Population Differentiation in Acer platanoides L. at the Regional Scale-Laying the Basis for Effective Conservation of Its Genetic Resources in Austria

Norway maple (Acer platanoides L.) is a widespread forest tree species in Central and Northern Europe but with a scattered distribution. In the debate on climate change driven changes in species selection in the forest, Norway maple has recently received raised interest because of its comparatively high drought resistance (higher than in sycamore maple). Therefore, it is an interesting species for sites high in carbonates and where other native tree species have become devastated by pathogens (e.g., elm, ash). In Austria, the demand on saplings is currently rising, while there is only very little domestic reproductive material available (on average more than 95% of saplings are imported from neighboring countries). This study was undertaken to identify genetic diversity and population structure of Norway maple in Austria to lay the foundation for the establishment of respective in situ and ex situ conservation measures. In addition, samples from planted stands and imported reproductive material from other countries were included to study the anthropogenic influence on the species in managed forests. We used 11 novel microsatellites to genotype 756 samples from 27 putatively natural Austrian populations, and 186 samples derived from two planted stands and five lots of forest reproductive material; in addition, 106 samples from other European populations were also genotyped. Cross species amplification of the new markers was tested in 19 Acer species from around the world. Population clustering by STRUCTURE analysis revealed a distinct pattern of population structure in Austria and Europe, but overall moderate differentiation. Sibship analysis identifies several populations with severe founding effects, highlighting the need for proper selection of seed sources of sufficient genetic diversity in the species.