Earth Sciences

Metabolic and proteomic profiling of diapause in the aphid parasitoid praon volucre

D.Renault , E.Com , H.Colinet , B.Charoy-Guevel


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Background: Diapause, a condition of developmental arrest and metabolic depression exhibited by a wide range of animals is accompanied by complex physiological and biochemical changes that generally enhance environmental stress tolerance and synchronize reproduction. Even though some aspects of diapause have been well characterized, very little is known about the full range of molecular and biochemical modifications underlying diapause in non-model organisms. Methodology/Principal Findings: In this study we focused on the parasitic wasp, Praon volucre that exhibits a pupal diapause in response to environmental signals. System-wide metabolic changes occurring during diapause were investigated using GC-MS metabolic fingerprinting. Moreover, proteomic changes were studied in diapausing versus nondiapausing phenotypes using a combination of two-dimensional differential gel electrophoresis and mass spectrometry. We found a reduction of Krebs cycle intermediates which most likely resulted from the metabolic depression. Glycolysis was galvanized, probably to favor polyols biosynthesis. Diapausing parasitoids accumulated high levels of cryoprotective polyols, especially sorbitol. A large set of proteins were modulated during diapause and these were involved in various functions such as remodeling of cytoskeleton and cuticle, stress tolerance, protein turnover, lipid metabolism and various metabolic enzymes. Conclusions/Significance: The results presented here provide some first clues about the molecular and biochemical events that characterize the diapause syndrome in aphid parasitoids. These data are useful for probing potential commonality of parasitoids diapause with other taxa and they will help creating a general understanding of diapause underpinnings and a background for future interpretations.

Why economic dynamics matter in assessing climate change damages : illustration on extreme events

S.Hallegatte , P.Dumas , J.Charles


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Extreme events are one of the main channels through which climate and socio-economic systems interact, and it is likely that climate change will modify the probability distribution of the losses they generate. The long-term growth models used in climate change assessments, however, cannot capture the effects of such short-term shocks. To investigate this issue, a non-equilibrium dynamic model is used to assess the macroeconomic consequences of extreme events. This exercise allowed us to define the Economic Amplification Ratio, as the ratio of the overall production loss due to an event to its direct costs. This ratio could be used to improve the cost-benefit analysis of prevention measures. We found also that, unlike a Solow-like model, NEDyM exhibits a bifurcation in GDP losses : for each value of the capacity to fund reconstruction, GDP losses remain moderate if the intensity and frequency of extremes remain under a threshold value, beyond which GDP losses increase sharply. This bifurcation may partly explain why some poor countries that experience repeated natural disasters cannot develop. Applied to the specific issue of climate change, this model suggests that changes in the distribution of extremes may entail significant GDP losses in absence of specific adaptation. It suggests, therefore, that to avoid inaccurately low assessments of damages, researchers must take into account the distribution of extremes instead of their average cost and make explicit assumptions on the organization of future economies.

Downscaling scenarios of future land use and land cover changes using a participatory approach: an application to mountain risk assessment in the pyrenees (france)

A.Puissant , T.Houet , M.Gremont , L.Vacquie , Y.Forget , A.Marriotti , S.Bernardie , Y.Thiery , R.Vandromme , G.Grandjean


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Better understanding the pathways through which future socioeconomic changes might influence land use and land cover changes is a crucial step in accurately assessing the resilience of societies to mountain hazards. Participatory foresight involving local stakeholders may help building fine-scale LULCC scenarios that are consistent with the likely evolution of mountain communities. This paper develops a methodology that combines participatory approaches in downscaling socioeconomic scenarios with LULCC modelling to assess future changes in mountain hazards, applied to a case study located in the French Pyrenees. Four spatially explicit local scenarios are built each including a narrative, two future land cover maps up to 2040 and 2100, and a set of quantified LULCC. Scenarios are then used to identify areas likely to encounter land cover changes prone to affect gravitational hazards. In order to demonstrate their interest for decision-making, future land cover maps are used as input to a landslide hazard assessment model. Results highlight that reforestation will continue to be a major trend in all scenarios and confirm that the approach improves the accuracy of landslide hazard computations. This validates the interest of developing fine-scale LULCC models that account for the local knowledge of stakeholders.

Mapping the centimeter-scale spatial variability of pahs and microbial populations in the rhizosphere of two plants

A.Cebron , A.Bourceret , C.Leyval , C.De


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Rhizoremediation uses root development and exudation to favor microbial activity. Thus it can enhance polycyclic aromatic hydrocarbon biodegradation in contaminated soils. Spatial heterogeneity of rhizosphere processes, mainly linked to the root development stage and to the plant species, could explain the contrasted rhizoremediation efficiency levels reported in the literature. Aim of the present study was to test if spatial variability in the whole plant rhizosphere, explored at the centimetre-scale, would influence the abundance of microorganisms , and the abundance and activity of PAH-degrading bacteria, leading to spatial variability in PAH concentrations. Two contrasted rhizospheres were compared after 37 days of alfalfa or ryegrass growth in independent rhizotron devices. Almost all spiked PAHs were degraded, and the density of the PAH-degrading bacterial populations increased in both rhizospheres during the incubation period. Mapping of multiparametric data through geostatistical estimation revealed that although root biomass was spatially structured, PAH distribution was not. However a greater variability of the PAH content was observed in the rhizosphere of alfalfa. Yet, in the ryegrass-planted rhizotron, the Gram-positive PAH-degraders followed a reverse depth gradient to root biomass, but were positively correlated to the soil pH and carbohydrate concentrations. The two rhizospheres structured the microbial community differently: a fungus-to-bacterium depth gradient similar to the root biomass gradient only formed in the alfalfa rhizotron.

Categorizing chlordecone potential degradation products to explore their environmental fate

D.Patureau , P.Benoit , L.Mamy , R.Servien , Z.Li , E.Latrille , V.Rossard , F.Bessac , F.Martin-Laurent


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Chlordecone has been used extensively as an organochlorine insecticide but is nowadays banned and listed on annex A in The Stockholm Convention on Persistent Organic Pollutants. Although experimental evidences of biodegradation of this compound are scarce, several dechlorination products have been proposed by Dolfing et al. using Gibbs free energy calculations to explore different potential transformation routes. We here present the results of an in silico classification of chlordecone transformation products based on statistical analyses combining several environmental endpoints and structural molecular descriptors. Starting from the list of putative chlordecone TPs and considering available data on degradation routes of other organochlorine compounds, we used different clustering strategies to explore the potential environmental behaviour of putative chlordecone TPs from the knowledge on their molecular descriptors. The method offers the possibility to focus on TPs present in different classes and to infer their environmental fate. Thus, we have deduced some hypothetical trends for the environmental behaviour of TPs of chlordecone assuming that TPs, which were clustered away from chlordecone, would have different environmental fate and ecotoxicological impact compared to chlordecone. Our findings suggest that mono-and di-hydrochlordecone, which are TPs of chlordecone often found in contaminated soils, may have similar environmental behaviour in terms of persistence.

Integrated modelling of functional and structural connectivity of river corridors for european otter recovery

K.Van , C.Cavillon , T.Tormos , J.Piffady , P.Landry , Y.Souchon


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Connectivity may be structural, based on adjacency of landscape features, or functional, based on howthat adjacency translates to movement of organisms. We present a modelling approach that elucidatesboth aspects of connectivity to identify vital corridors and conservation priorities in a river network. For the dendritic network structure of river systems, at first a graph theoretic structure is developed tomodel the river network at the segment scale. To derive functional connectivity, a Bayesian hierarchicalmodelling of species dispersal is applied to infer the influence of riparian corridor characteristics to thespecies colonization. The integration of the functional and structural component is realized with a graph-theoretic con-nectivity measure. With this approach, the European otter colonization of the Loire river basin over 25years is modelled on the basis of large datasets on riparian corridor land use and hydromorphologicalcharacteristics of a 17,000 km river network. Channel straightening and riparian forest fragmentation aredetermined to be key elements to the functional connectivity. Road infrastructure is distinguished as acritical habitat factor, but not so much an obstacle for the species movement in the riparian corridor. Inte-gration of the Bayesian model posterior colonization probability in the integrated connectivity analysisreveals the importance of the river network density to the otter colonization and locates conservationpriorities mainly in the lower parts of the river basin. Synthesis and applications: Both functional and structural connectivity are essential elements in thecontexts of ecological network identification for species conservation and recovery. We successfullydeveloped an integrated modelling of both components of connectivity that highlighted the importanceof the downstream basin for a well-connected ecological network for the otter.

Rapid evolutionary responses of life history traits to different experimentally-induced pollutions in caenorhabditis elegans

B.Goussen , D.Reale , J.Bonzom , M.Dutilleul , S.Galas , C.Lecomte , F.Daian


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Background: Anthropogenic disturbances can lead to intense selection pressures on traits and very rapid evolutionary changes. Evolutionary responses to environmental changes, in turn, reflect changes in the genetic structure of the traits, accompanied by a reduction of evolutionary potential of the populations under selection. Assessing the effects of pollutants on the evolutionary responses and on the genetic structure of populations is thus important to understanding the mechanisms that entail specialization to novel environmental conditions or resistance to novel stressors. Results: Using an experimental evolution approach we exposed Caenorhabditis elegans populations to uranium, salt and alternating uranium-salt environments over 22 generations. We analyzed the changes in the average values of life history traits and the consequences at the demographic level in these populations. We also estimated the phenotypic and genetic variance structure of these traits at different generations. Compared to populations in salt, populations in uranium showed a reduction of the stability of their trait structure and a higher capacity to respond by acclimation. However, the evolutionary responses of traits were generally lower for uranium compared to salt treatment; and the evolutionary responses to the alternating uraniumsalt environment were between those of constant environments. Consequently, at the end of the experiment, the population rate of increase was higher in uranium than in salt and intermediate in the alternating environment. Conclusions: Our multigenerational experiment confirmed that rapid adaptation to different polluted environments may involve different evolutionary responses resulting in demographic consequences. These changes are partly explained by the effects of the pollutants on the genetic variance structure of traits and the capacity of acclimation to novel conditions. Finally, our results in the alternating environment may confirm the selection of a generalist type in this environment.

Modeling plankton ecosystem functioning and nitrogen fluxes in the oligotrophic waters of the beaufort sea, arctic ocean: a focus on light-driven processes

M.Babin , B.Zakardjian , F.Joux , P.Raimbault , V.Le , H.Xie


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The Arctic Ocean undergoes profound changes of its physical and biotic environments due to climate change. In some areas of the Beaufort Sea, the stronger haline stratification observed in summer alters the plankton ecosystem structure, functioning and productivity, promoting oligotrophy. A one-dimension physicalbiological coupled model based on the large multiparametric database of the Malina project in the Beaufort Sea was used to infer the plankton ecosystem functioning and related nitrogen fluxes and to assess the model sensitivity to key light-driven processes involved in nutrient recycling and phytoplankton growth. The coupled model suggested that ammonium photochemically produced from photosensitive dissolved organic nitrogen was a necessary nitrogen source to achieve the observed levels of microbial biomass and production. Photoammonification directly and indirectly contributed to 70% and 18. 5% of the 010 m and whole water column, respectively, simulated primary production. The model also suggested that variable carbon to chlorophyll ratios were required to simulate the observed herbivorous versus microbial food web competition and realistic nitrogen fluxes in the Beaufort Sea oligotrophic waters. In face of accelerating Arctic warming, more attention should be paid in the future to the mechanistic processes involved in food webs and functional group competition, nutrient recycling and primary production in poorly productive waters of the AO, as they are expected to expand rapidly.

Expert guided integration of induced knowledge into a fuzzy knowledge base

S.Guillaume , L.Magdalena


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Resume : Cet article propose une methode pour construire des systemes a la fois precis et interpretables en integrant dans la meme base de connaissance des elements de connaissance experte et d'autres issus de donnees. Pour favoriser la cooperation entre l'expert et les donnees, le processus d'induction est encadre par de severes contraintes qui permettent a l'expert de garder le controle tout au long du processus. La procedure est sequentielle. Dans un premier temps un partitionnement flou est concu a partir des donnees et de la connaissance experte. La compatibilite entre les deux types de partitions est verifiee a partir de trois criteres : domaine de variation, granularite et interpretation semantique. Puis, des regles expertes et induites sont generees en tenant compte de ces partitions. Les deux bases de regles peuvent alors etre fusionnees en une seule. Grace au partitionnement commun, la comparaison des regles peut se faire au seul niveau linguistique. Les eventuels conflits sont geres et les principales qualites d'une base de regles, coherence, absence de redondance et completude sont etudiees. La premiere etape est completement decrite dans le cadre de l'article, tandis que la seconde est seulement introduite. / his paper proposes a method for building accurate and interpretable systems by integrating expert and induced knowledge into a single knowledge base. To favor the cooperation between expert knowledge and data, the induction process is run under severe constraints to ensure the fully control of the expert. The procedure is made up of two hierarchical steps. Firstly, a common fuzzy input space is designed according to both the data and expert knowledge. The compatibility of the two types of partitions, expert and induced, is checked according to three criteria: range, granularity and semantic interpretation. Secondly, expert rules and induced rules are generated according to the previous common fuzzy input space. Then, induced and expert rules have to be merged into a new rule base. Thanks to the common universe resulting from the first step, rule comparison can be made at the linguistic level only. The possible conflict situations are managed and the most important rule base features, consistency, redundancy and completeness, are studied. The first step is thoroughly described in this paper, while the second is only introduced.

Hydraulic habitat alteration at the catchment scale: impacts of groundwater abstraction in the seine‑normandie catchment

J.Belliard , C.Miguel , N.Lamouroux , H.Pella , B.Labarthe , N.Flipo , M.Akopian


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Among available tools for estimating the ecological impacts of discharge alteration, hydraulic habitat models link hydraulic models of streams with biological models that reflect the preferences of organisms for hydraulics. The simplification of habitat models now enables their application at the catchment scale for estimating the impacts on habitats of discharge and abstraction management. In the Seine-Normandie catchment in France, we propose an original linkage of a distributed hydrological model, a fish species distribution model and hydraulic habitat models. We show that groundwater abstraction in the catchment cause a moderate alteration of low flows and a weak alteration of usable habitats for fish. However, the spatial distribution of alterations helps to identify regions where impacts are stronger , due to strong abstraction and/or the presence of demanding fish species. An uncertainty analysis indicates that our results should be interpreted at the regional scale only; they allow identifying regions that would deserve more detailed analyses. Our results open many perspectives for taking into account habitat issues in quantitative water management at the catchment scale. Resume : Parmi les outils permettant d'evaluer les impacts ecologiques des alterations de debit des cours d'eau, les modeles d'habitat hydraulique couplent une modelisation hydraulique avec des modeles des exigences ecologiques des especes aquatiques. La simplification de ces modeles permet de les appliquer a l'echelle des bassins versants pour quantifier l'impact sur l'habitat hydraulique de la gestion des debits et des prelevements. Nous realisons sur le bassin Seine-Normandie un couplage original d'un modele hydrologique distribue, de modeles de distribution spatiale des poissons et de modeles d'habitat simplifies. Ce couplage montre que les prelevements en nappe generent une alteration des debits d'etiage moderee qui se traduit pour les especes en place par une alteration d'habitat favorable faible. Neanmoins, la repartition spatiale des alterations permet d'identifier les territoires les plus impactes , du fait de prelevements importants et/ou de la presence d'especes plus exigeantes. Une analyse des incertitudes suggere d'interpreter les resultats a l'echelle de territoires ou plus large, et l'exercice permet donc d'identifier les territoires sur lesquels une modelisation plus fine serait utile. Ces resultats ouvrent de nombreuses perspectives pour prendre en compte les milieux aquatiques dans la gestion quantitative des bassins.
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