Differences In Population Size Research Articles

Exploration of Fragmentation Mechanisms of Yellow Split Peas during Grinding Using a Multimodal Approach

In the context of food and agro-ecological transitions, the development of food applications based on legume flours and plant proteins requires a mastery of grain milling. While wheat grain milling has been extensively studied and is well-mastered, legume grinding and its underlying mechanisms are still poorly understood. The aim of this work is to contribute to the study of the fragmentation mechanisms of pea grains during grinding. Experiments were carried out on hulled yellow pea grains (Kameleon variety) ground under different conditions using a ball mill (MM400, Retsch®, Haan, Germany) or a micro-cylinder mill. The results showed that the grinding of pea grains, regardless of the type of mill, produced powders characterized by particle size distribution curves with a multimodal shape. The curve analysis was performed according to a simplified deconvolution approach, taking into account different particle populations without diameter overlap. Four particle populations of different sizes were identified and correlated with specific mechanisms governing the grinding of yellow split peas. The physical and biochemical properties of the resulting powders were determined. Taking into account the proportions of the four populations within the powders, the results showed a positive correlation between the volume proportions of very fine (0–10 µm) and fine (10–55 µm) particles within the powders and the starch damage rate and the specific surface area developed, irrespective of the type of mill.

Mathematical modeling of the vaccination influence on the COVID-19 epidemic propagation

The mathematical model based on a system of ordinary differential equations is proposed to describe the effect of the vaccination rate on the spread of the COVID-19 epidemic. The results of numerical modeling are presented for the case when vaccination begins after the beginning of the epidemic. A dimensionless vaccination parameter V was obtained, which allows one to characterize the effect of the vaccination rate on the reduction of the incidence of viral diseases with different virulence levels in a large closed population of people. Introducing this parameter allows the simulation results to be generalized to the populations of different size, different epidemic spread rate, different vaccination rate, and different vaccine efficiency. It has been shown that increasing the parameter V decreases the proportion of the sick population. It follows from our model that the vaccination influence on the spread of a respiratory viral disease such as COVID-19 decreases for a later initiation of vaccination. The simulation results should contribute to the development of optimal vaccination scenarios for the population.

The role of population size in folk tune complexity

Demography, particularly population size, plays a key role in cultural complexity. However, the relationship between population size and complexity appears to vary across domains: while studies of technology typically find a positive correlation, the opposite is true for language, and the role of population size in complexity in the arts remains to be established. Here, we investigate the relationship between population size and complexity in music using Irish folk session tunes as a case study. Using analyses of a large online folk tune dataset, we show that popular tunes played by larger communities of musicians have diversified into a greater number of different versions which encompass more variation in melodic complexity compared with less popular tunes. However, popular tunes also tend to be intermediate in melodic complexity and variation in complexity for popular tunes is lower than expected given the increased number of tune versions. We also find that user preferences for individual tune versions are more skewed in popular tunes. Taken together, these results suggest that while larger populations create more frequent opportunities for musical innovation, they encourage convergence upon intermediate levels of melodic complexity due to a widespread inverse U-shaped relationship between complexity and aesthetic preference. We explore the assumptions underlying our empirical analyses further using simple simulations of tune diffusion through populations of different sizes, finding that a combination of biased copying and structured populations appears most consistent with our results. Our study demonstrates a unique relationship between population size and cultural complexity in the arts, confirming that the relationship between population size and cultural complexity is domain-dependent, rather than universal.

Mass determination of protoplanetary disks from dust evolution

Context. The mass of protoplanetary disks is arguably one of their most important quantities shaping their evolution toward planetary systems, but it remains a challenge to determine this quantity. Using the high spatial resolution now available on telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA), recent studies derived a relation between the disk surface density and the location of the “dust lines”. This is a new concept in the field, linking the disk size at different continuum wavelengths with the radial distribution of grain populations of different sizes. Aims. We aim to use a dust evolution model to test the dependence of the dust line location on disk gas mass. In particular, we are interested in the reliability of the method for disks showing radial substructures, as recent high-resolution observations revealed. Methods. We performed dust evolution calculations, which included perturbations to the gas surface density with different amplitudes at different radii, to investigate their effect on the global drift timescale of dust grains. These models were then used to calibrate the relation between the dust grain drift timescale and the disk gas mass. We investigated under which condition the dust line location is a good mass estimator and tested how different stellar and disk properties (disk mass, stellar mass, disk age, and dust-to-gas ratio) affect the dust line properties. Finally, we show the applicability of this method to disks such as TW Hya and AS 209 that have been observed at high angular resolution with ALMA and show pronounced disk structures. Results. Our models without pressure bumps confirm a strong dependence of the dust line location on the disk gas mass and its applicability as a reliable mass estimator. The other disk properties do not significantly affect the dust line location, except for the age of the system, which is the major source of uncertainty for this mass estimator. A population of synthetic disks was used to calibrate an analytic relation between the dust line location and the disk mass for smooth disks, finding that previous mass estimates based on dust lines overestimate disk masses by about one order of magnitude. Radial pressure bumps can alter the location of the dust line by up to ~10 au, while its location is mainly determined by the disk mass. Therefore, an accurate mass estimation requires a proper evaluation of the effect of bumps. However, when radial substructures act as traps for dust grains, the relation between the dust line location and disk mass becomes weaker, and other mass estimators need to be adopted. Conclusions. Our models show that the determination of the dust line location is a promising approach to the mass estimate of protoplanetay disks, but the exact relation between the dust line location and disk mass depends on the structure of the particular disk. We calibrated the relation for disks without evidence of radial structures, while for more complex structures we ran a simple dust evolution model. However, this method fails when there is evidence of strong dust traps. It is possible to reveal when dust evolution is dominated by traps, providing the necessary information for when the method should be applied with caution.

Correlation between adiponectin level and the degree of fibrosis in patients with NAFLD

Abstract Background Non-alcoholic Fatty Liver Disease (NAFLD) is one of the most prevalent chronic liver diseases particularly in Egypt. It is defined as accumulation of lipids inside the hepatocytes, in absence of other etiologies of hepatic damage. It is frequently associated with obesity, diabetes mellitus and metabolic syndrome. Objective To find out the correlation between the degree of liver fibrosis in Non-alcoholic Fatty Liver Disease patients and their serum Adiponectin level as a future non-invasive method for assessment of liver fibrosis to substitute liver biopsy to avoid its hazardous complication. Also to study the correlation between diabetes mellitus as well as obesity and serum Adiponetctin level. Patients and Methods 50 patients were selected to participate in our study based on our inclusion criteria. They were recruited from the Internal Medicine department, Gastro-intestinal clinic in AlDemerdash Hospital using a convenient sampling method. Diagnoses of NAFLD (Non-alcoholic fatty liver disease) was confirmed by laboratory markers (AST, ALT, Lipid profile), ultrasound as well as fibroscan examination. Results Analyzing adiponectin levels showed that -besides its significant correlation with BMI, hypertension, diabetes mellitus and dyslipidemia- it was significantly lower in high grade fibrosis group compared to low grade fibrosis group with P-value of (0.000) and a cutoff value for stage 3/4 fibrosis of about 2.31μg/ml which marked a promising hope of adeponictin being of protective value against liver fibrosis. However, more studies performed on populations of different sizes and characteristics are recommended to allow more accurate generalization of the results and hopefully exploring a new horizon for the follow up and treatment of patients with chronic liver disease especially NAFLD. Conclusion Adiponectin is an abundant adipocyte-derived protein with well-established antiatherogenic, insulin-sensitizing and anti-inflammatory properties. The liver is a major target organ for adiponectin especially in fatty liver diseases and this adipocytokine has the ability to control many liver functions including metabolism, inflammation and fibrosis. Both serum levels and hepatic adiponectin receptor expression are decreased in NAFLD. Therefore, either adiponectin itself or adiponectin-inducing agents might be of key therapeutic interest in the near future in the treatment of NAFLD.

Applying deterministic lateral displacement cell separation on immune cells of Marine shrimp

For analyzing the immune system of an organism, it is necessary to classify and separate distinct types of cells based on their characteristics. Hemocytes, immune cells of shrimp, are still difficult to classify and separate with existing technologies due to the lack of obvious morphological characteristics or type-specific markers. We adapted the deterministic lateral displacement (DLD) method as a tool to separate the hemocytes of shrimp because the previous work suggested there is a relevance between the size of hemocytes and their functions. The image and flow cytometry (FCM) analyses confirmed that this microfluidics-based technology enabled the size-based separation of cells having a broad size distribution at the buffer condition suitable for the marine species. Cells separated with this chip retained their morphological information, and qRT-PCR was successfully conducted to reveal the differences in expression levels of immune-related genes between cell populations of different sizes. The present results prove that the DLD method can be an effective tool for the analysis of non-model organisms, in which the characteristics of cells are not well established and studied.

Cell heterogeneity, rather than the cell storage solution, affects the behavior of mesenchymal stem cells in vitro and in vivo

BackgroundMesenchymal stem cells (MSCs) have to be expanded in vitro to reach a sufficient cell dose for the treatment of various diseases. During the process of expansion, some obstacles remain to be overcome. The purpose of this study was to investigate the effects of storage solutions and heterogeneity on the behavior of MSCs in vitro and in vivo.MethodsUmbilical cord MSCs (UC-MSCs) of similar sizes within normal ranges were suspended in three different storage solutions, phosphate buffer solution, normal saline, and Dulbecco’s modified Eagle medium. Then, the ultrastructure, viability, and safety of these cells were compared. Other two UC-MSC populations of different sizes were categorized based on their mean diameters. The ultrastructure, proliferation, immunosuppression, hepatic differentiation potential, and number of senescent cells were investigated and compared. The survival rates of mice after the infusion of UC-MSCs of different sizes were compared.ResultsFor UC-MSCs suspended in different storage solutions, the cell apoptosis rates, ultrastructure, and survival rates of mice were similar, and no differences were observed. Cells with a diameter of 19.14 ± 4.89 μm were categorized as the larger UC-MSC population, and cells with a diameter of 15.58 ± 3.81 μm were categorized as the smaller population. The mean diameter of the larger UC-MSC population was significantly larger than that of the smaller UC-MSC population (p < 0.01). Smaller UC-MSCs had more powerful proliferation and immunosuppressive potential and a higher nucleus-cytoplasm ratio than those of large UC-MSCs. The number of cells positive for β-galactosidase staining was higher in the larger UC-MSC population than in the smaller UC-MSC population. The survival rates of mice receiving 1 × 106 or 2 × 106 smaller UC-MSCs were 100%, both of which were higher than those of mice receiving the same amounts of larger UC-MSCs (p < 0.01). The cause of mouse death was explored and it was found that some larger UC-MSCs accumulated in the pulmonary capillary in dead mice.ConclusionDifferent storage solutions showed no significant effects on cell behavior, whereas heterogeneity was quite prevalent in MSC populations and might limit cells application. Hence, it is necessary to establish a more precise standardization for culture-expanded MSCs.

Ex Situ Conservation of Large and Small Plant Populations Illustrates Limitations of Common Conservation Metrics

Premise of research. Ex situ plant conservation can be improved through genetic analysis. One area of interest is the relative value of conserving smaller or larger populations and how sampling strategies for these might differ. Current practice emphasizes collecting large sample sizes from some populations and limiting sampling from others and aims for the capture of allele diversity exceeding predetermined thresholds at the species level. Evaluating how well botanic garden collections can capture the genetic diversity of populations of different sizes can help refine guidance on conservation efforts. Methodology. A model species, Pseudophoenix sargentii (Arecaceae), was chosen for its disjunct and insular range, variation in population size, and presence in collections. We compared 123 in situ plants from three discrete island populations with 94 ex situ conservation specimens via 10 microsatellite markers. Comparison of allelic diversity among the wild populations and collections allowed for the evaluation of genetic capture. Pivotal results. Genetic distance analysis, fixation indexes, and Bayesian clustering analysis show discrete in situ geographic structure and close affinity between ex situ collections and in situ source populations. Yet collections from just the largest population met the Global Strategy for Plant Conservation Target 9 threshold for conservation success for that source population, for other smaller populations, and for all populations together. Conclusions. Percent of genetic capture thresholds may need revision, as such thresholds overlook important diversity. Efficient genetic capture is maximized by emphasizing unique maternal lineages and limiting half-siblings in a collection, but this selectivity must be balanced against the need for redundancy in living collections. Large and small populations each contribute to meeting genetic diversity goals. We recommend that botanic gardens and their networks develop conservation priorities based on genetic diversity and resources, carefully consider existing thresholds for conservation success, define metrics for ex situ conservation goals, and integrate analysis into ex situ conservation efforts.

A Framework for a Statistical Characterization of Epidemic Cycles: COVID-19 Case Study.

BackgroundSince the beginning of the COVID-19 pandemic, researchers and health authorities have sought to identify the different parameters that drive its local transmission cycles to make better decisions regarding prevention and control measures. Different modeling approaches have been proposed in an attempt to predict the behavior of these local cycles.ObjectiveThis paper presents a framework to characterize the different variables that drive the local, or epidemic, cycles of the COVID-19 pandemic, in order to provide a set of relatively simple, yet efficient, statistical tools to be used by local health authorities to support decision making.MethodsVirtually closed cycles were compared to cycles in progress from different locations that present similar patterns in the figures that describe them. With the aim to compare populations of different sizes at different periods of time and locations, the cycles were normalized, allowing an analysis based on the core behavior of the numerical series. A model for the reproduction number was derived from the experimental data, and its performance was presented, including the effect of subnotification (ie, underreporting). A variation of the logistic model was used together with an innovative inventory model to calculate the actual number of infected persons, analyze the incubation period, and determine the actual onset of local epidemic cycles.ResultsThe similarities among cycles were demonstrated. A pattern between the cycles studied, which took on a triangular shape, was identified and used to make predictions about the duration of future cycles. Analyses on effective reproduction number (Rt) and subnotification effects for Germany, Italy, and Sweden were presented to show the performance of the framework introduced here. After comparing data from the three countries, it was possible to determine the probable dates of the actual onset of the epidemic cycles for each country, the typical duration of the incubation period for the disease, and the total number of infected persons during each cycle. In general terms, a probable average incubation time of 5 days was found, and the method used here was able to estimate the end of the cycles up to 34 days in advance, while demonstrating that the impact of the subnotification level (ie, error) on the effective reproduction number was <5%.ConclusionsIt was demonstrated that, with relatively simple mathematical tools, it is possible to obtain a reliable understanding of the behavior of COVID-19 local epidemic cycles, by introducing an integrated framework for identifying cycle patterns and calculating the variables that drive it, namely: the Rt, the subnotification effects on estimations, the most probable actual cycles start dates, the total number of infected, and the most likely incubation period for SARS-CoV-2.

Influence of stream characteristics and population size on downstream transport of freshwater mollusk environmental DNA

Many freshwater mussel species are highly endangered. Knowledge of their occurrence and distribution is a crucial prerequisite for their conservation. The use of environmental DNA (eDNA) is a relatively new approach and an effective tool to detect the presence of target species in freshwater environments. This study aimed to establish a molecular identification tool for eDNA for the endangered thick-shelled river mussel Unio crassus Philipsson in Retzius, 1788 and to analyze the relationships between mussel abundance, stream discharge, sampling distance, and freshwater mollusk DNA signal (detectability and DNA quantity) by using binary logistic and linear regression modeling. We additionally correlated turbidity and mollusk DNA detectability. We developed a species-specific eDNA detection system in silico and tested the efficiency and species specificity on water samples collected downstream of extant populations of different sizes (100–42,000 individuals) in Bavaria, Germany. This system allowed detection of very small U. crassus populations over long distances (>3 km) and excluded amplification of DNA from other potentially co-occurring species. Signal strength was most strongly associated with population size and distance of sampling point from mussel population. Additionally, a negative correlation with stream turbidity was evident. This species-specific tool may help in screening of streams for target species that are otherwise difficult to monitor.

Conserving the genetic diversity of condemned populations: Optimizing collections and translocation.

We consider approaches for conserving genetic diversity from plant populations whose destruction is imminent. We do this using SNP genotype data from two endangered species, Pimelea spicata and Eucalyptus sp. Cattai. For both species, we genotyped plants from a ‘condemned’ population and designed ex situ collections, characterizing how the size and composition of the collection affected the genetic diversity preserved. Consistent with previous observations, populations where genetic diversity was optimized captured more alleles than populations of equal size chosen at random. This benefit of optimization was larger when the propagation population was small. That is, small numbers of individuals (e.g. 20) needed to be selected carefully to capture a comparable proportion of alleles to optimized populations, but larger random populations (e.g. >48) captured almost as many alleles as optimized populations. We then examined strategies for generating translocation populations based on the horticultural constraints presented by each species. In P. spicata, which is readily grown from cuttings, we designed translocation populations of different sizes, using different numbers of ramets from each member of propagation populations. We then performed simulations to predict the loss of alleles from these populations over 10 generations. Large translocation populations were predicted to maintain a greater proportion of source population alleles than smaller translocation populations, but this effect was saturated beyond 200 individuals. In E. sp. Cattai, we examined strategies to promote the diversity of progeny from a conservation planting scenario with 36 individuals. This included the optimization of the spatial arrangement of the planting and supplementing the diversity of the condemned population with individuals from additional sites. In sum, we studied approaches for designing genetically diverse translocations of condemned populations for two species that require contrasting methods of propagation, illustrating the application of approaches that were useful in different circumstances.

Effect of O-Antigen Chain Length Regulation on the Immunogenicity of Shigella and Salmonella Generalized Modules for Membrane Antigens (GMMA).

Recently, generalized modules for membrane antigens (GMMA) technology has been proposed as an alternative approach to traditional glycoconjugate vaccines for O-antigen delivery. Saccharide length is a well-known parameter that can impact the immune response induced by glycoconjugates both in terms of magnitude and quality. However, the criticality of O-antigen length on the immune response induced by GMMA-based vaccines has not been fully elucidated. Here, Shigella and Salmonella GMMA-producing strains were further mutated in order to display homogeneous polysaccharide populations of different sizes on a GMMA surface. Resulting GMMA were compared in mice immunization studies. Athymic nude mice were also used to investigate the involvement of T-cells in the immune response elicited. In contrast with what has been reported for traditional glycoconjugate vaccines and independent of the pathogen and the sugar structural characteristics, O-antigen length did not result in being a critical parameter for GMMA immunogenicity. This work supports the identification of critical quality attributes to optimize GMMA vaccine design and improve vaccine efficacy and gives insights on the nature of the immune response induced by GMMA.

Chronic restraint stress increases social interaction in C57BL/6J mice monitoring through MiceProfiler analysis.

The social deficit is a prevailing symptom in stress-induced depression. Although social interaction behavior has been widely studied in humans and rodents, it is imprecise to record the social behavior between two free-moving mice via perusal. In the present study, we applied an approach to analyze the social behavior in mice using a software named "MiceProfiler." C57BL/6J mice were stressed via chronic restraint stress (CRS) and housed in three populations of different sizes as follows: single, three in a cage, and six in a cage. The MiceProfiler was used to analyze the video of behavioral repertoire and, the result showed that stressed and single housed mice exhibited more social interaction both in the contact time and contact activities. Furthermore, we investigated the effect of CRS on social behavior when the mice were housed in larger populations size (three or six in a cage) and found that, the CRS procedure promoted social interaction. However, the larger population size resulted in the less total contact time, less time of head-tail, and moving in an opposite way. Besides, the CRS mice showed less social avoidance while the mice from a larger population presented less active contact. And the CRS mice also exhibited a higher social hierarchy compared with the control. Our data indicated that mild restraint stress might increase the intercommunication between mice. Collectively, our findings provided a new evidence for social behavior study and the MiceProfiler could be a new tool to measure the social behaviors of rodents.

Accuracy of whole-genome sequence imputation using hybrid peeling in large pedigreed livestock populations

BackgroundThe coupling of appropriate sequencing strategies and imputation methods is critical for assembling large whole-genome sequence datasets from livestock populations for research and breeding. In this paper, we describe and validate the coupling of a sequencing strategy with the imputation method hybrid peeling in real animal breeding settings.MethodsWe used data from four pig populations of different size (18,349 to 107,815 individuals) that were widely genotyped at densities between 15,000 and 75,000 markers genome-wide. Around 2% of the individuals in each population were sequenced (most of them at 1× or 2× and 37–92 individuals per population, totalling 284, at 15–30×). We imputed whole-genome sequence data with hybrid peeling. We evaluated the imputation accuracy by removing the sequence data of the 284 individuals with high coverage, using a leave-one-out design. We simulated data that mimicked the sequencing strategy used in the real populations to quantify the factors that affected the individual-wise and variant-wise imputation accuracies using regression trees.ResultsImputation accuracy was high for the majority of individuals in all four populations (median individual-wise dosage correlation: 0.97). Imputation accuracy was lower for individuals in the earliest generations of each population than for the rest, due to the lack of marker array data for themselves and their ancestors. The main factors that determined the individual-wise imputation accuracy were the genotyping status, the availability of marker array data for immediate ancestors, and the degree of connectedness to the rest of the population, but sequencing coverage of the relatives had no effect. The main factors that determined variant-wise imputation accuracy were the minor allele frequency and the number of individuals with sequencing coverage at each variant site. Results were validated with the empirical observations.ConclusionsWe demonstrate that the coupling of an appropriate sequencing strategy and hybrid peeling is a powerful strategy for generating whole-genome sequence data with high accuracy in large pedigreed populations where only a small fraction of individuals (2%) had been sequenced, mostly at low coverage. This is a critical step for the successful implementation of whole-genome sequence data for genomic prediction and fine-mapping of causal variants.

Degree of fragmentation and population size do not adversely affect reproductive success of a rare shrub species, Banksia nivea (Proteaceae), in a naturally fragmented community

Abstract Fragmentation of plant communities is generally considered to be detrimental to the survival of the constituent species, especially those that are rare. We investigated the effects of fragmentation on reproductive biology in nine populations of the rare taxon Banksia nivea subsp. uliginosa, differing in size and habitat context. Small mammals were the main pollinator, with lower contributions from honeybees and birds (honeyeaters). There was no significant relationship between population size, fruit set and seed germinability. Fruit set was marginally highest (25.5 ± 3.4) in medium size populations and was variable over years. Lower fruit set (1.0 ± 0.6) in the smallest population may be due to inbreeding depression or lack of pollinators in a degraded habitat, but low fruit set was also observed in the largest population despite high levels of gene flow, possibly due to low pollinator visitation rate in a low-density population. Seeds from all populations had high germination success (&gt;93.4%). Predation occurred in up to 56% of fruit and increased with increasing population size, but was not significantly different between populations of different size. Our study provided evidence that the reproductive output in species in a naturally fragmented landscape system may be resilient to reduced population size and other influences of anthropogenic fragmentation.

Optimizing Selection of the Reference Population for Genotype Imputation From Array to Sequence Variants.

Imputation of high-density genotypes to whole-genome sequences (WGS) is a cost-effective method to increase the density of available markers within a population. Imputed genotypes have been successfully used for genomic selection and discovery of variants associated with traits of interest for the population. To allow for the use of imputed genotypes for genomic analyses, accuracy of imputation must be high. Accuracy of imputation is influenced by multiple factors, such as size and composition of the reference group, and the allele frequency of variants included. Understanding the use of imputed WGSs prior to the generation of the reference population is important, as accurate imputation might be more focused, for instance, on common or on rare variants. The aim of this study was to present and evaluate new methods to select animals for sequencing relying on a previously genotyped population. The Genetic Diversity Index method optimizes the number of unique haplotypes in the future reference population, while the Highly Segregating Haplotype selection method targets haplotype alleles found throughout the majority of the population of interest. First the WGSs of a dairy cattle population were simulated. The simulated sequences mimicked the linkage disequilibrium level and the variants’ frequency distribution observed in currently available Holstein sequences. Then, reference populations of different sizes, in which animals were selected using both novel methods proposed here as well as two other methods presented in previous studies, were created. Finally, accuracies of imputation obtained with different reference populations were compared against each other. The novel methods were found to have overall accuracies of imputation of more than 0.85. Accuracies of imputation of rare variants reached values above 0.50. In conclusion, if imputed sequences are to be used for discovery of novel associations between variants and traits of interest in the population, animals carrying novel information should be selected and, consequently, the Genetic Diversity Index method proposed here may be used. If sequences are to be used to impute the overall genotyped population, a reference population consisting of common haplotypes carriers selected using the proposed Highly Segregating Haplotype method is recommended.

Adapting in larger numbers can increase the vulnerability of Escherichia coli populations to environmental changes.

Larger populations generally adapt faster to their existing environment. However, it is unknown if the population size experienced during evolution influences the ability to face sudden environmental changes. To investigate this issue, we subjected replicate Escherichia coli populations of different sizes to experimental evolution in an environment containing a cocktail of three antibiotics. In this environment, the ability to actively efflux molecules outside the cell is expected to be a major fitness-affecting trait. We found that all the populations eventually reached similar fitness in the antibiotic cocktail despite adapting at different speeds, with the larger populations adapting faster. Surprisingly, although efflux activity (EA) enhanced in the smaller populations, it decayed in the larger ones. The evolution of EA was largely shaped by pleiotropic responses to selection and not by drift. This demonstrates that quantitative differences in population size can lead to qualitative differences (decay/enhancement) in the fate of a character during adaptation to identical environments. Furthermore, the larger populations showed inferior fitness upon sudden exposure to several alternative stressful environments. These observations provide a novel link between population size and vulnerability to environmental changes. Counterintuitively, adapting in larger numbers can render bacterial populations more vulnerable to abrupt environmental changes.

Erythrocyte Senescent Markers by Flow Cytometry

Background: Mature red blood cells lack protein synthesis and are unable to restore inactivated enzymes, damaged cytoskeleton and membrane proteins. An oxidation breakdown of band 3 is probably part of the mechanism leading to the generation of a senescent cell antigen. This specific signal serves for the clearance of RBCs by inducing the binding of autologous IgG and C3, leading to phagocytosis. In addition, phosphatidilserin molecules appear in the outer membrane and the CD47 expression diminishes. Methods: Erythrocytes of different ages from whole blood were studied by flow cytometry analysing light scatter proprieties, binding of autologous IgG, C3 complement deposits, externalization of phosphatidylserine and CD47 expression. Dot-plot analysis based on forward scatter versus side scatter parameters showed two RBCs populations of different sizes and density. RBCs were further incubated with Alexa 488 IgG, APC-anti-C3, PE-annexin-V and PE-CD47. The comparison of the values obtained for the different variables studied in SeRBC and YRBC populations was carried out by the Student t-test for matched samples or by the Wilcoxon test (after verification of the normality assumption). Results: The percentage of IgG and C3 positive cells was significantly higher in senescent red blood cells population. The fraction of annexin-V positive RBCs was also larger in SeRBCs while the CD47 expression was lower in this population. Conclusions: These results indicate that flow cytometry allow differenciation of erythrocytes populations of different ages, turning this tool into an useful alternative option to study erythrocyte aging process. These findings will contribute to a better understanding of the process and mechanisms involved in erythrocyte senescence process.

Detection of genetic purging and predictive value of purging parameters estimated in pedigreed populations.

The consequences of inbreeding for fitness are important in evolutionary and conservation biology, but can critically depend on genetic purging. However, estimating purging has proven elusive. Using PURGd software, we assess the performance of the Inbreeding-Purging (IP) model and of ancestral inbreeding (Fa) models to detect purging in simulated pedigreed populations, and to estimate parameters that allow reliably predicting the evolution of fitness under inbreeding. The power to detect purging in a single small population of size N is low for both models during the first few generations of inbreeding (t ≈ N/2), but increases for longer periods of slower inbreeding and is, on average, larger for the IP model. The ancestral inbreeding approach overestimates the rate of inbreeding depression during long inbreeding periods, and produces joint estimates of the effects of inbreeding and purging that lead to unreliable predictions for the evolution of fitness. The IP estimates of the rate of inbreeding depression become downwardly biased when obtained from long inbreeding processes. However, the effect of this bias is canceled out by a coupled downward bias in the estimate of the purging coefficient so that, unless the population is very small, the joint estimate of these two IP parameters yields good predictions of the evolution of mean fitness in populations of different sizes during periods of different lengths. Therefore, our results support the use of the IP model to detect inbreeding depression and purging, and to estimate reliable parameters for predictive purposes.

Mating pattern and pollen dispersal in the wild olive tree (Olea europaea subsp. cuspidata)

In this study, the mating system, contemporary pollen flow, and landscape pollen connectivity of the wild olive tree (Olea europaea subsp. cuspidata) were analyzed in a fragmented landscape of less than 4-km diameter located in north-western Ethiopia. Four remnant populations of different sizes were investigated. Eight highly polymorphic microsatellite markers were used to genotype 534 adults and 704 embryos. We used contrasting sampling schemes and different methodological approaches to analyze the pollen flow. We observed a lower rate of inbreeding and correlated mating in the fragmented vs. the non-fragmented subpopulation. Using parentage analysis, we detected a bidirectional pollen movement across subpopulations. Pollen flow was found to be directed towards small subpopulations based on parentage and anisotropic analysis. Pollen immigration amounted to more than 50%. Although most pollination occurred within a distance of less than 200 m, longer distance pollen movements of more than 3 km were also detected. Pollen dispersal in the large and dense subpopulation was reduced, and a smaller number of effective pollen sources were detected compared to a smaller fragmented subpopulation. We obtained consistent estimates for the number of effective pollen donors (approximately 6 per mother tree) using three different methods. The average pollen dispersal distance at the landscape level amounted to 276 m while at the local level, 174 m was estimated. Bigger trees were better pollen contributors than smaller trees. We showed here for the first time that pollen dispersal in wild olive follows a leptokurtic distribution.