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Andre, Aurore; Quillevere, Frederic; Morard, Raphael; Ujiie, Yurika; Escarguel, Gilles; De Vargas, Colomban; De Garidel-thoron, Thibault; Douady, Christophe J.. |
The use of planktonic foraminifera in paleoceanography requires taxonomic consistency and precise assessment of the species biogeography. Yet, ribosomal small subunit (SSUr) DNA analyses have revealed that most of the modern morphospecies of planktonic foraminifera are composed of a complex of several distinct genetic types that may correspond to cryptic or pseudo-cryptic species. These genetic types are usually delimitated using partial sequences located at the 3'end of the SSUrDNA, but typically based on empirical delimitation. Here, we first use patristic genetic distances calculated within and among genetic types of the most common morpho-species to show that intra-type and inter-type genetic distances within morpho-species may significantly overlap,... |
Tipo: Text |
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Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00290/40107/38859.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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Ishitani, Yoshiyuki; Ujiie, Yurika; De Vargas, Colomban; Not, Fabrice; Takahashi, Kozo. |
Collodaria are the only group of Radiolaria that has a colonial lifestyle. This group is potentially the most important plankton in the oligotrophic ocean because of its large biomass and the high primary productivity associated with the numerous symbionts inside a cell or colony. The evolution of Collodaria could thus be related to the changes in paleo-productivity that have affected organic carbon fixation in the oligotrophic ocean. However, the fossil record of Collodaria is insufficient to trace their abundance through geological time, because most collodarians do not have silicified shells. Recently, molecular phylogeny based on nuclear small sub-unit ribosomal DNA (SSU rDNA) confirmed Collodaria to be one of five orders of Radiolaria, though the... |
Tipo: Text |
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Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00140/25108/23217.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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Ujiie, Yurika; Asahi, Hirofumi; Sagawa, Takuya; Bassinot, Franck. |
The North Pacific Subtropical Gyre (NPSG) has two important functions, i.e., one in ocean heat transfer and another as a driving force for circulation of the surface and intermediate waters on the basin scale. In the present study, we describe records of the vertical thermal structures and distributions of water masses in the upper ocean of the subtropical northwest (NW) Pacific for the past 190 kyr, using two sediment cores collected from the Kuroshio Current area in the East China Sea and the NPSG area. During the two glacial periods, the Kuroshio Current was weakened owing to changes in ocean-atmosphere circulation and eustasy. The differences in the Mg/Ca-derived temperatures between surface and thermocline waters show the changes of depth and... |
Tipo: Text |
Palavras-chave: North Pacific Subtropical Gyre; LGM; MIS 6; Paleotemperature; Water-column structure. |
Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00358/46911/46812.pdf |
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