In many species of animals, females typically mate with more than one male (polyandry) Some social insects carry this behaviour to extremes1 For example, honeybee queens mate with ten to twenty (or even more) males on their nuptial flights2 The reasons for this behaviour remain unknown, given the obvious costs of time, energy and exposure to predation Several potential benefits of polyandry have been proposed1,3,3,4, but none are well supported yet Here we test the hypothesis that genetic diversity among a female's offspring may offer some protection from parasitism5,6,7 We artificially inseminated queens of a bumble-bee (Bombus terrestris L) with sperm of either low or high genetic diversity The resulting colonies were exposed to parasitism under field conditions High-diversity colonies had fewer parasites and showed greater reproductive success, on average, than did low-diversity colonies We suggest that female mating frequency may be influenced in part by parasites

Experimental variation in polyandry affects parasite loads and fitness in a bumble-bee

The first opening of the Bering Strait was an important palaeogeographical and biogeographical event for marine and terrestrial biotas in Asia and North America1,2,3, and an oceanographic event of global importance4,5,6. This event, however, has never been precisely dated, so it has not been accurately incorporated into models of global biogeography and oceanography. A recent find of the bivalve mollusc Astarte in southern Alaska is a clear signal that the strait had opened by at least the Late Miocene or earliest Pliocene epochs, because this genus otherwise dwelled only in the Arctic and North Atlantic oceans at that time1,2. Here we show that marine diatoms with Astarte are correlative with subzone b of the Neodenticula kamtschatica zone of the North Pacific diatom biochronology, yielding an age range of 4.8–5.5 Myr (refs 7, 8). Stratigraphic information suggests that this may be a minimum age range for the strait's first opening, which evidently occurred between 4.8 and 7.3–7.4 Myr ago. Our results contrast with past studies9,10,11,12,13 that suggested an age of 3.1–4.1 Myr for the initial opening of the Bering Strait.

Evidence for an early opening of the Bering Strait

A refined age for the earliest opening of Bering Strait

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. ABSTRACT The Phanerozoic tectonic evolution of the Circum-North Pacific is recorded mainly in the erogenic collages of the Circum-North Pacific mountain belts that separate the North Pacific from the eastern North Asian and western North American Cratons. The collages consist of tectonostratigraphic terranes, composed of fragments of igneous arcs, accretionary-wedge and subduction-zone complexes, passive continental margins, and cratons, that are overlapped by continental margin arc and sedimentary basin assemblages. The geologic history of terranes and overlap assemblages is highly complicated because of post-accretion dismemberment and translation during strike-slip faulting that occurred subparallel to continental margins. The complex tectonics of this region is analyzed by the following steps. (1) Tectonic environments for the erogenic collage are assigned from regional compilation and synthesis of stratigraphic and faunal data. The tectonic environments include cratonal, passive continental margin, metamorphosed continental margin, continental-margin arc, island arc; oceanic crust, seamount, and ophiolite, accretionary wedge and subduction zone, turbidite basin, and metamorphic. (2) Correlations are made between terranes. (3) Coeval terranes are grouped into a single tectonic origin, i.e., a single island arc or subduction zone. (4) Igneous arc and subduction zone terranes, that are interpreted as being tectonically linked, are grouped into coeval, curvilinear arc-subduction zone complexes. (5) By use of geologic, faunal, and paleomagnetic data, the original positions of terranes are interpreted. And (6) the paths of tectonic migration are constructed. Six processes overlapping in time were responsible for most of the complexities of the collage of terranes and overlap assemblages around the Circum-North Pacific. First, in the Late Proterozoic, and the Late Devonian and Early Carboniferous, major periods of rifting occurred along the margins of Northeast Asia and northwestern part of the North American Cordillera. The rifting resulted in fragmentation and formation of cratonal and passive continental margin terranes from each continent that eventually migrated and accreted to other sites along the evolving margins of the original or adjacent continents. Second, from about the Late Triassic through the mid-Cretaceous, a succession of island arcs and tectonically paired subduction zones formed near continental margins. Third, from about mainly the mid-Cretaceous through the Present, a succession of igneous arcs and …

Phanerozoic tectonic evolution of the circum-north Pacific

..........................................................................................................................................................1 Chapter 1. The 1912 Eruption and its Importance ....................................................................................3 Overview of the Eruption ........................................................................................................3 Volcanological Significance of the 1912 Eruption ..............................................................3 Chapter 2. The Context of the 1912 Eruption ..........................................................................................13 Geographic Setting ...............................................................................................................13 Cultural Setting: Katmai Before 1912 .................................................................................13 Cultural Setting: The World in 1912 ....................................................................................14 Scientific Context of the Early Katmai Investigations .....................................................15 Geologic Setting of the Katmai Volcano Cluster ..............................................................17 Chapter 3. 1912 Eruption Narrative: What Was Actually Recorded in 1912 ......................................19 Chronology of Observations in 1912 ...................................................................................19 Environmental Impact of the Eruption ...............................................................................22 Recovery of Flora and Fauna ...............................................................................................22 Chapter 4. History of Investigations and Interpretations .....................................................................25 Chronology of Geologic Investigations at Katmai ............................................................25 Principal Contributors to the Early Geologic Investigations at Katmai ........................42 Chapter 5. Products of the 1912 Eruption ................................................................................................45 Eruptive Episode I ..................................................................................................................48 Layer A ...........................................................................................................................49 All-Rhyolite Ignimbrite .................................................................................................51 Layer B ...........................................................................................................................56 Compositionally Heterogeneous (Main) Valley-Filling Ignimbrite (VFI) ...............57 Compositionally Heterogeneous High-Energy Proximal Ignimbrite (HEPI) ........62 Time Constraints for Episode I ...................................................................................66 Eruptive Episodes II and III ..................................................................................................68 Layer C............................................................................................................................70 Layer D ...........................................................................................................................71 Layer E ............................................................................................................................71 Layer F ............................................................................................................................73 Layer G ...........................................................................................................................74 Layer H ...........................................................................................................................76 Proximal Pyroclastic Density Currents .....................................................................77 Proximal Fall Deposits: Contrasting Facies ..............................................................77 Eruptive Episode IV: Dacitic Phantom Dome and Block Bed .........................................78 Eruptive Episode V: Novarupta Rhyolite Dome .................................................................80 Chapter 6. Volcanological Aspects of the Primary Eruption Products ..............................................87 Volumes Erupted ....................................................................................................................87 Coignimbrite Ash and Coplinian Ash ..................................................................................87

/pdf/the-novarupta-katmai-eruption-of-1912-largest-eruption-of-2ivrhzqmnh.pdf

The Novarupta-Katmai eruption of 1912 - largest eruption of the twentieth century; centennial perspectives

Stratigraphic framework of the Alaska Peninsula

/pdf/the-alaska-peninsula-terrane-a-definition-2gm7q47r8m.pdf

The Alaska Peninsula terrane; a definition

Geologic map of the Ugashik, Bristol Bay, and western part of Karluk quadrangles, Alaska

/pdf/the-alaska-mineral-resource-assessment-program-background-1ss1vn1faa.pdf

The Alaska Mineral Resource Assessment Program; background information to accompany folio of geologic and resource maps of the Ugashik, Bristol Bay, and western part of Karluk quadrangles, Alaska

Generalized geologic map of the Ugashik, Bristol Bay and part of Karluk quadrangles, Alaska

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