Document: JEN-3-54-7

The role of ant nutrition in mediating a lycaenid-ant mutualism.

WEEKS, J.A.*

University of Arizona, Tucson, AZ 85721 ¹

Abstract:
Variability in the occurrence, strength, or outcome of mutualistic interactions has the potential to mediate both ecological and evolutionary processes within and among species. In this study, I examined the role of ant nutrition in mediating the context-dependent variability that occurs in the facultative mutualism between the lycaenid butterfly, Hemiargus isola, and one species of attendant ants, Crematogaster opuntiae. To establish that the response of foraging ants to lycaenid caterpillars is based on the nutritional needs of the colony, I quantified the response of foraging ants from colonies fed a high carbohydrate/low protein diet, a high protein/low carbohydrate diet, and a balanced carbohydrate and protein control diet to lycaenid caterpillars. Diet had a significant impact on the motivation of foraging ants to tend lycaenids. Significantly more ants from colonies fed a high protein/low carbohydrate diet tended lycaenids indicating that workers do forage based on the nutritional needs of the colony. Because the availability of carbohydrate resources changes dramatically during the months when several generations of lycaenids are completing development, these results suggest that there is a seasonal preference for H. isola that has the potential to impact population dynamics. In addition, the results indicate that there is variability in larval attractiveness. The response of foraging ants from a single colony to individual larvae differed significantly. Therefore, it appears that, in addition to ant nutrition, other factors influencing larval attractiveness contribute to the variability observed in this mutualism.

Keywords: mutualism, lycaenid, ants, conditionality, nutrition, Lycaenidae, Formicidae

This abstract is being presented at: 8:30 AM in session:
Oral Session #5: Mutualisms.