Earth Sciences

Apres le deluge : evolution geomorphologique du delta du danube apres la reconnexion mer noire - mediterranee et ses implications sur le peuplement eneolithique / chalcolithique

L.Carozza , J.Carozza , M.Danu , V.Radu , F.Leveque , C.Micu , A.Burens-Carozza , G.Opreanu , C.Haita


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In this work, we document the evolution of the upper Danube delta using archaeological, geomorphological and geoarchaeological approaches, after the discovery, in the 90's, of the oldest human settlement close to Mila 23 district. In-site and out-site fieldwork allows us to refine the Danube delta early evolution from 5,600 to 4,000 cal. yr BC. During this period, it functions like a fresh bayhead delta, flowing into a huge lagoon isolated from the open sea by the Letea-Caraorman spit. Then, lagoon water level rose rapidly due to an eustatic rise, and possibly from an unusual highstand of sealevel resulting from wet conditions. The settlement was then partially flooded and abandoned around 4,450 cal. yr BC. Resume : Dans ce travail, l'evolution de la zone interne du delta du Danube est apprehendee a partir de travaux geoarcheologiques et geomorphologiques realises dans le district de Mila 23, suite a la decouverte de la plus vieille occupation humaine du delta dans les annees 90. Les travaux sur site et hors site ont permis de preciser les stades precoces de l'evolution du delta entre 5 600 et 4 000 ans cal. av. J. -C. Celui-ci evolue comme un delta lagunaire en eau douce, s'epandant dans un large lagon separe de la mer par la ride de Letea-Caraorman. La remontee rapide du niveau lagunaire, sous l'effet de la remontee eustatique et peut-etre d'une sur cote liee a un evenement humide, ont conduit a une submersion partielle du site et probablement a son abandon vers 4 450 ans cal. av. J. -C.

Local molecular clocks in three nuclear genes: divergence times for rodents and other mammals and incompatibility among fossil calibrations.

F.Delsuc , E.J , M.J , D.Huchon


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Reconstructing the chronology of mammalian evolution is a debated issue between molecule-and fossil-based inferences. A methodological limitation of molecules is the evolutionary rate variation among lineages, precluding the application of the global molecular clock. We considered 2422 first and second codon positions of the combined ADRA2B, IRBP, and vWF nuclear genes for a well-documented set of placentals including an extensive sampling of rodents. Using seven independent calibration points and a maximum-likelihood framework, we evaluated whether molecular and paleontological estimates of mammalian divergence dates may be reconciled by the local molecular clocks approach, allowing local constancy of substitution rates with variations at larger phylogenetic scales. To handle the difficulty of choosing among all possible rate assignments for various lineages, local molecular clocks were based on the results of branch-length and two-cluster tests. Extensive lineage-specific variation of evolutionary rates was detected, even among rodents. Cross-calibrations indicated some incompatibilities between divergence dates based on different paleontological references. To decrease the impact of a single calibration point, estimates derived from independent calibrations displaying only slight reciprocal incompatibility were averaged. The divergence dates inferred for the split between mice and rats was younger than previously published molecular estimates. The most recent common ancestors of rodents, primates and rodents, boreoeutherians, and placentals were estimated to be, respectively, approximately 60, 70, 75, and 78 Myr old. Global clocks, local clocks, and quartet dating analyses suggested a Late Cretaceous origin of the crown placental clades followed by a Tertiary radiation of some placental orders like rodents.

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.

Looking for the bird kiss: evolutionary scenario in sauropsids.

S.Dufour , P.Chemineau , A.Lafont , J.Pasquier , K.Rousseau , B.Querat


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BACKGROUND: The neuropeptide Kiss and its receptor KissR are key-actors in the brain control of reproduction in mammals, where they are responsible for the stimulation of the activity of GnRH neurones. Investigation in other vertebrates revealed up to 3 Kiss and 4 KissR paralogs, originating from the two rounds of whole genome duplication in early vertebrates. In contrast, the absence of Kiss and KissR has been suggested in birds, as no homologs of these genes could be found in current genomic databases. This study aims at addressing the question of the existence, from an evolutionary perspective, of the Kisspeptin system in birds. It provides the first large-scale investigation of the Kisspeptin system in the sauropsid lineage, including ophidian, chelonian, crocodilian, and avian lineages. RESULTS: Sauropsid Kiss and KissR genes were predicted from multiple genome and transcriptome databases by TBLASTN. Phylogenetic and syntenic analyses were performed to classify predicted sauropsid Kiss and KissR genes and to re-construct the evolutionary scenarios of both gene families across the sauropsid radiation. Genome search, phylogenetic and synteny analyses, demonstrated the presence of two Kiss genes and of two KissR genes in the sauropsid lineage. These four genes, also present in the mammalian lineage, would have been inherited from their common amniote ancestor. In contrast, synteny analyses supported that the other Kiss and KissR paralogs are missing in sauropsids as in mammals, indicating their absence in the amniote lineage. Among sauropsids, in the avian lineage, we demonstrated the existence of a Kiss2-like gene in three bird genomes. The divergence of these avian Kiss2-like sequences from those of other vertebrates, as well as their absence in the genomes of some other birds, revealed the processes of Kiss2 gene degeneration and loss in the avian lineage. CONCLUSION: These findings contribute to trace back the evolutionary history of the Kisspeptin system in amniotes and sauropsids, and provide the first molecular evidence of the existence and fate of a Kiss gene in birds.

Modeling social-ecological feedback effects in the implementation of payments for environmental services in pasture-woodlands

A.Buttler , F.Gillet , R.Huber , S.Briner , A.Peringer , S.Lauber , R.Seidl , A.Widmer , Q.Bao , C.Hirschi


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An effective implementation of payment for environmental services must allow for complex interactions of coupled social-ecological systems. We present an integrative study of the pasture-woodland landscape of the Swiss Jura Mountains combining methods from natural and social sciences to explore feedback between vegetation dynamics on paddock level, farm-based decision making, and policy decisions on the national political level. Our modeling results show that concomitant climatic and socioeconomic changes advance the loss of open grassland in silvopastoral landscapes. This would, in the longer term, deteriorate the historical wooded pastures in the region, which fulfill important functions for biodiversity and are widely considered as landscapes that deserve protection. Payment for environmental services could counteract this development while respecting historical land-use and ecological boundary conditions. The assessed policy feedback process reveals that current policy processes may hinder the implementation of PES, even though a payment for the upkeep of wooded pasture would generally enjoy the backing of the relevant policy network. To effectively support the upkeep of the wooded pastures in the Jura, concomitant policy changes, such as market deregulation, must also be taken into account.

Identification and Characterization of PlAlix, the Alix Homologue From the Mediterranean Sea Urchin Paracentrotus Lividus

A.L , D.Bernardo, , M.G , R.D , D.A , B.A


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The sea urchin provides a relatively simple and tractable system for analyzing the early stages of embryo development. Here, we use the sea urchin species, Paracentrotus lividus, to investigate the role of Alix in key stages of embryogenesis, namely the egg fertilization and the first cleavage division. Alix is a multifunctional protein involved in different cellular processes including endocytic membrane trafficking, filamentous (F)-actin remodeling, and cytokinesis. Alix homologues have been identified in different metazoans; in these organisms, Alix is involved in oogenesis and in determination/differentiation events during embryo development. Herein, we describe the identification of the sea urchin homologue of Alix, PlAlix. The deduced amino acid sequence shows that Alix is highly conserved in sea urchins. Accordingly, we detect the PlAlix protein cross-reacting with monoclonal Alix antibodies in extracts from P. lividus, at different developmental stages. Focusing on the role of PlAlix during early embryogenesis we found that PlAlix is a maternal protein that is expressed at increasingly higher levels from fertilization to the 2-cell stage embryo. In sea urchin eggs, PlAlix localizes throughout the cytoplasm with a punctuated pattern and, soon after fertilization, accumulates in larger puncta in the cytosol, and in microvilli-like protrusions. Together our data show that PlAlix is structurally conserved from sea urchin to mammals and may open new lines of inquiry into the role of Alix during the early stages of embryo development

The PREDICTS Database: a Global Database of How Local Terrestrial Biodiversity Responds to Human Impacts

e.al. , I.D. , J.M. , H.S. , B.D. , D.J. , H.M. , D.Palma, , L.I. , N.T. , B.H. , K.L. , C.S. , H.L. , P.H. , S.R. , C.A. , C.D. , E.S. , G.M. , K.V.


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Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species' threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project - and avert - future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups - including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems - http://www.predicts.org.uk). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.Lawrence N. Hudson ... Konstans Wells ... et al

How do biodiversity patterns of river animals emerge from the distributions of common and rare species?

J.Cucherousset , R.Cereghino , F.Santoul , J.Figuerola


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We studied the patterns of commonness and rarity for one vertebrate and four freshwater insect taxa in southwestern France , and we analysed the relationships between the location of sites and the contribution of commonness and rarity to species richness within a large stream system. Richness patterns in fish and aquatic insects were related to the location of sites within the stream system. The number of common and rare fish species increased from up-to downstream areas as a result of downstream additions of species. The number of common insect species peaked in the intermediate section of the river continuum, whereas rarity increased with decreasing elevation. In all taxa, common species gave a closer approximation to overall patterns of species richness than did rare ones. The biodiversity patterns of river animals emerged from convergence in the distributions of common and rare species , or mostly from the distribution of common species. However, in fish, Ephemeroptera and Plecoptera, the rarer species became almost equally, or more strongly correlated with overall species richness when increasing information along the common-to-rare and rare-to-common sequences. These patterns suggested that rarer species show a similar or stronger affinity, on a species-for-species basis, for high richness areas than do the commoner species. These schemes have implications for biodiversity assessments, as studies using common species richness to target important areas for monitoring or conservation efforts within stream systems will not necessarily identify areas important for rare species, and vice versa.

Marine biodiversity - warming vs. biological invasions and overfishing in the mediterranean sea: take care, one train can hide another

T.Perez , D.Thibault , C.Fernandez , M.Verlaque , C.Lejeusne , C.Boudouresque , A.Blanfune , T.Thibaut , S.Ruitton


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Biodiversity means the variety of life, encompassing levels of complexity from within species to across ecosystems. Biodiversity therefore includes several dimensions: evolutionary scale , functional scale, organizational scale , spatial scale and heterogeneity diversity. Biodiversity can therefore be measured in different and complementary ways, thus involving the use of at least 200 different metrics, which can suggest different and contrasting conclusions. It is worth emphasizing that species richness may be the least appropriate metric, despite its popular acceptance. There is a growing tendency for stakeholders, managers, government officials, environmentalists, scientists, politicians and the media to focus, as concerns threats to biodiversity, on species richness and climate change. However, focusing on climate warming can mask other stressors that, today, and perhaps for decades to come, may have more impact on ecosystems than global warming. In the Mediterranean Sea, the overall impact of Non-Indigenous Species and overfishing on species diversity, ecosystem diversity and ecosystem functioning exceeds to a greater or lesser degree the direct impact of warming. Drastically altered functioning patterns, and even new ecosystems are spreading throughout the Mediterranean Sea. This trend is likely to become more pronounced over the next decades. Ecosystem goods and services are also being profoundly altered, generally towards a decline, as illustrated by the overgrazed barren grounds of the eastern basin, which no longer support fisheries, by the impact of the Caulerpa meadows on the scuba diving business and the economic value of the fisheries of the western basin, by the brackish lagoon ecosystems and by the blooms of the introduced comb jelly Mnemiopsis leidyi in the Black Sea, before the arrival of its predator Beroe ovata. Here, we draw attention to the fact that, at this moment and probably also in the future, the huge flow of NISs and overfishing constitute worrying issues, although largely ignored by stakeholders and political authorities. Take care: Un train peut en cacher un autre , that is to say the impact of warming may contribute to hiding other effects, of at least equal gravity, such as biological invasions and overfishing.

Contrasted taxonomic, phylogenetic and functional diversity patterns in semi-natural permanent grasslands along an altitudinal gradient

A.Mouly , F.Gillet , R.Perronne , L.Mauchamp


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Background and aims Recent methodological and theoretical advances in community ecology have allowed more robust exploration of complementary facets of biodiversity in plant communities. Focusing on semi-natural permanent grasslands of the French Jura Mountains, we assessed how taxonomic, phylogenetic and functional diversity metrics vary among three phytosociological vegetation units. Methods We selected a sample of 135 releves out of a phytosociological database, depicting three phytosociological orders and including 381 vascular plant species. We built a phylogenetic tree based on sequences of two genes encoding chloroplast proteins, from which we computed phylogenetic diversity metrics that we compared to various taxonomic, single-trait and multi-trait functional metrics, including community-weighted means of functional traits. Key results Most diversity metrics and CWMs significantly differed among vegetation units. Within each facet of biodiversity, the different metrics showed complementary results. Moreover, even when considering diversity metrics comparable in mathematical terms, i. e. based on Rao quadratic entropy, the results were largely non-redundant among the facets of biodiversity. Phylogenetic diversity and multi-trait functional diversity show opposite responses to vegetation units, as well as a low phylogenetic signal. These two results suggest that phylogenetic diversity cannot be used as a simple proxy for functional diversity. Conclusion This study highlights the importance of taking into consideration different facets for a better understanding of biodiversity. In particular, phylogenetic and functional facets appear highly informative, and could thus be used in addition to taxonomic diversity metrics as indicators of conservation value.

Political ecology of private forest fencing in the french sologne: what are the social and environmental issues at stake in the dispute?

B.Hautdidier , M.Baltzinger , J.Mouche , M.Blondet


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We propose an interdisciplinary approach designed to study the spread of private fencing in the French Sologne as a socio-ecological phenomenon. We conducted two parallel approaches: a study of how fencing may affect spatial use by deer and an interview campaign in order to elucidate which human values were at stake in the fencing debate. To this end we applied a Political ecology approach in order to articulate these two kinds of results. We highlighted two competing discourses regarding hunting-oriented private properties, showing that this contention is based on the replacement of game birds by big game over the past thirty years, which went along with the spread of fencing. Resume : Cet article propose une approche interdisciplinaire visant a etudier la dynamique d'engrillagement en Sologne sous ses aspects humains et ecologiques. Des travaux ont ete menes, relates par ailleurs dans des manuscrits soumis a des revues d'ecologie, afin de decrire le comportement spatial des cerfs de Sologne, en presence de grillages. Un travail d'enquete a egalement ete effectue, portant sur les valeurs associees a l'environnement en Sologne telles qu'elles etaient mises a jour par l'evocation des engrillagements. Nous utilisons ici une approche de type political ecology pour mettre en regard ces deux types de resultats. Nous mettons en evidence deux discours concurrents sur les formes de legitimation des proprietes cynegetiques, dont l'opposition s'articule autour du remplacement du petit gibier par le grand au cours de ces trente dernieres annees. Nous expliquons le role joue par les engrillagements dans cette mise en concurrence.

Effects of burial on leaf litter quality, microbial conditioning and palatability to three shredder taxa

E.Chauvet , J.Cornut , A.Elger , M.Danger


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1. Heterotrophic microorganisms are crucial for mineralising leaf litter and rendering it more palatable to leaf-shredding invertebrates. A substantial part of leaf litter entering running waters may be buried in the streambed and thus be exposed to the constraining conditions prevailing in the hyporheic zone. The fate of this buried organic matter and particularly the role of microbial conditioning in this habitat remain largely unexplored. 2. The aim of this study was to determine how the location of leaf litter within the streambed , as well as the leaf litter burial history, may affect the leaf-associated aquatic hyphomycete communities and therefore leaf consumption by invertebrate detritivores. We tested the hypotheses that burial of leaf litter would result in lower decomposition rates associated with changes in microbial assemblages compared with leaf litter at the surface and altered microbial conditioning of buried leaf litter would lead to decreased quality and palatability to their consumers, translating into lower growth rates of detritivores. 3. These hypotheses were tested experimentally in a second-order stream where leaf-associated microbial communities, as well as leaf litter decomposition rates, elemental composition and toughness, were compared across controlled treatments differing by their location within the streambed. We examined the effects of the diverse conditioning treatments on decaying leaf palatability to consumers through feeding trials on three shredder taxa including a freshwater amphipod, of which we also determined the growth rate. 4. Microbial leaf litter decomposition, fungal biomass and sporulation rates were reduced when leaf litter was buried in the hyporheic zone. While the total species richness of fungal assemblages was similar among treatments, the composition of fungal assemblages was affected by leaf litter burial in sediment. 5. Leaf litter burial markedly affected the food quality of leaf material, probably due to the changes in microbial conditioning. Leaf litter palatability to shredders was highest for leaves exposed at the sediment surface and tended to be negatively related to leaf litter toughness and CP ratio. In addition, burial of leaf litter led to lower amphipod growth rates, which were positively correlated with leaf litter P content. 6. These results emphasise the importance of leaf colonisation by aquatic fungi in the hyporheic zone of headwater streams, where fungal conditioning of leaf litter appears particularly critical for nutrient and energy transfer to higher trophic levels.
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