Hybridization in contact zone between temperate European pine species

Hybridization studies are important to advance our understanding of the interspecific gene flow and its evolutionary consequences in closely related species. Hybridization and admixture patterns were assessed in a contact zone and reference populations of European pine species using sequence data from 26 nuclear genes and a species-diagnostic cpDNA marker. Reference populations formed three distinct genetic clusters comprising Pinus sylvestris, Pinus mugo/Pinus uliginosa, and Pinus uncinata. Evidence of population structure was found only in P. uliginosa. Based on phenotypic characteristics and molecular data, we identified five groups of individuals in the contact zone in Poland, comprising forms of the parental species and intermediates that were most probably the result of interspecific crosses. A combination of nuclear gene sequence data and a diagnostic organelle marker were used to show that hybridization is frequent in the contact zone and results in hybrid trees with distinct phenotypic identity. The influence of selection in maintaining hybrid phenotypes in environments unsuited to parental species was inferred from nucleotide polymorphism data. A lack of admixture in reference populations suggests that hybridization has not occurred during post-glacial migration and so the contact zone represents a distinct, active example of ongoing evolution. Pine populations in this zone will be a valuable system for studying the genetic basis of hybrid advantage in environmental conditions untypical of pure parental species.     

Genome-wide detection of genetic loci triggering uneven descending of gametes from a natural hybrid pine

Marker transmission ratio distortion (TRD) revealed in genetic mapping studies on distant crosses can be used to infer the genetic basis relating to reproductive barriers between species. Unlike measuring the degree of TRD by the overall number of segregation distorted markers in the affected genome regions, mapping the segregation distorting loci (SDL) provides reliable statistic parameters that help to confine the target genomic regions for further characterization at molecular level. Using the linkage map constructed for a natural hybrid of Pinus hwangshanensis and Pinus massoniana, we perform SDL analyses and align the established map to the loblolly pine consensus map. Altogether, six SDLs with relatively strong LOD supports are detected on four linkage groups of the established map. Since gametes inheriting different alternate chromatid blocks from the SDL affecting genome regions have uneven chance to descend to the offspring, the corresponding genome regions are supposed to play more significant roles in rendering the reproductive isolations between P. hwangshanensis and P. massoniana. This paper presents a case study on a crucial step for uncovering the hidden genetic factors that trigger the uneven descending of gametes in a natural hybrid pine.     

Mountain pine beetle host-range expansion threatens the boreal forest

The current epidemic of the mountain pine beetle (MPB), an indigenous pest of western North American pine, has resulted in significant losses of lodgepole pine. The leading edge has reached Alberta where forest composition shifts from lodgepole to jack pine through a hybrid zone. The susceptibility of jack pine to MPB is a major concern, but there has been no evidence of host-range expansion, in part due to the difficulty in distinguishing the parentals and their hybrids. We tested the utility of a panel of microsatellite loci optimized for both species to classify lodgepole pine, jack pine and their hybrids using simulated data. We were able to accurately classify simulated individuals, and hence applied these markers to identify the ancestry of attacked trees. Here we show for the first time successful MPB attack in natural jack pine stands at the leading edge of the epidemic. This once unsuitable habitat is now a novel environment for MPB to exploit, a potential risk which could be exacerbated by further climate change. The consequences of host-range expansion for the vast boreal ecosystem could be significant.     

Ecological-cenotic role of phytogenous fields of Scots pine on coal dumps

Transformation of ecological factors on dumps of coal mines under the effect of Pinus sylvestris L. results in formation of three-zone phytogenous fields. The under-crown zone is characterized by a leveled temperature regime, low illumination, forest litter accumulation, and formation of abundant undergrowth. In the sufficiently moistened transitional zone, well-developed moss cover is formed, and the undergrowth occurrence is very low. The external zone, transitional to the background meadow communities, is characterized by well-formed grass cover, an abundance of species, and a group pattern of the undergrowth of P. sylvestris L. The reaction of herbaceous plants on the effect of phytogenous pine fields may be positive (adaptive) or negative. Most species are characterized by a negative reaction.     

Identifying southern yellow pine cross sections from the southeastern United States using quadratic discriminant analysis on pith and second annual ring diameters

Southern yellow pine specimens collected from historical structures, stumps, and coarse woody debris in forests have been difficult to identify at the species level due to similar wood anatomy. This can be problematic for dendrochronologists when identifying the correct species used in the construction of historical structures, or reconstructing forest history on the landscape and using those specimens in the context of that history. We applied a quadratic discriminant analysis (QDA) to update a century-old method plotting pith diameters against second annual ring diameters to discern one species of southern yellow pine from others. Our analysis estimates error rates for false positive and false negative determinations when comparing longleaf pine (Pinus palustris Mill.) to shortleaf (Pinus echinata Mill.) and loblolly pine (Pinus taeda L.). The cross-validated false positive error rates for the smallest dataset (n = 46), was nearly twice (9.52%) that determined as a simple proportion by counting errant observations (4.76%). QDA of the largest dataset (n = 206) gave a flatter zero contour and false positive rate (3.13%) like the proportionally determined value (1.56%), despite one additional observation being falsely assigned to longleaf pine by QDA. An unknown, unearthed southern pine specimen from southeastern Virginia was radiocarbon dated up to 500 years prior and assigned as longleaf by our method (probability ≥ 0.9998). Thus, through a QDA, it is possible to greatly improve confidence in identifications of key unknown specimens that can provide evidence of discerning one species, longleaf pine, from other southern yellow pines.     

Degree of Hybridization in Seed Stands of Pinus engelmannii Carr. In the Sierra Madre Occidental,Durango, Mexico

Hybridization is an important evolutionary force, because interspecific gene transfer can introduce more new genetic material than is directly generated by mutations. Pinus engelmannii Carr. is one of the nine most common pine species in the pine-oak forest ecoregion in the state of Durango, Mexico. This species is widely harvested for lumber and is also used in reforestation programmes. Interspecific hybrids between P.engelmannii and Pinus arizonica Engelm. have been detected by morphological analysis. The presence of hybrids in P. engelmannii seed stands may affect seed quality and reforestation success. Therefore, the goals of this research were to identify introgressive hybridization between P. engelmannii and other pine species in eight seed stands of this species in Durango, Mexico, and to examine how hybrid proportion is related to mean genetic dissimilarity between trees in these stands, using Amplified Fragment Length Polymorphism (AFLP) markers and morphological traits. Differences in the average current annual increment of putative hybrids and pure trees were also tested for statistical significance. Morphological and genetic analyses of 280 adult trees were carried out. Putative hybrids were found in all the seed stands studied. The hybrids did not differ from the pure trees in vigour or robustness. All stands with putative P. engelmannii hybrids detected by both AFLPs and morphological traits showed the highest average values of the Tanimoto distance, which indicates: i) more heterogeneous genetic material, ii) higher genetic variation and therefore iii) the higher evolutionary potential of these stands, and iv) that the morphological differentiation (hybrid/not hybrid) is strongly associated with the Tanimoto distance per stand. We conclude that natural pairwise hybrids are very common in the studied stands. Both morphological and molecular approaches are necessary to confirm the genetic identity of forest reproductive material.     

High-throughput genotyping and mapping of single nucleotide polymorphisms in loblolly pine (Pinus taeda L.)

The development and application of genomic tools to loblolly pine (Pinus taeda L.) offer promising insights into the organization and structure of conifer genomes. The application of a high-throughput genotyping assay across diverse forest tree species, however, is currently limited taxonomically. This is despite the ongoing development of genome-scale projects aiming at the construction of expressed sequence tag (EST) libraries and the resequencing of EST-derived unigenes for a diverse array of forest tree species. In this paper, we report on the application of Illumina’s high-throughput GoldenGate™ SNP genotyping assay to a loblolly pine mapping population. Single nucleotide polymorphisms (SNPs) were identified through resequencing of previously identified wood quality, drought tolerance, and disease resistance candidate genes prior to genotyping. From that effort, a 384 multiplexed SNP assay was developed for high-throughput genotyping. Approximately 67% of the 384 SNPs queried converted into high-quality genotypes for the 48 progeny samples. Of those 257 successfully genotyped SNPs, 70 were segregating within the mapping population. A total of 27 candidate genes were subsequently mapped onto the existing loblolly pine consensus map, which consists of 12 linkage groups spanning a total map distance of 1,227.6 cM. The ability of SNPs to be mapped to the same position as fragment-based markers previously developed within the same candidate genes, as well as the pivotal role that SNPs currently play in the dissection of complex phenotypic traits, illustrate the usefulness of high-throughput SNP genotyping technologies to the continued development of pine genomics. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Habitat indicators for cavity-nesters: The polypore Phellinus pini in pine forests

Foresters and arborists have long used fruit-bodies of heart-rot fungi as signs of advanced live-tree decay, but such usage has not been elaborated for forest conservation. I analysed relationships between a heart-rot fungus, tree-cavity supply, and cavity-nesting bird assemblage in wet hemiboreal Scots pine (Pinus sylvestris) forests in Estonia. The focal species, Phellinus pini, is the main heartwood decayer of live pines; it typically forms fruit-bodies at the stage of advanced decay on old trees. I found that the pine wetlands had few tree-cavities (mostly in snags) and cavity-nesting birds (woodpeckers being almost absent) despite abundant snag supply. Only one fruit-body of P. pini was found on cavity-tree but stand-scale abundance of the fruit-bodies correlated well with cavity-nester densities. Multifactor models indicated that cavity formation, not tree death, was the limiting process for secondary cavity-nesters, and P. pini could indeed be used (in combination with old-pine abundance) for assessing their habitat quality. This fungus could also serve as an educational flagship species to bridge conservation biology and forest pathology, and its fruit-bodies can signal trees to be retained at harvesting in pine forests. The conclusion is that there is hope for developing practical indicators to manage for the hidden decay processes that govern tree-cavity development.     

Development of secondary pine forests after pine wilt disease in western Japan

Abstract. The development of secondary Pinus densiflora (Japanese red pine) forests after pine wilt disease was studied through phytosociological analysis, estimation of forest structure before disease and size-structure, tree ring and stem analyses. Following the end of the disease, the growth of previously suppressed small oak trees was accelerated. This is quite different from the development of forests following fire, which starts with the establishment of pine seedlings. Pine wilt disease shifted the dominance of secondary forests from Pinus densiflora to Quercus serrata oak forest. In pine forests, disturbance by fire is important for forest maintenance. In contrast, disturbance by pine wilt disease leads to an acceleration of succession from pine forest to oak forest.     

Impact of groundwater salinity on vegetation species richness in the coastal pine forests and wetlands of Ravenna,Italy

In the coastal pine forests (Pinus pinea and Pinus pinaster) of Ravenna (Italy) along the Adriatic coast, many pine trees are stressed or dying. In this paper we present ground elevation, depth to watertable, salinity of groundwater and vegetation species richness data within one of the coastal pine forests and some wetlands north of the Bevano River between LAT. 44°23′10″ and LAT. 44°20′21″ and between LONG. 12°17′25″ and LONG. 12°19′33″. The data are presented areally and along a 50 m long transect perpendicular to the coast to study the cause of distress in the pine forest and in different water pools within the wetlands. The findings were compared to published values of tolerance to salinity for 39 plant species typical of the area and incorporated into a web application to help nature managers in assessing or adjusting water salinity in relation to the vegetation species present. The pine trees are relatively tolerant to salinity (up to 12 g/l) but cannot survive a shallow watertable. On the other hand, species richness or biodiversity in this area is promoted by a shallow watertable and low salinity.     

Abiotic factors modulate post-drought growth resilience of Scots pine plantations and rear-edge Scots pine and oak forests

The proportion of planted forests in the Mediterranean Basin is one of the largest in the world. These plantations are dominated by pine species and present a series of characteristics such as low elevation, high competition or small tree size that make them more vulnerable to droughts. However, quantitative assessments of their post-drought growth resilience in accordance with species, site factors and tree characteristics are lacking. In this study we sampled 164 trees at four forest sites located in the drought-prone Sierra Nevada, southeastern Spain. We compared growth responsiveness to drought in rear-edge planted vs. relic natural Scots pine (Pinus sylvestris) and coexisting Pyrenean oak (Quercus pyrenaica) stands. Our objective was to characterize and compare the different growth responses to drought between species and sites and the effect of the main physiographic factors (altitude, aspect, and slope) on these responses since the influence of these factors on post-drought resistance and resilience has received little attention to date. Our results reveal that the planted pine sites with the lowest mean growth rates displayed greater resistance during drought, and that higher altitude was associated with improved resistance and/or resilience for all species and sites. Natural pine and Pyrenean oak stands were better adapted to the dry climatic conditions of the Mediterranean region where the study was undertaken, displaying greater resistance and/or resilience and lower influence of drought on growth in comparison to stands of planted pines. These results suggest that promoting the conservation of high-elevation pine plantations and enhancing the regeneration of natural pine and oak may improve the resistance and resilience of these drought-prone forest ecosystems.     

Seed screening of three pine species for glyphosate sensitivity for forest restoration

Austrian black pine (Pinus nigra J.F. Arnold), Scots pine (Pinus sylvestris L.), and maritime pine (Pinus pinaster Aiton) are commonly used in restoration practices in the Mediterranean base including Turkey. Direct seeding can secure desired level of tree establishment and survival on degraded sites wherever, favorable safe sites are scattered throughout the landscape. Glyphosate is a commonly used herbicide for weed control in forest, nursery and restoration sites worldwide, due to its broad-spectrum efficacy and considerably less toxicity on the environment compared to other chemicals. The present study screened the glyphosate phytotoxicity of three dominant pine species in Turkey during a seed germination trial, after seeds had been presoaked in 15 different dose-glyphosate solutions varying between 0 and 5%, v:v. Glyphosate applications damaged seed germination speed more than cumulative germination rate. As a systemic herbicide, glyphosate appeared highly phytotoxic to Austrian black pine. Scots pine showed an intermediate glyphosate phytotoxicity. Maritime pine was the least sensitive species, tolerating glyphosate at ≤1% doses. In conclusion, glyphosate may be used at low doses on restoration sites seeded with maritime pine while it is not recommended to be used on degraded sites seeded with Austrian black pine and Scots pine.     

Cross-species amplification and characterization of microsatellite loci in Pinus mugo Turra

Pinus mugo (dwarf mountain pine) is an important component of European mountain ecosystems. However, little is known about the present genetic structure and population differentiation of this species at the DNA level, possibly due to a lack of nuclear microsatellite markers (SSR) developed for Pinus mugo. Therefore in this study we transferred microsatellite markers originally developed for Pinus sylvestris and Pinus taeda to Pinus mugo. This cross-species amplification approach is much faster and less expensive than isolation and characterization of new microsatellite markers. The transfer rates from the source species to Pinus mugo were moderately low (26%). There were no differences in microsatellite repeat motifs between the source species and Pinus mugo. Nuclear microsatellite markers successfully transferred to Pinus mugo can be applied to various genetic studies on this species, due to the high level of their polymorphism and high value of polymorphic information content.     

Ecogeographical characteristics of the seed-bearing capacity and natural regeneration of pine on the fire-sites in pine forests of Transbaikalia

The paper presents the results of the studying of the parameters of post-fire structure and seed-bearing capacity of tree stands, factors of surface medium (thickness of burnt duff, projective cover of herb and moss vegetation) as well as number, vitality, and age structure of self-seeded Scots pine (Pinus sylvestris L.) and accompanying small-leaved species in the Lower Selenga pine forest massif of the forest-steppe in Southwestern Transbaikalia. The seed harvests were 1.5–2 times higher than in the geographically replacing forest types in the forest-steppe of West Siberia, and vitality of the undergrowth of the pine under the canopy of fire-affected stands was extremely low. It is shown that the pine reforests successfully on the fire-sites in the zone of insemination from the forest walls and on the thin fire-sites in the cowberry-rhododendron pine forests, where it is 2–3 times more abundant than in forest-steppe of the West Siberia. The reforestation is insufficient on the fire-sites in the bearberry-lichen pine forests.     

Primers designed to amplify a mitochondrial nad1 intron in ponderosa pine, Pinus ponderosa, limber pine, P. flexilis, and Scots pine, P. sylvestris

The b/c intron of the mitochondrial nad1 gene, was sequenced to characterize the indel region of ponderosa pine, Pinus ponderosa. The sequence in ponderosa pine was aligned with the sequence in Scots pine, Pinus sylvestris, to design seven primers that are useful for sequencing and for revealing size variation in amplified fragments in ponderosa pine, Scots pine, and limber pine, Pinus flexilis. These primers reveal variability in all three species, and the pattern of variability within ponderosa pine is described by a preliminary survey. The indel region of ponderosa pine contains three distinct elements with lengths of 31, 32, and 34 bp. Received: 1 March 2000 / Accepted: 14 April 2000<@head-com-p1a.lf>Communicated by P.M.A. Tigerstedt     

Taxonomic Identification of Mediterranean Pines and Their Hybrids Based on the High Resolution Melting (HRM) and trnL Approaches: From Cytoplasmic Inheritance to Timber Tracing

Fast and accurate detection of plant species and their hybrids using molecular tools will facilitate the assessment and monitoring of local biodiversity in an era of climate and environmental change. Herein, we evaluate the utility of the plastid trnL marker for species identification applied to Mediterranean pines (Pinus spp.). Our results indicate that trnL is a very sensitive marker for delimiting species biodiversity. Furthermore, High Resolution Melting (HRM) analysis was exploited as a molecular fingerprint for fast and accurate discrimination of Pinus spp. DNA sequence variants. The trnL approach and the HRM analyses were extended to wood samples of two species (Pinus nigra and Pinus sylvestris) with excellent results, congruent to those obtained using leaf tissue. Both analyses demonstrate that hybrids from the P. brutia (maternal parent) × P. halepensis (paternal parent) cross, exhibit the P. halepensis profile, confirming paternal plastid inheritance in Group Halepensis pines. Our study indicates that a single one-step reaction method and DNA marker are sufficient for the identification of Mediterranean pines, their hybrids and the origin of pine wood. Furthermore, our results underline the potential for certain DNA regions to be used as novel biological information markers combined with existing morphological characters and suggest a relatively reliable and open taxonomic system that can link DNA variation to phenotype-based species or hybrid assignment status and direct taxa identification from recalcitrant tissues such as wood samples.     

Bird assemblages in pine plantations replacing native ecosystems in NW Patagonia

Forest plantations of exotic conifers represent an important economic activity in NW Patagonia, Argentina. However, there is a remarkable lack of information on the impact of forestry on native biodiversity. We analyzed the effect of Pinus ponderosa plantations on bird communities, considering different stand management practices (dense and sparse tree covers), and different landscape contexts where they are planted (Austrocedrus chilensis forest and steppe). Ultimately we wished to assess in which way plantations may be designed and managed to improve biodiversity conservation. Bird richness and abundance did not change significantly in the steppe, although community composition did, and was partially replaced by a new community, similar to that of ecotonal forests. In contrast, in the A. chilensis forest areas, species richness decreased in dense plantations, but bird community composition remained relatively constant when replacing the native forest with pine plantations. Also, in A. chilensis forest, stand management practices aiming at maintaining low tree densities permit the presence of many bird species from the original habitat. In the steppe area in turn, both dense and sparse plantations are unsuitable for most steppe species, thus it is necessary to manage them at higher scales, maintaining the connectivity of the native matrix to prevent the fragmentation of bird populations. We conclude that pine plantations can provide habitat for a substantial number of native bird species, and this feature varies both with management practices and with the landscape context of areas where afforestation occurs.     

The genetics of shortleaf pine (<Emphasis Type="Italic">Pinus echinata</Emphasis> mill.) with implications for restoration and management

Shortleaf pine (Pinus echinata Mill.) is an important commercial timber resource and forest ecosystem component in the southeastern USA. The species occurs in mainly drier sites as an early- to mid-successional species, is fire-adapted, and it plays an important role in the fire ecology of the region. However, shortleaf pine genetics are not well-studied, especially in this era of molecular genetics and genomics. Most genetics research about the species has focused on provenance testing. Generally, shortleaf pine performs well in colder areas, when compared to loblolly pine (Pinus taeda L.), a close relative, which is faster growing and the most common plantation species in the region. Though not as advanced in genetic improvement as loblolly pine, tree breeders have improved shortleaf pine in one to two generations of selection, and diverse, genetically improved shortleaf pine materials are available to foresters and landowners throughout the southeastern USA. Researchers have also studied the genetic variation of shortleaf pine using various molecular markers and have found that shortleaf pine is generally a prolific outcrosser, a trait it shares with other non-isolated members of the family Pinaceae. In recent years, however, it has shared less genetic material across long ranges, probably because of habitat fragmentation. Various anthropogenic factors also affect shortleaf pine’s future, as recent studies show that shortleaf pine introgression with loblolly pine puts the species—and the resiliency of southeastern forests—at risk. Importantly, fire exclusion is a likely cause of the increase in introgression. Herein, we provide further details and up-to-date genetic information and resources for foresters and ecologists interested in the restoration and management of shortleaf pine.