We assessed genetic diversity of naturally expanding Norway maple populations in Lithuania, focusing on potential genetic risks associated with spontaneous colonization. We genotyped 186 trees within a single forest stand and 390 trees across 21 populations in Lithuania at seven nuclear microsatellite loci. Significant bottleneck effects were detected, particularly in northern populations, where Norway maple presence is scarce. These northern populations exhibited the lowest genetic diversity (Ho = 0.57-0.65; FIS = 0.15-0.20) and elevated relatedness, in contrast to the more diverse north-eastern populations (Ho = 0.65-0.80; FIS = 0.04-0.10). Population differentiation was low (FST = 0.054***), and the genetic structure was more uniform than expected for a strictly entomophilous species. Bayesian clustering identified genetically distinct groups in north-eastern Lithuania. Genetic differentiation among genetic clusters within a single stand (FST = 0.098) was nearly twice that observed among populations in Lithuania. Our findings suggest that the spontaneous spread of Norway maple may result in (a) genetically eroded groups of closely related individuals, as observed in northern Lithuania, or (b) the development of internal genetic structuring within populations, leading to deviations from random mating and increased inbreeding. Such populations may require targeted genetic diversity enrichment.

As pressures from climate change and global trade increase, developing cost-effective tools for origin tracking becomes essential to ensure the traceability and adaptability of forest reproductive material (FRM). Our objectives were (a) to test the efficiency of a set of nuclear microsatellite loci (nSSR) for revealing the genetic structures identified by high-input sequencing studies and (b) to verify this set of nSSR loci for genetic assignment of commercial seed lots into reference regions. We used 12 nSSR markers to genotype 220 trees from 11 populations representing the eastern Baltic, Scandinavian and southern European ranges of Norway spruce. The results showed that the populations from the eastern Baltic range had relatively higher allelic diversity parameters. The Bayesian clustering revealed a geographically consistent genetic structuring of Norway spruce populations by distinguishing the eastern Baltic from southern European and Scandinavian populations. GENECLASS analysis correctly assigned Lithuanian commercial seed lots into the Lithuanian reference region with markedly higher probability than to any other reference regions. Our study demonstrates promising results for origin identification of Norway spruce, particularly in contexts where high-resolution genomic approaches remain financially or logistically inaccessible.

European beech (Fagus sylvatica L.) has a wide distribution range through Central and Western Europe, and is tolerant to a range of environmental factors and shade. Due to the high wood quality and growth rate, there is increasing interest in the cultivation of this species in Northern Europe, and European beech is appropriate for closer-to-nature forestry management practices, where shade-tolerant species are essential. Latvia is located to the north of the natural range of European beech, but stands have been successfully established in the 19th century, using reproductive material of unknown origin. This study investigated the natural regeneration, genetic diversity, population structure, and provenance of Latvian F. sylvatica populations from two areas in western Latvia—Skede and Kaleti. Parent–offspring analyses did not identify a decrease in genetic diversity parameters in the naturally regenerated offspring, indicating that natural regeneration has not decreased the genetic viability of these populations. The three stands located in Skede were genetically very similar (pairwise Fst values ranged from 0.004 to 0.007). The Kaleti stand was more differentiated from the Skede stands (pairwise Fst values with the Skede stands ranged from 0.047 to 0.051), and the genetic diversity was low (He = 0.638). This is probably a result of the use of reproductive material collected from a very limited number of individuals to establish this stand, which also prevented the determination of the origin of this material. The Skede stand was compared to German, Polish, and Swedish F. sylvatica populations, and a Bayesian clustering analysis indicated that the most likely provenance of the Skede stand in Latvia was from southern Germany.

We investigated the presence of spatial genetic groups within forest tree populations and determined if the genetic divergence among these groups is greater than that between populations using Scots pine (Pinus sylvestris) as a model species. We genotyped 890 adult trees of Scots pine in six natural populations in Lithuania at 11 nuclear microsatellite loci. We used a Bayesian clustering approach to identify the within-population genetic groups within each of the six populations. We calculated the differentiation indexes among the genetic groups within each population and among the six populations by ignoring the genetic groups. The Bayesian clustering revealed 2 to 6 distinct genetic groups of varying size as the most likely genetic structures within populations. The genetic differentiation indexes among the genetic groups within populations were nearly tenfold greater (FST = 0.012–0.070) than those between the populations (FST = 0.003). We conclude on the existence of markedly stronger structuring of genetic variation within populations than between populations of Scots pine in large forest tracts of northern Europe. Such genetic structures serve as a contributing factor to large within population genetic diversity in northern conifers. We assume that within population mating in Scots pine is not completely random but rather is stratified into genetic clusters. Our study provides pioneering novel key insights into structuring of genetic variation within populations. Our findings have implications for examining within-population genetic diversity and genetic structure, conservation, and management of genetic resources.

It is crucial for northerly Norway spruce to understand how seasonal warming and site conditions influence the intensity of free growth and what the effects of free growth on stem quality and adaptedness are. We studied the intensity of sylleptic and proleptic free growth in 660 6-to-9-year-old Norway spruce trees planted on normally irrigated and temporary overmoistured sites of variable fertility. We focused on the ability of individual trees to retain a type of free growth over three seasons and examined the associations between free growth, stem quality, and phenology traits. The results show that 23% to 50% of trees exhibited free growth, depending on the season. Mild and warm conditions in August and September tended to promote free growth. Among trees aged 6 to 9 years, 82% to 84% of those without free growth maintained this status over the following two seasons. While sylleptic growth decreased with age, proleptic growth increased. Over the seasons, individual trees were more consistent in maintaining proleptic growth than sylleptic growth. Trees on moist site types exhibited significantly more free growth than those in normally irrigated sites across all seasons. Trees with both sylleptic and proleptic free growth were significantly taller than those without free growth; however, sylleptic trees showed a markedly lower frequency of stem defects compared with those with proleptic growth. Free growth intensity was weakly associated with spring phenology and appeared to disrupt the well-established associations between phenology traits within the annual cycle. We conclude that selecting trees for overall height, particularly those with sylleptic free growth, may well exploit the benefits of free growth without significantly increasing the risk of autumn or winter frost damage.

We benefited from the availability of a species-specific DNA marker to describe the morphometry of T. cordata × platyphyllos hybrids of an impressive age (ca. 150 years) grown in the Pazaislis baroque monastery yard in Central Lithuania. In an earlier study on a country-wide set of 543 T. cordata individuals from natural forest populations in Lithuania, we detected a nuclear microsatellite locus Tc8 well-differentiating between T. cordata and T. platyphyllos. The Tc8 locus contained a 140 bp allele in T. cordata (541 sampled individuals) and alleles above 160 bp in the two trees with a T. platyphyllos-like morphology (sampled in a national park). To verify the Tc8 locus as species specific, we sampled a further four T. platyphyllos-like individuals, which all contained the Tc8 locus alleles above 160 bp. We subsequently genotyped the six old-growth individuals from the Pazaislis monastery with mixed T. cordata × platyphyllos morphology. Results revealed that all six old-growth Tilia individuals from the Pazaislis monastery were heterozygous for the Tc8 locus with alleles of 140 bp (indicative of T. cordata) and 162 bp (indicative of T. platyphyllos). This finding confirms the morphological observations that these individuals are hybrids between T. cordata and T. platyphyllos. Additionally, the genotyping of a set of 14 nuclear microsatellite loci revealed that all six trees from the Pazaislis monastery are clones, possessing identical microsatellite genotypes. After the molecular identification, we morphotyped leaves, bracts, twigs, and nuts of the 6 old-growth T. cordata × platyphyllos hybrids from the Pazaislis monastery, 16 T. cordata old-growth trees, 4 T. × europaea var. europaea ‘Pallida’ trees growing near the Pazaislis monastery, and 4 mature T. platyphyllos trees from a nearby Girionys park. The morphotyping showed that T. cordata × platyphyllos hybrids may be the easiest to distinguish from T. cordata by raised and horizontally tertiary veins of leaves.

We tested the hypothesis that old-growth unmanaged (OGU) forests have higher genetic diversity than second-growth managed (SGM) forests and systematic forest tending markedly reduces genetic diversity and alters the fine-scale spatial genetic structure (SGS) of contemporary generation in natural populations, employing Scots pine ( Pinus sylvestris L.). We examined genetic diversity, differentiation and SGS of three OGU and three post-tending natural SGM populations of Scots pine on similar ecosites in different parts of Lithuania by genotyping 890 mature trees at 11 nuclear microsatellite loci. The genetic differentiation between OGU and SGM population groups was not significant. Although OGU populations had higher allelic diversity, effective population size ( N e ) and higher inbreeding coefficient than SGM populations, the differences between OGU and SGM populations were not significant for these parameters. However, we found a significant loss of OGU-specific private rare alleles, copies of rare alleles and genotypic diversity in the SGM populations. OGU populations had significantly stronger SGS and larger neighborhood size than SGM populations. We infer that systematic tending in natural Scots pine forests does not cause a significant reduction in common genetic diversity parameters and reduces SGS by disrupting clusters of relatives. However, it does cause significant loss of rare alleles and genotypic diversity and some genetic differentiation from OGU. We suggest genetic monitoring for genetic diversity conservation and N e maintenance, and developing forest management and gene conservation guidelines for better conservation of rare alleles and genotypic diversity.

We studied the associations between the stem quality, phenology, and genetic structure by genotyping the phenotypic variation at 15 genomic SSR makers of 208 mature European beech trees in four artificially established stands in Lithuania. The genetic differentiation among the stands was significant (D-EST = 0.029**). The stand NOR1 of Carpathian origin significantly differed from the remaining three stands of Bavarian origin at the highest 0.001 significance level. In most of the stands, the early flushing trees were of significantly worse stem quality. Within each of the stands, the Bayesian clustering identified 2 to 3 genetic groups, among which the differentiation was markedly stronger than between the stands (D-EST 0.095*** to 0.142***). The genetic groups differed markedly in stem quality and phenology as well as inbreeding levels. We conclude that (a) the genetic structuring in European beech stands strongly depends on non-random mating owing to phenology variation among the relative groups, (b) due to strong relationship among phenology, adaptedness and stem morphotype, this genetic variation is reflected by the stem morphotype.

Scots pine is economically and ecologically important forest tree species in Lithuania. According to the Regulation of Forest Planting and Restoration of Lithuania (2018) and the Regulations on Forest Reproductive Material (FRM) (2017) forests must be planted and replanted with the target tree species, using high quality seeds and seedlings from a given provenance. EU Council Directive (1999/105/EC) indicates that EU Member States are responsible for the regulation, requirements and implementation of FRM quality and traceability system. The existing FRM control system in Lithuania is based on the control actions of the supporting documents regarding the origin of FRM. However, this FRM traceability system is limited and, in some cases, cannot ensure that FRM used for reforestation/afforestation originates from the declared place of origin or belongs to a certain seed or plant lot. In this study we aimed to assess and compare genetic diversity of scots pine seed orchard clones with seeds, and to test DNA based parentage analysis methods with Jonava scots pine seed orchard clones and seeds. Up to now DNA markers based FRM traceability system in Lithuania has not been tested and implemented. Thus, our first results based on 12 nuclear microsatellite markers indicated that genetic diversity among Jonava seed orchard clones and collected seeds were moderately high and comparable with other studies on scots pine in Europe. The test of the maternity analysis software CERVUS has showed very positive results in maternity assignments. Therefore, selected microsatellite markers in combination with accurate sampling design and specific DNA analysis methods should be improved and can be used for FRM traceability system based on DNA “fingerprints”.

Due to complex history of European forests, natural populations may not necessarily represent autochthonous genepools for forest trees. Eastern Prussian forests were famous for using non-local sources for afforestation. We studied efficiency of a set of nuclear microsatellite markers (nSSR) for genetic association and diversity studies of 194 adult trees from 5 populations genotyped at 11 nSSR loci. The Bayesian and UPGMA clustering revealed two genetically distinct groups: (a) the Baltic group, and (b) the Bavarian one and an over 200-years-old sea-side Lithuanian population of Juodkrante from the sea-side Curonian spit of Neringa. We interpret this result as putative introduction of Bavarian Scots pine back in the 18th century, when reforestation efforts were made to sustain moving sands in the dunes of Neringa. The genomic SSRs were more variable than the EST SSRs. However, the association between the variability of the nuclear microsatellite loci and their efficiency in detecting population differentiation was not strong. Keywords: nSSR, Pinus sylvestris (L.), population structure, provenance transfer, FRM transfer, molecular markers

We studied the genetic differentiation, structure, and diversity of Scots pine populations in Lithuania based on nuclear, chloroplast microsatellite, and mitochondrial DNA markers. We focused on revealing evolutionary history, country-wide geneflow patterns, and structuring among the Scots pine populations. We genotyped 439 Scots pine individuals of mature age from 23 natural Scots pine stands in Lithuania and used the AMOVA and a set of genetic-clustering methods. The among-population differentiation was weak for nuclear microsatellite loci (nSSRs) (FST = 0.005) but much stronger for cpSSRs (PhiST = 0.240). The populations were structured into highland and lowland populations based on cpSSRs and eastern highland versus the rest for nSSRs. We detected two mtDNA mitotypes—the universal type A and northeastern type B, and the latter occurred at a markedly higher frequency in eastern Lithuania. Within-population genetic diversity was higher in large pine-dominated forest tracts in the eastern highlands than in fragmented forests in the western highlands. We concluded that phenology-based genetic networks following the temperature climate gradients have a strong effect on shaping the genetic structure of otherwise rather homogeneous gene pools of Scots pine populations in Lithuania. The possible effects of human interference with forests on genetic diversity of Scots pine populations in Lithuania are discussed.

Lietuvos miškotyros mokslininkai savo tyrimų rezultatus komunikuoja dažniausiai moksliniuose renginiuose bei leidiniuose užsienyje, paprastai anglų kalba. Lietuvoje vykstančiose konferencijose, praktiniuose seminaruose rezultatus dažniausia pateikia mokslinę karjerą tik pradedantys mokslininkai ar studentai, kurie disponuoja paprastai tik nesenai pradėtų tyrimų duomenimis. Santykinai aukštesnio lygio mokslininkams dalyvavimas nacionalinio lygio mokslo komunikavimo projektuose paprastai netikslingas ir dėl nepakankamo tokios veiklos pripažinimo. Todėl šio projekto naujumą sudaro (i) siekis sutelkti visus – įvairiose tematikose bei institucijose dirbančius, įvairių karjeros etapų, pradedant studentais, baigiant akademikais – miškotyros mokslininkus Lietuvoje pristatyti savo mokslinius pasiekimus bei ateities vizijas vienodu, į mokslo populiarinimą orientuotu formatu bei (ii) parengti leidinį, apibendrinantį miškotyros mokslą formatu ir turiniu, kuris Lietuvos miškotyroje nebuvo taikytas. Projekto aktualumas yra susijęs miškininkystės mokslo ir, per tai, miškininkystės studijų programų populiarinimu nauju formatu, kuris, tikimasi, padės geriau pasiekti tikslinę auditoriją (t.y. ne tik profesionalius miškotyros mokslininkus). Projektas tiesiogiai atitinką vieną iš Nacionalinio miškų susitarimo siekių: „Siekti, kad mokslo populiarinimas ir ryšys su visuomene taptų vienu iš kriterijų vertinant mokslo tiriamuosius projektus, plačiajai visuomenei pritaikyti mokslinių tyrimų rezultatai būtų dažniau pateikiami ir viešinami įvairiose medijose“.

Abstract Tilia cordata Mill. is a valuable tree species enriching the ecological values of the coniferous‐dominated boreal forests in Europe. Following the historical decline, spreading of Tilia sp. is challenged by the elevated inbreeding and habitat fragmentation. We studied the geographical distribution of genetic diversity of Tilia cordata populations in Lithuania. We used 14 genomic microsatellite markers to genotype 543 individuals from 23 wild‐growing populations. We found that Tilia cordata retained high levels of genetic diversity (population F IS = 0–0.15, H o = 0.53–0.69, H e = 0.56–0.75). AMOVA, Bayesian clustering, and Monmonier's barrier detection indicate weak but significant differentiation among the populations (F ST = 0.037***) into geographically interpretable clusters of (a) western Lithuania with high genetic heterogeneity but low genetic diversity, bottleneck effects, (b) relatively higher genetic diversity of Tilia cordata on rich and most soils of midland lowland, and (c) the most differentiated populations on poor soils of the coolest northeastern highland possessing the highest rare allele frequency but elevated inbreeding and bottleneck effects. Weak genetic differentiation among the Tilia cordata populations in Lithuania implies common ancestry, absence of strong adaptive gradients, and effective genetic exchange possible mediated via the riparian networks. A hypothesis on riparian networks as gene flow mediators in Tilia cordata was raised based on results of this study.

Motivation: Trait variation within species can reveal plastic and/or genetic responses to environmental gradients, and may indicate where local adaptation has occurred. Here, we present a dataset of rangewide variation in leaf traits from seven of the most ecologically and economically important tree species in Europe. Sample collection and trait assessment are embedded in the GenTree project (EU-Horizon 2020), which aims at characterizing the genetic and phenotypic variability of forest tree species to optimize the management and sustainable use of forest genetic resources. Our dataset captures substantial intra- and interspecific leaf phenotypic variability, and provides valuable information for studying the relationship between ecosystem func-tioning and trait variability of individuals, and the response and resilience of species to environmental changes. Main types of variable contained: We chose morphological and chemical characters linked to trade-offs between acquisition and conservation of resources and water use, namely specific leaf area, leaf size, carbon and nitrogen content and their ratio, and the isotopic signature of stable isotope 13C and 15N in leaves. Spatial location and grain: We surveyed between 18 and 22 populations per species, 141 in total, across Europe. Time period: Leaf sampling took place between 2016 and 2017. Major taxa and level of measurement: We sampled at least 25 individuals in each population, 3,569 trees in total, and measured traits in 35,755 leaves from seven European tree species, i.e. the conifers Picea abies, Pinus pinaster and Pinus sylvestris, and the broadleaves Betula pendula, Fagus sylvatica, Populus nigra and Quercus petraea. Software format: The data files are in ASCII text, tab delimited, not compressed.

Spontaneous hybrids between the native elms (genus Ulmus L.) have been observed in the forests of Europe. Gene conservation raises questions regarding the genetic background for the complex morphology and taxonomy of elms. Our objective was to dissect morphological and genetic variation in the natural swamps of Ulmus species groups in Lithuanian forests with the aid of leaf morphology and microsatellite (SSR) markers. We sampled leaves from 189 elms at 26 locations to grasp the phenotypic diversity in variable natural habitats in Lithuanian forests. We assigned the elms into six taxonomic and genetics groups based on 31 leaf morphology parameters and tested the genetic differentiation between these six groups at six nuclear SSR loci by using Bayesian and genetic distance-based clustering. The genetic and leaf morphometric analyses of putative elm hybrid swamps indicated a low genetic exchange between U. laevis Pall. and the other Ulmus groups. The genetic and morphometric data supported the differentiation of U. glabra Huds. and U. glabra (female) × U. minor Mill. (male) spontaneous hybrids. In addition, the results of the genetic analysis also confirmed the high level of genome sharing among U. minor and U. minor subsp. minor Richens., where leaf morphology failed to differentiate genetically discrete groups. For gene conservation, we would suggest considering separate gene conservation units selected based on leaf and stem morphology for U. laevis, U. glabra, U. glabra × minor, and the U. minor species complex.

This dataset is the result of a survey conducted during the 2012-2016 COST Action FP1202 (MaP-FGR): Strengthening conservation: a key issue for adaptation of marginal/peripheral populations of forest trees to climate change in Europe. It contains the name, location and other relevant information of 577 forests that are considered as marginal of peripheral by forest experts. Information (as specified in the read-me file) includes among others: Genus, Species, Country, Name of marginal population, Latitude, Longitude, Elevation, Type of marginality, Silvicultural system, Protection status, Threat status, and genetic and phenotypic trait data availability This dataset can be used to, e.g., test effects of marginality on biological and genetic traits, compare expert knowledge with statistics-based indicators, raise awareness of the importance of marginal populations for conservation and sustainable use.

Two alder species (Alnus glutinosa and A. incana) have overlapping distribution, naturally occur in Lithuania, and are considered ecologically and economically important forest tree species. The objective of our study was to estimate the likelihood of spontaneous hybridizations between native alders in natural stands of Lithuania based on leaf morphology and nuclear microsatellite markers. The sampled trees were assigned to the three taxonomic groups of A. glutinosa, A. incana, and potential hybrids based on the leaf and bark morphological traits. The genetic differentiation and potential hybridization between these three groups was tested based on 15 nSSR markers. We identified studied Alnus spp. individuals as pure species and hybrids. Two microsatellite loci were reported as discriminating well between these species. We concluded that our results showed the highest likelihood of two genetic group structures, a clear genetic differentiation between the morphology-based groups of A. glutinosa and A. incana, and rather variable likelihood values in the putative hybrid group. The results provide important implications for genetic conservation and management of Alnus spp.

SummaryEarly‐stage fitness variation has been seldom evaluated at broad scales in forest tree species, despite the long tradition of studying climate‐driven intraspecific genetic variation. In this study, we evaluated the role of climate in driving patterns of population differentiation at early‐life stages inPinus sylvestrisand explored the fitness and growth consequences of seed transfer within the species range.We monitored seedling emergence, survival and growth over a 2‐yr period in a multi‐site common garden experiment which included 18 European populations and spanned 25° in latitude and 1700 m in elevation.Climate–fitness functions showed that populations exhibited higher seedling survival and growth at temperatures similar to their home environment, which is consistent with local adaptation. Northern populations experienced lower survival and growth at warmer sites, contrary to previous studies on later life stages. Seed mass was higher in populations from warmer areas and was positively associated with survival and growth at more southern sites. Finally, we did not detect a survival–growth trade‐off; on the contrary, bigger seedlings exhibited higher survival probabilities under most climatic conditions.In conclusion, our results reveal that contrasting temperature regimes have played an important role in driving the divergent evolution ofP. sylvestrispopulations at early‐life stages.

This dataset consists of combined field transect data and data from a provenance trial. Geographic coordinates and selected Worldclim climatic parameters (mean annual temperature, mean temperature of the warmest quarter and mean annual precipitation) for each sampling site or the original provenance site.are given. For each sampling site we give mean needle length, width, and stomatal traits for each needle surface (number of stomatal rows and stomatal density) as well as the projected stomatal density..

We studied the maternally inherited chloroplast DNA polymorphism at three microsatellite loci of 157 Quercus robur trees from 38 native populations in Lithuania. We found high diversity of eight haplotypes from the Balkan lineage A (frequency 0.75) and the "German" subbranch of the Balkan lineage A (freq. 0.12), western and eastern Italian lineages C (freq. 0.05 and 0.06, respectively), and Iberian lineage B (freq. 0.03). The haplotypes were geographically well structured (among population differentiation index PhiPT = 0.30, the p-value < 0.001) that is unexpected for such a small territory as Lithuania. We raised a hypothesis on historical overexploitation of oaks by eliminating certain haplotypes in Lithuania, following a drastic felling of oak forests over the last few centuries.