidae) leafcutter ant colony (and even up to 50% during the dry season)(Wirth et al.