Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The easternmost part of the Neoproterozoic Araçuaí belt comprises an anatectic domain that involves anatexites (the Carlos Chagas unit), leucogranites and migmatitic granulites that display a well-developed fabric. Microstructural observations support that the deformation occurred in the magmatic to submagmatic state. Structural mapping integrating field and anisotropy of magnetic susceptibility (AMS) revealed a complex, 3D structure. The northern domain displays gently dipping foliations bearing a NW-trending lineation, southward, the lineation trend progressively rotates to EW then SW and the foliation is gently folded. The eastern domain displays E-W and NE-SW trending foliations with moderate to steeply dips bearing a dominantly NS trending lineation. Magnetic mineralogy investigation suggests biotite as the main carrier of the magnetic susceptibility in the anatexites and ferromagnetic minerals in the granulites. Crystallographic preferred orientation (CPO) measurements using the electron backscatter diffraction (EBSD) technique suggest that the magnetic fabric comes from the crystalline anisotropy of biotite and feldspar grains, especially. The delineation of several structural domains with contrasted flow fabric suggests a 3D flow field involving westward thrusting orthogonal to the belt, northwestward orogen-oblique escape tectonics and NS orogen-parallel flow. This complex deformation pattern may be due to interplay of collision-driven and gravity-driven deformations.
ISSN: 0191-8141

hal-00903878
https://hal.archives-ouvertes.fr/hal-00903878
DOI : 10.1016/j.jsg.2013.08.001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Espinho Branco anatexite, located within a transcurrent, high-temperature shear zone in NE Brazil, was the subject of a comprehensive petrostructural study (Anisotropy of Magnetic Susceptibility - AMS, Anisotropy of Anhysteretic Remanence - AAR, Electron Backscatter Diffraction - EBSD) to evaluate the compatibility of different fabrics with the kinematics of melt deformation. Magnetite dominates susceptibilities larger than 1 mSI and biotite displays [001] lattice directions consistent with AMS k3 axes. In contrast, migmatites with a susceptibility lower than 0.5 mSI and no visible mesoscopic foliation provide crystallographic fabrics distinct from AMS and AAR. However, AAR remains consistent with the regional strain field. These results suggest that the correlation of field, AMS and crystallographic fabrics is not always straightforward despite the relatively simple organisation of the magnetic fabric in the anatexite. We conclude that AMS recorded the final stages of the strain field in the migmatite irrespective of its complex mesoscale structures and contrasting crystallographic fabrics.
ISSN: 0191-8141

hal-00823056
https://hal.archives-ouvertes.fr/hal-00823056
DOI : 10.1016/j.jsg.2012.12.008

Éditeur(s) : NRC
Résumé : We studied relationships between tropical tunas (albacore (Thunnus alalunga), bigeye (Thunnus obesus), and yellowfin (Thunnus albacares)) and their biotic and abiotic environments through simultaneous acoustic observations of tunas and their prey, experimental longline catch, and oceanographic data in French Polynesia. Vertical habitat limits were estimated based on temperature and dissolved oxygen at capture data. We then studied tuna-micronekton relationships to better understand how tuna occupy the pelagic space, At a regional scale, tunas were more abundant in areas rich in prey with favourable hydrological conditions. Inside such areas, at the scale of a longline set, however, the longline catches were maximal only when prey were not distributed in dense patches (except for yellowfin tuna). We interpreted this result by considering that areas with high prey abundance attract tunas, but at a small scale, if prey are patchy distributed, tunas are more inclined to feed on them rather than on longline baits. The effect of patches on yellowfin tuna catch per unit effort (CPUE) does not appear likely because this species also feeds on the mixed layer, where patch density was very low. Not only hydrological characteristics, but also prey density and prey patch characteristics, should be taken into account for interpreting longline CPUE data.
Thunnus obesus, et thon à nageoires jaunes, Thunnus albacares) à leurs environnements biotique et abiotique. Pour ce faire, nous avons réalisé simultanément, en Polynésie Française, des observations acoustiques des thons et de leurs proies, des pêches à l'aide d'une palangre instrumentée et des mesures hydrologiques. Des limites d'habitat vertical des thons calculées sur la base de données de température et d'oxygène dissous sont proposées. Nous étudions ensuite les relations thons-micronecton afin de mieux comprendre la stratégie d'occupation de l'espace des thons. A une échelle régionale, les thons sont plus abondants dans des zones riches en proies avec des conditions hydrologiques favorables. Cependant, à l'intérieur de telles zones, les captures sont maximales lorsque les proies ne sont pas distribuées sous forme de patchs (sauf pour le thon à nageoires jaunes). Nous interprétons ces résultats en considérant que les zones de fortes abondances en proies attirent les thons mais, qu'à une échelle fine, si les proies sont distribuées sous la forme de patchs denses, les thons s'en nourrissent préférentiellement, au détriment des appâts de la palangre. Ces patchs ne semblent pas influencer les prises par unité d'effort (PUE) des thons à nageoires jaunes, probablement parce que cette espèce se nourrit également dans la couche homogène où la densité en patchs est très faible. Les caractéristiques hydrologiques, mais également la densité en proies et leur type de distribution, devraient donc être pris en compte pour l'interprétation des données de PUE.
Canadian journal of fisheries and aquatic sciences (0706-652X) (NRC), 2002-06 , Vol. 59 , N. 6 , P. 1002-1013

Droits : 2002 NRC Canada
http://archimer.ifremer.fr/doc/2002/publication-733.pdf
DOI:10.1139/F02-073
http://archimer.ifremer.fr/doc/00000/733/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The crust of the Paleoproterozoic West African Craton in northern Ghana is dominantly made of Tonalite-Trondhjemite-Granodiorite (TTG) suites, low-K to high-K calc-alkaline granites, with minor LILE-enriched diorites, and chemically related lavas. Results of zircon U-Pb dating indicate that all these different rock types were formed together over a prolonged period of ca. 100 Ma, between 2.21 and 2.11 Ga. Zircon Hf isotope compositions of five samples are supra-chondritic (εHft from +1 to +6) indicating that the granitoids derive from the reworking of juvenile crustal components as old as 2.60 Ga. Geochemical data show that the TTGs were derived from the reworking of a low-K mafic crust, while biotite granites formed by the reworking of older felsic crustal rocks, and diorites derived from the melting of LILE-enriched mantle sources.The combined datasets support a three-step model for the formation of the crust of the West African craton in northern Ghana: (1) a juvenile, mafic proto-crust was extracted from the depleted mantle between 2.60 and 2.30 Ga, in an oceanic environment remote from any pre-existing continental nucleus; (2) the mafic proto-crust was reworked in several primitive magmatic arcs or in accreted oceanic plateaux. Crustal reworking initially produced minor felsic magmatism between 2.35 and 2.21 Ga, followed by the 2.21–2.15 Ga emplacement of low- to medium-P TTG and K-rich calc-alkaline granitoid suites, and was coeval with the formation of an enriched mantle source. (3) Various proto-continental terranes collided during the Eburnean orogeny between 2.14 and 2.11 Ga, triggering intense reworking of the composite crust and mantle reservoirs formed in the previous two steps, i.e. remnants of the juvenile mafic crust, older TTGs and biotite granites, and previously enriched mantle sources. The emplacement of high-P TTGs, granites and LILE-enriched diorites resulted from lower crustal heating in response to the delamination of the lower crust and lithospheric mantle. The Eburnean collision therefore marks the final stages of a 200–500 Ma long period of juvenile continental crust formation and stabilisation. The datasets further reveal that the Paleoproterozoic West African Craton comprises a minimum of two distinct crustal blocks, with north-western Ghana lying at their interface.
ISSN: 0301-9268

hal-01467999
https://hal.archives-ouvertes.fr/hal-01467999
DOI : 10.1016/j.precamres.2016.10.011

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Human exposure to dechloranes has been evaluated in Western Europe (France) with the analysis of Dechlorane Plus (DP), Dechloranes (Dec) 602, 603 and 604, Chlordene Plus (CP) and Mirex in 48 serum samples collected between 2003 and 2005. While no production source has been identified in Europe until now, detection frequencies for all investigated dechloranes were high, except for Dec 604 which was below detection limit for all samples. The mean DP concentration was 1.40±1.40ng/g lipid weight (lw), lower than levels reported in serum from Chinese population, but higher than levels reported in Canadian human milk. To the best of our knowledge, this is the first time that ∑5dechlorane levels are reported for human serum. A specific pattern of contamination was found (Dec 603>DP>Mirex>Dec 602>CP) compared to other biota samples that have been analyzed from Europe, with Dec 603 as the most abundant dechlorane (mean level: 2.61±2.63ng/g lw). Dec 603 and CP levels were correlated with age and with levels of some bioaccumulative organochlorine pesticides (OCPs). These results indicate that bioaccumulation properties should be further investigated and taken in consideration when assessing human exposure to dechloranes. For comparison purposes, polybrominated diphenyl ether (PBDE) levels were also measured for BDE-47, -99, -100, -153 and -154 in the serum samples. As expected, BDE-47 and BDE-153 were the major congeners with mean levels of 2.06±1.80ng/g lw and 1.39±0.97ng/g lw, respectively. The mean ∑5PBDE levels (4.32±2.99ng/g lw) were in the range typical of Western Europe levels, but lower than the mean ∑5dechlorane levels (6.24±4.16ng/g lw). These results indicate that the attention to dechloranes should be continued if research indicates toxicological concerns.
ISSN: 0160-4120

hal-01004642
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01004642
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01004642/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01004642/file/Levelssur dechloranes_and_polybrominated_diphenyl_ethers_accepted.pdf
DOI : 10.1016/j.envint.2013.12.014

Éditeur(s) : Gauthier-Villars
Résumé : This review provides a brief update of the occurrence and adaptive significance of asexual reproduction in echinoderms. It then focuses on the state of knowledge of biotic and abiotic factors that influence asexual processes in this group, particularly factors that may play a role in regulating the expression and relative proportion of asexual versus sexual phenotypes within populations of species, as well as factors modulating and triggering asexual processes. The information presented in the review is synthesized into the form of a basic model depicting how environmental factors may interact with physiological factors to regulate asexual reproduction in echinoderms, and to show how such regulatory processes may parallel in some ways those known to regulate sexual reproduction. Since the model is based mainly on correlational evidence derived from comparative field observations, a number of experimental approaches for testing the predictions of the model are discussed briefly.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1996 , Vol. 19 , N. 3-4 , P. 227-235

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00094/20481/18151.pdf
http://archimer.ifremer.fr/doc/00094/20481/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : The area of forest plantations is increasing worldwide helping to meet timber demand and protect natural forests. However, with global change, monospecific plantations are increasingly vulnerable to abiotic and biotic disturbances. As an adaption measure we need to move to plantations that are more diverse in genotypes, species, and structure, with a design underpinned by science. TreeDivNet, a global network of tree diversity experiments, responds to this need by assessing the advantages and disadvantages of mixed species plantations. The network currently consists of 18 experiments, distributed over 36 sites and five ecoregions. With plantations 1-15 years old, TreeDivNet can already provide relevant data for forest policy and management. In this paper, we highlight some early results on the carbon sequestration and pest resistance potential of more diverse plantations. Finally, suggestions are made for new, innovative experiments in understudied regions to complement the existing network.
ISSN: 0044-7447

hal-01204232
https://hal.archives-ouvertes.fr/hal-01204232
DOI : 10.1007/s13280-015-0685-1
PRODINRA : 324368
PUBMED : 26264716

Éditeur(s) : HAL CCSD Elsevier
Résumé : In Vietnam, recent studies demonstrated that the Kon Tum Massif was part of the Indosinian mountain system, together with the Truong Son Belt. One sector of the Kon Tum Massif (Song Ba valley) is a granulite facies terrain for which Ar–Ar and U–Pb ages cluster around 245–250 Ma. In the area of Song Bien river, also metamorphosed under granulite facies conditions, Ar–Ar ages of 410 Ma are displayed by biotite. In this study, U–Pb dating of monazite and zircon has been used to understand the reason for these two groups of ages, taking into account the metamorphic mineral assemblages related to granulite facies metamorphism in the two districts. For granulites of Song Ba valley, ages of 245–250 Ma are confirmed from monazites. In the Song Bien district, ages of 465–470 Ma displayed by monazites are interpreted to correspond to the metamorphic climax. Zircons from one of these samples record the age of anatexis that has affected the granulitic rocks. The younger age recorded in the Song Ba valley is considered to reflect high temperature related to charnockitic intrusions emplaced near the end of the Indosinian orogeny, overprinting the earlier formed granulites and resetting the U–Pb and Ar–Ar ages. For the first time, two HT events are dated in the Kon Tum Massif, one occurring during the Ordovician and the other during the Permo-Triassic.
ISSN: 0743-9547

hal-00404975
https://hal.archives-ouvertes.fr/hal-00404975
DOI : 10.1016/j.jseaes.2007.01.005

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : Quantitative analyses on calcareous nannofossil assemblages on high temporal resolution (600-800 years) have been carried out from Core KC01B in the Ionian Sea (Eastern Mediterranean) throughout Marine Isotope Stage (MIS) 13-9, between 500 and 300 ka. This is an interval of considerable climate changes, known as the Mid-Brunhes event, which includes MIS 11, considered as a possible analogue for future interglacial conditions. In the Mediterranean core, the interval is characterized by the dominance of Gephyrocapsa spp., as also known from ocean records. Calcareous nannofossil abundance fluctuations have been interpreted in terms of modification of sea surface primary productivity/water stratification and temperature. Specifically, the increase in abundance of Gephyrocapsa caribbeanica and small Gephyrocapsa coupled with decreases of Florisphaera profunda, Syracosphaera spp. and Rhabdosphaera spp. suggests enhanced primary productivity/mixed surface waters during interglacial stages and at the Terminations, which can be interpreted in terms of interaction between climate changes and mesoscale oceanographic circulation. On the other hand, distributions of Calciosolenia spp., Oolithotus spp. and Umbilicosphaera sibogae, which are in phase with delta O-18 curve showing higher abundances at the lighter values of the marine isotope record, are considered as warm-water indicators. Biotic proxies point to peculiar climate dynamics through the MIS 12-11 transition (i.e. Termination V). High productive, cool, low salinity and turbid surface waters characterize the early MIS 11(421-408 ka) and likely reflect enhanced continental humidity/monsoon activity over North Africa and increased runoff into the basin. A late surface water warming with respect to Termination V is established at about 403 ka, during a period of low insolation forcing, almost coeval with the deposition of sapropel S11. A climate optimum, lasting about 15 ky (403-389 ka), is then recorded during a period of low insolation forcing centred at 398 ka. The later part of MIS 11 is characterized by climate deterioration at about 389 ka. Comparison with results from subtropical to polar Atlantic records suggests a remarkable relation between Mediterranean and Atlantic climate regimes.
Quaternary International (1040-6182) (Pergamon-elsevier Science Ltd), 2013-03 , Vol. 288 , P. 97-111

Droits : 2011 Elsevier Ltd and INQUA. All rights reserved.
http://archimer.ifremer.fr/doc/00181/29194/27593.pdf
DOI:10.1016/j.quaint.2011.12.007
http://archimer.ifremer.fr/doc/00181/29194/

Éditeur(s) : HAL CCSD
Résumé : International audience
The Kazdağ Massif exposes a metamorphic dome in the Biga Peninsula of northwest Turkey. An extensional origin has been proposed for the dome, limited on both flanks by detachments and/or shear zones. The northern flank is bounded by the extensional Alakeçi Shear Zone (ASZ), whose P-T-t path is still poorly known. We therefore focus on its metamorphic conditions and related temporal history to precise its tectono-metamorphic evolution. The local tectonostratigraphy in structurally ascending order comprises: (i) the high-grade metamorphic core rocks of the Kazdaǧ Massif (gneisses and micaschists intercalated with amphibolites and marbles); (ii) the two kilometer-thick ASZ; (iii) the overlaying unmetamorphosed pre-Cenomanian accretionary Çetmi mélange; and (iv) Neogene sedimentary and volcanic cover rocks. ASZ mylonites were derived from both the core rocks and the mélange lithologies. From the north to the south the mylonitic fabrics in the ASZ depict a top-to-the N-NNE shearing, parallel to the NNE-plunging stretching lineation and NNW-dipping mylonitic foliation. This geometry implies normal sense movement i.e. north-side down-dip extensional displacement along this flank of the Kazdaǧ Massif. The northward transition from ductile to brittle-ductile regime through the ASZ shows that the deformation occurred at decreasing temperatures and degree of metamorphism. The paragenesis in equilibrium within the mylonitic gneisses and schists contains Qtz + Fs + Ms + Bt + Grt ± St ± Sill, with late retrogressive chlorite after biotite and garnet. Four samples of ASZ rocks yielded pressures between 6.9-5.7 kbar and temperatures between 706-587°C. Three samples from the mylonitic rocks supplied in situ isochron 36Ar/40Ar mica ages between 31.2-24.2 Ma, which we interpret to date the cooling of the mylonites following the P-T decrease across the ASZ. The metamorphic and structural results support the extensional character of the ASZ, and sketch transition from sillimanite core gneisses in the deeper structural levels to chlorite schists towards the top of the shear zone. These new data allow to precise the peak P-T conditions and the temporal evolution in the northern flank of the Kazdaǧ Massif, where Late Oligocene extensional exhumation was assisted by NNE-directed ductile-brittle ASZ, which had operated from amphibolite to greenschist facies. At the regional scale, this tectono-metamorphic pattern is similar to those observed on other places of the north Aegean domain.
IOP Conference Series
Austin, TE, United States

hal-00642725
https://hal-brgm.archives-ouvertes.fr/hal-00642725
DOI : 10.1088/1755-1307/2/1/012012

Éditeur(s) : John Wiley & Sons
Résumé : 1. Transitional waters, described as critical transition zones because of their position at terrestrial, freshwater and marine interfaces, provide essential goods and services to the biosphere including human populations. These ecotones face increasing human influence mainly due to population density increase in coastal areas. 2. Transitional water bodies have, to date, received little attention in the development of ecological status indicators, this is a critical deficiency when trying to meet the Water Framework Directive objective of all significant water bodies achieving good ecological status by the year 2015. 3. In order to assess changes in transitional water communities many taxonomic-based indicators have already been proposed but there are a number of concerns for their use such as taxonomic classification difficulties, their unsuitability for multi-site comparisons and their inconsistent relationships with disturbance or stress. 4. Alternative methods based on body size, abundance distribution among functional groups, functional diversity and productivity descriptors are proposed. These methods offer the opportunity to compare sites with different taxonomic compositions and allow derivation of indicators related to ecological status of communities under scrutiny. 5. Finally, the suitability of these taxonomic-free descriptors to provide relevant information for each of the four main biotic compartments in coastal lagoons is discussed. The use of biomass distribution among functional groups for fish, benthos and macrophyte and to use body-size distribution for benthos and plankton is proposed. Copyright (c) 2006 John Wiley and Sons, Ltd.
Aquatic Conservation: Marine and Freshwater Ecosystems (1052-7613) (John Wiley & Sons), 2006-07 , Vol. 16 , N. 5 , P. 469-482

Droits : 2006 John Wiley & Sons, Ltd
http://archimer.ifremer.fr/doc/2006/publication-1849.pdf
DOI:10.1002/aqc.769
http://archimer.ifremer.fr/doc/00000/1849/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : We examined tree-soil habitat associations in lowland forest communities at Paracou, French Guiana. We analyzed a large dataset assembling six permanent plots totaling 37.5 ha, in which extensive LIDAR-derived topographical data and soil chemical and physical data have been integrated with precise botanical determinations. Map of relative elevation from the nearest stream summarized both soil fertility and hydromorphic characteristics, with seasonally inundated bottomlands having higher soil phosphate content and base saturation, and plateaus having higher soil carbon, nitrogen and aluminum contents. We employed a statistical test of correlations between tree species density and environmental maps, by generating Monte Carlo simulations of random raster images that preserve autocorrelation of the original maps. Nearly three fourths of the 94 taxa with at least one stem per ha showed a significant correlation between tree density and relative elevation, revealing contrasted species-habitat associations in term of abundance, with seasonally inundated bottomlands (24.5% of species) and well-drained plateaus (48.9% of species). We also observed species preferences for environments with or without steep slopes (13.8% and 10.6%, respectively). We observed that closely-related species were frequently associated with different soil habitats in this region (70% of the 14 genera with congeneric species that have a significant association test) suggesting species-habitat associations have arisen multiple times in this tree community. We also tested if species with similar habitat preferences shared functional strategies. We found that seasonally inundated forest specialists tended to have smaller stature (maximum diameter) than species found on plateaus. Our results underline the importance of tree-soil habitat associations in structuring diverse communities at fine spatial scales and suggest that additional studies are needed to disentangle community assembly mechanisms related to dispersal limitation, biotic interactions and environmental filtering from species-habitat associations. Moreover, they provide a framework to generalize across tropical forest sites.
ISSN: 1932-6203

hal-01260289
https://hal.archives-ouvertes.fr/hal-01260289
PRODINRA : 342930
DOI : 10.1371/journal.pone.0141488

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : Fishing with a beach seine for catching small pelagic fishes is a traditional activity in Martinique. Since the early eighties, an important decrease in the number of fishermen practising this activity has been recorded. In the context of high exploitation of reef resources, the beach seine presents a low selectivity, catching too many juveniles of demersal fish. The fads established in coastal areas, have been successfully used in others regions of the world for exploiting small pelagics. Thus, it could allow to favour a change of exploitation style of these resources in Martinique. In partnership, Ifremer, the Regional Council and the Fishing Committee have began an evaluation of the potentialities for this type of structures around the island. To achieve this study, several experimental coastal fads have been established in different places. Surveys by subaquatic observations are periodically carried out to compare the attractive power of different aggregation devices (colour, shape, volume) and understand the factors influencing the determinism of the aggregation (biotic and abiotic). The results presented and discussed correspond to the initial stage of this study which should be pursued in the next months.Original Abstract: La peche a la senne de plage pour la capture des petits poissons pelagiques est une activite halieutique traditionnelle et ancienne en Martinique. Depuis le debut des annees quatre-vingt, une diminution importante du nombre de pecheurs pratiquant cette activite est enregistree. Les dispositifs de concentration de poissons (DCP) implantes en zone cotiere sont abondamment utilises dans d'autres regions du monde avec succes. Ils pourraient donc permettre de redynamiser ce secteur en Martinique. L'Ifremer, le conseil regional et le comite des peches ont entrepris, en partenariat, une etude permettant d'evaluer les potentialites du developpement de ce type d'amenagement autour de l'ile. Pour realiser cette etude, plusieurs DCP cotiers experimentaux ont ete implantes dans differents sites. Ils font l'objet d'un suivi halieutique base sur les comparaisons des captures realisees par les professionnels sur et hors DCP. En parallele, des campagnes d'observations sous-marines sont effectuees de facon periodique. Elles permettent d'une part de comparer les pouvoirs attractifs de differents dispositifs d'agregation (forme, volume, couleur) et, d'autre part, de mieux comprendre les facteurs biotiques et abiotiques influencant le determinisme de l'agregation. Les resultats presentes et discutes correspondent a la phase initiale de l'etude qui doit se poursuivre dans les prochains mois afin de couvrir toute la saison de peche.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15302/12634.pdf
http://archimer.ifremer.fr/doc/00042/15302/

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : The Amazon basin harbors a diverse ecological community that has a critical role in the maintenance of the biosphere. Although plant and animal communities have received much attention, basic information is lacking for fungal or prokaryotic communities. This is despite the fact that recent ecological studies have suggested a prominent role for interactions with soil fungi in structuring the diversity and abundance of tropical rainforest trees. In this study, we characterize soil fungal communities across three major tropical forest types in the western Amazon basin (terra firme, seasonally flooded and white sand) using 454 pyrosequencing. Using these data, we examine the relationship between fungal diversity and tree species richness, and between fungal community composition and tree species composition, soil environment and spatial proximity. We find that the fungal community in these ecosystems is diverse, with high degrees of spatial variability related to forest type. We also find strong correlations between alpha- and beta-diversity of soil fungi and trees. Both fungal and plant community beta-diversity were also correlated with differences in environmental conditions. The correlation between plant and fungal richness was stronger in fungal lineages known for biotrophic strategies (for example, pathogens, mycorrhizas) compared with a lineage known primarily for saprotrophy (yeasts), suggesting that this coupling is, at least in part, due to direct plant-fungal interactions. These data provide a much-needed look at an understudied dimension of the biota in an important ecosystem and supports the hypothesis that fungal communities are involved in the regulation of tropical tree diversity.
ISSN: 1751-7362

hal-01032405
https://hal.archives-ouvertes.fr/hal-01032405
DOI : 10.1038/ismej.2013.66

Éditeur(s) : HAL CCSD Wiley
Résumé : Tank bromeliads form a conspicuous, yet neglected freshwater habitat in Neotropical forests. Recent studies driven by interests in medical entomology, fundamental aspects of bromeliad ecology and experimental research on food webs have, however, prompted increasing interest in bromeliad aquatic ecosystems. As yet, there is nothing in the literature about the life histories and environmental drivers of invertebrate population dynamics in tank bromeliads. Based on fortnightly samples taken over oneyear, size frequency plots and individual dry masses allowed us to establish the life cycles and growth rates of the dominant aquatic invertebrates in a common bromeliad species of French Guiana. Linear mixed-effect models and Mantel tests were used to predict changes in density, biomass, and growth rates in relation to temperature, rainfall, humidity and detrital resources. Annual variations in invertebrate densities and biomasses could be described according to three types of distribution: unimodal, bimodal or almost constant. Despite seasonal variations, precipitation, temperature, relative humidity and detritus concentration accounted significantly for changes in density and biomass, but we found no significant responses in growth rates of most invertebrate species. Species rather displayed non-seasonal life cycles with overlapping cohorts throughout the year. There was also a trend for delayed abundance peaks among congeneric species sharing similar functional traits, suggesting temporal partitioning of available resources. Beyond novel knowledge, quantitative information on life histories is important to predict food-web dynamics under the influence of external forcing and self-organisation. Our results suggest that changes in species distribution that will affect population dynamics through biotic interactions in space and/or time could have greater effects on food webs and ecosystem functioning than changes in environmental factors per se.
ISSN: 0046-5070

hal-01607779
https://hal.archives-ouvertes.fr/hal-01607779
DOI : 10.1111/fwb.12862
PRODINRA : 407311

Éditeur(s) : HAL CCSD Geological Society
Résumé : International audience
We constrain the slip and cooling history of the Mykonos detachment footwall using thermochronometry. A U-Pb zircon age of 13.5 +/- 0.3 Ma dates intrusion of the Mykonos monzogranite. Ar-40/ Ar-39 homblende and biotite ages from the monzogranite are 12.7 +/- 0.6 Ma and 10.9 +/- 0.6 Ma, whereas zircon and apatite fission-track ages range from 13 +/- 0.8 Ma to 10.7 +/- 0.8 Ma and 12.5 +/- 2.2 Ma to 10.5 +/- 1.8 Ma. (U-Th)/He ages range from 13.6 +/- 0.6 Ma to 9.0 +/- 0.7 Ma for zircon and 11. +/- 10.5 Ma to 8.9 +/- 0.4 Ma for apatite. The ages in part overlap within 2 sigma errors and together with the long apatite fission-track lengths (>14 mu m) support rapid cooling at rates > 100 degrees C Ma(-1). The low-temperature thermochronometric ages decrease east-northeastwards in the direction of hanging-wall transport on the Mykonos detachment. Age-distance relationships show that the Mykonos detachment slipped at an average rate of 6.0 + 9.2/-2.4 km Ma(-1) c. 30 km of offset and c. 12 km of exhumation. This result indicates that Miocene low-angle normal faulting was not important for the exhumation of the Cycladic blueschist unit. The opening of the Aegean Sea basin in the Miocene was controlled by a few large-magnitude low-angle normal faults.
ISSN: 0016-7649

hal-00412177
https://hal.archives-ouvertes.fr/hal-00412177
DOI : 10.1144/0016-76492006-145

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
The Western Indian Ocean harbors one of theworld’s most diverse marine biota yet is threatened byexploitation with few conservation measures in place.Primary candidates for conservation in the region are theScattered Islands (Iles Eparses), a group of relativelypristine and uninhabited islands in the MozambiqueChannel. However, while optimal conservation strategiesdepend on the degree of population connectivity amongspatially isolated habitats, very few studies have beenconducted in the area. Here, we use highly variablemicrosatellite markers from two damselfishes (Amphiprionakallopisos and Dascyllus trimaculatus) with differing lifehistory traits [pelagic larval duration (PLD), adult habitat]to compare genetic structure and connectivity among theseislands using classic population structure indices as well asBayesian clustering methods. All classical fixation indexesFST, RST, G0ST, and Jost’s D show stronger genetic differentiationamong islands for A. akallopisos compared to D.trimaculatus, consistent with the former species’ shorterPLD and stronger adult site attachment, which may restrictlarval dispersal potential. In agreement with these results,the Bayesian analysis revealed clear genetic differentiationamong the islands in A. akallopisos, separating the southerngroup (Bassas da India and Europa) from the center(Juan de Nova) and northern (Iles Glorieuses) islands, butnot for D. trimaculatus. Local oceanographic patterns suchas eddies that occur along the Mozambique Channel appearto parallel the results reported for A. akallopisos, but suchfeatures seem to have little effect on the genetic differentiationof D. trimaculatus. The contrasting patterns ofgenetic differentiation between species within the samefamily highlight the importance of accounting for diverselife history traits when assessing community-wide connectivity,an increasingly common consideration in conservationplanning.
ISSN: 0722-4028

hal-01561992
https://hal-univ-perp.archives-ouvertes.fr/hal-01561992
DOI : 10.1007/s00338-016-1495-z

Éditeur(s) : HAL CCSD Wiley Open Access
Résumé : 11 pages
International audience
The loss of regulating agents such as parasites is among the most important changes in biotic interactions experienced by populations established in newly colonized areas. Under a relaxed parasite pressure, individuals investing less in costly immune mechanisms might experience a selective advantage and become successful colonizers as they re-allocate resources to other fitness-related traits. Accordingly, a refinement of the evolution of increased competitive ability (EICA) hypothesis proposed that immunity of invasive populations has evolved toward a reduced investment in innate immunity, the most costly component of immunity, and an increased humoral immunity that is less costly. Biogeographical approaches comparing populations between native and expansion ranges are particularly relevant in exploring this issue, but remain very scarce. We conducted a biogeographical comparison between populations of Spectacled Thrush (Turdus nudigenis) from the native area (South America) and from the expansion range (Caribbean islands). First, we compared haemosporidian prevalence and circulating haptoglobin (an acute-phase protein produced during inflammation). Second, we challenged captive birds from both ranges with Escherichia coli lipopolysaccharides (LPS) and measured postchallenge haptoglobin production and body mass change. Birds from the expansion range showed lower haemosporidian prevalence and lower levels of haptoglobin than birds from the native range. In addition, the inflammation elicited by LPS injection and its associated cost in terms of body mass loss were lower in birds from the expansion range than in birds from the native range. In accordance with the enemy release hypothesis, our results suggest that range expansion is associated with a reduced infection risk. Our study also supports the hypothesis that individuals from newly established populations have evolved mechanisms to dampen the inflammatory response and are in accordance with one prediction of the refined EICA hypothesis, proposed to understand biological invasions.
ISSN: 2045-7758

hal-01403291
https://hal.archives-ouvertes.fr/hal-01403291
DOI : 10.1002/ece3.2486

Éditeur(s) : HAL CCSD
Résumé : Tropical forests are a biodiversity hotspot, with the coexistence of numerous species until a fine spatial scale. Particularly, 16.000 tree species coexist in Amazonia, 1.800 in Frenche Guiana and between 120 and more than 200 tree species per hectare. However, there are some uncertainties in maintaining diversity in regard to global changes. Hence before predicting the diversity evolution face of global changes, fundamental studies are needed to understand which assembly processes are involved in the maintenance of diversity. These fundamental studies still relevant given the lack of consensus on the relative importance of assembly processes. This thesis is a continuation of these fundamental studies, using innovative integrative approach, at multi-scale, to address three types of diversity: taxonomic diversity, functional and phylogenetic. Our results challenge the importance of environmental filtering for hydrological and chemical properties of soils, versus the importance of biotic interactions on community assembly. Furthermore, our results suggest that species distributions could be affected by forest dynamics related to falling trees and therefore by light availability. Finally, we have highlighted the importance of dispersal limitation on community assembly.
Les forêts tropicales représentent un ‘hotspot’ de diversité avec un nombre considérable d’espèces qui coexistent jusqu’à une échelle locale fine. Plus particulièrement, 16 000 espèces d’arbres coexistent en Amazonie, 1 800 en Guyane française et entre 120 et plus de 200 espèces d’arbres par hectare. Cependant, le maintien de cette diversité face aux changements globaux actuels et à venir (qu’ils soient anthropiques ou climatiques…) est incertain. Avant de pouvoir prédire l’évolution de la diversité face aux changements globaux, un travail fondamental est nécessaire afin de comprendre les processus d’assemblage des communautés, processus qui maintiennent cette diversité. Ce travail est réalisé depuis de nombreuses années en écologie et reste d’actualité vu l’absence de consensus quant à l’importance relative des processus d’assemblage. Cette thèse s’inscrit dans la continuité de ce travail fondamental en utilisant une approche intégrative innovante, qui aborde de manière multi-échelle trois types de diversité : diversité taxonomique, fonctionnelle et phylogénétique. Nos résultats questionnent sur l'importance du filtrage environnemental quant aux propriétés hydrologiques et chimiques des sols, et sur celle des interactions biotiques dans l’assemblage de la communauté étudiée. Par ailleurs, nos résultats suggèrent que les distributions d’espèces puissent être influencées par la dynamique forestière en lien avec les chutes d’arbres et donc avec la disponibilité en lumière. Enfin, nous avons mis en évidence l’importance de la limitation de dispersion.
https://tel.archives-ouvertes.fr/tel-01418447

NNT : 2016YANE0003
tel-01418447
https://tel.archives-ouvertes.fr/tel-01418447
https://tel.archives-ouvertes.fr/tel-01418447/document
https://tel.archives-ouvertes.fr/tel-01418447/file/these.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The timing of E–W extension of the Tibetan plateau provides a test of mechanical models of the geodynamic evolution of the India–Asia convergence zone. In this work we focus on the Kung Co half graben (Southern Tibet, China), bounded by an active N–S normal fault with a minimum vertical offset of 1600 m. To estimate the onset of normal faulting we combined high and medium temperature (U–Pb, Ar/Ar) and low temperature ((U–Th)/He) thermochronometry of the Kung Co pluton, a two-mica granite of the northern Himalayan granitic belt that outcrop in the footwall of the fault. Biotite and muscovite Ar/Ar ages , are close from each other [not, vert, similar 16 Ma ± 0.2 (Ms) and not, vert, similar 15 ± 0.4 Ma (Bt)], which is typical of fast cooling. The zircon and apatite (U–Th)/He ages range from 11.3 to 9.6 Ma and 9.9 to 3.7 Ma respectively. These He ages are indicative of (1) fast initial cooling, from 11.3 to not, vert, similar 9 Ma, gradually decreasing with time and (2) a high geothermal gradient (not, vert, similar 400 °C/km), close to the surface at not, vert, similar 10 Ma. The Kung Co pluton was emplaced at about 22 Ma (U–Pb on zircon) at less than 10 km depth and 520–545 °C. Subsequent to its shallow emplacement, the pluton underwent fast thermal re-equilibration ending around 7.5 Ma, followed by a period of slow cooling caused either by the end of the thermal re-equilibration or by very slow exhumation (0.02–0.03 mm/yr) from not, vert, similar 7.5 Ma to at least 4 Ma. In either case the data suggest that the exhumation rate increased after 4 Ma. We infer this increase to be related to the initiation of the Kung Co normal fault. A critical examination of previously published data show that most not, vert, similar N–S Tibetan normal faults may have formed less than 5 Ma ago rather than in the Miocene as assumed by several authors. Such a young age implies that E–W extension is not related to the Neogene South Tibetan magmatism (25 to 8 Ma). Consequently, models relating E–W extension to magmatism, such as convective removal of the lower lithosphere, may be inappropriate. We rather think that this extension is related with local accommodation of boundary forces and displacements.
ISSN: 0012-821X

hal-00311791
https://hal.archives-ouvertes.fr/hal-00311791
DOI : 10.1016/j.epsl.2007.01.029