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

β1A Integrin Is a Master Regulator of Invadosome Organization and Function

Use of patterned surfaces, reverse genetics, and time-controlled photoinactivation showed that β1 but not β3 integrins are required for invadosome formation, self-assembly, and stabilization into a ring structure. The activation state of β1 as well as its phosphorylation by protein kinase C on Ser785 control these process and link to the degradative function

Paternity analysis of pollen-mediated gene flow for Fraxinus excelsior L. in a chronically fragmented landscape

Paternity analysis based on microsatellite marker genotyping was used to infer contemporary genetic connectivity by pollen of three population remnants of the wind-pollinated, wind-dispersed tree Fraxinus excelsior, in a deforested Scottish landscape. By deterministically accounting for genotyping error and comparing a range of assignment methods, individual-based paternity assignments were used to derive population-level estimates of gene flow. Pollen immigration into a 300ha landscape represents between 43% and 68% of effective pollination, mostly depending on assignment method. Individual male reproductive success is unequal, with 31 of 48 trees fertilising one seed or more, but only three trees fertilising more than ten seeds. Spatial analysis suggests a fat-tailed pollen dispersal curve with 85% of detected pollination occurring within 100m, and 15% spreading between 300m and 1900m from the source. Identification of immigrating pollen sourced from two neighbouring remnants indicates further effective dispersal at 2900m. Pollen exchange among remnants is driven by population size rather than geographic distance, with larger remnants acting predominantly as pollen donors, and smaller remnants as pollen recipients. Enhanced wind dispersal of pollen in a barren landscape ensures that the seed produced within the catchment includes genetic material from a wide geographic area. However, gene flow estimates based on analysis of non-dispersed seeds were shown to underestimate realised gene immigration into the remnants by a factor of two suggesting that predictive landscape conservation requires integrated estimates of post-recruitment gene flow occurring via both pollen and seed

Anisotropic diffusion of water molecules in hydroxyapatite nanopores

Funded by EPSRC Grant EP/K000128/1

High amplitude wave propagation in collapsible tube. I. — Relation between rheological properties and wave propagation

The mechanical behaviour of collapsible tubes is theoretically and experimentally studied when the viscoelastic wall is longitudinally stretched. The dynamic rheological law is deduced from the static law by introducing the dynamic Young's modulus as experimentally obtained. It is then shown that the speed of small amplitude pressure waves is well predicted using this dynamic rheological law.La mécanique des tuyaux collabables à parois viscoélastiques prétendues longitudinalement est étudiée à la fois théoriquement et expérimentalement. Le comportement statique du tube est caractérisé par une loi reliant la pression transmurale et l'aire d'une section droite du tube. Cette loi, vérifiée expérimentalement grâce à des mesures effectuées sur un banc hydrodynamique de simulation, est généralisée au cas de phénomènes instationnaires en introduisant le module dynamique mesuré directement sur des échantillons de matériau pariétal. On montre alors que l'on peut déduire de cette loi de comportement dynamique, la vitesse des ondes de pression de petite amplitude. Ces résultats sont alors confrontés aux mesures directes de vitesse de propagation des ondelettes de pressions, en imposant différentes valeurs de la pression moyenne, que le tube soit alors gonflé ou partiellement collabé

High amplitude wave propagation in collapsible tubes. II. Forerunners and high amplitude waves

It is shown that, under certain circumstances, a pressure wave of large amplitude which propagates in a fluid, inside a deformable viscoelastic tube initially inflated or collapsed, can present the behaviour of a shock wave. The characteristic time and length of formation for such a shock like wave can be computed from the method of characteristics if the dynamic rheological law of the tube is known. The principal feature of such a shock wave propagation inside an initially collapsed tube is the presence of wavelets on the wave front. The dispersion relation of such wavelets, experimentally obtained from the wall displacements measurements, has been theoretically interpreted on the basis of dynamical effects dominated by the longitudinal tension of the tube.Il a été montré qu'une onde de pression de grande amplitude qui se propage dans un fluide contenu dans un tube initialement partiellement collabé ou dilaté, à parois viscoélastiques, peut, dans certaines conditions, présenter des caractéristiques d'une onde de choc. Le temps et la distance de formation de cette onde de surpression peuvent être calculés à partir de la méthode des caractéristiques lorsque la loi de comportement dynamique du tube est connue. Il est d'autre part montré que la caractéristique essentielle du front d'onde de surpression, dans le cas d'un tuyau initialement partiellement collabé, est la présence d'ondelettes se propageant en précurseur du front d'onde principal, et dont la dynamique est dominée par les effets de tension longitudinale du tube. La propagation de ces ondes, déduites des mesures de déplacement des parois peut être caractérisée par une équation de dispersion dont on donne une interprétation théorique

Theoretical models in mechanics of the left ventricle.

International audienceDifferent rheological concepts and theoretical studies have been recently presented using models of myocardial mechanics. Complex analysis of the mechanical behavior of the left ventricular wall have been developed in order to estimate the local stresses and deformations that occur during the heart cycle as well as the ventricular stroke volume and pressure. Theoretical models have taken into account non-linear and viscoelastic passive properties of the myocardium tissue, when subjected to large deformations, through given strain energy functions or stress-strain relations. Different prolate spheroid geometries have been considered for such thick shell cardiac structure. During the active state of the contraction, the rheological behavior of the fibers has been described using different muscle models and relationships between fiber tension and strain, and activation degree. A forthcoming approach for bridging the gap between the knowledge of the muscle fiber microrheological properties and the study of the mechanical behavior of the entire ventricle, consists in including anisotropic and inhomogeneous effects through fiber direction field