Analysis of Rate-Based Pull and Push Strategies with Limited Migration Rates in Large Distributed Networks

Abstract A new Bayesian method that uses individual multilocus genotypes to estimate rates of recent immigration (over the last several generations) among populations is presented. The method also estimates the posterior probability distributions of individual immigrant ancestries, population allele frequencies, population inbreeding coefficients, and other parameters of potential interest. The method is implemented in a computer program that relies on Markov chain Monte Carlo techniques to carry out the estimation of posterior probabilities. The program can be used with allozyme, microsatellite, RFLP, SNP, and other kinds of genotype data. We relax several assumptions of early methods for detecting recent immigrants, using genotype data; most significantly, we allow genotype frequencies to deviate from Hardy-Weinberg equilibrium proportions within populations. The program is demonstrated by applying it to two recently published microsatellite data sets for populations of the plant species Centaurea corymbosa and the gray wolf species Canis lupus. A computer simulation study suggests that the program can provide highly accurate estimates of migration rates and individual migrant ancestries, given sufficient genetic differentiation among populations and sufficient numbers of marker loci.

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Spatial and space-time correlations in systems of subpopulations with genetic drift and migration.

Genetics ◽

10.1093/genetics/133.3.711 ◽

1993 ◽

Vol 133 (3) ◽

pp. 711-727

Author(s):

B K Epperson

Keyword(s):

Population Genetics ◽

Time Correlation ◽

Space Time ◽

Spatial Correlations ◽

Gene Frequencies ◽

Migration Patterns ◽

Migration Rates ◽

Space And Time ◽

Time Correlations ◽

And Migration

Abstract The geographic distribution of genetic variation is an important theoretical and experimental component of population genetics. Previous characterizations of genetic structure of populations have used measures of spatial variance and spatial correlations. Yet a full understanding of the causes and consequences of spatial structure requires complete characterization of the underlying space-time system. This paper examines important interactions between processes and spatial structure in systems of subpopulations with migration and drift, by analyzing correlations of gene frequencies over space and time. We develop methods for studying important features of the complete set of space-time correlations of gene frequencies for the first time in population genetics. These methods also provide a new alternative for studying the purely spatial correlations and the variance, for models with general spatial dimensionalities and migration patterns. These results are obtained by employing theorems, previously unused in population genetics, for space-time autoregressive (STAR) stochastic spatial time series. We include results on systems with subpopulation interactions that have time delay lags (temporal orders) greater than one. We use the space-time correlation structure to develop novel estimators for migration rates that are based on space-time data (samples collected over space and time) rather than on purely spatial data, for real systems. We examine the space-time and spatial correlations for some specific stepping stone migration models. One focus is on the effects of anisotropic migration rates. Partial space-time correlation coefficients can be used for identifying migration patterns. Using STAR models, the spatial, space-time, and partial space-time correlations together provide a framework with an unprecedented level of detail for characterizing, predicting and contrasting space-time theoretical distributions of gene frequencies, and for identifying features such as the pattern of migration and estimating migration rates in experimental studies of genetic variation over space and time.

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Brain drain and brain gain in Russia: Analyzing international migration of researchers by discipline using Scopus bibliometric data 1996–2020

Scientometrics ◽

10.1007/s11192-021-04091-x ◽

2021 ◽

Author(s):

Alexander Subbotin ◽

Samin Aref

Keyword(s):

Brain Drain ◽

Policy Development ◽

Donor Country ◽

International Mobility ◽

Science System ◽

Migration Rates ◽

Net Migration ◽

Novel Approach ◽

Five Disciplines ◽

The Impact

AbstractWe study international mobility in academia, with a focus on the migration of published researchers to and from Russia. Using an exhaustive set of over 2.4 million Scopus publications, we analyze all researchers who have published with a Russian affiliation address in Scopus-indexed sources in 1996–2020. The migration of researchers is observed through the changes in their affiliation addresses, which altered their mode countries of affiliation across different years. While only 5.2% of these researchers were internationally mobile, they accounted for a substantial proportion of citations. Our estimates of net migration rates indicate that while Russia was a donor country in the late 1990s and early 2000s, it has experienced a relatively balanced circulation of researchers in more recent years. These findings suggest that the current trends in scholarly migration in Russia could be better framed as brain circulation, rather than as brain drain. Overall, researchers emigrating from Russia outnumbered and outperformed researchers immigrating to Russia. Our analysis on the subject categories of publication venues shows that in the past 25 years, Russia has, overall, suffered a net loss in most disciplines, and most notably in the five disciplines of neuroscience, decision sciences, mathematics, biochemistry, and pharmacology. We demonstrate the robustness of our main findings under random exclusion of data and changes in numeric parameters. Our substantive results shed light on new aspects of international mobility in academia, and on the impact of this mobility on a national science system, which have direct implications for policy development. Methodologically, our novel approach to handling big data can be adopted as a framework of analysis for studying scholarly migration in other countries.

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Migration aspirations from a youth perspective: focus groups with returnees and youth in Mali

The Journal of Modern African Studies ◽

10.1017/s0022278x20000567 ◽

2020 ◽

Vol 58 (4) ◽

pp. 551-577

Author(s):

Jaimie Bleck ◽

Alison Lodermeier

Keyword(s):

Focus Groups ◽

Political Crisis ◽

Male Youth ◽

Migration Rates ◽

African Migration ◽

Youth Perspective

AbstractMali has one of the highest migration rates in Africa, but we still know very little about the processes and drivers of migration – particularly in the context of the current political crisis. This article draws on 27 focus groups with 220 returnees and male youth respondents conducted in the summer of 2018. Respondents cite underemployment and the inability to provide for relatives as well as a feeling of hopelessness about a future life in Mali as drivers of migration. Returnees report that the voyage was more difficult than anticipated. However, even with knowledge of the significant risks they face, most (68%) returnees express a desire to try to migrate again: this is particularly true for returned migrants who failed in an attempt to reach Europe (89%). The research illustrates very different experiences for migrants attempting to reach Europe and those with goals of intra-African migration.

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