The population dynamics of aphids on fire weed: a comparison of local populations and metapopulations

1978 ◽  
Vol 56 (12) ◽  
pp. 2554-2564 ◽  
Author(s):  
John F. Addicott
Keyword(s):  
Population Dynamics ◽  
Spatial Heterogeneity ◽  
Rocky Mountains ◽  
Median Number ◽  
Marked Variation ◽  
High Frequencies ◽  
Local Populations ◽  
Epilobium Angustifolium ◽  
Population Processes ◽  
Different Levels

Local populations of four species of aphids (Macrosiphum Valerianae, Aphis varions, A. helianthi, and A. salicariae) occur on shoots of fireweed (Epilobium angustifolium) in the Rocky Mountains of Colorado, U.S.A. Through exhaustive and repeated nondestructive sampling of the local populations on over 3800 shoots of fireweed, information was obtained on the dynamics of both the local populations and the metapopulation of each species. The dynamics of the metapopulation were analyzed in terms of the frequency of shoots occupied by aphids and the median number of aphids per occupied shoot. There were significant differences between species in both parameters, but high densities were not necessarily accompanied by high frequencies. Local populations were initiated throughout the summer, and there was marked variation in the duration and size of these populations. Most populations lasted only a few weeks, but others lasted up to 14 weeks. This turnover of local populations within the metapopulation implies that local populations must be studied in order to understand the dynamics of the metapopulation. There is a discussion of the relationships between population processes occurring at different levels of spatial heterogeneity.

scholarly journals Explaining Spatial Heterogeneity in Population Dynamics and Genetics from Spatial Variation in Resources for a Large Herbivore

PLoS ONE ◽  
2012 ◽  
Vol 7 (10) ◽  
pp. e47858 ◽  
Author(s):  
Adrienne L. Contasti ◽  
Emily J. Tissier ◽  
Jill F. Johnstone ◽  
Philip D. McLoughlin
Keyword(s):  
Population Dynamics ◽  
Spatial Heterogeneity ◽  
Spatial Variation ◽  
Large Herbivore

scholarly journals Simulating the impact of vaccination rates on the initial stages of a COVID-19 outbreak in New Zealand (Aotearoa) with a stochastic model

2021 ◽  
Author(s):  
Leighton M Watson
Keyword(s):  
New Zealand ◽  
Stochastic Model ◽  
Process Model ◽  
Branching Process ◽  
Total Population ◽  
Median Number ◽  
Vaccination Rate ◽  
Vaccination Rates ◽  
The Impact ◽  
Different Levels

Aim: The August 2021 COVID-19 outbreak in Auckland has caused the New Zealand government to transition from an elimination strategy to suppression, which relies heavily on high vaccination rates in the population. As restrictions are eased and as COVID-19 leaks through the Auckland boundary, there is a need to understand how different levels of vaccination will impact the initial stages of COVID-19 outbreaks that are seeded around the country. Method: A stochastic branching process model is used to simulate the initial spread of a COVID-19 outbreak for different vaccination rates. Results: High vaccination rates are effective at minimizing the number of infections and hospitalizations. Increasing vaccination rates from 20% (approximate value at the start of the August 2021 outbreak) to 80% (approximate proposed target) of the total population can reduce the median number of infections that occur within the first four weeks of an outbreak from 1011 to 14 (25th and 75th quantiles of 545-1602 and 2-32 for V=20% and V=80%, respectively). As the vaccination rate increases, the number of breakthrough infections (infections in fully vaccinated individuals) and hospitalizations of vaccinated individuals increases. Unvaccinated individuals, however, are 3.3x more likely to be infected with COVID-19 and 25x more likely to be hospitalized. Conclusion: This work demonstrates the importance of vaccination in protecting individuals from COVID-19, preventing high caseloads, and minimizing the number of hospitalizations and hence limiting the pressure on the healthcare system.

scholarly journals The distribution of transposable elements within and between chromosomes in a population of Drosophila melanogaster. I. Element frequencies and distribution

1992 ◽  
Vol 60 (2) ◽  
pp. 103-114 ◽  
Author(s):  
Brian Charlesworth ◽  
Angela Lapid ◽  
Darlene Canada
Keyword(s):  
Population Dynamics ◽  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Transposable Elements ◽  
Copy Number ◽  
Polytene Chromosomes ◽  
Chromosome Band ◽  
High Frequencies ◽  
Copy Numbers

SummaryData were collected on the distribution of nine families of transposable elements among second and third chromosomes isolated from a natural population of Drosophila melanogaster, by means of in situ hybridization of element probes to polytene chromosomes. It was found that the copy numbers per chromosome in the distal sections of the chromosome arms followed a Poisson distribution. Elements appeared to be distributed randomly along the distal sections of the chromosome arms. There was no evidence for linkage disequilibrium in the distal sections of the chromosomes, but some significant disequilibrium was detected in proximal regions. There were many significant correlations between different element families with respect to the identity of the sites that were occupied in the sample. There were also significant correlations between families with respect to sites at which elements achieved relatively high frequencies. Element frequencies per chromosome band were generally low in the distal sections, but were higher proximally. These results are discussed in the light of models of the population dynamics of transposable elements. It is concluded that they provide strong evidence for the operation of a force or forces opposing transpositional increase in copy number. The data suggest that the rate of transposition perelement per generation is of the order of 10−4, for the elements included in this study.

Macroeconomic and Operational Challenges in Countries in Fragile Situations

Policy Papers ◽  
2011 ◽  
Vol 11 (43) ◽  
Author(s):  
Keyword(s):  
Political Economy ◽  
Social Cohesion ◽  
International Community ◽  
Capacity Constraints ◽  
The Political ◽  
Fragile States ◽  
Uncertain Environments ◽  
Common Features ◽  
Local Populations ◽  
Different Levels

There is broad recognition that countries in fragile situations face unique challenges. While fragility may afflict countries at different levels of income and capacity, common features of fragile states are institutions that are seen to be weak and lack legitimacy, as well as a fractious political setting, which in turn elevates the risk of violence. Fragilities impose large costs and hardships on local populations that can spill over to neighboring countries—directly through conflict, crime, and disease, but also through economic linkages. Considering these unique challenges, the international community is developing forms of engagement that stress peacebuilding, social cohesion, and statebuilding. They incorporate recognition of the need for sustained engagement, a willingness to take calculated risks in uncertain environments, fuller attention to the political economy of reforms and capacity constraints, and coordination of donor efforts.

scholarly journals Global Production Increased by Spatial Heterogeneity in a Population Dynamics Model

2005 ◽  
Vol 53 (4) ◽  
pp. 359-370 ◽  
Author(s):  
J.-C. Poggiale ◽  
P. Auger ◽  
D. Nérini ◽  
C. Manté ◽  
F. Gilbert
Keyword(s):  
Population Dynamics ◽  
Spatial Heterogeneity ◽  
Dynamics Model ◽  
Population Dynamics Model

scholarly journals Habitat choice stabilizes metapopulation dynamics through increased ecological specialisation

2018 ◽  
Author(s):  
Frederik Mortier ◽  
Staffan Jacob ◽  
Martijn L. Vandegehuchte ◽  
Dries Bonte
Keyword(s):  
Population Dynamics ◽  
Habitat Choice ◽  
Current Theory ◽  
Metapopulation Dynamics ◽  
Evolution Of Dispersal ◽  
Tight Coupling ◽  
Dispersal Capacity ◽  
Local Populations ◽  
Informed Decisions ◽  
The Face

AbstractDispersal is a key trait responsible for the spread of individuals and genes among local populations, thereby generating eco-evolutionary interactions. Especially in heterogeneous metapopulations, a tight coupling between dispersal, population dynamics and the evolution of local adaptation is expected. In this respect, current theory predicts dispersal to counteract ecological specialisation by redistributing locally selected phenotypes (i.e. migration load). However, in nature we observe that some specialists exhibit a strong dispersal capacity.Habitat choice following informed dispersal decisions, provides a possible mechanism for individuals to match the environment to their phenotype, thereby enabling the persistence of evolved ecological specialisation. How such informed decisions affect the evolution of dispersal and ecological specialisation and how these, in turn, influence metapopulation dynamics is yet to be determined.By means of individual-based modelling, we show that informed decisions on both departure and settlement decouples the evolution of dispersal and generalism, favouring highly dispersive specialists. Choice at settlement decouples dispersal from ecological specialisation most effectively. Additionally, habitat choice stabilizes local and metapopulation demography because of the maintenance of ecological specialisation at all levels of dispersal propensity.We advocate considering habitat choice in spatially structured ecological models to improve demographic predictions in the face of environmental change.

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