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For centuries many more Swiss stone pines were felled than regrew, mainly because humans used the fragrant wood in so many different ways. The stone pine is, however, much more important for people living in the central Alps as it is an integral part of high-altitude protection forests. It provides a habitat for specialized wildlife and forms an attractive landscape for recreation.
While stone-pine forests used to be overexploited, naturally regenerated stone pines today are encouraged and sometimes even planted. But which region should the young plants come from? Is the local stock original or do the stone pines originate from trees of non-local provenance planted in earlier times? Here the pattern of genetic relationships can yield valuable information.
Felix Gugerli, Head of the Group ‘Ecological Genetics’, has, together with his team, analyzed about 3000 trees from nearly 140 stone-pine stands. The pines’ genetic fingerprints indicate that the populations in eastern Switzerland are distinct from those in western Switzerland, i.e. they are not closely related. Felix suspects that the ancestors of these two groups of populations outlasted the last Ice Age in two separate refugia along the southern fringe of the Alps. Pollen finds and the remains of subfossil wood, seeds and pine-cones support this hypothesis. Why, though, can the eastern and western Swiss populations today still be genetically distinguished? Felix thinks: “After the last Ice Age, the genetically distinct Swiss stone pines migrated back into the Alps from their respective refugia. While they do seem to have been in contact with each other in the region of the Gotthard Massif, they did not intermix much because the habitat was too inhospitable for the stone pine. The mountain range thus seems to have acted as a kind of barrier to genetic exchange.” Such contact zones can be found in other places throughout the Alps, which suggests there were other such Ice-Age refugia as well.
The findings of this study are of practical relevance as they indicate that local seed should be used for planting because it is presumably adapted to the environment in which it occurs. Ongoing research should show to what extent this will also apply under future environmental conditions. (Reinhard Lässig, Diagonal 1/17)