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| Cavaleiro, Catarina; Voelker, Antje Hl; Stoll, Heather; Baumann, Karl-heinz; Kucera, Michal. |
| Coccolithophores contribute significantly to the marine primary productivity and play a unique role in ocean biogeochemistry by using carbon for photosynthesis (biological pump) and also for calcification (carbonate pump). Despite the importance of including coccolithophores in global climate models to allow better predictions of the climate system's responses to planetary change, highly uncertain coccolithophore paleoproductivity past reconstructions mostly relied on proxies dependent on accumulation and sedimentation rates, and preservation conditions. In this study we used an independent proxy, based on the coccolith fraction (CF) Sr/Ca ratio, to reconstruct coccolithophore productivity. We used the marine sediment core MD03-2699 from the western... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00590/70244/68282.pdf |
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| Morard, Raphaël; Füllberg, Angelina; Brummer, Geert-jan A.; Greco, Mattia; Jonkers, Lukas; Wizemann, André; Weiner, Agnes K. M.; Darling, Kate; Siccha, Michael; Ledevin, Ronan; Kitazato, Hiroshi; De Garidel-thoron, Thibault; De Vargas, Colomban; Kucera, Michal. |
| The planktonic foraminifera genus Globigerinoides provides a prime example of a species-rich genus in which genetic and morphological divergence are uncorrelated. To shed light on the evolutionary processes that lead to the present-day diversity of Globigerinoides, we investigated the genetic, ecological and morphological divergence of its constituent species. We assembled a global collection of single-cell barcode sequences and show that the genus consists of eight distinct genetic types organized in five extant morphospecies. Based on morphological evidence, we reassign the species Globoturborotalita tenella to Globigerinoides and amend Globigerinoides ruber by formally proposing two new subspecies, G. ruber albus n.subsp. and G. ruber ruber in order to... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00595/70719/68946.pdf |
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| Weiner, Agnes K. M.; Morard, Raphael; Weinkauf, Manuel F. G.; Darling, Kate F.; André, Aurore; Quillévéré, Frédéric; Ujiie, Yurika; Douady, Christophe J.; De Vargas, Colomban; Kucera, Michal. |
| Single-cell genetic analysis is an essential method to investigate the biodiversity and evolutionary ecology of marine protists. In protist groups that do not reproduce under laboratory conditions, this approach provides the only means to directly associate molecular sequences with cell morphology. The resulting unambiguous taxonomic identification of the DNA sequences is a prerequisite for barcoding and analyses of environmental metagenomic data. Extensive single-cell genetic studies have been carried out on planktonic foraminifera over the past 20 years to elucidate their phylogeny, cryptic diversity, biogeography, and the relationship between genetic and morphological variability. In the course of these investigations, it has become evident that genetic... |
| Tipo: Text |
Palavras-chave: Foraminifera; Protists; Single-cell genetics; Cryptic diversity; Comparability; Methods; Laboratory protocols; Standardization. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00383/49460/49938.pdf |
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| Dickson, Alexander J.; Austin, William E. N.; Hall, Ian R.; Maslin, Mark A.; Kucera, Michal. |
| 1] There is much uncertainty surrounding the mechanisms that forced the abrupt climate fluctuations found in many palaeoclimate records during Marine Isotope Stage (MIS)-3. One of the processes thought to be involved in these events is the Atlantic Meridional Overturning Circulation ( MOC), which exhibited large changes in its dominant mode throughout the last glacial period. Giant piston core MD95- 2006 from the northeast Atlantic Ocean records a suite of palaeoceanographic proxies related to the activity of both surface and deep water masses through a period of MIS- 3 when abrupt climate fluctuations were extremely pronounced. A two- stage progression of surface water warming during interstadial warm events is proposed, with initial warming related to... |
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| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00237/34824/33304.pdf |
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| Morard, Raphael; Escarguel, Gilles; Weiner, Agnes K. M.; Andre, Aurore; Douady, Christophe J.; Wade, Christopher M.; Darling, Kate F.; Ujiie, Yurika; Seears, Heidi A.; Quillevere, Frederic; De Garidel-thoron, Thibault; De Vargas, Colomban; Kucera, Michal. |
| Investigations of biodiversity, biogeography, and ecological processes rely on the identification of "species" as biologically significant, natural units of evolution. In this context, morphotaxonomy only provides an adequate level of resolution if reproductive isolation matches morphological divergence. In many groups of organisms, morphologically defined species often disguise considerable genetic diversity, which may be indicative of the existence of cryptic species. The diversity hidden by morphological species can be disentangled through genetic surveys, which also provide access to data on the ecological distribution of genetically circumscribed units. These units can be identified by unique DNA sequence motifs and allow studies of evolutionary and... |
| Tipo: Text |
Palavras-chave: Cryptic species; Genetic diversity; Planktonic foraminifera; Molecular nomenclature; MOTUs. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00383/49408/49900.pdf |
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