D3146: Learning behavior in fungus-gardening ants

All fungus-gardening ants (subfamily Myrmicinae, tribe Attini) tend gardens of fungal symbionts. In this obligate symbiosis, the ants provide their fungus with vegetative material which the fungus breaks down and consumes, and the fungus provides the ants with nourishment. A learning behavior called delayed rejection can be observed in the most highly derived fungus-gardeners, the leafcutting genera Atta and Acromyrmex: when a fungicide undetectable to the ants is added to forage material, the ants will collect the adulterated forage normally at first, but after a period of time abruptly cease collection of that forage type. To investigate this learning behavior across the fungus-gardening ant phylogeny, we measured colony learning rate of delayed rejection in five species of fungus-gardening ants from basal taxa, higher non-leaf-cutting taxa, and leaf-cutting taxa. Since more derived taxa and more basal taxa exhibit differences in caste specialization, brain size, and colony size, we expect more derived taxa and more basal taxa will also exhibit different colony learning rates.