Scientists at the Smithsonian’s National Museum of Natural History have discovered a new genus and species of attine ants that reveals key clues in the mystery of ant agriculture evolution. A description of the new species, Cyatta abscondita, was published recently in the journal PLoS ONE.
Attine ants make up a group of more than 240 known ant species that pioneered agriculture well before humans and nearly all other organisms. They evolved more than 50 million years ago, growing elaborate fungal gardens in their nests to feed their colonies.
Ted Schultz, curator of ants at the museum, and Jeffrey Sosa-Calvo, graduate student at the University of Maryland and a Smithsonian pre-doctoral fellow, conducted an ancestral analysis of the new species using DNA. The new species is considered to be a “living fossil,” which can reveal ways in which early attine ants may have lived.
“Through our DNA analysis, we learned that the new species is very closely related to the first ant ancestor that began growing fungal gardens,” Sosa-Calvo explains. “Given this relationship, we can infer that some of C. abscondita’s unique physical and behavioral characteristics hint at what the first agricultural ants and their predecessors looked and acted like.”
C. abscondita, meaning “hidden ant” and informally named the “ghost ant” by its discoverers, was first recognized by members of the research team as a single misidentified specimen in 2003 in the collections of the Museum of Zoology at the University of Sao Paulo in Brazil.
Based on where the specimens had been collected, Schultz and Sosa-Calvo traced the location of the species to two separate, highly threatened, biomes in Brazil: Caatinga, an underexplored desert-like region populated widely by small thorny vegetation, and Cerrado, a tropical savanna region known among experts as a biodiversity hotspot. “After discovering such an informative species in Caatinga and Cerrado, we are very excited to return to these regions to learn more about this fascinating group of ants,” said Schultz.
The discovery of the new species entailed a multiyear excavation of intricate nests, delving down to a maximum of two meters beneath the surface. Ghost ants are nocturnal and forage for organic debris to grow their fungus gardens, which hang in curtain-like columns from the ceilings of their underground chambers. While the fungi that the ghost ants cultivate are probably not completely dependent upon their ant partners to survive and reproduce, the ants are dependent on the fungi for their survival.
The publication is the result of an international collaboration between research institutions in the U.S., Brazil and Germany.