Meeting Abstract

75.6  Tuesday, Jan. 6  Allometric scaling of whole colony metabolic rate in Pogonomyrmex californicus WATERS, James S.*; HOLBROOK, C. Tate; FEWELL, Jennifer H.; HARRISON, Jon F.; Arizona State University, Tempe; Arizona State University, Tempe; Arizona State University, Tempe; Arizona State University, Tempe james.waters@asu.edu

Across all the kingdoms of living organisms and a vast range of body sizes, an organism’s metabolic rate scales with mass by a power between 0.66 and 1, most often near 0.75. The mechanistic basis for the reduced mass-specific metabolic rate in larger animals remains controversial. The social efficiency hypothesis suggests that evolution of sociality may be facilitated by increased efficiency of task performance in larger groups, suggesting that metabolic rates might scale with mass to an exponent less than 1 in whole social groups, as occurs in individual organisms. We tested this possibility by investigating the scaling of metabolic rates of whole, functioning ant colonies. The metabolic rates of lab reared colonies of a monomorphic seed-harvester ant species, Pognonomyrmex californicus, were non-invasively measured with flow-through respirometry. Larger colonies expended less energy per ant than smaller colonies: whole colony metabolic rate scales with colony mass to the power of 0.75, suggesting that the colony is metabolically more like a "super-organism" than a collection of individuals. Investigating the mechanisms driving the scaling of metabolic rates in social groups such as ant colonies may reveal insight to the evolution of sociality as well as fundamental principles of scaling that also apply to organisms. This research was partially supported by a Sigma Xi Grant In Aid of Research and a NSF Graduate Research Fellowship to JSW and NSF IBN 0419704 to JFH.