Ancient cliff-clinging flower and three species of ant

A lovely story from Ed Yong of multiple mutualisms involving a very rare, cliff-clinging plant that may live 300 years or more and three species of ants: "Ancient flower lives only on two Spanish cliffs, and uses ants to survive"

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This story begins with a cliff-hanger. On the Spanish side of the Pyrenees mountains, around 850 metres above sea level, two adjacent cliff faces hold the entire population of Borderea chouardii – one of the world's rarest plants. It's a small herb that grows into crevices in the rock. Its leaves are heart-shaped and its flowers green and unassuming. There are around 10,000 individuals here, all growing on a square kilometre of vertical rock.
Now, Maria Garcia form the Spanish National Research Council has discovered the plant's survival strategy, which involves three different species of ants. Through these multiple partnerships, B.chouardii quite literally clings to existence.
The plant is a relict, an ancient hanger-on from a time just after the death of the dinosaurs, when the Pyrenees enjoyed a tropical climate. It was discovered in 1952, and Garcia started studying it in 1993 by request of the Regional Government of Aragon, which is responsible for its management. Since then, she has regularly returned to the site by herself, and monitored all the accessible plants. "It's not easy fieldwork, I can tell you, but exciting and fun," she says.
Borderea plants are either ...