Three New Species of Fungus-Farming Ants Discovered in South America

Three new species of the ant genus Sericomyrmex have been discovered in Brazil, Venezuela, Colombia, Ecuador and Peru.

Sericomyrmex radioheadi, worker. Image credit: A. Ješovnik T.R. Schultz, doi: 10.3897/zookeys.670.11839.

The genus Sericomyrmex belongs to the fungus-farming ants (tribe Attini), a New World group of over 250 species, all of which cultivate fungus gardens for food. These ants provide the fungus with the substrate on which it grows, either organic detritus or fresh vegetation, thus effectively practicing agriculture.

Like the majority of attine-ant genera, Sericomyrmex has a wide Neotropical distribution, ranging from Mexico southward to Bolivia, Paraguay, and Paraná, Brazil.

Sericomyrmex species can be found in a variety of habitats, from dry savanna to tropical wet forest, as well as in disturbed, open, and urban habitats.

In an attempt to revise and improve the taxonomy of this genus, Smithsonian Institution’s Ant Lab researchers Ana Ješovnik and Ted R. Schultz collected and studied Sericomyrmex ants from across their entire range in Central and South America.

As a result, they discovered three new species: Sericomyrmex maravalhas in Brazil, S. radioheadi in Venezuela, and S. saramama in Colombia, Ecuador and Peru.

“One of those species, Sericomyrmex radioheadi, collected in the Venezuelan Amazon, was named after the British music band Radiohead,” the researchers said.

“We wanted to honor their music. But more importantly, we wanted to acknowledge the conservation efforts of the band members, especially in raising climate-change awareness,” Dr. Ješovnik explained.

The team also found that the bodies of Sericomyrmex ants are covered with a white, crystal-like layer.

“Curiously, this previously unknown layer is present in female ants (workers and queens), but is entirely absent in males. Both the chemical composition and the function of this layer are unclear,” the scientists said.

“One possibility is that the layer is microbial in origin and that it has a role in protecting the ants and their gardens from parasites.”

“This is interesting, because most of the fungus-farming ants cultivate antibiotic-producing bacteria on their bodies to protect their gardens from microbial weeds.”

“In Sericomyrmex, these bacteria are absent, yet their gardens are also parasite-free.”

Figuring out if this crystal-like layer has a role in protecting these ants’ fungus gardens might provide clues for managing diseases in human agriculture and medicine.

“At only 4 million years, Sericomyrmex is an evolutionary youngster, the most recently evolved genus of fungus-farming ants, and an example of rapid radiation — comparable to other fast-evolving groups, such as the freshwater fishes in Africa, or the Hawaiian fruit flies,” the researchers said.

“Rapid radiation is a process in which organisms diversify quickly into a multitude of forms, making these ants good candidates for studies into speciation and evolution.”

The paper describing the new Sericomyrmex species was published in the journal ZooKeys.

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A. Ješovnik T.R. Schultz. 2017. Revision of the fungus-farming ant genus Sericomyrmex Mayr (Hymenoptera, Formicidae, Myrmicinae). ZooKeys 670: 1-109; doi: 10.3897/zookeys.670.11839