It is amazing.”Jost believes his findings conflict with conventional thinking about the evolution of endemic plants. “The usual view is that endemism is cause by geographical isolation: the plants could grow elsewhere, but they cannot escape the confines of their single habitat That’s not true for these orchids,” he says “They have tiny, dust-like seeds that can spread easily. But the colonisations fail because they literally cannot grow anywhere else.”This might be good news for the survival of biodiversity if, as expected, the planet warms in the coming decades. Endangered plants may be better at seeking new territory than previously thought. But the question remains: if they are so picky about climate, will they find anywhere suitable to go?A widely respected and published botanical Indiana Jones, Jost is never happier than when clambering through the bone-chillingly cold, damp Andean valleys.

As he says, “The only way to discover the botanical secrets up there is to walk every ridge and valley.” Some parts are guarded by tenacious Shuar Indians, descendants of the Inca gold-hoarders. But most are empty, except for the occasional mountain tapir and bear. “There are mountain ridges here that no scientist has ever visited,” Jost says. But whether braving bears, frostbite or belligerent locals, he rejoices in following in the footsteps of his hero, the 19th-century English botanist Richard Spruce, who trekked through the Pastaza valley in the 1850s. “He discovered ferns and liverworts that nobody has seen since.”I met Jost in mid-December, just after he returned from his latest expedition.

He apartment was strewn with plant samples, and in his rooftop greenhouse he was ready to show off intricate orchid flowers from past expeditions, many of which had opened their petals under his tender care.”You have to know what you are looking for when you go orchid hunting,” he says. “The flowers are only a few millimetres across and usually hide under the leaves Often the plants are not in flower. If I spot what I think is a new species, I can often only be sure when I bring it back here to wait for the flower to appear.”The survival of these plants away from the cloud forests is precarious. Jost keeps the greenhouse air cool with an electric fan, which is dependent on the town’s fitful power supply, and a passive air conditioner that draws in air over permanently wet tiles He maintains humidity with an ingenious paperweight balance. When a packet of plant stalks on the balance becomes too dry, it loses weight and the balance shifts, switching on a humidifier in the bathroom below “It’s not perfect.