Jun Chen, Lili Li, Pascal Milesi, Gunnar Jansson, Mats Berlin, Bo Karlsson, Jelena Aleksic, Giovanni G Vendramin, Martin LascouxPlease use the format "First name initials family name" as in "Marie S. Curie, Niels H. D. Bohr, Albert Einstein, John R. R. Tolkien, Donna T. Strickland"
<p>Primeval forests are today exceedingly rare in Europe and transfer of forest reproductive material for afforestation and improvement have been very common, especially over the last two centuries. This can be a serious impediment when inferring past population movements in response to past climate changes such as the last glacial maximum (LGM), some 18,000 years ago. In the present study, we genotyped 1,672 individuals from three Picea species (*P. abies*, *P. obovata*, and *P. omorika*) at 1M SNPs using exome capture to infer the past demographic history of Norway spruce and estimate the amount of recent introduction used to establish the Norway spruce breeding program in Southern Sweden. Most of these trees belong to *P. abies* and originate from the base population of the Swedish breeding program. Others originate from populations across the natural ranges of the three species. Of the 1,499 individuals stemming from the breeding program, a large proportion corresponds to recent introductions. The split of *P. omorika* occurred 23 million years ago (mya), while the divergence between *P. obovata* and *P. abies* began 17.6 mya. Demographic inferences retrieved the same main clusters within *P. abies* than previous studies, i.e. a vast northern domain ranging from Norway to central Russia, where the species is progressively replaced by Siberian spruce (*P. obovata*) and two smaller domains, an Alpine domain, and a Carpathian one, but also revealed further subdivision and gene flow among clusters. The three main domains divergence was ancient (15 mya) and all three went through a bottleneck corresponding to the LGM. Approximately 17% of *P. abies* Nordic domain migrated from *P. obovata* ~103K years ago, when both species had much larger effective population sizes. Our analysis of genome-wide polymorphism data thus revealed the complex demographic history of *Picea* genus in Western Europe and highlighted the importance of material transfer in Swedish breeding program.</p>
Picea abies, demographic inferences, population transfer, forest management
