scholarly journals Multiscale population dynamics in reproductive biology: singular perturbation reduction in deterministic and stochastic models

2020 ◽  
Vol 67 ◽  
pp. 72-99 ◽  
Author(s):  
Celine Bonnet ◽  
Keltoum Chahour ◽  
Frédérique Clément ◽  
Marie Postel ◽  
Romain Yvinec
Keyword(s):  
Population Dynamics ◽  
Singular Perturbation ◽  
Stochastic Models ◽  
Ovarian Follicle ◽  
Population Level ◽  
Bimodal Distribution ◽  
Special Focus ◽  
Reduction Techniques ◽  
Theoretical Results ◽  
Limit Models

In this study, we describe different modeling approaches for ovarian follicle population dynamics, based on either ordinary (ODE), partial (PDE) or stochastic (SDE) differential equations, and accounting for interactions between follicles. We put a special focus on representing the population-level feedback exerted by growing ovarian follicles onto the activation of quiescent follicles. We take advantage of the timescale difference existing between the growth and activation processes to apply model reduction techniques in the framework of singular perturbations. We first study the linear versions of the models to derive theoretical results on the convergence to the limit models. In the nonlinear cases, we provide detailed numerical evidence of convergence to the limit behavior. We reproduce the main semi-quantitative features characterizing the ovarian follicle pool, namely a bimodal distribution of the whole population, and a slope break in the decay of the quiescent pool with aging.

scholarly journals The epidemiological consequences of immune priming

2012 ◽  
Vol 279 (1746) ◽  
pp. 4505-4512 ◽  
Author(s):  
Hannah J. Tidbury ◽  
Alex Best ◽  
Mike Boots
Keyword(s):  
Immune Response ◽  
Population Dynamics ◽  
Population Level ◽  
Low Doses ◽  
Population Stability ◽  
Invertebrate Immunity ◽  
Invertebrate Host ◽  
Immune Priming ◽  
Pathogen Persistence ◽  
Full Immunity

Exposure to low doses of pathogens that do not result in the host becoming infectious may ‘prime’ the immune response and increase protection to subsequent challenge. There is increasing evidence that such immune priming is a widespread and important feature of invertebrate host–pathogen interactions. Immune priming clearly has implications for individual hosts but will also have population-level implications. We present a susceptible–primed–infectious model—in contrast to the classic susceptible–infectious–recovered framework—to investigate the impacts of immune priming on pathogen persistence and population stability. We describe impacts of immune priming on the epidemiology of the disease in both constant and seasonal environments. A key result is that immune priming may act to destabilize population dynamics. In particular, when the proportion of individuals becoming primed rather than infected is high, but this priming does not confer full immunity, the population may be strongly destabilized through the generation of limit cycles. We discuss the implications of our model both in the context of invertebrate immunity and more widely.

scholarly journals Global Stability and Hopf-bifurcation Analysis of Biological Systems using Delayed Extended Rosenzweig-MacArthur Model

2018 ◽  
Vol 12 (2) ◽  
pp. 171
Author(s):  
Enobong E. Joshua ◽  
Cec Ekemini T. Akpan
Keyword(s):  
Experimental Data ◽  
Population Dynamics ◽  
Hopf Bifurcation ◽  
Asymptotic Stability ◽  
Asymptotically Stable ◽  
Stability Switches ◽  
Large Delay ◽  
Local Hopf Bifurcation ◽  
Delay Margin ◽  
Theoretical Results

This paper investigates the global asymptotic stability of a Delayed Extended Rosenzweig-MacArthur Model via Lyapunov-Krasovskii functionals. Frequency sweeping technique ensures stability switches as the delay parameter increases and passes the critical bifurcating threshold.The model exhibits a local Hopf-bifurcation from asymptotically stable oscillatory behaviors to unstable strange chaotic behaviors dependent of the delay parameter values.Hyper-chaotic fluctuations were observed for large delay values far away from the critical delay margin. Numerical simulations of experimental data obtained via non-dimensionalization have shown the applications of theoretical results in ecological population dynamics.

scholarly journals Proteolytic Remodeling of Perineuronal Nets: Effects on Synaptic Plasticity and Neuronal Population Dynamics

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
P. Lorenzo Bozzelli ◽  
Seham Alaiyed ◽  
Eunyoung Kim ◽  
Sonia Villapol ◽  
Katherine Conant
Keyword(s):  
Population Dynamics ◽  
Synaptic Plasticity ◽  
Synaptic Input ◽  
Neuronal Plasticity ◽  
Population Level ◽  
Gamma Oscillations ◽  
Brain Regions ◽  
Neuronal Population ◽  
Perineuronal Nets ◽  
Perineuronal Net

The perineuronal net (PNN) represents a lattice-like structure that is prominently expressed along the soma and proximal dendrites of parvalbumin- (PV-) positive interneurons in varied brain regions including the cortex and hippocampus. It is thus apposed to sites at which PV neurons receive synaptic input. Emerging evidence suggests that changes in PNN integrity may affect glutamatergic input to PV interneurons, a population that is critical for the expression of synchronous neuronal population discharges that occur with gamma oscillations and sharp-wave ripples. The present review is focused on the composition of PNNs, posttranslation modulation of PNN components by sulfation and proteolysis, PNN alterations in disease, and potential effects of PNN remodeling on neuronal plasticity at the single-cell and population level.

scholarly journals dDocent: a RADseq, variant-calling pipeline designed for population genomics of non-model organisms

2014 ◽  
Author(s):  
Jonathan Puritz ◽  
Christopher M. Hollenbeck ◽  
John R. Gold
Keyword(s):  
Population Genomics ◽  
De Novo ◽  
Variant Calling ◽  
Population Level ◽  
Model Organisms ◽  
Effective Population ◽  
Reduction Techniques ◽  
Indel Polymorphisms ◽  
Indel Calling ◽  
Population Sizes

Restriction-site associated DNA sequencing (RADseq) has become a powerful and useful approach for population genomics. Currently, no software exists that utilizes both paired-end reads from RADseq data to efficiently produce population-informative variant calls, especially for organisms with large effective population sizes and high levels of genetic polymorphism but for which no genomic resources exist. dDocent is an analysis pipeline with a user-friendly, command-line interface designed to process individually barcoded RADseq data (with double cut sites) into informative SNPs/Indels for population-level analyses. The pipeline, written in BASH, uses data reduction techniques and other stand-alone software packages to perform quality trimming and adapter removal, de novo assembly of RAD loci, read mapping, SNP and Indel calling, and baseline data filtering. Double-digest RAD data from population pairings of three different marine fishes were used to compare dDocent with Stacks, the first generally available, widely used pipeline for analysis of RADseq data. dDocent consistently identified more SNPs shared across greater numbers of individuals and with higher levels of coverage. This is most likely due to the fact that dDocent quality trims instead of filtering and incorporates both forward and reverse reads in assembly, mapping, and SNP calling, thus enabling use of reads with Indel polymorphisms. The pipeline and a comprehensive user guide can be found at (http://dDocent.wordpress.com).

scholarly journals The consequences of polyandry for population viability, extinction risk and conservation

2013 ◽  
Vol 368 (1613) ◽  
pp. 20120053 ◽  
Author(s):  
Luke Holman ◽  
Hanna Kokko
Keyword(s):  
Population Dynamics ◽  
Extinction Risk ◽  
Population Level ◽  
Female Fitness ◽  
Male Care ◽  
Negative Effect ◽  
Adverse Environmental Conditions ◽  
The Cost ◽  
Cost Of Sex ◽  
Population Fitness

Polyandry, by elevating sexual conflict and selecting for reduced male care relative to monandry, may exacerbate the cost of sex and thereby seriously impact population fitness. On the other hand, polyandry has a number of possible population-level benefits over monandry, such as increased sexual selection leading to faster adaptation and a reduced mutation load. Here, we review existing information on how female fitness evolves under polyandry and how this influences population dynamics. In balance, it is far from clear whether polyandry has a net positive or negative effect on female fitness, but we also stress that its effects on individuals may not have visible demographic consequences. In populations that produce many more offspring than can possibly survive and breed, offspring gained or lost as a result of polyandry may not affect population size. Such ecological ‘masking’ of changes in population fitness could hide a response that only manifests under adverse environmental conditions (e.g. anthropogenic change). Surprisingly few studies have attempted to link mating system variation to population dynamics, and in general we urge researchers to consider the ecological consequences of evolutionary processes.

scholarly journals From global to local scale: where is the best for conservation purpose?

2020 ◽  
Vol 30 (1) ◽  
pp. 183-200
Author(s):  
Elena Sulis ◽  
Gianluigi Bacchetta ◽  
Donatella Cogoni ◽  
Giuseppe Fenu
Keyword(s):  
Population Dynamics ◽  
Local Level ◽  
Demographic Data ◽  
Conservation Status ◽  
Population Level ◽  
Local Scale ◽  
Local Analysis ◽  
Vital Rates ◽  
Spanish Populations ◽  
Local Trend

AbstractDemographic analysis of plant populations represents an essential conservation tool allowing to identify the population trends both at global and at the local level. In this study, the population dynamics of Helianthemum caput-felis (Cistaceae) was investigated at the local level by monitoring six populations distributed in Sardinia, Balearic Islands and Ibero-Levantine coast (Alicante). Demographic data for each population were analysed by performing Integral Projection Models (IPMs). Our results showed that, although the local trend of the main basic demographic functions was similar, vital rates and demographic dynamics varied among populations indicating high variability. In fact, asymptotic growth rate in Spanish populations widely varied both between years and populations (some populations growth, decline or strongly decline), while Sardinian populations showed greater equilibrium or a slight increase. Also, the typical pattern of a long-lived species was not supported by the results at the local scale. These results indicated that different populations of the same species can present extremely different population dynamics and support the belief that, for conservation needs, local studies are more informative than global ones: the conservation status of H. caput-felis could notably vary at a small spatial scale and, accordingly, the conservation efforts must be planned at the population level and supported by local analysis.

scholarly journals Analyzing and Modeling Temporal Disease Progress of Barley yellow dwarf virus Serotypes in Barley Fields

2000 ◽  
Vol 90 (8) ◽  
pp. 860-866 ◽  
Author(s):  
F. Leclercq-Le Quillec ◽  
M. Plantegenest ◽  
G. Riault ◽  
C. A. Dedryver
Keyword(s):  
Population Dynamics ◽  
Barley Yellow Dwarf Virus ◽  
Rhopalosiphum Padi ◽  
Bimodal Distribution ◽  
Yellow Dwarf ◽  
Dwarf Virus ◽  
Metopolophium Dirhodum ◽  
Barley Yellow Dwarf ◽  
Virus Serotype ◽  
Yellow Dwarf Virus

Population dynamics of Padi avenae (PAV), Macrosiphum avenae (MAV), and Rhopalosiphum padi (RPV) virus serotypes of Barley yellow dwarf virus (BYDV) and of their main aphid vectors were studied in winter barley (Hordeum vulgare) fields for three successive years in western France. An epidemiological model of the spread of viruses in the field was developed based on vector populations as forcing variables and the population dynamics of each virus serotype. This model accurately simulated the kinetics of the epidemic for PAV serotypes, which are the most common ones. For RPV and to some extent for MAV, the results were less satisfactory. The occurrence and spread of PAV and MAV serotypes in the field was clearly and easily related to that of their main vector species. Conversely, the spread of RPV serotypes showed no consistent relationships with the dynamics of their vectors. Incidence of PAV in 1989 to 1990 and 1990 to 1991 showed a bimodal distribution, with maximums in fall (December) and spring (May) that were linked to fall infestations by R. padi and spring infestations by three (R. padi, Sitobion avenae, and Metopolophium dirhodum) or two (S. avenae and M. dirhodum) aphid species. In 1991 to 1992, the PAV infection curve was monomodal and mainly due to a primary spread of the virus by very large populations of alate R. padi. MAV incidence was low in fall and winter and reached a maximum in spring 1990 and 1991 related to the occurrence of S. avenae and M. dirhodum. RPV incidence was low every year, despite the abundance of its vector, R. padi. Mixed infections were more frequent than expected by chance and were assumed to be partly related to heterologous encapsidation. The occurrence of each serotype is discussed in relation to the time of crop infection and possible damage.

scholarly journals A Simplified Population-Level Landscape Model Identifying Ecological Risk Drivers of Pesticide Applications, Part One: Case Study for Large Herbivorous Mammals

2021 ◽  
Vol 18 (15) ◽  
pp. 7720
Author(s):  
David Tarazona ◽  
Guillermo Tarazona ◽  
Jose V. Tarazona
Keyword(s):  
Population Dynamics ◽  
Pesticide Exposure ◽  
Population Level ◽  
Guidance Document ◽  
Population Abundance ◽  
Landscape Model ◽  
Ecological Data ◽  
Conceptual Approach ◽  
Terrestrial Vertebrates ◽  
The Impact

Environmental risk assessment is a key process for the authorization of pesticides, and is subjected to continuous challenges and updates. Current approaches are based on standard scenarios and independent substance-crop assessments. This arrangement does not address the complexity of agricultural ecosystems with mammals feeding on different crops. This work presents a simplified model for regulatory use addressing landscape variability, co-exposure to several pesticides, and predicting the effect on population abundance. The focus is on terrestrial vertebrates and the aim is the identification of the key risk drivers impacting on mid-term population dynamics. The model is parameterized for EU assessments according to the European Food Safety Authority (EFSA) Guidance Document, but can be adapted to other regulatory schemes. The conceptual approach includes two modules: (a) the species population dynamics, and (b) the population impact of pesticide exposure. Population dynamics is modelled through daily survival and seasonal reproductions rates; which are modified in case of pesticide exposure. All variables, parameters, and functions can be modified. The model has been calibrated with ecological data for wild rabbits and brown hares and tested for two herbicides, glyphosate and bromoxynil, using validated toxicity data extracted from EFSA assessments. Results demonstrate that the information available for a regulatory assessment, according to current EU information requirements, is sufficient for predicting the impact and possible consequences at population dynamic levels. The model confirms that agroecological parameters play a key role when assessing the effect of pesticide exposure on population abundance. The integration of laboratory toxicity studies with this simplified landscape model allows for the identification of conditions leading to population vulnerability or resilience. An Annex includes a detailed assessment of the model characteristics according to the EFSA scheme on Good Modelling Practice.

scholarly journals Multiple regions of primate orofacial sensorimotor cortex encode bite force and gape

2020 ◽  
Author(s):  
Fritzie I. Arce-McShane ◽  
Barry J. Sessle ◽  
Yasheshvini Ram ◽  
Carrie A. Balcer ◽  
Callum F. Ross ◽  
...  
Keyword(s):  
Sensorimotor Cortex ◽  
Linear Models ◽  
Population Level ◽  
Brain Regions ◽  
Bite Force ◽  
Population Activity ◽  
Precise Control ◽  
Reduction Techniques ◽  
Multiple Regions ◽  
Task Parameters

AbstractThe precise control of bite force and gape is vital for effective breakdown and manipulation of food inside the oral cavity during feeding. Yet the role of the orofacial sensorimotor cortex (OSMcx) in the control of bite force and gape is still largely unknown. The aim of this study was to elucidate how individual neurons and populations of neurons in multiple regions of OSMcx differentially encode bite force and gape when subjects (Macaca mulatta) generated different levels of bite force at varying gapes. We examined neuronal activity recorded simultaneously from three microelectrode arrays implanted chronically in the primary motor (MIo), primary somatosensory (SIo), and cortical masticatory (CMA) areas of OSMcx. We used generalized linear models to evaluate encoding properties of individual neurons and utilized dimensionality reduction techniques to decompose population activity into components related to specific task parameters. Individual neurons encoded bite force more strongly than gape in all three OSMCx areas although bite force was a better predictor of spiking activity in MIo versus SIo. Population activity differentiated between levels of bite force and gape while preserving task-independent temporal modulation across the behavioral trial. While activation patterns of neuronal populations were comparable across OSMCx areas, the total variance explained by task parameters was context-dependent and differed across areas. These findings suggest that the cortical control of gape may rely on computations at the population level whereas the strong encoding of bite force at the individual neuron level allows for the precise and rapid control of bite force.Significance StatementBiting a piece off an apple requires precise sensorimotor control and coordination of bite force and gape by multiple brain regions. The cortical representations of bite force and gape by individual neurons and large populations of neurons across connected motor and somatosensory areas in orofacial cortex is unknown. Here we showed that bite force was more strongly encoded than gape by individual neurons in primary motor, somatosensory, and cortical masticatory areas. Moreover, bite force was more effectively represented in motor versus somatosensory cortices. At the population level, bite force and gape were distinguishable particularly when gape was randomized from trial-to-trial. The results are important for understanding neurophysiological processes underlying masticatory dysfunctions that may occur in aging, stroke, and Alzheimer’s disease.

scholarly journals Outbreaks of Tomostethus nigritus (Fabricius, 1804) (Hymenoptera, Tenthredinidae) on Fraxinus angustifolia ‘Raywood’ in Belgium

2019 ◽  
Vol 72 ◽  
pp. 67-81
Author(s):  
Fons Verheyde ◽  
Geert Sioen
Keyword(s):  
Population Dynamics ◽  
Crucial Role ◽  
Western Europe ◽  
Population Level ◽  
Climatic Conditions ◽  
Future Research ◽  
Pest Species ◽  
Satisfactory Explanation ◽  
Fraxinus Angustifolia ◽  
The City

In Western Europe the ash sawfly Tomostethus nigritus is known to occur at low densities on Fraxinus excelsior and is uncommonly reported as a pest species. However, we show here that outbreaks can occur on non-endemic trees such as F. angustifolia, and that the species is able to spread quickly using city infrastructure. At the visited localities near the city of Ghent, foliage of Fraxinus angustifolia ‘Raywood’ emerged approximately one month earlier than on F. excelsior. At the same time, changed climatic conditions in the last decade, i.e. higher temperatures in March, caused adults to emerge earlier. Synchronicity of the potential hosts and T. nigritus may therefore have altered, playing a crucial role in population dynamics. Future research should aim to confirm if the species dramatically declines in numbers after reaching its peak population level, an effect which was observed in previous studies, but for which there is still no satisfactory explanation.

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