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Auteur Ramirez-Romero, E.; Molinero, J.C.; Sommer, U.; Salhi, N.; Yahia, O.K.-D.; Yahia, M.N.D.
Titre Phytoplankton size changes and diversity loss in the southwestern Mediterranean Sea in relation to long-term hydrographic variability Type Article scientifique
Année 2020 Publication Revue Abrégée Estuar. Coast. Shelf Sci.
Volume 235 Numéro Pages 106574
Mots-Clés bay; climate-change; Diversity loss; dynamics; evolution; jellyfish; marine; Nanophytoplankton; Ocean warming; patterns; Phytoplankton diversity; plankton communities; Size structural changes; Southwestern mediterranean; temperature; time-series
Résumé Structural changes in plankton primary producers have large implications for food web dynamics, energy fluxes and the vertical export of biogenic particulate carbon. Here we examine phytoplankton data spanning the period 1993-2008 from the Bay of Tunis, southwestern Mediterranean Sea, in relation to long term hydroclimate variability. We show a conspicuous shift in the structure of the phytoplankton community characterized by an increase of small-sized species and diversity loss, revealing a dominance of smaller blooming diatoms and cyanobacteria. Such changes were concurrent with marked modifications in hydroclimatic patterns experienced in the Bay of Tunis consisting of a shift towards enhanced winter precipitation together with rising temperatures. This novel study shows an overall rise in the proportion of small phytoplankton cells and a decreasing trend in phytoplankton diversity in the southern Mediterranean area. These findings warn of a potential decline of trophic efficiency and lesser food web stability resulting from mean size reduction and the diversity loss.
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ISSN 0272-7714 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection (down) 2766
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Auteur Thomas, F.; Dittami, S.M.; Brunet, M.; Le Duff, N.; Tanguy, G.; Leblanc, C.; Gobet, A.
Titre Evaluation of a new primer combination to minimize plastid contamination in 16S rDNA metabarcoding analyses of alga-associated bacterial communities Type Article scientifique
Année 2020 Publication Revue Abrégée Environ. Microbiol. Rep.
Volume 12 Numéro 1 Pages 30-37
Mots-Clés diversity; phylogenetic analysis; ribosomal-rna sequences; surfaces
Résumé Plant- and alga-associated bacterial communities are generally described via 16S rDNA metabarcoding using universal primers. As plastid genomes encode 16S rDNA related to cyanobacteria, these data sets frequently contain >90% plastidial sequences, and the bacterial diversity may be under-sampled. To overcome this limitation we evaluated in silico the taxonomic coverage for four primer combinations targeting the 16S rDNA V3-V4 region. They included a forward primer universal to Bacteria (S-D-Bact-0341-b-S-17) and four reverse primers designed to avoid plastid DNA amplification. The best primer combination (NOCHL) was compared to the universal primer set in the wet lab using a synthetic community and samples from three macroalgal species. The proportion of plastid sequences was reduced by 99%-100% with the NOCHL primers compared to the universal primers, irrespective of algal hosts, sample collection and extraction protocols. Additionally, the NOCHL primers yielded a higher richness while maintaining the community structure. As Planctomycetes, Verrucomicrobia and Cyanobacteria were underrepresented (70%-90%) compared to universal primers, combining the NOCHL set with taxon-specific primers may be useful for a complete description of the alga-associated bacterial diversity. The NOCHL primers represent an innovation to study algal holobionts without amplifying host plastid sequences and may further be applied to other photosynthetic hosts.
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Volume de collection Numéro de collection Edition
ISSN 1758-2229 ISBN Médium
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Notes WOS:000498132200001 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection (down) 2759
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Auteur Legras, G.; Loiseau, N.; Gaertner, J.-C.; Poggiale, J.-C.; Gaertner-Mazouni, N.
Titre Assessing functional diversity: the influence of the number of the functional traits Type Article scientifique
Année 2020 Publication Revue Abrégée Theor. Ecol.
Volume 13 Numéro 1 Pages 117-126
Mots-Clés biodiversity; Dissimilarity metric; framework; Functional diversity; Functional traits; global hotspots; Index sensitivity; indexes; mismatch; redundancy; reveals; species richness; Trend analysis; vulnerability
Résumé The impact of the variation of the number of functional traits on functional diversity assessment is still poorly known. Although the covariation between these two parameters may be desirable in some situations (e.g. if adding functional traits provides relevant new functional information), it may also result from mathematical artefacts and lead to misinterpretation of the results obtained. Here, we have tested the behaviour of a set of nine indices widely used for assessing the three main components of functional diversity (i.e. functional richness, evenness and divergence), according to the variation in the number of functional traits. We found that the number of functional traits may strongly impact the values of most of the indices considered, whatever the functional information they contain. The FRic, TOP and n-hypervolume indices that have been developed to characterize the functional richness component appeared to be highly sensitive to the variation in the number of traits considered. Regarding functional divergence, most of the indices considered (i.e. Q, FDis and FSpe) also showed a high degree of sensitivity to the number of traits considered. In contrast, we found that indices used to compute functional evenness (FEve and Ru), as well as one of the indices related to functional divergence (FDiv), are weakly influenced by the variation in the number of traits. All these results suggest that interpretation of most of the functional diversity indices considered cannot only be based on their values as they are, but requires taking into account the way in which they have been computed.
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Volume de collection Numéro de collection Edition
ISSN 1874-1738 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection (down) 2750
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Auteur Su, G.; Villeger, S.; Brosse, S.
Titre Morphological sorting of introduced freshwater fish species within and between donor realms Type Article scientifique
Année 2020 Publication Revue Abrégée Glob. Ecol. Biogeogr.
Volume Numéro Pages
Mots-Clés biogeographic realms; body-size; ecology; establishment; exported species; functional diversity; hydropower; imputation; invasion steps; invasion success; morphological traits; morphospace; nonnative fishes; rivers; trade; traits; translocated species
Résumé Aim: To determine which morphological characteristics make a fish species a good candidate for introduction and establishment, we tested whether (a) introduced species differ in morphology from non-introduced species (species only existing in native areas and not introduced to new areas) in each donor assemblage (biogeographic realm fauna); (b) within the introduced species, the morphology of established species (self-sustaining introduced species) differs from that of the non-established species; (c) within the established species, those exported out of their native realm have more extreme morphological traits than those translocated within their native realm. Major taxa studied: Freshwater fish. Location: Global. Time period: 1960s-2010s. Methods: We used a global database of freshwater fishes from the six realms. Ten morphological traits were measured on 9,150 species. Principal component analysis was conducted to combine the 10 traits into a multidimensional morphospace. We used permutational multivariate analysis of variance (PERMANOVA) and permutational analysis for the multivariate homogeneity of dispersions (PERMDISP2) to compare the distribution of species groups in the morphospace and Kolmogorov-Smirnov tests to compare their distributions on principal component (PC) axes. Results: The morphology of introduced species differed from that of non-introduced species in all the six biogeographic realms. Among introduced species, established species had more extreme morphological traits than non-established species in most realms. Among established species, exported species had more extreme morphological traits than translocated species. Main conclusions: Morphological differences between introduced and nonintroduced species rely on an anthropogenic trait selection for fisheries and angling, leading to the preference for the introduction of predators with large and laterally compressed bodies. Established introduced species represent a small subset of introduced species morphologies, with these species having more extreme morphological traits, probably making them more efficient in particular habitats than their non-established counterparts. This was particularly marked for fish morphologies adapted to lentic waters. Such a trend was apparent for exported species, which have more extreme traits than translocated species.
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Volume de collection Numéro de collection Edition
ISSN 1466-822x ISBN Médium
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Notes WOS:000512276700001 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection (down) 2740
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Auteur Leclerc, C.; Villeger, S.; Marino, C.; Bellard, C.
Titre Global changes threaten functional and taxonomic diversity of insular species worldwide Type Article scientifique
Année 2020 Publication Revue Abrégée Divers. Distrib.
Volume 26 Numéro 4 Pages 402-414
Mots-Clés biodiversity; birds; conservation; dimensions; extinction risk; functional specialization; functional originality; functional richness; islands; mammals; redundancy; species traits; trait; vulnerability
Résumé Aim The assessment of biodiversity patterns under global changes is currently biased towards taxonomic diversity, thus overlooking the ecological and functional aspects of species. Here, we characterized both taxonomic and functional diversity of insular biodiversity threatened by multiple threats. Location Worldwide islands (n = 4,348). Methods We analysed the relative importance of eleven major threats, including biological invasions or climate change, on 2,756 insular endemic mammals and birds. Species were functionally described using five ecological traits related to diet, habitat and body mass. We computed complementary taxonomic and functional diversity indices (richness, specialization, originality and vulnerability) of species pools affected by each threatening process to investigate relationships between diversity dimensions and threats. We also determined whether species-specific traits are associated with specific threats. Results On average, 8% of insular endemic species at risk of extinction are impacted by threats, while 20% of their functional richness is affected. However, a marked disparity in functional richness values associated with each threat can be highlighted. In particular, cultivation and wildlife exploitation are the greatest threats to insular endemic species. Moreover, each threat may contribute to the loss of at least 10% of functional diversity, because it affects threatened species that support unique and extreme functions. Finally, we found complex patterns of species-specific traits associated with particular threats that is not explain by the threatening processes (directly affecting survival or modifying habitat). For instance, cultivation threatens very large mammals, while urbanization threatens very small mammals. Main conclusions These findings reinforce the importance of exploring the vulnerability of biodiversity facets in the face of multiple threats. Anthropogenic pressures may result in a loss of unique functions within insular ecosystems, which provides important insights into the understanding of threatening processes at a global scale.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 1366-9516 ISBN Médium
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Notes WOS:000511022100001 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection (down) 2738
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