Spatial and temporal biodiversity variations in a high mountain environment: the case of the proglacial margin of the Evettes, Natura 2000 area (Savoie, French Alps)

International audienceThe aim of this paper is to contribute to the understanding of the changes in plant cover after the recent glacier retreat, in an alpine environment. The selected study site in Savoie in the French Alps (2502-2509m asl), belonging to the European network Natura 2000, provides favourable conditions for the study due to the flat glacier foreland, where the glacier did not advance since the Little Ice Age. Data collected from 110 botanical plots were correlated with dated glacial and proglacial landforms. Species diversity has been analysed using the Shannon-Weaver index, the Grime classification, and the uncommon species described in the European list of Natura 2000 European Network. Classical and multivariate analyses have been made to determine the impact of the glacial retreat on the biodiversity variation. We show that the changes in species richness and vegetation cover were related to the distance from the glacier front. The biodiversity index was less than 2.5 near the glacier but above 4 at the furthest point. The highest plant diversity, however, was observed at an intermediate position, where competitive and pioneer plants were equally represented in the field. This location, concurrently, showed the highest heterogeneity in the activity of periglacial processes. It seems that the most heterogeneous and disturbed soils, due to inherited deposits and currently active periglacial processes, are responsible for an increase in biodiversity.L'objectif de cet article est de contribuer à la compréhension des changements en cours dans un environnement alpin, au front d'une marge proglaciaire, en relation avec un retrait glaciaire. Le secteur étudié correspond à la plaine proglaciaire du glacier des Evettes, situé en Savoie dans les Alpes françaises, vers 2500m d'altitude. Ce site appartient au réseau Natura 2000. Les conditions écologiques locales ont permis l'élaboration d'une vaste plaine proglaciaire en raison du retrait du glacier depuis la fin du Petit Âge Glaciaire (stades de retrait jalonnés depuis 1860). Les données collectées reposent sur l'échantillonnage floristique sur 110 placettes dont les résultats ont été analysés statistiquement avec plusieurs paramètres : la distance par rapport au front glaciaire actuel (et donc l'âge depuis la déglaciation), le contexte morphopédologique, la diversité spécifique déterminée à partir de l'indice Shannon-Weaver, la classification du type de stratégie dite de Grime et la valeur de la rareté de l'espèce lorsque celle-ci est signalée dans les listes du réseau européen de Natura 2000. Des analyses univariées et multivariées ont été appliquées afin de déterminer l'impact du retrait glaciaire sur la variation de la biodiversité. Si l'on aboutit très classiquement à la démonstration qu'il y a augmentation globale de la biodiversité en allant du front glaciaire actuel vers la marge la plus externe, notre étude prouve que la biodiversité la plus élevée concerne un point intermédiaire. Cette position correspond en réalité au secteur où les conditions locales périglaciaires permettent la cohabitation de plantes à la fois pionnières, rudérales et compétitrices. A terme, cette activité périglaciaire, ici responsable de l'augmentation de la biodiversité, est pourtant en régression sous l'impact du réchauffement

Identification of genetic variants associated with Huntington's disease progression: a genome-wide association study

Background Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, HTT. Age at onset has been used as a quantitative phenotype in genetic analysis looking for Huntington's disease modifiers, but is hard to define and not always available. Therefore, we aimed to generate a novel measure of disease progression and to identify genetic markers associated with this progression measure. Methods We generated a progression score on the basis of principal component analysis of prospectively acquired longitudinal changes in motor, cognitive, and imaging measures in the 218 indivduals in the TRACK-HD cohort of Huntington's disease gene mutation carriers (data collected 2008–11). We generated a parallel progression score using data from 1773 previously genotyped participants from the European Huntington's Disease Network REGISTRY study of Huntington's disease mutation carriers (data collected 2003–13). We did a genome-wide association analyses in terms of progression for 216 TRACK-HD participants and 1773 REGISTRY participants, then a meta-analysis of these results was undertaken. Findings Longitudinal motor, cognitive, and imaging scores were correlated with each other in TRACK-HD participants, justifying use of a single, cross-domain measure of disease progression in both studies. The TRACK-HD and REGISTRY progression measures were correlated with each other (r=0·674), and with age at onset (TRACK-HD, r=0·315; REGISTRY, r=0·234). The meta-analysis of progression in TRACK-HD and REGISTRY gave a genome-wide significant signal (p=1·12 × 10−10) on chromosome 5 spanning three genes: MSH3, DHFR, and MTRNR2L2. The genes in this locus were associated with progression in TRACK-HD (MSH3 p=2·94 × 10−8 DHFR p=8·37 × 10−7 MTRNR2L2 p=2·15 × 10−9) and to a lesser extent in REGISTRY (MSH3 p=9·36 × 10−4 DHFR p=8·45 × 10−4 MTRNR2L2 p=1·20 × 10−3). The lead single nucleotide polymorphism (SNP) in TRACK-HD (rs557874766) was genome-wide significant in the meta-analysis (p=1·58 × 10−8), and encodes an aminoacid change (Pro67Ala) in MSH3. In TRACK-HD, each copy of the minor allele at this SNP was associated with a 0·4 units per year (95% CI 0·16–0·66) reduction in the rate of change of the Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, and a reduction of 0·12 units per year (95% CI 0·06–0·18) in the rate of change of UHDRS Total Functional Capacity score. These associations remained significant after adjusting for age of onset. Interpretation The multidomain progression measure in TRACK-HD was associated with a functional variant that was genome-wide significant in our meta-analysis. The association in only 216 participants implies that the progression measure is a sensitive reflection of disease burden, that the effect size at this locus is large, or both. Knockout of Msh3 reduces somatic expansion in Huntington's disease mouse models, suggesting this mechanism as an area for future therapeutic investigation

Géodynamique, colonisation végétale et phytodiversité des talus d'éboulis dans le massif de la Grande Chartreuse (Préalpes françaises du Nord). Caractéristiques géo-écologiques et sensibilité aux changements environnementaux.

Due to their rich ecosystems and great plant diversity, the talus slopes of the Grande Chartreuse massif have been designated by the European Directive on Habitats, Fauna and Flora, as sites of community interest. The plant diversity on these talus slopes seems to be a function of the mosaic landscape structure, whose complex dynamics are determined by the interaction of topo-climatic, edaphic, geomorphologic, geodynamic and biological factors, that act at several spatio-temporal scales. The plants colonization noted on some talus slopes may be at the origin of a change in the phytodiversity. On talus slopes exposed in the past to only limited anthropic pressure, this phenomenon may be interpreted as a consequence of frequency and intensity deceleration of niveo-periglacial processes due to climatic change. This study is based on a geo-ecological approach of talus slopes mosaics. The methodology used enabled us to characterize the structure and the functionning of talus slopes mosaics but also define their evolution over the last century. Furthermore, this study underscores the richness of these habitats, wich could become observatories of choice for monitoring phytodiversity evolution under the effects of current environmental changes.Les talus d'éboulis du massif de la Grande Chartreuse retenus par la Directive « Habitats, faune et flore » comme des sites d'intérêt communautaire, abritent de nombreuses espèces rupicoles considérées comme prioritaires. La diversité spécifique de ces talus d'éboulis semble inféodée à leur structure paysagère en mosaïque, dont la dynamique est régie par l'interaction de facteurs topo-climatiques, édaphiques, géomorphologiques, géodynamiques et biologiques, agissant à plusieurs échelles spatio-temporelles. La colonisation végétale constatée, sur certains talus d'éboulis au cours des trente dernières années, pourrait être à l'origine d'une modification de la phytodiversité. Sur des talus d'éboulis sujets dans le passé, à une pression anthropique réduite, ce phénomène semble être une conséquence du ralentissement de la fréquence et de l'intensité des processus nivéo-périglaciaires, lié au réchauffement climatique. Cette étude repose sur une approche géo-écologique des talus d'éboulis. La méthodologie mise en œuvre permet de caractériser la structure et le fonctionnement des mosaïques mais aussi de cerner leur évolution depuis le début du siècle dernier. De plus, elle révèle la richesse de ces habitats qui pourraient constituer des observatoires privilégiés, pour le suivi à long terme de la phytodiversité sous l'effet des changements environnementaux en cours

Articulation entre protection stricte et approche contractuelle pour la conservation des roselières du Grand Delta du Rône. Activités humaines et dynamique de la biodiversité en région méditerranéenne. Problématique scientifique, enjeux de conservation

National audienc

Clinical and genetic characteristics of late-onset Huntington's disease

Background: The frequency of late-onset Huntington's disease (>59 years) is assumed to be low and the clinical course milder. However, previous literature on late-onset disease is scarce and inconclusive. Objective: Our aim is to study clinical characteristics of late-onset compared to common-onset HD patients in a large cohort of HD patients from the Registry database. Methods: Participants with late- and common-onset (30–50 years)were compared for first clinical symptoms, disease progression, CAG repeat size and family history. Participants with a missing CAG repeat size, a repeat size of ≤35 or a UHDRS motor score of ≤5 were excluded. Results: Of 6007 eligible participants, 687 had late-onset (11.4%) and 3216 (53.5%) common-onset HD. Late-onset (n = 577) had significantly more gait and balance problems as first symptom compared to common-onset (n = 2408) (P <.001). Overall motor and cognitive performance (P <.001) were worse, however only disease motor progression was slower (coefficient, −0.58; SE 0.16; P <.001) compared to the common-onset group. Repeat size was significantly lower in the late-onset (n = 40.8; SD 1.6) compared to common-onset (n = 44.4; SD 2.8) (P <.001). Fewer late-onset patients (n = 451) had a positive family history compared to common-onset (n = 2940) (P <.001). Conclusions: Late-onset patients present more frequently with gait and balance problems as first symptom, and disease progression is not milder compared to common-onset HD patients apart from motor progression. The family history is likely to be negative, which might make diagnosing HD more difficult in this population. However, the balance and gait problems might be helpful in diagnosing HD in elderly patients

Optimization of adsorptive removal of α-toluic acid by CaO2 nanoparticles using response surface methodology

The present work addresses the optimization of process parameters for adsorptive removal of α-toluic acid by calcium peroxide (CaO2) nanoparticles using response surface methodology (RSM). CaO2 nanoparticles were synthesized by chemical precipitation method and confirmed by Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) analysis which shows the CaO2 nanoparticles size range of 5–15 nm. A series of batch adsorption experiments were performed using CaO2 nanoparticles to remove α-toluic acid from the aqueous solution. Further, an experimental based central composite design (CCD) was developed to study the interactive effect of CaO2 adsorbent dosage, initial concentration of α-toluic acid, and contact time on α-toluic acid removal efficiency (response) and optimization of the process. Analysis of variance (ANOVA) was performed to determine the significance of the individual and the interactive effects of variables on the response. The model predicted response showed a good agreement with the experimental response, and the coefficient of determination, (R2) was 0.92. Among the variables, the interactive effect of adsorbent dosage and the initial α-toluic acid concentration was found to have more influence on the response than the contact time. Numerical optimization of process by RSM showed the optimal adsorbent dosage, initial concentration of α-toluic acid, and contact time as 0.03 g, 7.06 g/L, and 34 min respectively. The predicted removal efficiency was 99.50%. The experiments performed under these conditions showed α-toluic acid removal efficiency up to 98.05%, which confirmed the adequacy of the model prediction

Reduced Cancer Incidence in Huntington's Disease: Analysis in the Registry Study

Background: People with Huntington's disease (HD) have been observed to have lower rates of cancers. Objective: To investigate the relationship between age of onset of HD, CAG repeat length, and cancer diagnosis. Methods: Data were obtained from the European Huntington's disease network REGISTRY study for 6540 subjects. Population cancer incidence was ascertained from the GLOBOCAN database to obtain standardised incidence ratios of cancers in the REGISTRY subjects. Results: 173/6528 HD REGISTRY subjects had had a cancer diagnosis. The age-standardised incidence rate of all cancers in the REGISTRY HD population was 0.26 (CI 0.22-0.30). Individual cancers showed a lower age-standardised incidence rate compared with the control population with prostate and colorectal cancers showing the lowest rates. There was no effect of CAG length on the likelihood of cancer, but a cancer diagnosis within the last year was associated with a greatly increased rate of HD onset (Hazard Ratio 18.94, p < 0.001). Conclusions: Cancer is less common than expected in the HD population, confirming previous reports. However, this does not appear to be related to CAG length in HTT. A recent diagnosis of cancer increases the risk of HD onset at any age, likely due to increased investigation following a cancer diagnosis