scholarly journals Density Dependence of Egg Recruitment and Moth Dispersal in Spruce Budworms

Forests ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 706 ◽  
Author(s):  
Jacques Régnière ◽  
Vincent G. Nealis
Keyword(s):  
Population Dynamics ◽  
Boreal Forests ◽  
Random Perturbation ◽  
Spruce Budworm ◽  
Formal Context ◽  
Low Density ◽  
Density Dependent ◽  
Migration Rates ◽  
Net Migration ◽  
And Migration

Egg recruitment quantifies the relative importance of realized fecundity and migration rates in the population dynamics of highly mobile insects. We develop here a formal context upon which to base the measurement and interpretation of egg recruitment in population dynamics of eastern and western spruce budworms, two geographically separated species that share a very similar ecology. Under most circumstances, per capita egg recruitment rates in these budworms are higher in low-density populations and lower in high-density populations, relative to the regional mean: Low-density populations are nearly always migration sinks for gravid moths, and dense populations nearly always sources. The slope of this relationship, measured on a log scale, is negatively correlated with migration rate, and ranges between 0 and −1. The steeper the slope, the more marked net migration. Using our western spruce budworm observations, we found strong evidence of density-dependent emigration in budworms, so migration is not simply a random perturbation in the lagged, density-dependent stochastic process leading to budworm outbreaks. It is itself statistically and biologically density-dependent. Therefore, moth migration is a synchronizing factor and a spread mechanism that is essential to understanding the development and expansion of spruce budworm outbreaks at regional scales in the boreal forests of North America.

International Migration in Russia: Dynamics, Policies, Forecast

2011 ◽  
pp. 35-53
Author(s):  
S. Ivanov
Keyword(s):  
Population Dynamics ◽  
Population Size ◽  
International Migration ◽  
Low Fertility ◽  
Population Projections ◽  
Future Trends ◽  
Net Migration ◽  
Fertility Trend ◽  
And Migration

Large flows of migrants into low fertility countries increase the weight of international migration in the population dynamics. The current net migration inflow to Russia is about 350 thousand people per year. Migration hypotheses of the population projections include the assumption of constancy of this level until 2050; net migration of 50 thousand people per year; zero net migration and net migration at the level of 900 thousand people per year. Migration hypotheses are combined with the hypotheses of future trends in fertility, including the low, the middle and the high variants. With low fertility and zero net migration the population by 2050 will be reduced by almost half. Stable migration combined with low fertility will not prevent depopulation of the order of almost 1/3 by 2050. If fertility trend follows the high path and migration remains constant the population size will be restored in 10 years and then will increase by 10 per cent. Тo restore the population size by 2020 with slowly increasing fertility, approximately 1, 5 million people more should immigrate into Russia every year than emigrate from it.

scholarly journals Does migration depress regional human capital accumulation in the EU’s new member states? Theoretical and empirical evidence

2021 ◽  
Vol 41 (1) ◽  
pp. 95-122
Author(s):  
Sascha Sardadvar ◽  
Elena Vakulenko
Keyword(s):  
Human Capital ◽  
Growth Rates ◽  
Capital Accumulation ◽  
Member States ◽  
Migration Rates ◽  
New Member States ◽  
Net Migration ◽  
Capital Growth ◽  
And Migration ◽  
The Eu

AbstractDuring the first decade of the present century the countries which accessed the EU were characterised by high GDP growth rates while most of their regions displayed negative net-migration rates. At the same time, the new member states’ human capital endowments were high relative to their GDP levels, creating incentives to emigrate. The present paper takes a detailed look at the interplay of regional human capital endowments and migration. First, by theoretically examining migration’s determinants and second, by testing the corresponding findings via panel econometric regressions for the EU’s new member states’ regions. The results display positive impacts of net-migration on regional human capital growth rates, improving the economic potential of thriving regions but possibly increasing disparities within countries.

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

Genetics ◽  
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.

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

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.

Derivation of Pheromone-Based Larval Thresholds in Spruce Budworm Accounting for Distance to Defoliated Forest Stands

2021 ◽  
Author(s):  
Marc Rhainds ◽  
Ian DeMerchant ◽  
Pierre Therrien
Keyword(s):  
Boreal Forests ◽  
Large Scale ◽  
Choristoneura Fumiferana ◽  
Intervention Strategy ◽  
Spruce Budworm ◽  
Interactive Effects ◽  
The Novel ◽  
Forest Stands ◽  
General Guideline ◽  
Number Of Males

Abstract Spruce budworm, Choristoneura fumiferana Clem. (Lepidoptera: Tortricidae), is the most severe defoliator of Pinaceae in Nearctic boreal forests. Three tools widely used to guide large-scale management decisions (year-to-year defoliation maps; density of overwintering second instars [L2]; number of males at pheromone traps) were integrated to derive pheromone-based thresholds corresponding to specific intergenerational transitions in larval densities (L2i → L2i+1), taking into account the novel finding that threshold estimates decline with distance to defoliated forest stands (DIST). Estimates of thresholds were highly variable between years, both numerically and in terms of interactive effects of L2i and DIST, which limit their heuristic value. In the context of early intervention strategy (L2i+1 > 6.5 individuals per branch), however, thresholds fluctuated within relatively narrow intervals across wide ranges of L2i and DIST, and values of 40–200 males per trap may thus be used as general guideline.

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