scholarly journals Feedback Between Coevolution and Epidemiology Can Help or Hinder the Maintenance of Genetic Variation in Host-Parasite Models

2020 ◽  
Author(s):  
Ailene MacPherson ◽  
Matthew J. Keeling ◽  
Sarah P. Otto
Keyword(s):  
Genetic Variation ◽  
Population Fluctuations ◽  
Red Queen ◽  
Neutral Drift ◽  
Disease Epidemiology ◽  
Two Factors ◽  
Population Sizes ◽  
Host Genetic ◽  
Host Parasite ◽  
The Impact

AbstractUnderstanding if and when coevolution helps maintains genetic variation in hosts of a directly-transmissible pathogen is fundamental to quantifying the prevalence and impact of coevolution on disease epidemiology. Here, we extend our previous work on the maintenance of genetic variation in a classic matching-alleles coevolutionary model by exploring the effects of ecological and epidemiological feedbacks, where both allele frequencies and population sizes are allowed to vary over time. In general, we find that coevolution rarely maintains more host genetic variation than expected under neutral genetic drift alone. When and if coevolution maintains or depletes genetic variation relative to neutral drift is determined, predominantly, by two factors: the deterministic stability of the Red Queen allele frequency cycles and the frequency at which pathogen fixation occurs, as this results in directional selection and the depletion of genetic variation in the host. Compared to purely coevolutionary models with constant host and pathogen population sizes, ecological and epidemiological feedbacks stabilize Red Queen cycles deterministically, but population fluctuations in the pathogen increase the rate of pathogen fixation, especially in epidemiological models. Taken together our results illustrate the importance of considering the ecological and epidemiological context in which coevolution occurs when examining the impact of Red Queen cycles on genetic variation.

scholarly journals The impact of host genetic variation on infection with HIV-1

2015 ◽  
Vol 16 (6) ◽  
pp. 577-583 ◽  
Author(s):  
Paul J McLaren ◽  
Mary Carrington
Keyword(s):  
Genetic Variation ◽  
Host Genetic ◽  
The Impact ◽  
Hiv 1

scholarly journals Threshold harvesting as a conservation or exploitation strategy in population management

2020 ◽  
Vol 13 (4) ◽  
pp. 519-536
Author(s):  
Frank M. Hilker ◽  
Eduardo Liz
Keyword(s):  
Management Strategies ◽  
Population Cycles ◽  
Life Cycles ◽  
Environmental Stochasticity ◽  
Population Fluctuations ◽  
Allee Effects ◽  
Resource Exploitation ◽  
Population Sizes ◽  
Observation Uncertainty ◽  
The Impact

AbstractThreshold harvesting removes the surplus of a population above a set threshold and takes no harvest below the threshold. This harvesting strategy is known to prevent overexploitation while obtaining higher yields than other harvesting strategies. However, the harvest taken can vary over time, including seasons of no harvest at all. While this is undesirable in fisheries or other exploitation activities, it can be an attractive feature of management strategies where removal interventions are costly and desirable only occasionally. In the presence of population fluctuations, the issue of variable harvests and population sizes becomes even more notorious. Here, we investigate the impact of threshold harvesting on the dynamics of both population size and harvests, especially in the presence of population cycles. We take into account semelparous and iteroparous life cycles, Allee effects, observation uncertainty, and demographic as well as environmental stochasticity, using generic mathematical models in discrete time. Our results show that threshold harvesting enhances multiple forms of population stability, namely persistence, constancy, resilience, and dynamic stability. We discuss plausible choices of threshold values, depending on whether the aim is resource exploitation, pest control, or the stabilization of fluctuations.

scholarly journals Comparison of genetic variation between rare and common congeners of Dipodomys with estimates of contemporary and historical effective population size

2021 ◽  
Author(s):  
Michaela Halsey ◽  
John Stuhler ◽  
Natalia J Bayona-Vasquez ◽  
Roy N Platt ◽  
Jim R Goetze ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Population Size ◽  
Effective Population Size ◽  
Population Fluctuations ◽  
Nucleotide Polymorphisms ◽  
Effective Population ◽  
Single Nucleotide ◽  
Demographic Dynamics ◽  
Population Sizes

Organisms with low effective population sizes are at greater risk of extinction because of reduced genetic diversity.   Dipodomys elator  is a kangaroo rat that is classified as threatened in Texas and field surveys from the past 50 years indicate that the distribution of this species has decreased. This suggests geographic range reductions that could have caused population fluctuations, potentially impacting effective population size. Conversely, the more common and widespread  D. ordii  is thought to exhibit relative geographic and demographic stability. Genetic variation between  D. elator  and  D. ordii  samples was assessed using 3RAD, a modified restriction site associated sequencing approach. It was hypothesized that  D. elator  would show lower levels of nucleotide diversity, observed heterozygosity, and effective population size when compared to  D. ordii . Also of interest was identifying population structure within contemporary samples of  D. elator  and detecting genetic variation between temporal samples that could indicate demographic dynamics. Up to 61,000 single nucleotide polymorphisms were analyzed. It was determined that genetic variability and effective population size in contemporary  D. elator  populations were lower than that of  D. ordii, that there is only slight, if any, structure within contemporary  D. elator  populations, and there is little genetic differentiation between spatial or temporal historical samples suggesting little change in nuclear genetic diversity over 30 years. Results suggest that genetic diversity of  D. elator  has remained stable despite claims of reduced population size and/or abundance, which may indicate a metapopulation-like system, whose fluctuations might counteract any immediate decrease in fitness.

Characterizing the impact of recovering sea otters on commercially important crabs in California estuaries

2020 ◽  
Vol 655 ◽  
pp. 123-137
Author(s):  
TM Grimes ◽  
MT Tinker ◽  
BB Hughes ◽  
KE Boyer ◽  
L Needles ◽  
...  
Keyword(s):  
Abiotic Factors ◽  
Sea Otter ◽  
Dungeness Crab ◽  
Sea Otters ◽  
Elkhorn Slough ◽  
Enhydra Lutris Nereis ◽  
Crab Abundance ◽  
Population Sizes ◽  
Commercially Important ◽  
The Impact

Protective legislation and management have led to an increase in California’s sea otter Enhydra lutris nereis population. While sea otter recovery has been linked to ecosystem benefits, sea otter predation may negatively affect commercially valuable species. Understanding the potential influence of sea otters is of particular importance as their range expands into estuaries that function as nurseries for commercially valuable species like Dungeness crab Metacarcinus magister. We consider how sea otter predation has affected the abundance and size of juvenile Dungeness crab in Elkhorn Slough, California, USA, and analyzed cancrid crab abundance and size across 4 California estuaries with and without sea otters to understand how biotic and abiotic factors contribute to observed variation in crab size and abundance. We compared trends in southern sea otters relative to Dungeness crab landings in California to assess whether increasing sea otter abundance have negatively impacted landings. In Elkhorn Slough, juvenile Dungeness crab abundance and size have declined since 2012, coinciding with sea otter population growth. However, the impact of sea otters on juvenile Dungeness crab size was habitat-specific and only significant in unvegetated habitat. Across estuaries, we found that cancrid crab abundance and size were negatively associated with sea otter presence. While abiotic factors varied among estuaries, these factors explained little of the observed variation in crab abundance or size. Although we found evidence that sea otters can have localized effects on cancrid crab populations within estuaries, we found no evidence that southern sea otters, at recent population sizes, have negatively impacted Dungeness crab landings in California from 2000-2014.

Self-Esteem and Loneliness as Predicting Factors of Arab Children Achievement İn Kuala Lumpur

2015 ◽  
Vol 5 (1) ◽  
pp. 199 ◽  
Author(s):  
Asma'a Abdel Fattah Alhoot ◽  
Ssekamanya Sıraje Abdallah
Keyword(s):  
Academic Achievement ◽  
Relevant Literature ◽  
Self Esteem ◽  
Kuala Lumpur ◽  
Arab Children ◽  
Predicting Factors ◽  
Two Factors ◽  
Arab Schools ◽  
And Gender ◽  
The Impact

Taking into consideration the fact that self-esteem and loneliness have an even more important role to play in students' learning, this study seeks to examine the correlation of these two factors with children academic performance. The study involved 499 (grade 4 to grade 9) Arab children studying at Arab schools in Kuala Lumpur-Malaysia. Data were collected via two questionnaires (one for loneliness and the other for self-esteem). The correlational data analysis yielded a negative correlation between loneliness and academic achievement while there is a positive correlation between self-esteem and achievement. Results also suggested that there is no correlation between students' gender, age, and academic achievement. Furthermore, the results revealed that self-esteem is a good predictor of achievement while loneliness and gender are not good predictors. The findings of the present study are discussed in relation to the relevant literature, taking into consideration the impact of children mental health on their academic achievement. Finally, recommendations for further research are presented.

scholarly journals The Impact of Health Policies and Sociodemographic Factors on Doubling Time of the COVID-19 Pandemic in Mexico

2021 ◽  
Vol 18 (5) ◽  
pp. 2354
Author(s):  
Lina Díaz-Castro ◽  
Héctor Cabello-Rangel ◽  
Kurt Hoffman
Keyword(s):  
Population Density ◽  
Doubling Time ◽  
Sociodemographic Factors ◽  
Health Policies ◽  
Government Response ◽  
University Of Oxford ◽  
Negative Effect ◽  
Population Sizes ◽  
The University ◽  
The Impact

Background. The doubling time is the best indicator of the course of the current COVID-19 pandemic. The aim of the present investigation was to determine the impact of policies and several sociodemographic factors on the COVID-19 doubling time in Mexico. Methods. A retrospective longitudinal study was carried out across March–August, 2020. Policies issued by each of the 32 Mexican states during each week of this period were classified according to the University of Oxford Coronavirus Government Response Tracker (OxCGRT), and the doubling time of COVID-19 cases was calculated. Additionally, variables such as population size and density, poverty and mobility were included. A panel data model was applied to measure the effect of these variables on doubling time. Results. States with larger population sizes issued a larger number of policies. Delay in the issuance of policies was associated with accelerated propagation. The policy index (coefficient 0.60, p < 0.01) and the income per capita (coefficient 3.36, p < 0.01) had a positive effect on doubling time; by contrast, the population density (coefficient −0.012, p < 0.05), the mobility in parks (coefficient −1.10, p < 0.01) and the residential mobility (coefficient −4.14, p < 0.01) had a negative effect. Conclusions. Health policies had an effect on slowing the pandemic’s propagation, but population density and mobility played a fundamental role. Therefore, it is necessary to implement policies that consider these variables.

scholarly journals Phony peach disease: past and present impact on the peach industry in the southeastern U.S.A

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Kendall A. Johnson ◽  
Clive H. Bock ◽  
Phillip M. Brannen
Keyword(s):  
New Technologies ◽  
Current Knowledge ◽  
Future Research ◽  
Management Options ◽  
Disease Epidemiology ◽  
Pathogen Diversity ◽  
Foundational Research ◽  
Global Threat ◽  
And Control ◽  
The Impact

Abstract Background Phony peach disease (PPD) is caused by the plant pathogenic bacterium Xylella fastidiosa subsp. multiplex (Xfm). Historically, the disease has caused severe yield loss in Georgia and elsewhere in the southeastern United States, with millions of PPD trees being removed from peach orchards over the last century. The disease remains a production constraint, and management options are few. Limited research has been conducted on PPD since the 1980s, but the advent of new technologies offers the opportunity for new, foundational research to form a basis for informed management of PPD in the U.S. Furthermore, considering the global threat of Xylella to many plant species, preventing import of Xfm to other regions, particularly where peach is grown, should be considered an important phytosanitary endeavor. Main topics We review PPD, its history and impact on peach production, and the eradication efforts that were conducted for 42 years. Additionally, we review the current knowledge of the pathogen, Xfm, and how that knowledge relates to our understanding of the peach—Xylella pathosystem, including the epidemiology of the disease and consideration of the vectors. Methods used to detect the pathogen in peach are discussed, and ramifications of detection in relation to management and control of PPD are considered. Control options for PPD are limited. Our current knowledge of the pathogen diversity and disease epidemiology are described, and based on this, some potential areas for future research are also considered. Conclusion There is a lack of recent foundational research on PPD and the associated strain of Xfm. More research is needed to reduce the impact of this pathogen on peach production in the southeastern U.S., and, should it spread internationally, wherever peaches are grown.

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