Monday, December 10, 2007
D0080

Phosphorus flow through colonies of the desert leafcutter ant Acromyrmex versicolor

Rebecca M. Clark, Kimberly Shaffer, kashaffe@asu.edu, and Jennifer H. Fewell, jfewell@asu.edu. Arizona State University, Social Insect Research Group, School of Life Sciences, Tempe, AZ

The emergence of the ant-fungus mutualism is a unique transition in ant trophic evolution, from a predatory lifestyle to mycophagy. Whereas trophic relationships between other ant species and their food have been shown to resemble those of other terrestrial insects, we do not fully understand how the evolution of the ant-fungus mutualism has affected trophic dynamics within leafcutter colonies. One method for understanding trophic dynamics involves comparing stoichiometric relationships (relative elemental composition) between organisms and their food sources. Along with carbon and nitrogen, elemental phosphorus (P) is a key element responsible for organismal growth, and it is found in much higher relative concentrations in insects compared to plants, requiring insects to employ a range of methods to effectively concentrate P. To determine if leafcutter fungus serves as an intermediary to concentrate the available P, we measured the relative P concentrations of: workers of the desert leafcutter ant Acromyrmex versicolor, the ants’ fungus, and leaves of one of the ants’ major food sources (Palo brea, a desert tree species). We found that ant relative P concentrations measured 0.64%, three times higher than leaf P concentration (0.19%), and also three times higher than fungus P concentration (0.21%). Thus, in contrast with expectations, the leafcutter ant fungus does not concentrate available P, and further research is needed to understand how leafcutter ants obtain adequate amounts of P.


Species 1: Hymenoptera Formicidae Acromyrmex versicolor