Variations in Population Density, Movement, and Rickettsial Infection Rates in a Local Population of Dermacentor variabilis (Acarina: Ixodidae) Ticks in the Piedmont of Georgia 1

1983 ◽  
Vol 12 (6) ◽  
pp. 1737-1746 ◽  
Author(s):  
Verne F. Newhouse
Keyword(s):  
Population Density ◽  
Local Population ◽  
Dermacentor Variabilis ◽  
Infection Rates ◽  
Rickettsial Infection

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.

scholarly journals The COVID-19 Pandemic Situation in Malaysia: Lessons Learned from the Perspective of Population Density

2021 ◽  
Vol 18 (12) ◽  
pp. 6566
Author(s):  
Siew Bee Aw ◽  
Bor Tsong Teh ◽  
Gabriel Hoh Teck Ling ◽  
Pau Chung Leng ◽  
Weng Howe Chan ◽  
...  
Keyword(s):  
Population Density ◽  
Pearson Correlation ◽  
Strong Relationship ◽  
Lessons Learned ◽  
P Value ◽  
Population Census ◽  
Infection Rates ◽  
Health Official ◽  
Contagious Diseases ◽  
Spatio Temporal

This paper attempts to ascertain the impacts of population density on the spread and severity of COVID-19 in Malaysia. Besides describing the spatio-temporal contagion risk of the virus, ultimately, it seeks to test the hypothesis that higher population density results in exacerbated COVID-19 virulence in the community. The population density of 143 districts in Malaysia, as per data from Malaysia’s 2010 population census, was plotted against cumulative COVID-19 cases and infection rates of COVID-19 cases, which were obtained from Malaysia’s Ministry of Health official website. The data of these three variables were collected between 19 January 2020 and 31 December 2020. Based on the observations, districts that have high population densities and are highly inter-connected with neighbouring districts, whether geographically, socio-economically, or infrastructurally, tend to experience spikes in COVID-19 cases within weeks of each other. Using a parametric approach of the Pearson correlation, population density was found to have a moderately strong relationship to cumulative COVID-19 cases (p-value of 0.000 and R2 of 0.415) and a weak relationship to COVID-19 infection rates (p-value of 0.005 and R2 of 0.047). Consequently, we provide several non-pharmaceutical lessons, including urban planning strategies, as passive containment measures that may better support disease interventions against future contagious diseases.

scholarly journals Novel Identification of Dermacentor variabilis Arp2/3 Complex and Its Role in Rickettsial Infection of the Arthropod Vector

PLoS ONE ◽  
2014 ◽  
Vol 9 (4) ◽  
pp. e93768 ◽  
Author(s):  
Natthida Petchampai ◽  
Piyanate Sunyakumthorn ◽  
Mark L. Guillotte ◽  
Victoria I. Verhoeve ◽  
Kaikhushroo H. Banajee ◽  
...  
Keyword(s):  
Dermacentor Variabilis ◽  
Rickettsial Infection ◽  
Arthropod Vector

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.

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.

scholarly journals Viscous Populations and Their Support for Reciprocal Cooperation

2003 ◽  
Vol 9 (3) ◽  
pp. 327-334 ◽  
Author(s):  
James A. R. Marshall ◽  
Jonathan E. Rowe
Keyword(s):  
Population Density ◽  
Local Population ◽  
Limited Mobility ◽  
Spatially Distributed ◽  
Tit For Tat ◽  
Levels Of Support ◽  
Globally Stable ◽  
Viscous Populations

Viscous populations (those whose members are spatially distributed and have limited mobility and locality of interaction and mating) have been proposed to support the evolution of reciprocal cooperation among self-interested individuals. Here we present a model of such a population and describe how its examination yielded the realization that different classes of viscous populations exist with differing levels of support for reciprocal cooperation. Specifically we find from our model that, in a spatially distributed population with increased viscosity, the reciprocally cooperative tit-for-tat strategy may not be globally stable due to a corresponding increase in local population density.

Impact of bovine tuberculosis on a population of brushtail possums (Trichosurus vulpecula Kerr) in the Orongorongo Valley, New Zealand

2004 ◽  
Vol 31 (4) ◽  
pp. 389 ◽  
Author(s):  
A. Arthur ◽  
D. Ramsey ◽  
M. Efford
Keyword(s):  
Overall Survival ◽  
New Zealand ◽  
Population Density ◽  
Bovine Tuberculosis ◽  
Local Population ◽  
Trichosurus Vulpecula ◽  
Considerable Uncertainty ◽  
Highly Sensitive ◽  
Competing Models ◽  
The Impact

Brushtail possums are the main wildlife vectors of bovine tuberculosis (Tb) in New Zealand. Possum–Tb models form the basis of possum control aimed at eradicating the disease, and yet competing models show different behaviour, and are highly sensitive to parameters about which there is considerable uncertainty. One area of great uncertainty is the impact of the disease on possum populations. We investigated the impact of Tb on a local population of brushtail possums in the Orongorongo Valley, Wellington. Bovine Tb was first detected in 1997 at one site within an intensively studied population, but has not been detected in another intensively studied population 3 km away since the early 1980s. Using a Before-After-Control-Impact (BACI) analysis, detection of Tb coincided with a 42% (95% CI = 23–56%) reduction in the odds of apparent yearly survival of a possum >17 months of age, i.e. a decrease in yearly survival from 0.85 to 0.77 in 'good' years, and a decrease from 0.71 to 0.60 in 'bad' years. This suggests that Tb had a significant impact on overall survival. However, there was no impact on local population density in September each year due to compensatory recruitment.

Initiation of breeding after winter in bank voles: effects of food and population density

2001 ◽  
Vol 79 (10) ◽  
pp. 1743-1753 ◽  
Author(s):  
Jana A Eccard ◽  
Hannu Ylönen
Keyword(s):  
Population Density ◽  
Bank Vole ◽  
Local Density ◽  
Local Population ◽  
Food Supplements ◽  
Clethrionomys Glareolus ◽  
Environmental Stability ◽  
Food Treatment ◽  
Bank Voles ◽  
Winter Food

We studied factors causing variation in the initiation of reproduction after winter in the bank vole (Clethrionomys glareolus), an iteroparous seasonal breeder, by offering different winter food supplements and monitoring local density variation. We used either sunflower seeds or barley to supplement the diet of populations of bank voles in grassland enclosures. In a parallel experiment we used spruce seeds, a natural winter food, to supplement the diet of bank vole populations in unfenced spruce forest. Survival, maturation, and breeding were monitored by livetrapping. Population density decreased during winter in grassland enclosures and remained constant in the forest, with no difference between food treatments. Breeding was initiated earlier in the grassland enclosures than in the forest, probably because of the supplemental food supply in both seed treatments and social and environmental stability in enclosures. Within both experiments, we found no differences in timing of parturition between food treatments. Inter actions of food treatment with density of females influenced the time of initiation of breeding in both experiments. At low densities, breeding started up to 1 month earlier than the population average. At high densities, a proportion of females did not breed during spring. Massive food supplements advanced the initiation of breeding, but among animals with similar food supplies, local population density seemed to have stronger regulatory effects. Local density variations may therefore create asynchronous breeding patterns within populations under similar wintering conditions.

scholarly journals Correlation between COVID-19 Morbidity and Mortality Rates in Japan and Local Population Density, Temperature, and Absolute Humidity

2020 ◽  
Vol 17 (15) ◽  
pp. 5477 ◽  
Author(s):  
Sachiko Kodera ◽  
Essam A. Rashed ◽  
Akimasa Hirata
Keyword(s):  
Population Density ◽  
Local Population ◽  
Absolute Humidity ◽  
Mortality Rates ◽  
Morbidity And Mortality ◽  
Maximum Temperature ◽  
Daily Maximum ◽  
P Value ◽  
Nursing Home Patients ◽  
Higher Temperature

This study analyzed the morbidity and mortality rates of the coronavirus disease (COVID-19) pandemic in different prefectures of Japan. Under the constraint that daily maximum confirmed deaths and daily maximum cases should exceed 4 and 10, respectively, 14 prefectures were included, and cofactors affecting the morbidity and mortality rates were evaluated. In particular, the number of confirmed deaths was assessed, excluding cases of nosocomial infections and nursing home patients. The correlations between the morbidity and mortality rates and population density were statistically significant (p-value < 0.05). In addition, the percentage of elderly population was also found to be non-negligible. Among weather parameters, the maximum temperature and absolute humidity averaged over the duration were found to be in modest correlation with the morbidity and mortality rates. Lower morbidity and mortality rates were observed for higher temperature and absolute humidity. Multivariate linear regression considering these factors showed that the adjusted determination coefficient for the confirmed cases was 0.693 in terms of population density, elderly percentage, and maximum absolute humidity (p-value < 0.01). These findings could be useful for intervention planning during future pandemics, including a potential second COVID-19 outbreak.

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