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Auteur NIEBLAS, A.-E.; DEMARCQ, H.; DRUSHKA, K.; SLOYAN, B.; BONHOMMEAU, S.
Titre (up) Front variability and surface ocean features of the presumed southern bluefin tuna spawning grounds in the tropical southeast Indian Ocean Type Article scientifique
Année 2014 Publication Revue Abrégée Deep-sea Research Part II-topical Studies In Oceanography
Volume 107 Numéro Pages 64-76
Mots-Clés Front detection index; Indo-Australian region; Oceanic fronts; Southern bluefin tuna Thunnus maccoyii; Spawning grounds (10 degrees S-20 degrees S 105 degrees E-125 degrees E); Tropical southeast Indian Ocean
Résumé The southern bluefin tuna (SBT, Thunnus maccoyii) is an ecologically and economically valuable fish. However, surprisingly little is known about its critical early life history, a period when mortality is several orders of magnitude higher than at any other life stage, and when larvae are highly sensitive to environmental conditions. Ocean fronts can be important in creating favourable spawning conditions, as they are a convergence of water masses with different properties that can concentrate planktonic particles and lead to enhanced productivity. In this study, we examine the front activity within the only region where SBT have been observed to spawn: the tropical southeast Indian Ocean between Indonesia and Australia (10 degrees S-20 degrees S, 105 degrees E-125 degrees E). We investigate front activity and its relationship to ocean dynamics and surface features of the region. Results are also presented for the entire Indian Ocean (30 degrees N-45 degrees S, 20 degrees E-140 degrees E) to provide a background context. We use an extension of the Cayula and Cornillon algorithm to detect ocean fronts from satellite images of sea surface temperature (SST) and chlorophyll-a concentration (chl-a). Front occurrence represents the probability of occurrence of a front at each pixel of an image. Front intensity represents the magnitude of the difference between the two water masses that make up a front. Relative to the rest of the Indian Ocean, both SST and chl-a fronts in the offshore spawning region are persistent in occurrence and weak in intensity. Front occurrence and intensity along the Australian coast are high, with persistent and intense fronts found along the northwest and west coasts. Fronts in the tropical southeast Indian Ocean are shown to have strong annual variability and some moderate interannual variability. SST front occurrence is found to lead the Southern Oscillation Index by one year, potentially linked to warming and wind anomalies in the Indian Ocean. The surface ocean characteristics of the offshore SBT spawning region are found to be particularly stable compared to the rest of the Indian Ocean in terms of stable SST, low eddy kinetic energy, i.e., low mesoscale eddy activity, and low chl-a. However, this region has high front occurrence, but low front intensity of both SST and chl-a fronts. The potential impact of these oceanic features for SBT spawning is discussed.
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ISSN 0967-0645 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1131
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Auteur Villeger, S.; Grenouillet, G.; Brosse, S.
Titre (up) Functional homogenization exceeds taxonomic homogenization among European fish assemblages Type Article scientifique
Année 2014 Publication Revue Abrégée Global Ecology and Biogeography
Volume 23 Numéro 12 Pages 1450-1460
Mots-Clés beta-diversity; exotic species; functional diversity; Non-native species; taxonomic dissimilarity; translocation
Résumé Aim Human activities and the consequent extirpations of native species and introductions of non-native species have been modifying the composition of species assemblages throughout the world. These anthropogenic impacts have modified the richness of assemblages as well as the biological dissimilarity among them. However, while changes in taxonomic dissimilarity (i.e. accounting for species composition) have been assessed intensively during the last decade there are still few assessments of changes in functional dissimilarity (i.e. accounting for the diversity of biological traits). Here, we assess the temporal changes in both taxonomic and functional dissimilarities for freshwater fish assemblages across Europe. Location Western Palaearctic, 137 river basins. Methods The Jaccard index was used to quantify the changes in both taxonomic and functional dissimilarity. We then partitioned dissimilarity to extract its turnover component and measured the changes in the contribution of turnover to dissimilarity. Results Functional homogenization exceeded taxonomic homogenization six-fold. More importantly, we found only a moderate positive correlation between these changes. For instance, 40% of assemblages that experienced taxonomic differentiation were actually functionally homogenized. Taxonomic and functional homogenizations were stronger when the historical level of taxonomic dissimilarity among assemblages was high and when a high number of non-native species were introduced in the assemblages. Moreover, translocated species (i.e. non-native species originating from Europe) played a stronger role than exotic species (i.e. those coming from outside Europe) in this homogenization process, while extirpation did not play a significant role. Main conclusions Change in taxonomic diversity cannot be used to predict changes in functional diversity. In addition, as functional diversity has been proven to be a better indicator of ecosystem functioning and stability than taxonomic diversity, further studies are required to test the potential effects of functional homogenization at the local scale.
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ISSN 1466-8238 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 1178
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Auteur Mouillot, D.; Villeger, S.; Parravicini, V.; Kulbicki, M.; Arias-González, J.E.; Bender, M.; Chabanet, P.; Floeter, S.R.; Friedlander, A.; Vigliola, L.; Bellwood, D.R.
Titre (up) Functional over-redundancy and high functional vulnerability in global fish faunas on tropical reefs Type Article scientifique
Année 2014 Publication Revue Abrégée Proceedings of the National Academy of Sciences of the United States of America
Volume 111 Numéro 38 Pages 13757-13762
Mots-Clés
Résumé When tropical systems lose species, they are often assumed to be buffered against declines in functional diversity by the ability of the species-rich biota to display high functional redundancy: i.e., a high number of species performing similar functions. We tested this hypothesis using a ninefold richness gradient in global fish faunas on tropical reefs encompassing 6,316 species distributed among 646 functional entities (FEs): i.e., unique combinations of functional traits. We found that the highest functional redundancy is located in the Central Indo-Pacific with a mean of 7.9 species per FE. However, this overall level of redundancy is disproportionately packed into few FEs, a pattern termed functional over-redundancy (FOR). For instance, the most speciose FE in the Central Indo-Pacific contains 222 species (out of 3,689) whereas 38% of FEs (180 out of 468) have no functional insurance with only one species. Surprisingly, the level of FOR is consistent across the six fish faunas, meaning that, whatever the richness, over a third of the species may still be in overrepresented FEs whereas more than one third of the FEs are left without insurance, these levels all being significantly higher than expected by chance. Thus, our study shows that, even in high-diversity systems, such as tropical reefs, functional diversity remains highly vulnerable to species loss. Although further investigations are needed to specifically address the influence of redundant vs. vulnerable FEs on ecosystem functioning, our results suggest that the promised benefits from tropical biodiversity may not be as strong as previously thought.
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 600
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Auteur ADJEROUD, M.; GUERECHEAU, A.; VIDAL-DUPIOL, J.; FLOT, J.-F.; ARNAUD-HAOND, S.; BONHOMME, F.
Titre (up) Genetic diversity, clonality and connectivity in the scleractinian coral Pocillopora damicornis: a multi-scale analysis in an insular, fragmented reef system Type Article scientifique
Année 2014 Publication Revue Abrégée Marine Biology
Volume 161 Numéro 3 Pages 531-541
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Résumé Clonality and genetic structure of the coral Pocillopora damicornis sensu lato were assessed using five microsatellites in 12 populations from four islands of the Society Archipelago (French Polynesia) sampled in June 2008. The 427 analysed specimens fell into 132 multilocus genotypes (MLGs), suggesting that asexual reproduction plays an important role in the maintenance of these populations. A haploweb analysis of ITS2 sequences of each MLG was consistent with all of them being conspecific. Genetic differentiation was detected both between and within islands, but when a single sample per MLG was included in the analyses, the populations turned out to be nearly panmictic. These observations provide further evidence of the marked variability in reproductive strategies and genetic structure of P. damicornis throughout its geographic range; comparison with results previously obtained for the congeneric species Pocillopora meandrina underlines the importance of life history traits in shaping the genetic structure of coral populations
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ISSN 0025-3162 ISBN Médium
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Notes The following values have no corresponding Zotero field:<br/>Author Address: Inst Rech Dev, Unite 227, CoReUs2, Noumea 98848, New Caledonia.<br/>Author Address: CORAIL, Lab Excellence, F-66860 Perpignan, France.<br/>Author Address: Univ Perpignan, CNRS, UMR 5244, F-66860 Perpignan, France.<br/>Author Address: Univ Perpignan, UMR 5244, F-66860 Perpignan, France.<br/>Author Address: Max Planck Inst Dynam & Self Org, D-37073 Gottingen, Germany.<br/>Author Address: Inst Francais Rech Exploitat Mer, UMR 212, F-34203 Sete, France.<br/>Author Address: Univ Montpellier 2, Inst Sci Evolut, CNRS, UMR 5554, F-34095 Montpellier 5, France.<br/>PB – Springer<br/> Approuvé pas de
Numéro d'Appel LL @ pixluser @ collection 341
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Auteur Dias, M.S.; Oberdorff, T.; Hugueny, B.; Leprieur, F.; Jezequel, C.; Cornu, J.F.; Brosse, S.; Grenouillet, G.; Tedesco, P.A.
Titre (up) Global imprint of historical connectivity on freshwater fish biodiversity Type Article scientifique
Année 2014 Publication Revue Abrégée Ecology Letters
Volume 17 Numéro 9 Pages 1130-1140
Mots-Clés Alpha diversity; Beta diversity; Biogeography; Quaternary climate changes; africa; climate changes; contemporary; diversity patterns; endemism; evolution; freshwater fish; global; history; north-america; richness; river systems; scale; sea-level changes; species turnover; species-richness
Résumé The relative importance of contemporary and historical processes is central for understanding biodiversity patterns. While several studies show that past conditions can partly explain the current biodiversity patterns, the role of history remains elusive. We reconstructed palaeo-drainage basins under lower sea level conditions (Last Glacial Maximum) to test whether the historical connectivity between basins left an imprint on the global patterns of freshwater fish biodiversity. After controlling for contemporary and past environmental conditions, we found that palaeo-connected basins displayed greater species richness but lower levels of endemism and beta diversity than did palaeo-disconnected basins. Palaeo-connected basins exhibited shallower distance decay of compositional similarity, suggesting that palaeo-river connections favoured the exchange of fish species. Finally, we found that a longer period of palaeo-connection resulted in lower levels of beta diversity. These findings reveal the first unambiguous results of the role played by history in explaining the global contemporary patterns of biodiversity.
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Langue English Langue du Résumé Titre Original
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ISSN 1461-023x ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 631
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