The effects of genotype, caste, and age on foraging performance in leaf-cutting ants

The evolution of polyandry is a general problem in behavioral ecology that has attracted particular interest in the social insects. Most social insects are monandrous (i.e., females are inseminated by a single male), but approximately a third of species have evolved polyandry (i.e., females are inseminated by multiple males), which can reach extreme levels. One of the leading explanations for polyandry is that genetically diverse colonies may have improved division of labor because of genotypic variation in the propensity of workers to engage in particular tasks. Here we investigate whether there may also be genotypic variation in the ability to carry out a task, by examining the effect of genotype, as well as caste and age, on the foraging performance of workers of the leaf-cutting ant Acromyrmex subterraneus. Larger ants cut larger fragments of orange-impregnated parafilm, and did so more quickly than smaller ants, whereas older ants also cut larger fragments but were slower to transport them. Most importantly, we found that patrilines within colonies differed significantly in the size of fragment cut, and the speed of cutting and transporting fragments when controlling for both ant size and fragment size in the analyses. Certain patrilines were better foragers, often in multiple ways, whereas other patrilines were significantly worse at foraging. Genotype can therefore affect the ability of social insect workers to carry out tasks as well as their previously shown propensity to engage in them, providing an additional mechanism by which genetic diversity may be beneficial to social insect colonies.