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Key message: Pinus nigraJ.F. Arnold has an ecological and economic interest in Europe, but many of the planted populations have an unknown origin and infraspecific taxonomy. Six PortugueseP. nigrapopulations characterised with microsatellites revealed high intra-population diversity structured into two clusters with low differentiation that might suggest two provenances or infraspecific taxa. Despite compared with foreign samples from different subspecies, we were not able to infer about the origin or infraspecific taxonomy of the Portuguese populations based on the pooled microsatellite data. Context: Many of the European Pinus nigra J.F. Arnold forests were planted with the material of unknown origin. Efforts have been made to determine their provenances and infraspecific taxonomy regarding their relevance for defining strategies of genetic resources conservation, germplasm use, forest management and genetic improvement. The Portuguese P. nigra populations are allochthonous, and their provenance and infraspecific taxonomy are unknown. Aims: With this work, we intended to characterise the Portuguese P. nigra populations regarding its genetic diversity, structure and relationships using simple sequence repeat (SSR) markers and/or to infer about its origin and infraspecific taxonomy by comparing the SSR patterns of foreign P. nigra samples of known taxonomic classification. Methods: A total of 224 Portuguese P. nigra individuals from six populations were characterised using 14 SSR markers developed specifically to different Pinus sp., including P. nigra, by other authors. Results: Thirteen SSR loci were selected and showed 100% of polymorphism among individuals. The genetic diversity was higher within (95%) rather than among (5%) populations. The Portuguese individuals were structured into two main clusters (K = 2) with low genetic differentiation (FST = 0.04), and the foreign samples were genetically distant from the Portuguese individuals. Conclusion: The six Portuguese P. nigra populations revealed high genetic diversity and seemed to be structured into two main clusters with low differentiation suggesting two provenances or infraspecific taxa. Nonetheless, the comparative analyses with foreign samples did not allow a clear inference about its origin and/or infraspecific taxonomy. Additional foreign samples and/or molecular markers will be tested to pursue these goals. [ABSTRACT FROM AUTHOR]

European black pine (Pinus nigra J.F.Arnold) is an ecologically and economically important conifer growing across southern Europe and the Mediterranean Basin in a variety of habitats. Its morphological and ecological variabilities as well as geographic origin are the basis for subspecies level taxonomic identification and forestry practice recommendations. Yet, no true consensus exists and genomic resources are lacking for resolving the taxonomy of P. nigra and assessing its adaptive potential. To provide genetic tools for further research, we generated novel genomic resources using six de novo transcriptomic assemblies representing major biogeographic regions where the species is growing naturally. Using two closely related species, Pinus sylvestris and Pinus halepensis, as outgroups, we identified a set of 2200 nuclear, putatively orthologous, single-copy genes. In addition, we identified a set of 405,624 polymorphic SNPs for P. nigra. Based on these resources, we were able to confirm the division of P. nigra into two wide geographical population groups and to provide new insights into evolutionary dynamics of the species. [ABSTRACT FROM AUTHOR]

Aim: To test whether intraspecific trait responses to climate among populations across species distribution ranges can be untangled using field observations, under the rationale that, in natural forest tree populations, long‐term climate shapes population responses while recent climate change drives phenotypic plasticity. Location: Europe. Time period: 1901–2014. Taxa: Silver fir (Abies alba Mill.) and sessile oak [Quercus petraea (Matt.) Liebl.]. Methods: We estimated the variation of individual tree height as a function of long‐term and short‐term climates to tease apart provenance effects (variation among populations of different geographical origin), plasticity and their interaction, using mixed‐effect models calibrated with national forest inventory data (in‐situ models). To validate our approach, we tested the ability of in‐situ models to predict independently tree height observations in common gardens experiments where provenance and plastic effects can be measured and separated. In‐situ model predictions of tree height variation among provenances and among planting sites were compared to observations in common gardens and to predictions from a similar model calibrated using common garden data (ex‐situ model). Results: In Q. petraea, we found high correlations between in‐situ and ex‐situ model predictions of provenance and plasticity effects and their interaction for tree height (r > .80). We showed that the in‐situ models significantly predicted tree height variation among provenances and sites for A. alba and Q. petraea. Spatial predictions of phenotypic plasticity across species distribution ranges indicate decreasing tree height in populations of warmer climates in response to recent anthropogenic climate warming. Main conclusions: Our modelling approach using national forest inventory observations provides a new perspective for understanding patterns of intraspecific trait variation across species ranges. Its application is particularly interesting for species for which common garden experiments do not exist or do not cover the entire climatic range of the species. [ABSTRACT FROM AUTHOR]

[Display omitted] • We assessed the impact of genetically enriched material on forests' resilience. • We compared sixteen selected populations with their reference natural population. • We used three comprehensive SNP datasets (overall, common and outlier). • Selected material was significantly differentiated from their original population. • No major genetic diversity loss was detected following genetic selection. • We propose core collections to enrich populations for uncertain future. Delivering material selected for breeding purposes into the wild in the context of sustainable forest management might reduce the levels of genetic diversity of future forests in comparison to that of natural populations. Another consequence might be a reduction of their resilience under uncertain future climatic and socio-economic conditions if these new populations lack adaptability. Despite the long tradition of breeding activities in Europe, there is still a need to assess the impact of genetically enriched material on forests' resilience. In this study, we address (1) the genetic diversity of selected material compared to its wild ancestors, and (2) how to enrich breeding material to support forests' resilience under changing socio-environmental conditions. We analysed 16 study cases of selected material delivered from breeding activities in four European forest tree species (Pinus halepensis Mill., Pinus nigra J.F. Arnold, Pinus pinaster Ait. and Populus nigra L.) with different levels of breeding. To answer these two questions, we first assessed and compared the genetic diversity of selected material versus natural populations using both putatively neutral and adaptive (based on diverging selection) Single Nucleotide Polymorphisms (SNPs). We then suggest how to enrich these populations for resilience under future climatic conditions by defining a core collection for each species including material from populations that will likely disappear under future conditions. Thanks to the large SNP datasets available for our focal species, we were able to detect some trends in our data. Expected and observed heterozygosity values for selected populations were almost always identical. The selected material showed small but significant genetic differentiation from their original population and their inbreeding coefficient was generally lower. However, the level of genetic improvement (i.e. low vs high) was not correlated with the observed genetic differences between selected material and natural populations.The genetic characterization of natural populations distributed across the species range, and the future projection of their range stability, made it possible to identify core-collections that would significantly enrich breeding populations under uncertain future environmental conditions. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides a review of theoretical and practical aspects related to genetic management of forest trees. The implementation of international commitments on forest genetic diversity has been slow and partly neglected. Conservation of forest genetic diversity is still riddled with problems, and complexities of national legal and administrative structures. Europe is an example of a complex region where the distribution ranges of tree species extend across large geographical areas with profound environmental differences, and include many countries. Conservation of forest genetic diversity in Europe has been hampered by a lack of common understanding on the management requirements for genetic conservation units of forest trees. The challenge resides in integrating scientific knowledge on conservation genetics into management of tree populations so that recommendations are feasible to implement across different countries. Here, we present pan-European minimum requirements for dynamic conservation units of forest genetic diversity. The units are natural or man-made tree populations which are managed for maintaining evolutionary processes and adaptive potential across generations. Each unit should have a designated status and a management plan, and one or more tree species recognized as target species for genetic conservation. The minimum sizes of the units are set at 500, 50 or 15 reproducing individuals depending on tree species and conservation objectives. Furthermore, silvicultural interventions should be allowed to enhance genetic processes, as needed, and field inventories carried out to monitor regeneration and the population size. These minimum requirements are now used by 36 countries to improve management of forest genetic diversity. [Copyright &y& Elsevier]

The effect of past environmental changes on the demography and genetic diversity of natural populations remains a contentious issue and has rarely been investigated across multiple, phylogenetically distant species. Here, we perform comparative population genomic analyses and demographic inferences for seven widely distributed and ecologically contrasting European forest tree species based on concerted sampling of 164 populations across their natural ranges. For all seven species, the effective population size, N e , increased or remained stable over many glacial cycles and up to 15 million years in the most extreme cases. Surprisingly, the drastic environmental changes associated with the Pleistocene glacial cycles have had little impact on the level of genetic diversity of dominant forest tree species, despite major shifts in their geographic ranges. Based on their trajectories of N e over time, the seven tree species can be divided into three major groups, highlighting the importance of life history and range size in determining synchronous variation in genetic diversity over time. Altogether, our results indicate that forest trees have been able to retain their evolutionary potential over very long periods of time despite strong environmental changes., (© 2024. The Author(s).)

Phenotypic plasticity and local adaptation are the two main processes underlying trait variability. Under rapid environmental change, phenotypic plasticity, if adaptive, could increase the odds for organisms to persist. However, little is known on how environmental variation has shaped plasticity across species ranges over time. Here, we assess whether the portion of phenotypic variation of tree populations linked to the environment is related to the inter-annual climate variability of the last century and how it varies among populations across species ranges and age. To this aim, we used 372,647 individual tree height measurements of three pine species found in low elevation forests in Europe: Pinus nigra Arnold, P. pinaster Aiton and P. pinea L. Measurements were taken in a network of 38 common gardens established in Europe and North Africa with 315 populations covering the distribution range of the species. We fitted linear mixed-effect models of tree height as a function of age, population, climate and competition effects. Models allowed us to estimate tree height response curves at the population level and indexes of populations' phenotypic variation, as a proxy of phenotypic plasticity, at 4, 8 and 16 years old, and relate these indexes to the inter-annual climate variability of the last century. We found that phenotypic variation in tree height was higher in young trees than in older ones. We also found that P. pinea showed the highest phenotypic variation in tree height compared with P. pinaster and P. nigra. Finally, phenotypic variation in tree height may be partly adaptive, and differently across species, as climate variability during the last century at the origin of the populations explained between 51 and 69% of the current phenotypic variation of P. nigra and P. pinea, almost twice of the levels of P. pinaster. MAIN CONCLUSIONS: Populations' phenotypic variation in tree height is largely explained by the climate variability that the populations experienced during the last century, which we attribute to the genetic diversity among populations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

The dataset presented here was collected by the GenTree project (EU-Horizon 2020), which aims to improve the use of forest genetic resources across Europe by better understanding how trees adapt to their local environment. This dataset of individual tree-core characteristics including ring-width series and whole-core wood density was collected for seven ecologically and economically important European tree species: silver birch (Betula pendula), European beech (Fagus sylvatica), Norway spruce (Picea abies), European black poplar (Populus nigra), maritime pine (Pinus pinaster), Scots pine (Pinus sylvestris), and sessile oak (Quercus petraea). Tree-ring width measurements were obtained from 3600 trees in 142 populations and whole-core wood density was measured for 3098 trees in 125 populations. This dataset covers most of the geographical and climatic range occupied by the selected species. The potential use of it will be highly valuable for assessing ecological and evolutionary responses to environmental conditions as well as for model development and parameterization, to predict adaptability under climate change scenarios.