Background selection is a process whereby recurrent deleterious mutations cause a decrease in the effective population size and genetic diversity at linked loci. Several authors have suggested that ...variation in the intensity of background selection could cause variation in FST across the genome, which could confound signals of local adaptation in genome scans. We performed realistic simulations of DNA sequences, using recombination maps from humans and sticklebacks, to investigate how variation in the intensity of background selection affects FST and other statistics of population differentiation in sexual, outcrossing species. We show that, in populations connected by gene flow, Weir and Cockerham's (1984; Evolution, 38, 1358) estimator of FST is largely insensitive to locus‐to‐locus variation in the intensity of background selection. Unlike FST, however, dXY is negatively correlated with background selection. Moreover, background selection does not greatly affect the false‐positive rate in FST outlier studies in populations connected by gene flow. Overall, our study indicates that background selection will not greatly interfere with finding the variants responsible for local adaptation.
The New Worlds of Thomas Robert Malthusis a sweeping global and intellectual history that radically recasts our understanding of Malthus'sEssay on the Principle of Population, the most famous book on ...population ever written or ever likely to be. Malthus'sEssayis also persistently misunderstood. First published anonymously in 1798, theEssaysystematically argues that population growth tends to outpace its means of subsistence unless kept in check by factors such as disease, famine, or war, or else by lowering the birth rate through such means as sexual abstinence.
Challenging the widely held notion that Malthus'sEssaywas a product of the British and European context in which it was written, Alison Bashford and Joyce Chaplin demonstrate that it was the new world, as well as the old, that fundamentally shaped Malthus's ideas. They explore what the Atlantic and Pacific new worlds-from the Americas and the Caribbean to New Zealand and Tahiti-meant to Malthus, and how he treated them in hisEssay. Bashford and Chaplin reveal how Malthus, long vilified as the scourge of the English poor, drew from his principle of population to conclude that the extermination of native populations by European settlers was unjust.
Elegantly written and forcefully argued,The New Worlds of Thomas Robert Malthusrelocates Malthus'sEssayfrom the British economic and social context that has dominated its reputation to the colonial and global history that inspired its genesis.
Africa is inferred to be the continent of origin for all modern human populations, but the details of human prehistory and evolution in Africa remain largely obscure owing to the complex histories of ...hundreds of distinct populations. We present data for more than 580,000 SNPs for several hunter-gatherer populations: the Hadza and Sandawe of Tanzania, and the not equalKhomani Bushmen of South Africa, including speakers of the nearly extinct N
Investment in health is a strategically important and often underestimated component of economic development. This study sets out a systematic approach to improving health in poor countries. For ...emerging countries, substantially improved health outcomes are a prerequisite to breaking out of the poverty cycle. This book on poverty and health, jointly published by the OECD and WHO, sets out the essential components of a broad-scope “pro-poor” health approach for action within the health system and beyond it. It is for development practitioners in the area of health issues.
Dynamic population mapping using mobile phone data Deville, Pierre; Linard, Catherine; Martin, Samuel ...
Proceedings of the National Academy of Sciences - PNAS,
11/2014, Letnik:
111, Številka:
45
Journal Article
Recenzirano
Odprti dostop
During the past few decades, technologies such as remote sensing, geographical information systems, and global positioning systems have transformed the way the distribution of human population is ...studied and modeled in space and time. However, the mapping of populations remains constrained by the logistics of censuses and surveys. Consequently, spatially detailed changes across scales of days, weeks, or months, or even year to year, are difficult to assess and limit the application of human population maps in situations in which timely information is required, such as disasters, conflicts, or epidemics. Mobile phones (MPs) now have an extremely high penetration rate across the globe, and analyzing the spatiotemporal distribution of MP calls geolocated to the tower level may overcome many limitations of census-based approaches, provided that the use of MP data is properly assessed and calibrated. Using datasets of more than 1 billion MP call records from Portugal and France, we show how spatially and temporarily explicit estimations of population densities can be produced at national scales, and how these estimates compare with outputs produced using alternative human population mapping methods. We also demonstrate how maps of human population changes can be produced over multiple timescales while preserving the anonymity of MP users. With similar data being collected every day by MP network providers across the world, the prospect of being able to map contemporary and changing human population distributions over relatively short intervals exists, paving the way for new applications and a near real-time understanding of patterns and processes in human geography.
Understanding the mechanisms underlying population decline is a critical challenge for conservation biologists. Both deterministic (e.g. habitat loss, fragmentation, and Allee effect) and stochastic ...(i.e. demographic and environmental stochasticity) demographic processes are involved in population decline. Simultaneously, a decrease of population size has far-reaching consequences for genetics of populations by increasing the risk of inbreeding and the strength of genetic drift, which together inevitably results in a loss of genetic diversity and a reduced effective population size (
N
e
). These genetic factors may retroactively affect vital rates (a phenomenon coined ‘inbreeding depression’), reduce population growth, and accelerate demographic decline. To date, most studies that have examined the demographic and genetic processes driving the decline of wild populations have neglected their spatial structure. In this study, we examined demographic and genetic factors involved in the decline of a spatially structured population of a lekking bird, the western capercaillie (
Tetrao urogallus
). To address this issue, we collected capture-recapture and genetic data over a 6-years period in the Vosges Mountains (France). Our study showed that the population of
T. urogallus
experienced a severe decline between 2010 and 2015. We did not detect any Allee effect on survival and recruitment. By contrast, individuals of both sexes dispersed to avoid small subpopulations, thus suggesting a potential behavioral response to a mate finding Allee effect. In parallel to this demographic decline, the population showed low levels of genetic diversity, high inbreeding and low effective population sizes at both subpopulation and population levels. Despite this, we did not detect evidence of inbreeding depression: neither adult survival nor recruitment were affected by individual inbreeding level. Our study underlines the benefit from combining demographic and genetic approaches to investigate processes that are involved in population decline.
Populations of many bumblebee species are declining, with distributions shifting northwards to track suitable climates. Climate change is considered a major contributing factor. Arctic species are ...particularly vulnerable as they cannot shift further north, making assessment of their population viability important. Analysis of levels of whole‐genome variation is a powerful way to analyse population declines and fragmentation. Here, we use genome sequencing to analyse genetic variation in seven species of bumblebee from the Scandinavian mountains, including two classified as vulnerable. We sequenced 333 samples from across the ranges of these species in Sweden. Estimates of effective population size (NE) vary from ~55,000 for species with restricted high alpine distributions to 220,000 for more widespread species. Population fragmentation is generally very low or undetectable over large distances in the mountains, suggesting an absence of barriers to gene flow. The relatively high NE and low population structure indicate that none of the species are at immediate risk of negative genetic effects caused by high levels of genetic drift. However, reconstruction of historical fluctuations in NE indicates that the arctic specialist species Bombus hyperboreus has experienced population declines since the last ice age and we detected one highly inbred diploid male of this species close to the southern limit of its range, potentially indicating elevated genetic load. Although the levels of genetic variation in montane bumblebee populations are currently relatively high, their ranges are predicted to shrink drastically due to the effects of climate change and monitoring is essential to detect future population declines.
The strengths of families from culture to culture, when compared to each other, are remarkably similar and give us common ground around the world upon which to unite and develop mutual understanding. ...Strengths-Based Research and Perspectives: Strong Families Around the World , provides a conceptual framework for global family strengths, discussing the diverse strengths and challenges that families face regardless of location. This book presents 43 expert authors from 18 countries in all seven major areas in the world who explain what it means to be a family in the context of their country and the challenges their country faces in the world today.
Focusing on the latest studies of similarities between strong families of different cultures, Strengths-Based Research and Perspectives: Strong Families Around the World presents a wide variety of disciplines, including family studies, family education, family therapy, modern languages, psychology, social work, sociology, cultural anthropology, and nursing. This insightful text centers on the Family Strengths Perspective, a paradigm that not only recognizes that there are problems in families today, but demonstrates clearly how these can be dealt with successfully. This valuable resource provides case study examples, quotations from literature and cultural mythology, tables, figures, and extensive references to give readers an in-depth understanding of the issues from strengths-based perspectives.
Topics in Strengths-Based Research and Perspectives: Strong Families Around the World include:
an introduction into the Family Strengths Perspective
the International Family Strengths Model
the propositions of the Family Strengths Perspective
how the Family Strengths Perspective fits with other conceptual frameworks
families from a global perspective
a conceptual framework for understanding global family strengths and challenges
Strengths-Based Research
Human activity is a major driver of change and has contributed to many of the challenges we face today. Detailed information about human population distribution is fundamental and use of freely ...available, high-resolution, gridded datasets on global population as a source of such information is increasing. However, there is little research to guide users in dataset choice. This study evaluates five of the most commonly used global gridded population datasets against a high-resolution Swedish population dataset on a pixel level. We show that datasets which employ more complex modeling techniques exhibit lower errors overall but no one dataset performs best under all situations. Furthermore, differences exist in how unpopulated areas are identified and changes in algorithms over time affect accuracy. Our results provide guidance in navigating the differences between the most commonly used gridded population datasets and will help researchers and policy makers identify the most suitable datasets under varying conditions.
Early life‐cycle events play critical roles in determining the population and community dynamics of plants. The ecology of seeds and their germination patterns can determine range limits, adaptation ...to environmental variation, species diversity, and community responses to climate change. Understanding the adaptive consequences and environmental filtering of such functional traits will allow us to explain and predict ecological dynamics. Here we quantify key functional aspects of germination physiology and relate them to an existing functional ecology framework to explain long‐term population dynamics for 13 species of desert annuals near Tucson, Arizona, USA. Our goal was to assess the extent to which germination functional biology contributes to long‐term population processes in nature. Some of the species differences in base, optimum, and maximum temperatures for germination, thermal times to germination, and base water potentials for germination were strongly related to 20‐yr mean germination fractions, 25‐yr average germination dates, seed size, and long‐term demographic variation. Comparisons of germination fraction, survival, and fecundity vs. yearly changes in population size found significant roles for all three factors, although in varying proportions for different species. Relationships between species’ germination physiologies and relative germination fractions varied across years, with fast‐germinating species being favored in years with warm temperatures during rainfall events in the germination season. Species with low germination fractions and high demographic variance have low integrated water‐use efficiency, higher vegetative growth rates, and smaller, slower‐germinating seeds. We have identified and quantified a number of functional traits associated with germination biology that play critical roles in ecological population dynamics.
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