scholarly journals Unexpected heterozygosity in an island mouflon population founded by a single pair of individuals

2006 ◽  
Vol 274 (1609) ◽  
pp. 527-533 ◽  
Author(s):  
Renaud Kaeuffer ◽  
David W Coltman ◽  
Jean-Louis Chapuis ◽  
Dominique Pontier ◽  
Denis Réale
Keyword(s):  
Genetic Diversity ◽  
Wild Population ◽  
Ovis Aries ◽  
Stochastic Simulations ◽  
Single Pair ◽  
Small Populations ◽  
Short Period ◽  
Large Populations ◽  
History Of ◽  
Over Time

In population and conservation genetics, there is an overwhelming body of evidence that genetic diversity is lost over time in small populations. This idea has been supported by comparative studies showing that small populations have lower diversity than large populations. However, longitudinal studies reporting a decline in genetic diversity throughout the whole history of a given wild population are much less common. Here, we analysed changes in heterozygosity over time in an insular mouflon ( Ovis aries ) population founded by two individuals in 1957 and located on one of the most isolated locations in the world: the Kerguelen Sub-Antarctic archipelago. Heterozygosity measured using 25 microsatellite markers has actually increased over 46 years since the introduction, and exceeds the range predicted by neutral genetic models and stochastic simulations. Given the complete isolation of the population and the short period of time since the introduction, changes in genetic variation cannot be attributed to mutation or migration. Several lines of evidence suggest that the increase in heterozygosity with time may be attributable to selection. This study shows the importance of longitudinal genetic surveys for understanding the mechanisms that regulate genetic diversity in wild populations.

scholarly journals The pattern of neutral molecular variation under the background selection model.

Genetics ◽  
1995 ◽  
Vol 141 (4) ◽  
pp. 1619-1632 ◽  
Author(s):  
D Charlesworth ◽  
B Charlesworth ◽  
M T Morgan
Keyword(s):  
Genetic Diversity ◽  
Genomic Region ◽  
Stochastic Simulations ◽  
Background Selection ◽  
Effective Population ◽  
Frequency Spectra ◽  
Low Genetic Diversity ◽  
Neutral Locus ◽  
Large Populations ◽  
Site Diversity

Abstract Stochastic simulations of the infinite sites model were used to study the behavior of genetic diversity at a neutral locus in a genomic region without recombination, but subject to selection against deleterious alleles maintained by recurrent mutation (background selection). In large populations, the effect of background selection on the number of segregating sites approaches the effect on nucleotide site diversity, i.e., the reduction in genetic variability caused by background selection resembles that caused by a simple reduction in effective population size. We examined, by coalescence-based methods, the power of several tests for the departure from neutral expectation of the frequency spectra of alleles in samples from randomly mating populations (Tajima's, Fu and Li's, and Watterson's tests). All of the tests have low power unless the selection against mutant alleles is extremely weak. In Drosophila, significant Tajima's tests are usually not obtained with empirical data sets from loci in genomic regions with restricted recombination frequencies and that exhibit low genetic diversity. This is consistent with the operation of background selection as opposed to selective sweeps. It remains to be decided whether background selection is sufficient to explain the observed extent of reduction in diversity in regions of restricted recombination.

scholarly journals Strongly deleterious mutations are a primary determinant of extinction risk due to inbreeding depression

2019 ◽  
Author(s):  
Christopher C. Kyriazis ◽  
Robert K. Wayne ◽  
Kirk E. Lohmueller
Keyword(s):  
Genetic Diversity ◽  
Inbreeding Depression ◽  
Extinction Risk ◽  
Fragmented Landscape ◽  
Small Populations ◽  
Deleterious Mutations ◽  
Genetic Rescue ◽  
Isolated Populations ◽  
Large Populations ◽  
Source Populations

AbstractHuman-driven habitat fragmentation and loss have led to a proliferation of small and isolated plant and animal populations with high risk of extinction. One of the main threats to extinction in these populations is inbreeding depression, which is primarily caused by the exposure of recessive deleterious mutations as homozygous by inbreeding. The typical approach for managing these populations is to maintain high genetic diversity, often by translocating individuals from large populations to initiate a ‘genetic rescue.’ However, the limitations of this approach have recently been highlighted by the demise of the gray wolf population on Isle Royale, which was driven to the brink of extinction soon after the arrival of a migrant from the large mainland wolf population. Here, we use a novel population genetic simulation framework to investigate the role of genetic diversity, deleterious variation, and demographic history in mediating extinction risk due to inbreeding depression in small populations. We show that, under realistic models of dominance, large populations harbor high levels of recessive strongly deleterious variation due to these mutations being hidden from selection in the heterozygous state. As a result, when large populations contract, they experience a substantially elevated risk of extinction after these strongly deleterious mutations are exposed by inbreeding. Moreover, we demonstrate that although translocating individuals to small populations is broadly effective as a means to reduce extinction risk, using small or moderate-sized source populations rather than large source populations can greatly increase the effectiveness of genetic rescue due to greater purging in these smaller populations. Our findings challenge the traditional conservation paradigm that focuses on maximizing genetic diversity to reduce extinction risk in favor of a view that emphasizes minimizing strongly deleterious variation. These insights have important implications for managing small and isolated populations in the increasingly fragmented landscape of the Anthropocene.Impact SummaryNumerous threats to extinction exist for small populations, including the detrimental effects of inbreeding. Although much of the focus in reducing these harmful effects in small populations has been on maintaining high genetic diversity, here we use simulations to demonstrate that emphasis should instead be placed on minimizing strongly deleterious variation. More specifically, we show that historically-large populations with high levels of genetic diversity also harbor elevated levels of recessive strongly deleterious mutations hidden in the heterozygous state. Thus, when these populations contract, inbreeding can expose these strongly deleterious mutations as homozygous and lead to severe inbreeding depression and rapid extinction. Moreover, we demonstrate that, although translocating individuals to these small populations to perform a ‘genetic rescue’ is broadly beneficial, the effectiveness of this strategy can be greatly increased by targeting historically-smaller source populations where recessive strongly deleterious mutations have been purged. These results challenge long-standing views on how to best conserve small and isolated populations facing the threat of inbreeding depression, and have immediate implications for preserving biodiversity in the increasingly fragmented landscape of the Anthropocene.

The Path of Standard Albanian Language Formation

2018 ◽  
Vol 5 (2) ◽  
pp. 106-115
Author(s):  
Sindorela Doli Kryeziu
Keyword(s):  
Single Unit ◽  
Cultural Factors ◽  
Language History ◽  
Whole Process ◽  
History Of ◽  
Social And Cultural Factors ◽  
Cultural Body ◽  
Over Time ◽  
Language Literature

Abstract In our paper we will talk about the whole process of standardization of the Albanian language, where it has gone through a long historical route, for almost a century.When talking about standard Albanian language history and according to Albanian language literature, it is often thought that the Albanian language was standardized in the Albanian Language Orthography Congress, held in Tirana in 1972, or after the publication of the Orthographic Rules (which was a project at that time) of 1967 and the decisions of the Linguistic Conference, a conference of great importance that took place in Pristina, in 1968. All of these have influenced chronologically during a very difficult historical journey, until the standardization of the Albanian language.Considering a slightly wider and more complex view than what is often presented in Albanian language literature, we will try to describe the path (history) of the standard Albanian formation under the influence of many historical, political, social and cultural factors that are known in the history of the Albanian people. These factors have contributed to the formation of a common state, which would have, over time, a common standard language.It is fair to think that "all activity in the development of writing and the Albanian language, in the field of standardization and linguistic planning, should be seen as a single unit of Albanian culture, of course with frequent manifestations of specific polycentric organization, either because of divisions within the cultural body itself, or because of the external imposition"(Rexhep Ismajli," In Language and for Language ", Dukagjini, Peja, 1998, pp. 15-18.)

Stepping up detection, response, preparedness and readiness measures for “COVID-19”- A Pandemic

2020 ◽  
Vol 11 (SPL1) ◽  
pp. 1042-1047
Author(s):  
Khushbu Balsara ◽  
Deepankar Shukla
Keyword(s):  
Health Care ◽  
Health Care Workers ◽  
Clinical History ◽  
Frontline Workers ◽  
Diagnostic Assays ◽  
Care Workers ◽  
Short Period ◽  
History Of ◽  
Detection Response ◽  
Care Worker

In a very short period of time, “COVID-19” has seized the consciousness globally by making remarkable changes in our day to day living and has superintended as a public health emergency globally. It has high radar of transmission, affecting an individual at work to frontline workers. The measures and planning for a response plays a key role from drawing up an emergency committee and this follows an equation which broadly deals with epidemiological to clinical history of the patient, management steps from isolation, screening, diagnostic assays for identification and treatment. The application of an organized plan with secure structure aids in better performance, increases efficacy of management and saves time. Also saves time for a health care worker to g through routine levels of channels of administration if already a familiar way of operation is known for such situations. Thus, planning and developing a ‘blueprint of approach’ towards management of patient while facing such situation is a must. This review provides an insight to the measures for detection, response and preparedness of the hospital and health care workers should largely be inclusive of; also highlights the measures to be taken at every step after coming in contact with a positive case of “COVID-19”.

“The last chord of the Silver Age”: science and culture in Crimea in 1920

2020 ◽  
Vol 2020 (10-4) ◽  
pp. 4-14
Author(s):  
Vladimir Kalinovsky ◽  
Alexander Puchenkov
Keyword(s):  
Civil War ◽  
The South ◽  
Silver Age ◽  
Russian Culture ◽  
Short Period ◽  
The Crimea ◽  
Science And Culture ◽  
History Of ◽  
Russian Intelligentsia

This article is devoted to the development of science and culture in the short period of the Wrangel Crimea - 1920. At this time, the brightest figures of Russian culture of that time worked on the territory of the small Peninsula: O. E. Mandelstam, M. A. Voloshin, B.D. Grekov, G.V. Vernadsky, V.I. Vernadsky and others. The article provides an overview of the life and activities of the Russian intelligentsia in 1920 in the Crimea, based on materials of periodicals as the most important source for studying the history of the Civil war in the South of Russia whose value is to be fully evaluated.

Transocean and the History of Tax Inversions

2018 ◽  
Vol 34 (1) ◽  
pp. 1-12
Author(s):  
Susan M. Albring ◽  
Randal J. Elder ◽  
Mitchell A. Franklin
Keyword(s):  
Multinational Corporations ◽  
Economic Impacts ◽  
Income Taxes ◽  
Tax Rates ◽  
Corporate Tax ◽  
Corporate Income Taxes ◽  
History Of ◽  
Jobs Act ◽  
The U.S ◽  
Over Time

ABSTRACT The first tax inversion in 1983 was followed by small waves of subsequent inversion activity, including two inversions completed by Transocean. Significant media and political attention focused on transactions made by U.S. multinational corporations that were primarily designed to reduce U.S. corporate income taxes. As a result, the U.S. government took several actions to limit inversion activity. The Tax Cuts and Jobs Act of 2017 (TCJA) significantly lowered U.S. corporate tax rates and one expected impact of TCJA is a reduction of inversion activity. Students use the Transocean inversions to understand the reasons why companies complete a tax inversion and how the U.S. tax code affects inversion activity. Students also learn about the structure of inversion transactions and how they have changed over time as the U.S. government attempted to limit them. Students also assess the tax and economic impacts of inversion transactions to evaluate tax policy.

Historical Representations and Recent Changes

2018 ◽  
Author(s):  
Jürgen Schaflechner
Keyword(s):  
Comparative Analysis ◽  
South Asia ◽  
Oral Histories ◽  
Detailed History ◽  
Modern Times ◽  
History Of ◽  
Historical Representations ◽  
The Rich ◽  
Many Sources ◽  
Over Time

Chapter 3 introduces the tradition of ritual journeys and sacred geographies in South Asia, then hones in on a detailed history of the grueling and elaborate pilgrimage attached to the shrine of Hinglaj. Before the construction of the Makran Coastal Highway the journey to the Goddess’s remote abode in the desert of Balochistan frequently presented a lethally dangerous undertaking for her devotees, the hardships of which have been described by many sources in Bengali, Gujarati, Hindi, Sindhi, and Urdu. This chapter draws heavily from original sources, including travelogues and novels, which are supplanted with local oral histories in order to weave a historical tapestry that displays the rich array of practices and beliefs surrounding the pilgrimage and how they have changed over time. The comparative analysis demonstrates how certain motifs, such as austerity (Skt. tapasyā), remain important themes within the whole Hinglaj genre even in modern times while others have been lost in the contemporary era.

Introduction

2018 ◽  
Author(s):  
Marko Geslani
Keyword(s):  
Comparative Study ◽  
Royal Power ◽  
History Of ◽  
Historical Developments ◽  
The Comparative Study ◽  
The Relationship ◽  
Over Time ◽  
Indian Religion

The introduction reviews the historiographic problem of the relation between fire sacrifice (yajña) and image worship (pūjā), which have traditionally been seen as opposing ritual structures serving to undergird the distinction of “Vedic” and “Hindu.” Against such an icono- and theocentric approach, it proposes a history of the priesthood in relation to royal power, centering on the relationship between the royal chaplain (purohita) and astrologer (sāṃvatsara) as a crucial, unexplored development in early Indian religion. In order to capture these historical developments, it outlines a method for the comparative study of ritual forms over time.

Evolutionary genetics of small populations

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Evolutionary Genetics ◽  
Small Population ◽  
Small Populations ◽  
Effective Population ◽  
Genetic Management ◽  
Evolutionary Genetic ◽  
Loss Of Genetic Diversity ◽  
Number Of Individuals

Genetic management of fragmented populations involves the application of evolutionary genetic theory and knowledge to alleviate problems due to inbreeding and loss of genetic diversity in small population fragments. Populations evolve through the effects of mutation, natural selection, chance (genetic drift) and gene flow (migration). Large outbreeding, sexually reproducing populations typically contain substantial genetic diversity, while small populations typically contain reduced levels. Genetic impacts of small population size on inbreeding, loss of genetic diversity and population differentiation are determined by the genetically effective population size, which is usually much smaller than the number of individuals.

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