Alpine peaks, cradles of an unsuspected floral diversity

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Discovering a new species of plant in Europe has become rare. On the summits of the Alps, however, three unknowns have just been identified. Three androsaces, discreet cushion plants that adorn the rocks and cracks of the high mountains. The androsace of Viso, the androsace of Dauphiné and the androsace of Saussure deploy their buds and their small white or pink flowers around a single root. Their hemispherical and dense shape offers exceptional thermal protection. They retain moisture and their own organic matter, which they recycle. And so can live for centuries.

The discovery of these new species is only the emerged part of the Vertical Ecology program, led since 2009 by the biologist Sébastien Lavergne (Laboratory of Alpine Ecology of Grenoble) and Cédric Dentant, botanist at the Ecrins National Park, astride the ‘Isère and the Hautes-Alpes. The two men have the singularity of combining science and mountaineering, which opened the way to inaccessible summits, ridges and peaks. An extreme environment that has remained terra incognita for the life sciences. “The high mountains are seen as a desert hostile to life. But by investing it with a floristic approach, we discovered an unsuspected biodiversity ”, says Cédric Dentant.

With their teams, they inventoried more than 300 high altitude plants, in the Ecrins and other massifs of the Alps, and carried out a vast program of genetic sequencing of all the plant species of the Alpine arc, i.e. some 4,500 taxa (or groups). The tallest plant observed, a saxifrage with opposite leaves, hung at 4,070 meters on the Barre des Ecrins – it currently holds the altitude record in Europe, at 4,500 meters. Beyond their inventory, these plants of the tops open a window on the evolutionary history of the alpine flora. With a major question: where did species take refuge during the great glaciations?

Shelters and species factory

For 2.4 million years, and until the end of the last ice age 10,000 years ago, fluctuations in ice ages and interglacials have shaped the emergence and distribution of species. According to the theory of the “nunataks”, an Inuit term for the mountain, certain peaks were able, thanks to their verticality and the power of solar radiation, to escape the ice, emerging like islets in a frozen ocean. They would then have served as a refuge for a procession of species, which then redeployed as the warming weather took place, seeding the surrounding mountains.

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