SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "AMNE:(NATURVETENSKAP Biologiska vetenskaper) "

Sökning: AMNE:(NATURVETENSKAP Biologiska vetenskaper)

Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Caputo, Andrea, 1988- (författare)
  • Genomic and morphological diversity of marine planktonic diatom-diazotroph associations : a continuum of integration and diversification through geological time
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Symbioses between eukaryotes and nitrogen (N2)-fixing cyanobacteria (or diazotrophs) are quite common in the plankton community. A few genera of diatoms (Bacillariophyceae) such as Rhizosolenia, Hemiaulus and Chaetoceros are well known to form symbioses with the heterocystous diazotrophic cyanobacteria Richelia intracellularis and Calothrix rhizosoleniae. The latter are also called diatom-diazotroph associations, or DDAs. Up to now, the prokaryotic partners have been morphologically and genetically characterized, and the phylogenetic reconstruction of the well conserved nifH gene (encodes for the nitrogenase enzyme) placed the symbionts in 3 clusters based on their host-specificity, i.e. het-1 (Rhizosolenia-R. intracellularis), het-2 (Hemiaulus-R. intracellularis), and het-3 (Chaetoceros-C- rhizosoleniae). Conversely, the diatom-hosts, major representative of the phytoplankton community and crucial contributors to the carbon (C) biogeochemical cycle, have been understudied.The first aim of this thesis was to genetically and morphologically characterize the diatom-hosts, and to reconstruct the evolutionary background of the partnerships and the symbiont integration in the host. The molecular-clock analysis reconstruction showed the ancient appearance of the DDAs, and the traits characterizing the ancestors. In addition, diatom-hosts bearing internal symbionts (with more eroded draft genomes) appeared earlier than diatom-hosts with external symbionts. Finally a blast survey highlighted a broader distribution of the DDAs than expected.The second aim of this thesis was to compare genetic and physiological characteristics of the DDAs symbionts with the other eukaryote-diazotroph symbiosis, i.e. prymnesiophyte-UCYN-A (or Candidatus Atelocyanobacterium thalassa). The genome comparison highlighted more genes for transporters in het-3 (external symbiont) and in the UCYN-A based symbiosis, suggesting that symbiont location might be relevant also for metabolic exchanges and interactions with the host and/or environment. Moreover, a summary of methodological biases that brought to an underestimation of the DDAs is reported.The third aim of this thesis was to determine the distribution of the DDAs in the South Pacific Ocean using a quantitative polymerase chain reaction (qPCR) approach and to outline the environmental drivers of such distribution. Among the het-groups, het-1 was the most abundant/detected and co-occurred with the other 2 symbiotic strains, all responding similarly to the influence of abiotic factors, such as temperature and salinity (positive and negative correlation, respectively). Globally, Trichodesmium dominated the qPCR detections, followed by UCYN-B. UCYN-A phylotypes (A-1, A-2) were detected without their proposed hosts, for which new oligonucleotides were designed. The latter suggested a facultative symbiosis. Finally, microscopy observations of the het-groups highlighted a discrepancy with the qPCR counts (i.e. the former were several order of magnitudes lower), leading to the idea of developing a new approach to quantify the DDAs.  The fourth aim of this thesis was to develop highly specific in situ hybridization assays (CARD-FISH) to determine the presence of alternative life-stages and/or free-living partners. The new assays were applied to samples collected in the South China Sea and compared with abundance estimates from qPCR assays for the 3 symbiotic strains. Free-living cells were indeed detected along the transect, mainly at deeper depths. Free-living symbionts had two morphotypes: trichomes and single-cells. The latter were interpreted as temporary life-stages. Consistent co-occurrence of the 3 het-groups was also found in the SCS and application of a SEM model predicted positive interactions between the het groups. We interpreted the positive interaction as absence of intra-specific competition, and consistent with the previous study, temperature and salinity were predicted as major drivers of the DDAs distribution.
  •  
2.
  •  
3.
  • Pontiller, Benjamin, 1985- (författare)
  • Molecular mechanisms involved in prokaryotic cycling of labile dissolved organic matter in the sea
  • 2021
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Roughly half of the global primary production originates from microscopic phytoplankton in marine ecosystems, converting carbon dioxide into organic matter. This organic matter pool consists of a myriad of compounds that fuel heterotrophic bacterioplankton. However, knowledge of the molecular mechanisms – particularly the metabolic pathways involved in the degradation and utilization of dissolved organic matter (DOM) – and transcriptional dynamics over spatiotemporal gradients are still scarce. Therefore, we studied the molecular mechanisms of bacterioplankton communities, including archaea, involved in the cycling of DOM, over different spatiotemporal scales in experiments and through field observations.In seawater experiments, we found a divergence of bacterioplankton transcriptional responses to different organic matter compound classes (carbohydrates, nucleic acids, and proteins) and condensation states (monomers or polymers). These responses were associated with distinct bacterial taxa, suggesting pronounced functional partitioning of these compounds in the Sea. Baltic Proper mesocosms amended with two different river loadings (forest versus agriculture river water) revealed a divergence in gene expression patterns between treatments during bloom decay. This was particularly true for genes in phosphorus and nitrogen metabolism, highlighting the importance and sensitivity of interaction effects between river- and phytoplankton-derived DOM in regulating bacterial activity responses to changes in precipitation-induced riverine runoff.In shipboard mesocosms in an Atlantic coastal upwelling system, we found significant changes in bacterioplankton transcription of hydrolyzing enzymes and membrane transporters from phytoplankton bloom development to senescence, primarily driven by phytoplankton-derived DOM and dissolved organic carbon dynamics. These responses differed substantially between bacterial orders, suggesting that functional resource partitioning is dynamically structured by temporal changes in DOM quantity and quality. Further analysis of these gene systems in a stratified fjord revealed pronounced divergence in transcription with depth and between bacterial taxa; moreover, transcription was more variable in the surface waters. This highlights the interplay between functional and physical partitioning of biogeochemical cycles. Collectively, the findings in this thesis contribute novel insights into the interdependency between prokaryotes and DOM by shedding light on the mechanisms involved in DOM cycling over ecologically relevant spatiotemporal scales.
  •  
4.
  •  
5.
  • Hoffsten, Per-Ola (författare)
  • Galvån : Ett riksintresseområde för naturvården, X 105
  • 1992
  • Rapport (övrigt vetenskapligt)abstract
    • RiksintressetRikedom av forsar och strömmar i kombination med vattendragets storlek utgör en ovanlig och därför värdefull miljö.Området utgör även en värdefull biotop för sårbart djurliv bl. a utter, nedströmsvandrande insjööring.Översvämningsbetingade våtmarksmiljöer med rik flora, bl. a Kung Karls spira, intressant strandflora invid sidofåror, samt en unik svampflora invid biflödet Nybobäcken.
  •  
6.
  • Hurtado, P., et al. (författare)
  • Disentangling functional trait variation and covariation in epiphytic lichens along a continent-wide latitudinal gradient
  • 2020
  • Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : ROYAL SOC. - 0962-8452 .- 1471-2954. ; 287:1922
  • Tidskriftsartikel (refereegranskat)abstract
    • Characterizing functional trait variation and covariation, and its drivers, is critical to understand the response of species to changing environmental conditions. Evolutionary and environmental factors determine how traits vary among and within species at multiple scales. However, disentangling their relative contribution is challenging and a comprehensive trait-environment framework addressing such questions is missing in lichens. We investigated the variation in nine traits related to photosynthetic performance, water use and nutrient acquisition applying phylogenetic comparative analyses in lichen epiphytic communities on beech across Europe. These poikilohydric organisms offer a valuable model owing to their inherent limitations to buffer contrasting environmental conditions. Photobiont type and growth form captured differences in certain physiological traits whose variation was largely determined by evolutionary processes (i.e. phylogenetic history), although the intraspecific component was non-negligible. Seasonal temperature fluctuations also had an impact on trait variation, while nitrogen content depended on photobiont type rather than nitrogen deposition. The inconsistency of trait covariation among and within species prevented establishing major resource use strategies in lichens. However, we did identify a general pattern related to the water-use strategy. Thus, to robustly unveil lichen responses under different climatic scenarios, it is necessary to incorporate both among and within-species trait variation and covariation.
  •  
7.
  • Janson, S., et al. (författare)
  • Population genetic structure of crucian carp (Carassius carassius) in man-made ponds and wild populations in Sweden
  • 2015
  • Ingår i: Aquaculture International. - 0967-6120 .- 1573-143X. ; 23:1, s. 359-368
  • Tidskriftsartikel (refereegranskat)abstract
    • Although once popular prior to the last century, the aquaculture of crucian carp Carassius carassius (L. 1758) in Sweden gradually fell from favour. This is the first genetic comparison of crucian carp from historic man-made ponds in the Scandinavian Peninsula. The aim was to identify old populations without admixture and to compare the relationship of pond populations from different provinces in Sweden. In total, nine microsatellite loci from 234 individuals from 20 locations in varied parts of Sweden were analysed. The genetic distances of crucian carp populations indicated that the populations in the southernmost province of Sweden, Scania, shared a common history. A pond population in the province SmAyenland also showed a common inheritance with this group. In the province Uppland, further north in Sweden, the population genetic distances suggested a much more complex history of crucian carp distributions in the ponds. The data showed that there are some ponds with potentially old populations without admixture, but also that several ponds might have been stocked with fish from many sources.
  •  
8.
  • Koch, Kamilla, et al. (författare)
  • Morphological differences in the ovary of Libellulidae (Odonata)
  • 2009
  • Ingår i: International Journal of Odonatology. - Oxford : Taylor & Francis. - 1388-7890. ; 12:1, s. 147-156
  • Tidskriftsartikel (refereegranskat)abstract
    • All female Odonata have been assumed to produce oocytes continuously during their mature life span. However, a recent study of ovariole orientation and development led to the suggestion that Libellulidae are divided into two groups of species, one with continuous, the other with stepwise oocyte production. To find more evidence of this division, we compared the size variation and growth within the vitellarium of the ovary, studying oocytes, and follicle cells. We found that morphological characters discriminate between the two ovary types in eight of the 10 investigated species. In both types we found an increase in all measurements from the anterior to the posterior end of the vitellarium. The increase in oocyte width and follicle cell length was significantly higher in species with a continuous oocyte production. We also noted that follicle cells may have more than one nucleus and that their number can vary during vitellogenesis. Our study confirmed the hypotheses that two different ovary types exist in Libellulidae. The two species not fitting into this grouping could be an artefact of small samp le size due to intraspecific phenotypic plasticity, or else there might be more than two ovary groups, or even a continuum. We could not offer an explanation as to how the process of stepwise oocyte production differs from continuous based production on morphological characters.
  •  
9.
  • Lindström, Kai, et al. (författare)
  • Sperm adaptation in relation to salinity in three goby species
  • 2021
  • Ingår i: Journal of Fish Biology. - 0022-1112 .- 1095-8649.
  • Tidskriftsartikel (refereegranskat)abstract
    • In externally fertilizing species, the gametes of both males and females are exposed to the influences of the environment into which they are released. Sperm are sensitive to abiotic factors such as salinity, but they are also affected by biotic factors such as sperm competition. In this study, the authors compared the performance of sperm of three goby species, the painted goby, Pomatoschistus pictus, the two-spotted goby, Pomatoschistus flavescens, and the sand goby, Pomatoschistus minutus. These species differ in their distributions, with painted goby having the narrowest salinity range and sand goby the widest. Moreover, data from paternity show that the two-spotted goby experiences the least sperm competition, whereas in the sand goby sperm competition is ubiquitous. The authors took sperm samples from dissected males and exposed them to high salinity water (31 PSU) representing the North Sea and low salinity water (6 PSU) representing the brackish Baltic Sea Proper. They then used computer-assisted sperm analysis to measure the proportion of motile sperm and sperm swimming speed 10 min and 20 h after sperm activation. The authors found that sperm performance depended on salinity, but there seemed to be no relationship to the species' geographical distribution in relation to salinity range. The species differed in the proportion of motile sperm, but there was no significant decrease in sperm motility during 20 h. The sand goby was the only species with motile sperm after 72 h.
  •  
10.
  • Spagopoulou, Foteini, et al. (författare)
  • Shifts in Reproductive Investment in Response to Competitors Lower Male Reproductive Success
  • 2020
  • Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 196:3, s. 355-368
  • Tidskriftsartikel (refereegranskat)abstract
    • In many species, males exhibit phenotypic plasticity in sexually selected traits when exposed to social cues about the intensity of sexual competition. To date, however, few studies have tested how this plasticity affects male reproductive success. We initially tested whether male mosquitofish,Gambusia holbrooki(Poeciliidae), change their investment in traits under pre- and postcopulatory sexual selection depending on the social environment. For a full spermatogenesis cycle, focal males were exposed to visual and chemical cues of rivals that were either present (competitive treatment) or absent (control). Males from the competitive treatment had significantly slower-swimming sperm but did not differ in sperm count from control males. When two males competed for a female, competitive treatment males also made significantly fewer copulation attempts and courtship displays than control males. Further, paternity analysis of 708 offspring from 148 potential sires, testing whether these changes in reproductive traits affected male reproductive success, showed that males previously exposed to cues about the presence of rivals sired significantly fewer offspring when competing with a control male. We discuss several possible explanations for these unusual findings.
  •  
Skapa referenser, mejla, bekava och länka
Typ av publikation
tidskriftsartikel (24705)
doktorsavhandling (3180)
annan publikation (1963)
konferensbidrag (1184)
forskningsöversikt (1085)
bokkapitel (909)
visa fler...
rapport (468)
samlingsverk (redaktörskap) (449)
bok (211)
licentiatavhandling (184)
recension (61)
proceedings (redaktörskap) (22)
patent (16)
konstnärligt arbete (8)
visa färre...
Typ av innehåll
refereegranskat (25772)
övrigt vetenskapligt (7962)
populärvet., debatt m.m. (668)
Författare/redaktör
Uhlen, Mathias (321)
Dalen, Love (179)
Langel, Ülo (174)
Ellegren, Hans (173)
Elmberg, Johan, 1960 ... (170)
Olsen, Björn (127)
visa fler...
Ericson, Per G P, 19 ... (121)
Bertilsson, Stefan (120)
von Heijne, Gunnar (120)
Ehrlén, Johan (119)
Lundeberg, Joakim (116)
Angerbjörn, Anders (116)
Ågren, Jon (115)
Björklund, Mats (114)
Werdelin, Lars (113)
Nilsson Ekdahl, Kris ... (110)
Elmberg, Johan (110)
Jonsson, Bengt Gunna ... (110)
Greenberg, Larry (110)
Nilsson, Mats (108)
Söderhäll, Kenneth (108)
Granéli, Edna (106)
Andersson, Leif (106)
Hedenäs, Lars (106)
Jakobsson, Mattias (103)
Mannervik, Bengt (102)
Lascoux, Martin (102)
Karlsson, Thomas (100)
Lammi, Mikko, 1961- (100)
Waldenström, Jonas (99)
Kolm, Niclas (98)
Laurila, Anssi (96)
Lindahl, Erik (92)
Nilsson, Christer (91)
Hylander, Kristoffer (87)
Lindblad, Peter (87)
Thulin, Mats (87)
Nilsson, Peter (86)
Nilsson, Bo (86)
Los, Marek Jan (86)
Qvarnström, Anna (86)
Berglund, Anders (85)
Uhlen, M (85)
Cousins, Sara A. O. (84)
Pinhassi, Jarone (82)
Wiklund, Christer (82)
Schmitz, Monika (81)
Arnqvist, Göran (81)
Lundberg, Emma (80)
Åqvist, Johan (80)
visa färre...
Lärosäte
Uppsala universitet (11712)
Stockholms universitet (8684)
Umeå universitet (4479)
Kungliga Tekniska Högskolan (2891)
Linnéuniversitetet (1852)
Linköpings universitet (1683)
visa fler...
Karolinska Institutet (1373)
Naturhistoriska riksmuseet (1273)
Sveriges Lantbruksuniversitet (1179)
Karlstads universitet (955)
Örebro universitet (934)
Södertörns högskola (763)
Lunds universitet (612)
Mittuniversitetet (572)
Högskolan Kristianstad (499)
Göteborgs universitet (496)
Högskolan i Skövde (246)
Högskolan i Gävle (150)
Naturvårdsverket (146)
Högskolan i Halmstad (134)
Chalmers tekniska högskola (101)
Jönköping University (94)
Malmö universitet (87)
Luleå tekniska universitet (85)
RISE (71)
Högskolan i Borås (63)
Högskolan Dalarna (54)
Mälardalens högskola (49)
Gymnastik- och idrottshögskolan (33)
VTI - Statens väg- och transportforskningsinstitut (13)
Ersta Sköndal Bräcke högskola (9)
Högskolan Väst (4)
Försvarshögskolan (4)
Riksantikvarieämbetet (2)
Röda Korsets Högskola (2)
Nordiska Afrikainstitutet (1)
Blekinge Tekniska Högskola (1)
visa färre...
Språk
Engelska (32803)
Svenska (1484)
Tyska (71)
Franska (14)
Ryska (13)
Spanska (10)
visa fler...
Finska (10)
Arabiska (6)
Danska (5)
Norska (4)
Portugisiska (4)
Nederländska (3)
Polska (2)
Kinesiska (2)
Italienska (1)
Isländska (1)
Estniska (1)
Japanska (1)
Turkiska (1)
Vietnamesiska (1)
visa färre...
Forskningsämne (UKÄ/SCB)
Naturvetenskap (34398)
Medicin och hälsovetenskap (2479)
Lantbruksvetenskap (978)
Teknik (508)
Samhällsvetenskap (426)
Humaniora (263)

År

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy