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.
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.
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.
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.
A new genus and a new species of Sinemurian micromorph ammonite in eastern France (Côte-d'Or). Hemicymbites tardiornatum nov. gen, nov. sp. [Un nouveau genre et une nouvelle espèce d'ammonite micromorphe dans le Sinémurien de l'Est de la France (Côte-d'Or)]
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.