ALBERT

Description: Scattered groups of these ancient fish may all stem from a single remote population. Coelacanths were discovered in the Comoros archipelago to the northwest of Madagascar in 1952. Since then, these rare, ancient fish have been found to the south off Mozambique, Madagascar and South Africa, and to the north off Kenya and Tanzania — but it was unclear whether these are separate populations or even subspecies. Here we show that the genetic variation between individuals from these different locations is unexpectedly low. Combined with earlier results from submersible and oceanographic observations1, 2, our findings indicate that a separate African metapopulation is unlikely to have existed and that locations distant from the Comoros were probably inhabited relatively recently by either dead-end drifters or founders that originated in the Comoros.

Description: By combining the lithologic, original palynologic and published micropaleonthological data we reconstructed paleogeographical events On the Pechora shelf during the Younger Dryas and Holocene time. Our paleoenvironmental reconstructions are based On the regularities in formation of pollen-and-spores assemblages in the surface sediments of the Pechora Sea. The main stages in paleogeography of the Pechora Sea during the Late Pleistocene were emphasized. The Late Valdai sediments in the Pechora Sea region were accumulated under the influence of fluvioglacial flows probably from the melting ice cap on Kolguev Island and, also, coastal glaciers. Climate deterioration considerably changed coastal vegetation as reflected in the depleted taxonomic and quantitative composition of palynospectra. The pollen data suggest that Open steppe-like plant communities with Artemisia, Poaceae, Asteraceae and Caryophyllaceae dominated dry ecotopes On watersheds, whereas tundra-like communities with Betula nana, arctic Salix, Dryas, Saxifraga, Carex and Brassicaceae were common in more humid coastal lowlands. The overlying silts and loamy sands are believed to have been accumulated during early deglaciation, i.e., Older Dryas and Alleröd. During this phase the glacial sedimentation was rather rapidly replaced by a glaciomarine deposition. Progressive climate warming caused prominent changes in coastal vegetation. Discontinuous treeless tundra-steppe associations were replaced by dwarf and shrub ernik tundra. A "complex vegetation cover" of forest-tundra apparently existed in the northern part of the Kola Peninsula and in the Northern Dvina Lowland. By the end of the Alleröd alder-bushes and horsetails occupied riverbanks, and spruce occurred in the forest-tundra communities on the adjacent hinterland.

Description: More reliable reconstructions of the Late Quaternary glacial history of the Pechora Sea have been carried out due to new radiocarbon datings. The bulk of evidence favors the view that complete deglaciation of the Pechora Sea occurred in the middle Valdai epoch, about 35-40 ka. After a short interstadial period with normal marine conditions, sea-level fall gave rise to establishment of continental environments. In the late Valdai, the Novaya Zemlya ice sheet occupied only the northernmost Pechora Sea and did not reach the Pechora Lowland. In the Course of the subsequent Holocene transgression, the shelf was abraded. Modern lithodynamic conditions in the Pechora Sea determine accumulation of sandy-silty deposits.

Description: The article discusses the main results of the complex investigations of barrier beaches in the Pechora Sea including coastal dynamics and accompanying exogenous processes (eolian transportation), lithological and micropaleontological studies of the sediment sequence and radiocarbon dating. We were the first to reconstruct sedimentation conditions and evolution of these big accumulative forms in the Pechora Sea. Stationary observations on coastal dynamics and the rate of eolian sedimentation allowed estimating the rate of barrier retreat. The mechanism of formation and evolution of dune belts on these barriers is described. Composition of diatom associations and lithological data provide evidence for facial-genetic conditions of sedimentation during accumulation of barriers. Radiocarbon datings corroborate the "young" age of the modern avandune ridges of the barrier beaches.

Description: In the context of gradual Cenozoic cooling, the timing of the onset of significant Northern Hemisphere glaciation 2.7 million years ago is consistent with Milankovitch's orbital theory, which posited that ice sheets grow when polar summertime insolation and temperature are low. However, the role of moisture supply in the initiation of large Northern Hemisphere ice sheets has remained unclear. The subarctic Pacific Ocean represents a significant source of water vapour to boreal North America, but it has been largely overlooked in efforts to explain Northern Hemisphere glaciation. Here we present alkenone unsaturation ratios and diatom oxygen isotope ratios from a sediment core in the western subarctic Pacific Ocean, indicating that 2.7 million years ago late-summer sea surface temperatures in this ocean region rose in response to an increase in stratification. At the same time, winter sea surface temperatures cooled, winter floating ice became more abundant and global climate descended into glacial conditions. We suggest that the observed summer warming extended into the autumn, providing water vapour to northern North America, where it precipitated and accumulated as snow, and thus allowed the initiation of Northern Hemisphere glaciation.

Description: Sexual mimicry among animals is widespread, but does it impart a fertilization advantage in the widely accepted ‘sneak–guard’ model of sperm competition? Here we describe field results in which a dramatic facultative switch in sexual phenotype by sneaker-male cuttlefish leads to immediate fertilization success, even in the presence of the consort male. These results are surprising, given the high rate at which females reject copulation attempts by males, the strong mate-guarding behaviour of consort males, and the high level of sperm competition in this complex mating system