Meeting Abstract
Queens of the harvester ant Pogonomrymex californicus have been documented as having two distinct behavioral phenotypes controlling both aggression and the tendency to form foundress associations. Pleometrotic queens found colonies cooperatively with nest-mates while haplometrotic queens found solitary nests. Haplometrotic queens are larger and more aggressive to other queens, and produce eggs at a higher rate during colony founding. We tested for possible metabolic differences between these types, predicting that the non-aggressive pleometrotic queens would have lower metabolic rates, and that pairs of pleometrotic queens would have even lower rates (per ant) as prior studies have shown reduced work and per capita egg production in pairs relative to solitary founders. CO2 emission and O2 consumption was measured using a stop-flow respirometry system. We tested individual haplo- and pleometrotic individuals and pairs of pleometrotic queens. Respiratory quotients averaged .68 and did not differ among treatments, suggesting that these queens were primarily metabolizing lipids. Indeed, our results showed that the paired pleometrotic queens had a significantly lower metabolic rate (.0066 mlCO2/hour⋅animal) than the individual pleometrotic queens (.0077 mlCO2/hour⋅animal), while haplometrotic queens had the highest metabolic rate of the three groups (.009 mlCO2/hour⋅animal), suggesting that the aggressivity and high egg-laying rates of the haplometrotic queens has a measurable and significant cost, and that cooperative founding reduces per capita energy use. These differences in energy use may partially explain differences in survival of queens, as queens do not forage during the prolonged period of colony founding. This research was partially supported by NSF IOS 1122157 and NSF DMS 1313312.
