This, however, is precisely what researchers report in Science magazine.

It is all because of the Acacia's mutually beneficial relationship with a biting ant.

Together they fend off Africa's big grazing mammals; but it is these very antagonists that are needed to keep the plant-insect team working in concert.

"Simulating large mammal extinction, by experimentally excluding them from eating the trees, causes the ant-plant mutualism to break down," said co-author Robert Pringle from Stanford University, US.

The whistling thorn tree (Acacia drepanolobium) and the biting ant (Crematogaster) that lives on it form a relationship, evolved over many millennia, in which both species co-operate and in turn benefit from each other.