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.-- Ed Yong
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.