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Ancient mitochondrial and modern whole genomes unravel massive genetic diversity loss during near extinction of Alpine ibex
No full textSpatial and temporal variations in riverine mercury in the Mackenzie River Basin, Canada, from community-based water quality monitoring data.
No full textArctic rivers deliver~40 t yr−1 of mercury (Hg) to the Arctic Ocean, ~6%of which is from the Mackenzie River Basin(MRB), a region warming at ~3 times the mean hemispheric rate. How this will affect Hg transfer to ecosystems of theBeaufort Sea is a worrying issue. To help address this question, we analyzed >500 measurements ofHg and other waterproperties from 22 rivers collected in 2012–2018 by communities of the MRB. This new dataset provides a more comprehensiveview of riverine Hg variations across the basin than was previously available. We find that rivers issuedfrom mountains in the western MRB contribute the largest share of Hg in the Mackenzie River, 60–95 % of it beingcarried as fine suspended solids and probably sourced from riverbank erosion and thaw slumps. In contrast, lowlandrivers of the central and eastern MRB contribute larger shares of dissolved Hg (up to 78 %), likely from recent atmosphericdeposition through precipitation. Using load modelling constrained by the new water quality dataset, we estimatethat the three largest western tributaries (Liard, Peel and Arctic Red rivers) of the Mackenzie contribute 60 % ofthe annual MRB THg export and DHg export to the Beaufort Sea during freshet, as well as 51 % of DHg export, whilesupplying 60% of freshet discharge. Load modelling also reveals a sustained decline in DHg loads of ~13 kg yr−1 between2001 and 2016 in the lower Mackenzie River, which likely reflect a decreasing trend in atmospheric Hg depositionover most of northwestern Canada during this period. This study highlights the value of community-based waterquality monitoring in helping to support assessments of riverine Hg in theMRB in support of the Minamata Conventionon Mercury
Estimating a mortality threshold for the Belt Sea population of harbour porpoises
No full textFor small cetaceans bycatch in fishing gear is one of the largest threats towards their conservation. In order to effectively manage this threat, an estimation of the maximum number of animals that can be killed by anthropogenic activities each year is required. Such calculations rely on species or population specific information on population dynamics, and information on the current state of the population relative to carrying capacity. Here, we calculate the mortality limit for the Belt Sea population of harbour porpoises (Phocoena phocoena) based on a modified potential biological removal (mPBR) method. We estimate that for the population to reach the conservation objective set by ASCOBANS (the population should reach 80% of carrying capacity (assumed here to be 50,000 animals), with the assumption that this is achieved within 100 years with an 80% probability) a maximum of 29 animals can be removed annually. This removal rate applies a recover factor (Fr) of 0.1 that accounts for many uncertainties in population dynamics, abundance estimates, and the current removal rate and depletion level of the population. However, even using the highest possible Fr value (1.0) (which is not recommended for populations with unknown status and does not allow the population to reach the conservation objective), the mPBR limit of the population is 292, which is still significantly lower than the current estimated levels of bycatch in this population (~700 a year). Therefore, urgent action is required in order to ensure that this population is able to reach the conservation objective and achieve good environmental status under a range of European legislation.
Selenium concentration in herring from the Baltic Sea tracks decadal and spatial trends in external sources
No full textSelenium (Se) has a narrow range between nutritionally optimal and toxic concentrations for many organisms, including fish and humans. However, the degree to which humans are affecting Se concentrations in coastal food webs with diffuse Se sources is not well described. Here we examine large-scale drivers of spatio-temporal variability in Se concentration in herring from the Baltic Sea (coastal sea) to explore the anthropogenic impact on a species from the pelagic food web. We analyze data from three herring muscle time series covering three decades (1979–2010) and herring liver time series from 20 stations across the Baltic Sea covering a fourth decade (2009–2019). We find a 0.7–2.0% per annum (n = 26–30) Se decline in herring muscle samples from 0.34 ± 0.02 μg g−1 ww in 1979–1981 to 0.18 ± 0.03 μg g−1 ww in 2008–2010. This decrease continues in the liver samples during the fourth decade (6 of 20 stations show significant decrease). We also find increasing North-South and East-West gradients in herring Se concentrations. Using our observations, modelled Se deposition (spatio-temporal information) and estimated Se river discharge (spatial information), we show that the spatial variability in herring Se tracks the variability in external source loads. Further, between 1979 and 2010 we report a ∼5% per annum decline in direct Se deposition and a more gradual, 0.7–2.0% per annum, decline in herring Se concentrations. The slower rate of decrease for herring can be explained by stable or only slowly decreasing riverine inputs of Se to the Baltic Sea as well as recycling of Se within the coastal system. Both processes can reduce the effect of the trend predicted from direct Se deposition. We show that changing atmospheric emissions of Se may influence Se concentrations of a pelagic fish species in a coastal area through direct deposition and riverine inputs from the terrestrial landscape
Locating the BACE of the Cambrian: Bayan Gol in southwestern Mongolia and global correlation of the Ediacaran–Cambrian boundary
No full textThe diversification of animals during the Cambrian Period is one of the most significant evolutionary events inEarth’s history. However, the sequence of events leading to the origin of ‘modern’ ecosystems and the exacttemporal relationship between Ediacaran and Cambrian faunas are uncertain, as identification of the Ediacaran–Cambrian boundary and global correlation through this interval remains problematic. Here we review thecontroversies surrounding global correlation of the base of the Cambrian and present new high-resolutionbiostratigraphic, lithostratigraphic and δ13C chemostratigraphic data for terminal Ediacaran to basal Cambrianstrata in the Zavkhan Basin of Mongolia. This predominantly carbonate sequence, through the Zuun-Arts andBayangol formations in southwestern Mongolia, captures a distinct, negative δ13C excursion close to the top ofthe Zuun-Arts Formation recognized as the BAsal Cambrian carbon isotope Excursion (BACE). In this location,the nadir of the BACE closely coincides with first occurrence of the characteristic early Cambrian protoconodontProtohertzina anabarica. Despite recent suggestions that there is an evolutionary continuum of biomineralizinganimals across the Ediacaran–Cambrian transition, we suggest that this continuum is restricted to tubular forms,and that skeletal taxa such as Protohertzina depict ‘true’ Cambrian representatives that are restricted entirely tothe Cambrian. Employing the first appearance of the trace fossil Treptichnus pedum to define the base of theCambrian suffers significant drawbacks, particularly in carbonate settings where it is not commonly preserved.As T. pedum is the only proxy available to correlate the Cambrian Global boundary Stratotype Section and Point(GSSP) defined at Fortune Head, Newfoundland, we suggest that the GSSP be redefined elsewhere, in a newstratigraphic section that contains secondary markers that permit global correlation. We propose the nadir of theBACE as the favored candidate to define the base of the Cambrian. However, it is essential that the BACE becomplemented with secondary markers. In many global sections the nadir of the BACE and the first occurrence ofthe genus Protohertzina are closely juxtaposed, as are the BACE and T. pedum. Hence these taxa provide essentialbiostratigraphic control on the BACE and increase potential for effective global correlation. We also recommendthat an Auxiliary boundary Stratotype Section and Point (ASSP) be simultaneously established in order toincorporate additional markers that will aid global correlation of the Ediacaran–Cambrian boundary. The BAY4/5 section through the upper Zuun-Arts and Bayangol formations yields key shelly fossils and δ13C values and istherefore an ideal candidate for consideration as the GSSP for the Ediacaran–Cambrian boundary.The authors are supported by grants from the Swedish Research Council to T.P.T (VR2017-05183) and C.B.S. (VR2016-04610, VR2021-04295), a Young Thousand Talents Plan of China (41720104002) and National Natural Science Foundation of China to T.P.T. (42072003) and G.L (41890844). M.J.B is supported by research funds from Northwest University, Xi’an and the University of New England, Australia.</p
A Lower Cretaceous palynoflora from Carregueira (Lusitanian Basin, westernmost Iberia): taxonomic, stratigraphic and palaeoenvironmental implications
No full textHere we describe a new Lower Cretaceous palynoflora from the Lusitanian Basin, located in the westernmost sector of the Iberian Peninsula. The spore-pollen assemblage was extracted from samples collected in the Carregueira clay pit complex, located near the village of Juncal, western Portugal, from sedimentary deposits belonging to the Figueira da Foz Formation. A rich and well-preserved palynoflora, typical of non-marine fluvial environments, was recovered. Fifty-eight species and morphological groups of palynomorphs in 43 genera were recognized. The palynoflora is dominated by fern spores and conifer pollen. Angiosperm pollen is scarce and mainly represented by Afropollis, Clavatipollenites, Stellatopollis and Senectotetradites. Comparisons with described marine sections in Portugal suggest that the fossil horizon is lower Albian, corresponding to a hiatus between Zone I and Zone II in the Potomac Group of the eastern USA. The same beds contain a mesofossil flora dominated by angiosperm seeds, fruits and flowers. A similar contrast in the relative abundance of angiosperm mesofossils and pollen is seen at other Portuguese localities but is not evident in the Potomac Group. The palynoflora and the sedimentological data suggest deposition in wet lowland environments in a moderately humid regional setting.This research was supported by grants from the Amadeu Dias Foundation, the Portuguese Science Foundation (FCT) through the project UIDB/04292/2020 to MARE - Marine and Environmental Sciences Centre, the Czech Grant Agency (project 20-06134S) and by the Swedish Research Council (VR, grant no. 2019-4061).</p
New Material of Schizotheriine Chalicothere (Perissodactyla, Chalicotheriidae) from the Xianshuihe Formation (Early Miocene) of Lanzhou Basin, Northwest China
No full textA new schizotheriine mandible from the early Miocene Xianshuihe Formation in Lanzhou Basin, Northwest China is described here. Compared with other contemporaneous taxa, the lower jaw is most similar to Borissiakia betpakdalensis from Kazakhstan based on mandibular morphology and dental features, except for a much smaller body size which is hardly explained by intraspecific variation and suggests it represents a smaller body-sized species of Borissiakia. The type specimen of Phyllotillon huangheensis, from the same strata of the Lanzhou Basin, shares characters with the new specimen in the lower cheek teeth and the tapered morphology of the anterior horizontal ramus. Differences between both are reflected in the height of the ramus, especially the level of the symphysis, which may be an expression of sexual dimorphism. Therefore, schizotheriine mandibles from the early Miocene of Lanzhou Basin are regarded as the same taxon, and both are recognized as Borissiakia huangheensis. The occurrence of a chalicothere and other large perissodactyls may suggest that a certain amount of open woodland was distributed across the basin and that the paleoclimate might have been more humid during the early Miocene.Open access funding provided by Swedish Museum of Natural History. The present research was financially supported by the National Natural Science Foundation of China (NSFC 42172010). ZY L sincerely appreciates the China Scholarship Council (no. 202106970018) for one year of research as a visiting PhD student with TM at the Swedish Museum of Natural History.</p
Extinct seed plant diversity in the Early Cretaceous: An enigmatic new microsporangiate fossil with Decussosporites pollen in situ
No full textA new microsporangiate cone, Renbernia zhoui, is described from the mesofossil flora extracted from exposures ofthe Potomac Group at Puddledock, Virginia, U.S.A., which are of Early Cretaceous (early-middle Albian) age. The cone consists of densely arranged dorsiventrally flattened laminar, flabelliform microsporangiophores that bear two elongate microsporangia on the presumed abaxial surface. The microsporangia are separated by sterile tissue that expands apically into a prominent hood-like sterile extension. The microsporangia have extrorse valvate dehiscence and both microsporangia and sterile apical expansion are covered by a short stiff hairs. In situ pollen resembles Decussosporites, elliptical with a long median colpus on the presumed distal surface flanked laterally by two equally long lateral colpi. A short transverse colpus on the presumed proximal surface links the two lateral colpi and divides the grain into two parts creating the appearance of two sacci. Renbernia zhoui is similar to Brenneria potomacensis described from the slightly older Drewry's Bluff and Dutch Gap mesofossil floras from the Potomac Group that also has Decussosporites-type pollen in situ. However, Renbernia microsporangiophores are more distinctly laminar and have sporangia that are more prominently elongated and with a hood-like apical extension of sterile tissue. The in situ pollen is also much smaller, the pollen wall is much more distinctly perforate-foveolate rather than more or less psilate, and in Renbernia the saccus-like structures are not inflated. The relationship of Brenneria and Renbernia, as well as the possible link between Decussosporites-type pollen and pollen of Eucommiidites (Erdtmanithecales) is discussed.We thank the Paul Scherrer Institut, Villigen, Switzerland, for provisionof synchrotron radiation beamtime at the TOMCAT beamlineX02DA of the Swiss Light Source and Federica Marone for her helpat the beamline. Financial support was provided by the Swiss LightSource (project 20190071) and by the Swedish Research Council (Vetenskapsrådet 2014-5228 to E. M. Friis). We also thank the Oak Spring Garden Foundation for support during the preparation of this paper.</p
A guide to avian museomics: Insights gained from resequencing hundreds of avian study skins
No full textBiological specimens in natural history collections constitute a massive repository of genetic information. Many specimens have been collected in areas in which they no longer exist or in areas where present-day collecting is not possible. There are also specimens in collections representing populations or species that have gone extinct. Furthermore, species or populations may have been sampled throughout an extensive time period, which is particularly valuable for studies of genetic change through time. With the advent of high-throughput sequencing, natural history museum resources have become accessible for genomic research. Consequently, these unique resources are increasingly being used across many fields of natural history. In this paper, we summarize our experiences of resequencing hundreds of genomes from historical avian museum specimens. We publish the protocols we have used and discuss the entire workflow from sampling and laboratory procedures, to the bioinformatic processing of historical specimen data
