INSTYTUT DENDROLOGII

Geographic variation of Alnus incana (L.) Moench within its natural range

Research on 22 populations of Alnus incana (Grey Alder) within its natural range of distribution enabled verification of a hypothesis about morphological and genetic differences between populations. Of particular interest is to compare Alpine and Carpathian populations as well as Carpathian and boreal populations. As a result of isolation during climatic changes in the Pleistocene, differences between Central European populations could develop.
The variation detected by biometric analysis indicates that only Scandinavian populations are distinct. An exception is the Finnish population FIN_1, representing the south of Finland, which is somewhat similar to the Central European group. Populations from the Alps and Carpathians do not differ as much as expected. The only Balkan population studied, although geographically distant, is similar to Carpathian populations. They also proved to be morphologically and genetically close to Masurian populations (NE Poland). A. incana from the Eastern Carpathians does not form any distinguishable group and is intermediate between populations from Masuria and the Alps. Only two populations from the Bieszczady Mountains (eastern Polish Carpathians, SE Poland) are slightly different. This suggests that they may originate from another Pleistocene refugium. Alpine populations differ quite strongly from one another but all of them are within the Central-South European group. The variation between Alpine populations, visible on the dendrogram, results from the distinct postglacial history of that region. It is clearly noticeable also in other tree species.
Results of this study do not confirm the hypothesis that differences between Carpathian, Sudeten and Alpine populations are significant. This may indicate that during the glacial periods the gene exchange was continued, as these regions were not sufficiently isolated. The geographic variation of this species along the axis Balkans-Scandinavia is easily noticeable. On the basis of this study it is debatable whether A. incana has migrated from montane refugia northwards, along Central European rivers, mostly the Vistula and Oder. It can be noticed, anyway, that Masurian and Sudeten populations are very similar to one another and to Eastern Carpathian populations. In contrast, populations from the Bieszczady Mountains (SE Poland) and Masuria (NE Poland) differ considerably and do not seem to be of common origin.