Response of fire ants (Formicidae: Solenopsis invicta and S.gerninata) to artificial nectars with amino acids

Abstract

Abstract. The role that amino acids in extrafloral nectars play in attracting ants to plants was investigated. Workers from laboratory colonies of Solenopsis invicta Buren and S.geminafa (F). (Formicidae) fed from artificial nectaries containing mimics of the extrafloral nectar of Passiflora menispermifoh and P.caerulea; P.menispermifoh nectar contains higher levels of amino acids (1347.3 pdml) than does the nectar of P.currulea (125.2 μm/ml). When sugar‐only and sugar—amino acid nectar mimics were presented simultaneously, more S.invicta workers were counted at sugar—amino acid nectar mimics than at sugar‐only nectars. S.geminatu did not discriminate between the two nectars. When the two Pamiflora L. nectar mimics were presented simultaneously, S.invicta and S.geminata workers were more abundant at the nectaries containing high levels of amino acids (P.menispermifolia HBK mimic) than at the nectaries containing low levels of amino acids (P.cuerulea L. mimic). The behaviour shown by S.invicta and S.gerninata suggests that plants with high levels of amino acids in their extrafloral nectars attract more ant protectors and might suffer less herbivory than plants producing nectars with low levels of amino acids. If so, ants may favour, over evolutionary time, plants that produce nectars with high levels of amino acids. Day‐to‐day variability in ant behaviour was considerable even among laboratory colonies maintained on the same diet in similar environmental conditions. This variability will reduce the selective impact that ants have on plants and may help to explain why most ant‐plant interactions are facultative.