scholarly journals Accounting for interspecific competition and age structure in demographic analyses of density dependence improves predictions of fluctuations in population size

2019 ◽  
Vol 22 (5) ◽  
pp. 797-806 ◽  
Author(s):  
Marlène Gamelon ◽  
Stefan J. G. Vriend ◽  
Steinar Engen ◽  
Frank Adriaensen ◽  
André A. Dhondt ◽  
...  
Keyword(s):  
Density Dependence ◽  
Interspecific Competition ◽  
Population Size ◽  
Age Structure

Dynamic modes of exploited limited population: results of modeling and numerical study

2016 ◽  
Vol 11 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Г.П. Неверова ◽  
G.P. Neverova
Keyword(s):  
Population Dynamics ◽  
Density Dependence ◽  
Population Size ◽  
Age Structure ◽  
Birth Rate ◽  
Numerical Study ◽  
Dynamic Regime ◽  
Demographic Parameters ◽  
Current Population

The paper investigates the model of population dynamics with age structure and density dependence of birth rate. We consider two situations: 1) the population develops freely and 2) the population is exploited. It was shown that harvesting leads to the stabilization of the dynamics. There is multiregimism, i.e. different dynamic regimes are possible with the same values of demographic parameters. It is shown that even a single harvesting in the current population size could lead to a change of the observed dynamic regime.

scholarly journals Statistical Estimation of Modern Trends and Prospects of the Size and Structure Population of Ukraine

2017 ◽  
pp. 65-72
Author(s):  
Z. О. Palian ◽  
I. H. Bondarenko
Keyword(s):  
Population Size ◽  
Age Structure ◽  
Structural Changes ◽  
Age Groups ◽  
Natural Increase ◽  
Reproductive Age ◽  
Structural Factors ◽  
Forecast Horizon ◽  
The Crimea ◽  
Size And Structure

A balanced change in demographic processes should be considered as a prerequisite and, at the same time, as a result of the stable development of the state. Reproduction intensity depends not only on the character of demographic behavior, but also on the presence of contingents of the population, providing or potentially able to provide for its replacement. The dynamics of Ukrainian population, the transformation of its gender-age structure during the period of independence, taking into account the intensive and structural factors of natural increase and migration, is considered. During 2002-2015, the regime of survival and fertility improved in Ukraine, due to which the depopulation slowed down somewhat. But even these positive changes do not compensate for the loss of population size as a result of systematic aging, reducing the proportion of reproductive contingent and its aging. Significant demographic losses, direct and indirect, were caused by a hybrid war from Russia. Alienation of the territory of the Crimea and parts of Donbas is not only a minus 2.5 million citizens of Ukraine. This is a change in the structure of the population - a decrease in the proportion of older age groups that increase the demographic load and worsen the characteristics of survival and fertility of the maternal generation. In this work are presented the results of the short-term simulation of population size and structure taking into account modern trends of replacements components and existing administrative-territorial changes. Two scenarios of the forecast for 2018 have been developed, and the base year it was taken in 2013, when the Crimea was part of Ukraine. The first, realistic scenario was based on the preservation of the current situation - Ukraine without the annexed Crimea and the occupied part of the Donbas. The second scenario imitates the return to Ukraine of all the lost territories. Simulation showed that the population of Ukraine will be reduced by both scenarios, but to 41.9 million people under the scenario without the occupied and annexed territories and to 44.7 million people in the second scenario. The finish of war will due to slow down the death rate to 14.9%0. The age structure of the population does not differ significantly in two scenarios, because the forecast horizon is very short (4 years). The share of generation of parents and women of reproductive age in both variants of the forecast decreases. However, in the case of returning Crimea, it will be even lower (47.4% vs. 47.5% in the first scenario). The reason for this is the emigration of young and middle-aged people to the mainland of Ukraine and to the Russian Federation, which provided some preferences to the settlers from Ukraine. Expected structural changes combined with the modern life and fertility regime will worsen natural population growth rates in both scenarios. In further research is planned to build trend models of births and deaths that will allow the artificially restore the interrupted time series due to administrative-territorial incomparability of data on demographic events

scholarly journals The mating rate of Drosophila suzukii reduction due to reproductive interference from Drosophila melanogaster

2020 ◽  
Author(s):  
Yongzhuo Chen ◽  
Min Zhang ◽  
Wei Hu ◽  
Jing Li ◽  
Pengcheng Liu ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Interspecific Competition ◽  
Population Size ◽  
Egg Laying ◽  
Significant Decline ◽  
Reproductive Interference ◽  
Drosophila Suzukii ◽  
Offspring Number ◽  
Successful Mating ◽  
Reproductive Activities

Abstract Background Drosophila suzukii is widely distributed. Research has revealed that the presence of Drosophila melanogaster can reduce the emergence and egg laying of D. suzukii. However, the reasons for these phenomena have not yet been reported. To investigate this issue, we sought to answer three questions: Can the presence of D. melanogaster reduce the longevity of D. suzukii? Does D. melanogaster dominate in larval interspecific competition with D. suzukii? Does reproductive interference occur between these species; i.e., do individuals of one species (e.g., D. suzukii) engage in reproductive activities with individuals of the other (e.g., D. melanogaster) such that the fitness of one or both species is reduced? Results The results showed that the adult offspring number of Drosophila suzukii was significantly reduced when this species was reared with Drosophila melanogaster. The larval interspecific competition had no significant effects on Drosophila suzukii longevity or population size. Surprisingly, Drosophila melanogaster imposed reproductive interference on males of Drosophila suzukii, which led to a significant decline in the rate of successful mating of the latter species. Conclusions The presence of Drosophila melanogaster causes the population size of Drosophila suzukii to decrease through reproductive interference, and the rate of successful mating in Drosophila suzukii is significantly reduced in the presence of Drosophila melanogaster.

scholarly journals Investigating three sources of bias in hook-and-line surveys: survey design, gear saturation, and multispecies interactions

2019 ◽  
Vol 76 (2) ◽  
pp. 192-207
Author(s):  
Peter T. Kuriyama ◽  
Trevor A. Branch ◽  
Allan C. Hicks ◽  
John H. Harms ◽  
Owen S. Hamel
Keyword(s):  
Interspecific Competition ◽  
Population Size ◽  
Relative Error ◽  
Statistical Power ◽  
Survey Design ◽  
Biological Information ◽  
Catch Per Unit Effort ◽  
Absolute Relative Error ◽  
Survey Results ◽  
Survey Methodologies

Hook-and-line surveys can be used to estimate population trends in fish species where conventional methods such as trawl, acoustic, visual, or pot surveys cannot be applied. Hook-and-line surveys allow for the collection of biological information, but the resultant indices of abundance may be biased. We designed simulations to address concerns around survey design, hook saturation, and competition among species and found that catch per unit effort (CPUE) declined more slowly than population size across all scenarios. This hyperstability was most prominent when fish were found in high-density patches, and these scenarios have median absolute relative error values roughly three to five times greater than those with more even distributions of fish density. Despite hyperstability, the surveys still had statistical power to detect changes in abundance. Interspecific competition for hooks caused bias in survey results when one species was more aggressive than another. Taken together, our results indicate hook-and-line surveys fill a niche in survey methodologies, but their use and interpretation can be challenged by hyperstability and competition among species.

Response of Daphnia population size and age structure to predation

1975 ◽  
Vol 19 (4) ◽  
pp. 2898-2905
Author(s):  
Nelson G. Hairston ◽  
Robert A. Pastorok
Keyword(s):  
Population Size ◽  
Age Structure ◽  
Daphnia Population ◽  
Size And Age Structure

Differential response of marine populations to climate forcing

2003 ◽  
Vol 60 (8) ◽  
pp. 971-985 ◽  
Author(s):  
Kevin S McCann ◽  
Louis W Botsford ◽  
Alan Hasting
Keyword(s):  
Density Dependence ◽  
Age Structure ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Environmental Variability ◽  
Climate Forcing ◽  
Dungeness Crab ◽  
Cancer Magister ◽  
Environmental Forcing ◽  
Variable Recruitment

In searching for causes of fluctuations in marine populations, investigators often assume that populations respond on the same time scale as the environmental forcing period, but this may not hold true. Here we show how the response of populations to variable recruitment changes with the degree of overcompensation using models of two species with similar age structure but different density-dependent recruitment, chinook salmon (Oncorhynchus tshawytscha) and Dungeness crab (Cancer magister). For compensatory density dependence, as in chinook salmon, variability in recruitment tends to follow the period in environmental variability over all time scales. For overcompensatory density dependence, as in Dungeness crab, variability in recruitment follows the environmental variability only for periods much greater than the maximum age of the population. For periods in environmental variability less than the maximum age, the dominant period of the population response is slightly larger than the length of the age structure. Here, strong overcompensatory recruitment acts to filter out potentially good recruitment years, resulting in dominant periodicities slightly larger than the length of the age structure. These mechanisms appear to explain the differences between observed spectra of Dungeness crab and chinook salmon.

scholarly journals Evidence for r - and K -selection in a wild bird population: a reciprocal link between ecology and evolution

2016 ◽  
Vol 283 (1829) ◽  
pp. 20152411 ◽  
Author(s):  
Bernt-Erik Sæther ◽  
Marcel E. Visser ◽  
Vidar Grøtan ◽  
Steinar Engen
Keyword(s):  
Density Dependence ◽  
Population Size ◽  
Clutch Size ◽  
Balancing Selection ◽  
Empirical Support ◽  
Small Population ◽  
Environmental Stochasticity ◽  
Fluctuating Environments ◽  
Population Sizes ◽  
Large Clutch

Understanding the variation in selection pressure on key life-history traits is crucial in our rapidly changing world. Density is rarely considered as a selective agent. To study its importance, we partition phenotypic selection in fluctuating environments into components representing the population growth rate at low densities and the strength of density dependence, using a new stochastic modelling framework. We analysed the number of eggs laid per season in a small song-bird, the great tit, and found balancing selection favouring large clutch sizes at small population densities and smaller clutches in years with large populations. A significant interaction between clutch size and population size in the regression for the Malthusian fitness reveals that those females producing large clutch sizes at small population sizes also are those that show the strongest reduction in fitness when population size is increased. This provides empirical support for ongoing r - and K -selection in this population, favouring phenotypes with large growth rates r at small population sizes and phenotypes with high competitive skills when populations are close to the carrying capacity K . This selection causes long-term fluctuations around a stable mean clutch size caused by variation in population size, implying that r - and K -selection is an important mechanism influencing phenotypic evolution in fluctuating environments. This provides a general link between ecological dynamics and evolutionary processes, operating through a joint influence of density dependence and environmental stochasticity on fluctuations in population size.

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