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Many insects have evolved the ability to manipulate plant growth to generate extraordinary structures called galls, in which insect larva can develop while being sheltered and feeding on the plant. In particular, cynipid (Hymenoptera: Cynipidae) wasps have evolved to form morphologically complex galls and generate an astonishing array of gall shapes, colors, and sizes. However, the biochemical basis underlying these remarkable cellular and developmental transformations remains poorly understood. A key determinant in plant cellular development is cell wall deposition that dictates the physical form and physiological function of newly developing cells, tissues, and organs. However, it is unclear to what degree cell walls are restructured to initiate and support the formation of new gall tissue. Here, we characterize the molecular alterations underlying gall development using a combination of metabolomic, histological, and biochemical techniques to elucidate how valley oak (Quercus lobata) leaf cells are reprogrammed to form galls. Strikingly, gall development involves an exceptionally coordinated spatial deposition of lignin and xylan to form de novo gall vasculature. Our results highlight how cynipid wasps can radically change the metabolite profile and restructure the cell wall to enable the formation of galls, providing insights into the mechanism of gall induction and the extent to which plants can be entirely reprogrammed to form unique structures and organs.

A survey conducted in the 1920s, prior to the chestnut blight, indicated that chestnuts and oaks were codominant canopy species in White Oak Canyon, Shenandoah National Park, Virginia. A second survey in 1977 suggested that chestnuts were being replaced by tree species present before the blight, particularly oaks. In 2021, we resurveyed the 10 sites included in our 1977 survey and also recorded canopy and understory trees that grew above remnant chestnut sprouts. The canopy changed more substantially during the second interval (since 1977). Birch and maples were now more abundant. Hemlock declined, and oaks were less common in the canopy. In general, the trees considered as early to mid-successional have replaced oaks and hemlock. Chestnut sprouts have become much less common since 1977, presumably as repeated cycles of diebacks have weakened rootstocks. Those sites where chestnut sprouts have persisted until 2021 differed from neighboring sites without them. Chestnut sprouts were rare in sites with birch and hemlock; chestnut has persisted in locations with red oaks in the canopy and with few other understory competitors. This survey has been conducted over a longer time interval than previous studies that asked similar questions and our results suggest that changes to the forest composition following the loss of the American chestnut may be greater than previously recognized although the relative contribution of losing this codominant species is unclear.

Deciduous forests in northeastern North America are comprised of a mixture of ectomycorrhizal (EM) and arbuscular mycorrhizal (AM) trees. However, land use legacies and other factors have decreased EM and concomitantly increased AM tree dominance, potentially limiting forest ecosystem functioning. We investigated how scattered EM tree patches and soil inoculum from local EM tree‐dominated forests influence EM fungal colonisation, survival and growth of EM Tsuga canadensis, Pinus strobus and Quercus spp. tree seedlings in AM‐dominated secondary forests.Seedlings were planted next to dominant AM Acer and scattered EM Betula trees across three New York secondary forests. A subset of seedlings also received soil inoculum from local EM‐dominated forests. We monitored the survival and height growth of seedlings for 2 years and then measured seedling shoot biomass, assessed EM colonisation and identified EM fungi from seedling roots.All genera of seedlings planted near EM Betula had higher EM colonisation and fungal richness than those planted near AM Acer trees. Inoculation with EM forest soil increased EM colonisation and fungal richness of seedlings only near AM Acer, showing great effectiveness in areas lacking native EM fungi. Total EM fungal diversity on seedling roots was highest near EM Betula, which included numerous taxa usually associated with mature trees. In contrast, EM fungal communities near AM Acer were sparse and mostly dominated by relatively few taxa of spore‐bank fungi. Although seedling survival did not differ between treatments, soil inoculation and proximity to EM Betula increased second‐year height growth of Pinus and Tsuga while soil inoculation alone significantly enhanced shoot mass of Quercus seedlings.Synthesis. Agricultural land use legacies have resulted in expansive secondary forests dominated by AM trees. In these forests, establishment of EM tree seedlings outside existing EM tree patches may be hindered by a lack of EM fungi, but local soil inoculum from EM tree‐dominated forests can reintroduce native EM fungi into secondary forests lacking established EM trees. [ABSTRACT FROM AUTHOR]

The evolutionary processes that underlie variation in plant genome size have been much debated. Abiotic factors are thought to have played an important role, with negative and positive correlations between genome size and seasonal or stressful climatic conditions being reported in several systems. In turn, variation in genome size may influence plant traits which affect interactions with other organisms, such as herbivores. The mechanisms underlying evolutionary linkages between plant genome size and biotic and abiotic factors nonetheless remain poorly understod. To address this gap, we conducted phylogenetically controlled analyses testing for associations between genome size, climatic variables, plant traits (defenses and nutrients), and herbivory across 29 oak (Quercus) species. Genome size is significantly associated with both temperature and precipitation seasonality, whereby oak species growing in climates with lower and less variable temperatures but more variable rainfall had larger genomes. In addition, we found a negative association between genome size and leaf nutrient concentration (found to be the main predictor of herbivory), which in turn led to an indirect effect on herbivory. A follow‐up test suggested that the association between genome size and leaf nutrients influencing herbivory was mediated by variation in plant growth, whereby species with larger genomes have slower growth rates, which in turn are correlated with lower nutrients. Collectively, these findings reveal novel associations between plant genome size and biotic and abiotic factors that may influence life history evolution and ecological dynamics in this widespread tree genus. [ABSTRACT FROM AUTHOR]

Most oak savannas in the Midwestern United States have been lost to agriculture and habitat degradation. Because of their rarity and high plant and animal diversity, savannas are often a target for restoration, which frequently relies on the direct planting of oak seedlings to establish the necessary canopy. Returning fire to the system is critical to the herbaceous component, but with planted seedlings, managers risk damaging or killing trees if burning is introduced too soon. We studied the growth and physiological responses of three oak species (Quercus alba, Quercus macrocarpa, and Quercus velutina) to prescribed fire to determine impacts on planted trees. This study utilized two restored oak savanna units that were planted in 1995 and 1998, each with burned and unburned areas. We tracked trees ranging from 0.9 to 29.8 cm in diameter at breast height (DBH) to determine the size threshold above which top kill is unlikely and documented differences in leaf structure and extension growth between the burned and unburned areas. There was no mortality observed. Moreover, no trees larger than 4 cm DBH were top killed by the fire. Fire responses in leaf mass per unit area and chlorophyll content were small and inconsistent across species. However, all oak species grew more in burned areas than trees in adjacent unburned areas. Therefore, the addition of low‐intensity prescribed fire to an oak savanna planting may increase the growth rate of planted trees with minimal risk of mortality once trees have reached sufficient size. [ABSTRACT FROM AUTHOR]

Summary: Measurements of stable isotope ratios in organic compounds are widely used tools for plant ecophysiological studies. However, the complexity of the processes involved in shaping hydrogen isotope values (δ2H) in plant carbohydrates has limited its broader application.To investigate the underlying biochemical processes responsible for 2H fractionation among water, sugars, and cellulose in leaves, we studied the three main CO2 fixation pathways (C3, C4, and CAM) and their response to changes in temperature and vapor pressure deficit (VPD).We show significant differences in autotrophic 2H fractionation (εA) from water to sugar among the pathways and their response to changes in air temperature and VPD. The strong 2H depleting εA in C3 plants is likely driven by the photosynthetic H+ production within the thylakoids, a reaction that is spatially separated in C4 and strongly reduced in CAM plants, leading to the absence of 2H depletion in the latter two types. By contrast, we found that the heterotrophic 2H‐fractionation (εH) from sugar to cellulose was very similar among the three pathways and is likely driven by the plant's metabolism, rather than by isotopic exchange with leaf water.Our study offers new insights into the biochemical drivers of 2H fractionation in plant carbohydrates. [ABSTRACT FROM AUTHOR]

Anticipating the effects of global change on biodiversity has become a global challenge requiring new methods. Approaches like species distribution models have limitations which have fueled the development of joint species distribution models (JSDMs). However, JSDMs rely on systematic surveys community data, and no assessment has been made of their suitability with unstructured opportunistic databases data. We used hierarchical modeling of species communities (HMSC) to test JSDMs performance when using opportunistic databases. Using artificial data that mimic the limitations of such databases by subsampling complete co‐occurrence matrices (i.e. original data), we analysed how the completeness of opportunistic databases affects JSDMs regarding 1) the role of independent variables on species occurrence, 2) residual species co‐occurrence (as a proxy of biotic interactions) and 3) species distributions. Moreover, we illustrate how to evaluate completeness at the pixel level of real data with a study case of forest tree species in Europe, and evaluate the role of data completeness in model estimation. Our results with artificial data demonstrate that decreasing the completion percentage (the rate of original data presences represented in the subsampled matrices) increases false negatives and negative co‐occurrence probabilities, resulting in a loss of ecological information. However, HMSC tolerates different levels of degradation depending on the model aspect being considered. Models with 50% of missing data are valid for estimating species niches and distribution, but interaction matrices require databases with at least 75% of completion data. Furthermore, HMSC's predictions often resemble the original community data (without false negatives) even more than the subsampled data (with false negatives) in the training dataset. These findings were confirmed with the real study case. We conclude that opportunistic databases are a valuable resource for JSDMs, but require an analysis of data completeness for the target taxa in the study area at the spatial resolution of interest. [ABSTRACT FROM AUTHOR]

Oak bark, which is commonly used in the wood industry, has by-products often repurposed as fuel. Its extracts are rich in compounds with anticancer, antibacterial, antifungal, and anti-inflammatory properties. This study synthesized platinum nanoparticles (PtNPs) using aqueous extracts from Quercus dalechampii (QD), Q. frainetto (QF), and Q. petraea (QP). Key factors during nanoparticle formation included reaction time, metal ion concentration, pH, extract-to-metal ion ratio, and temperature. The PtNPs were characterized by dynamic light scattering, Fourier transform infrared spectroscopy, and transmission electron microscopy. The average diameters were 58.5 ± 7.6 nm for QD-PtNPs, 41.6 ± 5.4 nm for QF-PtNPs, and 41 ± 5.3 nm for QP-PtNPs. Antioxidant and antimicrobial activities were also analyzed. The QP-PtNPs had the highest DPPH (2,2-Diphenyl- 1-picrylhydrazyl), FRAP (Ferric Reducing Antioxidant Power), and CUPRAC (Cupric Reducing Antioxidant Capacity) free radical scavenging activities, while QD-PtNPs excelled in ABTS (2,2'-azinobis-(3- ethylbenzothiazoline-6-sulfonic acid)) scavenging. All PtNPs showed strong antimicrobial properties, particularly against Enterococcus faecalis, Escherichia coli, Candida krusei, and Candida auris. These findings suggest that Quercus-mediated PtNPs have significant potential for developing treatments against bacterial and fungal infections, with promising applications in medicine. [ABSTRACT FROM AUTHOR]

Urbanization and urban sprawl generally degrade and diminish wildlife habitat, threatening to extirpate local populations. However, certain synanthropic species (e.g., coyotes, white‐tailed deer, and squirrels) are able to persist in urban environments and may even occur at greater densities than they do in their natural habitats. Eastern fox squirrels (Sciurus niger) are large tree squirrels that are known to be present in greater densities within urban areas. To determine how landscape characteristics may affect fox squirrel presence, we conducted line‐transect surveys along sidewalks on the Texas A&M University—College Station campus to record presence of fox squirrels and nearest tree species. We calculated Jacobs' index of selectivity (D) for use of trees by fox squirrels along the transects. Squirrel density was calculated for all transects and modeled using linear regression with environmental (e.g., tree density) and survey (e.g., transect distance) variables. Fox squirrels preferred only a small number of the available tree species, primarily Quercus and Ulmus species. Observed fox squirrel density significantly increased with time of day, temperature, density of oaks (Quercus spp.), and density of all trees, and decreased with distance and area of the transect. These results suggest that even when urban areas contain suitable habitat, use of urban environments by wildlife is still highly selective and dependent on specific habitat requirements. [ABSTRACT FROM AUTHOR]

Eurasian Jays (Garrulus glandarius) typically store seeds on the ground in shallow caches, promoting tree recruitment. However, speculation exists that Eurasian Jays occasionally store a portion of seeds in microhabitats unsuitable for proper germination. Here, we report that unexpected caching sites in Eurasian Jays can be much more widespread than previously considered and despite their accidental character it seems to be a durable aspect of Eurasian Jay's hoarding behavior. Out of 259 removed acorns of Pedunculate Oak (Quercus robur), we localized 31 consumed and 222 stored acorns. Six experimental acorns (3% of stored acorns) were found stored by jays in unexpected caching sites: (i) above the ground on individuals of Scots Pine (Pinus sylvestris), (ii) inside the woody stems of Reynoutria sp. individuals, (iii) in a rotten trunk, and (iv) among ruin debris. Our findings suggest the need to revise our understanding of so-called unexpected caching in Eurasian Jays. This highlights a previously overlooked aspect of oak-jay interactions, offering a valuable piece to the puzzle. [ABSTRACT FROM AUTHOR]

Chloroplast (cp) genome sequences have been extensively used for phylogenetic and evolutionary analyses, as many have been sequenced in recent years. Identification of Quercus is challenging because many species overlap phenotypically owing to interspecific hybridization, introgression, and incomplete lineage sorting. Therefore, we wanted to gain a better understanding of this genus at the level of the maternally inherited chloroplast genome. Here, we sequenced, assembled, and annotated the cp genomes of the threatened Quercus marlipoensis (160,995 bp) and Q. kingiana (161,167 bp), and mined these genomes for repeat sequences and codon usage bias. Comparative genomic analyses, phylogenomics, and selection pressure analysis were also performed in these two threatened species along with other species of Quercus. We found that the guanine and cytosine content of the two cp genomes were similar. All 131 annotated genes, including 86 protein-coding genes, 37 transfer RNA genes, and 8 ribosomal RNA genes, had the same order in the two species. A strong A/T bias was detected in the base composition of simple sequence repeats. Among the 59 synonymous codons, the codon usage pattern of the cp genomes in these two species was more inclined toward the A/U ending. Comparative genomic analyses indicated that the cp genomes of Quercus section Ilex are highly conserved. We detected eight highly variable regions that could be used as molecular markers for species identification. The cp genome structure was consistent and different within and among the sections of Quercus. The phylogenetic analysis showed that section Ilex was not monophyletic and was divided into two groups, which were respectively nested with section Cerris and section Cyclobalanopsis. The two threatened species sequenced in this study were grouped into the section Cyclobalanopsis. In conclusion, the analyses of cp genomes of Q. marlipoensis and Q. kingiana promote further study of the taxonomy, phylogeny and evolution of these two threatened species and Quercus. [ABSTRACT FROM AUTHOR]

Quercus subsect. Campylolepides contains three species: Q. acutissima, Q. variabilis and Q. chenii, which is the East Asian clade of Quercus section Cerris. Species formation and phylogeography of whole subsection or species within the subsection have been studied in detail. It has been also found that section Cerris had an ancient gene introgression with section Ilex, which led to the plastid capture. However, the specific evolutionary history of plastids in subsect. Campylolepides and section Ilex remains unclear. Our study performed low-coverage whole genome sequencing on 15 samples from section Ilex and integrated previously published data from subsect. Campylolepides and its relatives, resulting in a total of 325 resequencing data, of which 276 individuals were from three subsect. Campylolepides species and 19 populations. We assembled 325 plastids to perform phylogeographic analysis. The results were as follows: (1) There were shared haplotypes among three species of subsect. Campylolepides, but the plastid haplotypes of the entire subsect. Campylolepides form a monophyletic branch nested within section Ilex species which are distributed from central China to Liangshan, Sichuan. (2) A relictual haplotype of subsect. Campylolepides from the Liaodong Peninsula clustered with Q. pseudosetulosa, a specie of the section Ilex. (3) Both plastid capture events occurred in the middle Miocene, after which no plastid capture occurred between subsect. Campylolepides and section Ilex. It is hypothesized that subsect. Campylolepides and section Ilex have formed almost complete reproductive isolation. The study demonstrates that section Ilex and subsect. Campylolepides have undergone ancient plastid capture events in their evolution history, ultimately lead to the gradual formation of relatively independent evolutionary paths. [ABSTRACT FROM AUTHOR]

Adaptive differentiation of traits and underlying loci can occur at a small geographical scale if natural selection is stronger than countervailing gene flow and drift. We investigated this hypothesis using coupled quantitative genetic and genomic approaches for a wind‐pollinated tree species, Quercus rubra, along the steep, narrow gradient of the Lake Superior coast that encompasses four USDA Hardiness Zones within 100 km. For the quantitative genetic component of this study, we examined phenotypic differentiation among eight populations in a common garden, measuring seed mass, germination, height, stem diameter, leaf number, specific leaf area and survival. For the genomic component, we quantified genetic differentiation for 26 populations from the same region using RAD‐seq. Because hybridisation with Quercus ellipsoidalis occurs in other parts of the species' range, we included two populations of this congener for comparison. In the common garden study, we found a strong signal of population differentiation that was significantly associated with at least one climate factor for nine of 10 measured traits. In contrast, we found no evidence of genomic differentiation among populations based on FST or any other measures. However, both distance‐based and genotype–environment association analyses identified loci showing the signature of selection, with one locus in common across five analyses. This locus was associated with the minimum temperature of the coldest month, a factor that defines the climate zones and was also significant in the common garden analyses. In addition, we documented introgression from Q. ellipsoidalis into Q. rubra, with rates of introgression correlated with the climate gradient. In sum, this study reveals signatures of selection at the quantitative trait and genomic level consistent with climate adaptation, a pattern that is more often documented at a much broader geographical scale, especially in long‐lived wind‐pollinated species. [ABSTRACT FROM AUTHOR]

Abstract Key message We test the potential benefits of planting 2-year vs. 1-year-old seedlings to restore Mediterranean oak-dominated systems. Planting 2-year-old Quercus suber L. seedlings is recommended for improved survival and resilience against wild boar (Sus scrofa L.) and drought in dry sandy soils. The removal of acorns in seedlings did not apparently influence leaf biochemical traits and could reduce wild boar damage, particularly in 1-year-old seedlings. Context In the face of anthropogenic global change, Mediterranean oak-dominated ecosystems confront increased biotic (ungulate herbivory) and abiotic (drought) stressors, compromising forest regeneration. Restoration measures are imperative to address this scenario. Aims This study assesses the impact of different mitigation measures on the survival and biochemical traits of two oak species. Methods We planted Quercus ilex L. and Q. suber L. seedlings in Cabañeros and Doñana National Parks (Spain), subjecting them to three treatments: cotyledon/acorn removal, seedling age (1- vs. 2-year-old), and herbivore protection (fenced vs. non-fenced). Results Wild boar (Sus scrofa L.) damage peaked in winter and early spring, while drought prevailed from late spring to fall. In sandy soils, wild boar uprooted 1-year-old more often than 2-years-old seedlings (40% vs. 18%). One-year-old seedlings without acorns showed higher survival rates against wild boar only in sandy soils. The removal of acorns in seedlings did not influence plant biochemical traits. Conclusions Planting 2-year-old seedlings in sandy soils may mitigate wild boar damage and improve drought resilience. Seedling age seems more important than acorn removal against biotic and abiotic stressors although acorn removal could reduce wild boar damage in 1-year-old seedlings. Our results underscore the importance of considering multiple stressors in oak restoration strategies.

Abstract Chloroplast (cp) genome sequences have been extensively used for phylogenetic and evolutionary analyses, as many have been sequenced in recent years. Identification of Quercus is challenging because many species overlap phenotypically owing to interspecific hybridization, introgression, and incomplete lineage sorting. Therefore, we wanted to gain a better understanding of this genus at the level of the maternally inherited chloroplast genome. Here, we sequenced, assembled, and annotated the cp genomes of the threatened Quercus marlipoensis (160,995 bp) and Q. kingiana (161,167 bp), and mined these genomes for repeat sequences and codon usage bias. Comparative genomic analyses, phylogenomics, and selection pressure analysis were also performed in these two threatened species along with other species of Quercus. We found that the guanine and cytosine content of the two cp genomes were similar. All 131 annotated genes, including 86 protein-coding genes, 37 transfer RNA genes, and 8 ribosomal RNA genes, had the same order in the two species. A strong A/T bias was detected in the base composition of simple sequence repeats. Among the 59 synonymous codons, the codon usage pattern of the cp genomes in these two species was more inclined toward the A/U ending. Comparative genomic analyses indicated that the cp genomes of Quercus section Ilex are highly conserved. We detected eight highly variable regions that could be used as molecular markers for species identification. The cp genome structure was consistent and different within and among the sections of Quercus. The phylogenetic analysis showed that section Ilex was not monophyletic and was divided into two groups, which were respectively nested with section Cerris and section Cyclobalanopsis. The two threatened species sequenced in this study were grouped into the section Cyclobalanopsis. In conclusion, the analyses of cp genomes of Q. marlipoensis and Q. kingiana promote further study of the taxonomy, phylogeny and evolution of these two threatened species and Quercus.

Abstract This study aimed to investigate the performance and factors affecting the species classification of convolutional neural network (CNN) architecture using whole-part and earlywood-part cross-sectional datasets of six Korean Quercus species. The accuracy of species classification for each condition was analyzed using the datasets, data augmentation, and optimizers—stochastic gradient descent (SGD), adaptive moment estimation (Adam), and root mean square propagation (RMSProp)—based on a CNN architecture with three to four convolutional layers. The model trained with the augmented dataset yielded significantly superior results in terms of classification accuracy compared to the model trained with the non-augmented dataset. The augmented dataset was the only factor affecting classification accuracy in the final five epochs. In contrast, four factors in the entire epoch, such as the Adam and SGD optimizers and the earlywood-part and whole-part datasets, affected species classification. The arrangement of earlywood vessels, broad rays, and axial parenchyma was identified as a major influential factor in the CNN species classification using gradient-weighted class activation mapping (Grad-CAM) analysis. The augmented whole-part dataset with the Adam optimizer achieved the highest classification accuracy of 85.7% during the final five epochs of the test phase.

Abstract Uncontrolled terpenoid emissions from forest trees in Japan may have contributed to high O3 concentrations observed in urban and suburban areas. To estimate ozone formation via a series of reactions between NO x and terpenoids using atmospheric chemistry models, it is important to produce terpenoid emission inventories by collecting all reported emission data for the major tree species in Japan and examining their reliability. In this review, we first describe three different plant terpenoid emission types, i.e., isoprene-emitting type, monoterpene-emitting type with storage tissues and organs, and monoterpene-emitting type without storage tissues and organs. Second, we describe various methods for measuring plant terpenoid emissions, including a recently developed simplified method, and explain their reliability. We emphasized that applicable measurement methods depend on the terpenoid emission types. Data obtained using static chamber methods should not be considered because they have the highest uncertainty resulting from normal chamber materials that are not specific to terpenoid measurements and lack humidity control. Finally, we show the absolute values of the collected emission rates and describe their variability. The deciduous oak species, Quercus serrata and Quercus mongolica var. crispula, and bamboo species, Phyllostachys pubescens and Phyllostachys bambusoides, are strong isoprene emitters. Among the monoterpene emitters, four evergreen broadleaf trees, including three Quercus species, had the highest basal emission rate (BER). The monoterpene storage type conifers Larix kaempferi and Pinus densiflora have relatively lower BERs. Emission data are not available for Castanopsis cuspidata, and seasonal changes in emission rates have not been reported for several major tree species in the top 20 rankings. Within species, the reported emission rates of some tree species differed by threefold. These differences may be attributed to the reliability of the measurement and analytical systems, tree age, leaf morphology, environmental conditions, and genetic diversity. We emphasize the need for reliable measurements to achieve a more precise terpenoid emission inventory for major tree species in Japan.

This study aimed to investigate the performance and factors affecting the species classification of convolutional neural network (CNN) architecture using whole-part and earlywood-part cross-sectional datasets of six Korean Quercus species. The accuracy of species classification for each condition was analyzed using the datasets, data augmentation, and optimizers—stochastic gradient descent (SGD), adaptive moment estimation (Adam), and root mean square propagation (RMSProp)—based on a CNN architecture with three to four convolutional layers. The model trained with the augmented dataset yielded significantly superior results in terms of classification accuracy compared to the model trained with the non-augmented dataset. The augmented dataset was the only factor affecting classification accuracy in the final five epochs. In contrast, four factors in the entire epoch, such as the Adam and SGD optimizers and the earlywood-part and whole-part datasets, affected species classification. The arrangement of earlywood vessels, broad rays, and axial parenchyma was identified as a major influential factor in the CNN species classification using gradient-weighted class activation mapping (Grad-CAM) analysis. The augmented whole-part dataset with the Adam optimizer achieved the highest classification accuracy of 85.7% during the final five epochs of the test phase. [ABSTRACT FROM AUTHOR]

Resolving evolutionary relationships among closely related species with interspecific gene flow is challenging. Genome‐scale data provide opportunities to clarify complex evolutionary relationships in closely related species and to observe variations in species relationships across the genomes of such species. The Himalayan–Hengduan subalpine oaks have a nearly completely sympatric distribution in southwest China and probably constitute a syngameon. In this study, we mapped resequencing data from different species in this group to the Quercus aquifolioides reference genome to obtain a high‐quality filtered single nucleotide polymorphism (SNP) dataset. We also assembled their plastomes. We reconstructed their phylogenetic relationships, explored the level and pattern of introgression among these species and investigated gene tree variation in the genomes of these species using sliding windows. The same or closely related plastomes were found to be shared extensively among different species within a specific geographical area. Phylogenomic analyses of genome‐wide SNP data found that most oaks in the Himalayan–Hengduan subalpine clade showed genetic coherence, but several species were found to be connected by introgression. The gene trees obtained using sliding windows showed that the phylogenetic relationships in the genomes of oaks are highly heterogeneous and therefore highly obscured. Our study found that all the oaks of the Himalayan–Hengduan subalpine clade from southwest China form a syngameon. The obscured phylogenetic relationships observed empirically across the genome are best explained by interspecific gene flow in conjunction with incomplete lineage sorting. [ABSTRACT FROM AUTHOR]

Acorn size is of great importance, both ecologically and economically. However, the long lifespan is an obstacle to improvement in breeding. Keumsura1ho is a recently bred cultivar of oak (Quercus acutissima Carruth) selected after eight years of selection due to its larger acorns and higher weight compared to the control. In the present study, we investigated the transcriptional mechanisms underlying the outstanding morphological characteristics of Keumsura1ho. For this purpose, one- and two-year-old acorns from the control and Keumsura1ho groups were used for comparative transcriptome analyses of their seeds. Among morphological characteristics, the Keumsura1ho seeds were 18.3% longer than those of the control. Seed width and depth were 33.9% greater than those of the control. In the transcriptome analysis, genes related to seed size were further enriched, with biennial Keumsura1ho showing higher enrichment in comparison to control genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the upregulated genes of the two-year-old Keumsura1ho seeds showed higher enrichment in phenylpropanoid metabolism compared to the control, with OMT1 and PRXs exhibiting high expression levels. This pathway has a significant impact on seed coat lignification and size in Keumsura1ho. The results of this study will benefit the development of breeding techniques by identifying marker genes for seed size. [ABSTRACT FROM AUTHOR]

Increasing temperatures, prolonged drought, the increased severity and intensity of storms, and other effects of climate change are being felt globally, and long-lived forest tree species may struggle in their current ranges. Oaks (Quercus spp.) have evolved a range of adaptations to dry and hot conditions and are believed to be a "climate change winner" by increasing their suitable habitat. However, a mixture of life history traits and increasing susceptibility to herbivores and xylovores as well as secondary pathogen infections still put oaks at risk of decline. Oak species found in the Midwestern, Great Lakes, and Northeastern United States and Canada are important keystone species with high ecological and economical importance. They are also vulnerable to existing, new, and emerging threats that have the potential to cause mortality across entire stands quickly. Current examples of insect threats include the Lymantria dispar (spongy moth), Agrilus bilineatus (twolined chestnut borer), and Nitidulidae (sap beetles) as disease vectors. Examples of emerging insects of concern include Cynipidae (oak gall wasps) and Enaphalodes rufulus (red oak borer). This study describes these insects, explains their mechanisms of action and the effects on oaks, and explores mitigation strategies for each. [ABSTRACT FROM AUTHOR]

The bioactive properties of underutilized corks such as Quercus cerris cork and planted Quercus suber cork in the Eastern Mediterranean are not well-known but are crucial in developing lignocellulosic biorefineries. To assess their biological potential, hydroethanolic cork extracts of Quercus cerris and Quercus suber were analyzed for phenolic composition, antioxidant, antiproliferative, antimicrobial activities, and hepatoxicity, as well as NO-production inhibition. Here, we show that a mild hydroethanolic extraction of Q. cerris and Q. suber corks yielded 3% phenolic extracts. The phenolic composition was similar in both cork extracts, with phenolic acids and ellagitannins as the primary compounds. The bioactivity of hydroethanolic cork extracts from Q. cerris surpassed that of Q. suber and showed effectiveness against all cancer cell lines tested. This first comprehensive study on the bioactivities of different corks involves detailed characterizations of phenolic compounds of cork extracts using UPLC-DAD-ESI/MSn, evaluations of the antioxidant properties with TBARS and OxHLIA methods, evaluation of antiproliferative activity against gastric (AGS), lung (NCI-H460), colon (CaCo2), and breast cancer (MCF7) cell lines, as well as evaluations of hepatotoxicity and NO-production inhibition. The findings from this study will help bolster the potential of using underutilized cork-rich barks as a valuable resource in bark-based biorefineries. [ABSTRACT FROM AUTHOR]

Uncontrolled terpenoid emissions from forest trees in Japan may have contributed to high O3 concentrations observed in urban and suburban areas. To estimate ozone formation via a series of reactions between NOx and terpenoids using atmospheric chemistry models, it is important to produce terpenoid emission inventories by collecting all reported emission data for the major tree species in Japan and examining their reliability. In this review, we first describe three different plant terpenoid emission types, i.e., isoprene-emitting type, monoterpene-emitting type with storage tissues and organs, and monoterpene-emitting type without storage tissues and organs. Second, we describe various methods for measuring plant terpenoid emissions, including a recently developed simplified method, and explain their reliability. We emphasized that applicable measurement methods depend on the terpenoid emission types. Data obtained using static chamber methods should not be considered because they have the highest uncertainty resulting from normal chamber materials that are not specific to terpenoid measurements and lack humidity control. Finally, we show the absolute values of the collected emission rates and describe their variability. The deciduous oak species, Quercus serrata and Quercus mongolica var. crispula, and bamboo species, Phyllostachys pubescens and Phyllostachys bambusoides, are strong isoprene emitters. Among the monoterpene emitters, four evergreen broadleaf trees, including three Quercus species, had the highest basal emission rate (BER). The monoterpene storage type conifers Larix kaempferi and Pinus densiflora have relatively lower BERs. Emission data are not available for Castanopsis cuspidata, and seasonal changes in emission rates have not been reported for several major tree species in the top 20 rankings. Within species, the reported emission rates of some tree species differed by threefold. These differences may be attributed to the reliability of the measurement and analytical systems, tree age, leaf morphology, environmental conditions, and genetic diversity. We emphasize the need for reliable measurements to achieve a more precise terpenoid emission inventory for major tree species in Japan. [ABSTRACT FROM AUTHOR]

A key question in insect community ecology is whether parasitoid assemblages are structured by the food plants of their herbivore hosts. Tritrophic communities centred on oak‐feeding cynipid gallwasps are one of the best‐studied tritrophic insect communities. Previous work suggests that host plant identity is a much stronger predictor of oak–cynipid interactions than of cynipid–parasitoid interactions. However, these relationships have not been formally quantified. We reason that the potential for ‘bottom‐up’ effects should increase with host plant phylogenetic diversity. We, therefore, generated quantified interaction network data for previously unstudied tritrophic cynipid communities in Sichuan, China, where, in addition to Quercus, cynipid host plants include Castanea, Castanopsis and Lithocarpus. We characterise these communities taxonomically and compare the extent to which host plant taxonomy predicts plant–herbivore and plant–parasitoid associations. We sampled 42,620 cynipid galls of 176 morphotypes from 23 host plant species, yielding over 4500 specimens of 64 parasitoid morphospecies. Many parasitoids were identifiable to chalcidoid taxa present in other Holarctic oak cynipid communities, with the addition of Cynipencyrtus (Cynipencyrtidae). As elsewhere, Sichuan parasitoid assemblages were dominated by generalists. Gallwasp–plant interaction networks were significantly more modular than parasitoid–plant association networks. Gallwasps were significantly more specialised to host plants (i.e. had higher mean d' values) than parasitoids. Parasitoid assemblages nevertheless showed significant plant‐associated beta diversity, with a dominant turnover component. We summarise parallels between our study and other Fagaceae‐associated cynipid communities and discuss our findings in light of the processes thought to structure tritrophic interactions centred on endophytic insect herbivores. [ABSTRACT FROM AUTHOR]

Discovery of a new species from the genera Sycophila Walker, 1871 (Hymenoptera, Eurytomidae): Sycophila gatesi Pérez-Alférez & Pujade-Villar n. sp., on the finding of males and females emerged from galls of Cynipidae (Hymenoptera) on Quercus in Mexico. The diagnostic morphological features of the adults are pictured and discussed. [ABSTRACT FROM AUTHOR]

Subtropical evergreen broad‐leaved forest (EBLF) is the predominant vegetation type in eastern China. However, the majority of the region it covers in eastern China was an arid area during the Paleogene. The temporal history and essential factors involved in the evolution of subtropical EBLFs in eastern China remain enigmatic. Here we report on the niche evolution of Quercus section Cyclobalanopsis, which appeared in south China and Japan during the Eocene and became a dominant component of subtropical EBLFs since the Miocene in eastern Asia, using integrative analysis of occurrences, climate data and a dated phylogeny of 35 species in Cyclobalanopsis. Species within clades Cyclobalanoides, Lamellosa, and Helferiana mainly exist in the Himalaya–Hengduan region, adapting to a plateau climate, while species within the other clades mainly live in eastern China under the control of the East Asian monsoon. Reconstructed history showed that significant divergence of climatic tolerance in Cyclobalanopsis began around 19 million years ago (Ma) in the early Miocene. Simultaneously, disparities in precipitation of wettest/warmest quarter and annual precipitation were markedly enhanced in Cyclobalanopsis, especially in the recent eastern clades. During the Miocene, the marked radiation of Cyclobalanopsis and many other dominant taxa of subtropical EBLFs strongly suggest the rapid formation and expansion of subtropical EBLFs in eastern China. Our research highlights that the intensification of the East Asian monsoon and subsequent occupation of new niches by the ancient clades already present in the south may have jointly promoted the formation of subtropical EBLFs in eastern China since the early Miocene. [ABSTRACT FROM AUTHOR]

Quercus species are utilized for their durable wood, providing sustenance for wildlife, conserving biodiversity, and contributing ecological, medicinal, and esthetic benefits to ecosystems and landscapes. In this study, we aimed to use the bark of three Quercus species (Q. dalechampi, Q. fraineto, and Q. petraea) for the synthesis of silver and gold nanoparticles (AgNPs and AuNPs). The aqueous extracts from the bark of Quercus sp. acted both as reducing and stabilizing agent, facilitating the rapid synthesis of AuNPs (AuQD, AuQF, and AuQP) and AgNPs (AgQD, AgQF, and AgQP). The obtained nanoparticles were characterized using UV-vis spectroscopy, TEM, DLS, and FTIR. Characterizations revealed that the nanoparticles exhibited a variety of shapes, such as polygonal, triangular, and spherical forms, with sizes ranging between 14 and 24 nm for AuNPs and 45–70 nm for AgNPs. The total phenolic content was assessed through spectroscopic methods, while several individual phenolic compounds were identified and quantified using UPLC-PDA. Furthermore, we assessed the antioxidant, antibacterial, and antifungal capacities of AuNPs, AgNPs, and raw extracts. The highest antioxidant activity was observed for raw extracts, followed by AgNPs and AuNPs, while the most potent antibacterial and antifungal activity was observed in AgQP. Moreover, cytotoxicity was examined in a human keratinocyte cell line (HaCaT). The results indicated no cytotoxic effects for AuNPs, while AgNPs and the raw extracts exhibited cytotoxic effects after 48 h of incubation. This research underscores the multifaceted utility of Quercus bark extracts in the green synthesis of metallic nanoparticles and their subsequent bioactivity assessment, suggesting promising perspectives for their application in various fields while urging cautious consideration of their cytotoxic implications. [ABSTRACT FROM AUTHOR]

The ongoing climatic change, together with atmospheric pollution, influences the timing, duration and intensity of pollen seasons of some allergenic plant taxa. To study these influences, we correlated the trends in the pollen season characteristics of both woody (Fraxinus, Quercus) and herbaceous (Ambrosia) taxa from two pollen monitoring stations in Slovakia with the trends in meteorological factors and air pollutants during the last two decades. In woody species, the increased temperature during the formation of flower buds in summer and autumn led to an earlier onset and intensification of next year's pollen season, especially in Quercus. The increase of relative air humidity and precipitation during this time also had a positive influence on the intensity of the pollen season of trees. The pollen season of the invasive herbaceous species Ambrosia artemisiifolia was prolonged by increased temperature and humidity during the summer and autumn of the same year, which extended the blooming period and delayed the end of the pollen season. From the studied air pollutants, only three were found to correlate with the intensity of the pollen season of the studied taxa, CO − positively and SO2 and NO2 − negatively. It is important to study these long-term trends since they not only give us valuable insight into the response of plants to changing conditions but also enable the prognosis of the exacerbations of pollen-related allergenic diseases. [ABSTRACT FROM AUTHOR]

Flooding stress is an increasingly serious problem in wetlands, often affecting large areas of crops and timber production areas. The current study aimed to explore the species differences in responses to flooding stress between Q. nuttallii and Q. palustris in an outdoor environment. All the tested plants survived after a 60-day flooding treatment that left 5 cm of water above the soil surface. This suggests that the two species are flood-tolerant, so they can be applied in the construction of riparian protection forests and wetland restoration. Compared with control conditions, flooding treatment significantly decreased seedling height and diameter and the Pn, Gs, Tr, Fv/Fm, ABS/CSm, TR0/CSm, ET0/CSm, RE0/CSm, IAA, and GA3 content and significantly increased the content of MDA, H2O2, soluble sugars, SOD, POD, ADH, ABA, and JA. Under control conditions, Q. nuttallii showed significantly greater growth and photosynthetic capability than Q. palustris. In contrast, Q. palustris exhibited less inhibition of growth and photosynthesis, oxidative stress levels, and antioxidant enzyme activities than Q. nuttallii under flooding conditions. The findings indicate that Q. palustris has better defense mechanisms against the damage caused by flooding stress than Q. nuttallii. Q. nuttallii was more sensitive and responsive to flooding than Q. palustris. [ABSTRACT FROM AUTHOR]

Since the discovery of the Newport Medieval Ship in 2002, many studies have tried to establish a chronology for its construction and subsequent abandonment. Whilst conventional ring-width dendrochronology has been able to identify the provenance and provide a terminus post quem for the ship, until now a felling date for timbers associated with the original construction of the vessel has proved elusive. This study reports results from the application of stable isotope dendrochronology to date timbers from the ship. Using a combination of dendrochronologically-dated timbers and stable oxygen isotopic data from dated and undated samples, we can provide an independent verification of the ring-width dendrochronology and to return the first felling dates for an assemblage of the ship's framing timbers. Our results indicate that the ship was likely constructed shortly after the winter of AD 1457/8 with an operational lifetime of less than a decade. The study highlights the potential for the use of stable isotope dendrochronology for the precise, absolute dating of archaeological ship remains where ring-width dendrochronology alone has not proved effective. [ABSTRACT FROM AUTHOR]

Plantations of exotic trees were proposed as an alternative to restore native forests in degraded lands, because they can attract seed dispersers and modulate the microclimate beneath their canopies. However, the large-scale introduction of exotic tree plantations can negatively affect native species by high competitiveness for soil resources and light, while they can also release allelopathic compounds that inhibit the germination and growth of other plants. In this study, we tested the suitability of Eucalyptus camaldulensis plantations to assist the restoration of degraded lands in central Mexico, which were originally covered with oak forests. For this, we sampled soil seed banks within forest remnants and plantations, which showed that the animal-mediated dispersal of oak propagules from forests inwards plantations is reduced. Additionally, we conducted germination trials that evidenced that the leaves of Eucalyptus trees contain allelopathic compounds that inhibit the germination of oaks seeds, also showing that these compounds accumulate in the soil of plantations. We finally conducted field experiments in which soil form forests and plantations were translocated between these two habitats, and acorns were sowed on both soil types. These field experiments revealed that, besides the accumulation of allelopathic compounds in soils of plantations, oak recruitment in these habitats is also impaired by unfavorable microclimatic conditions. Therefore, we conclude that Eucalyptus plantations are not promoting the recovery of native oak forests in central Mexico and, instead, alternative ecological restoration methods should be applied for reaching this aim. [ABSTRACT FROM AUTHOR]

Macrolichen diversity and community composition were determined for an area of high botanical interest in the Coast Ranges of Northern California – the Horse Mountain Botanical Area (HMBA) in Six Rivers National Forest. The Coast Ranges have been suggested to have high lichen diversity, yet detailed site-specific macrolichen surveys are lacking for the area. The HMBA is characterized by the presence of ultramafic (serpentine) soils, contributing to its diverse assemblage of conifers. Here we present comprehensive data on macrolichens of the HMBA integrated with environmental variables at the landscape level. Twenty 0.4 ha sampling plots were positioned across the varying habitats of the HMBA and macrolichens were intensively sampled from all substrata. Out of 888 total collections, 119 macrolichen species in 52 genera were identified, 63 species were sequenced for the mycobiont internal transcribed spacer (ITS) region, and all species were vouchered. Microenvironmental influences on lichen community composition were ordinated with nonmetric multidimensional scaling (NMS). Within-plot measured environmental variables with strongest correlations to ordination Axis 1 were 1) total tree basal area, 2) proportion of conifer basal area relative to hardwoods, and 3) distance between plot center and nearest stream. Distinct macrolichen communities were found in plots containing primarily conifers versus mixed hardwood-conifer plots. All plots contained both nitrogen-fixing and pendulous forage macrolichens; in each of the three hardwood-dominated plots, nitrogen-fixing lichens composed nearly a third of the species total. When epiphytic macrolichen species richness and dominance within the HMBA were compared to data from other regional forests, the HMBA showed comparable community composition but averaged 39% higher species richness. Results from this study can help inform management of the HMBA as well as future taxonomic and ecological research on regional macrolichens. [ABSTRACT FROM AUTHOR]

Tree growth is a key mechanism driving carbon sequestration in forest ecosystems. Environmental conditions are important regulators of tree growth that can vary considerably between nearby urban and rural forests. For example, trees growing in cities often experience hotter and drier conditions than their rural counterparts while also being exposed to higher levels of light, pollution, and nutrient inputs. However, the extent to which these intrinsic differences in the growing conditions of trees in urban versus rural forests influence tree growth response to climate is not well known. In this study, we tested for differences in the climate sensitivity of tree growth between urban and rural forests along a latitudinal transect in the eastern United States that included Boston, Massachusetts, New York City, New York, and Baltimore, Maryland. Using dendrochronology analyses of tree cores from 55 white oak trees (Quercus alba), 55 red maple trees (Acer rubrum), and 41 red oak trees (Quercus rubra) we investigated the impacts of heat stress and water stress on the radial growth of individual trees. Across our three‐city study, we found that tree growth was more closely correlated with climate stress in the cooler climate cities of Boston and New York than in Baltimore. Furthermore, heat stress was a significant hindrance to tree growth in higher latitudes while the impacts of water stress appeared to be more evenly distributed across latitudes. We also found that the growth of oak trees, but not red maple trees, in the urban sites of Boston and New York City was more adversely impacted by heat stress than their rural counterparts, but we did not see these urban–rural differences in Maryland. Trees provide a wide range of important ecosystem services and increasing tree canopy cover was typically an important component of urban sustainability strategies. In light of our findings that urbanization can influence how tree growth responds to a warming climate, we suggest that municipalities consider these interactions when developing their tree‐planting palettes and when estimating the capacity of urban forests to contribute to broader sustainability goals in the future. [ABSTRACT FROM AUTHOR]

This study aimed to point out the possible use of oak leaves (Q. petraea) in the production of fermented alcoholic beverages. Parameters such as antioxidant capacity, total phenolic content, phenolics and sugars were determined using spectrophotometric and chromatographic methods. pH values were also determined, and in the final product with a fermentation length of 85 days, the alcohol content was determined and sensory analysis performed. The antioxidant capacity of the beverage was lower compared to the infusions before fermentation, and its highest values were recorded in the leaf samples, in which the highest values of phenolic compounds and the total phenolic content were also recorded. A decrease in the content of total phenolics was recorded with the increasing length of fermentation in beverage samples. However, the fermentation process had a positive effect on the contents of some phenolic substances such as catechin, gallic acid and gallocatechin. Sensory analysis showed a higher acceptability of the fermented beverage without the addition of orange, which could be caused by the higher sugar content in these samples. Oak leaves therefore represent a suitable raw material for the production of a fermented alcoholic beverage, without the need to enrich the taste with other ingredients. [ABSTRACT FROM AUTHOR]

To preserve biodiversity and maintain ecosystem services provided by trees in the course of climate change, it is essential to consider challenging tree species, which are less studied primarily due to a lack of investment compared to commercial species. Species of the genus Quercus present an interesting case because of their economic and ecological importance, and their syngameon biology. As a model for exploring ecological diversification, and with recent advances in forest genomics, knowledge, data, and genomic resources for oak have accumulated and are summarized in this review to foster oaks as potential candidate species for future reforestation programs in Canadian natural, peri-urban, and urban ecosystems. We summarize the state of current genomic research in oak and the accompanying opportunities genomics can provide to achieve the potential of oak silviculture in Canada. Further, we highlight the socio-economic benefits of planting oaks and genomic tools for the development of a traceability system along the value chain. Finally, we discuss some of the remaining challenges to successfully integrate oaks into different forest management programs. In light of their increased drought resistance, oak species exhibit a strong potential as viable choices for future forests, resilient agricultural landscapes, and urban areas. By leveraging the progress made in oak genomics and the new applications that have been developed for commercial species, we can foster the successful management of oak genetic resources for the production of suitable seedlings, thereby aiding Canada in its ambitious pursuit of planting two billion trees to combat climate change. [ABSTRACT FROM AUTHOR]

Quercus species are the most frequent autochthonous arboreal taxa in the natural areas of Andalusia region (southern Spain). Due to their abundance and anemophilous character, high airborne pollen concentrations are detected in natural and urban areas of the region. Variations in its reproductive phenology can be considered an important bio-indicator regarding the impacts of climate change on vegetation in the Mediterranean region. This study aims to analyze trends in flowering patterns using airborne pollen concentrations from the capital cities of the 8 provinces of Andalusia region and to study its relationships with meteorological parameters and climate change over decades. Variations in time and intensity of flowering have been studied using different methods for defining the pollen season. This study demonstrates that for comparing results, it is relevant to choose the right definition to calculate the pollen season. The analysis of historical databases of Quercus airborne pollen in Andalusia showed variations in the floral phenology with an increase in the intensity of the pollen season throughout the studied period and an advance in the start trends due to the increase of temperature. Nevertheless, this increase might have been smoothed by the decrease of precipitations in some sampler locations, a limiting factor in the area. It has been also observed a delay in the end dates that caused a lengthening of the season. Climate change could be provoking longer and more intense pollen seasons that will lead to more intense and persistent symptoms in sensitive patients. [ABSTRACT FROM AUTHOR]

ABSTRACT Urbanization and urban sprawl generally degrade and diminish wildlife habitat, threatening to extirpate local populations. However, certain synanthropic species (e.g., coyotes, white‐tailed deer, and squirrels) are able to persist in urban environments and may even occur at greater densities than they do in their natural habitats. Eastern fox squirrels (Sciurus niger) are large tree squirrels that are known to be present in greater densities within urban areas. To determine how landscape characteristics may affect fox squirrel presence, we conducted line‐transect surveys along sidewalks on the Texas A&M University—College Station campus to record presence of fox squirrels and nearest tree species. We calculated Jacobs’ index of selectivity (D) for use of trees by fox squirrels along the transects. Squirrel density was calculated for all transects and modeled using linear regression with environmental (e.g., tree density) and survey (e.g., transect distance) variables. Fox squirrels preferred only a small number of the available tree species, primarily Quercus and Ulmus species. Observed fox squirrel density significantly increased with time of day, temperature, density of oaks (Quercus spp.), and density of all trees, and decreased with distance and area of the transect. These results suggest that even when urban areas contain suitable habitat, use of urban environments by wildlife is still highly selective and dependent on specific habitat requirements.

Abstract Key message Mining genome-wide DNA sequences enabled the discovery of near-diagnostic markers for species assignment in four European white oaks (Quercus petraea (Matt.) Liebl., Quercus pubescens Willd., Quercus pyrenaica Willd., and Quercus robur L.) despite their low interspecific differentiation. Near-diagnostic markers are almost fully fixed in one species and absent in the three others. As a result, only a handful of markers are needed for species identification, making this genetic assay a very promising operational taxonomic assignment procedure in research and forestry. Context Identifying species in the European white oak complex has been a long-standing concern in taxonomy, evolution, forest research, and management. Quercus petraea (Matt.) Liebl., Q. robur L., Q. pubescens Willd., and Q. pyrenaica Willd. are part of this species complex in western temperate Europe and hybridize in mixed stands, challenging species identification. Aims Our aim was to identify near-diagnostic single-nucleotide polymorphisms (SNPs) for each of the four species that are suitable for routine use and rapid diagnosis in research and applied forestry. Methods We first scanned existing whole-genome and target-capture data sets in a reduced number of samples (training set) to identify candidate diagnostic SNPs, i.e., genomic positions being characterized by a reference allele in one species and by the alternative allele in all other species. Allele frequencies of the candidates SNPs were then explored in a larger, range-wide sample of populations in each species (validation step). Results We found a subset of 38 SNPs (10 for Q. petraea, 7 for Q. pubescens, 9 for Q. pyrenaica, and 12 for Q. robur) that showed near-diagnostic features across their species distribution ranges with Q. pyrenaica and Q. pubescens exhibiting the highest (0.876) and lowest (0.747) diagnosticity, respectively. Conclusions We provide a new, efficient, and reliable molecular tool for the identification of the species Q. petraea, Q. robur, Q. pubescens, and Q. pyrenaica, which can be used as a routine tool in forest research and management. This study highlights the resolution offered by whole-genome sequencing data to design near-diagnostic marker sets for taxonomic assignment, even for species complexes with relatively low differentiation.

The current study reports the first records of an aphid-like pest and leaf pathogen on oak species in Bulgaria. In 2020-2023, leaf samples presenting characteristic yellow spots and lesions were collected from mature trees of Quercus petraea, Q. cerris, Q. frainetto and Q. robur in different localities of the country. Damage caused by oak obligate leaf pathogen Microstroma album, the leaf phylloxera, Phylloxera glabra, and the oak lace bug, Corythucha arcuata were identified on the lower surface of oak leaves. M. album was identified on all studied Quercus species. Angular white patches, the fruiting stage of the fungus, appeared on the lower surfaces of the leaves. P. glabra caused yellowish mosaic discoloration on the leaf surface of Quercus cerris, Q. frainetto and Q. pertaea. Sucking damage displayed a stippled pattern of yellow, brown, or whitish dots. In places where M. album develops, the invasive oak lace bug was often found as the only sucking species on oak leaves, which is most likely also a vector of the disease. Severe damage caused by established both obligate pathogen (M. album) and sucking insect pests (P. glabra, C. arcuata) could result in a weakening of the oak trees. On sufficiently weakened trees, secondary fungal pathogens or boring insects, commonly infested oak trees, can cause their death.

Abstract Background Climate change is expected to alter the factors that drive changes in adaptive variation. This is especially true for species with long life spans and limited dispersal capabilities. Rapid climate changes may disrupt the migration of beneficial genetic variations, making it challenging for them to keep up with changing environments. Understanding adaptive genetic variations in tree species is crucial for conservation and effective forest management. Our study used landscape genomic analyses and phenotypic traits from a thorough sampling across the entire range of Quercus longinux, an oak species native to Taiwan, to investigate the signals of adaptation within this species. Results Using ecological data, phenotypic traits, and 1,933 single-nucleotide polymorphisms (SNPs) from 205 individuals, we classified three genetic groups, which were also phenotypically and ecologically divergent. Thirty-five genes related to drought and freeze resistance displayed signatures of natural selection. The adaptive variation was driven by diverse environmental pressures such as low spring precipitation, low annual temperature, and soil grid sizes. Using linear-regression-based methods, we identified isolation by environment (IBE) as the optimal model for adaptive SNPs. Redundancy analysis (RDA) further revealed a substantial joint influence of demography, geology, and environments, suggesting a covariation between environmental gradients and colonization history. Lastly, we utilized adaptive signals to estimate the genetic offset for each individual under diverse climate change scenarios. The required genetic changes and migration distance are larger in severe climates. Our prediction also reveals potential threats to edge populations in northern and southeastern Taiwan due to escalating temperatures and precipitation reallocation. Conclusions We demonstrate the intricate influence of ecological heterogeneity on genetic and phenotypic adaptation of an oak species. The adaptation is also driven by some rarely studied environmental factors, including wind speed and soil features. Furthermore, the genetic offset analysis predicted that the edge populations of Q. longinux in lower elevations might face higher risks of local extinctions under climate change.

The main objective of the present study was to characterize the extracts obtained from the bark of three oak species in order to assess their use in potential cosmetic products.

Abstract Key message Despite been grown under the same climate, oak species are able to correlate with looser, but still identifiable, leaf morphological syndromes, composed by morphological traits with an ecological role in their respective macroclimates. Context Environmental restrictions imposed by climate have been shown to modulate leaf morphology. A reduction of leaf area in hot and dry climates reduces overheating because of a thinner boundary layer. Lobed shapes enhance hydraulic conductivity and faster cooling. Elongated leaves drain more quickly under high precipitation. Trichomes may help to reduce the effects of excessive sun exposure in hot and dry environments. Leaf mass per area (LMA) increases in stressful environments. Aim To assess the influence of global climate and clade on oak leaf syndromes comprising morphological traits with ecological roles. Methods We analyzed seven morphological traits in 141 oak species grown in a botanical garden, characterized into five macroclimates, and explored the partial effects of clade and climate. Results We found significant associations between macroclimate and every morphological trait measured. Temperate species tend to have large, obovate, lobed, malacophyllous leaves. Species occurring in dry habitats usually present small, rounded, pubescent, sclerophyllous leaves. Warm and wet climates induce the development of slender, lanceolate, glabrous leaves with an acuminate apex. Conclusion The functional roles of the different morphological traits are partially confirmed in genus Quercus as a response to the different macroclimates, where different leaf syndromes can be distinguished.

Vehicle pollution is a pervasive aspect of anthropogenic change across rural and urban habitats. The most common emissions are carbon- or nitrogen-based pollutants that may impact diverse interactions between plants and insect herbivores. However, the effects of vehicle pollution on plant-insect interactions are poorly understood. Here, we combine a city-wide experiment across the Sacramento Metropolitan Area and a laboratory experiment to determine how vehicle emissions affect insect herbivory and leaf nutritional quality. We demonstrate that leaf damage to a native oak species (Quercus lobata) commonly planted across the western US is substantially elevated on trees exposed to vehicle emissions. In the laboratory, caterpillars preferred leaves from highway-adjacent trees and performed better on leaves from those same trees. Synthesis and applications. Together, our studies demonstrate that the heterogeneity in vehicle emissions across cities may explain highly variable patterns of insect herbivory on street trees. Our results also indicate that trees next to highways are particularly vulnerable to multiple stressors, including insect damage. To combat these effects, urban foresters may consider planting trees that are less susceptible to insect herbivory along heavily travelled roadways.

Rising temperatures, increasing hydroclimate variability and intensifying disturbance regimes increase the risk of rapid ecosystem conversions. We can leverage multi‐proxy records of past ecosystem transformations to understand their causes and ecosystem vulnerability to rapid change.Prior to Euro‐American settlement, northern Indiana was a mosaic of prairie, oak‐dominated forests/woodlands and beech‐dominated hardwood forests. This heterogeneity, combined with well‐documented but poorly understood past beech population declines, make this region ideal for studying the drivers of ecosystem transformations.Here, we present a new record from Story Lake, IN, with proxies for vegetation composition (pollen), fire (charcoal) and beech intrinsic water use efficiency (δ13C of beech pollen; δ13Cbeech). Multiple proxies from the same core enable clear establishment of lead–lag relationships. Additionally, δ13Cbeech enables direct comparisons between beech population abundance and physiological responses to changing environments. We compare Story Lake to a nearby lake‐level reconstruction and to pollen records from nearby Pretty and Appleman Lakes and the distal Spicer Lake, to test hypotheses about synchrony and the spatial scale of governing processes.The 11.7 ka sediment record from Story Lake indicates multiple conversions between beech‐hardwood forest and oak forest/woodland. Beech pollen abundances rapidly increased between 7.5 and 7.1 ka, while oak declined. Oak abundances increased after 4.6 ka and remained high until 2.8 ka, indicating replacement of mesic forests by oak forest/woodland. At 2.8 ka, beech abundances rapidly increased, indicating mesic forest reestablishment. Beech and oak abundances correlate with charcoal accumulation rates but beech abundance is not correlated with δ13Cbeech.Fluctuations in beech abundances are synchronous among Story, Appleman and Pretty Lakes, but asynchronous between Story and Spicer Lakes, suggesting regulation by local‐scale vegetation‐fire‐climate feedbacks and secondarily by regional‐scale drivers.Holocene forest composition and fire dynamics appear to be closely co‐regulated and may be affected by local to regional climate variations. The importance of extrinsic drivers and positive/negative feedbacks changes over time, with higher ecoclimate sensitivity before 2.8 ka and greater resilience afterwards.Synthesis: Overall, oak‐ and beech‐dominated ecosystems were highly dynamic over the Holocene, with multiple ecosystem conversions driven by shifting interactions among vegetation, hydroclimate and fire regime. [ABSTRACT FROM AUTHOR]

The groundlayer flora has a disproportionate influence on ecosystem function and contributes to the biodiversity in temperate Quercus forests of eastern North America. Historically open understory conditions perpetuated, in part by fire, have become closed and homogenized by long‐term fire exclusion, likely impacting the groundlayer community. We explored the effects of burn season (unburned = CON, dormant season = DSB, growing season = GSB) on groundlayer (<1 m) vegetation attributes pre‐ and post‐burn. The difference (post‐burn – pre‐burn) in tree cover was greater in GSB (+8.22%) than DSB (+1.24%) and CON (+0.15%), while the change in forb cover was greater in GSB (+1.17%) than CON (−0.15%). Minor effects of burning were observed in diversity metrics, with the change in forb richness greater in GSB (+0.11 species/m2) than CON (−0.78 species/m2), while the change in tree richness was greater in GSB (+1.11 species/m2) than DSB (−1.11 species/m2) and CON (−1.67 species/m2). Nonmetric multi‐dimensional scaling provided evidence that between pre‐ and post‐burn, modest composition shifts in DSB and GSB were associated with more open conditions and lower litter depth. Understory composition did not vary among burn treatments pre‐burn, while post‐burn, composition differed significantly between CON and DSB and DSB and GSB. However, overall, a growing season burn had relatively minor effects on the groundlayer community compared to a dormant season burn. A better understanding of multiple factors affecting groundlayer response to burning is critical to the effective use of prescribed burning in attaining restoration goals. [ABSTRACT FROM AUTHOR]

A fundamental question in speciation genomics is how evolutionary processes shape the genomic landscape of differentiation between species. Regions of elevated differentiation, referred to as genomic islands, could be shared among closely related species (shared islands) or specific to a lineage (lineage‐specific islands). Shared islands are typically assumed to result from background selection. However, simulations and empirical studies have suggested that positive selection contributes to both shared and lineage‐specific islands. Here, we utilized comparative population genomics to examine the contributions of different evolutionary processes to patterns of genetic differentiation when gene flow and incomplete lineage sorting are minimal. We used whole‐genome resequencing data for 135 individuals from four oak species, including two independent species pairs, Quercus variabilis Blume and Quercus acutissima Carruth. in the subgenus Cerris, and Quercus dentata Thunb. and Quercus griffithii Hook.f. & Thomson ex Miq. in the subgenus Quercus. We found that both shared and subgenus‐specific islands were caused by positive selection, including selective sweeps in current populations and in their most recent common ancestors. Moreover, the recombination rate was a better predictor of genomic differentiation than gene density. Overall, our results reveal that recombination and positive selection impacted genomic differentiation considerably and provide a more precise grasp of how genomic islands formed in Quercus. [ABSTRACT FROM AUTHOR]

A phylogeographic study on the chloroplast DNA of natural white oak forests (Quercus subgen. Quercus, sect. Quercus) was carried out to identify possible haplotype-structured distribution within the Italian Peninsula, Sicily, and Sardinia. Sixty white oak populations belonging to Q. frainetto, Q. robur and the collective groups Q. petraea and Q. pubescens were considered and analyzed by combining five Chloroplast Simple Sequence Repeat (cpSSR) markers. A total of 28 haplotypes were detected. Central and southern Italy displayed the highest variability (14 and 10 haplotypes, respectively), followed by northern Italy (7), Sardinia (7), and Sicily (5). A complex geographical structure of the haplotype distribution emerged, highlighting (i) a high number of low-frequency haplotypes; (ii) the marked isolation of Sardinia; (iii) the occurrence of haplotypes widely distributed throughout the Italian Peninsula; (iv) the idiosyncrasy of Sicily, which exhibits exclusive haplotypes, and haplotypes shared with Sardinia and the rest of the Italian Peninsula. The haplotype distribution was also found to be partially related to the taxonomic identity of the specimens, with the following features emerging: a geographic separation between the central Italy and southern Italy Q. frainetto populations, an unexpected discontinuity between the Calabrian and Sicilian Q. petraea subsp. austrotyrrhenica populations, and the absence of the most common haplotype among the Q. pubescens populations of central and southern Italy. [ABSTRACT FROM AUTHOR]

Acute Oak Decline (AOD) is an oak disease that was first described in the United Kingdom. From the time the first symptoms appear, the disease can kill trees even within 6 years. One of the factors causing this disease is the action of the pathogenic bacteria Brenneria goodwinii, Rahnella victoriana and Gibbsiella quercinecans. In recent years, a deterioration in the condition of oak stands has been observed throughout Slovakia. These trees show exudates characteristic of AOD, which may indicate the presence of pathogenic bacteria. Samples of such symptomatic exudates from tree trunks were collected and analysed on 20 different plots in central and western Slovakia. Using real-time PCR, the presence of Brenneria goodwinii and Gibbsiella quercinecans was confirmed in ten and three stands, respectively. This report is the first information about the observation of these bacteria in weakened stands of Quercus robur in Slovakia. [ABSTRACT FROM AUTHOR]