Historical translocations of silver fir in peninsular Italy: Implications for managing the genetic diversity of plantations

Nowadays the use of forest reproductive material (FRM) is carefully regulated, but from the 18th century until few decades ago undocumented large-scale transfers of FRM has been commonly practiced in Europe. Past translocations could have had a profound impact on the genetic layout of European forests, and current plantations could either represent risks (e.g., genetic pollution for local lineages) or opportunities (e.g., unintentional assisted migration experiments in areas not covered by provenance trial networks) for extant forest genetic resources. Aiming at clarifying the role that silver fir plantations could play for the conservation of the genetic diversity of fragmented, rear-edge silver fir populations, we assembled a large genetic dataset of 3342 trees: 1553 from 48 plantations in Northern and Central Apennines, and 1789 from 38 natural populations representing possible sources of FRM. All trees were characterized with 16 microsatellite markers to reconstruct the main past translocations occurred in an area > 500 km wide in peninsular Italy. The integration of > 1000 newly genotyped individuals with previously published datasets enabled a broad review of the genetic structure of silver fir plantations across Italy. Overall, we found that ⁓30% of the planted individuals were translocated from a distant genetic cluster and 92% of nation-wide genetic diversity is conserved in plantations. The consequences of assessing the presence of local vs . non-local genotypes in plantations, as well as all downstream considerations about their spatial genetic structure and levels of genetic diversity, are discussed with a special focus on informing the management of forest tree plantations that could have high conservation value.