Background: Genetic processes shape the modern-day distribution of genetic variation within and between populations and can provide important insights into the underlying mechanisms of evolution. The resulting genetic variation is often unequally partitioned within species’ distribution range and especially large differences can manifest at the range limit, where population fragmentation and isolation play a crucial role in species survival. Despite several molecular studies investigating the genetic diversity and differentiation of European Alpine mountain forests, the climatic and demographic constrains which influence the genetic processes are often unknown. Here, we apply non-coding microsatellite markers to evaluate the sporadic peripheral and continuous populations of cembra pine (Pinus cembraL.), a long-lived conifer species that inhabits the subalpine treeline ecotone in the western Alps to investigate how the genetic processes contribute to the modern-day spatial distribution. Moreover, we corroborate our findings with paleoecological records, micro and macro-remains, to infer the species’ possible glacial refugia and expansion scenarios.Results: Four genetically distinct groups were identified, with Bayesian andF_STbased approaches, across the range of the species, situated in the northern, inner and south-western Alps. We found that genetic differentiation is substantially higher in marginal populations than at the center of the range, and marginal stands are characterized by geographic and genetic isolation due to spatial segregation and restricted gene flow. Moreover, multiple matrix regression approaches revealed effects of climatic heterogeneity in species’ spatial genetic pattern. Also, population stability tests indicated that all populations had experienced a severe historical bottleneck, no heterozygosity excess was detected, suggesting that more recently population sizes have remained relatively stable.Conclusions: Our study demonstrated that cembra pine might have survived in multiple glacial refugia and subsequently recolonized the Alps by different routes. Modern-day marginal populations, at the edge of the species’ range, could maintain stable sizes over long periods without inbreeding depression and preserve high amounts of genetic variation. Moreover, our analyses indicate that climatic variability has played a major role in shaping differentiation, in addition to past historical events such as migration and demographic changes.

Scot pine (Pinus sylvestris L.) is one the main forest-forming tree species in Russia, and is of great ecological, economic and social value. In order to manage the genetic resources of this important forest tree species efficiently, knowledge of its genetic diversity and structure is needed. Here, we assessed the genetic variation of 17 populations representing different parts of Scots pine range in Russia by using nuclear microsatellite markers (nSSR). Specifically, 14 populations were chosen within the natural distribution range of the species in Middle Siberia and three distant populations were sampled from the European part of Russia, the West Siberia and the Russian Far East. All populations showed high values of genetic diversity (H_E = 0.514) and A_R = 4.150. However, the easternmost population has shown the lowest level of genetic diversity (H_E = 0.433) and allelic richness (A_R = 3.505). Five genetic groups could be detected that correspond to: the European part of Russia, the south of Middle Siberia, the northwest of Middle Siberia, West and Middle Siberia, and the Russian Far East. However, the European population was the most genetically distinct one. The variation among Scots pine populations accounted for only 5% of the total variance. The highest level of genetic differentiation was found only between westernmost and easternmost populations (F_ST = 0.097). Our genetic data may contribute to a better understanding of the pattern of genetic diversity of Scots pine populations in Middle Siberia and help the conservation efforts of these genetic resources.

Turkey oak (Quercus cerris L.) is a deciduous tree species of the genus Quercus section Cerris (Fagaceae), widely distributed in Europe and Asia Minor. Throughout its vast distribution range, the species carries high phenotypic and genetic variability. Due to its high drought tolerance, Turkey oak may have great potential to be a key tree species in Central and Western Europe under climate change conditions. However, more detailed information on its phylogeny, phylogeography, phenotypic, and genetic variability is still needed for a more careful and reliable assessment of the species’ adaptation potential. To this end, based on 41 reviewed articles, we collected detailed information to support the evaluation of Turkey oak’s adaptation potential under climate change. In the reviewed articles, we observed a significantly lower number of genetic studies of the members of the section Cerris (especially the Euro-Mediterranean species) relative to the subgenus Quercus. We also identified research gaps with respect to the functional and population genetics of the species that should be addressed in the future. Nevertheless, the different evolutionary background and adaptation strategies of Turkey oak as compared to Central European white oaks, as well as its high phenotypic and genetic variability, may indeed represent a great potential for this species to support the climate adaptation of forestry in Central and Western Europe.

Knowledge on the genetic composition of Quercus petraea in south-eastern Europe is limited despite the species’ significant role in the re-colonisation of Europe during the Holocene, and the diverse climate and physical geography of the region. Therefore, it is imperative to conduct research on adaptation in sessile oak to better understand its ecological significance in the region. While large sets of SNPs have been developed for the species, there is a continued need for smaller sets of SNPs that are highly informative about the possible adaptation to this varied landscape. By using double digest restriction site associated DNA sequencing data from our previous study, we mapped RAD-seq loci to the Quercus robur reference genome and identified a set of SNPs putatively related to drought stress-response. A total of 179 individuals from eighteen natural populations at sites covering heterogeneous climatic conditions in the southeastern natural distribution range of Q. petraea were genotyped. The detected highly polymorphic variant sites revealed three genetic clusters with a generally low level of genetic differentiation and balanced diversity among them but showed a north–southeast gradient. Selection tests showed nine outlier SNPs positioned in different functional regions. Genotype-environment association analysis of these markers yielded a total of 53 significant associations, explaining 2.4–16.6% of the total genetic variation. Our work exemplifies that adaptation to drought may be under natural selection in the examined Q. petraea populations.

Soil bacterial communities play a remarkable role in nutrient cycling, significantly affecting soil organic material content, soil fertility, and, in an indirect way, plant succession processes. Conversely, vegetation type influences microbial soil life. The present study compared the bacterial microbiome composition, diversity and catabolic activity profile of topsoil samples collected under three different forest types (a twice-coppiced black locust stand, a young, naturally reforested, and a middle-aged mixed pedunculate oak stand) planted on former arable land in the early 20th century. Diversity indices determined during 16S ribosomal RNA sequencing-based metagenome analysis indicated that the black locust stand had the highest soil bacterial community diversity. At the phylum level, Acidobacteriota, Actinobacteriota, Proteobacteria, Verrucomicrobiota, Bacteroidota, and Gemmatimonadota were the most abundant taxa in the forest soils. Concerning soil parameters, redundancy analysis revealed that pH had the highest impact on bacterial community structure and pH, and soil organic carbon content on the samples’ respiration patterns. As for catabolic activity, the recently clearcut oak forest showed the lowest substrate-induced respiration, and citrate was the main driver for the inter-stand variability of microbial activity. Our results confirm that soil parameters and forest type influence the composition and functioning of the soil bacterial microbiome.