| 1. |
- Beimforde, Christina, et al.
(författare)
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Estimating the Phanerozoic history of the Ascomycota lineages: Combining fossil and molecular data
- 2014
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; :78, s. 386-398
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Tidskriftsartikel (refereegranskat)abstract
- The phylum Ascomycota is by far the largest group in the fungal kingdom. Ecologically important mutualisticassociations such as mycorrhizae and lichens have evolved in this group, which are regarded as keyinnovations that supported the evolution of land plants. Only a few attempts have been made to date theorigin of Ascomycota lineages by using molecular clock methods, which is primarily due to the lack ofsatisfactory fossil calibration data. For this reason we have evaluated all of the oldest available ascomycetefossils from amber (Albian to Miocene) and chert (Devonian and Maastrichtian). The fossils representfive major ascomycete classes (Coniocybomycetes, Dothideomycetes, Eurotiomycetes, Laboulbeniomycetes,and Lecanoromycetes). We have assembled a multi-gene data set (18SrDNA, 28SrDNA, RPB1 andRPB2) from a total of 145 taxa representing most groups of the Ascomycota and utilized fossil calibrationpoints solely from within the ascomycetes to estimate divergence times of Ascomycota lineages with aBayesian approach. Our results suggest an initial diversification of the Pezizomycotina in the Ordovician,followed by repeated splits of lineages throughout the Phanerozoic, and indicate that this continuousdiversification was unaffected by mass extinctions. We suggest that the ecological diversity within eachlineage ensured that at least some taxa of each group were able to survive global crises and rapidlyrecovered.
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| 2. |
- Friesenbichler, Evelyn, et al.
(författare)
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Sponge-microbial build-ups from the lowermost Triassic Chanakhchi section in southern Armenia: Microfacies and stable carbon isotopes
- 2018
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 490, s. 653-672
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Tidskriftsartikel (refereegranskat)abstract
- The end-Permian mass extinction was the most severe biotic crisis in Earth's history. In its direct aftermathmicrobial communities colonized some of the space left vacant after the severe decline of skeletal metazoans.The Permian-Triassic boundary microbialites were peculiarly abundant on low-latitude shallow-marine carbonateshelves of central Tethyan continents. Armenia features particularly well preserved and diverse basalTriassic sponge-microbial build-ups (BTSMBs), which were not studied in detail to date. Here, the Chanakhchisection in southern Armenia is described petrographically and by means of stable isotope analyses. TheArmenian BTSMBs formed in a distally open marine setting on a pelagic carbonate ramp in the course of twophases of microbial growth during the Induan (Lower Triassic). The BTSMBs are represented by predominantlythrombolitic but also dendrolitic and digitate stromatolite biostromes and mounds that vary in height between5 cm to 12 m. The digitate stromatolites are associated with calcium carbonate crystal fans (CCFs). Microfaciesanalyses revealed that the BTSMBs exhibit a number of different growth forms and internal fabrics. The formationof CCFs was apparently not devoid of biological influence and took place above the sediment surface. Theabundance of sponges in the BTSMBs reveals that ecologically complex metazoan-microbial reefs have beenpresent already early after the end-Permian mass extinction. However, the formation of biostromes and moundsdid not depend on sponges or other metazoans. BTSMBs that formed during the second microbial growth phaserevealed similar δ13C-values like the surrounding sediment. In contrast, the δ13Cmicrobialite and δ13Csediment valuesfrom the BTSMBs and CCFs of the first growth phase show a difference of up to +2.3‰, suggesting a significantinfluence of photoautotrophy during microbially induced carbonate precipitation.
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| 3. |
- Heindel, Katrin, et al.
(författare)
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The formation of microbial-metazoan bioherms and biostromes following the latest Permian mass extinction
- 2018
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Ingår i: Gondwana Research. - : Elsevier BV. - 1342-937X. ; 61, s. 187-202
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Tidskriftsartikel (refereegranskat)abstract
- After the latest Permian mass extinction event, microbial mats filled the ecological niche previously occupied by metazoan reefs, resulting in widespread microbialites. This study focuses on the lipid biomarker (molecular fossil) and invertebrate fossil records from Neotethyan platform margin sections to understand microbial-metazoan bioherm formation. Here, we find that early Griesbachian thrombolitic and stromatolitic microbialites from Çürük Dag (Turkey) and Kuh e Surmeh (Iran) contain abundant lipid biomarkers, representing input from cyanobacteria, anoxygenic phototrophic bacteria, sulfate-reducing bacteria, and halophilic archaea. The biomarker inventory suggests that the microbialites were constructed by cyanobacteria-dominated microbial mats. Biomarkers of halophilic archaea are interpreted to reflect input from the water column, suggesting that the Neotethys experienced at least episodically hypersaline conditions. We also demonstrate that bacteria, possible keratose sponges (up to 50% of the carbonate is represented by the possible sponges), and microconchids lived synergistically to form microbial-metazoan bioherms in the immediate aftermath of the extinction along the western margin of the Neotethys. Abundant fossils of oxygen-dependent invertebrates (i.e. microconchids, bivalves, gastropods, brachiopods, and ostracods) and foraminifers were also found within these bioherms. The presence of invertebrates in conjunction with abundant molecular fossils of cyanobacteria indicates an oxygenated water column. Even though the presence of the biomarker isorenieratane in microbialites may considered as evidence for euxinic conditions in the water column, its absence in the background sediments rather points to a source organism belonging to the mat community. The new finding of bioherms built in part by metazoans suggests that reef ecosystems underwent a major turnover across the extinction event, and shortens the ‘metazoan reef gap’ to just the uppermost Changhsingian. During the Early Triassic, therefore, reefal ecosystems were able to recover in oxygenated settings since the earliest Griesbachian, albeit in an impoverished state.
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| 4. |
- Leefman, Tim, et al.
(författare)
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An Imaging Mass Spectrometry Study on the Formation of Conditioning Films and Biofilms in the Subsurface (Äspö Hard Rock Laboratory, SE Sweden)
- 2015
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 32:3-4, s. 197-206
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Tidskriftsartikel (refereegranskat)abstract
- Conditioning films and biofilms forming on surfaces of solid materials exposed to aqueous media play a key role in in the interaction between the geo- and biospheres. In this study, time-of-flight secondary ion mass spectrometry and scanning electron microscopy were used to investigate the time scale, mode of formation, and chemistry of conditioning films and biofilms that formed on Si substrates exposed to aquifer water in the subsurface Äspö Hard Rock Laboratory, SE-Sweden. The detection of fragment ions of amino acids, carbohydrates, and carboxylic acids revealed that different types of organic compounds had adhered to the Si surface already after 10 min of exposure to the aquifer fluids, whereas the attachment of microbial cells was first observed after 1000 min. The organic compounds first formed isolated μm-sized accumulations and subsequently started to distribute on the wafer surface more homogenously. Simultaneously further microorganisms attached to the surface and formed biofilm-like cell accumulations after 3 months of exposure to aquifer water.
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| 5. |
- Luo, Cui, et al.
(författare)
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Identification and Current Palaeobiological Understanding of “Keratosa”-Type Nonspicular Demosponge Fossils in Carbonates : With a New Example from the Lowermost Triassic, Armenia
- 2022
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Ingår i: Life. - : MDPI AG. - 0024-3019 .- 2075-1729. ; 12:9
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Tidskriftsartikel (refereegranskat)abstract
- Structures similar to fossilized nonspicular demosponges have been reported in carbonates throughout the Phanerozoic and recently in rocks dating back to 890 Ma ago. Interpretation of these records is increasingly influential to our understanding of metazoans in multiple aspects, including their early evolution, the ecology in fossil reefs, and recovery after mass extinction events. Here, we propose six identification criteria of “Keratosa”-type nonspicular demosponge fossils based on the well-established taphonomical models and their biological characteristics. Besides, sponge fossils of this kind from the lowermost Triassic of Chanakhchi (Armenia) are described with a 3-D reconstruction to exemplify the application of these criteria in recognition of such organisms. Subsequently, the state-of-the-art understanding of the taxonomy and evolution of these fossil sponges, a previously poorly addressed topic, is summarized. The morphology of the Triassic Chanakhchi fossils indicates an affinity with verongimorphs, a group that may have evolved by Cambrian Age 3. Other than that, further efforts are encouraged to forge quantitative criteria based on the here proposed descriptive version and to explore the taxonomic diversity and evolutionary details of these fossil nonspicular demosponges.
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| 6. |
- Reitner, Joachim, et al.
(författare)
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Fungi in subterranean environments
- 2006
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Ingår i: G.M Gadd (ed), Fungi in biogenchemical cycles.. - Cambridge : Cambridge University Press. ; , s. 788-1002
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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