Swedish Museum of Natural History
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Morphology and wall ultrastructure of a unique megaspore, Flabellisporites zhaotongensis Sui, McLoughlin et Feng sp. nov., from the upper Permian of Southwest China
No full textA new lycopsid megaspore species with intricate ornamentation, Flabellisporites zhaotongensis Sui, McLoughlin etFeng sp. nov., is described from the Lopingian Xuanwei Formation of Yunnan Province, Southwest China, using scanning and transmission electron microscopy. This trilete megaspore is characterized by elevated membraneous flanges adorned with multifurcate spines, the longest of which are discrete ribbon-like appendages that basally converge to form a membrane around the equator; and evenly spaced single or bifurcate spines with sharp tips covering the remaining surfaces. Ultrastructural analysis reveals that the megaspore wall consists of four layers: (1) a thin and dense foot layer; (2) an inner spongy layer with small circular or elongate sporopollenin grains with parallel arrangement; (3) an outer, more porous, spongy layer consisting of larger and better interconnected sporopollenin units, that form a grid-like structure in certain cases; and (4) an electron-dense outermost layer forming the sculptural elements. Both morphological and ultrastructural characteristics indicate that the new megaspore species belongs to Isoetales. Our discovery represents the oldest occurrence of Flabellisporites, indicating the origin of this morpho-lineage before the end-Permian mass extinction, and enriches the known diversity of isoetalean lycopsids in the late Permian Cathaysian Flora.This study was jointly supported by the National NaturalScience Foundation of China (42325201), the Second Tibetan Plateau Scientific Expedition and Research (2019QZKK0706), the Yunnan Province Science and Technology Department, the Key Research Program of the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS-201905), the China Scholarship Council (202207030014). S.M. is funded by grants from the Swedish ResearchCouncil (VR grant numbers 2018-04527 and 2022-03920).</p
Carbon cycle perturbations and environmental change of the middle permian and Late Triassic Paleo-Antarctic circle
No full textDuring the middle Permian through the Triassic, Tasmania moved from paleo-latitudes of 78° to 69°S, wedged between Antarctica and Australia, within the paleo-South polar circle. During this time, significant global carbon cycle disturbances triggered major environmental and climatic changes and mass extinction events globally. The Bicheno-5 core from Eastern Tasmania, Australia, provides the opportunity to examine middle Permian and Upper Triassic sediments from the paleo-Antarctic, using high-resolution organic carbon isotope (δ13CTOC) chemostratigraphy, pXRF, and sedimentology, combined with new palynological data integrated with the existing radiometric age model. While there is a significant unconformity in the Upper Permian to the middle Triassic associated with eustatic sea-level fall as a result of regional uplift in eastern Australia, three distinct carbon isotope excursions (CIEs), characterized by negative shifts of up to − 6 ‰ were identified; the middle Permian Guadalupian Carbon Isotope Excursions (G-CIE), the Carnian Pluvial Episode (CPE), and the mid-Norian Event (MNE). These three events highlight a significant climate shift through glacial and interglacial cycles to warmer non-glacial intervals in the Late Triassic, with evidence of the polar record of the Carnian Pluvial Episode and the mid-Norian Event, which are poorly studied in the Southern Hemisphere, specifically within the Paleo-Antarctic circle.Authors thank the Tasmania Department of Mines for the permission and invitation to work with its data and consolidate basic concepts from all the sources. Khalifa University of Science and Technology supports this work under the funding of CIRA-2019-066. Funding is also acknowledged from The Knut and Alice WallenbergFoundation, grant KAW 2020.0145 (to V.V).</p
Graphic and statistical overview of temporal trends and spatial variations within the Swedish National Monitoring Programme for Contaminants in Marine Biota (until 2022 year’s data)
No full textAn Oligocene chimaeroid egg capsule from western Washington State, USA, and priority of Vaillantoonia Meunier, 1891
No full textFossil egg capsules of chimaeroids (holocephalian fishes), although rare, have been known for more than 150 years (Bessels, 1869; Meunier, 1891a) and have been found in rocks as old as Upper Triassic (Gottfried and Fordyce, 2014). Egg capsules of extant chimaeroids are spindle shaped, with a smooth central body where the embryo develops, an elongate anterior beak through which the hatchling emerges, and an elongate posterior pedicle. The capsules are flanked by a lateral membrane or web on both sides, and the web is reinforced with branching or unbranching rib-like costae that extend laterally from the central body, beak, and pedicle. Specimens are typically about 10–30 cm long. Egg capsules of extant chimaeroids are made of collagen (Hamlett et al., 2005) and as fossils, chimaeroid egg capsules are typically preserved as external casts (Fischer et al., 2014)
Gene flow and an anomaly zone complicate phylogenomic inference in a rapidly radiated avian family (Prunellidae)
No full textResolving the phylogeny of rapidly radiating lineages presents a challenge when building the Tree of Life. An Old World avian family Prunellidae (Accentors) comprises twelve species that rapidly diversified at the Pliocene–Pleistocene boundary. Here we investigate the phylogenetic relationships of all species of Prunellidae using a chromosome-level de novo assembly of Prunella strophiata and 36 high-coverage resequenced genomes. We use homologous alignments of thousands of exonic and intronic loci to build the coalescent and concatenated phylogenies and recover four different species trees. Topology tests show a large degree of gene tree-species tree discordance but only 40–54% of intronic gene trees and 36–75% of exonic genic trees can be explained by incomplete lineage sorting and gene tree estimation errors. Estimated branch lengths for three successive internal branches in the inferred species trees suggest the existence of an empirical anomaly zone. The most common topology recovered for species in this anomaly zone was not similar to any coalescent or concatenated inference phylogenies, suggesting presence of anomalous gene trees. However, this interpretation is complicated by the presence of gene flow because extensive introgression was detected among these species. When exploring tree topology distributions, introgression, and regional variation in recombination rate, we find that many autosomal regions contain signatures of introgression and thus may mislead phylogenetic inference. Conversely, the phylogenetic signal is concentrated to regions with low-recombination rate, such as the Z chromosome, which are also more resistant to interspecific introgression. Collectively, our results suggest that phylogenomic inference should consider the underlying genomic architecture to maximize the consistency of phylogenomic signal
Microbial landscapes in Trinervitermes trinervoides termite colonies are affected by mound compartments and soil properties but not by symbiotic Podaxis fungi
No full textTermites are important ecosystem engineers and play key roles in modulating microbial communities within and outside their mounds. Microbial diversity within termite mounds is generally lower than surrounding soils, due to termite-associated antimicrobial compounds and active sanitary behaviours. Microbial symbionts of termites can also influence the microbial landscape, by inhibiting or out-competing other microbes. Certain members of the arid habitat fungal genus Podaxis (Agaricomycetes; Agaricaceae) are symbiotic with savannah specialist grass-cutting termites, and have the potential to influence mound-associated microbiomes. To test this, wecharacterized fungal (ITS2) and bacterial (16S rRNA) communities within and outside 49 Trinervitermes trinervoides mounds with and without Podaxis fruiting bodies across a 1000 km transect in South Africa. We predicted that Podaxis would be a dominant member of the fungal communities in mounds and negatively impact microbial diversity. Further, we explored how environmental variables shaped microbial communities, including whether soil elemental composition affected Podaxis presence. As expected, we observed less diverse fungal communities, but not bacterial communities, within than outside mounds, while microbial communities differed by sampling regions and mound compartments. Podaxis sequences were present in 48 out of 49 mounds in low relative abundances, and neither fruiting body presence nor sequence abundance were associated with microbial diversity or composition. There was, however, an overall association between the presence of Podaxis fruiting bodies and elemental composition, with different elements displaying varying associations depending on geographic region. Both environmental variables and soil elements were associated with fungal and bacterial taxa, indicating that they are key drivers of microbial community composition. Taken together, our findings suggest that microbial landscapes in termite mounds are not strongly influenced by Podaxis but mainly driven by termite filtering and regional abiotic variables and elemental compositions
A Paleoproterozoic magmatic flare-up in the Central Domain of the Ketilidian Orogen, South Greenland, and correlations to Canada and Scandinavia
No full textThe Central Domain of the Ketilidian Orogen in South Greenland preserves two magmatic events that provide insight into crustal architecture and represent a major contribution to continental crustal growth in connection with the assembly of the late Paleoproterozoic-Mesoproterozoic supercontinent Columbia/Nuna. This study provides zircon U-Pb geochronology for the western parts of the Central Domain and, combined with previous published age data, documents crustal evolution in the orogeny. The geochronological data indicate an initial volumetrically-minor magmatic event at ca. 1850 Ma, referred to here as the Older Julianehåb Igneous Suite, followed by a pause in magmatic activity. This is followed by the Younger Julianehåb Igneous Suite, a major pulse of magmatism (comparable to magmatic flare-ups in Phanerozoic arcs) between ca. 1814 and 1795 Ma. The adjacent arcs in the Makkovik Province, Canada, and the Transscandinavian Igneous Belt, Scandinavia, preserve similarly-aged magmatic events and appear to young from west to east. Exposure levels in the Makkovik Province are shallower than in the Ketilidian Orogen, and shallower supracrustal deposits are significantly more abundant in the Makkovik Province, indicating significant differences in modern erosion levels
Microstructural and isotopic analysis of shocked monazite from the Hiawatha impact structure: development of porosity and its utility in dating impact craters
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