Research about Iceland, United States

USGS2019

Development and characterization of polymorphic microsatellite markers in Northern Fulmar, Fulmarus glacialis (Procellariformes), and cross-species amplification in eight other seabirds

Background In the North Pacific, northern fulmar ( Fulmarus glacialis ) forms extensive colonies in few locales, which may lead to limited gene flow and locale-specific population threats. In the Atlantic, there are thousands of colonies of varying sizes and in Europe the species is considered threatened. Prior screens and classical microsatellite development in fulmar failed to provide a suite of markers adequate for population genetics studies. Objectives The objective of this study was to isolate a suite of polymorphic microsatellite loci with sufficient variability to quantify levels of gene flow, population affinity, and identify familial relationships in fulmar. We also performed a cross-species screening of these markers in eight other species. Methods We used shotgun sequencing to isolate 26 novel microsatellite markers in fulmar to screen for variability using individuals from two distinct regions: the Pacific (Chagulak Island, Alaska) and the Atlantic (Hafnarey Island, Iceland). Results Polymorphism was present in 24 loci in Chagulak and 23 in Hafnarey, while one locus failed to amplify in either colony. Polymorphic loci exhibited moderate levels of genetic diversity and this suite of loci uncovered genetic structuring between the regions. Among the other species screened, polymorphism was present in one to seven loci. Conclusion The loci yielded sufficient variability for use in population studies and estimation of familial relationships; as few as five loci provide resolution to determine individual identity. These markers will allow further insight into the global population dynamics and phylogeography of fulmars. We also demonstrated some markers are transferable to other species.

Alaska↗

USGS1971

Plate tectonics and magmatic evolution

The validity of the general idea of plate tectonics is accepted; the magmas evolved along the spreading ridges are thought to be largely tholeiitic basalt, although alkalic olivine basalt and ultramafic rocks of several kinds have also been dredged from them. The ultramafics may be residual from the partial melting of pyrolite while the tholeiite was being formed at shallower depths, or they may possibly be fragments of the mantle raised by the injection of sills. Bouvet and Jan Mayen Islands, both on the crest of the Mid-Atlantic Ridge, are largely composed of alkali basalt with very minor differentiates of trachyte and even rhyolite that may be readily accounted for by differentiation at a high level in the volcanic edifice. Iceland, though, has so much granite and rhyolite widely distributed that it seems likely, as suggested by several students, that its basement is sialic. The volcanic islands tend to be more alkalic the farther they are from the ridges; perhaps they rose from deeper sources in areas of low heat flow and are not related to plate margins. If the African Rifts are incipient plate margins, it is noteworthy that the magmas associated with them are wholly different from the tholeiites of the oceanic ridges. They are among the most highly alkaline of any rocks known. The magmatic activity at the subduction zones, where the plates are being destroyed, is very different. There are three varieties of these plate junctions: continental against oceanic, oceanic against oceanic, and continental against continental. In both the junctions involving oceanic crust the material being consumed includes a variable thickness of sediment, underlain by 5 or 6 km of tholeiitic basalt overlying the downgoing mantle. These rocks are much less refractory than the pyrolite of the mantle and must surely compose a large part of material parental to the magmas formed along the subduction zones, the andesites, granodiorites, and granites. There is nowhere the tremendous volume of intermediate rocks that would have had to be formed if these voluminous magmas had been products of crystallization differentiation from a basaltic magma. The presently most active of the continent-continent junctions is along the Himalayas where India is underthrusting the continent of Asia; here there is no evidence of magmatism except along the transcurrent faults at either end of the main range. But there are large volcanic and plutonic masses that have no obvious relation to the plate boundaries active in Mesozoic and Cenozoic time. The Eogene volcanics of the San Juans and the Neogene volcanics of the Yellowstone are more than 1,500 km from any obvious subduction zone, and these regions of magmatic activity seem no more closely related to subduction zones than are the Tertiary igneous rocks of West Texas, the Cretaceous tuffs and plutons of Arkansas, the Cretaceous intrusives of the Monteregian Hills, and the minor Tertiary intrusives of Virginia.

Washington↗