Comparative Intraspecific Phylogeography of Alpine Plants

Research project P 13874 Comparative Intraspecific Phylogeography of Allpine Plants Harald NIKLFELD 11.10.1999 The Pleistocene ice ages have had a major impact on the biosphere. At the culmination of the last glaciation (Würm) about 18.000 years BP, nearly the entire Alps were covered with a continuous ice-shield. Only peripheral parts to the south and to the east remained unglaciated. Due to the tectonic structure of the Eastern Alps - a central part built up of silicates and peripheral limestone chaines to the north and to the south - the silicophile flora of the Eastern Alps does not exhibit a clear pattern of endemism reflecting Pleistocene refugial areas. Especially the occurrence of endemic taxa and of disjunct populations of rare species in the formerly most extensively glaciated central and highest parts of the Eastern Alps is not understood to date, although it had been a favorite object to biogeographers for many decades. The aim of this project is to investigate with molecular methods, where there have been refugial areas for eleven selected acidophilic taxa with contrasting distribution and ecology and to what extent these refugia contributed to the postglacial recolonization of the Alps. It can be expected, that due to the isolated and disjunct position of the presumed refugial areas, gene flow was restricted during the cold periods in the Pleistocene. Thus, evolutionary processes must have led to exclusive mutations and fixation of alleles/haplotypes in populations in the refugial areas as observed in several studies. This will allow to recognize these areas and to trace ancient remigration routes into the inner areas of the Alps. Whether some taxa, that nowadays are restricted to the most elevated parts of the Alps survived on nunataks (mountain peaks above the ice-shield) withstanding extreme conditions, or whether they recolonized these areas later, will be the second question asked in this project. If the investigated taxa have survived within the ice shield in disjunct populations more or less in situ, we expect a higher level of genetic diversity and the occurrence of exclusive haplotypes in the different nunatak-refugia. The comparison and interpretation of the 11 phylogeographic patterns gained will enable us to detect common patterns in the migration routes and the refugial areas. It will allow to estimate the influence of historical, ecological and geological factors on the distribution of the taxa. Two complementary molecular methods will be used to answer the above questions: AFLP-fingerprinting (Amplified Fragment Length Polymorphism) and PCR-based RFLP-fingerprinting of organellar DNA (Restriction Fragment Length Polymorphism). RFLP-analyses has already proved to be useful in detecting intraspecific genetic variation as caused by the ice-ages. But up to now very few molecular phylogeographic studies on alpine taxa have been carried out, most of them in Scandinavia, where in contrast to the situation in the Alps there is complete uncertainty about the location of refugial areas outside the ice shield what makes the interpretation of the results quite difficult. Subsidiary investigations on breeding system and cytology of the investigated taxa will complete the molecular investigations. The proposed investigation will be the first study dealing with the comparison of refugia and migration routes of different vascular plants using different molecular markers. A comparison of intraspecific phylogenies of widespread and of (sub)endemic taxa was never carried out this way before.

It is hard to imagine that less than 20,000 years ago the Alps were nearly completely covered by an ice sheet. Only some peripheral mountain ranges remained unglaciated. But was plant life possible in the Alps during these extreme periods? And if yes, where? In this project, we applied molecular methods such as Amplified Fragment Length Polymorphism (AFLP) fingerprinting on selected silicicolous alpine plant species to test the hypothesis that some siliceous areas at the eastern and southern border of the Alps acted as glacial refugia. We could demonstrate that genetic divergence caused by long-term isolation in these peripheral refugia is still detectable. In the central and thus most strongly glaciated parts of the Alps, mountain peaks (nunataks) protruded from the ice sheet. If higher plant life was possible on nunataks, has been discussed for more than a century. Our studies have shown that hardy plant species could survive on nunataks close to peripheral unglaciated areas. In contrast, the climatic conditions on nunataks in the central-most part of the Alps were too harsh even for the most hardy plants. However, we did not only rely on genetic data to trace ice age refugia. We also explored the distribution of narrow endemics, i.e. plants which have a very small distributional area and found good congruence with presumed glacial refugia. Our results thus suggest that refugia are characterised both by high endemism and by populations with special genetic features. These results are of high relevance for future research, e.g. in the field of global change research, as well as for a better and more efficient policy in nature conservation.