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Hampton L. Carson Dr. 《GeoJournal》1992,28(2):297-302
Consideration is given to the case of a daughter population of a sexual species that becomes successfully established in an area previously lacking that species, as has occurred recently in the Krakataus. If the new area is isolated geographically and if the number of founder individuals is small, conventional wisdom foresees a reduction of genetic variability within the colony. This might obstruct genetic adjustment to new conditions. Recent studies of the genetics of such bottlenecked populations, however, show that, in some instances, genetic variability for quantitative traits may actually increase rather than decrease after a bottleneck event. Whereas loss of some quasi-neutral biochemical alleles may occur, the quantitative polygenic balances on which adaptation depends can be carried through the bottleneck into the new population. Novel phenotypes may result from natural selection during the generations that immediately follow the bottleneck. Growing shield volcanoes in particular show rapid turnover of their surfaces such that organisms surviving there must continually recolonize or become extinct. Such species, existing as metapopulations, should be prone to bottleneck effects that produce genetic shifts. Examples are given from Drosophila silvestris on the island of Hawaii. The relevance of such genetic shifts to population structure and evolutionary change in populations is discussed, emphasizing the probable role of metapopulation structure. 相似文献
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Elise Brower 《Geochimica et cosmochimica acta》1973,37(1):155-158
Crystals of synthetic barite (BaSO4), celestite (SrSO4), and their solid solutions were recrystallized from brine by thermal cycling. Electron probe microanalyses show that the solid solutions are homogeneous within detection limits. The molar composition of solid solution crystals approximates the ideal value based on the ratio of equilibrium constants for barium and strontium sulfates. 相似文献
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Williamson Daniel Blaker Adam T. Hampton Charlotte Salter James 《Climate Dynamics》2015,45(5-6):1299-1324
Climate Dynamics - We describe the method of history matching, a method currently used to help quantify parametric uncertainty in climate models, and argue for its use in identifying and removing... 相似文献
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Ian A. Crawford Sarah A. Fagents Katherine H. Joy M. Elise Rumpf 《Earth, Moon, and Planets》2010,107(1):75-85
One of the principal scientific reasons for wanting to resume in situ exploration of the lunar surface is to gain access to
the record it contains of early Solar System history. Part of this record will pertain to the galactic environment of the
Solar System, including variations in the cosmic ray flux, energetic galactic events (e.g., supernovae and/or gamma-ray bursts),
and passages of the Solar System through dense interstellar clouds. Much of this record is of astrobiological interest as
these processes may have affected the evolution of life on Earth, and perhaps other Solar System bodies. We argue that this
galactic record, as for that of more local Solar System processes also of astrobiological interest, will be best preserved
in ancient, buried regolith (‘palaeoregolith’) deposits in the lunar near sub-surface. Locating and sampling such deposits
will be an important objective of future lunar exploration activities. 相似文献