In the upland forests of Vanua Levu and Taveuni in Fiji, a remarkable and largely unknown form of agriculture has been unfolding for millions of years, long before humans planted their first crops.
Tiny ants, no bigger than a grain of rice, have been cultivating plants in a sophisticated system that mirrors human farming in striking ways.
For Doctor of Philosophy (PhD) candidate Umar Diarra at The University of the South Pacific, learning about the depth of this ancient partnership was life-changing.
“I have always been drawn to research,” he says.
“There is something deeply satisfying about asking a question that nobody has answered before. But when I learned that ants in Fiji are among the only non-human animals known to cultivate plants, I knew I had to be part of uncovering that story.”
At the centre of Umar’s research is a fundamental ecological question: why do some partnerships in nature survive while others collapse?
“In nature, we see relationships everywhere between plants and pollinators, animals and microbes,” Umar explains.
“But while some of these partnerships persist for millions of years, others break down very quickly. We still don’t fully understand why.”
To explore this, Umar studies a unique group of ant-associated plants in the coffee family, known as Squamellaria. Fiji offers a rare and powerful research setting, where different types of these relationships exist side by side.
“Fiji is effectively a natural laboratory,” Umar says.
“We have both facultative and obligate partnerships occurring in the same forests. That allows us to directly compare how these systems function and respond to change.”
Among these plants, the most extraordinary are the obligate Squamellaria species – six plants found nowhere else on Earth. These species exist in a tightly interdependent relationship with a single ant species, Philidris nagasau. Together, they form what scientists consider the only known example of plant cultivation by a non-human animal.
“The ants plant the seeds, care for the plants as they grow, and fertilise them using their own waste,” Umar explains.
“In return, the plant provides shelter and food. Neither can survive without the other.”
Unlike most ants, Philidris nagasau cannot exist independently.
“These ants don’t just live in the plants, they depend on them completely,” Umar says.
“They expand their colonies by farming new plants. It’s agriculture in every sense of the word.”
Umar’s research goes beyond this extraordinary partnership to investigate how the ants maintain the health of their crops.
“What fascinated me is that they don’t just farm, they manage their crops,” he says. “They behave like farmers.”
Through detailed field observations, Umar has documented the ants performing behaviours remarkably similar to human agriculture.
“I’ve observed them actively removing unwanted material from the plants,” he explains.
“Essentially, they are weeding removing potential pathogens before they can harm the plant.”
But the most surprising discovery lies hidden inside the plants themselves.
Inside the waste chambers of these ant-farmed plants, Umar has identified diverse microbial communities, including previously unknown bacteria with potentially powerful properties.
“One of my most important findings is the discovery of antibiotic-producing bacteria living inside these plants,” he says.
“Many of these bacteria appear to be new to science.”
These microbes may play a crucial role in protecting the plant from disease.
“The bacteria are likely producing antibiotics that suppress harmful pathogens,” Umar explains. “It’s a natural disease management system that has evolved over millions of years.”
Beyond its ecological importance, this discovery could have far-reaching real-world applications.
“This opens exciting possibilities for agriculture and medicine,” he adds. “We may be looking at entirely new sources of natural antibiotics.”
Despite its global scientific significance, this delicate system is under growing threat.
Over three years of fieldwork, Umar has observed the spread of an invasive species, the white-footed ant (Technomyrmex vitiensis) into these forests.
“What I’ve seen is deeply concerning,” he says. “These invasive ants are displacing the farming ants at an alarming rate.”
The consequences are severe and immediate.
“When Philidris nagasau disappears, the plants lose everything seed dispersal, fertilisation, and protection,” Umar explains. “And without those services, they die.”
Because these ant-plant systems exist only in limited areas of Fiji, their vulnerability is especially high.
“We are at risk of losing an entire evolutionary system found nowhere else on Earth,” he warns.
Umar emphasises that this is not just a biological issue it is closely tied to human activity.
“The spread of invasive ants is strongly linked to forest disturbance,” he notes. “Protecting these species means thinking carefully about how we use and manage our land.”
Beyond contributing to ecological understanding, Umar hopes his research will spark greater national awareness and pride in Fiji’s natural heritage.
At the same time, the research points toward practical solutions and future innovations.
“Some of the bacteria we’ve found have plant growth-promoting properties,” Umar explains. “There is real potential here for sustainable agriculture.”
But perhaps most importantly, Umar hopes his work will inspire others.
“I hope this research encourages the next generation of Fijian scientists to look closely at what’s around them,” he says. “Some of the biggest questions in biology may already have their answers right here at home.”
In the quiet canopy of Fiji’s forests, these ants continue their ancient practice planting, tending, and protecting their crops with a precision that rivals human agriculture.
For Umar Diarra, the journey is far from over.
“There is still so much we don’t know,” he says.
“And that’s what makes it exciting. Every time we step into the forest, there’s a chance to discover something entirely new.”
Two young Squamellaria imberbis growing on host tree.
Dissected domatium of Squamellaria imberbis with Philidris nagasau visible.
A farming ant (Philidris nagasau) viewed under a microscope.
A magnified view of a farming ant under a microscope.
