scholarly journals Evolutionary effects of density-dependent selection in plants

1993 ◽  
Vol 62 (1) ◽  
pp. 57-62 ◽  
Author(s):  
G. Namkoong ◽  
J. Bishir ◽  
J. H. Roberds
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Energy Allocation ◽  
Gene Frequencies ◽  
Population Growth Rates ◽  
Stable Periodic ◽  
Density Dependent Selection ◽  
Allocation Strategies ◽  
Periodic Changes

SummaryThe evolution of traits that affect genotypic responses to density regulated resources can be strongly affected by population dynamics in ways that are unpredictable from individual viability or reproduction potentials. Genotypes that are most efficient in utilizing energy may not always displace less efficient ones, and the evolution of energy allocation strategies may not always favour reproductive fitness because of their effects on destabilizing population growth rates. Furthermore, genetic polymorphisms in single loci that affect such traits can be maintained in populations with stable, periodic changes in population size and gene frequencies in the absence of heterozygote superiority. In fact, in the models investigated in this paper, the polymorphism is maintained, even in the absence of equilibrium genotypic frequencies.

Life history and environmental influences on population dynamics in sockeye salmon

2014 ◽  
Vol 71 (8) ◽  
pp. 1198-1208 ◽  
Author(s):  
Douglas C. Braun ◽  
John D. Reynolds
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Sockeye Salmon ◽  
Life History Traits ◽  
Relative Importance ◽  
Population Growth Rates ◽  
Habitat Variables

Understanding linkages among life history traits, the environment, and population dynamics is a central goal in ecology. We compared 15 populations of sockeye salmon (Oncorhynchus nerka) to test general hypotheses for the relative importance of life history traits and environmental conditions in explaining variation in population dynamics. We used life history traits and habitat variables as covariates in mixed-effect Ricker models to evaluate the support for correlates of maximum population growth rates, density dependence, and variability in dynamics among populations. We found dramatic differences in the dynamics of populations that spawn in a small geographical area. These differences among populations were related to variation in habitats but not life history traits. Populations that spawned in deep water had higher and less variable population growth rates, and populations inhabiting streams with larger gravels experienced stronger negative density dependence. These results demonstrate, in these populations, the relative importance of environmental conditions and life histories in explaining population dynamics, which is rarely possible for multiple populations of the same species. Furthermore, they suggest that local habitat variables are important for the assessment of population status, especially when multiple populations with different dynamics are managed as aggregates.

scholarly journals Weather influences M. arvalis reproduction but not population dynamics in a 17-year time series

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Patrick Giraudoux ◽  
Petra Villette ◽  
Jean-Pierre Quéré ◽  
Jean-Pierre Damange ◽  
Pierre Delattre
Keyword(s):  
Time Series ◽  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Demographic Data ◽  
Common Vole ◽  
Empirical Work ◽  
Weather Conditions ◽  
Female Reproduction ◽  
Population Growth Rates

Abstract Rodent outbreaks have plagued European agriculture for centuries, but continue to elude comprehensive explanation. Modelling and empirical work in some cyclic rodent systems suggests that changes in reproductive parameters are partly responsible for observed population dynamics. Using a 17-year time series of Microtus arvalis population abundance and demographic data, we explored the relationship between meteorological conditions (temperature and rainfall), female reproductive activity, and population growth rates in a non-cyclic population of this grassland vole species. We found strong but complex relationships between female reproduction and climate variables, with spring female reproduction depressed after cold winters. Population growth rates were, however, uncorrelated with either weather conditions (current and up to three months prior) or with female reproduction (number of foetuses per female and/or proportion of females reproductively active in the population). These results, coupled with age-structure data, suggest that mortality, via predation, disease, or a combination of the two, are responsible for the large multi-annual but non-cyclic population dynamics observed in this population of the common vole.

scholarly journals Population growth rates: issues and an application

2002 ◽  
Vol 357 (1425) ◽  
pp. 1307-1319 ◽  
Author(s):  
H. Charles J. Godfray ◽  
Mark Rees
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Population Growth Rate ◽  
Population Change ◽  
Evolutionarily Stable Strategy ◽  
Model Systems ◽  
Population Growth Rates

Current issues in population dynamics are discussed in the context of The Royal Society Discussion Meeting 'Population growth rate: determining factors and role in population regulation'. In particular, different views on the centrality of population growth rates to the study of population dynamics and the role of experiments and theory are explored. Major themes emerging include the role of modern statistical techniques in bringing together experimental and theoretical studies, the importance of long-term experimentation and the need for ecology to have model systems, and the value of population growth rate as a means of understanding and predicting population change. The last point is illustrated by the application of a recently introduced technique, integral projection modelling, to study the population growth rate of a monocarpic perennial plant, its elasticities to different life-history components and the evolution of an evolutionarily stable strategy size at flowering.

scholarly journals Pattern of variation in avian population growth rates

2002 ◽  
Vol 357 (1425) ◽  
pp. 1185-1195 ◽  
Author(s):  
Bernt–Erik Sæther ◽  
Steinar Engen
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Specific Growth ◽  
Population Projections ◽  
Stochastic Effects ◽  
Density Regulation ◽  
Population Growth Rates ◽  
Specific Growth Rates

A central question in population ecology is to understand why population growth rates differ over time. Here, we describe how the long–term growth of populations is not only influenced by parameters affecting the expected dynamics, for example form of density dependence and specific population growth rate, but is also affected by environmental and demographic stochasticity. Using long–term studies of fluctuations of bird populations, we show an interaction between the stochastic and the deterministic components of the population dynamics: high specific growth rates at small densities r 1 are typically positively correlated with the environmental variance σ e 2 . Furthermore, θ, a single parameter describing the form of the density regulation in the theta–logistic density–regulation model, is negatively correlated with r 1 . These patterns are in turn correlated with interspecific differences in life–history characteristics. Higher specific growth rates, larger stochastic effects on the population dynamics and stronger density regulation at small densities are found in species with large clutch sizes or high adult mortality rates than in long–lived species. Unfortunately, large uncertainties in parameter estimates, as well as strong stochastic effects on the population dynamics, will often make even short–term population projections unreliable. We illustrate that the concept of population prediction interval can be useful in evaluating the consequences of these uncertainties in the population projections for the choice of management actions.

scholarly journals Age-structured Jolly-Seber model expands inference and improves parameter estimation from capture-recapture data

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0252748
Author(s):  
Nathan J. Hostetter ◽  
Nicholas J. Lunn ◽  
Evan S. Richardson ◽  
Eric V. Regehr ◽  
Sarah J. Converse
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Age Structure ◽  
Growth Rates ◽  
Lifetime Reproductive Success ◽  
Polar Bears ◽  
Population Growth Rates ◽  
Age Dependent ◽  
Capture Recapture ◽  
Age Structured

Understanding the influence of individual attributes on demographic processes is a key objective of wildlife population studies. Capture-recapture and age data are commonly collected to investigate hypotheses about survival, reproduction, and viability. We present a novel age-structured Jolly-Seber model that incorporates age and capture-recapture data to provide comprehensive information on population dynamics, including abundance, age-dependent survival, recruitment, age structure, and population growth rates. We applied our model to a multi-year capture-recapture study of polar bears (Ursus maritimus) in western Hudson Bay, Canada (2012–2018), where management and conservation require a detailed understanding of how polar bears respond to climate change and other factors. In simulation studies, the age-structured Jolly-Seber model improved precision of survival, recruitment, and annual abundance estimates relative to standard Jolly-Seber models that omit age information. Furthermore, incorporating age information improved precision of population growth rates, increased power to detect trends in abundance, and allowed direct estimation of age-dependent survival and changes in annual age structure. Our case study provided detailed evidence for senescence in polar bear survival. Median survival estimates were lower (<0.95) for individuals aged <5 years, remained high (>0.95) for individuals aged 7–22 years, and subsequently declined to near zero for individuals >30 years. We also detected cascading effects of large recruitment classes on population age structure, which created major shifts in age structure when these classes entered the population and then again when they reached prime breeding ages (10–15 years old). Overall, age-structured Jolly-Seber models provide a flexible means to investigate ecological and evolutionary processes that shape populations (e.g., via senescence, life expectancy, and lifetime reproductive success) while improving our ability to investigate population dynamics and forecast population changes from capture-recapture data.

scholarly journals Estimates of regional annual abundance and population growth rates of white sharks off central California

2021 ◽  
Vol 257 ◽  
pp. 109104
Author(s):  
Paul E. Kanive ◽  
Jay J. Rotella ◽  
Taylor K. Chapple ◽  
Scot D. Anderson ◽  
Timothy D. White ◽  
...  
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Central California ◽  
Population Growth Rates

scholarly journals ATIVIDADE ACARICIDA DE ÓLEOS ESSENCIAIS SOBRE Tetranychus ludeni (Zacher) (Acari: Tetranychidae) EM DUAS CULTIVARES DE ALGODOEIRO

Nativa ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 469
Author(s):  
Yasmin Bruna de Siqueira Bezerra ◽  
José Vargas de Oliveira ◽  
Taciana Keila dos Anjos Ramalho ◽  
Douglas Rafael e Silva Barbosa ◽  
Carlos Romero Ferreira de Oliveira ◽  
...  
Keyword(s):  
Population Growth ◽  
Essential Oils ◽  
Growth Rates ◽  
Ocimum Basilicum ◽  
Alternative Control ◽  
Population Growth Rates ◽  
Colored Cotton ◽  
Potential Alternative ◽  
Tetranychus Ludeni ◽  
Corymbia Citriodora

O presente trabalho teve como objetivo avaliar os efeitos repelentes e as taxas de crescimento populacional de óleos essenciais de Corymbia citriodora, Ocimum basilicum e Myracroduon urundeuva sobre o ácaro vermelho Tetranychus ludeni (Zacher) em algodoeiro de fibra colorida. Para o teste de repelência, óleos de Corymbia citriodora, Ocimum basilicum e Myracroduon urundeuva foram testados em diferentes concentrações sobre fêmeas adultas de T. ludeni, assim como para o teste de crescimento populacional, onde as cultivares foram tratadas com óleos essenciais.  O efeito repelente foi verificado para todos os óleos testados nas duas cultivares de algodão colorida. As taxas instantâneas de crescimento populacional para T. ludeni nas cultivares de algodoeiro BRS Verde e BRS Rubi foram todas positivas (ri> 0), indicando que a população está em estado ascendente, no entanto, a população cresceu a uma taxa menor quando comparada ao controle. Os óleos essenciais de C. citriodora, O. basilicum e M. urundeuva apresentam efeito acaricida e potencial controle alternativo de T. ludeni em algodoeiro de fibras coloridas sem causar danos ao algodoeiro.Palavras-chave: ácaro vermelho; algodão colorido; controle alternativo; taxa instantânea de crescimento; repelência. ACARICIDAL ACTIVITY OF ESSENTIAL OILS ON RED MITETetranychus ludeni (Zacher) (Acari: Tetranychidae) IN TWO COTTON CULTIVARS ABSTRACT: The objective of this work was to evaluate the repellent and population growth rates of essential oils of Corymbia citriodora, Ocimum basilicum and Myracroduon urundeuva on the red mite Tetranychus ludeni (Zacher) in cotton fiber. For the repellency test, oils of Corymbia citriodora, Ocimum basilicum and Myracroduon urundeuva were tested in different concentrations on adult females of T. ludeni, as well as for the population growth test, where the cultivars were treated with essential oils. The repellent effect was verified for all tested oils the two cultivars of colored cotton. The instant population growth rates for T. ludeni in the cultivars BRS Verde and BRS Rubi were all positive (ri> 0), indicating that the population is in an upward, however, the population grew at a lower rate when compared to the control. The essential oils of C. citriodora, O. basilicum and M. urundeuva have an acaricidal effect and potential alternative control of T. ludeni in cotton from colored fibers without causing damage to the cotton.Keywords: Red mite; colored cotton; essential oils; instant growth rate; repellency.

An Evaluation of RNA–DNA Ratio as a Measure of Long-Term Growth in Fish Populations

1973 ◽  
Vol 30 (2) ◽  
pp. 195-199 ◽  
Author(s):  
Terry A. Haines
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Growth Rates ◽  
Population Growth Rate ◽  
Environmental Changes ◽  
Age Distribution ◽  
Smallmouth Bass ◽  
Fish Populations ◽  
Population Growth Rates

The value of RNA–DNA ratio as a measure of long-term growth of fish populations under semi-natural conditions and when subjected to environmental manipulations was determined. Populations of carp and smallmouth bass of known age distribution were established in artificial ponds maintained at two fertility levels. After 15 months, population growth rates (as percent increase in weight) and RNA–DNA ratios of muscle tissue from selected fish were measured. Each species exhibited a range of population growth rates. The relation between population growth rate and individual fish RNA–DNA ratio for each species was significant. When reproduction occurred, the relation was not significant unless young-of-the-year fish were excluded from population growth rate calculations. Age of fish was also found to have an important effect on RNA–DNA ratio, with the ratio being higher in younger fish.RNA–DNA ratio can be a reliable indicator of long-term population growth in fish when population age structure is known and recruitment is controlled. The method has potential for use in detecting response to environmental changes before growth rate changes become severe.

Past, Present and Future Population Growth and Urban Management in Zimbabwe

2018 ◽  
pp. 1197-1214
Author(s):  
Innocent Chirisa ◽  
Aaron Maphosa ◽  
Lazarus Zanamwe ◽  
Elmond Bandauko ◽  
Liaison Mukarwi
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Urban Population ◽  
Urban Infrastructure ◽  
Natural Increase ◽  
Urban Migration ◽  
Urban Management ◽  
Population Growth Rates ◽  
Secondary Sources ◽  
Urban Population Growth

The central focus of this chapter is to analyse the urban population growth–urban management nexus in Zimbabwean cities. These cities are registering rapid population growth rates, due mainly to massive rural to urban migration and natural increase. Ideally, rapid urban population growth rates should be proportionate to urban infrastructure, facilities and services. This is not in the case in Zimbabwean cities, where the development of informal settlements, rising urban poverty, dilapidated urban infrastructure and other urban developmental challenges are rampant. Drawing from Malthusian theory, the current conditions in Zimbabwean cities represents that stage where the positive and negative checks are expected. In putting together this chapter, we used archival sources such as newspapers, government reports and other secondary sources. We conclude that planning initiatives and population control measures need to be used in Zimbabwean cities to address inefficiency and urban management challenges, which may be compromising urban sustainability. This study provides evidence-based information that urban local authorities may use to formulate policies to manage urban problems.

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