Project Title: “The evolution of alarm pheromones and their associated behaviors in fungus-farming ants”
Mentor: Rachelle Adams – Evolution, Ecology, and Organismal Biology
Abstract:
Introduction/Background
Alarm communication is present in all living organisms. Alarm responses, like the ones we see in birds and mammals, are visual and auditory, but insects utilize a different approach: volatile organic compounds. Species-specific chemical signals aka alarm pheromones are suspected to have evolved from venom or from compounds released upon injury, but the selective pressures influencing their evolution remain unknown. Fungus-growing ants (FGAs: tribe attini) are an ideal system for studying alarm pheromone evolution because of the system’s different clades with varying castes, behaviors, colony size, and farming lifestyles. We expect that different genera of FGAs have evolved unique alarm pheromone makeup to suit their varying lifestyles.
Methods
We have compiled published data (~20 species FGAs) and used Gas-chromatography mass-spectrometry (GC-MS) to quantify novel data (~4 species) of suspected alarm pheromones from mandibular extracts. Additionally, we used the mandible-opening response (MOR) behavioral assay to quantify different responses from individual species when exposed to 1) colony-specific mandibular extracts, 2) solvent control, and 3) 3-octanol (a positive control).
Results
We found that higher attines (for example, leaf-cutting ants) are more responsive than passive lower attines. This behavior could stem from heightened aggression owing to larger colonies with specific ‘task forces’- typical of higher attines. Lastly, we used a mantel test to show that alarm chemical composition can be explained from an evolutionary context. Ours is the first study to relate chemistry, behavior, and natural history together to explain alarm communication evolution in attine ants.
If you have any questions, feel free to leave a comment, or reach out to me via my email: jennings.443@osu.edu.
If you want to check out our lab, you can look to our website (https://megalomyrmex.osu.edu/) or our instagram (@megalomyrmex)!
Wow, this is fascinating! I’m shocked to learn that this is the first time anyone has linked chemistry, behavior, and natural history in a system that seems to rich with all three. For your Figure 5, it looks like you have a lot of groups at certain points along the x axis. Could you explain why that is?
Hi Kyle, thank you for your interest in our project! In Figure 5, the groupings along the x-axis are clades- we calculated phylogenetic distance as distance from most recently shared common ancestor. I hope that clears things up!
Great job Alison! Really excited about your thesis project discerning the ant-fungus mutualism. Have you thought about what kind of methods you’d like to use to this?
Thank you, and I’m really excited about that too! For my thesis, I am planning on studying a potential driving force in the ant-fungus mutualism. I want to see if certain fungus-growing ants (species of Cyphomyrmex) can differentiate between different fungus gardens because of cultivar-specific volatile compounds. I’m planning on splitting up my thesis into two parts. In aim 1, I am going to isolate fungal cultivars from three species of Cyphomyrmex onto agar mediums. I plan on then using chemical instrumentation to assess what volatiles are found in these gardens, and if these volatiles are ant- or microbe-derived. In aim 2, I am going to conduct choice tests to see whether the ants are unbiased, or if they have true preference for their own fungal garden’s volatiles.