Demography in relation to population density in two herbivorous marsupials: testing for source?sink dynamics versus independent regulation of population size

Oecologia ◽  
2004 ◽  
Vol 143 (1) ◽  
pp. 70-76 ◽  
Author(s):  
Christopher N. Johnson ◽  
Karl Vernes ◽  
Alison Payne
Keyword(s):  
Population Density ◽  
Population Size ◽  
Source Sink

scholarly journals Population Density or Populations Size. Which Factor Determines Urban Traffic Congestion?

2021 ◽  
Vol 13 (8) ◽  
pp. 4280
Author(s):  
Yu Sang Chang ◽  
Sung Jun Jo ◽  
Yoo-Taek Lee ◽  
Yoonji Lee
Keyword(s):  
Population Density ◽  
Population Size ◽  
Traffic Congestion ◽  
Critical Role ◽  
Small Population ◽  
High Density ◽  
Urban Traffic ◽  
Contradictory Result ◽  
Low Density

A large number of articles have documented that as population density of cities increases, car use declines and public transit use rises. These articles had a significant impact of promoting high-density compact urban development to mitigate traffic congestion. Another approach followed by other researchers used the urban scaling model to indicate that traffic congestion increases as population size of cities increases, thus generating a possible contradictory result. Therefore, this study examines the role of both density and population size on traffic congestion in 164 global cities by the use of Stochastic Impacts by Regression on Population, Affluence and Technology model. We divide 164 cities into the two subgroups of 66 low density cities and 98 high density cities for analysis. The findings from the subgroups analysis indicated a clear-cut difference on the critical role of density in low-density cities and the exclusive role of population size in high-density cities. Furthermore, using threshold regression model, 164 cities are divided into the two regions of large and small population cities to determine population scale advantage of traffic congestion. Our findings highlight the importance of including analysis of subgroups based on density and/or population size in future studies of traffic congestion.

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 Interactions between Kazachstania humilis Yeast Species and Lactic Acid Bacteria in Sourdough

2020 ◽  
Vol 8 (2) ◽  
pp. 240 ◽  
Author(s):  
Belén Carbonetto ◽  
Thibault Nidelet ◽  
Stéphane Guezenec ◽  
Marc Perez ◽  
Diego Segond ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Population Density ◽  
Population Size ◽  
Yeast Species ◽  
Positive Interactions ◽  
Composition And Structure ◽  
Density Analysis ◽  
Sourdough Yeast

Sourdoughs harbor simple microbial communities usually composed of a few prevailing lactic acid bacteria species (LAB) and yeast species. However, yeast and LAB found in sourdough have been described as highly diverse. Even if LAB and yeast associations have been widely documented, the nature of the interactions between them has been poorly described. These interactions define the composition and structure of sourdough communities, and therefore, the characteristics of the final bread product. In this study, the nature of the interactions between strains of two commonly found sourdough yeast species, Kazachstania humilis and Saccharomyces cerevisiae, and lactic acid bacteria isolated from sourdoughs has been analyzed. Population density analysis showed no evidence of positive interactions, but instead revealed neutral or negative asymmetric interaction outcomes. When in coculture, the yeasts´ population size decreased in the presence of LAB regardless of the strain, while the LAB´s population size was rarely influenced by the presence of yeasts. However, a higher maltose depletion was shown in maltose-negative K. humilis and maltose-positive obligately heterofermentative LAB cocultures compared to monocultures. In addition, tested pairs of obligately heterofermentative LAB and K. humilis strains leavened dough as much as couples of LAB and S. cerevisiae strains, while K. humilis strains never leavened dough as much as S. cerevisiae when in monoculture. Taken together, our results demonstrate that even if higher fermentation levels with increased maltose depletion were detected for K. humilis and obligately heterofermentative LAB pairs, these interactions cannot be ecologically classified as positive, leading us to rethink the established hypothesis of coexistence by facilitation in sourdoughs.

Fish population size, and not density, as the determining factor of parasite infection: a case study

Parasitology ◽  
2004 ◽  
Vol 128 (3) ◽  
pp. 305-313 ◽  
Author(s):  
A. M. BAGGE ◽  
R. POULIN ◽  
E. T. VALTONEN
Keyword(s):  
Species Richness ◽  
Population Density ◽  
Population Size ◽  
Fish Population ◽  
Host Population ◽  
Fish Length ◽  
Total Fish ◽  
Infection Parameters ◽  
The Mean

The diversity and abundance of parasites vary widely among populations of the same host species. These infection parameters are, to some extent, determined by characteristics of the host population or of its habitat. Recent studies have supported predictions derived from epidemiological models regarding the influence of host population density: parasite abundance and parasite species richness are expected to increase with increasing host population density, at least for directly transmitted parasites. Here, we test this prediction using a natural system in which populations of the crucian carp, Carassius carassius (L.), occur alone, with no other fish species, in a series of 9 isolated ponds in Finland. The ectoparasite communities in these fish populations consist of only 4 species of monogeneans (Dactylogyrus formosus, D. wegeneri, D. intermedius and Gyrodactylus carassii); the total and relative abundance of these 4 species varies among ponds, with one or two of the species missing from certain ponds. Across ponds, only one factor, total fish population size, explained a significant portion of the variance in both the mean number of monogenean species per fish and the mean total abundance of monogenean individual per fish. In contrast, fish population density did not influence either monogenean abundance or species richness, and neither did any of the other variables investigated (mean fish length per pond, number of fish examined per pond, distance to the nearest lake, and several water quality measures). In our system, proximity among fish individuals (i.e. host population density) may not be relevant to the proliferation of monogeneans; instead, the overall availability of host individuals in the host population appeared to be the main constraint limiting parasite population growth.

Cultural Evolution, Suicide and Homicide

1996 ◽  
Vol 79 (1) ◽  
pp. 334-334 ◽  
Author(s):  
David Lester
Keyword(s):  
Population Density ◽  
Population Size ◽  
Cultural Evolution ◽  
Suicide Rate ◽  
Homicide Rates

The ratio of the suicide rate to the sum of the suicide and homicide rates was not associated with the population size or population density of a sample of nations in 1980

scholarly journals Spread of new mutations through space

2022 ◽  
Author(s):  
Kyle Shaw ◽  
Peter Beerli
Keyword(s):  
Population Density ◽  
Population Size ◽  
Simulation Software ◽  
Effective Population ◽  
Random Drift ◽  
Rate Of Spread ◽  
Large Populations ◽  
Discrete Population ◽  
Explicit Simulation ◽  
New Mutations

The terms population size and population density are often used interchangeably, when in fact they are quite different. When viewed in a spatial landscape, density is defined as the number of individuals within a square unit of distance, while population size is simply the total count of a population. In discrete population genetics models, the effective population size is known to influence the interaction between selection and random drift with selection playing a larger role in large populations while random drift has more influence in smaller populations. Using a spatially explicit simulation software we investigate how population density affects the flow of new mutations through a geographical space. Using population density, selectional advantage, and dispersal distributions, a model is developed to predict the speed at which the new allele will travel, obtaining more accurate results than current diffusion approximations provide. We note that the rate at which a neutral mutation spreads begins to decay over time while the rate of spread of an advantageous allele remains constant. We also show that new advantageous mutations spread faster in dense populations.

scholarly journals Quantifying whether different demographic models produce incongruent results on population dynamics of two long-term studied rodent species

2017 ◽  
Vol 3 (1) ◽  
pp. 18-26
Author(s):  
Giovanni Amori ◽  
Valentina De Silvestro ◽  
Paolo Ciucci ◽  
Luca Luiselli
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Population Size ◽  
Myodes Glareolus ◽  
Suitable Model ◽  
Demographic Model ◽  
Apodemus Flavicollis ◽  
Demographic Models ◽  
Long Term Studies

Abstract1. Population density (ind/ha) of long-term (>15 years) series of CMR populations, using distinct demographic models designed for both open and closed populations, were analysed for two sympatric species of rodents (Myodes glareolus and Apodemus flavicollis) from a mountain area in central Italy, in order to test the relative performance of various employed demographic models. In particular, the hypothesis that enumeration models systematically underestimate the population size of a given population was tested.2. Overall, we compared the performance of 7 distinct demographic models, including both closed and open models, for each study species. Although the two species revealed remarkable intrinsic differences in demography traits (for instance, a lower propensity for being recaptured in Apodemus flavicollis), the Robust Design appeared to be the best fitting model, showing that it is the most suitable model for long-term studies.3. Among the various analysed demographic models, Jolly-Seber returned the lower estimates of population density for both species. Thus, this demographic model could not be suggested for being applied for long-term studies of small mammal populations because it tends to remarkably underestimate the effective population size. Nonetheless, yearly estimates of population density by Jolly-Seber correlated positively with yearly estimates of population density by closed population models, thus showing that interannual trends in population dynamics were uncovered by both types of demographic models, although with different values in terms of true population size.

LAYER PERFORMANCE IN COLONY CAGES AS RELATED TO STOCKING DENSITY AND POPULATION SIZE

1977 ◽  
Vol 57 (4) ◽  
pp. 785-792 ◽  
Author(s):  
A. T. HILL
Keyword(s):  
Population Density ◽  
Population Size ◽  
Feed Efficiency ◽  
Egg Production ◽  
Egg Quality ◽  
Stocking Density ◽  
White Leghorns ◽  
High Level

Two commercial strains of White Leghorns were each measured for egg production, egg quality, feed efficiency and net egg income over feed and bird costs. The birds were in populations of 18, 24 and 30 per colony cage each at densities of 310, 387 and 464 cm2 per bird. In addition, a 10th population–density combination of 24 birds, caged singly at 619 cm2, served as controls. A total of 3,840 birds were measured for 60 wk in two tests, each with four replications. Results were also related directly to an earlier experiment with populations of 3, 6 and 12 birds per cage at the same densities. The performances of populations of 18, 24 and 30 birds were equal and poor relative to the controls. All three populations at 387 cm2 per bird were superior to those at 310 cm2 and equal to 464 cm2 in egg production and net egg income. In comparisons with more conventionally caged populations of 3, 6 and 12 birds, colony caged layers yielded significantly (P < 0.01) fewer eggs and less net egg income. Mortality was significantly (P < 0.05) greater for colony caged layers. It was concluded that the general high level of stress in colony cages prevented the expression of declining performance normally expected with population increases, yet effects due to density were still evident.

Density-Dependent Response of the Pea Aphid (Hemiptera: Aphididae) to Imidacloprid

2007 ◽  
Vol 42 (2) ◽  
pp. 200-206 ◽  
Author(s):  
Paulina E. Kramarz ◽  
John E. Banks ◽  
John D. Stark
Keyword(s):  
Population Density ◽  
Population Size ◽  
Acyrthosiphon Pisum ◽  
Pea Aphid ◽  
Stressful Event ◽  
Relative Reduction ◽  
Initial Population ◽  
Lower Growth ◽  
Final Population ◽  
Initial Starting

A study was conducted to determine the influence of initial population density on the effects of pesticides on pea aphid, Acyrthosiphon pisum (Harris), populations. Three initial starting densities of pea aphids (147, 295 and 590 aphids per m2) were exposed to no pesticide or imidacloprid at rates of 1 or 5 g ai/ha on broad bean plants, Vicia faba L., in a greenhouse. Ten days later, population size was assessed. In general, higher initial aphid population density resulted in a higher final population density for all imidacloprid concentrations. However, population growth rates for populations started with the highest density (590 aphids per m2) were significantly lower than those with initial densities of 147 and 295 aphids per m2. This was due to a relative reduction in population number. Populations begun with 147 aphids per m2 were 50% lower after exposure to the highest concentration of imidacloprid, whereas the populations begun with 295 and 590 aphids per m2 were 42 and 25% of the starting population size, respectively. Therefore, the pesticide actually had a greater impact on the population started with the highest density. This can be explained by a synergistic effect of the pesticide and crowding. The lower growth rate observed in the population started with the highest density was probably due to crowding, whereby aphids approached the carrying capacity and were stressed. Even though these populations were reduced, final density was still sufficiently high to limit resources. These results indicate that the response of organisms to stress is influenced by population density at the start of a stressful event, such as a pesticide exposure. Therefore, different experimental designs may result in different outcomes and starting population densities must be carefully considered when designing population-level toxicological experiments.

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