39 research outputs found

    Optical control of scattering, absorption and lineshape in nanoparticles

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    We find exact conditions for the enhancement or suppression of internal and/or scattered fields in any smooth particle and the determination of their spatial distribution or angular momentum through the combination of simple fields. The incident fields can be generated by a single monochromatic or broad band light source, or by several sources, which may also be impurities embedded in the nanoparticle. We can design the lineshape of a particle introducing very narrow features in its spectral response

    Infections in Infants during the First 12 Months of Life: Role of Placental Malaria and Environmental Factors

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    Background: The association between placental malaria (PM) and first peripheral parasitaemias in early infancy was assessed in Tori Bossito, a rural area of Benin with a careful attention on transmission factors at an individual level. Methodology: Statistical analysis was performed on 550 infants followed weekly from birth to 12 months. Malaria transmission was assessed by anopheles human landing catches every 6 weeks in 36 sampling houses and season defined by rainfall. Each child was located by GPS and assigned to the closest anopheles sampling house. Data were analysed by survival Cox models, stratified on the possession of insecticide-treated mosquito nets (ITNs) at enrolment. Principal Findings: Among infants sleeping in a house with an ITN, PM was found to be highly associated to first malaria infections, after adjusting on season, number of anopheles, antenatal care (ANC) visits and maternal severe anaemia. Infants born from a malaria infected placenta had a 2.13 fold increased risk to present a first malaria infection than those born from a non infected placenta ([1.24-3.67], p<0.01) when sleeping in a house with an ITN. The risk to present a first malaria infection was increased by 3.2 to 6.5, according to the level of anopheles exposure (moderate or high levels, compared to the absence of anopheles). Conclusions: First malaria infections in early childhood can be attributed simultaneously to both PM and high levels of exposure to infected anopheles. Protective measures as Intermittent Preventive Treatment during pregnancy (IPTp) and ITNs, targeted on both mothers and infants should be reinforced, as well as the research on new drugs and insecticides. In parallel, investigations on placental malaria have to be strengthened to better understand the mechanisms involved, and thus to protect adequately the infants high risk group

    The macro- and megabenthic fauna on the continental shelf of the eastern Amundsen Sea, Antarctica

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    In 2008 the BIOPEARL II expedition on board of RRS James Clark Ross sailed to the eastern Amundsen Sea Embayment and Pine Island Bay, one of the least studied Antarctic continental shelf regions due to its remoteness and ice cover. A total of 37 Agassiz trawls were deployed at depth transects along the continental and trough slopes. A total of 5,469 specimens, belonging to 32 higher taxonomic groups and more than 270 species, were collected. Species richness per station varied from 1–55. The benthic assemblages were dominated by echinoderms and clearly different to those in the Ross, Scotia and Weddell seas. Here we present the macro- and megafaunal assemblage structure, its species richness and the presence of several undescribed species

    Macroecology of Southern Ocean echinoids : distribution, biogeography and modelisation

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    Quels sont les grands patrons de distribution des espĂšces et quels sont les facteurs qui les contrĂŽlent? Ces questions sont au cƓur des problĂ©matiques macroĂ©cologiques et prennent un intĂ©rĂȘt tout particulier au regard du rĂ©chauffement climatique global actuel. L’objectif principal de ce travail de thĂšse Ă©tait de dĂ©terminer les patrons de distribution actuels des espĂšces d’oursins antarctiques et subantarctiques Ă  l’échelle de l’ocĂ©an Austral et de mettre en Ă©vidence les facteurs qui contrĂŽlent ces distributions. La modĂ©lisation des niches Ă©cologiques d’une vingtaine d’espĂšces d’oursins a permis de mettre en Ă©vidence deux grands patrons de distribution : (1) un premier reprĂ©sentĂ© par les espĂšces dont la distribution n’est pas limitĂ©e au sud du Front Polaire et s’étend des cĂŽtes antarctiques aux zones subantarctiques et tempĂ©rĂ©es froides et (2) un deuxiĂšme constituĂ© d’espĂšces restreintes Ă  la zone antarctique. Au sein de ces deux patrons, cinq sous-patrons ont Ă©galement pu ĂȘtre dĂ©fini sur la base de diffĂ©rences de distribution latitudinale et bathymĂ©trique entre groupes d’espĂšces. Cette approche biogĂ©ographique par modĂ©lisation de niche Ă©cologique a Ă©tĂ© complĂ©tĂ©e par l’analyse de similaritĂ© de l’ensemble des faunes d’oursins, de bivalves et de gastĂ©ropodes, au niveau spĂ©cifique et gĂ©nĂ©rique, entre biorĂ©gions de l’ocĂ©an Austral. Cette analyse dĂ©montre qu’il existe chez les oursins et les bivalves des connexions fauniques entre l’AmĂ©rique du Sud et les zones subantarctiques ainsi qu’une sĂ©paration entre l’Est et l’Ouest antarctique. Au contraire, les faunes de gastĂ©ropodes subantarctiques montrent des affinitĂ©s plutĂŽt antarctiques que sud-amĂ©ricaines, l’Antarctique ne formant qu’une unique province pour ce clade. Ces diffĂ©rences entre clades sont interprĂ©tĂ©es comme Ă©tant le rĂ©sultat d’histoires Ă©volutive et biogĂ©ographique distinctes entre oursins et bivalves d’une part et gastĂ©ropodes d’autre part. L’hypothĂšse d’une rĂ©ponse Ă©volutive diffĂ©rente des clades aux changements environnementaux survenus au cours du CĂ©nozoĂŻque est avancĂ©e. Enfin, l’existence de connexions fauniques trans-antarctiques est mise en Ă©vidence dans l’étude des trois clades ; celles-ci sont interprĂ©tĂ©es comme le rĂ©sultat de la dislocation de la calotte ouest-antarctique et l’ouverture de bras de mer trans-antarctiques au cours du PlĂ©istocĂšne. Parmi les paramĂštres environnementaux utilisĂ©s dans la modĂ©lisation des niches Ă©cologiques, les rĂ©sultats montrent que trois paramĂštres jouent un rĂŽle majeur dans la distribution des oursins : la profondeur, la couverture de glace et la tempĂ©rature des eaux de surface. Toutefois, l’importance relative de ces paramĂštres diffĂšre selon les espĂšces d’oursins Ă©tudiĂ©es. L’étude du genre Sterechinus souligne tout particuliĂšrement ces diffĂ©rences. En effet, l’espĂšce S. neumayeri est plus sensible aux conditions environnementales qui prĂ©dominent prĂšs des cĂŽtes antarctiques (tempĂ©rature des eaux de surface et couverture de glace), alors que S. antarcticus semble ĂȘtre beaucoup moins contraint par ces mĂȘmes paramĂštres. La distribution potentielle de S. antarcticus est d’ailleurs beaucoup plus Ă©tendue en latitude. Cependant, S. antarcticus n’est pas prĂ©sent sur l’ensemble de son aire de distribution potentielle, ceci pouvant ĂȘtre expliquĂ© alternativement par le rĂ©sultat (1) de facteurs ocĂ©anographiques (rĂŽle de barriĂšre biogĂ©ographique jouĂ© par le Front Polaire), (2) d’interactions biotiques (phĂ©nomĂšnes de compĂ©tition inter-spĂ©cifique) et (3) du contexte temporel (colonisation toujours en cours).What are the forcing factors and main patterns of species distribution? This question is the core of macroecological issues and is of particular interest in the present context of global warming. The main objectives of this thesis were to determine the current distribution patterns of Antarctic and sub-Antarctic echinoid species at the scale of the whole Southern Ocean and to highlight the forcing factors that control them. The ecological niche modelling of 19 echinoid species showed that distribution is mainly structured in two patterns: (1) a first one represented by species that are not limited to the south of the Polar Front and distributed from the Antarctic coasts to the sub-Antarctic and cold temperate areas, and (2) a second one with species restricted to the Antarctic area. Within these two main patterns, five sub-patterns were also identified that depend on differences in the latitudinal and depth range of species groupings. In addition to this approach of biogeography by ecological niche modelling, a similarity analysis of echinoid, bivalve and gastropod fauna between bioregions of the Southern Ocean was performed at species and genus levels. This analysis reveals faunal connections between southern South America and sub-Antarctic areas in echinoids and bivalves, along with a partition between the East and West Antarctic. On the contrary, sub-Antarctic gastropod fauna show Antarctic rather than South American affinities and the Antarctic form a sole and unique province in this clade. These differences between clades are interpreted as the result of distinct biogeographic and evolutionary histories between echinoids and bivalves on the one hand, and gastropods on the other hand. The proposed hypothesis is that clades developped different evolutionary responses to the environmental changes that occurred during the Cenozoic. Finally, in the three clades, trans-Antarctic faunal connections are shown and interpreted as a result of West Antarctic Ice Sheet collapses and the setting up of trans-Antarctic sea-ways during the Pleistocene. Among the environmental parameters used for the ecological niche modelling, results show that the three following parameters play the main part in echinoid distribution: depth, sea-ice cover and sea surface temperature. However, the relative importance of these parameters depends on the species under studies. These differences are particularly emphasized in the case study of the genus Sterechinus. The species S. neumayeri is indeed the most dependent on environmental conditions that prevail along the Antarctic coasts (sea surface temperature and sea-ice cover), while S. antarcticus doesn’t seem to be so much under the control of these parameters. Accordingly, the potential distribution of S. antarcticus in latitude is the most extended. However, S. antarcticus is not present over the whole area of its potential distribution, what can be explained as the result of either (1) oceanographic factors (role of the Polar Front as a biogeographical barrier), (2) biotic interactions (inter-specific competition) or (3) the temporal context (still ongoing colonization)

    Macroécologie des échinides de l'océan Austral : Distribution, Biogéographie et Modélisation

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    What are the forcing factors and main patterns of species distribution? This question is the core of macroecological issues and is of particular interest in the present context of global warming. The main objectives of this thesis were to determine the current distribution patterns of Antarctic and sub-Antarctic echinoid species at the scale of the whole Southern Ocean and to highlight the forcing factors that control them. The ecological niche modelling of 19 echinoid species showed that distribution is mainly structured in two patterns: (1) a first one represented by species that are not limited to the south of the Polar Front and distributed from the Antarctic coasts to the sub-Antarctic and cold temperate areas, and (2) a second one with species restricted to the Antarctic area. Within these two main patterns, five sub-patterns were also identified that depend on differences in the latitudinal and depth range of species groupings. In addition to this approach of biogeography by ecological niche modelling, a similarity analysis of echinoid, bivalve and gastropod fauna between bioregions of the Southern Ocean was performed at species and genus levels. This analysis reveals faunal connections between southern South America and sub-Antarctic areas in echinoids and bivalves, along with a partition between the East and West Antarctic. On the contrary, sub-Antarctic gastropod fauna show Antarctic rather than South American affinities and the Antarctic form a sole and unique province in this clade. These differences between clades are interpreted as the result of distinct biogeographic and evolutionary histories between echinoids and bivalves on the one hand, and gastropods on the other hand. The proposed hypothesis is that clades developped different evolutionary responses to the environmental changes that occurred during the Cenozoic. Finally, in the three clades, trans-Antarctic faunal connections are shown and interpreted as a result of West Antarctic Ice Sheet collapses and the setting up of trans-Antarctic sea-ways during the Pleistocene. Among the environmental parameters used for the ecological niche modelling, results show that the three following parameters play the main part in echinoid distribution: depth, sea-ice cover and sea surface temperature. However, the relative importance of these parameters depends on the species under studies. These differences are particularly emphasized in the case study of the genus Sterechinus. The species S. neumayeri is indeed the most dependent on environmental conditions that prevail along the Antarctic coasts (sea surface temperature and sea-ice cover), while S. antarcticus doesn’t seem to be so much under the control of these parameters. Accordingly, the potential distribution of S. antarcticus in latitude is the most extended. However, S. antarcticus is not present over the whole area of its potential distribution, what can be explained as the result of either (1) oceanographic factors (role of the Polar Front as a biogeographical barrier), (2) biotic interactions (inter-specific competition) or (3) the temporal context (still ongoing colonization).Quels sont les grands patrons de distribution des espĂšces et quels sont les facteurs qui les contrĂŽlent? Ces questions sont au cƓur des problĂ©matiques macroĂ©cologiques et prennent un intĂ©rĂȘt tout particulier au regard du rĂ©chauffement climatique global actuel. L’objectif principal de ce travail de thĂšse Ă©tait de dĂ©terminer les patrons de distribution actuels des espĂšces d’oursins antarctiques et subantarctiques Ă  l’échelle de l’ocĂ©an Austral et de mettre en Ă©vidence les facteurs qui contrĂŽlent ces distributions. La modĂ©lisation des niches Ă©cologiques d’une vingtaine d’espĂšces d’oursins a permis de mettre en Ă©vidence deux grands patrons de distribution : (1) un premier reprĂ©sentĂ© par les espĂšces dont la distribution n’est pas limitĂ©e au sud du Front Polaire et s’étend des cĂŽtes antarctiques aux zones subantarctiques et tempĂ©rĂ©es froides et (2) un deuxiĂšme constituĂ© d’espĂšces restreintes Ă  la zone antarctique. Au sein de ces deux patrons, cinq sous-patrons ont Ă©galement pu ĂȘtre dĂ©fini sur la base de diffĂ©rences de distribution latitudinale et bathymĂ©trique entre groupes d’espĂšces. Cette approche biogĂ©ographique par modĂ©lisation de niche Ă©cologique a Ă©tĂ© complĂ©tĂ©e par l’analyse de similaritĂ© de l’ensemble des faunes d’oursins, de bivalves et de gastĂ©ropodes, au niveau spĂ©cifique et gĂ©nĂ©rique, entre biorĂ©gions de l’ocĂ©an Austral. Cette analyse dĂ©montre qu’il existe chez les oursins et les bivalves des connexions fauniques entre l’AmĂ©rique du Sud et les zones subantarctiques ainsi qu’une sĂ©paration entre l’Est et l’Ouest antarctique. Au contraire, les faunes de gastĂ©ropodes subantarctiques montrent des affinitĂ©s plutĂŽt antarctiques que sud-amĂ©ricaines, l’Antarctique ne formant qu’une unique province pour ce clade. Ces diffĂ©rences entre clades sont interprĂ©tĂ©es comme Ă©tant le rĂ©sultat d’histoires Ă©volutive et biogĂ©ographique distinctes entre oursins et bivalves d’une part et gastĂ©ropodes d’autre part. L’hypothĂšse d’une rĂ©ponse Ă©volutive diffĂ©rente des clades aux changements environnementaux survenus au cours du CĂ©nozoĂŻque est avancĂ©e. Enfin, l’existence de connexions fauniques trans-antarctiques est mise en Ă©vidence dans l’étude des trois clades ; celles-ci sont interprĂ©tĂ©es comme le rĂ©sultat de la dislocation de la calotte ouest-antarctique et l’ouverture de bras de mer trans-antarctiques au cours du PlĂ©istocĂšne. Parmi les paramĂštres environnementaux utilisĂ©s dans la modĂ©lisation des niches Ă©cologiques, les rĂ©sultats montrent que trois paramĂštres jouent un rĂŽle majeur dans la distribution des oursins : la profondeur, la couverture de glace et la tempĂ©rature des eaux de surface. Toutefois, l’importance relative de ces paramĂštres diffĂšre selon les espĂšces d’oursins Ă©tudiĂ©es. L’étude du genre Sterechinus souligne tout particuliĂšrement ces diffĂ©rences. En effet, l’espĂšce S. neumayeri est plus sensible aux conditions environnementales qui prĂ©dominent prĂšs des cĂŽtes antarctiques (tempĂ©rature des eaux de surface et couverture de glace), alors que S. antarcticus semble ĂȘtre beaucoup moins contraint par ces mĂȘmes paramĂštres. La distribution potentielle de S. antarcticus est d’ailleurs beaucoup plus Ă©tendue en latitude. Cependant, S. antarcticus n’est pas prĂ©sent sur l’ensemble de son aire de distribution potentielle, ceci pouvant ĂȘtre expliquĂ© alternativement par le rĂ©sultat (1) de facteurs ocĂ©anographiques (rĂŽle de barriĂšre biogĂ©ographique jouĂ© par le Front Polaire), (2) d’interactions biotiques (phĂ©nomĂšnes de compĂ©tition inter-spĂ©cifique) et (3) du contexte temporel (colonisation toujours en cours)

    BIOGEOGRAPHY AND MACROECOLOGY OF ANTARCTIC AND SUB-ANTARCTIC ECHINOIDS USING A GEOGRAPHIC INFORMATION SYSTEM.

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    participantMany features already show how Polar seas are impacted by present-day global warming. To cope with new climate-induced changes and survive, Antarctic and Subantarctic marine organisms can either migrate or adapt to new prevailing conditions. New biotic interactions between Southernmost species and Subantarctic invaders can be expected, as new biogeographical distributions have already been documented. Because they are biologically and ecologically well diversified, echinoids play an important part in Antarctic benthic communities. Moreover, symbioses associated to cidarid echinoids make them even more crucial for benthic diversity. The biogeographical mapping of Antarctic echinoids (south of latitude 35° S) is being performed using both data from literature and new records from the numerous recent cruise campaigns around Antarctica. The second step and objective of our work is to identify and characterize the main factors that control echinoid distribution in the Antarctic. To obtain a comprehensive model of echinoid biogeographical and macroecological patterns, physical data are matched to echinoid distribution using GIS. Two alternative hypotheses will be tested: (1) is Antarctic echinoid distribution controlled by environmental and physical factors such as water temperature, sediments and depth (the environmental hypothesis) or (2) is echinoid distribution best explained by historical biogeography (the provincialist hypothesis)

    Macroécologie des échinides de l'océan Austral (Distribution, Biogéographie et Modélisation)

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    Quels sont les grands patrons de distribution des espĂšces et quels sont les facteurs qui les contrĂŽlent? Ces questions sont au cƓur des problĂ©matiques macroĂ©cologiques et prennent un intĂ©rĂȘt tout particulier au regard du rĂ©chauffement climatique global actuel. L objectif principal de ce travail de thĂšse Ă©tait de dĂ©terminer les patrons de distribution actuels des espĂšces d oursins antarctiques et subantarctiques Ă  l Ă©chelle de l ocĂ©an Austral et de mettre en Ă©vidence les facteurs qui contrĂŽlent ces distributions. La modĂ©lisation des niches Ă©cologiques d une vingtaine d espĂšces d oursins a permis de mettre en Ă©vidence deux grands patrons de distribution : (1) un premier reprĂ©sentĂ© par les espĂšces dont la distribution n est pas limitĂ©e au sud du Front Polaire et s Ă©tend des cĂŽtes antarctiques aux zones subantarctiques et tempĂ©rĂ©es froides et (2) un deuxiĂšme constituĂ© d espĂšces restreintes Ă  la zone antarctique. Au sein de ces deux patrons, cinq sous-patrons ont Ă©galement pu ĂȘtre dĂ©fini sur la base de diffĂ©rences de distribution latitudinale et bathymĂ©trique entre groupes d espĂšces. Cette approche biogĂ©ographique par modĂ©lisation de niche Ă©cologique a Ă©tĂ© complĂ©tĂ©e par l analyse de similaritĂ© de l ensemble des faunes d oursins, de bivalves et de gastĂ©ropodes, au niveau spĂ©cifique et gĂ©nĂ©rique, entre biorĂ©gions de l ocĂ©an Austral. Cette analyse dĂ©montre qu il existe chez les oursins et les bivalves des connexions fauniques entre l AmĂ©rique du Sud et les zones subantarctiques ainsi qu une sĂ©paration entre l Est et l Ouest antarctique. Au contraire, les faunes de gastĂ©ropodes subantarctiques montrent des affinitĂ©s plutĂŽt antarctiques que sud-amĂ©ricaines, l Antarctique ne formant qu une unique province pour ce clade. Ces diffĂ©rences entre clades sont interprĂ©tĂ©es comme Ă©tant le rĂ©sultat d histoires Ă©volutive et biogĂ©ographique distinctes entre oursins et bivalves d une part et gastĂ©ropodes d autre part. L hypothĂšse d une rĂ©ponse Ă©volutive diffĂ©rente des clades aux changements environnementaux survenus au cours du CĂ©nozoĂŻque est avancĂ©e. Enfin, l existence de connexions fauniques trans-antarctiques est mise en Ă©vidence dans l Ă©tude des trois clades ; celles-ci sont interprĂ©tĂ©es comme le rĂ©sultat de la dislocation de la calotte ouest-antarctique et l ouverture de bras de mer trans-antarctiques au cours du PlĂ©istocĂšne. Parmi les paramĂštres environnementaux utilisĂ©s dans la modĂ©lisation des niches Ă©cologiques, les rĂ©sultats montrent que trois paramĂštres jouent un rĂŽle majeur dans la distribution des oursins : la profondeur, la couverture de glace et la tempĂ©rature des eaux de surface. Toutefois, l importance relative de ces paramĂštres diffĂšre selon les espĂšces d oursins Ă©tudiĂ©es. L Ă©tude du genre Sterechinus souligne tout particuliĂšrement ces diffĂ©rences. En effet, l espĂšce S. neumayeri est plus sensible aux conditions environnementales qui prĂ©dominent prĂšs des cĂŽtes antarctiques (tempĂ©rature des eaux de surface et couverture de glace), alors que S. antarcticus semble ĂȘtre beaucoup moins contraint par ces mĂȘmes paramĂštres. La distribution potentielle de S. antarcticus est d ailleurs beaucoup plus Ă©tendue en latitude. Cependant, S. antarcticus n est pas prĂ©sent sur l ensemble de son aire de distribution potentielle, ceci pouvant ĂȘtre expliquĂ© alternativement par le rĂ©sultat (1) de facteurs ocĂ©anographiques (rĂŽle de barriĂšre biogĂ©ographique jouĂ© par le Front Polaire), (2) d interactions biotiques (phĂ©nomĂšnes de compĂ©tition inter-spĂ©cifique) et (3) du contexte temporel (colonisation toujours en cours).What are the forcing factors and main patterns of species distribution? This question is the core of macroecological issues and is of particular interest in the present context of global warming. The main objectives of this thesis were to determine the current distribution patterns of Antarctic and sub-Antarctic echinoid species at the scale of the whole Southern Ocean and to highlight the forcing factors that control them. The ecological niche modelling of 19 echinoid species showed that distribution is mainly structured in two patterns: (1) a first one represented by species that are not limited to the south of the Polar Front and distributed from the Antarctic coasts to the sub-Antarctic and cold temperate areas, and (2) a second one with species restricted to the Antarctic area. Within these two main patterns, five sub-patterns were also identified that depend on differences in the latitudinal and depth range of species groupings. In addition to this approach of biogeography by ecological niche modelling, a similarity analysis of echinoid, bivalve and gastropod fauna between bioregions of the Southern Ocean was performed at species and genus levels. This analysis reveals faunal connections between southern South America and sub-Antarctic areas in echinoids and bivalves, along with a partition between the East and West Antarctic. On the contrary, sub-Antarctic gastropod fauna show Antarctic rather than South American affinities and the Antarctic form a sole and unique province in this clade. These differences between clades are interpreted as the result of distinct biogeographic and evolutionary histories between echinoids and bivalves on the one hand, and gastropods on the other hand. The proposed hypothesis is that clades developped different evolutionary responses to the environmental changes that occurred during the Cenozoic. Finally, in the three clades, trans-Antarctic faunal connections are shown and interpreted as a result of West Antarctic Ice Sheet collapses and the setting up of trans-Antarctic sea-ways during the Pleistocene. Among the environmental parameters used for the ecological niche modelling, results show that the three following parameters play the main part in echinoid distribution: depth, sea-ice cover and sea surface temperature. However, the relative importance of these parameters depends on the species under studies. These differences are particularly emphasized in the case study of the genus Sterechinus. The species S. neumayeri is indeed the most dependent on environmental conditions that prevail along the Antarctic coasts (sea surface temperature and sea-ice cover), while S. antarcticus doesn t seem to be so much under the control of these parameters. Accordingly, the potential distribution of S. antarcticus in latitude is the most extended. However, S. antarcticus is not present over the whole area of its potential distribution, what can be explained as the result of either (1) oceanographic factors (role of the Polar Front as a biogeographical barrier), (2) biotic interactions (inter-specific competition) or (3) the temporal context (still ongoing colonization).DIJON-BU Doc.Ă©lectronique (212319901) / SudocSudocFranceF

    Echinoids.

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    8 pagesInternational audienc

    Biogeographic processes in the Southern Ocean

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    8 pagesInternational audienc

    Antarctic, Sub-Antarctic and cold temperate echinoid database

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    Abstract This database includes spatia
    corecore