Changes In Population Density Research Articles

Some Ecological Aspects on the Striped Mealybug Ferrisia virgata (Cockerell) Infesting Acalypha Shrubs in Qalyubiya Governorate, Egypt

Acalypha shrubs Acalypha wilkesiana Mull.(Euphorbiaceae) found to be favorable host for the striped mealybug Ferrisia virgate (Cockerell)( Pseudococcidae) . This mealybug species is attacked all plant parts and caused considerable damages to this host. Some ecological aspects were carried out on F. virgata infesting acalypha shrubs throughout two successive years (2014-2015) and (2015-2016) in Qalyubiya Governorate. Results obtained showed that population density was more abundant during the second year than the first one, the annual means of total population were 62.02 and 52.01 individuals/leaf), respectively. Also, results revealed that, seasonal abundance of F. virgata found to be active from June to January of next year. The population density was reached its maximum activity on October during both years being 123.0 and 145.2 individuals /leaf for the first and second year, respectively. The prevailing main average temperature and relative humidity were ranging between 22.8°C, 24.2°C and 67%, 64% for the 1st and 2nd years, respectively. These conditions seemed to be favorable conditions for insect activity. After this activity period all stages of this species were disappeared from all plant parts. This phenomenon indicate that this mealybug species was overwinter during winter and spring seasons till the next summer. From these findings it could be stated that any control measurements must be early applied during June, at the beginning of activity period of this mealybug species. Also, results clarified that F. virgate was passed through two annual overlapping field generations on acalypha shrubs. Duration of the first generation was ranged between 80-85 days which occurred during summer months. While the second generation was lasted 75 days and occurred during autumn. Statistical analysis revealed that separate effect of each mean, two weeks earlier of the four selected weather factors on changes in population density of F. virgata most factors had insignificant effects except mean minimum temperature which had positive significant effects throughout the both years (r coefficient values were 0.589 and 0.677). While the combined effects of the four selected factors (mean minimum, maximum temperature, average temperature and mean percentage of relative humidity), two weeks earlier, had significant effects, as a group on the change in population density especially during (2014-2015) , the explained variance was 79.2% and F value 14.4.

DNA methyltransferase 3 participates in behavioral phase change in the migratory locust

DNA methylation plays important roles in the behavioral plasticity of animals. The migratory locust, Locusta migratoria, displays striking density-dependent phenotypic plasticity that can reversely transit between solitarious and gregarious phases. However, the role and the mechanism through which DNA methylation is involved in locust phase change remain unknown. Here, we investigated the expression levels of three DNA methyltransferase genes and their roles in the regulation of locust phase changes. All three Dnmt genes, namely, Dnmt1, Dnmt2 and Dnmt3 showed high expression levels in the brains of gregarious locusts. By contrast, only Dnmt3 transcript rapidly responded to population density changes, decreasing during the isolation of gregarious locusts and steadily increasing upon the crowding of solitarious locusts. Dnmt3 knockdown significantly reduced the phase-related locomotor activity, rather than the attraction index, in gregarious and crowded solitarious locusts. Transcriptome analysis showed that Dnmt3 knockdown upregulated the genes related to metabolism and transporting activity and downregulated those associated with oxidative stress response. The expression level of the phase-core transcriptional factor, hormone receptor HR3, was significantly suppressed in the brain after Dnmt3 knockdown. Moreover, there was significant overlap in the differentially expressed genes between Dnmt3 RNAi and HR3 RNAi data sets, suggesting HR3 may act as key transcriptional factor mediating Dnmt3-controlled gene expression profiles in locust brains. These findings suggest that Dnmt3 transcription is involved in locust behavioral transition, implying the possible roles of DNA methylation in phase-related phenotypic plasticity in locusts.

Recent changes in the Dutch foodscape: socioeconomic and urban-rural differences

BackgroundObesogenic food environments may influence dietary behaviours and contribute to obesity. Few countries quantified changes in their foodscape. We explored how the availability of different types of food retailers has changed in the Netherlands across levels of neighbourhood socioeconomic status (SES) and urbanisation.MethodsThis longitudinal ecological study conducted in the Netherlands had as unit of analysis administrative neighbourhoods. From 2004 to 2018, the geographic location and type of each food retailer were objectively assessed by a commercial company. Food retailers were categorised as local food shops, fast food restaurants, food delivery, restaurants, supermarkets, and convenience stores. Information on neighbourhood SES and urbanisation was obtained from Central Bureau of Statistics (CBS). To test the change in the counts of food retailers we used negative binomial generalized estimating equations (GEE), with neighbourhoods as the group variable, time as the independent variable and the counts of each type of food retailer as outcome. To account for changes in population density, analyses were adjusted for the number of inhabitants per neighbourhood. We tested effect modification by adding an interaction term for neighbourhood SES and urbanisation to the models.ResultsIn Dutch neighbourhoods between 2004 and 2018, a 120 and 35% increase was found in the count of food delivery outlets and restaurants, respectively, and a 24% decrease in count of local food shops. Stratified analyses showed an increase in the availability of supermarkets and convenience stores in the more urbanised and lower SES neighbourhoods, while a decrease was observed in the less urbanised and higher SES neighbourhoods.ConclusionsWe observed considerable changes in the Dutch foodscape. Over a 14 years period, the foodscape changed towards a higher availability of food retailers offering convenience and ready-to-eat foods. These findings can help policy makers aiming to promote a healthier food environment and obesity prevention.

The Impact of Urban Renewal on Land Surface Temperature Changes: A Case Study in the Main City of Guangzhou, China

To improve land use efficiency, urban renewal must also consider urban microclimates and heat islands. Existing research has depended on manual interpretation of high-resolution optical satellite imagery to resolve land surface temperature (LST) changes caused by urban renewal; however, the acquired ground time series data tend to be uneven and unique to specific frameworks. The objective of this study was to establish a more general framework to study LST changes caused by urban renewal using multi-source remote sensing data. Specifically, urban renewal areas during 2007–2017 were obtained by integrating Landsat and yearly Phased Array type L-band Synthetic Aperture Radar (PALSAR) images, and LST was retrieved from Landsat thermal infrared data using the generalized single-channel algorithm. Our results showed that urban renewal land (URL) area accounted for 1.88% of urban land area. Relative LST between URL and general urban land (GUL) of Liwan, Yuexiu, Haizhu, and Tianhe districts dropped by 0.88, 0.42, 0.43, and 0.10 K, respectively, whereas those of Baiyun, Huangpu, Panyu, and Luogang districts presented opposite characteristics, with a rise in the LST of 0.98, 1.03, 1.63, and 2.11 K, respectively. These results are attributable to population density, building density, and landscape pattern changes during the urban renewal process.

Identifying Driving Forces of Built-Up Land Expansion Based on the Geographical Detector: A Case Study of Pearl River Delta Urban Agglomeration.

Understanding the driving forces behind built-up land expansion is crucial in urban planning and management. Using the Pearl River Delta urban agglomeration as research area, four landscape metrics were used to analyze landscape characteristics of urban expansion from 1990 to 2015. Spatial autocorrelation analysis was used to study the characteristics of built-up land expansion, while geographical detector was employed to identify the driving forces of urban land growth and their interactions. The results show the extent of built-up land has been increasing, the structure has become more complex, the level of fragmentation has been increasing, and the aggregation degree is in decline. The built-up landscape index shows spatial heterogeneity occurring in the core and peripheral towns of cities, as well as in the core and peripheral areas of the entire region. Also, changes in the built-up landscape index indicate increased spatial aggregation occurring in the past 25 years. Results from the geographical detector show natural, socio-economic, and transportation-related factors have substantial influence on built-up land expansion. Elevation, slope, population density, change in population density, and road network density were shown to have high influencing power. The influencing powers of slope and change in population density were also found to be different from other factors, highlighting their important role in urban development. Also, there were two types of interactions found, enhance nonlinear and enhance bivariate interactions, indicating the compounding influence of interactions between significant determinants. This study provides a new perspective and methodological approach in evaluating the driving forces behind built-up land expansion and their interactions.

Parallel quorum-sensing system in Vibrio cholerae prevents signal interference inside the host.

Many bacteria use quorum sensing (QS) to regulate virulence factor production in response to changes in population density. QS is mediated through the production, secretion, and detection of signaling molecules called autoinducers (AIs) to modulate population-wide behavioral changes. Four histidine kinases, LuxPQ, CqsS, CqsR and VpsS, have been identified in Vibrio cholerae as QS receptors to activate virulence gene expression at low cell density. Detection of AIs by these receptors leads to virulence gene repression at high cell density. The redundancy among these receptors is puzzling since any one of the four receptors is sufficient to support colonization of V. cholerae in the host small intestine. It is believed that one of the functions of such circuit architecture is to prevent interference on any single QS receptor. However, it is unclear what natural molecules can interfere V. cholerae QS and in what environment interference is detrimental. We show here mutants expressing only CqsR without the other three QS receptors are defective in colonizing the host large intestine. We identified ethanolamine, a common intestinal metabolite that can function as a chemical source of QS interference. Ethanolamine specifically interacts with the ligand-binding CACHE domain of CqsR and induces a premature QS response in V. cholerae mutants expressing only CqsR without the other three QS receptors. The effect of ethanolamine on QS gene expression and host colonization is abolished by mutations that disrupt CqsR signal sensing. V. cholerae defective in producing ethanolamine is still proficient in QS, therefore, ethanolamine functions only as an external cue for CqsR. Our findings suggest the inhibitory effect of ethanolamine on CqsR could be a possible source of QS interference but is masked by the presence of the other parallel QS pathways, allowing V. cholerae to robustly colonize the host.

Influences of eutrophication on methanogenesis pathways and methanogenic microbial community structures in freshwater lakes

Freshwater lakes, especially eutrophic ones, have become a hotspot of methanogenesis. However, the effects of eutrophication and seasonality on methanogenesis activity and methanogenic microbial community remain unclear. In the current study, for two adjacent lakes at different trophic status, their methanogenesis potential in different seasons was evaluated using incubation experiments. The density, diversity, and community structure of methanogens were analyzed based on the mcrA gene. Correlation analysis and redundancy analysis were carried out to identify the environmental factors driving the variations of methanogenesis potential and methanogen community. The results showed that eutrophication could result in active methanogenesis with relatively high seasonal variance. The methanogenesis variation could be well explained by carbon input in association with algal growth, as well as the change of methanogen population density. With the dominance of Methanomicrobiales in both lakes, the hydrogenotrophic pathway had a major contribution to total methane production. The considerable proportion of Methanomassiliicocales in eutrophic lake implied that methylotrophic methanogenesis might be previously underestimated. These results added new insights towards methanogenesis process in eutrophic freshwater lakes.

What Happened to Brussels? The Big Decline and Muslim Immigration

We examined regional inequality in Belgium, both in the 19 communes of Brussels and in the country as a whole (n = 589 communes). We find very strong relationships between Muslim% of the population and a variety of social outcomes such as crime rate, educational attainment, and median income. For the 19 communes of Brussels, we find a correlation of -.94 between Muslim% and a general factor of socioeconomic variables (S factor) based on 22 diverse indicators. The slope for this relationship is -7.52, meaning that a change in S going from 0% to 100% Muslim corresponds to a worsening of overall social well-being by 7.52 (commune-level) standard deviations. For the entire country, we have data for 8 measures of social inequality. Analysis of the indicators shows an S factor which is very similar to the one from the Brussels data only based on the full set of indicators (r’s = .98). In the full dataset, the correlation between S and Muslim% is -.52, with a slope of -8.05. Adding covariates for age, population density, and spatial autocorrelation changes this slope to -8.77. Thus, the expected change going from a 0% to 100% Muslim population is -8.77 standard deviations in general social well-being. We discuss our findings in relation to other research on immigration and social inequality, with a focus on the causal influence of intelligence on life outcomes in general.

The Prediction of Finely-Grained Spatiotemporal Relative Human Population Density Distributions in China

China’s transportation industry has been experiencing huge changes and the travelling frequency of citizens becomes higher and higher and more and more diversified in a short time period. The analysis and deep research on the short-term change of population density in the city-level spatial resolution are worthy of further exploration. In this study, we first used two linear regression models to build relationships between the 2010 census density, predicted 2020 census density and the Tencent density respectively to test the usability of Tencent positioning data. The Pearson’s correlation coefficients r 0.58 (p $50\times 50$ km of spatial resolution. The total average of the ConvLSTM model’s Root Mean Square Error (RMSE) is 139.0, while the SARIMA’s one is three times greater than the value. And the coefficient of determination (R2) values of ConvLSTM model is higher than 0.9, while the other ones are about 0.78. Comparing the two results in both time and space concludes that: the evaluation results reflected by RMSE and R2 showed that the two models are both suitable for the prediction of Tencent density distribution in finely-grained time and space. Nevertheless, the predicted density correlated much better with the tested data at temporal and spatial scales when using ConvLSTM compared to SARIMA, and the capability of prediction in space by ConvLSTM model is more stable.

Population Density and Urbanization: Global Research Trend Analysis through the Lens of Scopus and Web of Science

In the last few decades, the steep rise in India’s urban population has caused rapid changes in population pattern. The main reason for this change is migration from rural to urban areas. Due to land crisis, cities like Mumbai and Kolkata are experiencing vertical growth, which causes change in population density. The ongoing process of urbanization impacts environmental, demographic, and socioeconomic heterogeneity issues. The municipal areas of cities should have basic amenities like electricity, roads, drinking water, communication, health and access to education. Here lies the question of urban planning. This paper has three distinct objectives. It aims to examine: (a) The genesis and growth of global research on urbanization and population density as reflected in two major citation databases, viz. Scopus and Web of Science; (b) The different facets of urbanization and population density research, through the two citation databases. (c) The essential bibliographic components like authorship pattern, source distribution pattern, keyword distribution pattern etc. of research output.

Association of change in the neighborhood obesogenic environment with colorectal cancer risk: The Multiethnic Cohort Study.

BackgroundNeighborhood environment has been associated with health behaviors. Despite the evidence of the influence of neighborhood social and physical factors on cancer risk, no research has evaluated whether changes in the neighborhood obesogenic environment, either by physical moves to different neighborhoods or experiencing neighborhood redevelopment or neglect, affect cancer risk.MethodsThe association of change in neighborhood environment attributes (socioeconomic status, population density, restaurant and retail food environments, numbers of recreational facilities and businesses, commute patterns, traffic density, and street connectivity) with colorectal cancer (CRC) risk was examined among 95,472 Los Angeles, CA, Multiethnic Cohort participants, including 2295 invasive CRC cases diagnosed between 1993 and 2010 using Cox proportional hazards regression, adjusting for age, race/ethnicity, other risk factors including BMI and physical activity, and baseline levels of neighborhood attributes. Stratified analyses were conducted by racial/ethnic group and moving status.Results40% of participants moved (changed physical residence) during follow-up. Across all races/ethnicities, upward change in population density was statistically significantly associated with higher CRC risk among male and female non-movers (HR: 1.35 and 1.41, respectively). The same association was also observed separately among female African American and Japanese American non-movers, male Latino non-movers, female African American and male White movers. Downward change in population density was significantly related to higher CRC risk among female non-movers (HR: 1.33). Downward change in traffic density was associated with lower CRC risk among male non-movers but with higher CRC risk among female movers (HR: 0.66 and 1.43, respectively). Downward changes in street connectivity or the number of recreational facilities were associated with higher CRC risk (HR: 1.34 and 1.54, respectively). Upward change in the number of recreational facilities was associated with lower CRC risk among female non-movers (HR: 0.70). Changes in the other neighborhood attributes did not exhibit significant associations with CRC risk within more than one racial/ethnic group.ConclusionChanges over time in neighborhood attributes have an effect on the risk of colorectal cancer, which is separate from the baseline levels of the same attributes and individual-level risk factors, and differs between sexes, movers and non-movers and across racial/ethnic groups.

Density dependence on multiple spatial scales maintains spatial variation in both abundance and traits

Population density affects fitness through various processes, such as mate finding and competition. The fitness of individuals in a population can in turn affect its density, making population density a key quantity linking ecological and evolutionary processes. Density effects are, however, rarely homogeneous. Different life-history processes can be affected by density over different spatial scales. In birds, for example, competition for food may depend on the number of birds nesting in the direct vicinity, while competition for nesting sites may occur over larger areas. Here we investigate how the effects of local density and of density in a nearby patch can jointly affect the emergence of spatial variation in abundance as well as phenotypic diversification. We study a two-patch model that is described by coupled ordinary differential equations. The patches have no intrinsic differences: they both have the same fitness function that describes how an individual’s fitness depends on density in its own patch as well as the density in the other patch. We use a phase-space analysis, combined with a mathematical stability analysis to study the long-term behaviour of the system. Our results reveal that the mutual effect that the patches have on each other can lead to the emergence and long-term maintenance of a low and a high density patch. We then add traits and mutations to the model and show that different selection pressures in the high and low density patch can lead to diversification between these patches. Via eco-evolutionary feedbacks, this diversification can in turn lead to changes in the long-term population densities: under some parameter settings, both patches reach the same equilibrium density when mutations are absent, but different equilibrium densities when mutations are allowed. We thus show how, even in the absence of differences between patches, interactions between them can lead to differences in long-term population density, and potentially to trait diversification.

Demographic and spatial responses of resident bird populations to the arrival of migratory birds within an urban environment

AbstractLong‐distance migration allows many bird species to overcome the severe climatic changes that occur in seasonal environments. Migration is highly demanding, and given its cyclical nature, we currently know that it has substantial effects on the population parameters of migratory birds during both breeding and wintering seasons. However, the potential effects of the presence of migratory birds in their wintering grounds on populations of resident birds have remain largely unexplored. Here, we propose the hypothesis that migratory birds negatively affect the habitat occupancy and population abundance of resident birds because of the arrival of numerous individuals during the most limiting months of the year. Here, we studied different species of migratory and resident birds that coexist during winter in an urban ecological reserve located within Mexico City. We used single‐species multiseason occupancy models, two‐species occupancy models, and distance sampling techniques to evaluate changes in occupancy and population density of resident bird species during three consecutive winters. We found an aggregation pattern between two resident species (Psaltriparus minimusandThryomanes bewickii) with three migratory warblers (Cardellina pusilla,Setophaga coronataandSetophaga townsendi). Thus, our results provide evidence of the formation of mixed‐species flocks in our study area. We also conclude that resident birds experience different demographic and behavioral processes during winter that not necessarily result from interspecific interactions with migratory birds.

Global H-NS counter-silencing by LuxR activates quorum sensing gene expression.

Bacteria coordinate cellular behaviors using a cell–cell communication system termed quorum sensing. In Vibrio harveyi, the master quorum sensing transcription factor LuxR directly regulates >100 genes in response to changes in population density. Here, we show that LuxR derepresses quorum sensing loci by competing with H-NS, a global transcriptional repressor that oligomerizes on DNA to form filaments and bridges. We first identified H-NS as a repressor of bioluminescence gene expression, for which LuxR is a required activator. In an hns deletion strain, LuxR is no longer necessary for transcription activation of the bioluminescence genes, suggesting that the primary role of LuxR is to displace H-NS to derepress gene expression. Using RNA-seq and ChIP-seq, we determined that H-NS and LuxR co-regulate and co-occupy 28 promoters driving expression of 63 genes across the genome. ChIP-PCR assays show that as autoinducer concentration increases, LuxR protein accumulates at co-occupied promoters while H-NS protein disperses. LuxR is sufficient to evict H-NS from promoter DNA in vitro, which is dependent on LuxR DNA binding activity. From these findings, we propose a model in which LuxR serves as a counter-silencer at H-NS-repressed quorum sensing loci by disrupting H-NS nucleoprotein complexes that block transcription.

Responses of daphnids and other zooplankton populations to massive fish kill in Lake Suwa

AbstractIn 2016, a massive fish kill of the planktivorous pond smelt Hypomesus nipponensis occurred in Lake Suwa, Japan. Pond smelt, which is important fish species from commercial and cultural perspectives, influences the zooplankton community in the lake. Following the massive fish kill, Daphnia galeata appeared and their population density increased to previously unseen levels by summer 2017. To help recover the fish population, larval pond smelt were released into the lake. Consequently, D. galeata has rarely appeared in Lake Suwa since summer 2017, except for a low‐density population observed in May–June 2018. These phenomena indicated that fish predation is a possible primary factor for suppressing daphnid populations in shallow eutrophic lake. Zooplankton populations showed species‐specific responses to the alterations in predation pressure. When the D. galeata population peaked after the fish kill event, rotifers, which are small‐sized competitors of daphnids, and calanoids tended to decrease in density. Rotifers then increased with the decrease in the daphnid populations due to the recovery of fish. Alternatively, cyclopoids, which demonstrated a similar population density following the fish kill event, tended to decrease when the fish population recovered. The population densities of Leptodora cf. kindtii/richardi and Bosmina spp. did not significantly differ between before the massive kill event and after pond smelt recovery. It is believed that the changes in zooplankton population densities observed in the present study may provide insights for further monitoring of aquatic food webs in eutrophic water systems, including Lake Suwa, where re‐oligotrophication is occurring and biological interactions are changing.

Impact of climate change on the small mammal community of the Yukon boreal forest.

Long‐term monitoring is critical to determine the stability and sustainability of wildlife populations, and if change has occurred, why. We have followed population density changes in the small mammal community in the boreal forest of the southern Yukon for 46 years with density estimates by live trapping on 3–5 unmanipulated grids in spring and autumn. This community consists of 10 species and was responsible for 9% of the energy flow in the herbivore component of this ecosystem from 1986 to 1996, but this increased to 38% from 2003 to 2014. Small mammals, although small in size, are large in the transfer of energy from plants to predators and decomposers. Four species form the bulk of the biomass. There was a shift in the dominant species from the 1970s to the 2000s, with Myodes rutilus increasing in relative abundance by 22% and Peromyscus maniculatus decreasing by 22%. From 2007 to 2018, Myodes comprised 63% of the catch, Peromyscus 20%, and Microtus species 17%. Possible causes of these changes involve climate change, which is increasing primary production in this boreal forest, and an associated increase in the abundance of 3 rodent predators, marten (Martes americana), ermine (Mustela ermine) and coyotes (Canis latrans). Following and understanding these and potential future changes will require long‐term monitoring studies on a large scale to measure metapopulation dynamics. The small mammal community in northern Canada is being affected by climate change and cannot remain stable. Changes will be critically dependent on food–web interactions that are species‐specific.

Quantifying cryptic function loss during community disassembly

Abstract Emerging theory suggests that the ecosystem‐level consequences of anthropogenic pressures depend on how species will be disassembled from ecological communities (i.e. the disassembly rule). Species loss, however, is not the sole ecological cause of ecosystem function loss: behaviours underpinning ecosystem function can also be disrupted by anthropogenic pressures without detectable declines of component species (‘cryptic function loss’). Here, we introduce a novel framework that integrates behavioural responses into community disassembly metrics. We applied this framework to freshwater mussel communities (order Unionida) of the midwestern United States, in which intensive agricultural land use threatens stream biota. We combined a field experiment, meta‐analysis and watershed‐scale population dataset to assess how excessive sediment concentrations, one of the leading drivers of freshwater biodiversity loss, influence community‐level water clearance rates of freshwater mussels via behavioural (changes in mass‐specific clearance rate) and population (changes in population density) responses. Our study provided three key insights. First, freshwater mussels exhibited high behavioural sensitivity to increased total suspended solids (TSS) across species (i.e. reduced water clearance rate), whereas population responses were highly species‐specific. Second, the behavioural response to increased TSS causes substantial cryptic function loss under stressful conditions: simulated water clearance rates when behavioural response is included can be less than half that of mussel communities with no behavioural response. Finally, simulations revealed that mussel communities are likely to show rapid but consistent rates of ecosystem function loss irrespective of disassembly rules. The similar rates of function loss are due to the uniform behavioural response to TSS that masks the linkage between population sensitivity of a species and its contribution to ecosystem function. Synthesis and applications. Our findings suggest that ignoring behavioural processes may cause non‐negligible underestimation of ecosystem function loss during community disassembly, potentially leading to overly optimistic assessments of ecosystem resilience. Furthermore, unlike species declines or local extinctions, behaviour response tied to function loss may occur concurrently with increasing anthropogenic pressures. Therefore, managers should acknowledge the risk of immediate function loss after human‐induced environmental changes.

Historical (1700–2012) global multi-model estimates of the fire emissions from the Fire Modeling Intercomparison Project (FireMIP)

Abstract. Fire emissions are a critical component of carbon and nutrient cycles and strongly affect climate and air quality. Dynamic global vegetation models (DGVMs) with interactive fire modeling provide important estimates for long-term and large-scale changes in fire emissions. Here we present the first multi-model estimates of global gridded historical fire emissions for 1700–2012, including carbon and 33 species of trace gases and aerosols. The dataset is based on simulations of nine DGVMs with different state-of-the-art global fire models that participated in the Fire Modeling Intercomparison Project (FireMIP), using the same and standardized protocols and forcing data, and the most up-to-date fire emission factor table based on field and laboratory studies in various land cover types. We evaluate the simulations of present-day fire emissions by comparing them with satellite-based products. The evaluation results show that most DGVMs simulate present-day global fire emission totals within the range of satellite-based products. They can capture the high emissions over the tropical savannas and low emissions over the arid and sparsely vegetated regions, and the main features of seasonality. However, most models fail to simulate the interannual variability, partly due to a lack of modeling peat fires and tropical deforestation fires. Before the 1850s, all models show only a weak trend in global fire emissions, which is consistent with the multi-source merged historical reconstructions used as input data for CMIP6. On the other hand, the trends are quite different among DGVMs for the 20th century, with some models showing an increase and others a decrease in fire emissions, mainly as a result of the discrepancy in their simulated responses to human population density change and land use and land cover change (LULCC). Our study provides an important dataset for further development of regional and global multi-source merged historical reconstructions, analyses of the historical changes in fire emissions and their uncertainties, and quantification of the role of fire emissions in the Earth system. It also highlights the importance of accurately modeling the responses of fire emissions to LULCC and population density change in reducing uncertainties in historical reconstructions of fire emissions and providing more reliable future projections.

Insights Into Nitric Oxide Modulated Quorum Sensing Pathways.

The emerging threat of drug resistant bacteria has prompted the investigation into bacterial signaling pathways responsible for pathogenesis. One such mechanism by which bacteria regulate their physiology during infection of a host is through a process known as quorum sensing (QS). Bacteria use QS to regulate community-wide gene expression in response to changes in population density. In order to sense these changes in population density, bacteria produce, secrete and detect small molecules called autoinducers. The most common signals detected by Gram-negative and Gram-positive bacteria are acylated homoserine lactones and autoinducing peptides (AIPs), respectively. However, increasing evidence has supported a role for the small molecule nitric oxide (NO) in influencing QS-mediated group behaviors like bioluminescence, biofilm production, and virulence. In this review, we discuss three bacteria that have an established role for NO in influencing bacterial physiology through QS circuits. In two Vibrio species, NO has been shown to affect QS pathways upon coordination of hemoprotein sensors. Further, NO has been demonstrated to serve a protective role against staphylococcal pneumonia through S-nitrosylation of a QS regulator of virulence.

Histomorphometric age estimation from the femoral cortex: A test of three methods in an Australian population

Histological methods can be used forensically to estimate age-at-death based on patterns of change in osteon shape, size, and population density, all of which result from the continuous process of bone remodelling. The present study examines the applicability of three existing histological age-at-death estimation methods as applied to an Australian population of known age and sex. Microradiographs from 50 mid-shaft femora thin sections, equally divided by sex, were obtained from the Melbourne Femur Reference Collection (MFRC); stated chronological age-at-death is 18 to 88 years. Osteon shape metrics are measured using ImageJ and the age-at-death prediction formulae of i) Singh and Gunberg, ii) Keough et al., and iii) Goliath et al. are applied. The relationship between estimated and actual age-at-death is then statistically quantified. All three formulae demonstrate pooled and sex-specific SEE values in excess of 20 years: i) pooled ±22.92 (♂±20.91, ♀±25.20); ii) ±20.79 (♂±20.96, ♀±21.05); and iii) ±35.43 (♂±32.68, ♀±38.66). When individuals under 40 years of age were excluded from the analysis, only two of the methods demonstrated increased accuracy: i) pooled ±20.87 (♂ ±17.47, ♀ ±23.70); ii) pooled ±18.21 (♂±16.51, ♀±19.90); and iii) pooled ±41.18 (♂ ±40.12, ♀ 43.05). The present study represents a preliminary investigation of the accuracy of existing histological age-at-death standards applied in an Australian population of known age.