Drought-Adaptation Potential in Fagus sylvatica: Linking Moisture Availability with Genetic Diversity and Dendrochronology

<div><h3>Background</h3><p>Microevolution is essential for species persistence especially under anticipated climate change scenarios. Species distribution projection models suggested that the dominant tree species of lowland forests in Switzerland, European beech (<em>Fagus sylvatica</em> L.), might disappear from most areas due to expected longer dry periods. However, if genotypes at the moisture boundary of the species climatic envelope are adapted to lower moisture availability, they can serve as seed source for the continuation of beech forests under changing climates.</p> <h3>Methodology/Principal Findings</h3><p>With an AFLP genome scan approach, we studied neutral and potentially adaptive genetic variation in <em>Fagus sylvatica</em> in three regions containing a dry and a mesic site each (<em>n</em>_ind. = 241, <em>n</em>_markers = 517). We linked this dataset with dendrochronological growth measures and local moisture availabilities based on precipitation and soil characteristics. Genetic diversity decreased slightly at dry sites. Overall genetic differentiation was low (<em>F</em>_st = 0.028) and Bayesian cluster analysis grouped all populations together suggesting high (historical) gene flow. The Bayesian outlier analyses indicated 13 markers with three markers differing between all dry and mesic sites and the others between the contrasting sites within individual regions. A total of 41 markers, including seven outlier loci, changed their frequency with local moisture availability. Tree height and median basal growth increments were reduced at dry sites, but marker presence/absence was not related to dendrochronological characteristics.</p> <h3>Conclusion and Their Significance</h3><p>The outlier alleles and the makers with changing frequencies in relation to moisture availability indicate microevolutionary processes occurring within short geographic distances. The general genetic similarity among sites suggests that ‘preadaptive’ genes can easily spread across the landscape. Yet, due to the long live span of trees, fostering saplings originating from dry sites and grown within mesic sites might increase resistance of beech forests during the anticipated longer dry periods.</p> </div

Estimation of Fagus sylvatica L mating system parameters in natural populations

The mating system of beech (Fagus sylvatica L) was investigated using polymorphism at 4 allozyme loci and the multilocus model of Ritland and Jain (1981). Beech appears to be a highly outcrossing species: the outcrossing rate ranges from 0.94 to 1. No significant differences were found in outcrossing rates according to environmental factors or among or within trees. Comparison of single-locus and multilocus estimates indicated that little or no inbreeding occurred. Outcross pollen pool was not homogeneous and heterogeneity in pollen allelic frequencies was observed even among nearby trees. A possible explanation may be the temporal variability of the pollen pool due to variation in flowering time and to matings between phenologically synchronous trees.Estimation des paramètres du mode de reproduction de Fagus sylvatica L. Le mode de reproduction du hêtre (Fagus sylvatica) a été étudié à l'aide de 4 marqueurs alloenzymatiques (GOT1, MDH1, SOD1 et IDH1) et du modèle multilocus de Ritland etJain (1981) dans 4 populations françaises : l'une en forêt d'Issaux dans les Pyrénées-Atlantiques, les trois autres dans le massif de l'Aigoual (La Serreyrèdes, Plo du Four et Sommet) (tableau I). Dans la forêt d'Issaux, 3 parcelles présentant des physionomies différentes ont été étudiées : une parcelle à forte densité (forêt), une autre située en lisière de forêt et la troisième formée d'arbres isolés. Les questions abordées dans cette étude sont les suivantes : i) quel est le taux d'autofécondation du hêtre en conditions naturelles ? ii) existe-t-il des variations de ce taux dans l'espace et dans le temps ? iii) existe-t-il une hétérogénéité du pollen à l'intérieur des populations ? Le hêtre est une espèce hautement allogame : le taux d'allofécondation est compris entre 0,94 (Aigoual) et 1 (Issaux) (tableau II). Ces estimations correspondent à des taux d'autofécondation inférieurs à la valeur moyenne (13%) calculée à partir des observations de Nielsen et Schaffalitzky-de-Muckadell (1954). Aucune différence significative n'a été mise en évidence selon les variations des facteurs de l'environnement entre les taux d'allofécondation observés. Ce taux ne varie pas non plus significativement d'un arbre à l'autre ou entre les secteurs d'un même arbre. Les taux très élevés d'allofécondation chez cette espèce autocompatible pourraient s'expliquer par certaines caractéristiques de sa biologie florale. La comparaison des estimations uni- et multilocus du taux d'allofécondation montre un niveau nul ou très faible de consanguinité. Une analyse de variance à 2 facteurs montre qu'il n'y a pas de variation de fréquence allopollinique d'un secteur à l'autre de la couronne d'un arbre : les secteurs d'un même arbre ont donc pu être considérés comme des répétitions aléatoires. En revanche, le nuage allopollinique est hétérogène : i) d'un arbre à l'autre et les fréquences alléliques du pollen peuvent être différentes même entre individus voisins (IDH1, tableau III), ii) entre les peuplements (GOT1 et MDH1). Dans la forêt d'Issaux cette hétérogénéité est maximale pour les arbres isolés (tableau V). À l'Aigoual, il n'y a pas d'hétérogénéité interpeuplements mais une forte hétérogénéité à l'intérieur de 2 des peuplements (tableau VI). Ces phénomènes peuvent s'expliquer par la variabilité du nuage pollinique dans le temps en raison de décalages à déterminisme génétique de la période de floraison (jusqu'à 20 j) et de la reproduction entre arbres synchrones d'un point de vue phénologique. Ce modèle pourrait expliquer, en particulier, l'hétérogénéité de l'allopollen entre arbres voisins non synchrones. Cependant, il devrait conduire, au cours du temps, à une structuration des populations en groupes d'arbres précoces et d'arbres tardifs, ce qui n'a pas été observé. En fait, il existe entre les individus les plus précoces et les plus tardifs toutes les classes intermédiaires : la distribution des arbres en fonction de leur période de floraison est à peu près normale, ce qui induit des classes chevauchantes d'individus

Genetic structure of natural stands of Fagus sylvatica L. (beech)

International audienceThe spatial genetic structures of three French natural beech stands were analysed using poly-morphic enzyme loci. Two methods were used: F-statistics and spatial autocorrelation statistics. Within these stands where self-fertilization rate is 0, a low heterozygote deficit was observed which may be due to a moderate level of mating between relatives. However, no increase of this deficit was observed from one generation to the next. The spatial genetic structuring was low. Within one open stand composed of several patches, founder events are invoked to explain a significant autocorrela-tion. Within the two other stands, both dense, results are similar to those produced by simulations of an isolation by distance model. The genetic structure seems not to be stable in space and time which may be due to (i) a limited number of generations; (ii) an effective gene flow less limited than hypothesized; and (iii) fertility differences or phenological incompatibilities between individuals

Fixation nette de carbone dans la biomasse d'un peuplement de Pin maritime, dans les Landes de Gascogne

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Fixation nette de carbone dans la biomasse d'un peuplement de Pin maritime, dans les Landes de Gascogne

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When capacitive transduction meets the thermomechanical limit: Towards femto-newton force sensors at very high frequency

International audienceWe show that the capacitive transduction of a MEMS device using a setup based on a microwave detection scheme achieves the measurement of the thermomechanical noise spectrum of a high-frequency (>10 MHz) high-stiffness (>10 5 N/m) resonator, reaching the outstanding displacement resolution of 1 fm/√Hz. This result paves the way for vibrating sensors with exquisite force resolution in the fN/vHz range, enabling large-bandwidth measurements of mechanical interactions at small scale and rheology of fluids at very high frequency. An example of application is given and concerns atomic force microscopy images of biomolecular assemblies

Endovascular management of ureteroarterial fistula. Single institution experience and systematic literature review

Background: Ureteroarterial fistula (UAF) represents an uncommon complication after urological surgery; however, this is a well-documented condition in patients with predisposing risk factors. The aim of the present study is to report and analyze the endovascular management of a series of patients with UAF, treated in authors’ hospital, and to report and analyze the same data concerning patients retrieved from a systematic literature review. Methods: Authors conducted a retrospective analysis of prospectively collected data and a systematic literature review. The research was carried out through PubMed database searching the following keywords: “uretero arterial fistula” and “uretero iliac fistula.” It includes only articles reporting the endovascular management. Results: Forty-six articles were included in the present study for a total of 94 patients. Risk factors were as follows: chronic indwelling ureteral stents, pelvic surgery, radiotherapy, iliac artery pseudo-aneurysm, and chemotherapy. All patients had gross hematuria at presentation. Stent graft placement was performed in 89 patients, embolization in 5 patients, and iliac internal artery embolization combined with stent graft placement was performed in 24 patients. Four postprocedural complications were observed (4.2%). During a median follow-up of 8 months, 10 complications related to UAF were observed (10.6%): rebleeding (7 cases) and stent thrombosis (3 cases). Two patients died for causes related to UAF (2.1%): rebleeding (1) and retroperitoneal abscess (1). Conclusion: Based on the present data, endovascular treatment is feasible and safe with low postprocedural complications and mortality rate. Considering the increase in surgery and radiotherapy performed, UAF should be always debated in patients with massive hematuria

Range wide versus local patterns of genetic diversity in hornbeam (Carpinus betulus L.)

A study based on AFLP markers was conducted to characterise the present population genetic structure of Carpinus betulus in Europe and to formulate guidelines for the use of this species in plantations on a local scale in Flanders. High within-population diversity and little (but significant) genetic differentiation were detected at both Flemish and European scales. However, there was a pattern of isolation by distance only at the European scale. Within-population gene diversity, a new rarefaction-based measure of number of genotypes (lsquoband richnessrsquo) and percentage of polymorphic loci are lower north of major mountain chains, suggesting that the mountain ranges formed a second bottleneck for the hornbeam during postglacial recolonisation. In Flanders, despite lower gene diversity, there were more polymorphic loci than in other European populations, a pattern that might have been caused by the mixing of material through planting, e.g. in hedges. In view of these findings, it is advised to create a single Flemish seed zone and to use preferentially reproductive material from this seed zone for new plantations in Flander