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Key messageEmbryonic axes of acorns have greater variability of mass than cotyledons or pericarp. Above/below ground seedling mass depends on oak species.Species of the genus oak are of great importance for forest ecosystems in almost all of the Holarctic. Knowledge of the diversity of the size of acorns and their parts would allow better use of the opportunity of genetic resources storage, both for the protection of endangered oak species and for forestry practices. The initial development of seedlings in reference to the size of the acorn, its parts and acorn maturation time was also investigated. The fresh and dry mass of individual acorns, embryonic axes and cotyledons of 15 species (Quercus agrifolia, Q. gambelli, Q. kelloggii, Q. alba, Q. bicolor, Q. coccinea, Q. falcata, Q. lyrata, Q. nigra, Q. prinus, Q. rubra, Q. cerris, Q. ilex, Q. petraea, and Q. robur) were determined. In the second part of the study, the mass of the ca. 3-month-old seedlings that had completed the first stage of growth, with a division on the leaves, the shoot and the root, was measured. The greatest variation in mass both between and within the species was demonstrated for the embryonic axis. The mass of seedlings depends on the size of the acorn and the cotyledons contained therein; whereas, the mass of the embryonic axis has no significant influence on the mass of seedlings.

Latitudinal and elevational gradients provide valuable experimental settings for studies of the potential impact of global warming on forest tree species. The availability of long-term phenological surveys in common garden experiments for traits associated with climate, such as bud flushing for sessile oaks (Quercus petraea), provide an ideal opportunity to investigate this impact. We sequenced 18 sessile oak populations and used available sequencing data for three other closely related European white oak species (Quercus pyrenaica, Quercus pubescens, and Quercus robur) to explore the evolutionary processes responsible for shaping the genetic variation across latitudinal and elevational gradients in extant sessile oaks. We used phenotypic surveys in common garden experiments and climatic data for the population of origin to perform genome-wide scans for population differentiation and genotype-environment and genotype-phenotype associations. The inferred historical relationships between Q. petraea populations suggest that interspecific gene flow occurred between Q. robur and Q. petraea populations from cooler or wetter areas. A genome-wide scan of differentiation between Q. petraea populations identified single nucleotide polymorphisms (SNPs) displaying strong interspecific relative divergence between these two species. These SNPs followed genetic clines along climatic or phenotypic gradients, providing further support for the likely contribution of introgression to the adaptive divergence of Q. petraea populations. Overall, the results indicate that outliers and associated SNPs are Q. robur ancestry-informative. We discuss the results of this study in the framework of the postglacial colonization scenario, in which introgression and diversifying selection have been proposed as essential drivers of Q. petraea microevolution.

To detect and avoid illegal logging of valuable tree species, identification methods for the origin of timber are necessary. We used next-generation sequencing to identify chloroplast genome regions that differentiate the origin of white oaks from the three continents; Asia, Europe, and North America. By using the chloroplast genome of Asian Q. mongolica as a reference, we identified 861 variant sites (672 single nucleotide polymorphisms (SNPs); 189 insertion/deletion (indel) polymorphism) from representative species of three continents (Q. mongolica from Asia; Q. petraea and Q. robur from Europe; Q. alba from North America), and we identified additional chloroplast polymorphisms in pools of 20 individuals each from Q. mongolica (789 variant sites) and Q. robur (346 variant sites). Genome sequences were screened for indels to develop markers that identify continental origin of oak species, and that can be easily evaluated using a variety of detection methods. We identified five indels and one SNP that reliably identify continent-of-origin, based on evaluations of up to 1078 individuals representing 13 white oak species and three continents. Due to the size of length polymorphisms revealed, this marker set can be visualized using capillary electrophoresis or high resolution gel (acrylamide or agarose) electrophoresis. With these markers, we provide the wood trading market with an instrument to comply with the U.S. and European laws that require timber companies to avoid the trade of illegally harvested timber.

Background Expressed Sequence Tags (ESTs) are a source of simple sequence repeats (SSRs) that can be used to develop molecular markers for genetic studies. The availability of ESTs for Quercus robur and Quercus petraea provided a unique opportunity to develop microsatellite markers to accelerate research aimed at studying adaptation of these long-lived species to their environment. As a first step toward the construction of a SSR-based linkage map of oak for quantitative trait locus (QTL) mapping, we describe the mining and survey of EST-SSRs as well as a fast and cost-effective approach (bin mapping) to assign these markers to an approximate map position. We also compared the level of polymorphism between genomic and EST-derived SSRs and address the transferability of EST-SSRs in Castanea sativa (chestnut). Results A catalogue of 103,000 Sanger ESTs was assembled into 28,024 unigenes from which 18.6% presented one or more SSR motifs. More than 42% of these SSRs corresponded to trinucleotides. Primer pairs were designed for 748 putative unigenes. Overall 37.7% (283) were found to amplify a single polymorphic locus in a reference full-sib pedigree of Quercus robur . The usefulness of these loci for establishing a genetic map was assessed using a bin mapping approach. Bin maps were constructed for the male and female parental tree for which framework linkage maps based on AFLP markers were available. The bin set consisting of 14 highly informative offspring selected based on the number and position of crossover sites. The female and male maps comprised 44 and 37 bins, with an average bin length of 16.5 cM and 20.99 cM, respectively. A total of 256 EST-SSRs were assigned to bins and their map position was further validated by linkage mapping. EST-SSRs were found to be less polymorphic than genomic SSRs, but their transferability rate to chestnut, a phylogenetically related species to oak, was higher. Conclusion We have generated a bin map for oak comprising 256 EST-SSRs. This resource constitutes a first step toward the establishment of a gene-based map for this genus that will facilitate the dissection of QTLs affecting complex traits of ecological importance.

The variation of Quercus variabilis leaf delta super( 13 ) C along latitude resulted primarily from phenotypic acclimation to climate. The determination of relative contribution by genetic adaptation and phenotypic acclimation to leaf delta super(13)C variation helps the use of this index for reconstructing paleoclimates, developing terrestrial carbon dynamic models, and evaluating plant water use efficiency under predicted climate change. Using a 4-year in situ investigation across eastern China and a common garden experiment to explore plastic versus adaptive effects on the variation of leaf delta super(13)C in Quercus variabilis, a widely distributed, economically important species in China. The leaf delta super(13)C of in situ populations ranged from -24.05 to -30.74 ppt, and increased significantly with latitude, which was positively related to index of aridity, and negatively to mean annual temperature. However, there was little variation in leaf delta super(13)C of seedlings from 16 populations planted in a common garden. These findings indicate the dominance of phenotypic acclimation in leaf delta super(13)C variation. The hierarchical partitioning analysis further suggested that observed changes of in situ leaf delta super(13)C had little association with leaf mass per area and nitrogen. These results suggest that Q. variabilis is physiologically flexible in acclimation to rapid climate change and can be a model plant species for studying the impacts of climate change on plant ecophysiology.

• Annually variable and synchronous seed production by plant populations, or masting, is a widespread reproductive strategy in long-lived plants. Masting is thought to be selectively beneficial because interannual variability and synchrony increase the fitness of plants through economies of scale that decrease the cost of reproduction per surviving offspring. Predator satiation is believed to be a key economy of scale, but whether it can drive phenotypic evolution for masting in plants has been rarely explored. • We used data from seven plant species (Quercus humilis, Quercus ilex, Quercus rubra, Quercus alba, Quercus montana, Sorbus aucuparia and Pinus pinea) to determine whether predispersal seed predation selects for plant phenotypes that mast. • Predation selected for interannual variability in Mediterranean oaks (Q. humilis and Q. ilex), for synchrony in Q. rubra, and for both interannual variability and reproductive synchrony in S. aucuparia and P. pinea. Predation never selected for negative temporal autocorrelation of seed production. • Predation by invertebrates appears to select for only some aspects of masting, most importantly high coefficient of variation, supporting individual-level benefits of the population-level phenomenon of mast seeding. Determining the selective benefits of masting is complex because of interactions with other seed predators, which may impose contradictory selective pressures.

This study addresses relationships between leaf phenology, xylogenesis, and functional xylem anatomy in two ring‐porous oak species, the temperate Quercus robur and the sub‐Mediterranean Q. pyrenaica. Earlywood vessel (EV) formation and leaf phenology were monitored in 2012 and 2013. Ten individuals per species were sampled at each of three sites located in NW Iberian Peninsula. EV areas measured on microcore sections were used to calculate the hydraulic tree diameter (Dₕ), in order to model relationships to phenology. Thermal requirements were evaluated using growing degree days (GDD). A species‐specific timing of growth resumption was found. The onset of EV formation and budburst were associated to a particular GDD in each species. The onset and duration of EV enlargement affected Dₕ (and EV size) in Q. robur, but hardly in Q. pyrenaica. The relationship between the timings of EV formation and xylem structure appears to be stronger for the temperate oak, whose larger vessels may result from thermal‐induced earlier resumption. In contrast, the sub‐Mediterranean oak would maintain a more conservative hydraulic architecture under warming conditions.

• Here, we investigated the physiological and structural leaf responses of seedlings of two evergreen and two deciduous Quercus species, grown in a glasshouse and subjected to contrasted conditions of light (low, medium and high irradiance) and water (continuous watering vs 2-months drought). • The impact of drought on photosynthetic rate was strongest in high irradiance, while the impact of shade on photosynthetic rate was strongest with high water supply, contradicting the hypothesis of allocation trade-off. • Multivariate causal models were evaluated using d-sep method. The model that best fitted the dataset proposed that the variation in specific leaf area affects photosynthetic rate and leaf nitrogen concentration, and this trait determines stomatal conductance, which also affects photosynthetic rate. • Shade conditions seemed to ameliorate, or at least not aggravate, the drought impact on oak seedlings, therefore, the drought response on leaf performance depended on the light environment.

Predicting species' potential geographical range by species distribution models (SDMs) is central to understand their ecological requirements. However, the effects of using different modeling techniques need further investigation. In order to improve the prediction effect, we need to assess the predictive performance and stability of different SDMs. We collected the distribution data of five common tree species (Pinus massoniana, Betula platyphylla, Quercus wutaishanica, Quercus mongolica and Quercus variabilis) and simulated their potential distribution area using 13 environmental variables and six widely used SDMs: BIOCLIM, DOMAIN, MAHAL, RF, MAXENT, and SVM. Each model run was repeated 100 times (trials). We compared the predictive performance by testing the consistency between observations and simulated distributions and assessed the stability by the standard deviation, coefficient of variation, and the 99% confidence interval of Kappa and AUC values. The mean values of AUC and Kappa from MAHAL, RF, MAXENT, and SVM trials were similar and significantly higher than those from BIOCLIM and DOMAIN trials (p<0.05), while the associated standard deviations and coefficients of variation were larger for BIOCLIM and DOMAIN trials (p<0.05), and the 99% confidence intervals for AUC and Kappa values were narrower for MAHAL, RF, MAXENT, and SVM. Compared to BIOCLIM and DOMAIN, other SDMs (MAHAL, RF, MAXENT, and SVM) had higher prediction accuracy, smaller confidence intervals, and were more stable and less affected by the random variable (randomly selected pseudo-absence points). According to the prediction performance and stability of SDMs, we can divide these six SDMs into two categories: a high performance and stability group including MAHAL, RF, MAXENT, and SVM, and a low performance and stability group consisting of BIOCLIM, and DOMAIN. We highlight that choosing appropriate SDMs to address a specific problem is an important part of the modeling process.

Background The German naturalist Alexander von Humboldt conducted an expedition through the American continent, alongside Aimé Bonpland, from 1799 to 1804. Before finally returning to Europe, they decided to take a side trip to the USA between May 20 and July 7, 1804. Humboldt’s most detailed account of his time in the USA consists of a manuscript entitled “Plantae des États-Unis” (1804), containing information on useful plants and timber of the country. The aim of this paper is to retrieve, for the first time, ethnobotanical information regarding North American plants and their uses inside this Humboldt’s manuscript as well as to highlight the erasure and invisibilization of North American Indigenous knowledge within historical documents and bibliography, mainly during the nineteenth century. Methods “Plantae des États-Unis” (digitized version and its transcription) was carefully analyzed, and information on plant species mentioned in the manuscript (including botanical and vernacular names, traditional uses, and general observations) was retrieved. Traditional uses were correlated with ethnobotanical data from the Native American Ethnobotany Database and encyclopedic literature on North American plants from the nineteenth and early twentieth centuries, as well as recent pharmacological studies searched in scientific papers. Results In the manuscript are mentioned 28 species distributed in 15 botanical families, with Fagaceae (9 Quercus species) being the most representative. All species are USA natives, except for one undetermined species (only the genus was mentioned, Corylus ). Four species were directly mentioned as medicinal ( Toxicodendron radicans , Liriodendron tulipifera , Actaea racemosa , and Gillenia stipulata ), while other four were described as tanning agents (astringent) ( Cornus florida , Diospyros virginiana , Quercus rubra , and Quercus velutina ). Two species were described as bitter ( Xanthorhiza simplicissima and A. racemosa ). Nine Quercus species were described, but five were reported as the most useful oaks for cultivation in Europe ( Quercus bicolor , Quercus castanea , Quercus virginiana , Quercus michauxii , and Quercus alba ); three of them were used for ship construction ( Q. virginiana , Q. michauxii , and Q. alba ), two as astringent ( Q. rubra and Q. stellata ), and one had wood of poor quality ( Quercus phellos ). One species was described as a yellow dye ( Hydrastis canadensis ), and the other was mentioned as toxic ( Aesculus pavia ). Ten species did not have any useful applications listed. Conclusions Although “Plantae des États-Unis” is a brief collection of annotations, these data reveal a historical scenario of outstanding plants with social and economic interest in the USA at the beginning of the nineteenth century. The data highlight a clear process of suppression of the traditional knowledge of Native North American Indigenous peoples in past historical records and literature, due to the lack of acknowledgment by white European settlers and American-born explorers. This ethnobotanical inventory may help us understand the relationship between plants and Native North American Indigenous peoples, as well as European naturalists and settlers, and USA-born people in the past, and reflect on the importance of Indigenous traditional knowledge, bioeconomy, sustainable management, and conservation of biodiversity in the present and future.