OHIO researchers discover oldest evidence of 'farming'

Jun 24, 2016

A fungus garden of Macrotermes natalensis. The freshly added substrate layer can be distinguished by its darker color.

Photo by Judith Korb

An international team of researchers, including two faculty members at Ohio University Heritage College of Osteopathic Medicine, has discovered the oldest fossil evidence of agriculture, not by humans, but by insects.

The team, led by Eric Roberts of James Cook University, discovered the oldest known example of fungus gardens within fossil termite nests from the East African Rift in 25 million year old geological deposits. The study was published June 22 in PLOS ONE.

Some termite species cultivate fungi in gardens in subterranean nests or chambers, helping to convert plant material into a more easily digestible food source for the termites.

Roberts said that scientists had previously used DNA from modern termites to estimate the origin of termite ‘fungus farming’ behavior back to at least 25 to 30 million years ago.

This has now been confirmed by trace fossil evidence from Tanzania, allowing researchers to more accurately characterize the timing and evolution of this symbiotic relationship, something thought to have significantly modified the environment.

"The origin of this behavior likely had a profound impact upon how nutrients were concentrated on the landscape, influencing the evolution of Africa's biota," said Professor Nancy Stevens of Ohio University's Heritage College. "Interestingly, the discovery of this behavior coincides with the late Oligocene climate optimum, before large-scale faunal shifts documented on the African landscape later in the Cenozoic."

Paul Filmer, program director in the National Science Foundation (NSF)’s Directorate for Geosciences, which funded the research, noted “Since some 90 percent of the wood in the dry environment studied is digested by termites, understanding the development of this symbiotic relationship is important to our knowledge of the history of carbon cycling in these forests."

Study co-author Duur Aanen, of Wageningen University in the Netherlands, said the transition to agriculture dramatically increased the range of possible habitats for both the fungus-growing termites and their domesticated fungi, in a process very similar to what happened tens of millions of years later, with humans and their domesticated crops and livestock.

Patrick O’Connor, professor of anatomy at the Heritage College, added, “This type of study emphasizes the need for integrating perspectives from the fossil record with modern approaches in comparative biology - it is a holistic approach to evolutionary biology and significantly informs our understanding of environmental change in deep time.”

While the cradle of termite agriculture presumably was in an African rainforest, the transition to fungiculture helped the termites to disperse to less hospitable dry savannas, and also to migrate out of Africa, into Asia.

Roberts added, “The phenomenon might have been triggered by the initial development of the Great Rift Valley in this part of eastern Africa, and the dramatic transformation of the landscape around this time.”

The study is part of an ongoing research project focused on the evolution of the Rukwa Rift Basin in Tanzania.  This project has produced an array of novel geological and paleontological discoveries in recent years.

Link  to paper:  http://dx.plos.org/10.1371/journal.pone.0156847

The study was funded by the US National Science Foundation-Directorate of Geosciences, the National Geographic Society (CRE), James Cook University, Ohio University, Portuguese Foundation for Science and Technology and a Marie Curie Fellowship.

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