Fungus-growing ants (Tribe Attini) and their fungal cultivars share a 50-million-year coevolutionary history. Large scale phylogenetic analyses depict a strong co-phyletic signal among ants and their farmed fungi yet fungus sharing among unrelated ant lineages is somewhat widespread. An overview of sharing has been hampered by a lack of genetic markers that exhibit intraspecific variation and surveys across geographic regions. For example, previous studies have shown similar sequences of the internal transcribed spacer (ITS) region of fungus in different species of Trachymyrmex, suggesting that these ant species are farming the same fungal clone. To examine whether this was a case of symbiont sharing or an issue of relatively uninformative molecular markers, samples of fungus from colonies of Trachymyrmex arizonensis and Trachymyrmex pomonae were collected and sequenced from southeastern Arizona using traditional barcode markers (ITS) and genome-wide single nucleotide polymorphisms (SNPs). Since T. arizonensis has also been known to grow fungus from leafcutter ants in the Chiricahua Mountains in Arizona, surveys were conducted in this area to find other instances of this behavior; however, this was not observed. According to fungal ITS sequences of T. arizonensis and T. pomonae, the fungi of these species fall into the same large clade as other fungi associated with the Trachymyrmex genus. The SNP dataset, on the other hand, indicated that each species of ant grew its own subclade of ant fungi with only one colony (out of fourteen) of T. arizonensis growing a fungus that was otherwise associated with T. pomonae. As a result, there appears to be a pattern of codivergence between Trachymyrmex ant species and their fungal cultivars that may suggest the possibility of cryptic speciation for fungi that has not otherwise been detected with conventional markers, and fungal sharing across species may be less prevalent than previously suspected.
Date of publication
Dr. Jon Seal, Dr. Katrin Kellner, Dr. Joshua Banta, Dr. Matthew Greenwold
Master of Science
Beigel, Katherine, "A COPHYLOGENETIC ANALYSIS OF FUNGUS GARDENING ANTS AND THEIR SYMBIOTIC FUNGI" (2020). Biology Theses. Paper 65.