Gluten-induced RNA methylation changes regulate intestinal inflammation via allele-specific XPO1 translation in epithelial cells.

OBJECTIVES: Coeliac disease (CD) is a complex autoimmune disorder that develops in genetically susceptible individuals. Dietary gluten triggers an immune response for which the only available treatment so far is a strict, lifelong gluten free diet. Human leucocyte antigen (HLA) genes and several non-HLA regions have been associated with the genetic susceptibility to CD, but their role in the pathogenesis of the disease is still essentially unknown, making it complicated to develop much needed non-dietary treatments. Here, we describe the functional involvement of a CD-associated single-nucleotide polymorphism (SNP) located in the 5'UTR of XPO1 in the inflammatory environment characteristic of the coeliac intestinal epithelium. DESIGN: The function of the CD-associated SNP was investigated using an intestinal cell line heterozygous for the SNP, N6-methyladenosine (m6A)-related knock-out and HLA-DQ2 mice, and human samples from patients with CD. RESULTS: Individuals harbouring the risk allele had higher m6A methylation in the 5'UTR of XPO1 RNA, rendering greater XPO1 protein amounts that led to downstream nuclear factor kappa B (NFkB) activity and subsequent inflammation. Furthermore, gluten exposure increased overall m6A methylation in humans as well as in in vitro and in vivo models. CONCLUSION: We identify a novel m6A-XPO1-NFkB pathway that is activated in CD patients. The findings will prompt the development of new therapeutic approaches directed at m6A proteins and XPO1, a target under evaluation for the treatment of intestinal disorders.

Plant-herbivore interactions in a trispecific hybrid swarm of Populus: assessing support for hypotheses of hybrid bridges, evolutionary novelty and genetic similarity.

UNLABELLED: Natural systems of hybridizing plants are powerful tools with which to assess evolutionary processes between parental species and their associated arthropods. Here we report on these processes in a trispecific hybrid swarm of Populus trees. Using field observations, common garden experiments and genetic markers, we tested the hypothesis that genetic similarities among hosts underlie the distributions of 10 species of gall-forming arthropods and their ability to adapt to new host genotypes. KEY FINDINGS: the degree of genetic relatedness among parental species determines whether hybridization is primarily bidirectional or unidirectional; host genotype and genetic similarity strongly affect the distributions of gall-forming species, individually and as a community. These effects were detected observationally in the wild and experimentally in common gardens; correlations between the diversity of host genotypes and their associated arthropods identify hybrid zones as centres of biodiversity and potential species interactions with important ecological and evolutionary consequences. These findings support both hybrid bridge and evolutionary novelty hypotheses. However, the lack of parallel genetic studies on gall-forming arthropods limits our ability to define the host of origin with their subsequent shift to other host species or their evolution on hybrids as their final destination.

Contrasting patterns of genetic diversity across the ranges of Pinus monticola and P. strobus: a comparison between eastern and western North American postglacial colonization histories.

UNLABELLED: • Premises of the study: Understanding the influence of recent glacial and postglacial periods on species' distributions is key for predicting the effects of future environmental changes. We investigated the influence of two physiographic landscapes on population structure and postglacial colonization of two white pine species of contrasting habitats: P. monticola, which occurs in the highly mountainous region of western North America, and P. strobus, which occurs in a much less mountainous area in eastern North America.• METHODS: To characterize the patterns of genetic diversity and population structure across the ranges of both species, 158 and 153 single nucleotide polymorphism (SNP) markers derived from expressed genes were genotyped on range-wide samples of 61 P. monticola and 133 P. strobus populations, respectively.• KEY RESULTS: In P. monticola, a steep latitudinal decrease in genetic diversity likely resulted from postglacial colonization involving rare long-distance dispersal (LDD) events. In contrast, no geographic patterns of diversity were detected in P. strobus, suggesting recolonization via a gradually advancing front or frequent LDD events. For each species, structure analyses identified two distinct southern and northern genetic groups that likely originated from two different glacial lineages. At a finer scale, and for the two species, smaller subgroups were detected that could be remnants of cryptic refugia.• CONCLUSION: During postglacial colonization, the western and eastern North American landscapes had different impacts on genetic signatures in P. monticola compared with P. strobus. We discuss the importance of our findings for conservation programs and predictions of species' response to climate change.

A cryptic syngameon within Betula shrubs revealed: Implications for conservation in changing subarctic environments.

Arctic and subarctic ecosystems are rapidly transforming due to global warming, emphasizing the need to understand the genetic diversity and adaptive strategies of northern plant species for effective conservation. This study focuses on Betula glandulosa, a native North American tundra shrub known as dwarf birch, which demonstrates an apparent capacity to adapt to changing climate conditions. To address the taxonomic challenges associated with shrub birches and logistical complexities of sampling in the northernmost areas where species' ranges overlap, we adopted a multicriteria approach. Incorporating molecular data, ploidy level assessment and leaf morphology, we aimed to distinguish B. glandulosa individuals from other shrub birch species sampled. Our results revealed three distinct species and their hybrids within the 537 collected samples, suggesting the existence of a shrub birch syngameon, a reproductive network of interconnected species. Additionally, we identified two discrete genetic clusters within the core species, B. glandulosa, that likely correspond to two different glacial lineages. A comparison between the nuclear and chloroplast SNP data emphasizes a long history of gene exchange between different birch species and genetic clusters. Furthermore, our results highlight the significance of incorporating interfertile congeneric species in conservation strategies and underscores the need for a holistic approach to conservation in the context of climate change, considering the complex dynamics of species interactions. While further research will be needed to describe this shrub birches syngameon and its constituents, this study is a first step in recognizing its existence and disseminating awareness among ecologists and conservation practitioners. This biological phenomenon, which offers evolutionary flexibility and resilience beyond what its constituent species can achieve individually, may have significant ecological implications.

Nature-based virtual reality intervention to manage stress in family caregivers of allogeneic hematopoietic stem cell transplant recipients: a two-phase pilot study protocol.

Millions of family members and/or friends in the U.S. serve as unpaid caregivers for individuals with chronic conditions, such as cancer. Caregiving for someone undergoing an intense allogeneic hematopoietic stem cell transplant (HSCT) is particularly demanding, with accompanying physical and psychological stress. Increased stress and stress-related symptoms could make it difficult for caregivers to fulfill their roles and could negatively impact the health status and quality of life of themselves and the recipients. Virtual reality (VR) is a promising technology increasingly used for treatment and wellness in various medical settings. There is growing evidence that studies have reported the positive effects of the VR intervention in managing and reducing stress among diverse populations in various clinical scenarios; however, no published studies have focused on family caregivers of patients with cancer. The study aims to assess the feasibility and acceptability of a four-week nature-based VR intervention and to examine the effectiveness of the VR intervention on stress in HSCT caregivers. This study comprises two phases. Phase I of the study will be a single-arm pre-post design focused on assessing the feasibility and acceptability of the VR intervention. Phase II of the study will be a prospective randomized controlled group design to examine the effectiveness of the VR intervention on perceived stress. Adults (≥ 18 years) who serve as primary caregivers for a person who will undergo an allogeneic HSCT will be recruited. Fifteen participants will be enrolled for Phase I and 94 participants for Phase II (Active VR arm N=47; Sham VR arm N=47). The nature-based immersive VR program contains 360° high-definition videos of nature scenes along with nature sounds through a head-mounted display (HMD) for 20 minutes every day for four weeks. Primary outcome is perceived stress measured by the Perceived Stress Scale. Secondary/exploratory outcomes are stress-related symptoms (e.g., fatigue, sleep disturbance) and physiological biomarkers (e.g., cortisol, alpha-amylase). The importance and innovativeness of this study consist of using a first-of-its-kind, immersive VR technology to target stress and investigating the health outcomes assessed by validated objective biomarkers as well as self-report measures of the nature-based intervention in the caregiver population. Clinical trial registration: ClinicalTrials.gov, identifier NCT05909202.

Ask suicide-screening questions to everyone in medical settings: the asQ'em Quality Improvement Project.

BACKGROUND: Suicide in hospital settings is a frequently reported sentinel event to the Joint Commission (JC). Since 1995, over 1,000 inpatient deaths by suicide have been reported to the JC; 25% occurred in non-behavioral health settings. Lack of proper "assessment" was the leading root cause for 80% of hospital suicides. This paper describes the "Ask Suicide-Screening Questions to Everyone in Medical Settings (asQ'em)" Quality Improvement Project. We aimed to pilot a suicide screening tool and determine feasibility of screening in terms of prevalence, impact on unit workflow, impact on mental health resources, and patient/nurse acceptance. METHODS: We piloted the asQ'em two-item screening instrument that assesses suicidal thoughts and behaviors, designed specifically for nurses to administer to medical patients. Educational in-services were conducted. A convenience sample of adult patients, 18 years or older, from three selected inpatient units in the National Institutes of Health Clinical Center, participated. RESULTS: A total of 331 patients were screened; 13 (4%) patients screened "positive" for suicide risk and received further evaluation. No patient had acute suicidal thoughts or required an observational monitor. Screening took approximately 2 minutes; 87% of patients reported feeling comfortable with screening; 81% of patients, 75% of nurses, and 100% of social workers agreed that all patients in hospitals should be screened for suicide risk. DISCUSSION: Nurses can feasibly screen hospitalized medical/surgical patients for suicide risk with a two-item screening instrument. Patients, nurses, and social workers rated their experience of screening as positive and supported the idea of universal suicide screening in the hospital.

Finding common ground: Toward comparable indicators of adaptive capacity of tree species to a changing climate.

Adaptive capacity, one of the three determinants of vulnerability to climate change, is defined as the capacity of species to persist in their current location by coping with novel environmental conditions through acclimation and/or evolution. Although studies have identified indicators of adaptive capacity, few have assessed this capacity in a quantitative way that is comparable across tree species. Yet, such multispecies assessments are needed by forest management and conservation programs to refine vulnerability assessments and to guide the choice of adaptation measures. In this paper, we propose a framework to quantitatively evaluate five key components of tree adaptive capacity to climate change: individual adaptation through phenotypic plasticity, population phenotypic diversity as influenced by genetic diversity, genetic exchange within populations, genetic exchange between populations, and genetic exchange between species. For each component, we define the main mechanisms that underlie adaptive capacity and present associated metrics that can be used as indices. To illustrate the use of this framework, we evaluate the relative adaptive capacity of 26 northeastern North American tree species using values reported in the literature. Our results show adaptive capacity to be highly variable among species and between components of adaptive capacity, such that no one species ranks consistently across all components. On average, the conifer Picea glauca and the broadleaves Acer rubrum and A. saccharinum show the greatest adaptive capacity among the 26 species we documented, whereas the conifers Picea rubens and Thuja occidentalis, and the broadleaf Ostrya virginiana possess the lowest. We discuss limitations that arise when comparing adaptive capacity among species, including poor data availability and comparability issues in metrics derived from different methods or studies. The breadth of data required for such an assessment exemplifies the multidisciplinary nature of adaptive capacity and the necessity of continued cross-collaboration to better anticipate the impacts of a changing climate.

Going with the flow: Intraspecific variation may act as a natural ally to counterbalance the impacts of global change for the riparian species Populus deltoides.

The speed and magnitude of global change will have major impacts on riparian ecosystems, thereby leading to greater forest vulnerability. Assessing species' adaptive capacities to provide relevant information for vulnerability assessments remains challenging, especially for nonmodel species like the North American Populus deltoides W. Bartram ex Marshall. The objective of this study was to understand how genomic diversity of this foundation species was shaped by its environment (climate, soil, and biotic interactions) to gauge its adaptive capacity. We used two complementary approaches to get a full portrait of P. deltoides genetic diversity at both the species and whole-genome ranges. First, we used a set of 93 nuclear and three chloroplastic SNP markers in 946 individuals covering most of the species' natural distribution. Then, to measure the degree of intraspecific divergence at the whole-genome level and to support the outlier and genomic-environment association analyses, we used a sequence capture approach on DNA pools. Three distinct lineages for P. deltoides were detected, and their current distribution was associated with abiotic and biotic variations. The comparison between both cpDNA and ncDNA patterns showed that gene flow between the lineages is unbalanced. The southern and northeastern populations may benefit from the input, through river flow, of novel alleles located upstream to their local gene pools. These alleles could migrate from populations that are already adapted to conditions that fit the predicted climates in the receiving local populations, hotter at the northeastern limit and drier in the Central United States. These "preadapted" incoming alleles may help to cope with maladaptation in populations facing changing conditions.

Glacial vicariance in the Pacific Northwest: evidence from a lodgepole pine mitochondrial DNA minisatellite for multiple genetically distinct and widely separated refugia.

The Canadian side of the Pacific Northwest was almost entirely covered by ice during the last glacial maximum, which has induced vicariance and genetic population structure for several plant and animal taxa. Lodgepole pine (Pinus contorta Dougl. ex. Loud.) has a wide latitudinal and longitudinal distribution in the Pacific Northwest. Our main objective was to identify relictual signatures of glacial vicariance in the population structure of the species and search for evidence of distinct glacial refugia in the Pacific Northwest. A maternally inherited mitochondrial DNA minisatellite-like marker was used to decipher haplotype diversity in 91 populations of lodgepole pine located across the natural range. Overall population differentiation was sizeable (G(ST) = 0.365 and R(ST) = 0.568). Four relatively homogeneous groups of populations, possibly representative of as many genetically distinct glacial populations, were identified for the two main subspecies, ssp. latifolia and ssp. contorta. For ssp. contorta, one glacial lineage is suggested to have been located at high latitudes and possibly off the coast of mainland British Columbia (BC), while the other is considered to have been located south of the ice sheet along the Pacific coast. For ssp. latifolia, two genetically distinct glacial populations probably occurred south of the ice sheet: in the area bounded by the Cascades and Rocky Mountains ranges, and on the eastern side of the Rockies. A possible fifth refugium located in the Yukon may have also been present for ssp. latifolia. Zones of contact between these ancestral lineages were also apparent in interior and northern BC. These results indicate the role of the Queen Charlotte Islands and the Alexander Archipelago as a refugial zone for some Pacific Northwest species and the vicariant role played by the Cascades and the American Rocky Mountains during glaciation.

Case management in primary care for frequent users of healthcare services with chronic diseases and complex care needs: an implementation and realist evaluation protocol.

INTRODUCTION: Significant evidence in the literature supports case management (CM) as an effective intervention to improve care for patients with complex healthcare needs. However, there is still little evidence about the facilitators and barriers to CM implementation in primary care setting. The three specific objectives of this study are to: (1) identify the facilitators and barriers of CM implementation in primary care clinics across Canada; (2) explain and understand the relationships between the actors, contextual factors, mechanisms and outcomes of the CM intervention; (3) identify the next steps towards CM spread in primary care across Canada. METHODS AND ANALYSIS: We will conduct a multiple-case embedded mixed methods study. CM will be implemented in 10 primary care clinics in five Canadian provinces. Three different units of analysis will be embedded to obtain an in-depth understanding of each case: the healthcare system (macro level), the CM intervention in the clinics (meso level) and the individual/patient (micro level). For each objective, the following strategy will be performed: (1) an implementation analysis, (2) a realist evaluation and (3) consensus building among stakeholders using the Technique for Research of Information by Animation of a Group of Experts method. ETHICS AND DISSEMINATION: This study, which received ethics approval, will provide innovative knowledge about facilitators and barriers to implementation of CM in different primary care jurisdictions and will explain how and why different mechanisms operate in different contexts to generate different outcomes among frequent users. Consensual and prioritised statements about next steps for spread of CM in primary care from the perspectives of all stakeholders will be provided. Our results will offer context-sensitive explanations that can better inform local practices and policies and contribute to improve the health of patients with complex healthcare needs who frequently use healthcare services. Ultimately, this will increase the performance of healthcare systems and specifically mitigate ineffective use and costs.

Development of a Traceability System Based on a SNP Array for Large-Scale Production of High-Value White Spruce (Picea glauca).

Biological material is at the forefront of research programs, as well as application fields such as breeding, aquaculture, and reforestation. While sophisticated techniques are used to produce this material, all too often, there is no strict monitoring during the "production" process to ensure that the specific varieties are the expected ones. Confidence rather than evidence is often applied when the time comes to start a new experiment or to deploy selected varieties in the field. During the last decade, genomics research has led to the development of important resources, which have created opportunities for easily developing tools to assess the conformity of the material along the production chains. In this study, we present a simple methodology that enables the development of a traceability system which, is in fact a by-product of previous genomic projects. The plant production system in white spruce (Picea glauca) is used to illustrate our purpose. In Quebec, one of the favored strategies to produce elite varieties is to use somatic embryogenesis (SE). In order to detect human errors both upstream and downstream of the white spruce production process, this project had two main objectives: (i) to develop methods that make it possible to trace the origin of plants produced, and (ii) to generate a unique genetic fingerprint that could be used to differentiate each embryogenic cell line and ensure its genetic monitoring. Such a system had to rely on a minimum number of low-cost DNA markers and be easy to use by non-specialists. An efficient marker selection process was operationalized by testing different classification methods on simulated datasets. These datasets were generated using in-house bioinformatics tools that simulated crosses involved in the breeding program for which genotypes from hundreds of SNP markers were already available. The rate of misidentification was estimated and various sources of mishandling or contamination were identified. The method can easily be applied to other production systems for which genomic resources are already available.

Patient Opinions About Screening for Suicide Risk in the Adult Medical Inpatient Unit.

As hospital clinicians and administrators consider implementing suicide risk screening on medical inpatient units, patient reactions to screening can provide essential input. This post hoc analysis examined patient opinions about screening for suicide risk in the medical setting. This analysis includes a subsample of a larger quality improvement project designed to screen medically hospitalized patients for suicide risk. Fifty-three adult medical inpatients at a clinical research hospital provided opinions about suicide risk screening. A qualitative analysis of responses to an opinion question about screening was conducted to identify major themes. Forty-three (81%) patients supported screening medical inpatients for suicide risk. Common themes emphasized asking patients directly about suicide, connection between mental/physical health, and the role of screening in suicide prevention. Adult medical inpatients supported screening for suicide risk on medical/surgical inpatient units. Behavioral health clinicians are uniquely poised to champion suicide detection and intervention in the general medical hospital setting. Patient opinions can be utilized to inform thoughtful implementation of universal suicide risk screening in the medical setting.

Case management in primary care among frequent users of healthcare services with chronic conditions: protocol of a realist synthesis.

INTRODUCTION: A common reason for frequent use of healthcare services is the complex healthcare needs of individuals suffering from multiple chronic conditions, especially in combination with mental health comorbidities and/or social vulnerability. Frequent users (FUs) of healthcare services are more at risk for disability, loss of quality of life and mortality. Case management (CM) is a promising intervention to improve care integration for FU and to reduce healthcare costs. This review aims to develop a middle-range theory explaining how CM in primary care improves outcomes among FU with chronic conditions, for what types of FU and in what circumstances. METHODS AND ANALYSIS: A realist synthesis (RS) will be conducted between March 2017 and March 2018 to explore the causal mechanisms that underlie CM and how contextual factors influence the link between these causal mechanisms and outcomes. According to RS methodology, five steps will be followed: (1) focusing the scope of the RS; (2) searching for the evidence; (3) appraising the quality of evidence; (4) extracting the data; and (5) synthesising the evidence. Patterns in context-mechanism-outcomes (CMOs) configurations will be identified, within and across identified studies. Analysis of CMO configurations will help confirm, refute, modify or add to the components of our initial rough theory and ultimately produce a refined theory explaining how and why CM interventions in primary care works, in which contexts and for which FU with chronic conditions. ETHICS AND DISSEMINATION: Research ethics is not required for this review, but publication guidelines on RS will be followed. Based on the review findings, we will develop and disseminate messages tailored to various relevant stakeholder groups. These messages will allow the development of material that provides guidance on the design and the implementation of CM in health organisations. TRIAL REGISTRATION NUMBER: Prospero CRD42017057753.

Variations in foliar monoterpenes across the range of jack pine reveal three widespread chemotypes: implications to host expansion of invasive mountain pine beetle.

The secondary compounds of pines (Pinus) can strongly affect the physiology, ecology and behaviors of the bark beetles (Coleoptera: Curculionidae, Scolytinae) that feed on sub-cortical tissues of hosts. Jack pine (Pinus banksiana) has a wide natural distribution range in North America (Canada and USA) and thus variations in its secondary compounds, particularly monoterpenes, could affect the host expansion of invasive mountain pine beetle (Dendroctonus ponderosae), which has recently expanded its range into the novel jack pine boreal forest. We investigated monoterpene composition of 601 jack pine trees from natural and provenance forest stands representing 63 populations from Alberta to the Atlantic coast. Throughout its range, jack pine exhibited three chemotypes characterized by high proportions of α-pinene, ß-pinene, or limonene. The frequency with which the α-pinene and ß-pinene chemotypes occurred at individual sites was correlated to climatic variables, such as continentality and mean annual precipitation, as were the individual α-pinene and ß-pinene concentrations. However, other monoterpenes were generally not correlated to climatic variables or geographic distribution. Finally, while the enantiomeric ratios of ß-pinene and limonene remained constant across jack pine's distribution, (-):(+)-α-pinene exhibited two separate trends, thereby delineating two α-pinene phenotypes, both of which occurred across jack pine's range. These significant variations in jack pine monoterpene composition may have cascading effects on the continued eastward spread and success of D. ponderosae in the Canadian boreal forest.

Large-scale asymmetric introgression of cytoplasmic DNA reveals Holocene range displacement in a North American boreal pine complex.

Jack pine (Pinus banksiana) and lodgepole pine (Pinus contorta var. latifolia) are two North American boreal hard pines that hybridize in their zone of contact in western Canada. The main objective of this study was to characterize their patterns of introgression resulting from past and recent gene flow, using cytoplasmic markers having maternal or paternal inheritance. Mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA) diversity was assessed in allopatric populations of each species and in stands from the current zone of contact containing morphological hybrids. Cluster analyses were used to identify genetic discontinuities among groups of populations. A canonical analysis was also conducted to detect putative associations among cytoplasmic DNA variation, tree morphology, and site ecological features. MtDNA introgression was extensive and asymmetric: it was detected in P. banksiana populations from the hybrid zone and from allopatric areas, but not in P. contorta populations. Very weak cpDNA introgression was observed, and only in P. banksiana populations. The mtDNA introgression pattern indicated that central Canada was first colonized by migrants from a P. contorta glacial population located west of the Rocky Mountains, before being replaced by P. banksiana migrating westward during the Holocene. In contrast, extensive pollen gene flow would have erased the cpDNA traces of this ancient presence of P. contorta. Additional evidence for this process was provided by the results of canonical analysis, which indicated that the current cpDNA background of trees reflected recent pollen gene flow from the surrounding dominant species rather than historical events that took place during the postglacial colonization.

Phylogeographic structure of jack pine (Pinus banksiana; Pinaceae) supports the existence of a coastal glacial refugium in northeastern North America.

PREMISE OF THE STUDY: The genetic structure of jack pine (Pinus banksiana Lamb.), a North American boreal conifer with large longitudinal distribution, was investigated to test for the possible existence of a genetically distinct lineage in the Maritimes region in northeastern North America, which could be indicative of a mid-latitude coastal refuge during the last glaciation. • METHODS: One maternally inherited mitochondrial DNA (mtDNA) minisatellite marker and four paternally inherited chloroplast DNA (cpDNA) microsatellite markers were used to assess the range-wide geographical structure of jack pine populations with particular focus on northeastern North America. • KEY RESULTS: The populations from the Maritimes region presented a unique mtDNA background characterized by very low diversity and the preponderance of a distinctive mitotype. The distribution of cpDNA diversity was not spatially structured, though three chlorotypes were restricted to the east. • CONCLUSIONS: MtDNA data suggest that populations from the Maritimes region derive from a genetically depauperated north-coastal refugium. Contrastingly, the much higher geographical uniformity observed for cpDNA variation indicates that gene flow by pollen had been much more effective than seed gene flow at homogenizing population structure.

A mitochondrial DNA minisatellite reveals the postglacial history of jack pine (Pinus banksiana), a broad-range North American conifer.

Jack pine (Pinus banksiana Lamb.) is a broadly distributed North American conifer and its current range was covered by the Laurentian ice sheet during the last glacial maximum. To infer about the history and postglacial colonization of this boreal species, range-wide genetic variation was assessed using a new and highly variable minisatellite-like marker of the mitochondrial genome. Among the 543 trees analysed, 14 distinct haplotypes were detected, which corresponded to different repeat numbers of the 32-nucleotide minisatellite-like motif. Several haplotypes were rare with limited distribution, suggesting recent mutation events during the Holocene. At the population level, an average of 2.6 haplotypes and a mean haplotype diversity (H) of 0.328 were estimated. Population subdivision of genetic diversity was quite high with G(ST) and R(ST) values of 0.569 and 0.472, respectively. Spatial analyses identified three relatively homogeneous groups of populations presumably representative of genetically distinct glacial populations, one west and one east of the Appalachian Mountains in the United States and a third one presumably on the unglaciated northeastern coastal area in Canada. These results indicate the significant role of the northern part of the US Appalachian Mountains as a factor of vicariance during the ice age. A fourth distinct group of populations was observed in central Québec where the continental glacier retreated last. It included populations harbouring haplotypes present into the three previous groups, and it had higher level of haplotype diversity per population (H = 0.548) and lower population differentiation (G(ST) = 0.265), which indicates a zone of suture or secondary contact between the migration fronts of the three glacial populations. Introgression from Pinus contorta Dougl. var. latifolia Engelm. was apparent in one western population from Alberta. Altogether, these results indicate that the mitochondrial DNA variation of jack pine is geographically highly structured and it correlates well with large-scale patterns emerging from recent phylogeographical studies of other tree boreal species in North America.