Nigra Populations Research Articles

SRAP markers for characterization of the genetic diversity and differentiation of Pinus nigra populations in protected forested areas in Bulgaria, Greece, and Cyprus

The present study aimed to evaluate the genetic diversity and differentiation of Pinus nigra Arnold, the European black pine, populations located in protected forested areas in three countries from the Balkan and Mediterranean region: Bulgaria, Greece, and Cyprus. Totally, 175 DNA samples from P. nigra plants collected from eight populations in these countries were analyzed using three SRAP primer pairs. The applied SRAP markers demonstrated high-resolution power, resulting in the identification of an average of 215 ± 67 polymorphic loci per SRAP primer pair. The analysis of molecular variance (AMOVA) showed that 82% of the observed variation was due to intra-population variation, while 18% was due to inter-population variation. The overall analysis of the population structure suggested low (Fst ≤ 0.01) intra-country differentiation for the populations from Bulgaria and Cyprus and moderate (0.15 ≤ Fst ≤ 0.17) inter-country differentiation. On the contrary, high differentiation between the populations (0.06 ≤ Fst ≤ 0.20) and complex genetic structure were characteristic of the three populations from Greece, relatively closely located in the area of the Pindos National Park. Analysis of the population structure also revealed that one of the Pindos populations belonged to the cluster of Bulgarian populations (Fst ≤ 0.01), showing moderate (Fst ≤ 0.11) to high (Fst ≤ 0.20) genetic differentiation from the other analyzed Pindos populations. The further use of SRAP markers for mapping the genetic diversity among P. nigra populations and identification of local populations diverted from the overall phylogeography-driven pattern in the studied region are discussed.

Genetic Structure and Diversity of Dalbergia nigra from Brazilian Atlantic Forest Fragments

Dalbergia nigra is a long-living tree endemic to the Atlantic Rain Forest. Due to its high commercial value, this species has been widely exploited for timber production and is now endangered. It is widely known that understanding patterns of genetic structure is paramount for conserving threatened species. We analyzed the genetic diversity of 140 individuals from four different forest fragments in the southern region of Bahia, Brazil, to verify the possible effects of fragmentation on these populations and provide information for conservation initiatives. High polymorphism levels were detected from the genotyping of nine microsatellite loci (mean HE = 0.733). All populations showed high genetic diversity; however, a reduction of genetic diversity was detected in each population (HO < HE). The average fixation index was high and significant (f = 0.167), which could be due to the occurrence of inbreeding, the Wahlund effect, reproductive system, or from null alleles. Genetic differentiation among populations was high (mean θP = 0.118), suggesting strong isolation, a pattern consistent with historically low gene flow. The Bayesian analysis revealed five different genetic groups, among which three groups correspond to three different forest fragments, and two groups showed the genetic subdivision of individuals from the other forest fragment. Based on our results, the suggested conservation strategy for D. nigra populations in the southern region of Bahia, Brazil, involves high environmental investments to protect all sampled forest fragments and individuals. Another strategy would be to collect seeds from all individuals from the sampled fragments and start a new population with human interference in its evolutive history inside a protection unit.

Genetics and epigenetics of Pinus nigra populations with differential exposure to air pollution.

Forest species in the course of their evolution have experienced several environmental challenges, which since historic times include anthropogenic pollution. The effects of pollution on the genetic and epigenetic diversity in black pine (Pinus nigra) forests were investigated in the Amyntaio - Ptolemais - Kozani Basin, which has been for decades the largest lignite mining and burning center of Greece, with a total installed generating capacity of about 4.5 GW, operating for more than 70 years and resulting in large amounts of primary air pollutant emissions, mainly SO2, NOx and PM10. P. nigra, a biomarker for air pollution and a keystone species of affected natural ecosystems, was examined in terms of phenology (cone and seed parameters), genetics (283 AFLP loci) and epigenetics (606 MSAP epiloci), using two populations (exposed to pollution and control) of the current (mature trees) and future (embryos) stand. It was found that cone, seed, as well as genetic diversity parameters, did not show statistically significant differences between the exposed population and the control. Nevertheless, statistically significant differences were detected at the population epigenetic level. Moreover, there was a further differentiation regarding the intergenerational comparison: while the epigenetic diversity does not substantially change in the two generations assessed in the control population, epigenetic diversity is significantly higher in the embryo population compared to the parental stand in the exposed population. This study sheds a light to genome dynamics in a forest tree population exposed to long term atmospheric pollution burden and stresses the importance of assessing both genetics and epigenetics in biomonitoring applications.

Invasive plant species that experience lower herbivory pressure may evolve lower diversities of chemical defense compounds in the exotic range.

Invasive plant species often escape from specialist herbivores and are more likely to be attacked by generalist herbivores in the exotic range. Consequently, the shifting defense hypothesis predicts that invasive plants will produce higher concentrations of qualitative defense compounds to deter dominant generalist herbivores in the exotic range. Here, I additionally propose a reduced chemical diversity hypothesis (RCDH), which predicts that reduced herbivory pressure will select for invasive plant genotypes that produce lower diversities of chemical defense compounds in the exotic range. I tested whether (1) invasive Brassica nigra populations express a lower diversity and an overall higher concentration of glucosinolate compounds than native-range B. nigra; (2) Brassica nigra individuals that express high diversities and concentrations of glucosinolate compounds are more attractive to specialist and deterrent to generalist herbivores; and (3) tissues of invasive B. nigra are less palatable than tissues of native-range B. nigra to the generalist herbivores Theba pisana and Helix aspersa. Invasive B. nigra populations produced a significantly lower diversity of glucosinolate compounds, a marginally higher concentration of total glucosinolates,and a significantly higher concentration of sinigrin (the dominant glucosinolate). Leaf tissues of invasive B. nigra were significantly less palatable to T. pisana and marginally less so to H. aspersa. Brassica nigra individuals that expressed high concentrations of total glucosinolate compounds were visited by a low diversity of generalist herbivore species in the field. In line with the RCDH, the lower diversity of glucosinolate compounds produced by invasive B. nigra populations likely resulted from selection imposed by reduced herbivory pressure in the exotic range.

Growth Pattern of European Black Pine outside Its Current Natural Range: A Case Study in Portugal

European Black Pine (Pinus nigra J.F. Arnold) is a fast-growing conifer, currently distributed in a fragmented pattern from western North Africa through Southern Europe to Asia Minor and is an economically important native conifer in Southern Europe. In Portugal, P. nigra populations are allochthonous, and were planted 50–90 years ago with plant material of unknown origin. This work intended to evaluate and investigate long-term radial growth characteristics of the species on the westernmost part of Europe, outside its natural range, in mainland Portugal. To achieve this objective, six planted stands located in the north and centre of the country were chosen, which were considered representative of the distribution of the species in the country and the most extreme south-western location in Europe. The height and diameter at breast height was measured and the general state of these stands was evaluated. Overall, no mortality was observed except in one site, where trees manifested poor growth. Sampling a set of 15 trees per site, was used to create a database for analysis of the radial development of the species. The 90 trees sampled, with ages ranging from 56–98 years, provided a database of 5308 observations of diameter-age pairs. The Schumacher function was tested for the description of radial growth and provided satisfying results in terms of the model fitness, allowing us to summarize general trends of diameter growth among sites. Complementary analysis of radial growth at a tree age of 50-yr was performed to assess for differences among populations. It was concluded that radial growth differs between sites, and two statistically different groups were identified, although no specific latitudinal or longitudinal gradients were found. The information on the identified growth patterns can be used for decision-making purposes when considering species selection in afforestation or reforestation procedures in the context of adaptive management.

Environmental and Plant Variables Influence Dalbergia nigra (Fabaceae) Phenology - Implications for Seed Production

Studies of plant phenology in the Atlantic Forest can be enhanced by a greater understanding of the factors regulating vegetative and reproductive cycles. Dalbergia nigra (Vell.) Allemão ex Benth. is endemic and vulnerable in the Atlantic Forest. We analyzed abiotic aspects and plant traits that modulate the phenologies of D. nigra by monitoring 135 individuals in four subpopulations from different remnant forests for 24 months. The growth and shapes of the plants, as well as environmental variables, were determined. Circular analysis evidenced phenological variations among subpopulations and evaluation periods. Multiple factor analysis evidenced that phenological variations are mainly correlated with precipitation, temperature, and tree height. The combination of environmental conditions and plant characteristics affect synchronicity and phenological intensity. Low fruiting intensity (less than 50%) limits seed production and recruitment. We emphasize the importance of forest remnants and the need to increase D. nigra populations in future reforestation projects.

Forest structure drives the expected growth of Pinus nigra along its latitudinal gradient under warming climate

Droughts chronically alter resource availability in forest ecosystems. The increased frequency and severity of such extreme climate events challenge the acclimation potential of tree species especially across the drought-prone Mediterranean region. Pinus nigra is a widely distributed tree species in the Mediterranean region and considered vulnerable to extreme droughts. We used a 1000 km latitudinal gradient from northern Morocco to north-eastern Spain incorporating four regions (Edge-South, Core-South, Core-North and Edge-North) and including different P. nigra provenances. We aim to identify the climate and forest structure related drivers that influence tree radial growth (BAI, basal area increment). We developed statistical models for BAI by incorporating the potential effects of climate and forest structure (diameter and age distributions). Then, we forecasted the future growth of P. nigra forests during the 21st century considering the emission scenario A2 with an expected increase of +2.7 °C at the end of this century. Our results showed large variability across P. nigra populations in terms of environmental conditions, forest structure, and growth. The northernmost P. nigra populations, subjected to wetter and cooler conditions were those presenting the lowest BAI (4.9 cm2), whereas the southernmost P. nigra populations subjected to drier and warmer conditions presented the highest BAI values (11.5 cm2). Pinus nigra growth was enhanced by high spring precipitation, but this positive effect was probably modulated by forest structure. Temperature explained a higher proportion of the BAI variance than precipitation, with warmer summer conditions decreasing growth. Growth projections forecasted a decline in BAI (from 9.6 to 7.0 cm2) across all ecological regions starting around the mid-21st century but being lower in Edge-North populations compared to the other populations. Our study provides quantitative knowledge related to how P. nigra populations have been growing across four distinctive ecological regions. We also provide a forecasting tool that incorporates both climate and stand structure related information to project dynamics in tree populations.

Diversity and genetic structure in a mini-garden of Dalbergia nigra: A tree threatened with extinction in the Atlantic Forest

Maintaining genetic variability within rare or threatened species is essential for the development of conservation and restoration strategies. Therefore, the objective of this study was to characterize the diversity and genetic structure in Dalbergia nigra mini-garden. DNA samples from 90 individuals of D. nigra originated from seeds collected in Linhares-ES and Viçosa-MG were analyzed using Inter Simple Squence Repeat (ISSR) markers. For this, eleven primers were selected, which generated 180 fragments (70.76% polymorphism). The polymorphic information content (PIC) for the markers used averaged 0.38, considering them as moderately informative. The number of ISSR fragments to obtain desired precision in genetic diversity analyses was shown to be 122 polymorphic fragments, which was attained by examining 11 ISSR markers with clear amplification patterns. It was observed that for the origin of Linhares the number of alleles observed (Ao) was 1.99 and the number of effective alleles (Ae) was 1.60. For the origin of Viçosa, the values of Ao and Ae were 1.92 and 1.57, respectively. High genetic diversity was found with parameters Shannon index (I* = 0.5538) and genetic diversity of Nei (H* = 0.3742) for all populations sampled; from Viçosa, these parameters were 0.4963 and 0.3334, respectively, and from Linhares, they were 0.5328 and 0.3563. In the graphic representation of genetic distances, 10 groups were formed, three of them with only one genotype in each group. Among the individuals from Viçosa, the presence of five groups was revealed, one of which was isolated. For comparisons between individuals from Linhares, grouping by the Unweighted Pair Group Method with Arithmetic mean (UPGMA) method revealed seven groups, two of which contained only one individual. Molecular variance analysis (AMOVA) for D. nigra populations indicated moderate genetic differentiation (ΦST = 0.118). The ΔK statistic corroborates the analysis of the structure, indicating the convergence of two Bayesian groups (K = 2). The ISSR markers were efficient in detecting genetic diversity in D. nigra. The populations of D. nigra present moderate genetic differentiation, with the highest proportion of genetic diversity within the populations. Mini-stumps have high diversity and, therefore, have the potential to be used as matrices for the collection of propagules in the production of seedlings for conservation purposes.

Wild Sambucus nigra L. from north-east edge of the species range: A valuable germplasm with inhibitory capacity against SARS-CoV2 S-protein RBD and hACE2 binding in vitro

Berries and flowers of Sambucus nigra L. tree are well known for their ability to mitigate symptoms of upper respiratory disorders related to reported antiviral properties. Industrial application and commercial cultivation of S. nigra is largely limited to a few widely grown cultivars. Restricted genetic diversity of cultivated S. nigra can be disadvantageous if new industrial applications are discovered. In this study wild S. nigra populations located on the north-east edge of the species natural range were explored by assessing genetic origin, berry and flower anti-oxidative potential, and berry rutin content. Best performing wild S. nigra extracts were selected for an assessment of previously unreported biological activity- inhibitory capacity against SARS-CoV2 S1 protein receptor binding domain (RBD) binding to recombinant human angiotensin -converting enzyme 2 (ACE2) receptor in vitro based on competitive enzyme linked immunosorbent assay (ELISA). Inter-simple sequence repeat (ISSR) marker-based genetic characterization suggested that explored wild S. nigra populations result from wild gene pool expanding northwards with admixture of historically introduced cultivated S. nigra. Average values of total phenolic content, anti-radical activity, and total flavonoids content of wild S. nigra populations did not exceed those of cv. ‘Haschberg’. Concentration-dependent inhibition of ACE2-SARS-CoV2 S-protein RBD binding was demonstrated in vitro for elderberry fruits and flowers extracts (IC50 of 1.66 mg DW ml−1 and 0.532 mg DW ml−1, respectively). Wild elderberry fruit extract exhibited higher inhibitory capacity than the extract from berries of cv ‘Haschberg’. This study validates the requirement for S. nigra wild germplasm bioprospecting and opens up directions for further research of new anti-SARS-CoV2 industrial applications of S. nigra.

Antennal transcriptome analysis and candidate olfactory genes in Crematogaster rogenhoferi

Crematogaster rogenhoferi (Hymenoptera: Formicidae), an omnivorous ant, is one of the dominant predatory natural enemies of a soft scale pest, Parasaissetia nigra Nietner (Homoptera: Coccidae), and can effectively control P. nigra populations in rubber forests. Olfaction plays a vital role in the process of predation. However, the information about the molecular mechanism of olfaction-evoked behaviour in C. rogenhoferi is limited. In this study, we conducted antennal transcriptome analysis to identify candidate olfactory genes. We obtained 53,892 unigenes, 16,185 of which were annotated. Based on annotations, we identified 49 unigenes related to chemoreception, including four odourant-binding proteins, three chemosensory proteins, 37 odourant receptors, two odourant ionotropic receptors and three sensory neuron membrane proteins. This is the first report on the molecular basis of the chemosensory system of C. rogenhoferi. The findings provide a basis for elucidating the molecular mechanisms of the olfactory-related behaviours of C. rogenhoferi, which would facilitate a better application of C. rogenhoferi as a biological control agent.

Seasonal adult occurrence of a coccidophagous ladybird, Telsimia nigra (Coleoptera: Coccinellidae), in citrus groves in central Japan

A coccidophagous ladybird, Telsimia nigra (Weise) (Coleoptera: Coccinellidae), may play a significant role in suppressing the abundance of scale insects belonging to Diaspididae (Hemiptera: Coccoidea) in citrus groves in Japan, and therefore might need to be protected from pesticide applications. Seasonal changes in the abundance of T. nigra adults were monitored using yellow sticky traps set inside citrus tree canopies and by beating citrus foliage in citrus groves with different pesticide application levels in Shizuoka City, central Japan. Telsimia nigra adults were caught on sticky traps in pesticide-free, organic, and reduced-pesticide groves, with far more adults in a pesticide-free grove, but were rarely recorded in conventionally managed groves. A larger number of T. nigra adults were captured on the traps from late March to early May, with a peak numbers in early to mid-April in the pesticide-free grove, and afterward adults were continually detected in much smaller numbers until November. Some adults were trapped mainly in April–May and October in organic and reduced-pesticide groves, with more adults in the former months. Adults collected by beating citrus foliage tended to be more abundant in April and November in the pesticide-free grove. Thus, T. nigra adults occurred most abundantly in April–May and in smaller numbers in October–November in citrus groves in Shizuoka City. This result suggests that the application of pesticides that are harmful to ladybirds should be avoided in April–May and autumn to conserve T. nigra populations in citrus groves in central Japan.

Physical, chemical and mechanical wood properties of Pinus nigra growing in Portugal

The wood of Pinus nigra populations planted in Portugal, comparatively to Pinus pinaster , has higher total extractive content, lower Klason lignin and H/G ratio, and similar mechanical properties, presenting advantages for industrial purposes. P. nigra was used in the reforestation of mountainous areas in Portugal, but its wood chemical and mechanical properties were never studied. This work intends to evaluate the chemical and mechanical wood properties of the P. nigra populations planted in Portugal, to relate these properties with previously characterised physical features and to compare these data with other European P. nigra stands and species, namely, P. pinaster. Wood chemical and mechanical properties were analysed in 90 trees from six Portuguese sites, using near-infrared (NIR) spectrometry and the three-point bending test. The wood of the P. nigra populations planted in Portugal presented average values of total extractive content = 9.4%, Klason lignin = 26.69%, MORRad = 14.93 MPa and MOERad = 1200.98 MPa. Ring density showed no significant correlation with ring width. The P. nigra populations planted in Portugal presented qualitative and quantitative properties similar to P. pinaster wood, the main resinous species in Portugal. Facing the lack of raw material for wood industry due to frequent forest fires in the Mediterranean region, P. nigra could be used to reforest mountainous areas of those regions.

Verification of new Populus nigra L. clone improvement based on their performance over three rotations

Abstract: Populus nigra is an important autochthonous woody plant that can be grown as a renewable energy source. The possibility of its improvement through intraspecific hybridization was tested. Differences in biomass production, growth parameters, Melampsora larici-populina rust resistance and drought tolerance were evaluated among 19 intraspecific hybrids from controlled crosses, 2 clones selected from natural populations and the “MAX 4” clone (P. nigra × P. maximowiczii). These P. nigra clones from controlled crosses were chosen from more than 2000 hybrid individuals whose parents were selected from natural populations in the Czech Republic. A field trial was set up in Pruhonice, Czech Republic (320 m a.s.l., 591 mm rainfall annually, mean annual temperature of 9.5 °C). The planting density was 6061 plants ha-1, and the plants were coppiced three times at 3-year intervals. The trial was irrigated only during its establishment. Among the clones, significant differences were found in all the evaluated traits over three rotations. An average dry matter yield of the best clone “MAX 4” was 12.8 t ha-1 yr-1 over three harvests. The best black poplar clone reached up to 9.4 t ha-1 yr-1 in three harvests. Rust resistance was constant over 9 years and high for the three P. nigra clones (two from controlled crosses and one from natural populations). Moreover, the best P. nigra clones from controlled crosses showed higher drought tolerance than the “MAX 4” clone. Breeding progress was confirmed, and most of the P. nigra clones from controlled crosses performed better than the clones selected from natural populations. The trial validated the suitability of natural populations for use as gene sources for intraspecific hybridization and as sources of clones with traits comparable with those of interspecific clones. These new P. nigra clones can replace allochthonous clones in areas where autochthonous P. nigra populations are threatened by introgression.

Portuguese Pinus nigra J.F. Arnold populations: genetic diversity, structure and relationships inferred by SSR markers

Pinus nigra J.F. Arnold has an ecological and economic interest in Europe, but many of the planted populations have an unknown origin and infraspecific taxonomy. Six Portuguese P. nigra populations characterised with microsatellites revealed high intra-population diversity structured into two clusters with low differentiation that might suggest two provenances or infraspecific taxa. Despite compared with foreign samples from different subspecies, we were not able to infer about the origin or infraspecific taxonomy of the Portuguese populations based on the pooled microsatellite data . Many of the European Pinus nigra J.F. Arnold forests were planted with the material of unknown origin. Efforts have been made to determine their provenances and infraspecific taxonomy regarding their relevance for defining strategies of genetic resources conservation, germplasm use, forest management and genetic improvement. The Portuguese P. nigra populations are allochthonous, and their provenance and infraspecific taxonomy are unknown. With this work, we intended to characterise the Portuguese P. nigra populations regarding its genetic diversity, structure and relationships using simple sequence repeat (SSR) markers and/or to infer about its origin and infraspecific taxonomy by comparing the SSR patterns of foreign P. nigra samples of known taxonomic classification. A total of 224 Portuguese P. nigra individuals from six populations were characterised using 14 SSR markers developed specifically to different Pinus sp., including P. nigra, by other authors. Thirteen SSR loci were selected and showed 100% of polymorphism among individuals. The genetic diversity was higher within (95%) rather than among (5%) populations. The Portuguese individuals were structured into two main clusters (K = 2) with low genetic differentiation (FST = 0.04), and the foreign samples were genetically distant from the Portuguese individuals. The six Portuguese P. nigra populations revealed high genetic diversity and seemed to be structured into two main clusters with low differentiation suggesting two provenances or infraspecific taxa. Nonetheless, the comparative analyses with foreign samples did not allow a clear inference about its origin and/or infraspecific taxonomy. Additional foreign samples and/or molecular markers will be tested to pursue these goals.

Seed osmopriming with PEG solutions in seeds of three infraspecific taxa of Pinus nigra: Impacts on germination, mitosis and nuclear DNA

A phenological characterisation of the Portuguese Pinus nigra stands performed in the 1980s considered them as belonging to subspecies laricio, salzmanni and nigra. Recently, six allochthonous P. nigra populations that represent the actual species distribution in Portugal were molecularly characterised and showed high genetic similarity to subsp. laricio vars. corsicana and calabrica, and genetic distance to subsp. salzmanni. P. nigra has a hard natural regeneration, and this problem will be enhanced under the more severe and frequent drought episodes projected to Europe. In this work, seeds of the P. nigra infraspecific taxa previously assigned to Portugal were osmoprimed with 10% and 20% polyethylene glycol (PEG) solutions to mimic water stress, and to analyse its impacts on germination, mitosis, and nuclear DNA of young needles. Hydroprimed seeds and resulting plantlets were used as controls. The osmotic stress imposed to the seeds delayed the germination in most of the cases, induced cell cycle anomalies, and caused DNA damage in needles. These impacts were more pronounced in subsp. laricio var. corsicana. The detection of osmotic stress effects from germination to the juvenile plantlet stage suggested a stress memory transmission between plant tissues. The 20% PEG osmopriming performed in var. corsicana seeds was lethal. Globally, this preliminary work suggested a differential water stress tolerance among the three P. nigra infraspecific taxa that should be exploited further, and provided probable explanations for their reduced natural regeneration and early mortality of pine seedlings that compromise afforestation/reforestation programs in Portugal and abroad.

A new approach to study local adaptation in long‐lived woody species: Virtual transplant experiments

Abstract Despite the importance of local adaptation and the extended literature that has addressed it, there are few methods available to explore local adaptation across large temporal scales. However, long‐term patterns are likely to be essential to understanding adaptation in long‐lived species, such as trees. Here, we propose a methodology named ‘virtual transplant experiment' (VTE), which uses long‐term climatic variability to explore local adaptation to climate in natural tree populations. VTEs evaluate the historical response of populations to their local climate and to climates representative of conditions in other populations. We tested our methodology using simulated data and applied it in two case studies on: (a) Pinus nigra populations at the edge of the species distribution, where previous research has suggested strong climate adaptation, and (b) Fagus sylvatica mesic populations, where parallel experiments showed no adaptation to macroclimate. VTE results from simulated and real‐world data matched our expectations, suggesting that the method accurately identified the patterns of local adaptation to climate in tree populations. VTEs consistently discriminated locally adapted populations in synthetic data with a known degree of local adaptation. As expected, P. nigra populations showed adaptation to local climate in the VTE, while F. sylvatica populations showed no overall local advantage. Our method provides a new way to test for local adaptation over time scales encompassing the complete lifespan of trees. VTEs can complement current methods to study local adaptation by adding the ability to explore the long‐term response to local climate in natural populations. The advantages and limitations of the different approaches to studying local adaptation stress the importance of combining multiple approaches to test for local adaptation in long‐lived organisms.

Genetic diversity and structure of Populus nigra populations in two highly fragmented river ecosystems from Turkey

European black poplar (Populus nigra L.) is an important tree species in terms of social, economic, and ecological interest in Turkey. Although large poplar plantations meet the needs of the economy, natural genetic resources of the species have been highly degraded due to anthropogenic effects such as overexploitation and habitat fragmentations. To assess genetic diversity and structure of fragmented populations, 124 naturally distributed European black poplar trees from two major rivers (Kizilirmak and Goksu) in Turkey were sampled and screened by using 20 nuclear microsatellite DNA loci. To detect the possibility of natural hybridization, 10 reference Populus deltoids L. trees were studied with six microsatellite loci. Out of 124, five trees were determined as F2 hybrids with diagnostic and informative alleles. Studied populations appear to have experienced a recent bottleneck event which is likely to cause to reduction in allelic diversity and to increase heterozygosity (mean Ho = 0.80). Four populations representing upstream, middle and downstream parts of the Kizilirmak River were found to be differentiated from Goksu river population, evidenced by genetic differentiation (FST = 0.06), geographical distances in principal coordinate analysis and clustering pattern in structure analysis. Traditional management of European black poplar coupled with bottleneck and hybridization events has played an important role in reduced genetic diversity and degradation of the genetic resources of the species in two river systems. The study has provided invaluable information to prevent further genetic degradation, to maintain existing genetic diversity of the species in its natural habitats, and to implement efficient conservation strategies and breeding programs for future generations.

Morpho-physiological variability of Pinus nigra populations reveals climate-driven local adaptation but weak water use differentiation

Disentangling patterns of intra-specific changes in morpho-physiological traits is crucial for understanding the capacity of tree populations to cope with human-induced environmental changes. This study combined well-established phenotyping techniques and unmanned aerial vehicle (UAV) imagery to characterise the extent of intra-specific variation for an array of meaningful traits among 18 populations of Pinus nigra growing in a common-garden experiment in central Spain, subject to summer drought. Data for eight traits describing above-ground growth, intrinsic water-use efficiency, water uptake patterns and reserve accumulation were obtained for 210 adult individuals belonging to the subspecies laricio, calabrica, nigra and salzmanii. UAV imagery was used to derive seven vegetation indices describing canopy structure and photosynthetic pigments. A strong inter-population differentiation arising from adaptation to cold and continental conditions at the geographical origin of the populations was found for growth traits, reserve accumulation, chlorophyll concentration and leaf surface area. Fast-growing populations, originating from milder climates, emerged in contrast to slow-growing populations, originating from colder and more continental areas of the species range. The latter were characterised by higher leaf chlorophyll concentration and higher investment in reserves. Inter-population variation was highly structured at the subspecies level. Subspecies laricio and calabrica were characterised by a higher growth investment, but diverged in relative radial to primary growth allometry, whereas subspecies nigra and salzmanii showed the highest investment in reserves. Importantly, variation of traits related to water economy was negligible, both at the population and subspecies level, indicating that Mediterranean populations of P. nigra may lack specific adaptation to drought stress. These results provided valuable information in forecasting the performance of this species in the context of climate change. Specifically, they anticipated the potential vulnerability of Mediterranean populations of P. nigra to future reduction in water availability.

Lack of local adaptation to the establishment conditions limits assisted migration to adapt drought-prone Pinus nigra populations to climate change

Abstract The intentional movement of tree genotypes, or assisted migration, is an operational approach proposed to adapt forest management to climate change. Assisted migration assumes that tree populations are locally adapted to environmental conditions, but this fact should be tested specifically. In this study, both a reciprocal transplant and a common garden experiment were carried out to test local adaptation to variable environmental conditions of seedling emergence and survival of the tree species Pinus nigra. Reciprocal sowing experiments involved the cross-sowing of four seed origins among four destination habitats, located in high- and low-altitude sites within central and peripheral populations of Pinus nigra. Evidence of local adaptation was taken to be a significant destination x origin interaction. Then, the possibility of local adaptation was further evaluated under the ‘‘local versus foreign’’ and the ‘‘home versus away’’ criteria. Results showed negative evidence of local adaptation to the emergence and survival environment faced by Pinus nigra seedlings, which would reduce the utility of assisted migration as an effective tool to adapt forests to ongoing climate change.

Above- and belowground responses of Populus nigra L. to mechanical stress observed on the Allier River, France

Pioneer riparian trees such as Populus nigra L. which establish on alluvial bars within dynamic riparian corridors strongly influence fluvial geomorphology by trapping sediments and constructing landforms during floods. The engineering effects (changes in the physical state of the habitat by organisms) of P. nigra on alluvial bars depend on its biomass and its exposure to mechanical stress. P. nigra has a strong phenotypic plasticity that enables individuals to adapt their morphological and biomechanical traits, according to the local hydrogeomorphic conditions. The comprehension and quantification of the variation of morphological and biomechanical response trait attributes of P. nigra populations according to their exposure to mechanical stress is fundamental to better understand why riparian plants are capable to impact fluvial geomorphology. In an empirical in situ study, we quantified the relation between response trait attributes of P. nigra and its exposure to three different levels of mechanical stress. At a highly exposed bar-head, plants clearly developed response traits such as small flexible stems and a strong root system which favour higher mechanical resistance, while at the less exposed bar-tail plants developed taller, less flexible stems and finer root systems. Plants that established in the lower reach of the chute channel developed some common trait attributes in comparison to the bar-tail population and some other trait attributes which were common to the bar-head population. Poplar plants which established on bar-tails favoured bioconstruction, and thus are potentially faster disconnected from hydrogeomorphic disturbances. These results further suggest that fine scale biogeomorphic feedbacks have an influence on larger scale processes within the fluvial corridor requiring hierarchical biogeomorphic bottom-up and top-down cross scale studies for a better understanding of complex biogeomorphic fluvial ecosystems.