Synoptic-Scale Atmospheric Circulation and Boreal Canada Summer Drought Variability of the Past Three Centuries

Five independent multicentury reconstructions of the July Canadian Drought Code and one reconstruction of the mean July-August temperature were developed using a network of 120 well-replicated tree-ring chronologies covering the area of the eastern Boreal Plains to the eastern Boreal Shield of Canada. The reconstructions were performed using 54 time-varying reconstruction submodels that explained up to 50% of the regional drought variance during the period of 1919-84. Spatial correlation fields on the six reconstructions revealed that the meridional component of the climate system from central to eastern Canada increased since the mid-nineteenth century. The most obvious change was observed in the decadal scale of variability. Using 500-hPa geopotential height and wind composites, this zonal to meridional transition was interpreted as a response to an amplification of long waves flowing over the eastern North Pacific into boreal Canada, from approximately 1851 to 1940. Composites with NOAA Extended Reconstructed SSTs indicated a coupling between the meridional component and tropical and North Pacific SST for a period covering at least the past 150 yr, supporting previous findings of a summertime global ocean-atmospherel-and surface coupling. This change in the global atmospheric circulation could be a key element toward understanding the observed temporal changes in the Canadian boreal forest fire regimes over the past 150 yr

Presence of Palaemon macrodactylus in a Europe estuary: evidence for a successful invasion of the Gironde (SW France)

Palaemon macrodactylus, an exotic shrimp native to the northwest Pacific Ocean, has been recorded in many estuaries along the Atlantic coast of Europe since the late 1990’s. In this study, a regular monthly survey, held since 1992 of the middle section of the Gironde estuary, revealed this species’ rapid and full colonization of the system since its appearance in samples during summer 1998. In the Gironde, the population of P. macrodactylus is self-sustaining and the species is now established there. Our study highlights two important elements that might explain its successful colonization: its ability to quickly invade a niche under-exploited by the similar native species and its greater reproductive output. The species’spatio-temporal distribution in relation to environmental variables was studied and compared with that of the native species P. longirostris. The exotic species was shown to mainly inhabit the polyhaline and mesohaline section of the estuary, which are sections generally under-exploited by females of the native species. Furthermore, fecundity analysis and larval abundance survey results revealed a higher potential fecundity and a greater proportion of larvae and juvenile stages for P. macrodactylus in the natural environment

IN SITU COMPARISON OF TREE-RING RESPONSES TO CLIMATE AND POPULATION GENETICS: THE NEED TO CONTROL FOR LOCAL CLIMATE AND SITE VARIABLES

Tree species responses to climate change will be greatly influenced by their evolutionary potential and their phenotypic plasticity. Investigating tree-rings responses to climate and population genetics at the regional scale is therefore crucial in assessing the tree behaviour to climate change. This study combined in situ dendroclimatology and population genetics over a latitudinal gradient and compared the variations between the two at the intra- and inter-population levels. This approach was applied on the northern marginal populations of Thuja occidentalis (eastern white-cedar) in the Canadian boreal forest. We aimed first to assess the radial growth variability (response functional trait) within populations across the gradient and to compare it with the genetic diversity (microsatellites). Second, we investigated the variability in the growth response to climate at the regional scale through the radial growth-climate relationships, and tested its correlation with environmental variables and population genetic structure. Model selection based on the Akaike Information Criteria revealed that the growth synchronicity between pairs of trees of a population covariates with both the genetic diversity of this population and the amount of precipitation (inverse correlation), although these variables only explained a small fraction of the observed variance. At the regional scale, variance partitioning and partial redundancy analysis indicate that the growth response to climate was greatly modulated by stand environmental variables, suggesting predominant plastic variations in growth-response to climate. Combining in situ dendroclimatology and population genetics is a promising way to investigate species’ response capacity to climate change in natural stands. We stress the need to control for local climate and site conditions effects on dendroclimatic response to climate to avoid misleading conclusions regarding the associations with genetic variables

L'introduction de la crevette exotique Palaemon macrodactylus dans l'estuaire de la Gironde risque-t-elle d'impacter la population de crevettes blanches natives P. longirostris ? : Quelques éléments de réponse

National audience5 espèces de crevettes sont recensées dans l'estuaire de la Gironde. En été 2006 on identifie la crevette exotique Palaemon macrodactylus. Etude de cette nouvelle espèce et comparaison avec la crevette blanche

Invasion récente de la crevette asiatique Palaemon macrodactylus : cas de la Gironde (France)

International audienceThe shrimp Palaemon macrodactylus Rathbun, 1902 is a native species of Asian waters. It was introduced into California (USA) in the 1950s and it had recently been recorded in Mar del Plata Harbor (Argentina) and in several European estuaries, such as the Guadalquivir (Spain), the Orwell (England) and the Gironde (France). In Europe, Palaemon macrodactylus was recorded belatedly after its introduction and hence very few data about its ecology and possible interactions with local shrimps are available. Since 1979, a large part of the Gironde estuary had been monthly sampled for fauna survey (mainly fish). The date of the first apparition of the oriental shrimp Palaemon macrodactylus and its expansion were inferred from the examination of the preserved samples from 1992 to 2006. The distribution of the invasive species indicated a spatial overlap with the distribution of the native species Palaemon longirostris Milne Edwards, 1837 and Crangon crangon Linnaeus, 1758, according to the seasons. We particularly focused on the possible interactions with Palaemon longirostris which supports an important traditional fisheries in the Gironde estuary (73 tonnes in the 2005). The first ecological data about P. macrodacylus in this area are presented, particularly its spatial distribution and its reproductive characters. These results revealed that the exotic species had an ecological advantage compared to the native one. P. macrodactylus is becoming an abundant element of the Palaemonid community of Gironde. The strength of the exotic population may be responsible for the decrease in abundance of the native shrimp populations

Faire l’histoire culturelle de la mondialisation

Depuis presque 200 ans, la mondialisation, cette phase d’accélération sans précédent des relations sociales et des contacts interculturels, caractérise aussi bien notre univers mental qu’elle définit l’horizon de nos pratiques quotidiennes. Ce livre s’attache à en saisir toute la complexité. Il entend à la fois saisir des représentations du mondial, se pencher sur les ambassadeurs de la mondialité aux XIXe et XXe siècles, réfléchir à l’articulation du global et du local, et analyser la configuration politique globale avec les nouvelles formes de gouvernance. À l’issue de ces études, il ressort que si le monde est dorénavant unique, il est loin d’être uniforme. Selon les termes du philosophe canadien Charles Taylor, « une profonde diversité » semble même dominer par-delà les fausses impressions d’uniformité. L’ensemble de ces contributions dessine un monde global dans lequel les individus échappent à la généralisation et à l’essentialisation mais relève d’un « tiers-espace », selon Homi Bhabba, où les identités se négocient en permanence au fil des circonstances offertes par un monde à la fois homogénéisé et fragmenté. Finalement, selon les mots du poète Pablo Neruda, les êtres mondialisés s’apparentent un peu à des « arbres ailés » quand les racines du local montent au ciel du global

Murine Nod1 but not its human orthologue mediates innate immune detection of tracheal cytotoxin

Tracheal cytotoxin (TCT) was originally described as the minimal effector that was able to reproduce the cytotoxic response of Bordetella pertussis on ciliated epithelial cells. This molecule triggers pleiotropic effects such as immune stimulation or slow-wave sleep modulation. Further characterization identified TCT as a specific diaminopimelic acid (DAP)-containing muropeptide, GlcNAc-(anhydro)MurNAc-L-Ala-D-Glu-mesoDAP-D-Ala. Here, we show that the biological activity of TCT depends on Nod1, an intracellular sensor of bacterial peptidoglycan. However, Nod1-dependent detection of TCT was found to be host specific, as human Nod1 (hNod1) poorly detected TCT, whereas mouse Nod1 (mNod1) did so efficiently. More generally, hNod1 required a tripeptide (L-Ala-D-Glu-mesoDAP) for efficient sensing of peptidoglycan, whereas mNod1 detected a tetrapeptide structure (L-Ala-D-Glu-mesoDAP-D-Ala). In murine macrophages, TCT stimulated cytokine secretion and NO production through Nod1. Finally, in vivo, injection of the tetrapeptide structure in mice triggered a transient yet strong release of cytokines into the bloodstream and the maturation of macrophages, in a Nod1-dependent manner. This study thereby identifies Nod1 as the long sought after sensor of TCT in mammals