Innate attraction supplants experience during host plant selection in an obligate plant-ant

In order to assess the relative contributions of innate attraction and environmentally-induced preference to nest plant selection by the obligate plant-ant Tetraponera aethiops, we submitted both mature and callow workers to paired choice tests using the leaves of four plant species, including their natural host plant Barteria fistulosa. Mature workers taken from nature as well as mature workers after 25 days of laboratory breeding (with or without contact with B. fifstulosa leaves) always showed a great preference for shelters made with the leaves of B. fistulosa. Similar results were obtained with callow workers isolated from any plant material during the first 25 days of imaginal (=adult) life or during pre-imaginal development. But those reared in contact with test-plant leaves for the same two periods showed significantly less preference for B. fistulosa than did the controls. As a result, experience gained during the larval and nymphal stages as well as during the first part of adult life (i.e. pre-imaginal as well as early learning) was demonstrated in T. aethiops, but in this situation of species-specific interaction it reinforces innate attraction as both larvae and adults live in contact with B. fistulosa in nature. These results are discussed in comparison with previous data collected on arboreal ants not specifically paired with a plant, for which an environmentally-induced preference can supplant innate attraction.