scholarly journals An alternative approach to asymptotic results on genetic composition when the population size is varying

2010 ◽  
pp. 370-375
Author(s):  
C. C. Heyde
Keyword(s):  
Population Size ◽  
Genetic Composition ◽  
Asymptotic Results ◽  
Alternative Approach

scholarly journals Costs and benefits of using rhythmic rate codes

2021 ◽  
Author(s):  
Erik J. Peterson ◽  
Bradley Voytek
Keyword(s):  
Nervous System ◽  
Population Size ◽  
Synaptic Connection ◽  
Poisson Model ◽  
Neural Oscillations ◽  
Costs And Benefits ◽  
Rate Code ◽  
Firing Rates ◽  
Alternative Approach ◽  
Connection Type

AbstractNeural oscillations are one of the most well-known macroscopic phenomena observed in the nervous system, and the benefits of oscillatory coding have been the topic of frequent analysis. Many of these studies focused on communication between populations which were already oscillating, and sought to understand how synchrony and communication interact. In this paper, take an alternative approach. We focus on measuring the costs, and benefits, of moving to an from an aperiodic code to a rhythmic one. We utilize a Linear-Nonlinear Poisson model, and assume a rate code. We report that no one factor seems to predict the costs, or benefits, of translating into a rhythmic code. Instead the synaptic connection type, strength, population size, and stimulus and oscillation firing rates interact in nonlinear ways. We suggest a number of experiments that might be used to confirm these predictions.Author summaryIt’s good to oscillate, sometimes.

scholarly journals Mating System in a Native Norway Spruce (Picea abies [L.] KARST.) Stand-Relatedness and Effective Pollen Population Size Show an Association with the Germination Percentage of Single Tree Progenies

Diversity ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 266
Author(s):  
Oliver Caré ◽  
Oliver Gailing ◽  
Markus Müller ◽  
Konstantin V. Krutovsky ◽  
Ludger Leinemann
Keyword(s):  
Gene Flow ◽  
Population Size ◽  
Norway Spruce ◽  
High Elevation ◽  
Germination Percentage ◽  
Early Embryo ◽  
Genetic Composition ◽  
Embryo Abortion ◽  
Family Structures ◽  
Single Tree

Norway spruce differs little in neutral genetic markers among populations and provenances often reported, but in terms of putative adaptive traits and their candidate genes, some clear differences have been observed. This has previously been shown for crown morphotypes. Stands with mostly narrow crown shapes are adapted to high elevation conditions, but these stands are scattered, and the forest area is often occupied by planted stands with predominantly broad crowned morphotypes. This raises questions on whether this differentiation can remain despite gene flow, and on the level of gene flow between natural and planted stands growing in close neighbourhood. The locally adapted stands are a valuable seed source, the progeny of which is expected to have high genetic quality and germination ability. The presented case study is useful for spruce plantation by demonstrating evaluation of these expectations. Immigrant pollen and seeds from planted trees could be maladaptive and may alter the genetic composition of the progeny. This motivated us to study single tree progenies in a locally adapted stand with narrow crowned trees in a partial mast year at nuclear genomic simple sequence repeat (SSR) markers. Spruce is a typical open-pollinated conifer tree species with very low selfing rates, which were also observed in our study (s = 0.3–2.1%) and could be explained by efficient cross-pollination and postzygotic early embryo abortion, common in conifers. The estimated high amount of immigrant pollen found in the pooled seed lot (70.2–91.5%) is likely to influence the genetic composition of the seedlings. Notably, for individual mother trees located in the centre of the stand, up to 50% of the pollen was characterised as local. Seeds from these trees are therefore considered to retain most of the adaptive variance of the stand. Germination percentage varied greatly between half-sib families (3.6–61.9%) and was negatively correlated with relatedness and positively with effective pollen population size of the respective families. As pollen mostly originated from outside the stand and no family structures in the stand itself were found, germination differences can likely be explained by diversity differences in the individual pollen cloud.

scholarly journals Effects of demographic stochasticity and life-history strategies on times and probabilities to fixation: an individual-based model

2017 ◽  
Author(s):  
Diala Abu Awad ◽  
Camille Coron
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Life History Strategies ◽  
Genetic Composition ◽  
Effective Population ◽  
Demographic Stochasticity ◽  
Large Fluctuations ◽  
Demographic Fluctuations ◽  
Reproductive Rates ◽  
The Times

AbstractPrevious works has suggested that the harmonic mean population size can summarize the consequences of demographic fluctuations on the genetic frequencies of populations. We test this hypothesis by studying a model in which the demography and genetic composition of the population are both determined by the behavior of the individuals within the population. We propose an effective population size that allows us to compare our model with the classical Wright-Fisher diffusion both for neutral alleles and those under selection. We find that using our approximation for the effective population size, the Wright-Fisher diffusion provides good results for the times to absorption and probabilities of fixation of a given neutral allele and in cases where selection is not too strong. However, the times and laws to fixation are not always well predicted due to large fluctuations in population size caused by small growth rates or strong competition between individuals, that cannot be captured by the constant population size approximation. The discrepancy between our model and the Wright-Fisher diffusion is accentuated in the presence of demo-genetic feed-back. Our results imply that the Wright-Fisher diffusion is not appropriate when studying probabilities and times to fixation in long-lived species with low reproductive rates.

The age of a Galton-Watson population with a geometric offspring distribution

2002 ◽  
Vol 39 (4) ◽  
pp. 816-828 ◽  
Author(s):  
F. C. Klebaner ◽  
S. Sagitov
Keyword(s):  
Population Size ◽  
Asymptotic Distribution ◽  
Initial Population ◽  
Asymptotic Results ◽  
The Past ◽  
Offspring Distribution ◽  
Initial Population Size ◽  
Watson Process ◽  
Looking Back

Motivated by the question of the age in a branching population we try to recreate the past by looking back from the currently observed population size. We define a new backward Galton-Watson process and study the case of the geometric offspring distribution with parameter p in detail. The backward process is then the Galton-Watson process with immigration, again with a geometric offspring distribution but with parameter 1-p, and it is also the dual to the original Galton-Watson process. We give the asymptotic distribution of the age when the initial population size is large in supercritical and critical cases. To this end, we give new asymptotic results on the Galton-Watson immigration processes stopped at zero.

Asymptotic results for the extinction time of Markov branching processes allowing emigration, I. Random walk decrements

1989 ◽  
Vol 21 (02) ◽  
pp. 243-269 ◽  
Author(s):  
Anthony G. Pakes
Keyword(s):  
Population Size ◽  
Large Scale ◽  
Branching Process ◽  
Branching Processes ◽  
Initial Population ◽  
Extinction Time ◽  
Asymptotic Results ◽  
Time To Extinction ◽  
Initial Population Size ◽  
The Mathematical Model

The mathematical model is a Markov branching process which is subjected to catastrophes or large-scale emigration. Catastrophes reduce the population size by independent and identically distributed decrements, and two mechanisms for generating catastrophe epochs are given separate consideration. These are that catastrophes occur at a rate proportional to population size, and as an independent Poisson process. The paper studies some properties of the time to extinction of the modified process in those cases where extinction occurs almost surely. Particular attention is given to limit theorems and the behaviour of the expected extinction time as the initial population size grows. These properties are contrasted with known properties for the case when there is no catastrophe component.

Asymptotic results for the extinction time of Markov branching processes allowing emigration, I. Random walk decrements

1989 ◽  
Vol 21 (2) ◽  
pp. 243-269 ◽  
Author(s):  
Anthony G. Pakes
Keyword(s):  
Population Size ◽  
Large Scale ◽  
Branching Process ◽  
Branching Processes ◽  
Initial Population ◽  
Extinction Time ◽  
Asymptotic Results ◽  
Time To Extinction ◽  
Initial Population Size ◽  
The Mathematical Model

The mathematical model is a Markov branching process which is subjected to catastrophes or large-scale emigration. Catastrophes reduce the population size by independent and identically distributed decrements, and two mechanisms for generating catastrophe epochs are given separate consideration. These are that catastrophes occur at a rate proportional to population size, and as an independent Poisson process.The paper studies some properties of the time to extinction of the modified process in those cases where extinction occurs almost surely. Particular attention is given to limit theorems and the behaviour of the expected extinction time as the initial population size grows. These properties are contrasted with known properties for the case when there is no catastrophe component.

The age of a Galton-Watson population with a geometric offspring distribution

2002 ◽  
Vol 39 (04) ◽  
pp. 816-828 ◽  
Author(s):  
F. C. Klebaner ◽  
S. Sagitov
Keyword(s):  
Population Size ◽  
Asymptotic Distribution ◽  
Initial Population ◽  
Asymptotic Results ◽  
The Past ◽  
Offspring Distribution ◽  
Initial Population Size ◽  
Watson Process ◽  
Looking Back

Motivated by the question of the age in a branching population we try to recreate the past by looking back from the currently observed population size. We define a new backward Galton-Watson process and study the case of the geometric offspring distribution with parameter p in detail. The backward process is then the Galton-Watson process with immigration, again with a geometric offspring distribution but with parameter 1-p, and it is also the dual to the original Galton-Watson process. We give the asymptotic distribution of the age when the initial population size is large in supercritical and critical cases. To this end, we give new asymptotic results on the Galton-Watson immigration processes stopped at zero.

Reduction of spermatogonia and testosterone in rat testes flown on space lab-3

1986 ◽  
Vol 44 ◽  
pp. 248-249
Author(s):  
Delbert E. Philpott ◽  
W. Sapp ◽  
C. Williams ◽  
T. Fast ◽  
J. Stevenson ◽  
...  
Keyword(s):  
Social Interaction ◽  
Social Status ◽  
Population Size ◽  
Physiological Response ◽  
Social Rank ◽  
Reproductive Function ◽  
Testicular Development ◽  
Organ Weights ◽  
Reproductive Maturation ◽  
Metabolic Activities

Space Lab 3 (SL-3) was flown on Shuttle Challenger providing an opportunity to measure the effect of spaceflight on rat testes. Cannon developed the idea that organisms react to unfavorable conditions with highly integrated metabolic activities. Selye summarized the manifestations of physiological response to nonspecific stress and he pointed out that atrophy of the gonads always occurred. Many papers have been published showing the effects of social interaction, crowding, peck order and confinement. Flickinger showed delayed testicular development in subordinate roosters influenced by group numbers, social rank and social status. Christian reported increasing population size in mice resulted in adrenal hypertrophy, inhibition of reproductive maturation and loss of reproductive function in adults. Sex organ weights also declined. Two male dogs were flown on Cosmos 110 for 22 days. Fedorova reported an increase of 30 to 70% atypical spermatozoa consisting of tail curling and/or the absence of a tail.

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