Variation In Population Size Research Articles

Analysis of Transparency in the Municipal Chambers of Pernambuco/Brazil Part of the Information Access Law

The aim of this study is to analyze the transparency of public information in electronic portals of Municipal Chambers of Pernambuco. It is a descriptive research with quali-quantitative approach, and the data collection procedure is documentary research. Websites of 169 Municipal Chambers of cities that have population beyond ten thousand inhabitants were analyzed, based on indicators proposed by the Information Access Law, in its first paragraph of Article 8. The compliance level was established through six indicators for which a grade criterion was determined: a point to each item that was observed and zero to when it was not observed. After descriptive statistics were carried out, it was observed that the obtained results reached 30% of compliance in ranking of the most transparent, which is a value considered very low. Moreover, from analyzed variables (Population Size and Ranking; Population Size and Transparency; Ranking and total Revenue; Transparency and total Revenue) it was confirmed that only Population Size and Ranking have a positive relationship. Therefore, the compliance level of the Information Access Law is still in a remote stage from reaching transparency and it is justified by the amount of analyzed articles, bringing unsatisfactory results, considering the Law has been effective since 2012.

Dynamics Analysis of a Nonlinear Stochastic SEIR Epidemic System with Varying Population Size.

This paper considers a stochastic susceptible exposed infectious recovered (SEIR) epidemic model with varying population size and vaccination. We aim to study the global dynamics of the reduced nonlinear stochastic proportional differential system. We first investigate the existence and uniqueness of global positive solution of the stochastic system. Then the sufficient conditions for the extinction and permanence in mean of the infectious disease are obtained. Furthermore, we prove that the solution of the stochastic system has a unique ergodic stationary distribution under appropriate conditions. Finally, the discussion and numerical simulation are given to demonstrate the obtained results.

Predation and nutrients drive population declines in breeding waders.

Allee effects are defined as a decline in per capita fitness at low population density. We hypothesized that predation reduces population size of breeding waders and thereby the efficiency of predator deterrence, while total nitrogen through its effects on primary and secondary productivity increases population size. Therefore, nest predation could have negative consequences for population size because nest failure generally results in breeding dispersal and hence reduced local population density. To test these predictions, we recorded nest predation in five species of waders for 4,745 nests during 1987-2015 at the nature reserve Tipperne, Denmark. Predation rates were generally negatively related to conspecific and heterospecific population density, but positively related to overall population density of the entire wader community. Nest predation and population density were related to ground water level, management (grazing and mowing), and nutrients. High nest predation with a time lag of one year resulted in low overall breeding population density, while high nutrient levels resulted in higher population density. These two factors accounted for 86% of the variance in population size, presumably due to effects of nest predation on emigration, while nutrient levels increased the level of vegetation cover and the abundance of food in the surrounding brackish water. These findings are consistent with the hypothesis that predation may reduce population density through negative density dependence, while total nitrogen at adjacent shallow water may increase population size. Nest predation rates were reduced by high ground water level in March, grazing by cattle and mowing that affected access to and susceptibility of nests to predators. These effects can be managed to benefit breeding waders.

Use of cast antlers to assess antler size variation in red deer populations: effects of mast seeding, climate and population features in Mediterranean environments

AbstractFundamental understanding of the factors influencing cervid antler size, development and investment has been traditionally drawn from harvest data. However, depending on the hunting tactic, harvest data may not represent a random sample of the population leading to possible inferential biases. Cast antlers may represent an alternative, cost‐effective and non‐invasive method. We used 4756 red deer (Cervus elaphus L.) cast antlers collected during a 10‐year period to evaluate the relationship between annual antler gross score and three key environmental components that determine habitat quality and resource availability in Mediterranean systems: (1) population traits (density and male age structure), (2) acorn yield and (3) a proxy of plant productivity [Real Bioclimatic Index(RBI)]. Population traits and acorn yield were measured before antler formation (autumn/winter) whereas RBI was calculated before (autumn/winter) and during (spring) antler formation. Population traits explained the highest amount of variance in antler score, followed by acorn yield and spring RBI, while no effect was found for autumn/winter RBI. Antler gross score was negatively related to population density but positively associated with acorn yield, spring RBI and male age structure. Interestingly, a significant interaction between population traits and acorn yield suggests a disproportional effect of population traits on antler size during non‐mast years (poor acorn crops), whereas no significant population effect was observed during mast years. Similarly, we found a positive effect of spring RBI on antlers when density was medium or low and/or age structure was balanced or older. These findings have important ecological implications in environments with high inter‐annual resources variability where high population densities lead to strong intraspecific competition during years of low food availability (e.g. during non‐mast years or drier springs), producing large antler size variation. Finally, although cast antlers reflect changes in environmental conditions we do not recommend their use unless reliable data on age structure is available.

Ancestral inference from haplotypes and mutations

We consider inference about the history of a sample of DNA sequences, conditional upon the haplotype counts and the number of segregating sites observed at the present time. After deriving some theoretical results in the coalescent setting, we implement rejection sampling and importance sampling schemes to perform the inference. The importance sampling scheme addresses an extension of the Ewens Sampling Formula for a configuration of haplotypes and the number of segregating sites in the sample. The implementations include both constant and variable population size models. The methods are illustrated by two human Y chromosome datasets.

Single and simultaneous binary mergers in Wright-Fisher genealogies

The Kingman coalescent is a commonly used model in genetics, which is often justified with reference to the Wright-Fisher (WF) model. Current proofs of convergence of WF and other models to the Kingman coalescent assume a constant sample size. However, sample sizes have become quite large in human genetics. Therefore, we develop a convergence theory that allows the sample size to increase with population size. If the haploid population size is N and the sample size is N1∕3−ϵ, ϵ>0, we prove that Wright-Fisher genealogies involve at most a single binary merger in each generation with probability converging to 1 in the limit of large N. Single binary merger or no merger in each generation of the genealogy implies that the Kingman partition distribution is obtained exactly. If the sample size is N1∕2−ϵ, Wright-Fisher genealogies may involve simultaneous binary mergers in a single generation but do not involve triple mergers in the large N limit. The asymptotic theory is verified using numerical calculations. Variable population sizes are handled algorithmically. It is found that even distant bottlenecks can increase the probability of triple mergers as well as simultaneous binary mergers in WF genealogies.

Fitness decline under osmotic stress in Caenorhabditis elegans populations subjected to spontaneous mutation accumulation at varying population sizes.

The consequences of mutations for population fitness depends on their individual selection coefficients and the effective population size. An earlier study of Caenorhabditis elegans spontaneous mutation accumulation lines evolved for 409 generations at three population sizes found thatNe = 1 populations declined significantly in fitness whereas the fitness of larger populations (Ne = 5, 50) was indistinguishable from the ancestral control under benign conditions. To test if larger MA populations harbor a load of cryptic deleterious mutations that are obscured underbenignlaboratory conditions, we measured fitness underosmotic stressvia exposure to hypersaline conditions. The fitness ofNe = 1 lines exhibited a further decline under osmotic stress compared to benign conditions. However, the fitness of larger populations remained indistinguishable from that of the ancestral control. The average effects of deleterious mutations inNe = 1 lines were estimated to be 22% for productivity and 14% for survivorship, exceeding values previously detected underbenignconditions. Our results suggest that fitness decline is due to large effect mutations that are rapidly removed via selection even in small populations, with implications for conservation practices. Genetic stochasticity may not be as potent and immediate a threat to the persistence of small populations as other demographic and environmental stochastic factors.

High spatial variation in population size and symbiotic performance of Rhizobium leguminosarum bv. trifolii with white clover in New Zealand pasture soils.

Biological nitrogen fixation through the legume-rhizobia symbiosis is important for sustainable pastoral production. In New Zealand, the most widespread and valuable symbiosis occurs between white clover (Trifolium repens L.) and Rhizobium leguminosarum bv. trifolii (Rlt). As variation in the population size (determined by most probable number assays; MPN) and effectiveness of N-fixation (symbiotic potential; SP) of Rlt in soils may affect white clover performance, the extent in variation in these properties was examined at three different spatial scales: (1) From 26 sites across New Zealand, (2) at farm-wide scale, and (3) within single fields. Overall, Rlt populations ranged from 95 to >1 x 108 per g soil, with variation similar at the three spatial scales assessed. For almost all samples, there was no relationship between rhizobia population size and ability of the population to fix N during legume symbiosis (SP). When compared with the commercial inoculant strain, the SP of soils ranged between 14 to 143% efficacy. The N-fixing ability of rhizobia populations varied more between samples collected from within a single hill country field (0.8 ha) than between 26 samples collected from diverse locations across New Zealand. Correlations between SP and calcium and aluminium content were found in all sites, except within a dairy farm field. Given the general lack of association between SP and MPN, and high spatial variability of SP at single field scale, provision of advice for treating legume seed with rhizobia based on field-average MPN counts needs to be carefully considered.

A mathematical analysis of Pine Wilt disease with variable population size and optimal control strategies

The present paper describes the dynamics of the Pine Wilt disease with variable population size. The basic mathematical results for the model are presented. The stability analysis of both the disease-free and endemic cases are presented whenever R0 lesser or greater than one, respectively. Further, an optimal control problem is formulated and the necessarily involved results are presented. Moreover, the numerical simulation of the optimal control problem with suggested control strategies for the possible eliminations of the infection in the pine trees population is presented.

On the absence of a correlation between population size and 'toolkit size' in ethnographic hunter-gatherers.

In apparent contradiction to the theoretically predicted effect of population size on the quality/quantity of material culture, statistical analyses on ethnographic hunter-gatherers have shown an absence of correlation between population size and toolkit size. This has sparked a heated, if sometimes tangential, debate as to the usefulness of the theoretical models and as to what modes of cultural transmission humans are capable of and hunter-gatherers rely on. I review the directly relevant theoretical literature and argue that much of the confusion is caused by a mismatch between the theoretical variable and the empirical observable. I then confirm that a model incorporating the appropriate variable does predict a positive association between population size and toolkit size for random oblique, vertical, best-of-K, conformist, anticonformist, success bias and one-to-many cultural transmission, with the caveat that for all populations sampled, the population size has remained constant and toolkit size has reached the equilibrium for this population size. Finally, I suggest three theoretical scenarios, two of them involving variable population size, that would attenuate or eliminate this association and hence help to explain the empirical absence of correlation.This article is part of the theme issue 'Bridging cultural gaps: interdisciplinary studies in human cultural evolution'.

Modeling the Growth and Decline of Pathogen Effective Population Size Provides Insight into Epidemic Dynamics and Drivers of Antimicrobial Resistance.

Nonparametric population genetic modeling provides a simple and flexible approach for studying demographic history and epidemic dynamics using pathogen sequence data. Existing Bayesian approaches are premised on stochastic processes with stationary increments which may provide an unrealistic prior for epidemic histories which feature extended period of exponential growth or decline. We show that nonparametric models defined in terms of the growth rate of the effective population size can provide a more realistic prior for epidemic history. We propose a nonparametric autoregressive model on the growth rate as a prior for effective population size, which corresponds to the dynamics expected under many epidemic situations. We demonstrate the use of this model within a Bayesian phylodynamic inference framework. Our method correctly reconstructs trends of epidemic growth and decline from pathogen genealogies even when genealogical data are sparse and conventional skyline estimators erroneously predict stable population size. We also propose a regression approach for relating growth rates of pathogen effective population size and time-varying variables that may impact the replicative fitness of a pathogen. The model is applied to real data from rabies virus and Staphylococcus aureus epidemics. We find a close correspondence between the estimated growth rates of a lineage of methicillin-resistant S. aureus and population-level prescription rates of n}{}beta-lactam antibiotics. The new models are implemented in an open source R package called skygrowth which is available at https://github.com/mrc-ide/skygrowth.

Spatial patterns of large jellyfish Chrysaora plocamia blooms in the Northern Humboldt Upwelling System in relation to biological drivers and climate

Abstract In the Northern Humboldt Upwelling System (NHUS), one of the most productive ecosystems in the world, the large jellyfish Chrysaora plocamia exhibits high inter-annual variability in population size, often resulting in massive blooms. In this study, we examined the geographic patterns C. plocamia in the NHUS and their spatial overlap with ichthyoplankton, zooplankton, and chlorophyll a concentration (Chl a) during two El Niño (EN) years (1982–1983 and 1986–1987), and a neutral year (2014). During EN years, the spatial extent of C. plocamia medusae was larger than in the neutral year. In 1982–1983, medusae were concentrated mainly in the central-southern and southern regions of Peru, where they were associated with zooplankton, sardine larvae, and Chl a. In 1986–1987, medusae occurred in the northern and southern regions and spatially overlapped with sardine larvae and Chl a, and with zooplankton and anchoveta larvae, respectively. In 2014, medusae occurred mainly in the northern region, where they were associated with zooplankton, Chl a, and anchoveta eggs and larvae. Our results indicate strong EN effects on the distribution and abundance of C. plocamia, which can have consequences for zooplankton and ichthyoplankton abundance, as well as fisheries, in the NHUS.

Public goods games in populations with fluctuating size

Many mathematical frameworks of evolutionary game dynamics assume that the total population size is constant and that selection affects only the relative frequency of strategies. Here, we consider evolutionary game dynamics in an extended Wright–Fisher process with variable population size. In such a scenario, it is possible that the entire population becomes extinct. Survival of the population may depend on which strategy prevails in the game dynamics. Studying cooperative dilemmas, it is a natural feature of such a model that cooperators enable survival, while defectors drive extinction. Although defectors are favored for any mixed population, random drift could lead to their elimination and the resulting pure-cooperator population could survive. On the other hand, if the defectors remain, then the population will quickly go extinct because the frequency of cooperators steadily declines and defectors alone cannot survive. In a mutation–selection model, we find that (i) a steady supply of cooperators can enable long-term population survival, provided selection is sufficiently strong, and (ii) selection can increase the abundance of cooperators but reduce their relative frequency. Thus, evolutionary game dynamics in populations with variable size generate a multifaceted notion of what constitutes a trait’s long-term success.

Detecting Recent Positive Selection with a Single Locus Test Bipartitioning the Coalescent Tree.

Many population genomic studies have been conducted in the past to search for traces of recent events of positive selection. These traces, however, can be obscured by temporal variation of population size or other demographic factors. To reduce the confounding impact of demography, the coalescent tree topology has been used as an additional source of information for detecting recent positive selection in a population or a species. Based on the branching pattern at the root, we partition the hypothetical coalescent tree, inferred from a sequence sample, into two subtrees. The reasoning is that positive selection could impose a strong impact on branch length in one of the two subtrees while demography has the same effect on average on both subtrees. Thus, positive selection should be detectable by comparing statistics calculated for the two subtrees. Simulations demonstrate that the proposed test based on these principles has high power to detect recent positive selection even when DNA polymorphism data from only one locus is available, and that it is robust to the confounding effect of demography. One feature is that all components in the summary statistics ([Formula: see text]) can be computed analytically. Moreover, misinference of derived and ancestral alleles is seen to have only a limited effect on the test, and it therefore avoids a notorious problem when searching for traces of recent positive selection.

Facultative commensalism of a free-burrowing urothoid amphipod with a deep burrow-dwelling callianassid shrimp in intertidal sand

Species of the free-burrowing amphipod genus, Urothoe, are common on open sandy beaches. On intertidal sandflats, some species are associated with burrows or tubes of large infauna. How this link is formed and persisting under sheltered conditions was examined. On an intertidal sandflat in mid-western Kyushu, Japan, U. carda co-occurred with the deep burrow-dwelling callianassid shrimp, Nihonotrypaea harmandi, along a 300-m transect between tide marks. Amphipods resided in the surface 5-cm sediment outside shrimp burrows, as confirmed by sediment coring and burrow casting. In summers 1980 and 1981, the shrimp and amphipod populations were confined to the upper shore at mean densities of 182 and 701 inds m−2, respectively. In winter to spring, when the sediment surface mixing was caused by seasonal wind-induced waves, the amphipod but not the shrimp expanded down to the lowest shore. Later, by 1983, the shrimp increased mean density by 2.5 times and now also ranged to the lowest shore. In the summers of 1984, 2010, and 2015, the amphipod expanded to the lowest shore as well, with small variations in population size. Three marked changes in substrate properties were associated with shrimp inhabitation: thicker oxidized layer (proxy for oxygenated layer) in the sediment column; looser surface sediment, as evaluated with vane shear strength; and coarser and better-sorted surface sediment with less mud content. At least the former two changes were attributable to shrimp bioturbation, which could provide the amphipod with more permeable and softer substrates, leading to the formation of facultative commensalism.

A framework for quantifying the relationship between intensity and severity of impact of disturbance across types of events and species

Understanding the impacts of natural disturbances on wildlife populations is a central task for ecologists; in general, the severity of impact of a disturbance (e.g., the resulting degree of population decline) is likely to depend primarily on the disturbance intensity (i.e., strength of forcing), type of disturbance, and species vulnerability. However, differences among disturbance events in the physical units of forcing and interspecific differences in the temporal variability of population size under normal (non-disturbance) conditions hinder comprehensive analysis of disturbance severity. Here, we propose new measures of disturbance intensity and severity, both represented by the return periods. We use a meta-analysis to describe the severity–intensity relationship across various disturbance types and species. The severity and the range of its 95% confidential interval increased exponentially with increasing intensity. This nonlinear relationship suggests that physically intense events may have a catastrophic impact, but their severity cannot be extrapolated from the severity–intensity relationship for weak, frequent disturbance events. The framework we propose may help to clarify the influence of event types and species traits on the severity–intensity relationship, as well as to improve our ability to predict the ecological consequences of various disturbance events of unexperienced intensity.

Population size and urban health advantage: scaling analyses of four major diseases for 417 US counties

In order to test the validity of urban health penalty versus urban health advantage, we have selected four major non-communicable diseases, cancer, circulatory, respiratory, and endocrine, nutritional and metabolic (ENM), to determine their scaling relationship between death counts and population size for nearly 400 large urban counties in the US during 1999 to 2010. We discover that there is a super-linear scaling relationship for the total counties for each of the four diseases categories, indicating urban health penalty. However, the results from our analysis by the subgroups of counties with different population sizes yield a U-shaped scaling curve where the most pronounced sub-linear relationship occurs at the subgroup of top 40 most populous counties. In short, both super-linear and sub-linear scaling relationships are observed depending on the subgroups with varying population sizes. Incorporating additional control variables do not materially alter our findings.

Population size and urban health advantage: scaling analyses of four major diseases for 417 US counties

In order to test the validity of urban health penalty versus urban health advantage, we have selected four major non-communicable diseases, cancer, circulatory, respiratory, and endocrine, nutritional and metabolic (ENM), to determine their scaling relationship between death counts and population size for nearly 400 large urban counties in the US during 1999 to 2010. We discover that there is a super-linear scaling relationship for the total counties for each of the four diseases categories, indicating urban health penalty. However, the results from our analysis by the subgroups of counties with different population sizes yield a U-shaped scaling curve where the most pronounced sub-linear relationship occurs at the subgroup of top 40 most populous counties. In short, both super-linear and sub-linear scaling relationships are observed depending on the subgroups with varying population sizes. Incorporating additional control variables do not materially alter our findings.

Simulation approach to solve fuzzy fixed charge multi-item solid transportation problems under budget constraint

In this paper, we have developed a dominate-based genetic algorithm to solve fuzzy fixed charge multi-item solid transportation problems (FFCMISTPs) under budget constraint in fuzzy environment, in which sources, demands, capacities of conveyances, unit selling prices, unit purchasing costs, fixed charges, unit transportation costs and transportation times are fuzzy in nature. Here, transportation problems are formulated in the form of profit maximisation problems and solved. For maximisation, a dominate-based genetic algorithm (DBGA) with varying population size, cyclic crossover, two-point mutation is developed which can deal with single-objective transportation problems. The developed algorithm is tested against some test functions and its efficiency is established in terms of iteration numbers for single objective. The fuzzy objective function and constraints are reduced to corresponding deterministic ones using graded mean integrating value, possibility/necessity measures and chance constrained programming method. The reduced crisp problems are solved using developed genetic algorithm. The models are illustrated with numerical examples. The real life practical implication of the model is also presented.

Global stability for a HIV/AIDS model

We investigate global stability properties of a HIV/AIDS population model with constant recruitment rate, mass action incidence, and variable population size. Existence and uniqueness results for disease-free and endemic equilibrium points are proved. Global stability of the equilibria is obtained through Lyapunov's direct method and LaSalle's invariance principle.