Resistance or emigration: response of the high-alpine plant Eritrichium nanum (L.) Gaudin to the ice age within the Central Alps

Two main possibilities regarding glacial survival of the mountain nora of t he Alps during the Quaternary have been discussed: the tabula rasa and the nunatak hypotheses. Eritrichium nanum (L.) Gaudin (Boraginaceae) is a peren nial cushion plant, occurring at high elevations of the Central Alps and ha ving a preference for extreme habitats. It belongs to a group of high-alpin e plants, for which in situ glacial survival on nunataks is ecologically po ssible. By investigating 20 populations of E. nanum of potential nunatak an d peripheral refugial regions using amplified fragment length polymorphism, considerable genetic differences between populations from the Central Alps and populations from peripheral refugia were detected; hence, the latter p robably did not serve as potential sources for the re-colonization of the C entral Alps after glaciation. Genetic variation was hierarchically structur ed (AMOVA), and three genetically distinct regions could be identified in t he Central Alps. Two of these, the Penninic and Rhaetic Alps, correspond to nunatak regions proposed in the biogeographic literature. Populations from the Lepontic Alps formed a third genetic group. Genetic correlation (Mante l statistics) was highest within populations, with a modest decline among p opulations within specific nunatak regions and a negative correlation outsi de the genetic influence of specific nunatak regions. In situ glacial survi val in E. nanum could be a model for the Quaternary history of other alpine plants, especially those that also occur at high elevations and in similar habitats.