Context is everything: mapping Cyphomyrmex-derived compounds to the fungus-growing ant phylogeny
Ants communicate using a suite of chemicals with a level of sophistication that is inextricably linked to their ecological dominance. The fungus-growing ants have been the focus of chemical ecology studies for decades, especially the leaf-cutting ants. Some create long, conspicuous foraging trails to harvest fresh vegetation used to sustain large farming systems that feed millions of workers. However, of the ca. 250 fungus-growing ant species, most feed detritus rather than fresh material to their gardens, and colony sizes are tens to hundreds of workers. Colonies within the attine genus Cyphomyrmex use distinct methods of agriculture (i.e., yeast and lower fungus agriculture). We compared compounds found in five species from the yeast-growing Cyphomyrmex rimosus group (C. rimosus and C. salvini) and the lower agriculture Cyphomyrmex wheeleri group (C. costatus, C. longiscapus, C. muelleri). Compounds identified were compared with those reported in the literature and mapped onto the attine-ant phylogeny, and glands of origin suggested. There were 10 compounds across five species and two are known alarm compounds, 1-octen-3-o1 and 3-octanol. Of the six farnesenes detected, the most notable was the diversity of gaster-derived compounds in C. salvini and the high abundance of (3Z, 6E)-α-7-ethylhomofarnesene and α-6-bishomofarnesene in the three C. wheeleri group species. We also found 2,5-dimethyl-3-isoamylpyrazine in the heads of yeast-growing species, an unexpected result because pyrazines are known trail substances in other attines. Our results expand our understanding of semiochemicals found in fungus-growing ants and provides a starting point to generate hypotheses for more extensive comparative studies.
KeywordsCyphomyrmex Fungus-farming ants Alarm pheromone Trail pheromone Chemical communication Formicidae
We thank the staff and researchers at the Smithsonian Tropical Research Institute (STRI) for logistical support, and the Autoridad Nacional del Ambiente y el Mar for permission to sample and export ants. For assistance in the field, we thank participants of the 2015 and 2017 Tropical Behavioral Ecology and Evolution course, organized and financially supported by the University of Copenhagen (2015) and The Ohio State University (2017) in coordination with STRI. Funding for JZS was provided by a Postdoctoral Fellowship from the Smithsonian Institution Competitive Grants Program, and by a Marie Curie International Incoming Fellowship (327940 INSEAME). RMMA was supported by the University of Copenhagen (2015) and The Ohio State University (2017).
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Conflict of interest
The authors declare that they have no conflict of interest.
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