Multiple introductions boosted genetic diversity in the invasive range of black cherry (Prunus serotina; Rosaceae)

Background and Aims Black cherry (Prunus serotina) is a North American tree that is rapidly invading European forests. This species was introduced first as an ornamental plant then it was massively planted by foresters in many countries but its origins and the process of invasion remain poorly documented. Based on a genetic survey of both native and invasive ranges, the invasion history of black cherry was investigated by identifying putative source populations and then assessing the importance of multiple introductions on the maintenance of gene diversity. Methods Genetic variability and structure of 23 populations from the invasive range and 22 populations from the native range were analysed using eight nuclear microsatellite loci and five chloroplast DNA regions. Key Results Chloroplast DNA diversity suggests there were multiple introductions from a single geographic region (the north-eastern United States). A low reduction of genetic diversity was observed in the invasive range for both nuclear and plastid genomes. High propagule pressure including both the size and number of introductions shaped the genetic structure in Europe and boosted genetic diversity. Populations from Denmark, The Netherlands, Belgium and Germany showed high genetic diversity and low differentiation among populations, supporting the hypothesis that numerous introduction events, including multiple individuals and exchanges between sites, have taken place during two centuries of plantation. Conclusions This study postulates that the invasive black cherry has originated from east of the Appalachian Mountains (mainly the Allegheny plateau) and its invasiveness in north-western Europe is mainly due to multiple introductions containing high numbers of individual

Patrimoines de la Seconde Guerre mondiale en Normandie

Ce projet collectif de recherche lancé en 2015 vise à inventorier dans les départements du Calvados, de la Manche et de l’Orne tous les éléments du dernier conflit qui sont conservés, disparus ou enfouis, et à en restituer la cohérence historique. Il vise particulièrement à étudier les différents éléments dans l’histoire du conflit et leur place dans les dispositifs militaires. Il porte donc aussi bien sur les vestiges liés à l’Occupation que sur les vestiges alliés ou les traces et aménageme..

Vestiges de la Seconde Guerre mondiale en Basse-Normandie

Ce programme collectif de recherche vise à inventorier de manière exhaustive les éléments conservés, disparus ou enfouis, formant des ensembles cohérents, sans se limiter aux seules élévations, et à appréhender les différents éléments dans l’histoire du conflit et leur place dans le dispositif défensif. Il s’appuie à la fois sur des études documentaires, des recherches de terrain ainsi que sur une base de données couplée à un SIG. Ce projet répond à un besoin urgent de gestion de ce patrimoin..

Vestiges de la Seconde Guerre mondiale en Basse-Normandie

Pour rappel, ce programme collectif de recherche vise à inventorier de manière exhaustive les éléments conservés, disparus ou enfouis, formant des ensembles cohérents, sans se limiter aux seules élévations, et à appréhender les différents éléments dans l’histoire du conflit et leur place dans le dispositif défensif. Il s’appuie à la fois sur des études documentaires, des recherches de terrain ainsi qu’une base de données couplée à un SIG. Ce projet répond à un besoin urgent de gestion de ce p..

Commitment in newspaper discourse and its evolution : BE X TO structures in contemporary British English

Cette thèse s'intéresse à la prise en charge énonciative jans le discours journalistique à travers l'étude de vingt structures BEX TO de l'anglais britannique contemporain dont BE able to, BE expected to, BE likely to, BE forced to, BE hard to, BE said to). Ce~ structures adjectivales et participiales présentent des affinités avec les domaines connexes de la modalité et de I'évidentialité et jouent ainsi un rôle important dans l'articulation de différents points de vue dans les textes journalistiques. Elles appartiennent cependant à un ensemble mal délimité, infra-catégoriel, et posent en ce sens des problèmes de description qui font qu'elles sont très peu abordées dans la littérature. Pour répondre à ce manque, nous proposons une analyse unifiée des phénomènes syntaxiques, sémantiques et pragmatiques mis en jeu car ces expressions quasi-modales dans le cadre de la ihéorie des Opérations Prédicatives et Énonciatives. lia l'élaboration de formes schématiques s'appuyant sur l'analyse d'un corpus d'énoncés authentiques (The Independent 1992-2009), nous démontrons que BEx TO est la trace d'une double opération d'attribution de propriété et de modalisation qui lui confère des propriétés à la fois factuelles et subjectives. Cette ambivalence des structures apparaît comme un facteur d'explication de leur emploi fréquent dans le discours journalistique, où elles contribuent à la mise en place de différents modes de prise en charge en interaction avec leur co-texte. Afin d'éclairer autrement le fonctionnement de ces marqueurs, nous traitons pour finir de leur évolution récente, que nous mettons en regard avec une étude critique de la théorie de la grammaticalisation.This thesis deals with commitment in newspaper discourse via the case study of twenty BE X TO structures in present-day British English (e.g. BE able to, BE expected to, BE likely to, BE forced to, BE hard to, BE said to). These adjectival and participial constructions are linked to the interrelated domains of modality and evidentiality, and as such they play an important role in the organisation of points of view in news texts. Yet they have been the object of very little research until recently, probably because they belong to an ill-defined grouping of expressions which seem to resist categorisation and pose as a consequence a number of descriptive issues. The goal of the present work is to remedy this void by providing a unified analysis of the syntactic, semantic and pragmatic phenomena involved in the uses of these quasi-modal markers, through the lens of the Theory of Predicative and Enunciative Operations. The schematic forms formulated on the basis of a detailed analysis of the Independent (1992-2009) corpus thus reveal that BE x TO structures are complex operators functioning as markers of property attribution and modalisation at the same time. Because of this double role, they are both factual and subjective, which probably contributes to their high frequency in newspaper discourse. It is also shown that depending on the co-text and the properties of individual structures, they are used by the speaker to express different types of stance or commitment. Finally, the uses of BEx TO structures are put into perspective via a study of their evolution in recent years. The data is considered with respect to grammaticalisation theory in a critical assessmen

Développement d’outils moléculaires pour l’identification et l'étude de la distribution des 3 espèces de lamproies à l'échelle nationale

Ce projet avait pour objectif de développer des marqueurs moléculaires permettant d’identifier les 3 espèces de lamproies présentes en France (Petromyzon marinus, Lampetra fluviatilis et L. planeri) et de détecter leur présence à partir d’ADN environnemental (ADNe). Nous avons testé l’utilisation d’un marqueur mitochondrial qui permet de distinguer P. marinus du genre Lampetra. Nous avons également développé un marqueur de l’ADN nucléaire dénommé diagLpf qui permet de distinguer L. fluviatilis et L. planeri par PCR quantitative. Ce marqueur est particulièrement utile pour identifier les ammocètes aux plus jeunes stades, qu’il est impossible d’identifier par des critères morphologiques. Enfin, avec le marqueur diagLpf, nous ne sommes pas parvenus à détecter la présence de lamproies à partir d’ADNe extrait avec des échantillons d’eau. De futures investigations dans ce domaine seront donc à développer avec les nouvelles techniques disponibles telles que la PCR digitale

A SNP marker to discriminate the european brook lamprey (Lampetra planeri), river lamprey (L. fluviatilis) and their hybrids

Background: The European River lamprey Lampetra fluviatilis and the brook lamprey L. planeri are two closely related species that are also considered as partially reproductively isolated ecotypes. At the larval stage, they cannot be distinguished morphologically or genetically by mitochondrial DNA. We aimed at developing a molecular tool to identify early life stages of L. fluviatilis and L. planeri. Methods and results: We first identified Single Nucleotide Polymorphism (SNP) markers with distinct alleles between L. fluviatilis and L. planeri based on RADseq data from 186 individuals collected in France. Then, we developed a quantitative PCR protocol to genotype a species-specific SNP, which was tested on 270 samples including larvae and adults from both species and 17 sites from Western Europe. Results were consistent with morphological identification in all cases except for samples from the Rhône drainage and the Loch Lomond in Scotland. Conclusions: This marker allows the identification of larval stages of L. fluviatilis, L. planeri as well as hybrids. The two cases where the marker was not diagnostic might be explained by an isolated and distinct L. planeri lineage in the Rhône drainage, and high levels of admixture among L. fluviatilis, L. planeri and the lake-parasitic form in Loch Lomond

Population genetics of Lymnaea stagnalis experimentally exposed to cocktails of pesticides

Freshwater invertebrates may be regularly exposed to pesticides in agricultural landscapes, as water bodies such as ditches and ponds are the final recipient of many chemicals, through various transfer pathways. Local evolutionary impacts may hence be expected on populations, especially for species with a completely aquatic life cycle. We tested the hypothesis that exposure to combinations of pesticides used in crop protection programmes could increase the effect of random genetic drift in a non-target species, via demographic impacts. To do so, experimental populations of the freshwater snail Lymnaea stagnalis were created from a common genetic pool and exposed for three successive generations to treatments corresponding to two different crop protection plans (conventional and low pesticide input). Population genetic parameters were estimated in each generation on the basis of ten polymorphic microsatellite loci. Effects consistent with increased random genetic drift were observed for one sampling campaign performed in the third generation, i.e., decreased genetic variability and increased population differentiation in the group of populations exposed to the treatment programme whose demographic impact was the most effective on L. stagnalis. Otherwise, no clear pattern emerged and even opposed effects could be observed. All populations were found significantly inbred, mostly due to biparental inbreeding. Conversely, selfing was generally not significant, and did not express preferentially under high pesticide pressure. We conclude from this study that population genetics should be used very cautiously in the context of ecological risk assessment, especially when applied to natural populations

Genetic and phenotypic changes in an Atlantic salmon population supplemented with non-local individuals : a longitudinal study over 21 years

While introductions and supplementations using non-native and potentially domesticated individuals may have dramatic evolutionary effects on wild populations, few studies documented the evolution of genetic diversity and life-history traits in supplemented populations. Here, we investigated year-to-year changes from 1989 to 2009 in genetic admixture at 15 microsatellite loci and in phenotypic traits in an Atlantic salmon (Salmo salar) population stocked during the first decade of this period with two genetically and phenotypically distinct source populations. We detected a pattern of temporally increasing introgressive hybridization between the stocked population and both source populations. The proportion of fish returning to the river after a single winter at sea (versus several ones) was higher in fish assigned to the main source population than in local individuals. Moreover, during the first decade of the study, both single-sea-winter and multi-sea-winter (MSW) fish assigned to the main source population were smaller than local fish. During the second decade of the study, MSW fish defined as hybrids were lighter and smaller than fish from parental populations, suggesting outbreeding depression. Overall, this study suggests that supplementation with non-local individuals may alter not only the genetic diversity of wild populations but also life-history traits of adaptive significance.genetic admixture, introgressive hybridization, life-history traits, outbreeding depression, Salmo salar, stockin

Data from: Environmental versus anthropogenic effects on population adaptive divergence in the freshwater snail Lymnaea stagnalis

Repeated pesticide contaminations of lentic freshwater systems located within agricultural landscapes may affect population evolution in non-target organisms, especially in species with a fully aquatic life cycle and low dispersal ability. The issue of evolutionary impact of pollutants is therefore conceptually important for ecotoxicologists. The impact of historical exposure to pesticides on genetic divergence was investigated in the freshwater gastropod Lymnaea stagnalis, using a set of 14 populations from contrasted environments in terms of pesticide and other anthropogenic pressures. The hypothesis of population adaptive divergence was tested on 11 life-history traits, using QST -FST comparisons. Despite strong neutral differentiation (mean FST = 0.291), five adult traits or parameters were found to be under divergent selection. Conversely, two early expressed traits showed a pattern consistent with uniform selection or trait canalization, and four adult traits appeared to evolve neutrally. Divergent selection patterns were mostly consistent with a habitat effect, opposing pond to ditch and channel populations. Comparatively, pesticide and other human pressures had little correspondence with evolutionary patterns, despite hatching rate impairment associated with global anthropogenic pressure. Globally, analyses revealed high genetic variation both at neutral markers and fitness-related traits in a species used as model in ecotoxicology, providing empirical support for the need to account for genetic and evolutionary components of population response in ecological risk assessment