CNRS Biogeosciences Laboratory
CNRS Biogeosciences Laboratory
Cornet S.,IRD Montpellier |
Cornet S.,CNRS Center of Evolutionary and Functional Ecology |
Bichet C.,CNRS Biogeosciences Laboratory |
Larcombe S.,University of Oxford |
And 2 more authors.
Journal of Animal Ecology | Year: 2014
Host resources can drive the optimal parasite exploitation strategy by offering a good or a poor environment to pathogens. Hosts living in resource-rich habitats might offer a favourable environment to developing parasites because they provide a wealth of resources. However, hosts living in resource-rich habitats might afford a higher investment into costly immune defences providing an effective barrier against infection. Understanding how parasites can adapt to hosts living in habitats of different quality is a major challenge in the light of the current human-driven environmental changes. We studied the role of nutritional resources as a source of phenotypic variation in host exploitation by the avian malaria parasite Plasmodium relictum. We investigated how the nutritional status of birds altered parasite within-host dynamics and virulence, and how the interaction between past and current environments experienced by the parasite accounts for the variation in the infection dynamics. Experimentally infected canaries were allocated to control or supplemented diets. Plasmodium parasites experiencing the two different environments were subsequently transmitted in a full-factorial design to new hosts reared under similar control or supplemented diets. Food supplementation was effective since supplemented hosts gained body mass during a 15-day period that preceded the infection. Host nutrition had strong effects on infection dynamics and parasite virulence. Overall, parasites were more successful in control nonsupplemented birds, reaching larger population sizes and producing more sexual (transmissible) stages. However, supplemented hosts paid a higher cost of infection, and when keeping parasitaemia constant, they had lower haematocrit than control hosts. Parasites grown on control hosts were better able to exploit the subsequent hosts since they reached higher parasitaemia than parasites originating from supplemented hosts. They were also more virulent since they induced higher mass and haematocrit loss. Our study highlights that parasite virulence can be shaped by the host nutritional status and that parasite can adapt to the environment provided by their hosts, possibly through genetic selection. © 2013 British Ecological Society.
Thevenot M.,CNRS Biogeosciences Laboratory |
Dousset S.,CNRS Interdisciplinary Laboratory for Continental Environments
Pedosphere | Year: 2015
Diuron is frequently detected in surface- and groundwater under the vineyards, where organic amendments are often used, in Burgundy of France. Undisturbed column experiments were conducted to study the influence of three composted organic amendments on diuron leaching through columns of two vineyard soils from Vosne-Romanée (VR, calcareous Cambisol) and Beaujolais (Bj, sandy Leptosol), France. Bromide (used as non-reactive tracer) and diuron breakthrough curves (BTCs) were analyzed using convectivedispersive equation (CDE), two-region (mobile-immobile, MIM) and two-site models. No influence of the composts was observed on the bromide recovery rates. The CDE model described well the bromide BTCs for all columns of the Bj soil and seven of the VR soil, suggesting a homogeneous water flow. However, for five VR soil columns, the MIM model fitted better, suggesting a partition of the water flow (15%-50% of matrix flow). The texture, the coarse material content and the tillage of the VR soil could explain this heterogeneity. However, for all columns, diuron leaching was greater through the Bj soil (46%-68%) than the VR soil (28%-39%). The compost addition resulted in a contrasting effect on diuron leaching: no difference or a decrease was observed for the VR soil, probably due to an increase of adsorption sites, whereas no difference or an increase was observed for the Bj soil possibly because of interactions and/or competition of diuron with the compost water-extractable organic matter which could facilitate its transport. All the diuron BTCs were best described using the two-site model, suggesting a large proportion of time-dependent sorption sites (30%-50%). The soil type and the nature of the amendments had contrasting influences on diuron transport. Composts with a high water-soluble fraction must be avoided in sandy soils to reduce the risk of groundwater contamination. © 2015 Soil Science Society of China.
Arnoux E.,CNRS Biogeosciences Laboratory
Heredity | Year: 2014
Mobile organisms are expected to show population differentiation only over fairly large geographical distances. However, there is growing evidence of discrepancy between dispersal potential and realized gene flow. Here we report an intriguing pattern of differentiation at a very small spatial scale in the forest thrush (Turdus lherminieri), a bird species endemic to the Lesser Antilles. Analysis of 331 individuals from 17 sampling sites distributed over three islands revealed a clear morphological and genetic differentiation between these islands isolated by 40-50 km. More surprisingly, we found that the phenotypic divergence between the two geographic zones of the island of Guadeloupe was associated with a very strong genetic differentiation (Fst from 0.073-0.153), making this pattern a remarkable case in birds given the very small spatial scale considered. Molecular data (mitochondrial control region sequences and microsatellite genotypes) suggest that this strong differentiation could have occurred in situ, although alternative hypotheses cannot be fully discarded. This study suggests that the ongoing habitat fragmentation, especially in tropical forests, may have a deeper impact than previously thought on avian populations.Heredity advance online publication, 2 July 2014; doi:10.1038/hdy.2014.56.
Vigaud N.,CNRS Biogeosciences Laboratory |
Pohl B.,CNRS Biogeosciences Laboratory |
Cretat J.,CNRS Biogeosciences Laboratory
Climate Dynamics | Year: 2012
The Weather Research and Forecasting model (WRF) forced by ERA40 re-analyses, is used to examine, at regional scale, the role of key features of the local atmospheric circulation on the origin and development of Tropical Temperate Troughs (TTTs) representing a major contribution to South African rainfall during austral summer. A cluster analysis applied on 1971-2000 ERA40 and WRF simulated daily outgoing longwave radiation reveals for the November-February season three coherent regimes characteristic of TTTs over the region. Analyses of WRF simulated TTTs suggest that their occurrence is primarily linked with mid-latitude westerly waves and their phasing. Ensemble experiments designed for the case of austral summer 1996/1997 allow to examine the reproducibility of TTT events. The results obtained illustrate the importance of westerly waves phasing regarding the persistence of rain-producing continental TTT events. Moreover, oceanic surface conditions prevailing over the Agulhas current regions of the South West Indian Ocean (SWIO) are also found to influence TTT persistence for regional experiments with an oceanic mixed layer, warmer sea surface temperatures being associated with increased moisture advection from the SWIO where latent heat release is enhanced, favoring baroclinic instability and thus sustaining convection activity locally. © 2012 Springer-Verlag.
Forel M.-B.,Wuhan University |
Crasquin S.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments |
Kershaw S.,Brunel University |
Collin P.-Y.,CNRS Biogeosciences Laboratory
Terra Nova | Year: 2013
We present the first study of micro-crustaceans (ostracods) associated with microbial crusts in the aftermath of the most devastating extinction, the end-Permian extinction (EPE). These post-extinction microbialites dominated shallow shelf marine environments and were traditionally considered as devoid of any associated fauna. We present a micro-palaeontological analysis of a large record from microbial and non-microbial settings following the EPE. This dataset documents the proliferation of ostracods strictly associated with microbialites. Based on the diet of extant ostracods and uniformitarianism, we propose that the abundant microbes in the mats served as an unlimited food supply. Photosynthetic cyanobacteria may also have locally provided oxygen under low oxygen conditions interpreted by others for the microbialites. Microbialites provided a specialised environment that may have acted as refuge for ostracods in the immediate aftermath of the EPE. The surviving faunas may have been progenitors for the starting of the latter radiation. © 2012 Blackwell Publishing Ltd.
Martiny N.,CNRS Biogeosciences Laboratory |
Chiapello I.,CNRS Optical Atmosphere Laboratory
Atmospheric Environment | Year: 2013
Recently, mineral dust has been suspected to be one of the important environmental risk factor for meningitis epidemics in West Africa. The current study is one of the first which relies on long-term robust aerosol measurements in the Sahel region to investigate the possible impact of mineral dust on meningitis cases (incidence). Sunphotometer measurements, which allow to derive aerosol and humidity parameters, i.e., aerosol optical thickness, Angström coefficient, and precipitable water, are combined with quantitative epidemiological data in Niger and Mali over the 2004-2009 AMMA (African Monsoon Multidisciplinary Analysis) program period. We analyse how the extremely high aerosol loads in this region may influence both the calendar (onset, peaks, end) and the intensity of meningitis. We highlight three distinct periods: (i) from November to December, beginning of the dry season, humidity is weak, there is no dust and no meningitis cases; (ii) from January to April, humidity is still weak, but high dust loads occur in the atmosphere and this is the meningitis season; (iii) from May to October, humidity is high and there is no meningitis anymore, in presence of dust or not, which flow anyway in higher altitudes. More specifically, the onset of the meningitis season is tightly related to mineral dust flowing close to the surface at the very beginning of the year. During the dry, and the most dusty season period, from February to April, each meningitis peak is preceded by a dust peak, with a 0-2 week lead-time. The importance (duration, intensity) of these meningitis peaks seems to be related to that of dust, suggesting that a cumulative effect in dust events may be important for the meningitis incidence. This is not the case for humidity, confirming the special contribution of dust at this period of the year. The end of the meningitis season, in May, coincides with a change in humidity conditions related to the West African Monsoon. These results, which are interpreted in the context of recent independent epidemiological studies on meningitis highlight, (i) the particular role of dust during the dry season (low humidity conditions) on the onset and the intra-seasonal variability of the meningitis season; (ii) the specific role of high humidity at the end of the meningitis season in two Sahelian countries particularly affected by the disease. © 2013 Elsevier Ltd.
Sohm B.,CNRS Interdisciplinary Laboratory for Continental Environments |
Immel F.,CNRS Biogeosciences Laboratory |
Bauda P.,CNRS Interdisciplinary Laboratory for Continental Environments |
Pagnout C.,CNRS Interdisciplinary Laboratory for Continental Environments
Proteomics | Year: 2015
Large-scale production and incorporation of titanium dioxide nanoparticles (NP-TiO2) in consumer products leads to their potential release into the environment and raises the question of their toxicity. The bactericidal mechanism of NP-TiO2 under UV light is known to involve oxidative stress due to the generation of reactive oxygen species. In the dark, several studies revealed that NP-TiO2 can exert toxicological effects. However, the mode of action of these nanoparticles is still controversial. In the present study, we used a combination of fluorescent probes to show that NP-TiO2 causes Escherichia coli membrane depolarization and loss of integrity, leading to higher cell permeability. Using both transcriptomic and proteomic global approaches we showed that this phenomenon translates into a cellular response to osmotic stress, metabolism of cell envelope components and uptake/metabolism of endogenous and exogenous compounds. This primary mechanism of bacterial NP-TiO2 toxicity is supported by the observed massive cell leakage of K+/Mg2+ concomitant with the entrance of extracellular Na+, and by the depletion of intracellular ATP level. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Dommergues J.-L.,CNRS Biogeosciences Laboratory
Revue de Paleobiologie | Year: 2015
Three micromorph ammonites collected in the area of Semur-en-Auxois - the type-locality of the Sinemurian stage - are studied in the present paper. They are housed in the municipal museum of Semur-en-Auxois (2 spécimens) and in the Natural history museum of Marseille (1 specimen). These three ammonites are attributed to a new genus : Hemicymbites nov. gen. The two specimens of the museum of Semur-en-Auxois are interpreted as a new species : H. tardiornatum nov. gen., nov. sp. and the specimen of the museum of Marseille is here designated as the lectotype of Hemicymbites semicostulatus (Reynès, 1879). These three ammonites are the only currently known specimens belonging to the new genus Hemicymbites. Despite their small adulte sizes, they are characterized by a dramatic change during ontogeny between a smooth Cymbites-like phragmocône and a much more evolute, quasi-serpenticone and coarsly ribbed body-chamber. Even if accurate stratigraphical data are missing, these micromorph ammonites can be plausibly attributed to the Early Sinemurian. They show on the venter some slight indications of a weak keel flanked by faint flat areas. Although rather subtle, these traits coupled with a credible Early sinemurian age are consistent with a possible attribution to the Arietitidae family s.l. These new results support the impression that the ammonite faunas are, during the Sinemurian and especially during the Early Sinemurian, characterised by a remarkable disparity in adult size. Nevertheless, the micromorph Cymbites-like sinemurian ammonites are difficult to understand in terms of palaeobiodiversity. Indeed, these tiny ammonites can be either distinct species characterized by both small adult size and associated distinctive "traits of life history" or microconch morphs belonging to until now unidentified dimorphic couples.
Camberlin P.,CNRS Biogeosciences Laboratory
Climate Dynamics | Year: 2016
Relationships between daily precipitation and daily maximum and minimum temperature (Tx and Tn, respectively) are analyzed at station level over the Greater Horn of Africa (GHA). Rainfall occurrence is associated with either above normal Tn (mostly in cool highland areas) or below normal Tn (especially lowland, hot environments and early parts of the rainy season). Tx generally displays a more consistent response to rainfall occurrence, with cooling peaking 1 day after the rainfall event. However there is often a persistence of this cooling several days after the rainfall event, and the amplitude of the cooling is also greater for heavy rainfall events. These temperature anomalies are thought to be a response to cloudiness (concurrent reduced Tx and concurrent enhanced Tn) and soil moisture (reduced Tx and Tn, suggested to reflect evaporative cooling). These relationships are of relevance to the interpretation of temperature trends. From 1973 to 2013, the GHA shows a clear warming signal, for both Tn (+0.20 to +0.25 °C/decade depending on seasons) and Tx (+0.17 to +0.22 °C/decade). Rainfall shows both negative (mostly between February and July) and positive trends (mostly in October–December). Given the superimposition of temperature and rainfall trends in parts of the GHA and the covariations between daily rainfall and both Tx and Tn, regression models are used to extract the rainfall influence on temperature, accounting for lag effects up to 4 days. The daily residuals from these models are used to depict temperature variations independent from precipitation variations. At some stations, trends computed on these residuals noticeably differ from the raw Tx trends. When averaged across the GHA, these effects do not exceed −0.06 to +0.03 °C/decade (depending on the month) for Tx, and are marginal for Tn, thus do not strongly modify the magnitude of the warming in the last 40 years. Nevertheless, these results show that precipitation-temperature relationships must be addressed when analyzing temperature changes. © 2016 Springer-Verlag Berlin Heidelberg
Monceau K.,CNRS Agroecology Lab |
Monceau K.,CNRS Biogeosciences Laboratory |
Bonnard O.,CNRS Agroecology Lab |
Thiery D.,CNRS Agroecology Lab
Journal of Pest Science | Year: 2014
The yellow-legged hornet (Vespa velutina) is the first invasive Vespidae predator of honeybees to be accidentally introduced into Europe from Asia. In the current pollinator decline, V. velutina is an additional stressor for honeybees and other pollinators. Although V. velutina contributes to the loss of honeybee colonies, little is known about its biology and behaviour both in the native and in the invaded area. Here, we review the current knowledge of this species and describe its life cycle and life history traits (reproduction, overwintering, foraging and dispersal) in the light of the biology of other Vespidae. We also review the impact of this species on ecosystems, on the economics of beekeeping, and on human health (this species being potentially deadly for allergic people). Based on this information and on previous worldwide experiences with Vespidae invasions, we propose key research topics for the development of effective management plans. We identify methods to limit the impact and proliferation of V. velutina in Europe that are based on nest destruction, trapping, population genetics, and biological control. In our opinion, research effort on the means to detect and destroy V. velutina nests at an early stage is required in order to short-circuit the colony cycle and thus limit both its impact on honeybees and its expansion through Europe. Finally, we discuss the impact of this biological invasion on the development of methods that should be used to manage alien species in the future. © 2013 Springer-Verlag Berlin Heidelberg.