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As for most other temperate broadleaved tree species, large-scale genetic inventories of pedunculate oak (Quercus robur L.) have focused on the plastidial genome, which showed the impact of post-glacial recolonization and manmade seed transfer. However, how have pollen mediated gene flow and introgression impacted the large-scale genetic structure? To answer these questions, we did a genetic inventory on 1970 pedunculate oak trees from 197 locations in 13 European countries. All samples were screened with a targeted sequencing approach on a set of 381 polymorphic loci (356 nuclear SNPs, 3 nuclear InDels, 17 chloroplast SNPs, and 5 mitochondrial SNPs). In a former analysis with additional 1763 putative Quercus petraea trees screened for the same gene markers we obtained estimates on the species admixture of all pedunculate oak trees. We identified 13 plastidial haplotypes, which showed a strong spatial pattern with a highly significant autocorrelation up to a range of 1250 km. Significant spatial genetic structure up to 1250 km was also observed at the nuclear loci. However, the differentiation at the nuclear gene markers was much lower compared to the organelle gene markers. The matrix of genetic distances among locations was partially correlated between nuclear and organelle genomes. Bayesian clustering analysis revealed the best fit to the data for a sub-division into two gene pools. One gene pool is dominating the west and the other is the most abundant in the east. The western gene pool was significantly influenced by introgression from Quercus petraea in the past. In Germany, we identified a contact zone of pedunculate oaks with different introgression intensity, likely resulting from different historical levels of introgression in glacial refugia or during postglacial recolonization. The main directions of postglacial recolonization were south to north and south to northwest in West and Central Europe, and for the eastern haplotypes also east to west in Central Europe. By contrast, the pollen mediated gene flow and introgression from Q. petraea modified the large-scale structure at the nuclear gene markers with significant west–east direction.

Climate change is increasing insect pressure and forcing plants to adapt. Although chemotypic differentiation and phenotypic plasticity in spatially separated tree populations are known for decades, understanding their importance in herbivory resistance across forests remains challenging. We studied four oak forest stands in Germany using nontarget metabolomics, elemental analysis, and chemometrics and mapped the leaf metabolome of herbivore-resistant (T-) and herbivore-susceptible (S-) European oaks (Quercus robur) to Tortrix viridana, an oak pest that causes severe forest defoliation. Among the detected metabolites, we identified reliable metabolic biomarkers to distinguish S- and T-oak trees. Chemotypic differentiation resulted in metabolic shifts of primary and secondary leaf metabolism. Across forests, T-oaks allocate resources towards constitutive chemical defense enriched of polyphenolic compounds, e.g. the flavonoids kaempferol, kaempferol and quercetin glucosides, while S-oaks towards growth-promoting substances such as carbohydrates and amino-acid derivatives. This extensive work across natural forests shows that oaks' resistance and susceptibility to herbivory are linked to growth-defense trade-offs of leaf metabolism. The discovery of biomarkers and the developed predictive model pave the way to understand Quercus robur's susceptibility to herbivore attack and to support forest management, contributing to the preservation of oak forests in Europe.

Oaks are one of the most important and most common deciduous tree species in the forests of Central Europe, accounting for 10% of the total area. However, due to progressive global warming, the oak is increasingly exposed to biotic and abiotic stressors. In addition to drought and heat, thermophilic herbivorous insects are also a challenge for the oaks. During studies on the green oak leaf roller (Tortrix vidiana L.) in North Rhine-Westphalia (Germany), differences in the infestation intensity of individual oaks by this herbivorous moth were found, which led to a definition of tolerant (T-oaks, little defoliated) and susceptible (S-oaks, heavily defoliated) oaks. To validate results from conducted biochemical and molecular studies, ethological studies were carried out with the specialist Tortrix viridana (2013) and the generalist Lymantria dispar L. (gypsy moth) (2019). The parameters used to determine the performance of these herbivorous insects on the two different oak genotypes were developmental time, amount of fed leaves, and mortality of larvae and pupae during the juvenile phase. While the overall developmental time of green oak leaf roller larvae did not show a significant difference on S- and T-oaks, especially the female larvae of Lymantria dispar needed a longer developmental time on T-oaks. On T-oaks, larvae of Tortrix viridana had to consume significantly more leaf material to achieve approximately the same pupal weight as larvae fed on S-oaks. In contrast, larvae of the gypsy moth tended to ate less T-oak than S-oak leaf material without revealing differences in pupal weights. For the green oak leaf roller the mortality of pupae from T-oaks was significantly higher than from S-oaks. For Lymantria dispar no significant differences in mortality was observed. Basically, T-oaks seem to offer a poorer nutritional and developmental basis for both kinds of leaf-eating insects.

European beech, Fagus sylvatica L., is one of the most important and widespread deciduous tree species in Central Europe and is widely managed for its hard wood. The complete DNA sequence of the mitochondrial genome of Fagus sylvatica L. was assembled and annotated based on Illumina MiSeq reads and validated using long reads from nanopore MinION sequencing. The genome assembled into a single DNA sequence of 504,715 bp in length containing 58 genes with predicted function, including 35 protein-coding, 20 tRNA and three rRNA genes. Additionally, 23 putative protein-coding genes were predicted supported by RNA-Seq data. Aiming at the development of taxon-specific mitochondrial genetic markers, the tool SNPtax was developed and applied to select genic SNPs potentially specific for different taxa within the Fagales. Further validation of a small SNP set resulted in the development of four CAPS markers specific for Fagus, Fagaceae, or Fagales, respectively, when considering over 100 individuals from a total of 69 species of deciduous trees and conifers from up to 15 families included in the marker validation. The CAPS marker set is suitable to identify the genus Fagus in DNA samples from tree tissues or wood products, including wood composite products.

Background Herbivorous insects can have a profound impact on plant growth performance. In some years, canopy damage in poplar plantations exceeds 50% of the total leaf surface, thereby possibly compromising carbon fixation and biomass yield. To assess the transcriptional response of elite poplar clones to insect feeding and to test whether this response varies between different genotypes, we performed an RNA-sequencing experiment. We deeply sequenced the transcriptomes of eight elite clones belonging to three poplar species (Populus trichocarpa, P. nigra and P. maximowiczii), under Phratora vitellinae feeding and control conditions. This allowed us to precisely quantify transcript levels of about 24,000 expressed genes. Results Our data reveal a striking overall up-regulation of gene expression under insect attack in all eight poplar clones studied. The up-regulated genes were markedly enriched for the biological process ‘regulation of transcription’ indicating a highly concerted restructuring of the transcriptome. A search for potential cis-regulatory elements (CREs) that may be involved in this process identified the G-box (CACGTG) as the most significant motif in the promoters of the induced genes. In line with the role of the G-box in jasmonate (JA)-mediated activation of gene expression by MYC2, several genes involved in JA biosynthesis and signaling were up-regulated in our dataset. A co-expression network analysis additionally highlighted WRKY transcription factors. Within the most prominent expression module, WRKYs were strongly overrepresented and occupied several network hubs. Finally, the insect-induced genes comprised several protein families known to be involved in plant defenses, e.g. cytochrome P450s, chitinases and protease inhibitors. Conclusions Our data represent a comprehensive characterization of the transcriptional response of selected elite poplar clones to insect herbivory. Our results suggest that the concerted up-regulation of gene expression is controlled by JA signaling and WRKY transcription factors, and activates several defense mechanisms. Our data highlight potential targets of selection and may thus contribute to breeding insect-resistant poplar clones. Electronic supplementary material The online version of this article (10.1186/s12864-019-6048-8) contains supplementary material, which is available to authorized users.

The Swiss pine (Pinus cembra) is a montane tree in Central Europe and, therefore, known for its hardiness against severe winter colds. The seeds are harvested and eaten as pine nuts. We assembled and characterized the complete chloroplast genome of P. cembra to serve as a valuable resource in future genetic studies. The complete plastome sequence is 116,609 bp in length and contains 113 genes including 79 protein-coding genes, 30 tRNA genes, and 4 rRNA genes. A phylogenetic analysis of 34 Pinus plastome sequences shows that Pinus sibirica is the nearest relative to P. cembra and that there is a distinct clustering together with the other members of the section Quinquefoliae.

The indirect defences of plants are comprised of herbivore-induced plant volatiles (HIPVs) that among other things attract the natural enemies of insects. However, the actual extent of the benefits of HIPV emissions in complex co-evolved plant-herbivore systems is only poorly understood. The observation that a few Quercus robur L. trees constantly tolerated (T-oaks) infestation by a major pest of oaks (Tortrix viridana L.), compared with heavily defoliated trees (susceptible: S-oaks), lead us to a combined biochemical and behavioural study. We used these evidently different phenotypes to analyse whether the resistance of T-oaks to the herbivore was dependent on the amount and scent of HIPVs and/or differences in non-volatile polyphenolic leaf constituents (as quercetin-, kaempferol- and flavonol glycosides). In addition to non-volatile metabolic differences, typically defensive HIPV emissions differed between S-oaks and T-oaks. Female moths were attracted by the blend of HIPVs from S-oaks, showing significantly higher amounts of (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and (E)-β-ocimene and avoid T-oaks with relative high fraction of the sesquiterpenes α-farnesene and germacrene D. Hence, the strategy of T-oaks exhibiting directly herbivore-repellent HIPV emissions instead of high emissions of predator-attracting HIPVs of the S-oaks appears to be the better mechanism for avoiding defoliation.

Cyclic population dynamics of forest insects with periods of more than two generations have been discussed in relation to a variety of extrinsic and intrinsic forces. In the present study, we employed the selection pressure of density dependent competitive interactions according to Witting's equations (Witting, 2000) as driver for a discrete spatiotemporal model of the green oak leaf roller (Tortrix viridana). The model was successfully parameterised to rebuild the cyclic population dynamics of an empirical data set of a 30-year leaf roller monitoring in Russia. Our analysis focussed on the role of herbivore mortality and host plant food quality, which have a significant effect on T. viridana population dynamics. An additional egg or larvae mortality lowers population density and can lead to selection pressures that favour individuals with higher growth rate. This increased population growth rate can not only compensate the additional mortality, but also can lead to higher average moth abundances in subsequent generations. Furthermore, we analysed the effect of inter- and intraspecific variation in host plant quality on herbivore population dynamics and the spatial distribution of abundance and defoliation patterns. We found significant effects of the qualitative composition of a trees neighbourhood on the herbivore population of the respective tree. Also, the patchy damage patterns observable in reality have been reproduced by the present model. The applicability of the model approach and the putative genetic processes underlying Witting's model are discussed.

A geographically isolated population of an herbivorous insect (Tortrix viridana, Lepidoptera: Tortricidae) in the Bashkir Transural region and 5 further populations were investigated for genetic variation using eight microsatellite markers. The sample size per population was between 48 and 62 individuals. The genetic variation was higher within the isolated population than within populations in the center of the distribution area. No bottleneck effects were discovered during analyses that could have formatted the gene pool of this population. Balancing or directed selection toward preservation of specific alleles or promotion of heterozygous individuals could be an explanation for the unexpected high genetic diversity within this small and isolated population.

The green oak leaf roller (Tortrix viridana L.) is a major pest on oaks. The green oak leaf roller is one reason within a disease complex for the oak decline, and it leads to defoliation of oaks in spring. In Germany, Quercus robur L. is mainly affected. The partitioning of genetic variation within and among populations of forest pests is linked to their capacities for migration. And the capacity for migration is the basis for dispersal of the pest species to different host trees and host populations and, therefore, for further outbreak events. Thus, the within population spatial genetic structure (SGS) of T. viridana was investigated based on nuclear (AFLP) markers to analyse the dispersal capacity of this insect pest species at a very small spatial scale. A total of 401 individuals of the green oak leaf roller from four stands in North Rhine-Westphalia (Western Germany) were examined. In three of four populations, the AFLP markers revealed clearly SGS up to 40 m, which can be explained by the mating behaviour within this species.

An herbivorous insect, the green oak leaf roller ( Tortrix viridana ) and one of its host species, pedunculate oak ( Quercus robur ), were investigated for their genetic variation within and among populations on the basis of mitochondrial, chloroplast, and anonymous markers. Oaks and green oak leaf rollers from 10 oak stands in North Rhine-Westphalia (North-Western Germany) were examined. The genetic variation of pedunculate oaks is much lower within than among populations when assessed using chloroplast gene markers and higher among populations when assessed using anonymous markers. When using mitochondrial and AFLP markers, the genetic variation of the green oak leaf roller populations was higher within than among the populations, which suggests a high gene flow between the populations. Mantel tests on the gene diversities of oaks and the green oak leaf roller yielded a significant negative correlation for both marker types. To sum up, the reasons for the differences in the spatial patterns of the genetic variation of the host and herbivorous insect may be found in their different generation times, mechanisms and capacities for dispersal. The results for the green oak leaf roller revealed a higher migration rate than assumed before which has consequences for the prediction of the dynamics of future outbreak events.

Blowfly larvae found on human corpses are important for the estimation of the postmortem interval (PMI) and other questions of forensic relevance. Some of these species are difficult to differentiate morphologically, therefore a molecular method was elaborated for species identification. Specific fragments of the COI and COII region of the mitochondrial DNA (mtDNA) were amplified followed by digestion with different restriction enzymes. Using a 1.3 kb fragment, identification of Lucilia sericata, Calliphora vicina and Calliphora vomitoria was possible by digestion with only one restriction enzyme using either DraI or HinfI. Furthermore, we sequenced 349 bp (a part of the COI and COII regions) from the same three species and found 34 nucleotide distinctions between C. vicina and L. sericata, 30 between C. vomitoria and L. sericata and 15 between the two Calliphora species. These results aid in quick identification of species used for estimation of PMI.

The interaction between herbivorous insects and their host plants is a never-ending race related to evolutionary adaptation. Plants have developed an armament against herbivore attacks including indirect defences which besides others are comprised of volatile substances, as well as toxic secondary metabolites act directly against feeding herbivores. Insects, however, can rapidly evolve mechanisms to adapt to these compounds to prevent being harmed by them. Thus, herbivorous insects represent a fascinating feeding guild that are comprised of several arthropod groups, and especially the lepidopteran genera that feed on tree species. One of these lepidopteran species is the green oak leaf roller, Tortrix viridana L., a major pest on oaks throughout Europe. Its’ defoliating larvae use different species of the genus Quercus and cause severe damage to the oaks. Defoliation leads to decrease of wood formation and fructification, and to an increase of vulnerability to secondary pathogens (fungi, viruses and other insects). This tree-insect-system serve as a model system for a specialised herbivorous insect and its’ host plant from as well an ecological as a molecular point of view combined with modelling aspects.

The succession of insects is commonly used for estimation of the postmortem interval (PMI). In the warm season there are many insect species, which enable us to estimate the time of death, but in the cold season there are less species. For the estimation of a seasonal pattern, we examined 117 human corpses found in domestic environment during the year 2001. We found three typical ‘summer species’, active from May until October, three further species active from April until November. One blowfly species (Calliphora vicina) and the family of scuttle flies were active all over the year. These insects may be useful for PMI estimation in winter; however, further research concerning the developmental rate of scuttle flies is required. The distinct seasonal pattern of the early colonizing blowfly species allows to allocate the time of death to a particular time interval even in cases of long PMIs if empty puparia of these insects are found. q 2003 Elsevier Science Ireland Ltd. All rights reserved.

Background The defoliation of oaks is an urgent problem for forestry in Central Europe. During the last outbreak of the green oak leaf roller(Tortrix viridana) in 2003-2005, we observed fundamental differences in the defoliation level of individual Quercus robur trees in Germany. Some of the trees seem to be somehow “tolerant” (T oaks) against the insects grub while some seem to be conspicuously “susceptible” (S oaks). Within this study we aim to identify the underlying molecular and biochemical mechanisms in oaks responsible for the behavioural preference of T. viridana. By means of combined behavioural experiments and biochemical as well as molecular analysis of preformed and induced defence mechanisms in T and S oak phenotypes, we will identify the metabolic/chemical basis of the observed differences as prerequisite for the selection of candidate genes differentially expressed in tolerant and susceptible trees, respectively, after insects feeding.

Background The interaction between insect pests and their host plants is a never-ending race of evolutionary adaption. Plants have developed an armament against insect herbivore attacks, and attackers continuously learn how to address it. Using a combined transcriptomic and metabolomic approach, we investigated the molecular and biochemical differences between Quercus robur L. trees that resisted (defined as resistant oak type) or were susceptible (defined as susceptible oak type) to infestation by the major oak pest, Tortrix viridana L. Results Next generation RNA sequencing revealed hundreds of genes that exhibited constitutive and/or inducible differential expression in the resistant oak compared to the susceptible oak. Distinct differences were found in the transcript levels and the metabolic content with regard to tannins, flavonoids, and terpenoids, which are compounds involved in the defence against insect pests. The results of our transcriptomic and metabolomic analyses are in agreement with those of a previous study in which we showed that female moths prefer susceptible oaks due to their specific profile of herbivore-induced volatiles. These data therefore define two oak genotypes that clearly differ on the transcriptomic and metabolomic levels, as reflected by their specific defensive compound profiles. Conclusions We conclude that the resistant oak type seem to prefer a strategy of constitutive defence responses in contrast to more induced defence responses of the susceptible oaks triggered by feeding. These results pave the way for the development of biomarkers for an early determination of potentially green oak leaf roller-resistant genotypes in natural pedunculate oak populations in Europe.