INSECTÐSYMBIONT INTERACTIONS Presence of Multiparasite Infections Within Individual Colonies of Leaf-Cutter Ants

HostÐparasite dynamics can be altered when a host is infected by multiple parasite genotypes. The different strains of parasite are expected to compete for the limited host resources, potentially affecting the survival and reproduction of the host as well as the infecting parasites. Fungus-growing ants, including the well-known leaf-cutters, are an emerging model system for studying the evolution and ecology of symbiosis and host-parasite dynamics.We examinewhether the fungus gardens of leaf-cutter ants can be simultaneously infected by multiple strains of the fungal pathogen Escovopsis. Intensive sampling of Escovopsiswas conducted from individual gardens, as well as betweendifferent garden chamberswithin individual colonies of leaf-cutting ants. Isolates obtained were genotyped by DNA sequencing.We found that, minimally, 67% of the individual colonies of the leaf-cutter ant genera Atta and Acromyrmex and 50% of the At. colombica garden chambers studied were simultaneously infected bymultiple distinctEscovopsis strains. Experimental challenges showed that different Escovopsis strains do not exhibit obvious antagonism toward each other, suggesting that coinfecting strains of the parasite do not engage in interference competition, although interactions were not studied at the cellular level. Further research is needed to understand interparasite interactionsbetweencoinfectingEscovopsis strains and tounderstand the impactofmultiparasite infections on the survival of leaf-cutter ant gardens.