| 1. |
- Logares, Ramiro, et al.
(författare)
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Biogeography of bacterial communities exposed to progressive long-term environmental change
- 2013
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Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 7:5, s. 937-948
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Tidskriftsartikel (refereegranskat)abstract
- The response of microbial communities to long-term environmental change is poorly understood. Here, we study bacterioplankton communities in a unique system of coastal Antarctic lakes that were exposed to progressive long-term environmental change, using 454 pyrosequencing of the 16S rDNA gene (V3-V4 regions). At the time of formation, most of the studied lakes harbored marine-coastal microbial communities, as they were connected to the sea. During the past 20 000 years, most lakes isolated from the sea, and subsequently they experienced a gradual, but strong, salinity change that eventually developed into a gradient ranging from freshwater (salinity 0) to hypersaline (salinity 100). Our results indicated that present bacterioplankton community composition was strongly correlated with salinity and weakly correlated with geographical distance between lakes. A few abundant taxa were shared between some lakes and coastal marine communities. Nevertheless, lakes contained a large number of taxa that were not detected in the adjacent sea. Abundant and rare taxa within saline communities presented similar biogeography, suggesting that these groups have comparable environmental sensitivity. Habitat specialists and generalists were detected among abundant and rare taxa, with specialists being relatively more abundant at the extremes of the salinity gradient. Altogether, progressive long-term salinity change appears to have promoted the diversification of bacterioplankton communities by modifying the composition of ancestral communities and by allowing the establishment of new taxa. The ISME Journal (2013) 7, 937-948; doi:10.1038/ismej.2012.168; published online 20 December 2012
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| 2. |
- Logares, Ramiro, et al.
(författare)
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Genetic diversity patterns in five protist species occuring in lakes
- 2009
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Ingår i: Protist. - : Elsevier BV. - 1434-4610 .- 1618-0941. ; 160:2, s. 301-317
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the extent of the genetic diversity and its structuring patterns in protist species living in lakes. Here, we have investigated the genetic diversity patterns within five dinoflagellate species (Peridinium aciculiferum, Peridinium cinctum, Peridiniopsis borgei, Polarella glacialis, Scrippsiella aff. hangoei) that are present in lakes and sometimes, in marine habitats located in polar and temperate regions. A total of 68 clonal strains were investigated using Amplified Fragment Length Polymorphism (AFLP), a sensitive genetic fingerprinting technique. All used strains within each species had identical ITS nuclear ribosomal DNA sequences, a characteristic that indicates that they likely belong to the same species. We found a wide variability in the genetic diversity among species (between 20% and 90% of polymorphic loci; Nei's gene diversity between 0.08 and 0.37). In some cases, our analyses suggested the presence of different genetically homogeneous subgroups (genetic populations) within the same water body. Thus, it appears that different genetic populations can coexist within the same lake despite the likely occurrence of recombination that tends to homogenize the gene pool. Overall, our results indicated that a large number of dinoflagellate genotypes are present in lake populations, instead of a few dominating ones. In addition, our study shows that protists with identical ITS sequences can harbor considerable amounts of genetic diversity.
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| 3. |
- Logares, Ramiro, et al.
(författare)
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Recent evolutionary diversification of a protist lineage.
- 2008
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 10:5, s. 1231-1243
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Tidskriftsartikel (refereegranskat)abstract
- Here, we have identified a protist (dinoflagellate) lineage that has diversified recently in evolutionary terms. The species members of this lineage inhabit cold-water marine and lacustrine habitats, which are distributed along a broad range of salinities (0–32) and geographic distances (0–18 000 km). Moreover, the species present different degrees of morphological and sometimes physiological variability. Altogether, we analysed 30 strains, generating 55 new DNA sequences. The nuclear ribosomal DNA (nrDNA) sequences (including rapidly evolving introns) were very similar or identical among all the analysed isolates. This very low nrDNA differentiation was contrasted by a relatively high cytochrome b (COB) mitochondrial DNA (mtDNA) polymorphism, even though the COB evolves very slowly in dinoflagellates. The 16 Maximum Likelihood and Bayesian phylogenies constructed using nr/mtDNA indicated that the studied cold-water dinoflagellates constitute a monophyletic group (supported also by the morphological analyses), which appears to be evolutionary related to marine-brackish and sometimes toxic Pfiesteria species. We conclude that the studied dinoflagellates belong to a lineage which has diversified recently and spread, sometimes over long distances, across low-temperature environments which differ markedly in ecology (marine versus lacustrine communities) and salinity. Probably, this evolutionary diversification was promoted by the variety of natural selection regimes encountered in the different environments.
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| 4. |
- Rengefors, Karin, et al.
(författare)
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Evidence of concurrentlocal adaptation and high phenotypic plasticityin a polar microeukaryote.
- 2015
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2920 .- 1462-2912. ; 17:5, s. 1510-1519
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Tidskriftsartikel (refereegranskat)abstract
- Here we investigated whether there is evidence of local adaptation in strains of an ancestrallymarine dinoflagellate to the lacustrine environment they now inhabit(optimal genotypes) and/orif they have evolved phenotypic plasticity (a range of phenotypes). Eleven strains of Polarella glacialis were isolated and cultured from three different environments: the polar seas, ahyposaline,and a hypersaline Antarctic lake. Local adaptation was tested by comparing growth rates of lacustrine and marine strains at their own and reciprocal site conditions. To determine phenotypic plasticity, we measured thereaction norm for salinity.We found evidence of both, limitedlocal adaptation andhigherphenotypic plasticity in lacustrine strains when compared tomarine ancestors. At extreme high salinities,local lake strains outperformed otherstrains, and at extreme low salinities, strains from the hyposaline lake outperformed all other strains. The data suggest that lake populations may have evolved higher phenotypic plasticity in the lake habitats compared to the sea, presumably due to the high temporal variability in salinity in the lacustrine systems. Moreover, the interval of salinity tolerance differed between strains from the hyposalineand hypersaline lakes, indicatinglocal adaptation promoted by different salinity.
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| 5. |
- Rengefors, Karin, et al.
(författare)
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Marine-derived dinoflagellates in Antarctic saline lakes: annual dynamics and community composition
- 2008
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 44:3, s. 592-604
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Tidskriftsartikel (refereegranskat)abstract
- The saline lakes of the Vestfold Hills in Antarctica offer a remarkable natural laboratory where the adaptation of planktonic protists to a range of evolving physiochemical conditions can be investigated. This study illustrates how an ancestral marine community has undergone radical simplification leaving a small number of well-adapted species. Our objective was to investigate the species composition and annual dynamics of dinoflagellate communities in three saline Antarctic lakes. We observed that dinoflagellates occur year-round despite extremely low PAR during the southern winter, which suggests significant mixotrophic or heterotrophic activity. Only a small number of dominant dinoflagellate species were found in each lake, in contrast to the species-rich Southern Ocean from which the lake communities are believed to be derived. We verified that the lake species were representatives of the marine polar dinoflagellate community, and not freshwater species. Polarella glacialis Montresor, Procaccini et Stoecker, a bipolar marine species, was for the first time described in a lake habitat and was an important phototrophic component in the higher salinity lakes. In the brackish lakes, we found a new sibling species to the brackish-water species Scrippsiella hangoei (J. Schiller) J. Larsen, previously observed only in the Baltic Sea.
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