Reframing the mammoth steppe: Insights from analysis of isotopic niches

Woolly mammoth (Mammuthus primigenius), horse (Equus spp.) and bison (Bison spp.) coexisted with a variety of mammalian megafauna across the Pleistocene mammoth steppe – a megacontinental ecosystem that spanned northern Eurasia and northwestern North America. Previous research has suggested that highly conserved niches with minimal niche overlap allowed high levels of species diversity on the mammoth steppe. Here we evaluate previously published and some new collagen carbon and nitrogen isotope data (δ13C, δ15N) for mammoth steppe megaherbivores using Stable Isotope Bayesian Ellipses in R (SIBER) and linear regression models to determine isotopic niches for individual species during broad time intervals (pre-, during and post-Last Glacial Maximum (LGM)) at multiple geographic regions across the mammoth steppe. Individual species maintained relatively consistent isotopic niche positions at different geographic locations and during different times. Diet and habitat niches for any given species appear to have been similar across the mammoth steppe. Between some regions and times, however, species' isotopic niches changed, suggesting adaptation to local climatic conditions and/or changes in the nitrogen isotope patterns at the base of the food web. Isotopic niche overlap, including at the level of core niche overlap (>60% overlap), was observed in at least one time and region for most species. This overlap suggests high levels of functional redundancy in the ecosystem, whereby one species could fulfil another's ecological role in the latter's absence. Despite spatial and temporal environmental variation, species' adaptability and functional redundancy within the ecosystem would have made the mammoth steppe a highly resilient ecosystem

American Mastodon Mitochondrial Genomes Suggest Multiple Dispersal Events in Response to Pleistocene Climate Oscillations

Pleistocene glacial-interglacial cycles are correlated with dramatic temperature oscillations. Examining how species responded to these natural fluctuations can provide valuable insights into the impacts of present-day anthropogenic climate change. Here we present a phylogeographic study of the extinct American mastodon (Mammut americanum), based on 35 complete mitochondrial genomes. These data reveal the presence of multiple lineages within this species, including two distinct clades from eastern Beringia. Our molecular date estimates suggest that these clades arose at different times, supporting a pattern of repeated northern expansion and local extirpation in response to glacial cycling. Consistent with this hypothesis, we also note lower levels of genetic diversity among northern mastodons than in endemic clades south of the continental ice sheets. The results of our study highlight the complex relationships between population dispersals and climate change, and can provide testable hypotheses for extant species expected to experience substantial biogeographic impacts from rising temperatures

Evolutionary history of saber-toothed cats based on ancient mitogenomics

Saber-toothed cats (Machairodontinae) are among the most widely recognized representatives of the now largely extinct Pleistocene megafauna. However, many aspects of their ecology, evolution, and extinction remain uncertain. Although ancient-DNA studies have led to huge advances in our knowledge of these aspects of many other megafauna species (e.g., mammoths and cave bears), relatively few ancient-DNA studies have focused on saber-toothed cats, and they have been restricted to short fragments of mitochondrial DNA. Here we investigate the evolutionary history of two lineages of saber-toothed cats (Smilodon and Homotherium) in relation to living carnivores and find that the Machairodontinae form a well-supported clade that is distinct from all living felids. We present partial mitochondrial genomes from one S. populator sample and three Homotherium sp. samples, including the only Late Pleistocene Homotherium sample from Eurasia. We confirm the identification of the unique Late Pleistocene European fossil through ancient-DNA analyses, thus strengthening the evidence that Homotherium occurred in Europe over 200,000 years later than previously believed. This in turn forces a re-evaluation of its demography and extinction dynamics. Within the Machairodontinae, we find a deep divergence between Smilodon and Homotherium ( 18 million years) but limited diversity between the American and European Homotherium specimens. The genetic data support the hypothesis that all Late Pleistocene (or post-Villafrancian) Homotherium should be considered a single species, H. latidens, which was previously proposed based on morphological data

The Prognostic Significance of Whole Blood Global and Specific DNA Methylation Levels in Gastric Adenocarcinoma

Epigenetics, particularly DNA methylation, has recently been elucidated as important in gastric cancer (GC) initiation and progression. We investigated the clinical and prognostic importance of whole blood global and site-specific DNA methylation in GC. tests. Survival analyses were carried out using the Kaplan-Meier method and log rank test. A backward conditional Cox proportional hazards regression model was used to identify independent predictors of survival. = 0.02) respectively.Analysis of global and site-specific DNA methylation in peripheral blood by pyrosequencing provides quantitative DNA methylation values that may serve as important prognostic indicators

Achieved systolic blood pressure in older people: A systematic review and meta-analysis

Background: It remains unclear into which level the systolic blood pressure (SBP) should be lowered in order to provide the best cardiovascular protection among older people. Hypertension guidelines recommendation on attaining SBP levels 33,600 participants) were included. Compared with attaining SBP levels ≥140 mmHg, levels of 130 to <140 mmHg were not associated with lower risk of outcomes in the meta-analysis of RCTs, whereas there was an associated reduction of cardiovascular mortality (RR 0.72, 95% CI 0.59-0.88) and all-cause mortality (RR 0.86, 95% CI 0.75-0.99) in the meta-analysis of post-hoc analyses or subanalyses of RCTs. Limited and conflicting data were available for the SBP levels of <130 mmHg and 140 to <150 mmHg. Conclusions: Among older people, there is suggestive evidence that achieving SBP levels of 130 to <140 mmHg is associated with lower risks of cardiovascular and all-cause mortality. Future trials are required to confirm these findings and to provide additional evidence regarding the <130 and 140 to <150 mmHg SBP levels

Nitrogen and Carbon Isotopic Dynamics of Subarctic Soils and Plants in Southern Yukon Territory and its Implications for Paleoecological and Paleodietary Studies

We examine here the carbon and nitrogen isotopic compositions of bulk soils (8 topsoil and 7 subsoils, including two soil profiles) and five different plant parts of 79 C3 plants from two main functional groups: herbs and shrubs/subshrubs, from 18 different locations in grasslands of southern Yukon Territory, Canada (eastern shoreline of Kluane Lake and Whitehorse area). The Kluane Lake region in particular has been identified previously as an analogue for Late Pleistocene eastern Beringia. All topsoils have higher average total nitrogen δ15N and organic carbon δ13C than plants from the same sites with a positive shift occurring with depth in two soil profiles analyzed. All plants analyzed have an average whole plant δ13C of −27.5 ± 1.2 ‰ and foliar δ13C of ±28.0 ± 1.3 ‰, and average whole plant δ15N of −0.3 ± 2.2 ‰ and foliar δ15N of ±0.6 ± 2.7 ‰. Plants analyzed here showed relatively smaller variability in δ13C than δ15N. Their average δ13C after suitable corrections for the Suess effect should be suitable as baseline for interpreting diets of Late Pleistocene herbivores that lived in eastern Beringia. Water availability, nitrogen availability, spacial differences and intra-plant variability are important controls on δ15N of herbaceous plants in the study area. The wider range of δ15N, the more numerous factors that affect nitrogen isotopic composition and their likely differences in the past, however, limit use of the modern N isotopic baseline for vegetation in paleodietary models for such ecosystems. That said, the positive correlation between foliar δ15N and N content shown for the modern plants could support use of plant δ15N as an index for plant N content and therefore forage quality. The modern N isotopic baseline cannot be applied directly to the past, but it is prerequisite to future efforts to detect shifts in N cycling and forage quality since the Late Pleistocene through comparison with fossil plants from the same region

Population dynamics and range shifts of moose (Alces alces) during the Late Quaternary

Aim: Late Quaternary climate oscillations had major impacts on species distributions and abundances across the northern Holarctic. While many large mammals in this region went extinct towards the end of the Quaternary, some species survived and flourished. Here, we examine population dynamics and range shifts of one of the most widely distributed of these, the moose (Alces alces). Location: Northern Holarctic. Taxon: Moose (A. alces). Methods: We collected samples of modern and ancient moose from across their present and former range. We assessed their phylogeographical relations using part of the mitochondrial DNA in conjunction with radiocarbon dating to investigate the history of A. alces during the last glacial. Results: This species has a relatively shallow history, with the most recent common ancestor estimated at ca. 150–50 kyr. Ancient samples corroborate that its region of greatest diversity is in east Asia, supporting proposals that this is the region of origin of all extant moose. Both eastern and western haplogroups occur in the Ural Mountains during the last glacial period, implying a broader contact zone than previously proposed. It seems that this species went extinct over much of its northern range during the last glacial maximum (LGM) and recolonized the region with climate warming beginning around 15,000 yr bp. The post-LGM expansion included a movement from northeast Siberia to North America via Beringia, although the northeast Siberian source population is not the one currently occupying that area. Main conclusions: Moose are a relatively recently evolved species but have had a dynamic history. As a large-bodied subarctic browsing species, they were seemingly confined to refugia during full-glacial periods and expanded their range northwards when the boreal forest returned after the LGM. The main modern phylogeographical division is ancient, though its boundary has not remained constant. Moose population expansion into America was roughly synchronous with human and red deer expansion. © 2020 The Authors. Journal of Biogeography published by John Wiley & Sons LtdWe warmly thank the following museums, curators and people for access to samples: the late Andrei Sher, Severtsov Institute, Moscow; Andy Currant, Natural History Museum, London; Alfred Gardner, Smithsonian, Washington DC; R. Dale Guthrie, University of Alaska, Fairbanks; John de Vos, National Museum of Natural History (Naturalis), Leiden; Eileen Westwig, American Museum of Natural History, NY; Fyodor Shidlovsky, Ice-Age Museum, Moscow; Tong Haowen, Institute of Vertebrate Palaeontology and Paleoanthropology, Beijing; Mammoth Museum, Yakutsk; Geological Museum, Yakutsk; Paleontological Institute, Moscow; Royal Alberta Museum, Edmonton; Zoological Institute, Saint Petersburg; Museum of the Institute of Plant and Animal Ecology, Ekaterinburg. We thank our Yukon First Nation research partners for their continued support for our work on the ice age fossils of Yukon Territory. We are grateful to the placer gold mining community and the Tr'ond?k Hw?ch'in First Nation for their continued support and partnership with our research in the Klondike goldfields region; and the Vuntut Gwitchin First Nation for their collaboration with research in the Old Crow region. We would also like to thank Shai Meiri for help in drawing the map and useful discussion, Tony Stuart for access to radiocarbon dates, and Iris van Pijlen for laboratory assistance. This research was funded by NERC grant NE/G00269X/1 through the European Union FP7 ERA-NET program BiodivERsA. Funding for AMS dating was provided through NERC/AHRC/ORAU Grant NF/2008/2/15

Grey wolf genomic history reveals a dual ancestry of dogs

The grey wolf (Canis lupus) was the first species to give rise to a domestic population, and they remained widespread throughout the last Ice Age when many other large mammal species went extinct. Little is known, however, about the history and possible extinction of past wolf populations or when and where the wolf progenitors of the present-day dog lineage (Canisfamiliaris) lived(1-8). Here we analysed 72 ancient wolf genomes spanning the last 100,000 years from Europe, Siberia and North America. We found that wolf populations were highly connected throughout the Late Pleistocene, with levels of differentiation an order of magnitude lower than they are today. This population connectivity allowed us to detect natural selection across the time series, including rapid fixation of mutations in the gene IFT8840,000-30,000 years ago. We show that dogs are overall more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, suggesting a domestication process in the east. However, we also found that dogs in the Near East and Africa derive up to half of their ancestry from a distinct population related to modern southwest Eurasian wolves, reflecting either an independent domestication process or admixture from local wolves. None of the analysed ancient wolf genomes is a direct match for either of these dog ancestries, meaning that the exact progenitor populations remain to be located.Peer reviewe

Grey wolf genomic history reveals a dual ancestry of dogs

The grey wolf (Canis lupus) was the first species to give rise to a domestic population, and they remained widespread throughout the last Ice Age when many other large mammal species went extinct. Little is known, however, about the history and possible extinction of past wolf populations or when and where the wolf progenitors of the present-day dog lineage (Canis familiaris) lived1,2,3,4,5,6,7,8. Here we analysed 72 ancient wolf genomes spanning the last 100,000 years from Europe, Siberia and North America. We found that wolf populations were highly connected throughout the Late Pleistocene, with levels of differentiation an order of magnitude lower than they are today. This population connectivity allowed us to detect natural selection across the time series, including rapid fixation of mutations in the gene IFT88 40,000–30,000 years ago. We show that dogs are overall more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, suggesting a domestication process in the east. However, we also found that dogs in the Near East and Africa derive up to half of their ancestry from a distinct population related to modern southwest Eurasian wolves, reflecting either an independent domestication process or admixture from local wolves. None of the analysed ancient wolf genomes is a direct match for either of these dog ancestries, meaning that the exact progenitor populations remain to be located