Biomass relationships during colony development in the desert leafcutter ant Acromyrmex versicolor

Leafcutter ants harvest leaves to grow a symbiotic fungus, which serves as the ants‘ direct food source. However, little is known about growth dynamics within leafcutter ant nests, which must be regulated at the level of the fungus as well as within the ant population itself. To characterize growth, we established laboratory colonies by collecting newly mated queens, and measured worker population sizes and fungus volume once a week for the first six months of colony development. In a second experiment, we quantified foraging rates and waste generation across a period of two months, in conjunction with measurements of fungus production, worker production, and larva and pupa numbers. Colonies grew exponentially during early development. During the same period, the relationship between standing fungal biomass and worker biomass scaled isometrically. Foraging rate and worker production were also positively correlated. Interestingly, the standing fungal biomass, but not worker biomass, predicted larval and pupal population sizes. These findings suggest the need for further studies of how nutritional and behavioral feedbacks between the ants and fungus shape colony development.