With symbiotic partners, the means by which a host obtain a symbiont influence the specificity between the host and the symbiont. One such system where symbiont specificity is seen to varying degrees is with higher attine ants. Higher attine ants have symbiotic relationships with the fungal cultivar they grow and the bacterial symbionts in their microbiomes. Among the higher attines, there are two broad groups of fungi. Most ants in the genus Trachymyrmex tend to grow Clade–B fungi, which are a group of undescribed Leucocoprinus species, while leaf–cutting ants in the genera Acromyrmex and Atta tend to grow Clade–A fungi (Leucocoprinus gongylophorus). Previous work has shown switching the cultivar grown by Trachymyrmex ants, from Clade–B to Clade–A fungus, creates an unstable symbiosis between the ants and their grown cultivar, so that a sudden and catastrophic decrease in the size of their fungal garden invariably results. One hypothesis is that the stability of ant–fungal combinations is maintained by interactions among members of the microbiome of fungus–gardening ants and their fungus gardens. This thesis explored whether changing fungal partners impacts the microbiomes of the host ants and their symbiotic fungus by performing cross fostering experiments that forced ants to grow novel fungi. Specifically, these experiments forced ants of two Trachymyrmex species that normally grow Clade–B fungi to grow Clade–A fungi. The experiments revealed that Trachymyrmex ants altered their novel Clade–A garden microbiomes and that these were similar to that of the ‘control or sham switched’ Clade–B fungus gardens. These results suggest that ants play a role in determining the structure of the microbiome of their fungus gardens. Since these combinations are not stable, it is possible that the ‘novel’ microbiome structured by the Trachymyrmex ants is a factor in driving symbiotic collapse. Such findings suggest each fungal clade may have some specificity with a certain microbiome composition.

Date of publication

Summer 8-18-2022

Document Type




Persistent identifier


Committee members

Dr. Jon Seal, Dr. Katrin Kellner, Dr. Matthew Greenwold, Dr. Joshua Banta


Masters in Biology

Available for download on Saturday, August 17, 2024