Thriving or surviving? The isotopic record of the Wrangel Island woolly mammoth population

The world's last population of woolly mammoths (Mammuthus primigenius) lived on Wrangel Island persisting well into the Holocene, going extinct at ca. 4000 cal BP. According to the frequency of 'radiocarbon dated mammoth remains from the island, the extinction appears fairly abrupt. This study investigates the ecology of the Wrangel Island mammoth population by means of carbon, nitrogen and sulfur isotope analyses. We report new isotope data on 77 radiocarbon dated mammoth specimens from Wrangel Island and Siberia, and evaluate them in relation to previously published isotope data for Pleistocene mammoths from Beringia and lower latitude Eurasia, and the other insular Holocene mammoth population from St. Paul Island. Contrary to prior suggestions of gradual habitat deterioration, the nitrogen isotope values of the Wrangel Island mammoths do not support a decline in forage quality/quantity, and are in fact very similar to their north Beringian forebears right to the end. However, compared to Siberian mammoths, those from Wrangel Island show a difference in their energy economy as judged by the carbon isotope values of structural carbonate, possibly representing a lower need of adaptive strategies for survival in extreme cold. Increased mid-Holocene weathering of rock formations in the central mountains is suggested by sulfur isotope values. Scenarios related to water quality problems stemming from increased weathering, and a possibility of a catastrophic starvation event as a cause of, or contributing factor in their demise are discussed. (C) 2019 The Authors. Published by Elsevier Ltd.Peer reviewe

Boosting Terahertz Photoconductive Antenna Performance with Optimised Plasmonic Nanostructures

Advanced nanophotonics penetrates into other areas of science and technology, ranging from applied physics to biology, which results in many fascinating cross-disciplinary applications. It has been recently demonstrated that suitably engineered light-matter interactions at the nanoscale can overcome the limitations of today’s terahertz (THz) photoconductive antennas, making them one step closer to many practical implications. Here, we push forward this concept by comprehensive numerical optimization and experimental investigation of a log-periodic THz photoconductive antenna coupled to a silver nanoantenna array. We shed light on the operation principles of the resulting hybrid THz antenna, providing an approach to boost its performance. By tailoring the size of silver nanoantennas and their arrangement, we obtain an enhancement of optical-to-THz conversion efficiency 2-fold larger compared with previously reported results for similar structures, and the strongest enhancement is around 1 THz, a frequency range barely achievable by other compact THz sources. We also propose a cost-effective fabrication procedure to realize such hybrid THz antennas with optimized plasmonic nanostructures via thermal dewetting process, which does not require any post processing and makes the proposed solution very attractive for applications

Combining modern tracking data and historical records improves understanding of the summer habitats of the Eastern Lesser White‐fronted Goose Anser erythropus

Abstract: The Lesser White‐fronted Goose (Anser erythropus), smallest of the “gray” geese, is listed as Vulnerable on the IUCN Red List and protected in all range states. There are three populations, with the least studied being the Eastern population, shared between Russia and China. The extreme remoteness of breeding enclaves makes them largely inaccessible to researchers. As a substitute for visitation, remotely tracking birds from wintering grounds allows exploration of their summer range. Over a period of three years, and using highly accurate GPS tracking devices, eleven individuals of A. erythropus were tracked from the key wintering site of China, to summering, and staging sites in northeastern Russia. Data obtained from that tracking, bolstered by ground survey and literature records, were used to model the summer distribution of A. erythropus. Although earlier literature describes a patchy summer range, the model suggests a contiguous summer habitat range is possible, although observations to date cannot confirm A. erythropus is present throughout the modeled range. The most suitable habitats are located along the coasts of the Laptev Sea, primarily the Lena Delta, in the Yana‐Kolyma Lowland, and smaller lowlands of Chukotka with narrow riparian extensions upstream along major rivers such as the Lena, Indigirka, and Kolyma. The probability of A. erythropus presence is related to areas with altitude less than 500 m with abundant wetlands, especially riparian habitat, and a climate with precipitation of the warmest quarter around 55 mm and mean temperature around 14°C during June‐August. Human disturbance also affects site suitability, with a gradual decrease in species presence starting around 160 km from human settlements. Remote tracking of animal species can bridge the knowledge gap required for robust estimation of species distribution patterns in remote areas. Better knowledge of species' distribution is important in understanding the large‐scale ecological consequences of rapid global change and establishing conservation management strategies

Population dynamics and demographic history of Eurasian collared lemmings.

BACKGROUND: Ancient DNA studies suggest that Late Pleistocene climatic changes had a significant effect on population dynamics in Arctic species. The Eurasian collared lemming (Dicrostonyx torquatus) is a keystone species in the Arctic ecosystem. Earlier studies have indicated that past climatic fluctuations were important drivers of past population dynamics in this species. RESULTS: Here, we analysed 59 ancient and 54 modern mitogenomes from across Eurasia, along with one modern nuclear genome. Our results suggest population growth and genetic diversification during the early Late Pleistocene, implying that collared lemmings may have experienced a genetic bottleneck during the warm Eemian interglacial. Furthermore, we find multiple temporally structured mitogenome clades during the Late Pleistocene, consistent with earlier results suggesting a dynamic late glacial population history. Finally, we identify a population in northeastern Siberia that maintained genetic diversity and a constant population size at the end of the Pleistocene, suggesting suitable conditions for collared lemmings in this region during the increasing temperatures associated with the onset of the Holocene. CONCLUSIONS: This study highlights an influence of past warming, in particular the Eemian interglacial, on the evolutionary history of the collared lemming, along with spatiotemporal population structuring throughout the Late Pleistocene

Selective polarization generation in an amplifying photonic crystal with 2D array of metal nanoparticles

International audienc

Geolocator tagging of east Siberian Bluethroats

The Bluethroat subspecies Cyanecula svecica svecia occurs throughout the northern Palearctic. European C. s. svecia has been shown to follow a route west of the Himalaya to winter quarters in southern Asia. Out of 30 Bluethroats tagged with geolocators in eastern Siberia, we obtained one track suggesting that it migrated east of the Himalaya to a wintering area located in Myanmar. The different routes of western and eastern C. s. svecia implicate the presence of a migratory divide in Siberia, either formed in situ during the post-glacial colonization process or resulting from a secondary contact between different refuge populations

Development and Optimization of a Silica Column-Based Extraction Protocol for Ancient DNA

Rapid and cost-effective retrieval of endogenous DNA from ancient specimens remains a limiting factor in palaeogenomic research. Many methods have been developed to increase ancient DNA yield, but modifications to existing protocols are often based on personal experience rather than systematic testing. Here, we present a new silica column-based extraction protocol, where optimizations were tested in controlled experiments. Using relatively well-preserved permafrost samples, we tested the efficiency of pretreatment of bone and tooth powder with a bleach wash and a predigestion step. We also tested the recovery efficiency of MinElute and QIAquick columns, as well as Vivaspin columns with two molecular weight cut-off values. Finally, we tested the effect of uracil-treatment with two different USER enzyme concentrations. We find that neither bleach wash combined with a predigestion step, nor predigestion by itself, significantly increased sequencing efficiency. Initial results, however, suggest that MinElute columns are more efficient for ancient DNA extractions than QIAquick columns, whereas different molecular weight cut-off values in centrifugal concentrator columns did not have an effect. Uracil treatments are effective at removing DNA damage even at concentrations of 0.15 U/µL (as compared to 0.3 U/µL) of ancient DNA extracts

Combining modern tracking data and historical records improves understanding of the summer habitats of the Eastern Lesser White-fronted Goose Anser erythropus

The Lesser White-fronted Goose (Anser erythropus), smallest of the “gray” geese, is listed as Vulnerable on the IUCN Red List and protected in all range states. There are three populations, with the least studied being the Eastern population, shared between Russia and China. The extreme remoteness of breeding enclaves makes them largely inaccessible to researchers. As a substitute for visitation, remotely tracking birds from wintering grounds allows exploration of their summer range. Over a period of three years, and using highly accurate GPS tracking devices, eleven individuals of A. erythropus were tracked from the key wintering site of China, to summering, and staging sites in northeastern Russia. Data obtained from that tracking, bolstered by ground survey and literature records, were used to model the summer distribution of A. erythropus. Although earlier literature describes a patchy summer range, the model suggests a contiguous summer habitat range is possible, although observations to date cannot confirm A. erythropus is present throughout the modeled range. The most suitable habitats are located along the coasts of the Laptev Sea, primarily the Lena Delta, in the Yana-Kolyma Lowland, and smaller lowlands of Chukotka with narrow riparian extensions upstream along major rivers such as the Lena, Indigirka, and Kolyma. The probability of A. erythropus presence is related to areas with altitude less than 500 m with abundant wetlands, especially riparian habitat, and a climate with precipitation of the warmest quarter around 55 mm and mean temperature around 14°C during June-August. Human disturbance also affects site suitability, with a gradual decrease in species presence starting around 160 km from human settlements. Remote tracking of animal species can bridge the knowledge gap required for robust estimation of species distribution patterns in remote areas. Better knowledge of species' distribution is important in understanding the large-scale ecological consequences of rapid global change and establishing conservation management strategies