Fitness consequences of cooperative colony founding in the desert leaf-cutter ant Acromyrmex versicolor

The evolution of cooperative colony foundation (pleometrosis)in ants hasbeen attributed to conversion of extra resourcesinto increased competitiveability. Most cooperative foundingspecies provide these additional resourcesfrom internal fatstores; however, in those species that forage for resources,theextent and type of individual investment in multiqueen coloniesis notwell understood. We compared singly- and group-foundedlaboratory colonies ofthe desert leaf-cutter ant Acromyrmexversicolor to investigate howcooperation affects colony survival,foraging success, and worker production.Under laboratory conditions,single foundresses were significantly less likelyto initiatea successful symbiotic fungus garden, which inevitably led tocolonystarvation and death. If gardens were initiated successfully,however,there was no difference in the growth trajectoriesand foraging patternsbetween colony types. Cooperation in thisspecies may more likely bemaintained by survival benefits thanby growth rate differences, which may beconstrained in groupsby individual and colony-level costs.