scholarly journals Behavioural phase polyphenism in the Australian plague locust ( Chortoicetes terminifera )

2009 ◽  
Vol 5 (3) ◽  
pp. 306-309 ◽  
Author(s):  
Lindsey J. Gray ◽  
Gregory A. Sword ◽  
Michael L. Anstey ◽  
Fiona J. Clissold ◽  
Stephen J. Simpson
Keyword(s):  
Population Density ◽  
Phase Change ◽  
Local Population ◽  
Density Dependent ◽  
Behavioural Changes ◽  
Highly Active ◽  
Phase Polyphenism ◽  
Australian Plague Locust

Swarming and the expression of phase polyphenism are defining characteristics of locust species. Increases in local population density mediate morphological, physiological and behavioural changes within individuals, which correlate with mass marching of juveniles in migratory bands and flying swarms of adults. The Australian plague locust ( Chortoicetes terminifera ) regularly forms migratory bands and swarms, but is claimed not to express phase polyphenism and has accordingly been used to argue against a central role for phase change in locust swarming. We demonstrate that juvenile C. terminifera express extreme density-dependent behavioural phase polyphenism. Isolated-reared juveniles are sedentary and repelled by conspecifics, whereas crowd-reared individuals are highly active and are attracted to conspecifics. In contrast to other major locust species, however, behavioural phase change does not accumulate across generations, but shifts completely within an individual's lifetime in response to a change in population density.

Population Dynamics of the Australian Plague Locust, Chortoicetes Terminifera (Walker) in Central Western New South Wales Iii. Analysis of Population Processes.

1982 ◽  
Vol 30 (4) ◽  
pp. 569 ◽  
Author(s):  
RA Farrow
Keyword(s):  
Large Scale ◽  
Local Population ◽  
Population Fluctuations ◽  
Density Dependent ◽  
Delayed Effects ◽  
South Wales ◽  
Key Factor ◽  
Population Processes ◽  
The Times ◽  
Australian Plague Locust

An analysis of population processes in the Australian plague locust showed that the key factor determining local population fluctuations was net migration. The density-disturbing effects of migration were over-compensated by the delayed effects of natural enemies on immature survival. There was no evidence that the amplitude of fluctuations was controlled at any stage by density-dependent processes, even at the highest densities encountered. Gregarization, although density-dependent and leading to daytime emigration: rarely stabilized population peaks because swarming populations remained relatively static. Densities never reached the carrying capacity of the habitats, even locally, because of the frequency of emigration at night. Local population extinctions due to emigration and low productivity were compensated by eventual immigration at night in favourable weather. In neither situation was the size of night migration shown to be density-dependent, although a spurious effect was detected. Variations in natality and survival had little influence on local population trends but, when synchronized over large areas by unusually favourable weather, influenced the course of large-scale fluctuations. Regional populations were more stable than local ones, due to spatial and temporal differences in reproductive success in a heterogeneous environment, and to peripheral emigration losses. Variations in the synoptic circulation and rainfall at the times of migration and reproduction cause stochastic processes to exert a major control of regional population fluctuations in the Australian plague locust.

scholarly journals Changing Land Use and Population Density Are Degrading Water Quality in the Lower Mekong Basin

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1948
Author(s):  
Flavia Tromboni ◽  
Thomas E. Dilts ◽  
Sarah E. Null ◽  
Sapana Lohani ◽  
Peng Bun Ngor ◽  
...  
Keyword(s):  
Water Quality ◽  
Land Use ◽  
Population Density ◽  
Local Population ◽  
Reference Conditions ◽  
Mekong River ◽  
Land Use Impacts ◽  
Wet Season ◽  
Mekong Basin ◽  
Lower Mekong Basin

Establishing reference conditions in rivers is important to understand environmental change and protect ecosystem integrity. Ranked third globally for fish biodiversity, the Mekong River has the world’s largest inland fishery providing livelihoods, food security, and protein to the local population. It is therefore of paramount importance to maintain the water quality and biotic integrity of this ecosystem. We analyzed land use impacts on water quality constituents (TSS, TN, TP, DO, NO3−, NH4+, PO43−) in the Lower Mekong Basin. We then used a best-model regression approach with anthropogenic land-use as independent variables and water quality parameters as the dependent variables, to define reference conditions in the absence of human activities (corresponding to the intercept value). From 2000–2017, the population and the percentage of crop, rice, and plantation land cover increased, while there was a decrease in upland forest and flooded forest. Agriculture, urbanization, and population density were associated with decreasing water quality health in the Lower Mekong Basin. In several sites, Thailand and Laos had higher TN, NO3−, and NH4+ concentrations compared to reference conditions, while Cambodia had higher TP values than reference conditions, showing water quality degradation. TSS was higher than reference conditions in the dry season in Cambodia, but was lower than reference values in the wet season in Thailand and Laos. This study shows how deforestation from agriculture conversion and increasing urbanization pressure causes water quality decline in the Lower Mekong Basin, and provides a first characterization of reference water quality conditions for the Lower Mekong River and its tributaries.

Adjustment of fecundity and sex ratio in response to social environments in a haplodiploid mite

2022 ◽  
Author(s):  
Nuwan Weerawansha ◽  
Qiao Wang ◽  
Xiong Zhao He
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Population Size ◽  
Local Population ◽  
Female Offspring ◽  
Social Environments ◽  
Positive Interaction ◽  
Offspring Sex Ratio ◽  
Offspring Sex ◽  
Large Populations

Animals can adjust reproductive strategies in favour of corporation or competition in response to local population size and density, the two key factors of social environments. However, previous studies usually focus on either population size or density but ignore their interactions. Using a haplodiploid spider mite, Tetranychus ludeni Zacher, we carried out a factorial experiment in the laboratory to examine how ovipositing females adjust their fecundity and offspring sex ratio during their early reproductive life under various population size and density. We reveal that females laid significantly more eggs with increasing population size and significantly fewer eggs with increasing population density. This suggests that large populations favour cooperation between individuals and dense populations increase competition. We demonstrate a significant negative interaction of population size and density that resulted in significantly fewer eggs laid in the large and dense populations. Furthermore, we show that females significantly skewed the offspring sex ratio towards female-biased in small populations to reduce the local mate competition among their sons. However, population density incurred no significant impact on offspring sex ratio, while the significant positive interaction of population size and density significantly increased the proportion of female offspring in the large and dense populations, which will minimise food or space competition as females usually disperse after mating at crowded conditions. These results also suggest that population density affecting sex allocation in T. ludeni is intercorrelated with population size. This study provides evidence that animals can manipulate their reproductive output and adjust offspring sex ratio in response to various social environments, and the interactions of different socio-environmental factors may play significant roles.

Density-Dependent Population Growth

2020 ◽  
pp. 29-46
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Density Dependence ◽  
Multiple Equilibria ◽  
Dynamical Behavior ◽  
Logistic Growth ◽  
Density Dependent ◽  
Per Capita ◽  
Discrete Time Models ◽  
Complex Dynamical Behavior

The observation that no population can grow indefinitely and that most populations persist on ecological timescales implies that mechanisms of population regulation exist. Feedback mechanisms include competition for limited resources, cannibalism, and predation rates that vary with density. Density dependence occurs when per capita birth or death rates depend on population density. Density dependence is compensatory when the population growth rate decreases with population density and depensatory when it increases. The logistic model incorporates density dependence as a simple linear function. A population exhibiting logistic growth will reach a stable population size. Non-linear density-dependent terms can give rise to multiple equilibria. With discrete time models or time delays in density-dependent regulation, the approach to equilibrium may not be smooth—complex dynamical behavior is possible. Density-dependent feedback processes can compensate, up to a point, for natural and anthropogenic disturbances; beyond this point a population will collapse.

Aggregations of masked shrews ( Sorex cinereus ): density-related mating behavior? / Agrégation de musaraignes masquées ( Sorex cinereus ): accouplement relatif à la densité de la population?

Mammalia ◽  
2006 ◽  
Vol 70 (1-2) ◽  
Author(s):  
Thomas J. Maier ◽  
Katherine L. Doyle
Keyword(s):  
Population Density ◽  
Mating Behavior ◽  
High Population ◽  
High Population Density ◽  
Genetic Analyses ◽  
Highly Active ◽  
Sorex Cinereus

AbstractLarge aggregations of shrews have been reported and various explanations offered for this seemingly rare behavior; however, there has been little evidence to support any particular interpretation. We observed two small aggregations of highly active vocalizing Sorex cinereus while performing wildlife surveys in forested habitats in central Massachusetts, USA. These observations, in conjunction with a review of other reports, including genetic analyses, strongly suggest that such aggregations of adult Sorex are associated with mating behavior, more readily observed during periods of high population density. Published accounts of such behavior may be rare because primarily large aggregations have been reported; however, smaller breeding aggregations may be common.

scholarly journals Population density-dependent regulation of exopolysaccharide formation in the hyperthermophilic bacterium Thermotoga maritima

2004 ◽  
Vol 55 (3) ◽  
pp. 664-674 ◽  
Author(s):  
Matthew R. Johnson ◽  
Clemente I. Montero ◽  
Shannon B. Conners ◽  
Keith R. Shockley ◽  
Stephanie L. Bridger ◽  
...  
Keyword(s):  
Population Density ◽  
Thermotoga Maritima ◽  
Density Dependent ◽  
Hyperthermophilic Bacterium ◽  
Density Dependent Regulation

scholarly journals Mapping Changing Population Distribution on the Qinghai–Tibet Plateau since 2000 with Multi-Temporal Remote Sensing and Point-of-Interest Data

2020 ◽  
Vol 12 (24) ◽  
pp. 4059
Author(s):  
Lanhui Li ◽  
Yili Zhang ◽  
Linshan Liu ◽  
Zhaofeng Wang ◽  
Huamin Zhang ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Population Density ◽  
Rural Areas ◽  
Population Distribution ◽  
Local Population ◽  
Tibet Plateau ◽  
Point Of Interest ◽  
Tibet Autonomous Region ◽  
Multi Temporal ◽  
Qinghai Tibet Plateau

Advanced developments have been achieved in urban human population estimation, however, there is still a considerable research gap for the mapping of remote rural populations. In this study, based on demographic data at the town-level, multi-temporal high-resolution remote sensing data, and local population-sensitive point-of-interest (POI) data, we tailored a random forest-based dasymetric approach to map population distribution on the Qinghai–Tibet Plateau (QTP) for 2000, 2010, and 2016 with a spatial resolution of 1000 m. We then analyzed the temporal and spatial change of this distribution. The results showed that the QTP has a sparse population distribution overall; in large areas of the northern QTP, the population density is zero, accounting for about 14% of the total area of the QTP. About half of the QTP showed a rapid increase in population density between 2000 and 2016, mainly located in the eastern and southern parts of Qinghai Province and the central-eastern parts of the Tibet Autonomous Region. Regarding the relative importance of variables in explaining population density, the variables “Distance to Temples” is the most important, followed by “Density of Villages” and “Elevation”. Furthermore, our new products exhibited higher accuracy compared with five recently released gridded population density datasets, namely WorldPop, Gridded Population of the World version 4, and three national gridded population datasets for China. Both the root-mean-square error (RMSE) and mean absolute error (MAE) for our products were about half of those of the compared products except for WorldPop. This study provides a reference for using fine-scale demographic count and local population-sensitive POIs to model changing population distribution in remote rural areas.

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