The Evolution and Maintenance of Mutualism Between Lycaenid Butterflies and Ants

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Dr. Naomi Pierce of Princeton University proposes an intriguing approach to quantifying various selection forces that drive the evolution of mutalisms in living organisms. This research will identify selective forces shaping the evolution of mutualism between lycaenid larvae and ants, and behavioral and biochemical mechanisms maintaining the association. The first part of the project will measure the benefits that ants (Iridomyremes anceps and I. rufoniger) receive from tending larvae of Jalmenus evagoras in terms of colony growth rate and investment into reproductive brood. It will also investigate the importance of individual variation in attractiveness to ants of larvae of J. evagoras that live in aggregations. The second part of the project will consider some of the causal mechanisms maintaining the association by first testing the oviposition behavior of females of J. evagoras on host plants that vary in their nitrogen content. The main emphasis of this side of the research, however, will be in using ant bioassays and biochemical analyses to learn more about the nature of the secretions of lycaenid larvae. Of particular interest will be identifying the chemical cues involved in species specific recognition between larvae and their attendant ants. To do this, Dr. Pierce will compare the secretions of each species in the genus that associates with a particular species of ant. She will also determine whether the amino acid profiles secreted by different species of Jalmenus reflect the dietary preferences of their attendant ants. And finally, she will examine whether the epidermal secretions of lycaenid larvae mimic in any way the surface secretions of the brood of their attendant ants. These studies should add significantly to our understanding of interdependent organism associations and to our perspective on general evolution.