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Rise of the Toxic Slime : During the world’s worst mass extinction, bacteria and algaedevastated rivers and lakes—a warning for today
No full textLife on Earth has experienced some terrifyingly close calls in the past four billion years—cataclysmic events in which the species driven to extinction outnumbered the survivors. The worst crisis occurred 252 million years ago, at the end of the Permian Period. Conditions back then were the bleakest that animals ever faced. Wildfires and drought scoured the land; oceans became intolerably hot and suffocating. Very few creatures could survive in this hellscape. Ultimately more than 70 percent of land species and upward of 80 percent of ocean species went extinct, leading some paleontologists to call this dismal episode the Great Dying.The authors acknowledge the support of researchgrant EAR-1636625 from the National Science Foundation, and the Swedish Research Council (VR) grants 2018-04527 to SM and 2019-4061 to VV.</p
Sphenobaiera insecta from the Upper Triassic of South Australia, with a clarification of the genus Sphenobaiera (fossil Ginkgophyta) and its delimitation from similar foliage genera
No full textUpper Triassic deposits of the Leigh Creek Coal Measures in South Australia yield exquisitely preserved plant fossils of a typical mid- to high-latitude Gondwanan flora. Here, we presenta detailed cuticular analysis of the ginkgoalean leaf Sphenobaiera insecta J.M. Anderson et H.M.Anderson nov. emend., which is characterized by an unlobed or once-lobed, elliptic to oblanceolate lamina, abundant round to fusiform resin bodies, and absence of interveinal striae. We also propose an emendation to the genus diagnosis so that Sphenobaiera encompasses also unlobed leaves such as most of those attributed to S. insecta. Such leaves may be distinguished from morphologically similar co-occurring leaf taxa, such as Heidiphyllum elongatum (Pinales) and Rochipteris spp. (Petriellales), based on the characteristic resin bodies and sporadic occurrence of vein dichotomies in the central lamina. Sphenobaiera insecta leaves show common evidence of a particular type of herbivory damage along the leaf margin in the form of small (1–1.5-mm-long) semi-circular patches each lined by a crescent-shaped, darkened reaction rim.This work was supported by the DeutscheForschungsgemeinschaft (DFG) under Grant BO3131/1(Emmy Noether project “Latitudinal Patterns in PlantEvolution”) to B.B. and by the Vetenskapsrådet (VR) under Grant 2018-04527 to S.M.; </p
A new proteid salamander (Urodela, Proteidae) from the middle Miocene of Hambach (Germany) and implications for the evolution of the family
No full textMembers of the urodele family Proteidae currently account for eight extant species within two genera and at least four extinct species within three genera. The clade has a clear disjunct geographical range, with the extinct Paranecturus and the extant Necturus in North America and the extinct Mioproteus and the extant Proteus in Europe and Asia. A recent phylogenetic analysis supported a Eurasian clade including both fossil and living species found east of the Atlantic Ocean. However, the finding of a new proteid salamander, herein named Euronecturus grogu, from the Miocene of western Germany sheds new light on the evolution of this family, challenging the idea of all Eurasian members of the group deriving from a single lineage separated from the North American ones at least prior to the Oligocene. This new proteid taxon is based on five isolated atlases found in late Orleanian (MN 5) sediments in Hambach 6C, and displays features that are unknown in any other proteid, such as the presence of secondary dorsal crests, small and posteriorly-directed postzygapophyses, and (in at least some specimens) a wide and deep ventral fossa between the anterior cotyles. A phylogenetic analysis recovered the new taxon in an earl ybranching position within Proteidae, sister to all other proteids but the late Maastrichtian Paranecturus. It thus suggests the presence in Europe of a second proteid lineage, currently known only in the middle Miocene, that appears unrelated to the Mioproteus–Proteus clade.We gratefully acknowledge the support of the mining company RWE POWER AG (Cologne) during fieldwork at the Hambach locality. LM received support from Fondi di Ateneo dell'Università di Torino (2018–2019) and from the SYNTHESYS Project http://www.synthesys.info/ (FR-TAF 2486, HU-TAF 2724, AT-TAF-8564). This is publication number 357 of the Museum of Geology and Palaeontology of the University of Torino. AV was funded by a Humboldt Research Fellowship from the Alexander von Humboldt Foundation during part of the development of this work. He is now funded by the Agencia Española de Investigación, with a Juan de la Cierva-Formación grant (FCI2019-039443-I/AEI/10.13039/501100011033). TM was funded by the Deutsche Forschungsgemeinschaft (DFG) Special Research Project SFB 350.</p
The effects of four decades of climate change on the breeding ecology of an avian sentinel species across a 1,500-km latitudinal gradient are stronger at high latitudes.
No full textSedimentology of the continental end-Permian extinction eventin the Sydney Basin, eastern Australia
No full textUpper Permian to Lower Triassic coastal plain successions of the Sydney Basin in eastern Australia have been investigated in outcrop and continuous drillcores. The purpose of the investigation is to provide an assessment of palaeoenvironmental change at high southern palaeolatitudes in a continental margin context for the late Permian (Lopingian), across the end‐Permian Extinction interval, and into the Early Triassic. These basins were affected by explosive volcanic eruptions during the late Permian and, to a much lesser extent, during the Early Triassic, allowing high‐resolution age determination on the numerous tuff horizons. Palaeobotanical and radiogenic isotope data indicate that the end‐Permian Extinction occurs at the top of the uppermost coal bed, and the Permo‐Triassic boundary either within an immediately overlying mudrock succession or within a succeeding channel sandstone body, depending on locality due to lateral variation. Late Permian depositional environments were initially (during the Wuchiapingian) shallow marine and deltaic, but coastal plain fluvial environments with extensive coal‐forming mires became progressively established during the early late Permian, reflected in numerous preserved coal seams. The fluvial style of coastal plain channel deposits varies geographically. However, apart from the loss of peat‐forming mires, no significant long‐term change in depositional style (grain size, sediment‐body architecture, or sediment dispersal direction) was noted across the end‐Permian Extinction (pinpointed by turnover of the palaeoflora). There is no evidence for immediate aridification across the boundary despite a loss of coal from these successions. Rather, the end‐Permian Extinction marks the base of a long‐term, progressive trend towards better‐drained alluvial conditions into the Early Triassic. Indeed, the floral turnover was immediately followed by a flooding event in basinal depocentres, following which fluvial systems similar to those active prior to the end‐Permian Extinction were re‐established. The age of the floral extinction is constrained to 252.54 ± 0.08 to 252.10 ± 0.06 Ma by a suite of new Chemical Abrasion Isotope Dilution Thermal Ionization Mass Spectrometry U‐Pb ages on zircon grains. Another new age indicates that the return to fluvial sedimentation similar to that before the end‐Permian Extinction occurred in the basal Triassic (prior to 251.51 ± 0.14 Ma). The character of the surface separating coal‐bearing pre‐end‐Permian Extinction from coal‐barren post‐end‐Permian Extinction strata varies across the basins. In basin‐central locations, the contact varies from disconformable, where a fluvial channel body has cut down to the level of the top coal, to conformable where the top coal is overlain by mudrocks and interbedded sandstone–siltstone facies. In basin‐marginal locations, however, the contact is a pronounced erosional disconformity with coarse‐grained alluvial facies overlying older Permian rocks. There is no evidence that the contact is everywhere a disconformity or unconformity
Genetic variation between and within two populations of bat-eared foxes (Otocyon megalotis Desmarest, 1822) in South Africa
No full textInformation on genetic variation within and among populations is relevant for a broad range of topics in biology. We use a combination of mitochondrial and nuclear microsatellite markers to evaluate genetic variation within and between two populations of bat-eared foxes (Otocyon megalotis Desmarest, 1822) in South Africa. The bat-eared fox is a small canid occurring in southern and eastern Africa. The species is currently not threatened with extinction, but a lack of information on genetic diversity has been identified as a deficit for its future conservation. We observed low to moderate genetic differentiation between the two geographically separated populations, but neither mitochondrial nor nuclear microsatellite markers suggested that there have been dispersal barriers between them. Similar genetic diversity within both populations was contrasted by interpopulational differences in relatedness variation among males and females. A high genetic relatedness within both populations, indicated by mitochondrial data, is likely caused by a common historical origin or a combination of species-specific social organization and environmental dispersal constraints. We call for further research on the genetic divergence of bat-eared fox populations as well as on the genetic consequences of interactions between environmental characteristics and social organization in this species
Combining Bayesian age models and genetics to investigate population dynamics and extinction of the last mammoths in northern Siberia
No full textPopulation genomics of the critically endangered kākāpō
No full textSummary The kākāpō is a flightless parrot endemic to New Zealand. Once common in the archipelago, only 201 individuals remain today, most of them descending from an isolated island population. We report the first genome-wide analyses of the species, including a high-quality genome assembly for kākāpō, one of the first chromosome-level reference genomes sequenced by the Vertebrate Genomes Project (VGP). We also sequenced and analyzed 35 modern genomes from the sole surviving island population and 14 genomes from the extinct mainland population. While theory suggests that such a small population is likely to have accumulated deleterious mutations through genetic drift, our analyses on the impact of the long-term small population size in kākāpō indicate that present-day island kākāpō have a reduced number of harmful mutations compared to mainland individuals. We hypothesize that this reduced mutational load is due to the island population having been subjected to a combination of genetic drift and purging of deleterious mutations, through increased inbreeding and purifying selection, since its isolation from the mainland ∼10,000 years ago. Our results provide evidence that small populations can survive even when isolated for hundreds of generations. This work provides key insights into kākāpō breeding and recovery and more generally into the application of genetic tools in conservation efforts for endangered species
Coreomyces (Laboulbeniales) in Sweden, with two new species
No full textThe genus Coreomyces (Laboulbeniaceae, Laboulbeniomycetes, Ascomycota) includes minute parasites on water boatmen (Corixidae, Hemiptera, Insecta). This taxonomic study is primarily based on freshly sampled corixids infected by Coreomyces from Sweden, although a few samples from Denmark and Turkey were also included. All records were verified using DNA sequence data from the internal transcribed spacer region and large subunit of the nuclear ribosomal DNA repeat region. We recognise four species, two of which are new to science: Coreomyces confusus H. Sundb. et al. sp. nov., C. corixae Thaxt., C. dextrorsus H. Sundb. et al. sp. nov. and C. macropus Thaxt. Coreomyces corixae is new to Denmark, Sweden and Turkey, while C. macropus is new to Denmark and Sweden. Coreomyces confusus is morphologically very similar to C. macropus and also occupies the same positions on the same host species, although it seems to be less common. Coreomyces dextrorsus resembles C. corixae morphologically but is usually considerably larger. It infects the same host species as C. corixae and also shares one of its positions on the host with C. corixae, although it is much more common in its species-specific position. All four species can inhabit two different yet distinct positions on the host. We observe that morphology is affected by the position on the host and that different species sharing the same position on the host tend to be difficult or impossible to separate on morphology only. We conclude that species circumscriptions in Coreomyces must be based on the integration of molecular and morphological data