Swedish Museum of Natural History
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Phanerozoic atmospheric CO2 reconstructed with proxies and models: Current understanding and future directions
No full textKnowledge of paleo-atmospheric CO2 is critical to understanding how Earth System processes respond to a full range of CO2 concentrations, both past and future. This review addresses the terrestrial and marine proxies used to estimate paleo-CO2 concentrations and how the biological and/or geochemical properties of each proxy encodes the ambient CO2 signal, as well as the associated assumptions and uncertainties of the CO2 estimates. The Phanerozoic history of atmospheric CO2 is discussed, highlighting a new high-fidelity Cenozoic CO2 curve and its implications. Subsequently, pre-Cenozoic CO2 as is currently understood is outlined, in the context of its temporal relationship to climate and evolutionary changes. An overview of carbon cycle modeling for estimating paleo-CO2 is presented, including the key principles, models, and updates in the field, as well as the key emerging patterns and planned next steps. The review concludes by addressing next steps in advancing the science of CO2 reconstruction and for improving our understanding of the evolution of atmospheric CO2 over the past half-billion years
Paleoenvironmental implications of Deccan volcanism relative to the Cretaceous-Paleogene (K-Pg) mass extinction: evidence from the ‘red bole’ record
No full textLarge Igneous Provinces (LIPs) have been widely investigated for their potential role in mass extinction events. High-precision U-Pb zircon geochronology of the Deccan Traps indicates that peak eruptive activity began approximately 250 kyr before the Cretaceous-Paleogene (K-Pg) boundary and persisted into the early Danian, suggesting a causal link between Deccan volcanism and the K-Pg mass extinction. Within the Deccan stratigraphy, intra-volcanic weathered horizons known as red boles represent intervals of volcanic quiescence and serve as critical archives of paleoenvironmental conditions during the Deccan Traps emplacement. These red boles have been studied using a suite of geochemical proxies including major element composition, bulk rock and clay mineralogy, weathering indices, paleo-precipitation estimates, and stable isotope analyses to assess climatic and environmental changes induced by volcanism. Our multiproxy geochemical analysis of 26 red bole sections across the Deccan stratigraphy reveals that they are enriched in immobile elements such as Al and Fe3+. The clay fraction is dominated by smectite, suggesting semi-arid conditions with fluctuating moisture availability rather than persistent monsoonal climate. Weathering indices indicate progressive chemical weathering, likely exacerbated by acid rain associated with increasing volcanic emissions. Stable hydrogen and oxygen isotope compositions further suggest episodes of hydroclimatic instability that intensified alongside peak Deccan eruption rates, particularly near the K-Pg boundary. These findings reinforce the hypothesis that Deccan volcanism played a significant role in shaping Late Cretaceous climate variability and contributed to the environmental stresses leading up to the K-Pg mass extinction
Phylogeny of Palicoureeae (Rubiaceae) based on 353 low-copy nuclear genes – with particular focus on Hymenocoleus Robbr.
No full textMembers of the tribe Palicoureeae of the coffee family (Rubiaceae) have a complex taxonomic history and have been the focus of few modern systematic studies. The tribe comprises about 1,100 tropical species in ten genera. To investigate phylogeny, we used a target capture approach and the angiosperm-wide Angiosperms353 bait set to produce genomic data for a representative taxon sample of Palicoureeae, with particular focus on the African genus Hymenocoleus. Using coalescent-based inference methods, we find that Puffia gerrardii (recently separated from Geophila) is sister to Hymenocoleus. The deepest split in Hymenocoleus is highly affected by incomplete lineage sorting, possibly as a consequence of rapid speciation during the early evolution of the clade. Remaining interspecific relationships in Hymenocoleus could be confidently resolved and while Robbrecht’s traditional infrageneric classification scheme based on floral features is not supported as reflecting evolution in the group, we find that several other features do, e.g. characters of pyrenes and involucral cups. Although not free of challenges, a strong advantage with our analytical approach is that gene tree heterogeneity can be taken into account. Including flanking regions yielded data sets that had the strongest power to reject polytomies and produced less gene tree error, resulting in species trees with higher normalised quartet scores and higher average support compared to trees inferred only from exon data. Presumably paralogous loci are often filtered out prior to species tree estimation but we find that they may contribute important phylogenetic information when using an inference method that actively accounts for them
In-Situ Organic and Inorganic TOF-SIMS Mapping Reveals Biomarker Preservation in Carbonate Rather Than Phosphate Minerals
No full textHere we have applied ToF-SIMS and Raman microspectroscopy to a phosphatic coprolite (fossilised faecal matter) preserved within an iron carbonate concretion from the Mazon Creek lagerstätte (306 Ma), of which the biomarker composition has been previously characterised using GC-MS. Abundant cholesteroid biomarkers were determined to represent dietary input from animals. This study aimed to spatially resolve these cholesteroid biomarkers within the coprolite specimen. The steroid 5a,14a,17a(H) 20R cholestane was targeted for secondary ion mapping due to its abundance in the GC-MS analyses of the fossil (Tripp et al., 2022). The sterane biomarker was shown to be intimately associated with locally precipitated iron carbonate and some minor amounts of pyrite, and not associated with the phosphatised tissues. Importantly, phosphatisation is often associated with three-dimensional soft tissue preservation during earliest diagenesis, yet here does not show association with endogenous lipid biomarkers. This suggests that the factors facilitating lipid preservation in geological samples may differ to those controlling soft tissue fossilisation
Nanoparticles of iridium and other platinum group elements identified in Chicxulub asteroid impact spherules – Implications for impact winter and profound climate change
No full textThe Chicxulub asteroid that ended the Cretaceous Era ∼66.05 million years ago caused a prolonged time of global darkness – the impact winter – leading to mass extinctions. Elements from the asteroid, including the platinum group elements (PGEs) osmium, iridium and platinum are known from the globally distributed boundary clay but their carrier elements have so far been unknown. We identify, for the first time in detail, the presence of these PGEs within Chicxulub impact spherules and importantly, we identify their carrier elements. We show through synchrotron Nano-XRF how these PGEs occur in nanostructures as un-ordered cube- and/or needle-like crystals co-localizing with both siderophile and chalcophile elements including Co, Ni, Cu, Zn, and Pb, derived from the asteroid. These crystals are set within a matrix of iron-rich calcium and silica glass revealing the mix of vaporized target rock and the asteroid. The results provide insights into the combination of elements present in the spherules, indicating formation of new minerals. We argue that the nano-shards of unreactive elements such as platinum, iridium and copper acted as nuclei for aerosol formation and potentially contributed to a prolonged impact winter with darkness and cooling leading to a profound and long-term climate change.This work was supported by Swedish Research Council, Sweden, grants VR 2019-4061 (V·V.); and Knut and Alice Wallenberg Foundation, Sweden, grant KAW 2020.0145 (V·V.), and Wenner-Gren Foundation SSh2023-0016, Sweden (V·V.). We thank beamline scientists and staff at MAX IV synchrotron facility. We acknowledge MAX IV Laboratory for time on Beamline NanoMAX under Proposal 20190340 and Beamline Balder, Sweden, under Proposal 20210384. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research council, Sweden under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and Formas, Sweden, under contract 2019-02496. XRM data acquisition was supported by a grant to the Stockholm University Brain Imaging Centre, Sweden (SU FV-5.1.2-1035-15).</p
The progressive evolution of cold-adapted species
No full textThe evolution of cold-adapted terrestrial species underwent two main phases. First, the genera of cold-adapted taxa appeared during the Late Pliocene to Early Pleistocene. The modern day and Late Pleistocene cold-adapted species then arose during and after the Middle Pleistocene Transition. These species evolved through one or more of the following processes: out of the temperate zone, evolving in situ, or through montane preadaptation. Palaeogenetic studies are greatly contributing to our understanding of the timings and modes of evolution of cold-adapted species as well as when their specialised traits evolved. The evolution of polar plant and beetle species is claimed to show greater stasis than that of vertebrates, but could instead reflect morphological conservatism that can be tested with palaeogenetics
Balancing selection of climate adaptive loci underlies the success of introduction of Eurasian Tree Sparrows
No full textHuman-mediated introductions have enabled species to colonize beyond their native ranges, yet the mechanisms underlying successful establishment remain unclear. We combined genomic and ecological analyses to investigate parallel introductions of the Eurasian Tree Sparrow across continents. Our analyses of genetic structure and demography revealed that introduced populations in North America (European origin) and Australia (Chinese origin) experienced founder effects, with resulting bottlenecks, reduced genetic diversity, and increased inbreeding.Despite the genome-wide loss of diversity, we identified conserved regions of high genetic variation in the introduced populations, potentially maintained through balancing selection of ancestral polymorphisms. Genotype-climate association and genetic offset modeling demonstrated that climate-adaptivegenetic variants retained similar frequencies across the native and introduced ranges, likely maintaining similar interactions of genetic components with climate niches. Our findings highlight how retention of adaptive polymorphism facilitates establishment success in the introduced populations, providing a framework for predicting invasion potential through genomic signatures of adaptation
A parasite through time: Revisiting Trypanosoma rajae Laveran and Mesnil, 1902 with new molecular and morphological insights from the blood of Rajidae in the western Mediterranean
No full textTrypanosomes are blood parasitic protozoa infecting Chordates, including the elasmobranch skates (Rajidae). Amongst, Trypanosoma rajae Laveran and Mesnil, 1902 is a century old parasite, first briefly described from the Mediterranean starry ray Raja asterias and the undulate ray R. undulata off Roscoff, France, Northeast Atlantic, for which illustrations and molecular data are still lacking. Herein, we investigate blood trypanosomes of R. asterias, type-host of T. rajae and of those from the blood of the brown ray R. miraletus, collected off the Algerian coast, Western Mediterranean. We describe these trypanosomes using an integrative taxonomic approach combining morphological characters and partial 18S rRNA gene sequencing, and we provide several morphological, morphometrical, anatomical and biological characteristics (division stages). Specific characteristics of Trypanosoma ex R. asterias such as granulations of the nucleus and cytoplasm; shape of the kinetoplast, nucleus and body; tip of the body; the undulating membrane, as well as the morphometric measurements were within the ranges given in the previous records of T. rajae, and we ascribe thus the newly collected trypanosomes from R. asterias to T. rajae. Algeria and the Western Mediterranean are new locality records for T. rajae. Trypanosomes ex R. miraletus differed from T. rajae ex R. asterias by some morphometrical data: posterior end to kinetoplast (PK), free flagellum length (FF), the kinetoplast index (KI), slenderness (Sle), flagellar index (FI), midnucleus to anterior end (NA) and parasite maximum body width at nucleus (BWN). Partial 18S rRNA gene sequences of T. rajae ex R. asterias and Trypanosoma sp. ex R. miraletus showed ~99.76 % similarity. We take a conservative position and refer to trypanosomes from R. miraletus as T. cf. rajae. Phylogenetic analysis using 18S rRNA gene sequences of other aquatic trypanosomes allowed positioning of T. rajae relative to the other trypanosome species, previously described, infecting marine and freshwater hosts worldwide. Some divisional stages were also observed on MGG-stained thin smears allowing a brief description of the division of this trypanosome in the blood of its host. This effort is the first study of T. rajae using integrative taxonomy combining morphology and DNA and we provide for the first time observations of dividing stages of this species in the host bloo
Morphological and molecular (cox1, 28S rRNA) data of Microcotyle erythrini Van Beneden &amp; Hesse, 1863 sensu stricto (Polyopisthocotyla, Microcotylidae) infecting the gill lamellae of a marine sparid fish in the Western Mediterranean
No full textThe polyopisthocotylan Microcotyle erythrini was first described from the common pandora (Pagellus erythrinus) collected off Brest, Northeast Atlantic, and subsequently recorded from various sparid hosts across the Mediterranean. Recent studies combining morphometric and molecular data resolved this complex into distinct species, including M. isyebi from Boops boops and M. whittingtoni from Dentex dentex. Here, we investigate Microcotyle from Pagrus pagrus off Tunisia (Western Mediterranean), combining morphological and molecular barcodes (28S rRNA and cox1). The cox1 sequence divergence between Microcotyle from P. pagrus off Tunisia and M. erythrini sensu stricto from P. erythrinus in the Mediterranean was 0-3 %, suggesting the presence of a single species. Newly generated cox1 sequences clustered with high support within the M. erythrini sensu stricto clade reported from P. erythrinus in France and Spain and P. pagrus in Spain and Algeria. Phylogenetic analyses based on partial 28S rDNA sequences corroborated this, as the newly generated 28S sequences of M. erythrini from P. pagrus off Tunisia clustered alongside isolates from P. pagrus and P. erythrinus across the Western Mediterranean. We also provide novel morphometric and anatomical data for M. erythrini sensu lato based on Adriatic specimens (Montenegro) and discuss host specificity patterns in Microcotyle spp. from the Mediterranean. These findings emphasize the importance of comprehensive taxonomic revisions and highlight the complexity of Microcotyle species associated with sparid hosts in the Mediterranean.Systematics and integrative taxonomy of Monogenea parasitizing fishes of Swede