Genetic structure of the water frog (Pelophylax esculentus complex) populations in the south of the Central Russian Upland

BACKGROUND: The water frog (Pelophylax esculentus complex) is hybrid in composition. In view of the fact that a large number of data on the species composition of the water frog and very scarce material on the genetic structure of populations are available in the literature, we aimed to analyze the genetic structure of populations of the water frog in the southern part of the Middle Russian upland, which was one of the refugia for many species during the glacial epoch and the center of dispersion in the postglacial time, based on DNA microsatellite markers. MATERIALS AND METHODS: The study involved 36 local populations. DNA variability was analyzed by multiplex SSR-PCR. Seven loci (Res 14, Res 15, Res 17, Res 22, Rrid059A, Rrid082A, and Rrid171A) were used for amplification. Fragment analysis of PCR products was performed on an ABI PRISM 3500 automated capillary DNA sequencer (Applied Biosystems, USA). RESULTS: The total number of alleles detected ranged from 13 to 41. The effective number of alleles (Ae) averaged 4.569 0.219, the Chenon index (I) 1.567 0.04, level of expected heterozygosity (Не) 0.68 0.01. According to Wrights model, the greatest contribution to genetic variability is made by the heterogeneity of individuals within populations, some of which are of a hybrid nature (Fis = 0.281 0.069, Fit = 0.413 0.053, Fst = 0.180 0.017). The average indicator of the intensity of gene exchange between populations (Nm) was 1.212 0.142 individuals per generation. The calculation of the effective abundance using the LD method indicates a high level of viability of the studied groups of the frogs. CONCLUSION: The results demonstrated a high level of genetic diversity and viability of most of the studied groups, which, due to the intense gene exchange between them, can represent a single panmictic population. The data of the genetic analysis support the active adaptation of P. esculentus complex to living in an urbanized environment.

On the thickness of the Antarctic ice, and its relations to that of the glacial epoch

ABSTRACT At a time when nobody has yet landed on the Antarctic continent (1879), this presentation and accompanying paper predicts the morphology, dynamics and thermal regime of the Antarctic ice sheet. Mathematical modelling of the ice sheet is based on the assumptions that the thickness of tabular icebergs reflects the average thickness of the ice at the margin and that the surface gradients are comparable to those of reconstructed former ice sheets in the Northern Hemisphere. The modelling shows that (a) ice is thickest near the centre at the South Pole and thins towards the margin; (b) the thickness at the pole is independent of the amount of snowfall at that place; and (c) the mean velocity at the margin, assuming a mean annual snowfall of two inches per year, is 400–500 feet per year. The thermal regime of the ice sheet is influenced by three heat sources – namely, the bed, the internal friction of ice flow and the atmosphere. The latter is the most significant and, since ice has a downwards as well as horizontal motion, this carries cold ice down into the ice sheet. Since the temperature at which ice melts is lowered by pressure at a rate of 0.0137 °F for every atmosphere of pressure (something known since 1784), much of the ice sheet and its base must be below the freezing point. Estimates of the thickness of ice at the centre depend closely on the surface gradients assumed and range between 3 and 24 miles. Such uncertainty is of concern since both the volume and gravitational attraction of the ice mass have an effect on global sea level. In order to improve our estimate of the volume of ice, we will have to wait 76 years for John Glen to develop a realistic flow law for ice.

Cosmic connections: James Croll's influence on his contemporaries and his successors

ABSTRACT This paper examines the astronomical theory of ice ages of James Croll (1821–1890), its influence on contemporaries John Tyndall, Charles Lyell, and Charles Darwin, and the subsequent development of climate change science, giving special attention to the work of Svante Arrhenius, Nils Ekholm, and G. S. Callendar (for the carbon dioxide theory), and Milutin Milanković (for the astronomical theory). Croll's insight that the orbital elements triggered feedbacks leading to complex changes – in seasonality, ocean currents, ice sheets, radiative forcing, plant and animal life, and climate in general – placed his theory of the Glacial Epoch at the nexus of astronomy, terrestrial physics, and geology. He referred to climate change as the most important problem in terrestrial physics, and the one which will ultimately prove the most far reaching in its consequences. He was an autodidact deeply involved in philosophy and an early proponent of what came to be called ‘cosmic physics’ – later known as ‘Earth-system science.’ Croll opened up new dimensions of the ‘climate controversy’ that continue today in the interplay of geological and human influences on climate.

Exhumed fjords of Namibia: A glimpse of the Late Paleozoic Ice Age in the Karoo Supergroup of the Kaokoland basin

<p>The Late Paleozoic Ice Age (LPIA) is the longest-lived and most extreme glacial period (from ca 360 to 260 Ma) of the Phanerozoic. Over this time span, ice masses are thought to have covered most of Gondwana, from South America to Australia. In southern Africa, the sedimentary, stratigraphic and geomorphic evidence of this glaciation is recorded in the Karoo Supergroup. The Kaokoland region of northern Namibia is characterized by a dense network of deep (200-700 m), large (5-15 km) and U-shaped incised valleys formed during the LPIA (Martin, 1981). A recent reappraisal of the morphology and sedimentary infill of these outstanding geomorphic features attests of their glacial origin. Valley flanks are spectacularly striated and scratched while valley floors are characterized by extensive whalebacks and roches moutonnées. Moreover, the sedimentary infill at the base of these valleys is mainly composed of coarse deposits (conglomerates, diamictites, erratics, striated clasts) interpreted as glaciogenic in origin. Of particular interest, however, is the presence of coarse (ranging from sand to boulders) glaciogenic sediments plastered on the sub-vertical and striated valley sides. Vitally, the elevation of these deposits in the valleys appears to correspond to a linear bench-like level, which may reflect a marginal moraine allowing for the maximum thickness of the LPIA glaciers to be derived, an unprecedented advance. For the first time in the characterization of a pre-Pleistocene glacial epoch, an ice thickness has been inferred. Collectively, these features prove that the valleys were carved and occupied by ice masses during the LPIA from which ice volume, and in turn their contribution to global eustasy, can directly be inferred. In addition, postglacial sedimentary succession abutting on valley flanks and showcasing marine, deltaic and estuarine affinities clearly indicate that these glacial valleys formed fjords in the immediate aftermath of the LPIA, after the retreat of the ice margins. Sealed by the Karoo Supergroup sediments through Carboniferous to early Cretaceous times, these major glaciogenic morphologic features have subsequently been exhumed during the Cenozoic. Thus, some desertic landscapes of northern Namibia correspond to a glacial relief inherited from the LPIA at ca ~ 300 Myr ago.</p><p> </p><p>Martin, H., 1981, The Late Paleozoic Dwyka Group of the South Kalahari Basin in Namibia and Botswana and the subglacial valleys of the Kaokoveld in Namibia, in Hambrey, M.J., and Harland, W.B. (eds.) Earth’s Pre-Pleistocene Glacial Record: New York, Cambridge University Press, 61–66</p>