The extent of historic translocation of Norway spruce forest reproductive material in Europe

Key message Norway spruce seed has been traded extensively for at least three centuries throughout the natural distribution range in Europe and beyond. However, our knowledge about these transfers is limited. Historic data are essential tools to trace back human-mediated gene flow and for interpretation of recent genetic studies. Context Human-mediated gene flow can potentially have a major impact on the genetic composition of forest tree populations, yet our knowledge about seed sources used within the current species' range is still limited. Norway spruce is one of the most important coniferous species in European forestry, and data drawing conclusions about the genetic composition of current populations are vital with regard to gene conservation and sustainable forest management. Because molecular data are not available on a more detailed scale, historic records provide crucial information about translocations. Aims Our aim is to provide the first pan-European review on Norway spruce translocations from the seventeenth until the twentieth century. Methods We analysed historic and recent literature compiling information on the cultivation and transfer of Norway spruce reproductive material. Historic records are compared with recent molecular studies. Results Seed exchanges have profoundly altered the native genetic population structure of Norway spruce. Especially, Central European seeds have been used throughout and beyond the natural distribution area. Figures illustrating the historic plantings in Europe are provided. Conclusion Recent molecular data reveal persisting effects of past translocations. Historical records can be extremely useful for providing information about autochthony and thus guide gene conservation strategies and explain the performance of extant populations.