Ant genotype, but not genotype of cultivated fungi, predicts queen acceptance in the asexual fungus-farming ant Mycocepurus smithii (Hymenoptera: Formicidae)

Nestmate acceptance in ants can depend on environmental factors (e.g., odors acquired from environment) or on ant genotype. Here, we test whether queen acceptance by workers of the fungus-farming ant Mycocepurus smithii can be predicted from the fungal genotypes of fungus gardens and from the ant genotypes of interacting workers and queens. Mycocepurus smithii is a clonal (asexual) ant with multi-queen colonies that cultivate clonal fungi. Ant colonies can be switched to new fungi to raise queens in experimental cross-fostered ant-fungus combinations, and ant-genetic factors versus fungus-derived factors modulating worker-queen interactions can therefore be tested in controlled experiments. In a factorial experiment using all six combinations of three ant clones and two distantly related fungal clones, we performed 180 blind observation trials in which we introduced queens to queenless mesocosms (workers and garden) and scored worker aggression toward the introduced queens. We found that aggression toward queens is correlated with ant genotype, and that odor cues that ants may have acquired from their native fungal cultivar do not override the cues correlated with ant genotype during queen acceptance by workers. The acceptance of queens of M. smithii is based therefore less on fungal odor cues and more on cues correlated with ant genetics. Because hundreds of queens can be raised in laboratory nests of M. smithii, future research can use the queen-adoption protocol developed here to test whether the ant-genetic factors mediating queen acceptance could perhaps be important in kin recognition in M. smithii.