| 1. |
- Ellegaard, M., et al.
(författare)
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Dead or alive: sediment DNA archives as tools for tracking aquatic evolution and adaptation
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- DNA can be preserved in marine and freshwater sediments both in bulk sediment and in intact, viable resting stages. Here, we assess the potential for combined use of ancient, environmental, DNA and timeseries of resurrected long-term dormant organisms, to reconstruct trophic interactions and evolutionary adaptation to changing environments. These new methods, coupled with independent evidence of biotic and abiotic forcing factors, can provide a holistic view of past ecosystems beyond that offered by standard palaeoecology, help us assess implications of ecological and molecular change for contemporary ecosystem functioning and services, and improve our ability to predict adaptation to environmental stress. Ellegaard et al. discuss the potential for using ancient environmental DNA (eDNA), combined with resurrection ecology, to analyse trophic interactions and evolutionary adaptation to changing environments. Their Review suggests that these techniques will improve our ability to predict genetic and phenotypic adaptation to environmental stress.
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| 2. |
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| 3. |
- Kremp, A, et al.
(författare)
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Intraspecific variability in the response of bloom forming marine microalgae to changed climatic conditions
- 2012
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 2:6, s. 1195-1207
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton populations can display high levels of genetic diversity that, when reflected by phenotypic variability, may stabilize a species response to environmental changes. We studied the effects of increased temperature and CO2 availability as predicted consequences of global change, on 16 genetically different isolates of the diatom Skeletonema marinoi from the Adriatic Sea and the Skagerrak (North Sea), and on eight strains of the PST (paralytic shellfish toxin)-producing dinoflagellate Alexandrium ostenfeldii from the Baltic Sea. Maximum growth rates were estimated in batch cultures of acclimated isolates grown for five to 10 generations in a factorial design at 20 and 24°C, and present day and next century applied atmospheric pCO2, respectively. In both species, individual strains were affected in different ways by increased temperature and pCO2. The strongest response variability, buffering overall effects, was detected among Adriatic S. marinoi strains. Skagerrak strains showed a more uniform response, particularly to increased temperature, with an overall positive effect on growth. Increased temperature also caused a general growth stimulation in A. ostenfeldii, despite notable variability in strain-specific response patterns. Our data revealed a significant relationship between strain-specific growth rates and the impact of pCO2 on growth—slow growing cultures were generally positively affected, while fast growing cultures showed no or negative responses to increased pCO2. Toxin composition of A. ostenfeldii was consistently altered by elevated temperature and increased CO2 supply in the tested strains, resulting in overall promotion of saxitoxin production by both treatments. Our findings suggest that phenotypic variability within populations plays an important role in the adaptation of phytoplankton to changing environments, potentially attenuating short-term effects and forming the basis for selection. In particular, A. ostenfeldii blooms may expand and increase in toxicity under increased water temperature and atmospheric pCO2 conditions, with potentially severe consequences for the coastal ecosystem.
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| 4. |
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| 5. |
- Pinseel, E., et al.
(författare)
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Strain-specific transcriptional responses overshadow salinity effects in a marine diatom sampled along the Baltic Sea salinity cline
- 2022
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Ingår i: Isme Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370.
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Tidskriftsartikel (refereegranskat)abstract
- The salinity gradient separating marine and freshwater environments represents a major ecological divide for microbiota, yet the mechanisms by which marine microbes have adapted to and ultimately diversified in freshwater environments are poorly understood. Here, we take advantage of a natural evolutionary experiment: the colonization of the brackish Baltic Sea by the ancestrally marine diatom Skeletonema marinoi. To understand how diatoms respond to low salinity, we characterized transcriptomic responses of acclimated S. marinoi grown in a common garden. Our experiment included eight strains from source populations spanning the Baltic Sea salinity cline. Gene expression analysis revealed that low salinities induced changes in the cellular metabolism of S. marinoi, including upregulation of photosynthesis and storage compound biosynthesis, increased nutrient demand, and a complex response to oxidative stress. However, the strain effect overshadowed the salinity effect, as strains differed significantly in their response, both regarding the strength and the strategy (direction of gene expression) of their response. The high degree of intraspecific variation in gene expression observed here highlights an important but often overlooked source of biological variation associated with how diatoms respond to environmental change.
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| 6. |
- Ferrante, M. I., et al.
(författare)
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Exploring Molecular Signs of Sex in the Marine Diatom Skeletonema marinoi
- 2019
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Ingår i: Genes. - : MDPI AG. - 2073-4425. ; 10:7
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Tidskriftsartikel (refereegranskat)abstract
- Sexual reproduction plays a fundamental role in diatom life cycles. It contributes to increasing genetic diversity through meiotic recombination and also represents the phase where large-sized cells are produced to counteract the cell size reduction process that characterizes these microalgae. With the aim to identify genes linked to the sexual phase of the centric planktonic diatom Skeletonema marinoi, we carried out an RNA-seq experiment comparing the expression level of transcripts in sexualized cells with that of large cells not competent for sex. A set of genes involved in meiosis were found upregulated. Despite the fact that flagellate gametes were observed in the sample, we did not detect the expression of genes involved in the synthesis of flagella that were upregulated during sexual reproduction in another centric diatom. A comparison with the set of genes changing during the first phases of sexual reproduction of the pennate diatom Pseudo-nitzschia multistriata revealed the existence of commonalities, including the strong upregulation of genes with an unknown function that we named Sex Induced Genes (SIG). Our results further broadened the panel of genes that can be used as a marker for sexual reproduction of diatoms, crucial for the interpretation of metatranscriptomic datasets.
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| 7. |
- Leblond, J D, et al.
(författare)
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Fatty acid and sterol composition of two evolutionarily closely related dinoflagellate morphospecies from cold Scandinavian brackish and freshwaters
- 2006
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Ingår i: European Journal of Phycology. - : Informa UK Limited. - 1469-4433 .- 0967-0262. ; 41:3, s. 303-311
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the lipid composition of cold-adapted dinoflagellates. Here, we investigate Peridinium aciculiferum and Scrippsiella hangoei, two cold-adapted dinoflagellate morphospecies that present significant differences in general morphology, physiology and habitat, but which share identical ribosomal DNA (rDNA) sequences, indicating a recent evolutionary divergence between them. Despite their present taxonomic names, it is now known that these two genetically isolated morphospecies are evolutionarily related to the so-called Pfiesteria-like species. We have found that chloroplast-associated glycolipids from P. aciculiferum and S. hangoei contained a higher relative percentage of two polyunsaturated C-18 fatty acids (octadecapentaenoic [18:5(n-3)] and octadecatetraenoic [18:4(n-3)] acids), and a lower relative percentage of hexadecanoic acid (16:0) than typically observed in previously examined warm-adapted dinoflagellate species. This suggests that these two fatty acids provided the requisite membrane fluidity for chloroplasts under a cold growth condition in these two organisms. A similar increase in 18:5(n-3) and 18:4(n-3) over warm-adapted species was also found in the phospholipids and triglycerides. P. aciculiferum and S. hangoei were also examined for the production of unique sterols that may serve as chemical biomarkers. Both were found to have a very similar sterol composition, consisting of two common dinoflagellate sterols, cholestanol and dinostanol, as dominant sterols, along with a number of other common dinoflagellate sterols as minor sterols. This demonstrated the absence of a specific steroidal biomarker but, more importantly, showed that these two morphospecies still produce very similar sterols despite having diverged in several other traits.
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| 8. |
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| 9. |
- Rengefors, Karin, et al.
(författare)
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Genetic diversity and evolution in eukaryotic phytoplankton : Revelations from population genetic studies
- 2017
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 39:2, s. 165-179
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Tidskriftsartikel (refereegranskat)abstract
- Eukaryotic phytoplankton exhibit an enormous species richness, displaying a range of phylogenetic, morphological and physiological diversity. Yet, until recently, very little was known about the diversity, genetic variation and evolutionary processes within species and populations. An approach to explore this diversity and to understand evolution of phytoplankton is to use population genetics as a conceptual framework and methodology. Here, we discuss the patterns, processes and questions that population genetic studies have revealed in eukaryotic phytoplankton. First, we describe the main biological processes generating genetic variation. We specifically discuss the importance of life-cycle complexity for genetic and phenotypic diversity and consider how such diversity can be maintained during blooms when rapid asexual proliferation dominates. Next, we explore how genetic diversity is partitioned over time and space, with a focus on the processes shaping this structure, in particular selection and genetic exchange. Our aim is also to show how population genetics can be used to make inferences about realized dispersal and sexual recombination, as these processes are so difficult to study directly. Finally, we highlight important open questions and suggest promising avenues for future studies that will be made possible by new sequencing technologies.
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| 10. |
- Sefbom, Josefin, et al.
(författare)
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A planktonic diatom displays genetic structure over small spatial scales
- 2018
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 20:8, s. 2783-2795
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Tidskriftsartikel (refereegranskat)abstract
- Marine planktonic microalgae have potentially global dispersal, yet reduced gene flow has been confirmed repeatedly for several species. Over larger distances (>200 km) geographic isolation and restricted oceanographic connectivity have been recognized as instrumental in driving population divergence. Here we investigated whether similar patterns, that is, structured populations governed by geographic isolation and/or oceanographic connectivity, can be observed at smaller (6-152 km) geographic scales. To test this we established 425 clonal cultures of the planktonic diatom Skeletonema marinoi collected from 11 locations in the Archipelago Sea (northern Baltic Sea). The region is characterized by a complex topography, entailing several mixing regions of which four were included in the sampling area. Using eight microsatellite markers and conventional F-statistics, significant genetic differentiation was observed between several sites. Moreover, Bayesian cluster analysis revealed the co-occurrence of two genetic groups spread throughout the area. However, geographic isolation and oceanographic connectivity could not explain the genetic patterns observed. Our data reveal hierarchical genetic structuring whereby despite high dispersal potential, significantly diverged populations have developed over small spatial scales. Our results suggest that biological characteristics and historical events may be more important in generating barriers to gene flow than physical barriers at small spatial scales.
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| 11. |
- Sefbom, Josefin, et al.
(författare)
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Local adaptation through countergradient selection in northern populations of Skeletonema marinoi
- 2022
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Ingår i: Evolutionary Applications. - : Wiley. - 1752-4571. ; 16:2, s. 311-20
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Tidskriftsartikel (refereegranskat)abstract
- Marine microorganisms have the potential to disperse widely with few obvious barriers to gene flow. However, among microalgae, several studies have demonstrated that species can be highly genetically structured with limited gene flow among populations, despite hydrographic connectivity. Ecological differentiation and local adaptation have been suggested as drivers of such population structure. Here we tested whether multiple strains from two genetically distinct Baltic Sea populations of the diatom Skeletonema marinoi showed evidence of local adaptation to their local environments: the estuarine Bothnian Sea and the marine Kattegat Sea. We performed reciprocal transplants of multiple strains between culture media based on water from the respective environments, and we also allowed competition between strains of estuarine and marine origin in both salinities. When grown alone, both marine and estuarine strains performed best in the high-salinity environment, and estuarine strains always grew faster than marine strains. This result suggests local adaptation through countergradient selection, that is, genetic effects counteract environmental effects. However, the higher growth rate of the estuarine strains appears to have a cost in the marine environment and when strains were allowed to compete, marine strains performed better than estuarine strains in the marine environment. Thus, other traits are likely to also affect fitness. We provide evidence that tolerance to pH could be involved and that estuarine strains that are adapted to a more fluctuating pH continue growing at higher pH than marine strains.
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| 12. |
- Sjoqvist, C., et al.
(författare)
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Effects of Grazer Presence on Genetic Structure of a Phenotypically Diverse Diatom Population
- 2014
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 67:1, s. 83-95
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Tidskriftsartikel (refereegranskat)abstract
- Studies of predator-prey systems in both aquatic and terrestrial environments have shown that grazers structure the intraspecific diversity of prey species, given that the prey populations are phenotypically variable. Populations of phytoplankton have traditionally considered comprising only low intraspecific variation, hence selective grazing as a potentially structuring factor of both genetic and phenotypic diversity has not been comprehensively studied. In this study, we compared strain specific growth rates, production of polyunsaturated aldehydes, and chain length of the marine diatom Skeletonema marinoi in both grazer and non-grazer conditions by conducting monoclonal experiments. Additionally, a mesocosm experiment was performed with multiclonal experimental S. marinoi populations exposed to grazers at different levels of copepod concentration to test effects of grazer presence on diatom diversity in close to natural conditions. Our results show that distinct genotypes of a geographically restricted population exhibit variable phenotypic traits relevant to grazing interactions such as chain length and growth rates. Grazer presence affected clonal richness and evenness of multiclonal Skeletonema populations in the mesocosms, likely in conjunction with intrinsic interactions among the diatom strains. Only the production of polyunsaturated aldehydes was not affected by grazer presence. Our findings suggest that grazing can be an important factor structuring diatom population diversity in the sea and emphasize the importance of considering clonal differences when characterizing species and their role in nature.
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| 13. |
- Sjoqvist, C., et al.
(författare)
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Local adaptation and oceanographic connectivity patterns explain genetic differentiation of a marine diatom across the North Sea-Baltic Sea salinity gradient
- 2015
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 24:11, s. 2871-2885
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Tidskriftsartikel (refereegranskat)abstract
- Drivers of population genetic structure are still poorly understood in marine micro-organisms. We exploited the North Sea-Baltic Sea transition for investigating the seascape genetics of a marine diatom, Skeletonema marinoi. Eight polymorphic microsatellite loci were analysed in 354 individuals from ten locations to analyse population structure of the species along a 1500-km-long salinity gradient ranging from 3 to 30psu. To test for salinity adaptation, salinity reaction norms were determined for sets of strains originating from three different salinity regimes of the gradient. Modelled oceanographic connectivity was compared to directional relative migration by correlation analyses to examine oceanographic drivers. Population genetic analyses showed distinct genetic divergence of a low-salinity Baltic Sea population and a high-salinity North Sea population, coinciding with the most evident physical dispersal barrier in the area, the Danish Straits. Baltic Sea populations displayed reduced genetic diversity compared to North Sea populations. Growth optima of low salinity isolates were significantly lower than those of strains from higher native salinities, indicating local salinity adaptation. Although the North Sea-Baltic Sea transition was identified as a barrier to gene flow, migration between Baltic Sea and North Sea populations occurred. However, the presence of differentiated neutral markers on each side of the transition zone suggests that migrants are maladapted. It is concluded that local salinity adaptation, supported by oceanographic connectivity patterns creating an asymmetric migration pattern between the Baltic Sea and the North Sea, determines genetic differentiation patterns in the transition zone.
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