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Sample records for affecting population dynamics

  1. How Resource Phenology Affects Consumer Population Dynamics.

    PubMed

    Bewick, Sharon; Cantrell, R Stephen; Cosner, Chris; Fagan, William F

    2016-02-01

    Climate change drives uneven phenology shifts across taxa, and this can result in changes to the phenological match between interacting species. Shifts in the relative phenology of partner species are well documented, but few studies have addressed the effects of such changes on population dynamics. To explore this, we develop a phenologically explicit model describing consumer-resource interactions. Focusing on scenarios for univoltine insects, we show how changes in resource phenology can be reinterpreted as transformations in the year-to-year recursion relationships defining consumer population dynamics. This perspective provides a straightforward path for interpreting the long-term population consequences of phenology change. Specifically, by relating the outcome of phenological shifts to species traits governing recursion relationships (e.g., consumer fecundity or competitive scenario), we demonstrate how changes in relative phenology can force systems into different dynamical regimes, with major implications for resource management, conservation, and other areas of applied dynamics. PMID:26807744

  2. Predicting when climate-driven phenotypic change affects population dynamics.

    PubMed

    McLean, Nina; Lawson, Callum R; Leech, Dave I; van de Pol, Martijn

    2016-06-01

    Species' responses to climate change are variable and diverse, yet our understanding of how different responses (e.g. physiological, behavioural, demographic) relate and how they affect the parameters most relevant for conservation (e.g. population persistence) is lacking. Despite this, studies that observe changes in one type of response typically assume that effects on population dynamics will occur, perhaps fallaciously. We use a hierarchical framework to explain and test when impacts of climate on traits (e.g. phenology) affect demographic rates (e.g. reproduction) and in turn population dynamics. Using this conceptual framework, we distinguish four mechanisms that can prevent lower-level responses from impacting population dynamics. Testable hypotheses were identified from the literature that suggest life-history and ecological characteristics which could predict when these mechanisms are likely to be important. A quantitative example on birds illustrates how, even with limited data and without fully-parameterized population models, new insights can be gained; differences among species in the impacts of climate-driven phenological changes on population growth were not explained by the number of broods or density dependence. Our approach helps to predict the types of species in which climate sensitivities of phenotypic traits have strong demographic and population consequences, which is crucial for conservation prioritization of data-deficient species. PMID:27062059

  3. The model of fungal population dynamics affected by nystatin

    NASA Astrophysics Data System (ADS)

    Voychuk, Sergei I.; Gromozova, Elena N.; Sadovskiy, Mikhail G.

    Fungal diseases are acute problems of the up-to-day medicine. Significant increase of resistance of microorganisms to the medically used antibiotics and a lack of new effective drugs follows in a growth of dosage of existing chemicals to solve the problem. Quite often such approach results in side effects on humans. Detailed study of fungi-antibiotic dynamics can identify new mechanisms and bring new ideas to overcome the microbial resistance with a lower dosage of antibiotics. In this study, the dynamics of the microbial population under antibiotic treatment was investigated. The effects of nystatin on the population of Saccharomyces cerevisiae yeasts were used as a model system. Nystatin effects were investigated both in liquid and solid media by viability tests. Dependence of nystatin action on osmotic gradient was evaluated in NaCl solutions. Influences of glucose and yeast extract were additionally analyzed. A "stepwise" pattern of the cell death caused by nystatin was the most intriguing. This pattern manifested in periodical changes of the stages of cell death against stages of resistance to the antibiotic. The mathematical model was proposed to describe cell-antibiotic interactions and nystatin viability effects in the liquid medium. The model implies that antibiotic ability to cause a cells death is significantly affected by the intracellular compounds, which came out of cells after their osmotic barriers were damaged

  4. How Predation and Landscape Fragmentation Affect Vole Population Dynamics

    PubMed Central

    Dalkvist, Trine; Sibly, Richard M.; Topping, Chris J.

    2011-01-01

    Background Microtine species in Fennoscandia display a distinct north-south gradient from regular cycles to stable populations. The gradient has often been attributed to changes in the interactions between microtines and their predators. Although the spatial structure of the environment is known to influence predator-prey dynamics of a wide range of species, it has scarcely been considered in relation to the Fennoscandian gradient. Furthermore, the length of microtine breeding season also displays a north-south gradient. However, little consideration has been given to its role in shaping or generating population cycles. Because these factors covary along the gradient it is difficult to distinguish their effects experimentally in the field. The distinction is here attempted using realistic agent-based modelling. Methodology/Principal Findings By using a spatially explicit computer simulation model based on behavioural and ecological data from the field vole (Microtus agrestis), we generated a number of repeated time series of vole densities whose mean population size and amplitude were measured. Subsequently, these time series were subjected to statistical autoregressive modelling, to investigate the effects on vole population dynamics of making predators more specialised, of altering the breeding season, and increasing the level of habitat fragmentation. We found that fragmentation as well as the presence of specialist predators are necessary for the occurrence of population cycles. Habitat fragmentation and predator assembly jointly determined cycle length and amplitude. Length of vole breeding season had little impact on the oscillations. Significance There is good agreement between our results and the experimental work from Fennoscandia, but our results allow distinction of causation that is hard to unravel in field experiments. We hope our results will help understand the reasons for cycle gradients observed in other areas. Our results clearly demonstrate the

  5. Spatial and spatiotemporal variation in metapopulation structure affects population dynamics in a passively dispersing arthropod.

    PubMed

    De Roissart, Annelies; Wang, Shaopeng; Bonte, Dries

    2015-11-01

    The spatial and temporal variation in the availability of suitable habitat within metapopulations determines colonization-extinction events, regulates local population sizes and eventually affects local population and metapopulation stability. Insights into the impact of such a spatiotemporal variation on the local population and metapopulation dynamics are principally derived from classical metapopulation theory and have not been experimentally validated. By manipulating spatial structure in artificial metapopulations of the spider mite Tetranychus urticae, we test to which degree spatial (mainland-island metapopulations) and spatiotemporal variation (classical metapopulations) in habitat availability affects the dynamics of the metapopulations relative to systems where habitat is constantly available in time and space (patchy metapopulations). Our experiment demonstrates that (i) spatial variation in habitat availability decreases variance in metapopulation size and decreases density-dependent dispersal at the metapopulation level, while (ii) spatiotemporal variation in habitat availability increases patch extinction rates, decreases local population and metapopulation sizes and decreases density dependence in population growth rates. We found dispersal to be negatively density dependent and overall low in the spatial variable mainland-island metapopulation. This demographic variation subsequently impacts local and regional population dynamics and determines patterns of metapopulation stability. Both local and metapopulation-level variabilities are minimized in mainland-island metapopulations relative to classical and patchy ones. PMID:25988264

  6. A shift from exploitation to interference competition with increasing density affects population and community dynamics.

    PubMed

    Holdridge, Erica M; Cuellar-Gempeler, Catalina; terHorst, Casey P

    2016-08-01

    Intraspecific competition influences population and community dynamics and occurs via two mechanisms. Exploitative competition is an indirect effect that occurs through use of a shared resource and depends on resource availability. Interference competition occurs by obstructing access to a resource and may not depend on resource availability. Our study tested whether the strength of interference competition changes with protozoa population density. We grew experimental microcosms of protozoa and bacteria under different combinations of protozoan density and basal resource availability. We then solved a dynamic predator-prey model for parameters of the functional response using population growth rates measured in our experiment. As population density increased, competition shifted from exploitation to interference, and competition was less dependent on resource levels. Surprisingly, the effect of resources was weakest when competition was the most intense. We found that at low population densities, competition was largely exploitative and resource availability had a large effect on population growth rates, but the effect of resources was much weaker at high densities. This shift in competitive mechanism could have implications for interspecific competition, trophic interactions, community diversity, and natural selection. We also tested whether this shift in the mechanism of competition with protozoa density affected the structure of the bacterial prey community. We found that both resources and protozoa density affected the structure of the bacterial prey community, suggesting that competitive mechanism may also affect trophic interactions. PMID:27551386

  7. A hyperparasite affects the population dynamics of a wild plant pathogen

    PubMed Central

    Tollenaere, C; Pernechele, B; Mäkinen, H S; Parratt, S R; Németh, M Z; Kovács, G M; Kiss, L; Tack, A J M; Laine, A-L

    2014-01-01

    Assessing the impact of natural enemies of plant and animal pathogens on their host's population dynamics is needed to determine the role of hyperparasites in affecting disease dynamics, and their potential for use in efficient control strategies of pathogens. Here, we focus on the long-term study describing metapopulation dynamics of an obligate pathogen, the powdery mildew (Podosphaera plantaginis) naturally infecting its wild host plant (Plantago lanceolata) in the fragmented landscape of the Åland archipelago (southwest Finland). Regionally, the pathogen persists through a balance of extinctions and colonizations, yet factors affecting extinction rates remain poorly understood. Mycoparasites of the genus Ampelomyces appear as good candidates for testing the role of a hyperparasite, i.e. a parasite of other parasites, in the regulation of their fungal hosts' population dynamics. For this purpose, we first designed a quantitative PCR assay for detection of Ampelomyces spp. in field-collected samples. This newly developed molecular test was then applied to a large-scale sampling within the Åland archipelago, revealing that Ampelomyces is a widespread hyperparasite in this system, with high variability in prevalence among populations. We found that the hyperparasite was more common on leaves where multiple powdery mildew strains coexist, a pattern that may be attributed to differential exposure. Moreover, the prevalence of Ampelomyces at the plant level negatively affected the overwinter survival of its fungal host. We conclude that this hyperparasite may likely impact on its host population dynamics and argue for increased focus on the role of hyperparasites in disease dynamics. PMID:25204419

  8. A hyperparasite affects the population dynamics of a wild plant pathogen.

    PubMed

    Tollenaere, C; Pernechele, B; Mäkinen, H S; Parratt, S R; Németh, M Z; Kovács, G M; Kiss, L; Tack, A J M; Laine, A-L

    2014-12-01

    Assessing the impact of natural enemies of plant and animal pathogens on their host's population dynamics is needed to determine the role of hyperparasites in affecting disease dynamics, and their potential for use in efficient control strategies of pathogens. Here, we focus on the long-term study describing metapopulation dynamics of an obligate pathogen, the powdery mildew (Podosphaera plantaginis) naturally infecting its wild host plant (Plantago lanceolata) in the fragmented landscape of the Åland archipelago (southwest Finland). Regionally, the pathogen persists through a balance of extinctions and colonizations, yet factors affecting extinction rates remain poorly understood. Mycoparasites of the genus Ampelomyces appear as good candidates for testing the role of a hyperparasite, i.e. a parasite of other parasites, in the regulation of their fungal hosts' population dynamics. For this purpose, we first designed a quantitative PCR assay for detection of Ampelomyces spp. in field-collected samples. This newly developed molecular test was then applied to a large-scale sampling within the Åland archipelago, revealing that Ampelomyces is a widespread hyperparasite in this system, with high variability in prevalence among populations. We found that the hyperparasite was more common on leaves where multiple powdery mildew strains coexist, a pattern that may be attributed to differential exposure. Moreover, the prevalence of Ampelomyces at the plant level negatively affected the overwinter survival of its fungal host. We conclude that this hyperparasite may likely impact on its host population dynamics and argue for increased focus on the role of hyperparasites in disease dynamics. PMID:25204419

  9. Population dynamics of dechlorinators and factors affecting the level and products of PCB dechlorination in sediments

    SciTech Connect

    Kim, J.S.; Sokol, R.C.; Liu, X.; Bethoney, C.M.; Rhee, G.Y.

    1996-12-31

    Microbial dechlorination of polychlorinated biphenyls (PCBs) often stops although a significant number of removable chlorines remain. To determine the reason for the cessation, we investigated the limitation of organic carbon, PCB bioavailability, and inhibition by metabolic products. Enrichment with carbon sources did not induce additional chlorination, indicating the plateau was not due to depletion of organic carbon. The bioavailability was not limiting, since a subcritical micelle concentration of the surfactant, which enhanced desorption without inhibiting dechlorinating microorganisms, failed to lower the plateau. Neither was it due to accumulation of metabolites, since no additional dechlorination was detected when plateau sediments were incubated with fresh medium. Similarly, dechlorination was not inhibited in freshly spiked sediment slurries. Dechlorination ended up at the same level with nearly identical congener profiles, regardless of treatment. These results indicate that cessation of dechlorination was due to the accumulation of daughter congeners, which cannot be used as electron acceptors by microbes. To determine whether the decreasing availability affected the microorganisms, we determined the population dynamics of dechlorinators using the most probable number technique. The growth dynamics of the dechlorinators mirrored the time course of dechlorination. It started when the population increased by two orders of magnitude. Once dechlorination stopped the dechlorinating population also began to decrease. When dechlorinators were inoculated into PCB-free sediments, the population decreased over time. The decrease of the population as dechlorination ceased confirms that the diminishing availability of congeners was the reason for the incomplete dechlorination. Recent findings have shown that a second phase of dechlorination of certain congeners can occur after a long lag. 45 refs., 8 figs.

  10. Memory and obesity affect the population dynamics of asexual freshwater planarians

    NASA Astrophysics Data System (ADS)

    Dunkel, Jörn; Talbot, Jared; Schötz, Eva-Maria

    2011-04-01

    Asexual reproduction in multicellular organisms is a complex biophysical process that is not yet well understood quantitatively. Here, we report a detailed population study for the asexual freshwater planarian Schmidtea mediterranea, which can reproduce via transverse fission due to a large stem cell contingent. Our long-term observations of isolated non-interacting planarian populations reveal that the characteristic fission waiting time distributions for head and tail fragments differ significantly from each other. The stochastic fission dynamics of tail fragments exhibits non-negligible memory effects, implying that an accurate mathematical description of future data should be based on non-Markovian tree models. By comparing the effective growth of non-interacting planarian populations with those of self-interacting populations, we are able to quantify the influence of interactions between flatworms and physical conditions on the population growth. A surprising result is the non-monotonic relationship between effective population growth rate and nutrient supply: planarians exhibit a tendency to become 'obese' if the feeding frequency exceeds a critical level, resulting in a decreased reproduction activity. This suggests that these flatworms, which possess many genes homologous to those of humans, could become a new model system for studying dietary effects on reproduction and regeneration in multicellular organisms.

  11. Ecological context and metapopulation dynamics affect sex-ratio variation among dioecious plant populations

    PubMed Central

    Field, David L.; Pickup, Melinda; Barrett, Spencer C. H.

    2013-01-01

    Background and Aims Populations of dioecious flowering plants commonly exhibit heterogeneity in sex ratios and deviations from the equilibrium expectation of equal numbers of females and males. Yet the role of ecological and demographic factors in contributing towards biased sex ratios is currently not well understood. Methods Species-level studies from the literature were analysed to investigate ecological correlates of among-population sex-ratio variation and metapopulation models and empirical data were used to explore the influence of demography and non-equilibrium conditions on flowering sex ratios. Key Results The survey revealed significant among-population heterogeneity in sex ratios and this was related to the degree of sampling effort. For some species, sex-ratio bias was associated with the proportion of non-reproductive individuals, with greater male bias in populations with a lower proportion of individuals that were flowering. Male-biased ratios were also found at higher altitudes and latitudes, and in more xeric sites. Simulations and empirical data indicated that clonal species exhibited greater heterogeneity in sex ratios than non-clonal species as a result of their slower approach to equilibrium. The simulations also indicated the importance of interactions between reproductive mode and founder effects, with greater departures from equilibrium in clonal populations with fewer founding individuals. Conclusions The results indicate that sex-based differences in costs of reproduction and non-equilibrium conditions can each play important roles in affecting flowering sex ratios in populations of dioecious plants. PMID:23444124

  12. Continuous and discrete extreme climatic events affecting the dynamics of a high-arctic reindeer population.

    PubMed

    Chan, Kung-Sik; Mysterud, Atle; Øritsland, Nils Are; Severinsen, Torbjørn; Stenseth, Nils Chr

    2005-10-01

    Climate at northern latitudes are currently changing both with regard to the mean and the temporal variability at any given site, increasing the frequency of extreme events such as cold and warm spells. Here we use a conceptually new modelling approach with two different dynamic terms of the climatic effects on a Svalbard reindeer population (the Brøggerhalvøya population) which underwent an extreme icing event ("locked pastures") with 80% reduction in population size during one winter (1993/94). One term captures the continuous and linear effect depending upon the Arctic Oscillation and another the discrete (rare) "event" process. The introduction of an "event" parameter describing the discrete extreme winter resulted in a more parsimonious model. Such an approach may be useful in strongly age-structured ungulate populations, with young and very old individuals being particularly prone to mortality factors during adverse conditions (resulting in a population structure that differs before and after extreme climatic events). A simulation study demonstrates that our approach is able to properly detect the ecological effects of such extreme climate events. PMID:16010537

  13. Seasonal timing of first rain storms affects rare plant population dynamics

    USGS Publications Warehouse

    Levine, J.M.; McEachern, A.K.; Cowan, C.

    2011-01-01

    A major challenge in forecasting the ecological consequences of climate change is understanding the relative importance of changes to mean conditions vs. changes to discrete climatic events, such as storms, frosts, or droughts. Here we show that the first major storm of the growing season strongly influences the population dynamics of three rare and endangered annual plant species in a coastal California (USA) ecosystem. In a field experiment we used moisture barriers and water addition to manipulate the timing and temperature associated with first major rains of the season. The three focal species showed two- to fivefold variation in per capita population growth rates between the different storm treatments, comparable to variation found in a prior experiment imposing eightfold differences in season-long precipitation. Variation in germination was a major demographic driver of how two of three species responded to the first rains. For one of these species, the timing of the storm was the most critical determinant of its germination, while the other showed enhanced germination with colder storm temperatures. The role of temperature was further supported by laboratory trials showing enhanced germination in cooler treatments. Our work suggests that, because of species-specific cues for demographic transitions such as germination, changes to discrete climate events may be as, if not more, important than changes to season-long variables.

  14. From facilitation to competition: temperature-driven shift in dominant plant interactions affects population dynamics in seminatural grasslands.

    PubMed

    Olsen, Siri L; Töpper, Joachim P; Skarpaas, Olav; Vandvik, Vigdis; Klanderud, Kari

    2016-05-01

    Biotic interactions are often ignored in assessments of climate change impacts. However, climate-related changes in species interactions, often mediated through increased dominance of certain species or functional groups, may have important implications for how species respond to climate warming and altered precipitation patterns. We examined how a dominant plant functional group affected the population dynamics of four co-occurring forb species by experimentally removing graminoids in seminatural grasslands. Specifically, we explored how the interaction between dominants and subordinates varied with climate by replicating the removal experiment across a climate grid consisting of 12 field sites spanning broad-scale temperature and precipitation gradients in southern Norway. Biotic interactions affected population growth rates of all study species, and the net outcome of interactions between dominants and subordinates switched from facilitation to competition with increasing temperature along the temperature gradient. The impacts of competitive interactions on subordinates in the warmer sites could primarily be attributed to reduced plant survival. Whereas the response to dominant removal varied with temperature, there was no overall effect of precipitation on the balance between competition and facilitation. Our findings suggest that global warming may increase the relative importance of competitive interactions in seminatural grasslands across a wide range of precipitation levels, thereby favouring highly competitive dominant species over subordinate species. As a result, seminatural grasslands may become increasingly dependent on disturbance (i.e. traditional management such as grazing and mowing) to maintain viable populations of subordinate species and thereby biodiversity under future climates. Our study highlights the importance of population-level studies replicated under different climatic conditions for understanding the underlying mechanisms of climate

  15. Affective Dynamics in Psychopathology

    PubMed Central

    Trull, Timothy J.; Lane, Sean P.; Koval, Peter; Ebner-Priemer, Ulrich W.

    2016-01-01

    We discuss three varieties of affective dynamics (affective instability, emotional inertia, and emotional differentiation). In each case, we suggest how these affective dynamics should be operationalized and measured in daily life using time-intensive methods, like ecological momentary assessment or ambulatory assessment, and recommend time-sensitive analyses that take into account not only the variability but also the temporal dependency of reports. Studies that explore how these affective dynamics are associated with psychological disorders and symptoms are reviewed, and we emphasize that these affective processes are within a nexus of other components of emotion regulation.

  16. Wolf population dynamics in the U.S. Northern Rocky Mountains are affected by recruitment and human-caused mortality

    USGS Publications Warehouse

    Gude, J.A.; Mitchell, M.S.; Russell, R.E.; Sime, C.A.; Bangs, E.E.; Mech, L.D.; Ream, R.R.

    2012-01-01

    Reliable analyses can help wildlife managers make good decisions, which are particularly critical for controversial decisions such as wolf (Canis lupus) harvest. Creel and Rotella (2010) recently predicted substantial population declines in Montana wolf populations due to harvest, in contrast to predictions made by Montana Fish, Wildlife and Parks (MFWP). We replicated their analyses considering only those years in which field monitoring was consistent, and we considered the effect of annual variation in recruitment on wolf population growth. Rather than assuming constant rates, we used model selection methods to evaluate and incorporate models of factors driving recruitment and human-caused mortality rates in wolf populations in the Northern Rocky Mountains. Using data from 27 area-years of intensive wolf monitoring, we show that variation in both recruitment and human-caused mortality affect annual wolf population growth rates and that human-caused mortality rates have increased with the sizes of wolf populations. We document that recruitment rates have decreased over time, and we speculate that rates have decreased with increasing population sizes and/or that the ability of current field resources to document recruitment rates has recently become less successful as the number of wolves in the region has increased. Estimates of positive wolf population growth in Montana from our top models are consistent with field observations and estimates previously made by MFWP for 2008-2010, whereas the predictions for declining wolf populations of Creel and Rotella (2010) are not. Familiarity with limitations of raw data, obtained first-hand or through consultation with scientists who collected the data, helps generate more reliable inferences and conclusions in analyses of publicly available datasets. Additionally, development of efficient monitoring methods for wolves is a pressing need, so that analyses such as ours will be possible in future years when fewer resources

  17. Factors affecting population dynamics of leaf beetles in a subarctic region: The interplay between climate warming and pollution decline.

    PubMed

    Zvereva, Elena L; Hunter, Mark D; Zverev, Vitali; Kozlov, Mikhail V

    2016-10-01

    Understanding the mechanisms by which abiotic drivers, such as climate and pollution, influence population dynamics of animals is important for our ability to predict the population trajectories of individual species under different global change scenarios. We monitored four leaf beetle species (Coleoptera: Chrysomelidae) feeding on willows (Salix spp.) in 13 sites along a pollution gradient in subarctic forests of north-western Russia from 1993 to 2014. During a subset of years, we also measured the impacts of natural enemies and host plant quality on the performance of one of these species, Chrysomela lapponica. Spring and fall temperatures increased by 2.5-3°C during the 21-year observation period, while emissions of sulfur dioxide and heavy metals from the nickel-copper smelter at Monchegorsk decreased fivefold. However, contrary to predictions of increasing herbivory with climate warming, and in spite of discovered increase in host plant quality with increase in temperatures, none of the beetle species became more abundant during the past 20years. No directional trends were observed in densities of either Phratora vitellinae or Plagiodera versicolora, whereas densities of both C. lapponica and Gonioctena pallida showed a simultaneous rapid 20-fold decline in the early 2000s, remaining at very low levels thereafter. Time series analysis and model selection indicated that these abrupt population declines were associated with decreases in aerial emissions from the smelter. Observed declines in the population densities of C. lapponica can be explained by increases in mortality from natural enemies due to the combined action of climate warming and declining pollution. This pattern suggests that at least in some tri-trophic systems, top-down factors override bottom-up effects and govern the impacts of environmental changes on insect herbivores. PMID:27266523

  18. Evolutionary dynamics in structured populations

    PubMed Central

    Nowak, Martin A.; Tarnita, Corina E.; Antal, Tibor

    2010-01-01

    Evolutionary dynamics shape the living world around us. At the centre of every evolutionary process is a population of reproducing individuals. The structure of that population affects evolutionary dynamics. The individuals can be molecules, cells, viruses, multicellular organisms or humans. Whenever the fitness of individuals depends on the relative abundance of phenotypes in the population, we are in the realm of evolutionary game theory. Evolutionary game theory is a general approach that can describe the competition of species in an ecosystem, the interaction between hosts and parasites, between viruses and cells, and also the spread of ideas and behaviours in the human population. In this perspective, we review the recent advances in evolutionary game dynamics with a particular emphasis on stochastic approaches in finite sized and structured populations. We give simple, fundamental laws that determine how natural selection chooses between competing strategies. We study the well-mixed population, evolutionary graph theory, games in phenotype space and evolutionary set theory. We apply these results to the evolution of cooperation. The mechanism that leads to the evolution of cooperation in these settings could be called ‘spatial selection’: cooperators prevail against defectors by clustering in physical or other spaces. PMID:20008382

  19. Modeling sandhill crane population dynamics

    USGS Publications Warehouse

    Johnson, D.H.

    1979-01-01

    The impact of sport hunting on the Central Flyway population of sandhill cranes (Grus canadensis) has been a subject of controversy for several years. A recent study (Buller 1979) presented new and important information on sandhill crane population dynamics. The present report is intended to incorporate that and other information into a mathematical model for the purpose of assessing the long-range impact of hunting on the population of sandhill cranes.The model is a simple deterministic system that embodies density-dependent rates of survival and recruitment. The model employs four kinds of data: (1) spring population size of sandhill cranes, estimated from aerial surveys to be between 250,000 and 400,000 birds; (2) age composition in fall, estimated for 1974-76 to be 11.3% young; (3) annual harvest of cranes, estimated from a variety of sources to be about 5 to 7% of the spring population; and (4) age composition of harvested cranes, which was difficult to estimate but suggests that immatures were 2 to 4 times as vulnerable to hunting as adults.Because the true nature of sandhill crane population dynamics remains so poorly understood, it was necessary to try numerous (768 in all) combinations of survival and recruitment functions, and focus on the relatively few (37) that yielded population sizes and age structures comparable to those extant in the real population. Hunting was then applied to those simulated populations. In all combinations, hunting resulted in a lower asymptotic crane population, the decline ranging from 5 to 54%. The median decline was 22%, which suggests that a hunted sandhill crane population might be about three-fourths as large as it would be if left unhunted. Results apply to the aggregate of the three subspecies in the Central Flyway; individual subspecies or populations could be affected to a greater or lesser degree.

  20. Factors Affecting the Reproduction, Recruitment, Habitat, and Population Dynamics of Pallid Sturgeon and Shovelnose Sturgeon in the Missouri River

    USGS Publications Warehouse

    Korschgen, Carl E., (Edited By)

    2007-01-01

    For more than a hundred years, human activities have modified the natural forces that control the Missouri River and its native fish fauna. While the ecological effects of regulation and channel engineering are understood in general, the current understanding is not sufficient to guide river restoration and management. The U.S. Geological Survey (USGS) is in the third year of a multiagency research effort to determine the ecological requirements for reproduction and survival of the endangered pallid sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (Scaphirhynchus platorhynchus) in the Missouri River. The multidisciplinary research strategy includes components of behavior, physiology, habitat use, habitat availability, and population modeling of all life stages. Shovelnose sturgeon are used to design the strategy because they are closely related to the pallid sturgeon and are often used as a surrogate species to develop new research tools or to examine the effects of management actions or environmental variables on sturgeon biology and habitat use. During fiscal years 2005 and 2006, the U.S. Army Corps of Engineers (USACE) provided funds to USGS for tasks associated with the Comprehensive Sturgeon Research Program (CSRP) and for tasks associated with evaluation of the Sturgeon Response to Flow Modifications (SRFM). Because work activities of CSRP and SRFM are so integrated, we are providing information on activities that have been consolidated at the task level. These task activities represent chapters in this report.

  1. Evolutionary dynamics in set structured populations

    PubMed Central

    Tarnita, Corina E.; Antal, Tibor; Ohtsuki, Hisashi; Nowak, Martin A.

    2009-01-01

    Evolutionary dynamics are strongly affected by population structure. The outcome of an evolutionary process in a well-mixed population can be very different from that in a structured population. We introduce a powerful method to study dynamical population structure: evolutionary set theory. The individuals of a population are distributed over sets. Individuals interact with others who are in the same set. Any 2 individuals can have several sets in common. Some sets can be empty, whereas others have many members. Interactions occur in terms of an evolutionary game. The payoff of the game is interpreted as fitness. Both the strategy and the set memberships change under evolutionary updating. Therefore, the population structure itself is a consequence of evolutionary dynamics. We construct a general mathematical approach for studying any evolutionary game in set structured populations. As a particular example, we study the evolution of cooperation and derive precise conditions for cooperators to be selected over defectors. PMID:19433793

  2. Dynamics of resilience in forced migration: a 1-year follow-up study of longitudinal associations with mental health in a conflict-affected, ethnic Muslim population

    PubMed Central

    Siriwardhana, Chesmal; Abas, Melanie; Siribaddana, Sisira; Sumathipala, Athula; Stewart, Robert

    2015-01-01

    Objective The concept of ‘resilience’ is of increasing interest in studies of mental health in populations facing adversity. However, lack of longitudinal data on the dynamics of resilience and non-usage of resilience-specific measurements have prevented a better understanding of resilience-mental health interactions. Hence, the present study was conducted to investigate the stability of levels of resilience and its associations with sociodemographic and mental health exposures in a conflict-affected internal-migrant population in Sri Lanka. Design A prospective follow-up study of 1 year. Setting Puttalam district of North Western province in postconflict Sri Lanka (baseline in 2011, follow-up in 2012). Participants An ethnic Muslim population internally displaced 20 years ago (in 1990) from Northern Sri Lanka, aged 18 or above and currently in the process of return migration. Measures It was hypothesised that levels of resilience would be associated with mental health outcomes. Resilience was measured on both occasions using the 14-item Resilience Scale (RS-14), social support by the Multidimensional Social Support Scale and Lubben Social Network Scale and common mental disorders by the Patient Health Questionnaire (PHQ). Results Of 450 participants interviewed at baseline in 2011, 338 (75.1%) were re-interviewed in 2012 after a 1-year follow-up. The mean resilience scores measured by RS-14 were 80.2 (95% CI 78.6 to 81.9) at baseline and 84.9 (83.5 to 86.3) at follow-up. At both time points, lower resilience was independently associated with food insecurity, lower social support availability and social isolation. At both time points, there were significant associations with common mental disorders (CMDs) in unadjusted analyses, but they only showed independence at baseline. The CMD prevalence, maintenance and incidence at follow-up was 8.3%, 28.2% and 2.2%, respectively. Conclusions In this displaced population facing a potential reduction in adversity

  3. Flood trends and population dynamics

    NASA Astrophysics Data System (ADS)

    Di Baldassarre, G.

    2012-04-01

    Since the earliest recorded civilizations, such as those in Mesopotamia and Egypt that developed in the fertile floodplains of the Tigris and Euphrates and Nile rivers, humans tend to settle in flood prone areas as they offer favorable conditions for economic development. However, floodplains are also exposed to flood disasters that might cause severe socio-economic and environmental damages not to mention losses of human lives. A flood event turns to be a disaster when it coincides with a vulnerable environment exceeding society's capacity to manage the adverse consequences. This presentation discusses the link between hydrological risk and population change by referring to the outcomes of scientific works recently carried out in Africa and Europe. More specifically, it is shown that the severity of flood disasters, currently affecting more than 100 million people a year, might be seriously exacerbated because of population change. In fact, flood exposure and/or vulnerability might increase because of rapid population growth (and its spatial and temporal dynamics, e.g. urbanization) in the African continent and because of population ageing in many European countries. Lastly, timely and economically sustainable actions to mitigate this increasing hydrological risk are critically evaluated.

  4. Dynamic Synchronization of Teacher-Students Affection in Affective Instruction

    ERIC Educational Resources Information Center

    Zhang, Wenhai; Lu, Jiamei

    2011-01-01

    Based on Bower's affective network theory, the article links the dynamic analysis of affective factors in affective instruction, and presents affective instruction strategic of dynamic synchronization between teacher and students to implement the best ideal mood that promotes students' cognition and affection together. In the process of teaching,…

  5. COULD ETHINYL ESTRADIOL AFFECT THE POPULATION BIOLOGY OF CUNNER, TAUTOGOLABRUS ADSPERSUS

    EPA Science Inventory

    Endocrine disrupting chemicals in the environment may disturb the population dynamics of wildlife by affecting reproductive output and embryonic development of organisms. This study used a population model to evaluate whether ethinyl estradiol (EE2 could affect cunner Tautogolabr...

  6. AMPHIBIAN POPULATION DYNAMICS

    EPA Science Inventory

    Agriculture has contributed to loss of vertebrate biodiversity in many regions, including the U.S. Corn Belt. Amphibian populations, in particular, have experienced widespread and often inexplicable declines, range reductions, and extinctions. However, few attempts have been made...

  7. Discreteness effects in population dynamics

    NASA Astrophysics Data System (ADS)

    Guevara Hidalgo, Esteban; Lecomte, Vivien

    2016-05-01

    We analyse numerically the effects of small population size in the initial transient regime of a simple example population dynamics. These effects play an important role for the numerical determination of large deviation functions of additive observables for stochastic processes. A method commonly used in order to determine such functions is the so-called cloning algorithm which in its non-constant population version essentially reduces to the determination of the growth rate of a population, averaged over many realizations of the dynamics. However, the averaging of populations is highly dependent not only on the number of realizations of the population dynamics, and on the initial population size but also on the cut-off time (or population) considered to stop their numerical evolution. This may result in an over-influence of discreteness effects at initial times, caused by small population size. We overcome these effects by introducing a (realization-dependent) time delay in the evolution of populations, additional to the discarding of the initial transient regime of the population growth where these discreteness effects are strong. We show that the improvement in the estimation of the large deviation function comes precisely from these two main contributions.

  8. Population Dynamics of Viral Inactivation

    NASA Astrophysics Data System (ADS)

    Freeman, Krista; Li, Dong; Behrens, Manja; Streletzky, Kiril; Olsson, Ulf; Evilevitch, Alex

    We have investigated the population dynamics of viral inactivation in vitrousing time-resolved cryo electron microscopy combined with light and X-ray scattering techniques. Using bacteriophage λ as a model system for pressurized double-stranded DNA viruses, we found that virions incubated with their cell receptor eject their genome in a stochastic triggering process. The triggering of DNA ejection occurs in a non synchronized manner after the receptor addition, resulting in an exponential decay of the number of genome-filled viruses with time. We have explored the characteristic time constant of this triggering process at different temperatures, salt conditions, and packaged genome lengths. Furthermore, using the temperature dependence we determined an activation energy for DNA ejections. The dependences of the time constant and activation energy on internal DNA pressure, affected by salt conditions and encapsidated genome length, suggest that the triggering process is directly dependent on the conformational state of the encapsidated DNA. The results of this work provide insight into how the in vivo kinetics of the spread of viral infection are influenced by intra- and extra cellular environmental conditions. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1252522.

  9. Redefining the "carrier" state for foot-and-mouth disease from the dynamics of virus persistence in endemically affected cattle populations.

    PubMed

    Bronsvoort, Barend M deC; Handel, Ian G; Nfon, Charles K; Sørensen, Karl-Johan; Malirat, Viviana; Bergmann, Ingrid; Tanya, Vincent N; Morgan, Kenton L

    2016-01-01

    The foot-and-mouth disease virus (FMDV) "carrier" state was defined by van Bekkum in 1959. It was based on the recovery of infectious virus 28 days or more post infection and has been a useful construct for experimental studies. Using historic data from 1,107 cattle, collected as part of a population based study of endemic FMD in 2000, we developed a mixed effects logistic regression model to predict the probability of recovering viable FMDV by probang and culture, conditional on the animal's age and time since last reported outbreak. We constructed a second set of models to predict the probability of an animal being probang positive given its antibody response in three common non-structural protein (NSP) ELISAs and its age. We argue that, in natural ecological settings, the current definition of a "carrier" fails to capture the dynamics of either persistence of the virus (as measured by recovery using probangs) or the uncertainty in transmission from such animals that the term implies. In these respects it is not particularly useful. We therefore propose the first predictive statistical models for identifying persistently infected cattle in an endemic setting that captures some of the dynamics of the probability of persistence. Furthermore, we provide a set of predictive tools to use alongside NSP ELISAs to help target persistently infected cattle. PMID:27381947

  10. Redefining the “carrier” state for foot-and-mouth disease from the dynamics of virus persistence in endemically affected cattle populations

    PubMed Central

    Bronsvoort, Barend M. deC.; Handel, Ian G.; Nfon, Charles K.; Sørensen, Karl-Johan; Malirat, Viviana; Bergmann, Ingrid; Tanya, Vincent N.; Morgan, Kenton L.

    2016-01-01

    The foot-and-mouth disease virus (FMDV) “carrier” state was defined by van Bekkum in 1959. It was based on the recovery of infectious virus 28 days or more post infection and has been a useful construct for experimental studies. Using historic data from 1,107 cattle, collected as part of a population based study of endemic FMD in 2000, we developed a mixed effects logistic regression model to predict the probability of recovering viable FMDV by probang and culture, conditional on the animal’s age and time since last reported outbreak. We constructed a second set of models to predict the probability of an animal being probang positive given its antibody response in three common non-structural protein (NSP) ELISAs and its age. We argue that, in natural ecological settings, the current definition of a ”carrier” fails to capture the dynamics of either persistence of the virus (as measured by recovery using probangs) or the uncertainty in transmission from such animals that the term implies. In these respects it is not particularly useful. We therefore propose the first predictive statistical models for identifying persistently infected cattle in an endemic setting that captures some of the dynamics of the probability of persistence. Furthermore, we provide a set of predictive tools to use alongside NSP ELISAs to help target persistently infected cattle. PMID:27381947

  11. Structural dynamics and ecology of flatfish populations

    NASA Astrophysics Data System (ADS)

    Bailey, Kevin M.

    1997-11-01

    The concept of structure in populations of marine fishes is fundamental to how we manage and conduct research on these resources. The degree of population structure ranges widely among flatfishes. Although we know that large populations tend to be subdivided into local populations, based on morphological, meristic and reproductive characteristics, these data often conflict with evidence on genetic stock structure, due to the scale and organization of movement within the metapopulation. Movement of individuals between local subpopulations and colonization events on a macroecological scale are probably important to some flatfish populations. Dispersal of larvae is known to be a major factor affecting population mixing. Some flatfishes have planktonic stages of long duration and for these species there is often, but not always, little population structure; gene flow sometimes may be limited by oceanographic features, such as eddies and fronts. At the juvenile stage dispersal can result in colonization of under-utilized habitats; however, for flatfishes with strong habitat requirements, this type of event may be less likely when suitable habitats are fragmented. Complex population structure has major implications for management, e.g. lumping harvested populations with little gene flow can have detrimental local effects. Moreover, the issue of population structure and movement influences the interpretation of research data, where populations are generally treated as closed systems. There is currently a strong need for a multidisciplinary approach to study fish population dynamics and the structure of their populations. This research should involve molecular geneticists, population geneticists, animal behaviourists and ecologists. Migration mechanisms, colonization and extinction events, gene flow and density-dependent movements are subject areas of great importance to managing large harvested populations, but our understanding of them at ecological scales, at least for

  12. Evolutionary dynamics on interdependent populations

    NASA Astrophysics Data System (ADS)

    Gómez-Gardeñes, Jesús; Gracia-Lázaro, Carlos; Floría, Luis Mario; Moreno, Yamir

    2012-11-01

    Although several mechanisms can promote cooperative behavior, there is no general consensus about why cooperation survives when the most profitable action for an individual is to defect, especially when the population is well mixed. Here we show that when a replicator such as evolutionary game dynamics takes place on interdependent networks, cooperative behavior is fixed on the system. Remarkably, we analytically and numerically show that this is even the case for well-mixed populations. Our results open the path to mechanisms able to sustain cooperation and can provide hints for controlling its rise and fall in a variety of biological and social systems.

  13. Individual-based model of young-of-the-year striped bass population dynamics. II. Factors affecting recruitment in the Potomac River, Maryland

    SciTech Connect

    Cowan, J.H. ); Rose, K.A. ); Rutherford, E.S.; Houde, E.D. )

    1993-05-01

    An individual-based model of the population dynamics of young-of-the-year striped bass Morone saxatilis in the Potomac River, Maryland, was used to test the hypothesis that historically high recruitment variability can be explained by changes in environmental and biological factors that result in relatively small changes in growth and mortality rates of striped bass larvae. The four factors examined were (1) size distribution of female parents, (2) zooplankton prey density during the development of striped bass larvae, (3) density of completing larval white perch M. americana, and (4) temperature during larval development. Simulation results suggest that variations in female size and in prey for larvae alone could cause 10-fold variability in recruitment. But no single factor alone caused changes in vital rates of age-0 fish that could account for the 145-fold variability in the Potomac River index of juvenile recruitment. However, combined positive or negative effects of two or more factors resulted in more than a 150-fold simulated recruitment variability, suggesting that combinations of factors can account for the high observed annual variability in striped bass recruitment success. Higher cumulative mortality of feeding larvae and younger life stages than of juveniles was common to all simulations. supporting the contention that striped bass year-class strength is determined prior to metamorphosis. 76 refs., 7 figs., 4 tabs.

  14. Dynamic clustering of bacterial population

    NASA Astrophysics Data System (ADS)

    Ko, Elizabeth P.; Yomo, Tetsuya; Urabe, Itaru

    1994-08-01

    Bacterial cells having the same genotype were observed to split into a few clusters of phenotypes with various levels of enzyme activity. When the mixture of these phenotypically heterogeneous but genotypically homogeneous cells was cultivated in a liquid medium, the distribution of the population size of each cluster of phenotypes showed various kinds of dynamic oscillations. In addition, when this dynamic behavior was examined for the cells of the single colony, various patterns of shifting of homogeneous to heterogeneous lineage and vice versa were observed in the population. The results imply that differentiation of the cells with the same genotype can occur without spatial information and even under the same environment where the cells interact globally without spatial constrait. This interesting phenomenon totally contradicts the conventional biology that the genotype of a cell uniquely determines the phenotype of the cell and its progeny, but is consistent with the theoretical model of cell differentiation presented in the following paper. The sources of discrepancy between the existing theory in molecular biology and our results were discussed and it is concluded that in understanding a complex living system, a simple model consisting of the essence of the complex system can be constructed justifying the observed properties of the molecules in the system which provide free interactions.

  15. Cyanobacteria Affect Fitness and Genetic Structure of Experimental Daphnia Populations.

    PubMed

    Drugă, Bogdan; Turko, Patrick; Spaak, Piet; Pomati, Francesco

    2016-04-01

    Zooplankton communities can be strongly affected by cyanobacterial blooms, especially species of genus Daphnia, which are key-species in lake ecosystems. Here, we explored the effect of microcystin/nonmicrocystin (MC/non-MC) producing cyanobacteria in the diet of experimental Daphnia galeata populations composed of eight genotypes. We used D. galeata clones hatched from ephippia 10 to 60 years old, which were first tested in monocultures, and then exposed for 10 weeks as mixed populations to three food treatments consisting of green algae combined with cyanobacteria able/unable of producing MC. We measured the expression of nine genes potentially involved in Daphnia acclimation to cyanobacteria: six protease genes, one ubiquitin-conjugating enzyme gene, and two rRNA genes, and then we tracked the dynamics of the genotypes in mixed populations. The expression pattern of one protease and the ubiquitin-conjugating enzyme genes was positively correlated with the increased fitness of competing clones in the presence of cyanobacteria, suggesting physiological plasticity. The genotype dynamics in mixed populations was only partially related to the growth rates of clones in monocultures and varied strongly with the food. Our results revealed strong intraspecific differences in the tolerance of D. galeata clones to MC/non-MC-producing cyanobacteria in their diet, suggesting microevolutionary effects. PMID:26943751

  16. Modeling population dynamics: A quantile approach.

    PubMed

    Chavas, Jean-Paul

    2015-04-01

    The paper investigates the modeling of population dynamics, both conceptually and empirically. It presents a reduced form representation that provides a flexible characterization of population dynamics. It leads to the specification of a threshold quantile autoregression (TQAR) model, which captures nonlinear dynamics by allowing lag effects to vary across quantiles of the distribution as well as with previous population levels. The usefulness of the model is illustrated in an application to the dynamics of lynx population. We find statistical evidence that the quantile autoregression parameters vary across quantiles (thus rejecting the AR model as well as the TAR model) as well as with past populations (thus rejecting the quantile autoregression QAR model). The results document the nature of dynamics and cycle in the lynx population over time. They show how both the period of the cycle and the speed of population adjustment vary with population level and environmental conditions. PMID:25661501

  17. Between-Population Outbreeding Affects Plant Defence

    PubMed Central

    Leimu, Roosa; Fischer, Markus

    2010-01-01

    Between-population crosses may replenish genetic variation of populations, but may also result in outbreeding depression. Apart from direct effects on plant fitness, these outbreeding effects can also alter plant-herbivore interactions by influencing plant tolerance and resistance to herbivory. We investigated effects of experimental within- and between-population outbreeding on herbivore resistance, tolerance and plant fitness using plants from 13 to 19 Lychnis flos-cuculi populations. We found no evidence for outbreeding depression in resistance reflected by the amount of leaf area consumed. However, herbivore performance was greater when fed on plants from between-population compared to within-population crosses. This can reflect outbreeding depression in resistance and/or outbreeding effects on plant quality for the herbivores. The effects of type of cross on the relationship between herbivore damage and plant fitness varied among populations. This demonstrates how between-population outbreeding effects on tolerance range from outbreeding depression to outbreeding benefits among plant populations. Finally, herbivore damage strengthened the observed outbreeding effects on plant fitness in several populations. These results raise novel considerations on the impact of outbreeding on the joint evolution of resistance and tolerance, and on the evolution of multiple defence strategies. PMID:20838662

  18. How Population Growth Affects Linkage Disequilibrium

    PubMed Central

    Rogers, Alan R.

    2014-01-01

    The “LD curve” relates the linkage disequilibrium (LD) between pairs of nucleotide sites to the distance that separates them along the chromosome. The shape of this curve reflects natural selection, admixture between populations, and the history of population size. This article derives new results about the last of these effects. When a population expands in size, the LD curve grows steeper, and this effect is especially pronounced following a bottleneck in population size. When a population shrinks, the LD curve rises but remains relatively flat. As LD converges toward a new equilibrium, its time path may not be monotonic. Following an episode of growth, for example, it declines to a low value before rising toward the new equilibrium. These changes happen at different rates for different LD statistics. They are especially slow for estimates of σd2, which therefore allow inferences about ancient population history. For the human population of Europe, these results suggest a history of population growth. PMID:24907258

  19. Are population dynamics of shorebirds affected by El Niño/Southern Oscillation (ENSO) while on their non-breeding grounds in Ecuador?

    NASA Astrophysics Data System (ADS)

    O'Hara, Patrick D.; Haase, Ben J. M.; Elner, Robert W.; Smith, Barry D.; Kenyon, Jamie K.

    2007-08-01

    Declines in avian populations are a global concern, particularly for species that migrate between Arctic-temperate and tropical locations. Long-term population studies offer opportunities to detect and document ecological effects attributable to long-term climatic cycles such as the El Niño/Southern Oscillation (ENSO). In this study, we report possible population-level effects of such climatic cycles on shorebird species that use two non-breeding season sites in Ecuador (Santa Elena peninsula area, near La Libertad). During our 9-year study period (1991/1992-1999/2000), there was a particularly strong ENSO warm phase event during 1997/1998. Population trend data for three species of shorebird, Western Sandpipers ( Calidris mauri), Semipalmated Sandpipers ( C. pusilla), and Least Sandpipers ( C. minutilla), indicated abundances generally declined during the 1990s, but there was an increase in the proportion of first-year birds and their abundance in the years following the 1997/1998 ENSO warm phase. There was some support for variation in apparent survivorship associated with the onset of the ENSO warm phase event in our population models, based on capture-mark-recapture data. Following the 1997/1998 ENSO event onset, individuals for all three species were significantly lighter during the non-breeding season ( F1,3789 = 6.6, p = 0.01). Least-squares mean mass (controlling for size, sex and day of capture) for first-year birds dropped significantly more than for adults following ENSO (first-year mass loss = 0.69 ± 0.12 g; adult mass loss = 0.34 ± 0.11 g, F1,3789 = 5.31, p = 0.021), and least-squares mean mass dropped most during the period when sandpipers prepare for northward migration by gaining mass and moulting into breeding plumage. Least Sandpipers may have declined the most in mean mass following ENSO (0.76 ± 0.19 g), whereas Semipalmated Sandpipers were 0.52 ± 0.12 g lighter, and Western Sandpipers 0.40 ± 0.13 g lighter, but overall variation among

  20. Dynamic musical communication of core affect.

    PubMed

    Flaig, Nicole K; Large, Edward W

    2014-01-01

    Is there something special about the way music communicates feelings? Theorists since Meyer (1956) have attempted to explain how music could stimulate varied and subtle affective experiences by violating learned expectancies, or by mimicking other forms of social interaction. Our proposal is that music speaks to the brain in its own language; it need not imitate any other form of communication. We review recent theoretical and empirical literature, which suggests that all conscious processes consist of dynamic neural events, produced by spatially dispersed processes in the physical brain. Intentional thought and affective experience arise as dynamical aspects of neural events taking place in multiple brain areas simultaneously. At any given moment, this content comprises a unified "scene" that is integrated into a dynamic core through synchrony of neuronal oscillations. We propose that (1) neurodynamic synchrony with musical stimuli gives rise to musical qualia including tonal and temporal expectancies, and that (2) music-synchronous responses couple into core neurodynamics, enabling music to directly modulate core affect. Expressive music performance, for example, may recruit rhythm-synchronous neural responses to support affective communication. We suggest that the dynamic relationship between musical expression and the experience of affect presents a unique opportunity for the study of emotional experience. This may help elucidate the neural mechanisms underlying arousal and valence, and offer a new approach to exploring the complex dynamics of the how and why of emotional experience. PMID:24672492

  1. Arabinoxylan‐oligosaccharides (AXOS) affect the protein/carbohydrate fermentation balance and microbial population dynamics of the Simulator of Human Intestinal Microbial Ecosystem

    PubMed Central

    Sanchez, J. I.; Marzorati, M.; Grootaert, C.; Baran, M.; Van Craeyveld, V.; Courtin, C. M.; Broekaert, W. F.; Delcour, J. A.; Verstraete, W.; Van de Wiele, T.

    2009-01-01

    Summary Arabinoxylan‐oligosaccharides (AXOS) are a recently newly discovered class of candidate prebiotics as – depending on their structure – they are fermented in different regions of gastrointestinal tract. This can have an impact on the protein/carbohydrate fermentation balance in the large intestine and, thus, affect the generation of potentially toxic metabolites in the colon originating from proteolytic activity. In this study, we screened different AXOS preparations for their impact on the in vitro intestinal fermentation activity and microbial community structure. Short‐term fermentation experiments with AXOS with an average degree of polymerization (avDP) of 29 allowed part of the oligosaccharides to reach the distal colon, and decreased the concentration of proteolytic markers, whereas AXOS with lower avDP were primarily fermented in the proximal colon. Additionally, prolonged supplementation of AXOS with avDP 29 to the Simulator of Human Intestinal Microbial Ecosystem (SHIME) reactor decreased levels of the toxic proteolytic markers phenol and p‐cresol in the two distal colon compartments and increased concentrations of beneficial short‐chain fatty acids (SCFA) in all colon vessels (25–48%). Denaturant gradient gel electrophoresis (DGGE) analysis indicated that AXOS supplementation only slightly modified the total microbial community, implying that the observed effects on fermentation markers are mainly caused by changes in fermentation activity. Finally, specific quantitative PCR (qPCR) analysis showed that AXOS supplementation significantly increased the amount of health‐promoting lactobacilli as well as of Bacteroides–Prevotella and Clostridium coccoides–Eubacterium rectale groups. These data allow concluding that AXOS are promising candidates to modulate the microbial metabolism in the distal colon. PMID:21261885

  2. Long-term dynamics of Typha populations

    USGS Publications Warehouse

    Grace, J.B.; Wetzel, R.G.

    1998-01-01

    The zonation of Typha populations in an experimental pond in Michigan was re-examined 15 years after the original sampling to gain insight into the long-term dynamics. Current distributions of Typha populations were also examined in additional experimental ponds at the site that have been maintained for 23 years. The zonation between T. latifolia and T. angustifolia in the previously studied pond 15 years after the initial sampling revealed that the density and distribution of shoots had not changed significantly. Thus, it appears that previously reported results (based on 7- year old populations) have remained consistent over time. Additional insight into the interaction between these two taxa was sought by comparing mixed and monoculture stands in five experimental ponds that have remained undisturbed for their 23-year history. The maximum depth of T. latifolia, the shallow- water species, was not significantly reduced when growing in the presence of the more flood tolerant T. angustifolia. In contrast, the minimum depth of T. angustifolia was reduced from 0 to 37 cm when in the presence of T. latifolia. When total populations were compared between monoculture and mixed stands, the average density of T. angustifolia shoots was 59.4 percent lower in mixed stands while the density of T. latifolia was 32 percent lower, with T. angustifolia most affected at shallow depths (reduced by 92 percent) and T. latifolia most affected at the deepest depths (reduced by 60 percent). These long-term observations indicate that competitive displacement between Typha taxa has remained stable over time.

  3. How Colored Environmental Noise Affects Population Extinction

    NASA Astrophysics Data System (ADS)

    Kamenev, Alex; Meerson, Baruch; Shklovskii, Boris

    2008-12-01

    Environmental noise can cause an exponential reduction in the mean time to extinction (MTE) of an isolated population. We study this effect on an example of a stochastic birth-death process with rates modulated by a colored (that is, correlated) Gaussian noise. A path integral formulation yields a transparent way of evaluating the MTE and finding the optimal realization of the environmental noise that determines the most probable path to extinction. The population-size dependence of the MTE changes from exponential in the absence of the environmental noise to a power law for a short-correlated noise and to no dependence for long-correlated noise. We also establish the validity domains of the white-noise limit and adiabatic limit.

  4. Modeling seasonal interactions in the population dynamics of migratory birds

    USGS Publications Warehouse

    Runge, M.C.; Marra, P.P.

    2005-01-01

    Understanding the population dynamics of migratory birds requires understanding the relevant biological events that occur during breeding, migratory, and overwintering periods. The few available population models for passerine birds focus on breeding-season events, disregard or oversimplify events during nonbreeding periods, and ignore interactions that occur between periods of the annual cycle. Identifying and explicitly incorporating seasonal interactions into population models for migratory birds could provide important insights about when population limitation actually occurs in the annual cycle. We present a population model for the annual cycle of a migratory bird, based on the American Redstart (Setophaga ruticilla) but more generally applicable, that examines the importance of seasonal interactions by incorporating: (1) density dependence during the breeding and winter seasons, (2) a carry-over effect of winter habitat on breeding-season productivity, and (3) the effects of behavioral dominance on seasonal and habitat specific demographic rates. First, we show that habitat availability on both the wintering and breeding grounds can strongly affect equilibrium population size and sex ratio. Second, sex ratio dynamics, as mediated by behavioral dominance, can affect all other aspects of population dynamics. Third, carry-over effects can be strong, especially when winter events are limiting. These results suggest that understanding the population dynamics of migratory birds may require more consideration of the seasonal interactions induced by carry-over effects and density dependence in multiple seasons. This model provides a framework in which to explore more fully these seasonal dynamics and a context for estimation of life history parameters.

  5. Evolution of specialization under non-equilibrium population dynamics.

    PubMed

    Nurmi, Tuomas; Parvinen, Kalle

    2013-03-21

    We analyze the evolution of specialization in resource utilization in a mechanistically underpinned discrete-time model using the adaptive dynamics approach. We assume two nutritionally equivalent resources that in the absence of consumers grow sigmoidally towards a resource-specific carrying capacity. The consumers use resources according to the law of mass-action with rates involving trade-off. The resulting discrete-time model for the consumer population has over-compensatory dynamics. We illuminate the way non-equilibrium population dynamics affect the evolutionary dynamics of the resource consumption rates, and show that evolution to the trimorphic coexistence of a generalist and two specialists is possible due to asynchronous non-equilibrium population dynamics of the specialists. In addition, various forms of cyclic evolutionary dynamics are possible. Furthermore, evolutionary suicide may occur even without Allee effects and demographic stochasticity. PMID:23306058

  6. Dynamics of Affective States during Complex Learning

    ERIC Educational Resources Information Center

    D'Mello, Sidney; Graesser, Art

    2012-01-01

    We propose a model to explain the dynamics of affective states that emerge during deep learning activities. The model predicts that learners in a state of engagement/flow will experience cognitive disequilibrium and confusion when they face contradictions, incongruities, anomalies, obstacles to goals, and other impasses. Learners revert into the…

  7. Population Dynamics of Genetic Regulatory Networks

    NASA Astrophysics Data System (ADS)

    Braun, Erez

    2005-03-01

    Unlike common objects in physics, a biological cell processes information. The cell interprets its genome and transforms the genomic information content, through the action of genetic regulatory networks, into proteins which in turn dictate its metabolism, functionality and morphology. Understanding the dynamics of a population of biological cells presents a unique challenge. It requires to link the intracellular dynamics of gene regulation, through the mechanism of cell division, to the level of the population. We present experiments studying adaptive dynamics of populations of genetically homogeneous microorganisms (yeast), grown for long durations under steady conditions. We focus on population dynamics that do not involve random genetic mutations. Our experiments follow the long-term dynamics of the population distributions and allow to quantify the correlations among generations. We focus on three interconnected issues: adaptation of genetically homogeneous populations following environmental changes, selection processes on the population and population variability and expression distributions. We show that while the population exhibits specific short-term responses to environmental inputs, it eventually adapts to a robust steady-state, largely independent of external conditions. Cycles of medium-switch show that the adapted state is imprinted in the population and that this memory is maintained for many generations. To further study population adaptation, we utilize the process of gene recruitment whereby a gene naturally regulated by a specific promoter is placed under a different regulatory system. This naturally occurring process has been recognized as a major driving force in evolution. We have recruited an essential gene to a foreign regulatory network and followed the population long-term dynamics. Rewiring of the regulatory network allows us to expose their complex dynamics and phase space structure.

  8. Population dynamics of interacting spiking neurons

    NASA Astrophysics Data System (ADS)

    Mattia, Maurizio; del Giudice, Paolo

    2002-11-01

    A dynamical equation is derived for the spike emission rate ν(t) of a homogeneous network of integrate-and-fire (IF) neurons in a mean-field theoretical framework, where the activity of the single cell depends both on the mean afferent current (the ``field'') and on its fluctuations. Finite-size effects are taken into account, by a stochastic extension of the dynamical equation for the ν their effect on the collective activity is studied in detail. Conditions for the local stability of the collective activity are shown to be naturally and simply expressed in terms of (the slope of) the single neuron, static, current-to-rate transfer function. In the framework of the local analysis, we studied the spectral properties of the time-dependent collective activity of the finite network in an asynchronous state; finite-size fluctuations act as an ongoing self-stimulation, which probes the spectral structure of the system on a wide frequency range. The power spectrum of ν exhibits modes ranging from very high frequency (depending on spike transmission delays), which are responsible for instability, to oscillations at a few Hz, direct expression of the diffusion process describing the population dynamics. The latter ``diffusion'' slow modes do not contribute to the stability conditions. Their characteristic times govern the transient response of the network; these reaction times also exhibit a simple dependence on the slope of the neuron transfer function. We speculate on the possible relevance of our results for the change in the characteristic response time of a neural population during the learning process which shapes the synaptic couplings, thereby affecting the slope of the transfer function. There is remarkable agreement of the theoretical predictions with simulations of a network of IF neurons with a constant leakage term for the membrane potential.

  9. Comparing models of Red Knot population dynamics

    USGS Publications Warehouse

    McGowan, Conor

    2015-01-01

    Predictive population modeling contributes to our basic scientific understanding of population dynamics, but can also inform management decisions by evaluating alternative actions in virtual environments. Quantitative models mathematically reflect scientific hypotheses about how a system functions. In Delaware Bay, mid-Atlantic Coast, USA, to more effectively manage horseshoe crab (Limulus polyphemus) harvests and protect Red Knot (Calidris canutus rufa) populations, models are used to compare harvest actions and predict the impacts on crab and knot populations. Management has been chiefly driven by the core hypothesis that horseshoe crab egg abundance governs the survival and reproduction of migrating Red Knots that stopover in the Bay during spring migration. However, recently, hypotheses proposing that knot dynamics are governed by cyclical lemming dynamics garnered some support in data analyses. In this paper, I present alternative models of Red Knot population dynamics to reflect alternative hypotheses. Using 2 models with different lemming population cycle lengths and 2 models with different horseshoe crab effects, I project the knot population into the future under environmental stochasticity and parametric uncertainty with each model. I then compare each model's predictions to 10 yr of population monitoring from Delaware Bay. Using Bayes' theorem and model weight updating, models can accrue weight or support for one or another hypothesis of population dynamics. With 4 models of Red Knot population dynamics and only 10 yr of data, no hypothesis clearly predicted population count data better than another. The collapsed lemming cycle model performed best, accruing ~35% of the model weight, followed closely by the horseshoe crab egg abundance model, which accrued ~30% of the weight. The models that predicted no decline or stable populations (i.e. the 4-yr lemming cycle model and the weak horseshoe crab effect model) were the most weakly supported.

  10. Dynamic Random Networks in Dynamic Populations

    NASA Astrophysics Data System (ADS)

    Britton, Tom; Lindholm, Mathias

    2010-05-01

    We consider a random network evolving in continuous time in which new nodes are born and old may die, and where undirected edges between nodes are created randomly and may also disappear. The node population is Markovian and so is the creation and deletion of edges, given the node population. Each node is equipped with a random social index and the intensity at which a node creates new edges is proportional to the social index, and the neighbour is either chosen uniformly or proportional to its social index in a modification of the model. We derive properties of the network as time and the node population tends to infinity. In particular, the degree-distribution is shown to be a mixed Poisson distribution which may exhibit a heavy tail (e.g. power-law) if the social index distribution has a heavy tail. The limiting results are verified by means of simulations, and the model is fitted to a network of sexual contacts.

  11. How Interactions Affect Multiple Kinesin Dynamics

    NASA Astrophysics Data System (ADS)

    Kolomeisky, Anatoly

    2013-03-01

    Intracellullar transport is supported by several classes of enzymatic molecules known as motor proteins. Cellular cargos are frequently transported by teams of motor proteins, and recent experimental and theoretical studies uncovered many features of such complex dynamics. Here we investigate theoretically the role of nonmechanical interactions between kinesin motor proteins and microtubules in the collective motion of motor proteins. Our analysis is based on stochastic model that explicitly takes into account all chemical and mechanical transitions. Nonmechanical interactions are assumed to affect kinesin mechanochemistry only when the motors are separated by less than 3 microtubule lattice sites, and it is shown that relatively weak interaction energies can have a significant effect on collective motor dynamics. In agreement with optical trapping experiments on structurally defined kinesin complexes, the model predicts that these effects primarily occur when cargos are transported against loads exceeding single-kinesin stalling forces. These results highlights the complex dynamics of multiple motor proteins in cellular transport phenomena.

  12. Stage-Structured Population Dynamics of AEDES AEGYPTI

    NASA Astrophysics Data System (ADS)

    Yusoff, Nuraini; Budin, Harun; Ismail, Salemah

    Aedes aegypti is the main vector in the transmission of dengue fever, a vector-borne disease affecting world population living in tropical and sub-tropical countries. Better understanding of the dynamics of its population growth will help in the efforts of controlling the spread of this disease. In looking at the population dynamics of Aedes aegypti, this paper explored the stage-structured modeling of the population growth of the mosquito using the matrix population model. The life cycle of the mosquito was divided into five stages: eggs, larvae, pupae, adult1 and adult2. Developmental rates were obtained for the average Malaysian temperature and these were used in constructing the transition matrix for the matrix model. The model, which was based only on temperature, projected that the population of Aedes aegypti will blow up with time, which is not realistic. For further work, other factors need to be taken into account to obtain a more realistic result.

  13. Immigration-extinction dynamics of stochastic populations

    NASA Astrophysics Data System (ADS)

    Meerson, Baruch; Ovaskainen, Otso

    2013-07-01

    How high should be the rate of immigration into a stochastic population in order to significantly reduce the probability of observing the population become extinct? Is there any relation between the population size distributions with and without immigration? Under what conditions can one justify the simple patch occupancy models, which ignore the population distribution and its dynamics in a patch, and treat a patch simply as either occupied or empty? We answer these questions by exactly solving a simple stochastic model obtained by adding a steady immigration to a variant of the Verhulst model: a prototypical model of an isolated stochastic population.

  14. Population dynamics with and without selection

    NASA Astrophysics Data System (ADS)

    Pȩkalski, Andrzej; Sznajd-Weron, Katarzyna

    2001-03-01

    A model describing population dynamics is presented. We study the effect of selection pressure and inbreeding on the time evolution of the population and the chances of survival. We find that the selection is in general beneficial, enabling survival of a population whose size is declining. Inbreeding reduces the survival chances since it leads to clustering of individuals. We have also found, in agreement with biological data, that there is a threshold value of the initial size of the population, as well as of the habitat, below which the population will almost certainly become extinct. We present analytical and computer simulation approaches.

  15. Population dynamics on heterogeneous bacterial substrates

    NASA Astrophysics Data System (ADS)

    Mobius, Wolfram; Murray, Andrew W.; Nelson, David R.

    2012-02-01

    How species invade new territories and how these range expansions influence the population's genotypes are important questions in the field of population genetics. The majority of work addressing these questions focuses on homogeneous environments. Much less is known about the population dynamics and population genetics when the environmental conditions are heterogeneous in space. To better understand range expansions in two-dimensional heterogeneous environments, we employ a system of bacteria and bacteriophage, the viruses of bacteria. Thereby, the bacteria constitute the environment in which a population of bacteriophages expands. The spread of phage constitutes itself in lysis of bacteria and thus formation of clear regions on bacterial lawns, called plaques. We study the population dynamics and genetics of the expanding page for various patterns of environments.

  16. Travelling waves in vole population dynamics

    NASA Astrophysics Data System (ADS)

    Ranta, Esa; Kaitala, Veijo

    1997-12-01

    Spatial self-organization patterns in population dynamics have been anticipated, but demonstrating their existence requires sampling over long periods of time at a range of sites. Voles cause severe economic damage and are therefore extensively monitored, providing a source of the required data. Using two long-term data sets we now report the existence of travelling waves in vole population numbers.

  17. Resveratrol Does Not Affect Health, Longevity in Population Study

    MedlinePlus

    ... You are here Home Resveratrol does not affect health, longevity in population study May 16, 2014 Resveratrol, ... disease. Researchers have found it to improve the health (and in some cases, longevity) of animals, including ...

  18. Human population dynamics in Europe over the Last Glacial Maximum

    PubMed Central

    Tallavaara, Miikka; Luoto, Miska; Korhonen, Natalia; Järvinen, Heikki; Seppä, Heikki

    2015-01-01

    The severe cooling and the expansion of the ice sheets during the Last Glacial Maximum (LGM), 27,000–19,000 y ago (27–19 ky ago) had a major impact on plant and animal populations, including humans. Changes in human population size and range have affected our genetic evolution, and recent modeling efforts have reaffirmed the importance of population dynamics in cultural and linguistic evolution, as well. However, in the absence of historical records, estimating past population levels has remained difficult. Here we show that it is possible to model spatially explicit human population dynamics from the pre-LGM at 30 ky ago through the LGM to the Late Glacial in Europe by using climate envelope modeling tools and modern ethnographic datasets to construct a population calibration model. The simulated range and size of the human population correspond significantly with spatiotemporal patterns in the archaeological data, suggesting that climate was a major driver of population dynamics 30–13 ky ago. The simulated population size declined from about 330,000 people at 30 ky ago to a minimum of 130,000 people at 23 ky ago. The Late Glacial population growth was fastest during Greenland interstadial 1, and by 13 ky ago, there were almost 410,000 people in Europe. Even during the coldest part of the LGM, the climatically suitable area for human habitation remained unfragmented and covered 36% of Europe. PMID:26100880

  19. Human population dynamics in Europe over the Last Glacial Maximum.

    PubMed

    Tallavaara, Miikka; Luoto, Miska; Korhonen, Natalia; Järvinen, Heikki; Seppä, Heikki

    2015-07-01

    The severe cooling and the expansion of the ice sheets during the Last Glacial Maximum (LGM), 27,000-19,000 y ago (27-19 ky ago) had a major impact on plant and animal populations, including humans. Changes in human population size and range have affected our genetic evolution, and recent modeling efforts have reaffirmed the importance of population dynamics in cultural and linguistic evolution, as well. However, in the absence of historical records, estimating past population levels has remained difficult. Here we show that it is possible to model spatially explicit human population dynamics from the pre-LGM at 30 ky ago through the LGM to the Late Glacial in Europe by using climate envelope modeling tools and modern ethnographic datasets to construct a population calibration model. The simulated range and size of the human population correspond significantly with spatiotemporal patterns in the archaeological data, suggesting that climate was a major driver of population dynamics 30-13 ky ago. The simulated population size declined from about 330,000 people at 30 ky ago to a minimum of 130,000 people at 23 ky ago. The Late Glacial population growth was fastest during Greenland interstadial 1, and by 13 ky ago, there were almost 410,000 people in Europe. Even during the coldest part of the LGM, the climatically suitable area for human habitation remained unfragmented and covered 36% of Europe. PMID:26100880

  20. Deterministic evolutionary game dynamics in finite populations.

    PubMed

    Altrock, Philipp M; Traulsen, Arne

    2009-07-01

    Evolutionary game dynamics describes the spreading of successful strategies in a population of reproducing individuals. Typically, the microscopic definition of strategy spreading is stochastic such that the dynamics becomes deterministic only in infinitely large populations. Here, we present a microscopic birth-death process that has a fully deterministic strong selection limit in well-mixed populations of any size. Additionally, under weak selection, from this process the frequency-dependent Moran process is recovered. This makes it a natural extension of the usual evolutionary dynamics under weak selection. We find simple expressions for the fixation probabilities and average fixation times of the process in evolutionary games with two players and two strategies. For cyclic games with two players and three strategies, we show that the resulting deterministic dynamics crucially depends on the initial condition in a nontrivial way. PMID:19658731

  1. Population dynamics and regulation in the cave salamander Speleomantes strinatii

    NASA Astrophysics Data System (ADS)

    Salvidio, Sebastiano

    2007-05-01

    Time series analysis has been used to evaluate the mechanisms regulating population dynamics of mammals and insects, but has been rarely applied to amphibian populations. In this study, the influence of endogenous (density-dependent) and exogenous (density-independent) factors regulating population dynamics of the terrestrial plethodontid salamander Speleomantes strinatii was analysed by means of time series and multiple regression analyses. During the period 1993 2005, S. strinatii population abundance, estimated by a standardised temporary removal method, displayed relatively low fluctuations, and the autocorrelation function (ACF) analysis showed that the time series had a noncyclic structure. The partial rate correlation function (PRCF) indicated that a strong first-order negative feedback dominated the endogenous dynamics. Stepwise multiple regression analysis showed that the only climatic factor influencing population growth rate was the minimum winter temperature. Thus, at least during the study period, endogenous, density-dependent negative feedback was the main factor affecting the growth rate of the salamander population, whereas stochastic environmental variables, such as temperature and rainfall, seemed to play a minor role in regulation. These results stress the importance of considering both exogenous and endogenous factors when analysing amphibian long-term population dynamics.

  2. Multispecies population dynamics of prebiotic compositional assemblies.

    PubMed

    Markovitch, Omer; Lancet, Doron

    2014-09-21

    Present life portrays a two-tier phenomenology: molecules compose supramolecular structures, such as cells or organisms, which in turn portray population behaviors, including selection, evolution and ecological dynamics. Prebiotic models have often focused on evolution in populations of self-replicating molecules, without explicitly invoking the intermediate molecular-to-supramolecular transition. Here, we explore a prebiotic model that allows one to relate parameters of chemical interaction networks within molecular assemblies to emergent population dynamics. We use the graded autocatalysis replication domain (GARD) model, which simulates the network dynamics within amphiphile-containing molecular assemblies, and exhibits quasi-stationary compositional states termed compotype species. These grow by catalyzed accretion, divide and propagate their compositional information to progeny in a replication-like manner. The model allows us to ask how molecular network parameters influence assembly evolution and population dynamics parameters. In 1000 computer simulations, each embodying different parameter set of the global chemical interaction network parameters, we observed a wide range of behaviors. These were analyzed by a multi species logistic model often used for analyzing population ecology (r-K or Lotka-Volterra competition model). We found that compotypes with a larger intrinsic molecular repertoire show a higher intrinsic growth (r) and lower carrying capacity (K), as well as lower replication fidelity. This supports a prebiotic scenario initiated by fast-replicating assemblies with a high molecular diversity, evolving into more faithful replicators with narrower molecular repertoires. PMID:24831416

  3. Animal population dynamics: Identification of critical components

    USGS Publications Warehouse

    Emlen, J.M.; Pikitch, E.K.

    1989-01-01

    There is a growing interest in the use of population dynamics models in environmental risk assessment and the promulgation of environmental regulatory policies. Unfortunately, because of species and areal differences in the physical and biotic influences on population dynamics, such models must almost inevitably be both complex and species- or site-specific. Given the emormous variety of species and sites of potential concern, this fact presents a problem; it simply is not possible to construct models for all species and circumstances. Therefore, it is useful, before building predictive population models, to discover what input parameters are of critical importance to the desired output. This information should enable the construction of simpler and more generalizable models. As a first step, it is useful to consider population models as composed to two, partly separable classes, one comprising the purely mechanical descriptors of dynamics from given demographic parameter values, and the other describing the modulation of the demographic parameters by environmental factors (changes in physical environment, species interactions, pathogens, xenobiotic chemicals). This division permits sensitivity analyses to be run on the first of these classes, providing guidance for subsequent model simplification. We here apply such a sensitivity analysis to network models of mammalian and avian population dynamics.

  4. Population dynamics and the ecological stability of obligate pollination mutualisms

    USGS Publications Warehouse

    Holland, J. Nathaniel; DeAngelis, Donald L.

    2001-01-01

    Mutualistic interactions almost always produce both costs and benefits for each of the interacting species. It is the difference between gross benefits and costs that determines the net benefit and the per-capita effect on each of the interacting populations. For example, the net benefit of obligate pollinators, such as yucca and senita moths, to plants is determined by the difference between the number of ovules fertilized from moth pollination and the number of ovules eaten by the pollinator's larvae. It is clear that if pollinator populations are large, then, because many eggs are laid, costs to plants are large, whereas, if pollinator populations are small, gross benefits are low due to lack of pollination. Even though the size and dynamics of the pollinator population are likely to be crucial, their importance has been neglected in the investigation of mechanisms, such as selective fruit abortion, that can limit costs and increase net benefits. Here, we suggest that both the population size and dynamics of pollinators are important in determining the net benefits to plants, and that fruit abortion can significantly affect these. We develop a model of mutualism between populations of plants and their pollinating seed-predators to explore the ecological consequences of fruit abortion on pollinator population dynamics and the net effect on plants. We demonstrate that the benefit to a plant population is unimodal as a function of pollinator abundance, relative to the abundance of flowers. Both selective abortion of fruit with eggs and random abortion of fruit, without reference to whether they have eggs or not, can limit pollinator population size. This can increase the net benefits to the plant population by limiting the number of eggs laid, if the pollination rate remains high. However, fruit abortion can possibly destabilize the pollinator population, with negative consequences for the plant population.

  5. Expression of Nucleolin Affects Microtubule Dynamics.

    PubMed

    Gaume, Xavier; Place, Christophe; Delage, Helene; Mongelard, Fabien; Monier, Karine; Bouvet, Philippe

    2016-01-01

    Nucleolin is present in diverse cellular compartments and is involved in a variety of cellular processes from nucleolar structure and function to intracellular trafficking, cell adhesion and migration. Recently, nucleolin has been localized at the mature centriole where it is involved in microtubule nucleation and anchoring. Although this new function of nucleolin linked to microtubule regulation has been identified, the global effects of nucleolin on microtubule dynamics have not been addressed yet. In the present study, we analyzed the roles of nucleolin protein levels on global microtubule dynamics by tracking the EB3 microtubule plus end binding protein in live cells. We have found that during microtubule growth phases, nucleolin affects both the speed and life time of polymerization and by analyzing catastrophe events, we showed that nucleolin reduces catastrophe frequency. This new property of nucleolin was then confirmed in a cold induced microtubule depolymerization experiment in which we have found that cold resistant microtubules were totally destabilized in nucleolin depleted cells. Altogether, our data demonstrate a new function of nucleolin on microtubule stabilization, thus bringing novel insights into understanding the multifunctional properties of nucleolin in healthy and cancer cells. PMID:27309529

  6. Expression of Nucleolin Affects Microtubule Dynamics

    PubMed Central

    Gaume, Xavier; Place, Christophe; Delage, Helene; Mongelard, Fabien; Monier, Karine; Bouvet, Philippe

    2016-01-01

    Nucleolin is present in diverse cellular compartments and is involved in a variety of cellular processes from nucleolar structure and function to intracellular trafficking, cell adhesion and migration. Recently, nucleolin has been localized at the mature centriole where it is involved in microtubule nucleation and anchoring. Although this new function of nucleolin linked to microtubule regulation has been identified, the global effects of nucleolin on microtubule dynamics have not been addressed yet. In the present study, we analyzed the roles of nucleolin protein levels on global microtubule dynamics by tracking the EB3 microtubule plus end binding protein in live cells. We have found that during microtubule growth phases, nucleolin affects both the speed and life time of polymerization and by analyzing catastrophe events, we showed that nucleolin reduces catastrophe frequency. This new property of nucleolin was then confirmed in a cold induced microtubule depolymerization experiment in which we have found that cold resistant microtubules were totally destabilized in nucleolin depleted cells. Altogether, our data demonstrate a new function of nucleolin on microtubule stabilization, thus bringing novel insights into understanding the multifunctional properties of nucleolin in healthy and cancer cells. PMID:27309529

  7. Evolutionary dynamics of general group interactions in structured populations.

    PubMed

    Li, Aming; Broom, Mark; Du, Jinming; Wang, Long

    2016-02-01

    The evolution of populations is influenced by many factors, and the simple classical models have been developed in a number of important ways. Both population structure and multiplayer interactions have been shown to significantly affect the evolution of important properties, such as the level of cooperation or of aggressive behavior. Here we combine these two key factors and develop the evolutionary dynamics of general group interactions in structured populations represented by regular graphs. The traditional linear and threshold public goods games are adopted as models to address the dynamics. We show that for linear group interactions, population structure can favor the evolution of cooperation compared to the well-mixed case, and we see that the more neighbors there are, the harder it is for cooperators to persist in structured populations. We further show that threshold group interactions could lead to the emergence of cooperation even in well-mixed populations. Here population structure sometimes inhibits cooperation for the threshold public goods game, where depending on the benefit to cost ratio, the outcomes are bistability or a monomorphic population of defectors or cooperators. Our results suggest, counterintuitively, that structured populations are not always beneficial for the evolution of cooperation for nonlinear group interactions. PMID:26986362

  8. Evolutionary dynamics of general group interactions in structured populations

    NASA Astrophysics Data System (ADS)

    Li, Aming; Broom, Mark; Du, Jinming; Wang, Long

    2016-02-01

    The evolution of populations is influenced by many factors, and the simple classical models have been developed in a number of important ways. Both population structure and multiplayer interactions have been shown to significantly affect the evolution of important properties, such as the level of cooperation or of aggressive behavior. Here we combine these two key factors and develop the evolutionary dynamics of general group interactions in structured populations represented by regular graphs. The traditional linear and threshold public goods games are adopted as models to address the dynamics. We show that for linear group interactions, population structure can favor the evolution of cooperation compared to the well-mixed case, and we see that the more neighbors there are, the harder it is for cooperators to persist in structured populations. We further show that threshold group interactions could lead to the emergence of cooperation even in well-mixed populations. Here population structure sometimes inhibits cooperation for the threshold public goods game, where depending on the benefit to cost ratio, the outcomes are bistability or a monomorphic population of defectors or cooperators. Our results suggest, counterintuitively, that structured populations are not always beneficial for the evolution of cooperation for nonlinear group interactions.

  9. Stochastic population dynamics in populations of western terrestrial garter snakes with divergent life histories

    USGS Publications Warehouse

    Miller, David A.; Clark, W.R.; Arnold, S.J.; Bronikowski, A.M.

    2011-01-01

    Comparative evaluations of population dynamics in species with temporal and spatial variation in life-history traits are rare because they require long-term demographic time series from multiple populations. We present such an analysis using demographic data collected during the interval 1978-1996 for six populations of western terrestrial garter snakes (Thamnophis elegans) from two evolutionarily divergent ecotypes. Three replicate populations from a slow-living ecotype, found in mountain meadows of northeastern California, were characterized by individuals that develop slowly, mature late, reproduce infrequently with small reproductive effort, and live longer than individuals of three populations of a fast-living ecotype found at lakeshore locales. We constructed matrix population models for each of the populations based on 8-13 years of data per population and analyzed both deterministic dynamics based on mean annual vital rates and stochastic dynamics incorporating annual variation in vital rates. (1) Contributions of highly variable vital rates to fitness (??s) were buffered against the negative effects of stochastic variation, and this relationship was consistent with differences between the meadow (M-slow) and lakeshore (L-fast) ecotypes. (2) Annual variation in the proportion of gravid females had the greatest negative effect among all vital rates on ?? s. The magnitude of variation in the proportion of gravid females and its effect on ??s was greater in M-slow than L-fast populations. (3) Variation in the proportion of gravid females, in turn, depended on annual variation in prey availability, and its effect on ??s was 4- 23 times greater in M-slow than L-fast populations. In addition to differences in stochastic dynamics between ecotypes, we also found higher mean mortality rates across all age classes in the L-fast populations. Our results suggest that both deterministic and stochastic selective forces have affected the evolution of divergent life

  10. Rate of language evolution is affected by population size.

    PubMed

    Bromham, Lindell; Hua, Xia; Fitzpatrick, Thomas G; Greenhill, Simon J

    2015-02-17

    The effect of population size on patterns and rates of language evolution is controversial. Do languages with larger speaker populations change faster due to a greater capacity for innovation, or do smaller populations change faster due to more efficient diffusion of innovations? Do smaller populations suffer greater loss of language elements through founder effects or drift, or do languages with more speakers lose features due to a process of simplification? Revealing the influence of population size on the tempo and mode of language evolution not only will clarify underlying mechanisms of language change but also has practical implications for the way that language data are used to reconstruct the history of human cultures. Here, we provide, to our knowledge, the first empirical, statistically robust test of the influence of population size on rates of language evolution, controlling for the evolutionary history of the populations and formally comparing the fit of different models of language evolution. We compare rates of gain and loss of cognate words for basic vocabulary in Polynesian languages, an ideal test case with a well-defined history. We demonstrate that larger populations have higher rates of gain of new words whereas smaller populations have higher rates of word loss. These results show that demographic factors can influence rates of language evolution and that rates of gain and loss are affected differently. These findings are strikingly consistent with general predictions of evolutionary models. PMID:25646448

  11. Rate of language evolution is affected by population size

    PubMed Central

    Bromham, Lindell; Hua, Xia; Fitzpatrick, Thomas G.; Greenhill, Simon J.

    2015-01-01

    The effect of population size on patterns and rates of language evolution is controversial. Do languages with larger speaker populations change faster due to a greater capacity for innovation, or do smaller populations change faster due to more efficient diffusion of innovations? Do smaller populations suffer greater loss of language elements through founder effects or drift, or do languages with more speakers lose features due to a process of simplification? Revealing the influence of population size on the tempo and mode of language evolution not only will clarify underlying mechanisms of language change but also has practical implications for the way that language data are used to reconstruct the history of human cultures. Here, we provide, to our knowledge, the first empirical, statistically robust test of the influence of population size on rates of language evolution, controlling for the evolutionary history of the populations and formally comparing the fit of different models of language evolution. We compare rates of gain and loss of cognate words for basic vocabulary in Polynesian languages, an ideal test case with a well-defined history. We demonstrate that larger populations have higher rates of gain of new words whereas smaller populations have higher rates of word loss. These results show that demographic factors can influence rates of language evolution and that rates of gain and loss are affected differently. These findings are strikingly consistent with general predictions of evolutionary models. PMID:25646448

  12. Stability, complexity and robustness in population dynamics.

    PubMed

    Demongeot, J; Hazgui, H; Ben Amor, H; Waku, J

    2014-09-01

    The problem of stability in population dynamics concerns many domains of application in demography, biology, mechanics and mathematics. The problem is highly generic and independent of the population considered (human, animals, molecules,…). We give in this paper some examples of population dynamics concerning nucleic acids interacting through direct nucleic binding with small or cyclic RNAs acting on mRNAs or tRNAs as translation factors or through protein complexes expressed by genes and linked to DNA as transcription factors. The networks made of these interactions between nucleic acids (considered respectively as edges and nodes of their interaction graph) are complex, but exhibit simple emergent asymptotic behaviours, when time tends to infinity, called attractors. We show that the quantity called attractor entropy plays a crucial role in the study of the stability and robustness of such genetic networks. PMID:25107273

  13. Genetic diversity affects the strength of population regulation in a marine fish.

    PubMed

    Johnson, D W; Freiwald, J; Bernardi, G

    2016-03-01

    Variation is an essential feature of biological populations, yet much of ecological theory treats individuals as though they are identical. This simplifying assumption is often justified by the perception that variation among individuals does not have significant effects on the dynamics of whole populations. However, this perception may be skewed by a historic focus on studying single populations. A true evaluation of the extent to which among-individual variation affects the dynamics of populations requires the study of multiple populations. In this study, we examined variation in the dynamics of populations of a live-bearing, marine fish (black surfperch; Embiotoca jacksoni). In collaboration with an organization of citizen scientists (Reef Check California), we were able to examine the dynamics of eight populations that were distributed throughout approximately 700 km of coastline, a distance that encompasses much of this species' range. We hypothesized that genetic variation within a local population would be related to the intensity of competition and to the strength of population regulation. To test this hypothesis, we examined whether genetic diversity (measured by the diversity of mitochondrial DNA haplotypes) was related to the strength of population regulation. Low-diversity populations experienced strong density dependence in population growth rates and population sizes were regulated much more tightly than they were in high-diversity populations. Mechanisms that contributed to this pattern include links between genetic diversity, habitat use, and spatial crowding. On average, low-diversity populations used less of the available habitat and exhibited greater spatial clustering (and more intense competition) for a given level of density (measured at the scale of the reef). Although the populations we studied also varied with respect to exogenous characteristics (habitat complexity, densities of predators, and interspecific competitors), none of these

  14. Dynamical inference of hidden biological populations

    NASA Astrophysics Data System (ADS)

    Luchinsky, D. G.; Smelyanskiy, V. N.; Millonas, M.; McClintock, P. V. E.

    2008-10-01

    Population fluctuations in a predator-prey system are analyzed for the case where the number of prey could be determined, subject to measurement noise, but the number of predators was unknown. The problem of how to infer the unmeasured predator dynamics, as well as the model parameters, is addressed. Two solutions are suggested. In the first of these, measurement noise and the dynamical noise in the equation for predator population are neglected; the problem is reduced to a one-dimensional case, and a Bayesian dynamical inference algorithm is employed to reconstruct the model parameters. In the second solution a full-scale Markov Chain Monte Carlo simulation is used to infer both the unknown predator trajectory, and also the model parameters, using the one-dimensional solution as an initial guess.

  15. Dynamics of newly established elk populations

    USGS Publications Warehouse

    Sargeant, G.A.; Oehler, M.W., Sr.

    2007-01-01

    The dynamics of newly established elk (Cervus elaphus) populations can provide insights about maximum sustainable rates of reproduction, survival, and increase. However, data used to estimate rates of increase typically have been limited to counts and rarely have included complementary estimates of vital rates. Complexities of population dynamics cannot be understood without considering population processes as well as population states. We estimated pregnancy rates, survival rates, age ratios, and sex ratios for reintroduced elk at Theodore Roosevelt National Park, North Dakota, USA; combined vital rates in a population projection model; and compared model projections with observed elk numbers and population ratios. Pregnancy rates in January (early in the second trimester of pregnancy) averaged 54.1% (SE = 5.4%) for subadults and 91.0% (SE = 1.7%) for adults, and 91.6% of pregnancies resulted in recruitment at 8 months. Annual survival rates of adult females averaged 0.96 (95% CI = 0.94-0.98) with hunting included and 0.99 (95% CI = 0.97-0.99) with hunting excluded from calculations. Our fitted model explained 99.8% of past variation in population estimates and represents a useful new tool for short-term management planning. Although we found no evidence of temporal variation in vital rates, variation in population composition caused substantial variation in projected rates of increase (??=1.20-1.36). Restoring documented hunter harvests and removals of elk by the National Park Service led to a potential rate of ?? = 1.26. Greater rates of increase substantiated elsewhere were within the expected range of chance variation, given our model and estimates of vital rates. Rates of increase realized by small elk populations are too variable to support inferences about habitat quality or density dependence.

  16. FACTORS ADVERSELY AFFECTING AMPHIBIAN POPULATIONS IN THE US

    EPA Science Inventory

    Factors known or suspected to be adversely affecting native amphibian populations in the US were identified using information from species accounts written in a standardized format by multiple authors in a forthcoming book. Specific adverse factors were identified for 53 (58%) of...

  17. Singularities affect dynamics of learning in neuromanifolds.

    PubMed

    Amari, Shun-ichi; Park, Hyeyoung; Ozeki, Tomoko

    2006-05-01

    The parameter spaces of hierarchical systems such as multilayer perceptrons include singularities due to the symmetry and degeneration of hidden units. A parameter space forms a geometrical manifold, called the neuromanifold in the case of neural networks. Such a model is identified with a statistical model, and a Riemannian metric is given by the Fisher information matrix. However, the matrix degenerates at singularities. Such a singular structure is ubiquitous not only in multilayer perceptrons but also in the gaussian mixture probability densities, ARMA time-series model, and many other cases. The standard statistical paradigm of the Cramér-Rao theorem does not hold, and the singularity gives rise to strange behaviors in parameter estimation, hypothesis testing, Bayesian inference, model selection, and in particular, the dynamics of learning from examples. Prevailing theories so far have not paid much attention to the problem caused by singularity, relying only on ordinary statistical theories developed for regular (nonsingular) models. Only recently have researchers remarked on the effects of singularity, and theories are now being developed. This article gives an overview of the phenomena caused by the singularities of statistical manifolds related to multilayer perceptrons and gaussian mixtures. We demonstrate our recent results on these problems. Simple toy models are also used to show explicit solutions. We explain that the maximum likelihood estimator is no longer subject to the gaussian distribution even asymptotically, because the Fisher information matrix degenerates, that the model selection criteria such as AIC, BIC, and MDL fail to hold in these models, that a smooth Bayesian prior becomes singular in such models, and that the trajectories of dynamics of learning are strongly affected by the singularity, causing plateaus or slow manifolds in the parameter space. The natural gradient method is shown to perform well because it takes the singular

  18. 75 FR 51273 - Expanded Human Immunodeficiency Virus (HIV) Testing for Disproportionately Affected Populations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-19

    ... (HIV) Testing for Disproportionately Affected Populations AGENCY: Centers for Disease Control and... Affected Populations''. Additional funding from the Patient Protection and Affordable Care Act has been... (HIV) Testing for Disproportionately Affected Populations'' to make awards to state and county...

  19. Can coyotes affect deer populations in Southeastern North America?

    SciTech Connect

    Kilgo, J., C.; Ray, H., Scott; Ruth, Charles; Miller, Karl, V.

    2010-07-01

    ABSTRACT The coyote (Canis latrans) is a recent addition to the fauna of eastern North America, and in many areas coyote populations have been established for only a decade or two. Although coyotes are known predators of white-tailed deer (Odocoileus virginianus) in their historic range, effects this new predator may have on eastern deer populations have received little attention. We speculated that in the southeastern United States, coyotes may be affecting deer recruitment, and we present 5 lines of evidence that suggest this possibility. First, the statewide deer population in South Carolina has declined coincident with the establishment and increase in the coyote population. Second, data sets from the Savannah River Site (SRS) in South Carolina indicate a new mortality source affecting the deer population concurrent with the increase in coyotes. Third, an index of deer recruitment at SRS declined during the period of increase in coyotes. Fourth, food habits data from SRS indicate that fawns are an important food item for coyotes during summer. Finally, recent research from Alabama documented significant coyote predation on fawns there. Although this evidence does not establish cause and effect between coyotes and observed declines in deer recruitment, we argue that additional research should proactively address this topic in the region. We identified several important questions on the nature of the deer–coyote relationship in the East.

  20. Population mixture model for nonlinear telomere dynamics

    NASA Astrophysics Data System (ADS)

    Itzkovitz, Shalev; Shlush, Liran I.; Gluck, Dan; Skorecki, Karl

    2008-12-01

    Telomeres are DNA repeats protecting chromosomal ends which shorten with each cell division, eventually leading to cessation of cell growth. We present a population mixture model that predicts an exponential decrease in telomere length with time. We analytically solve the dynamics of the telomere length distribution. The model provides an excellent fit to available telomere data and accounts for the previously unexplained observation of telomere elongation following stress and bone marrow transplantation, thereby providing insight into the nature of the telomere clock.

  1. Galactic civilizations - Population dynamics and interstellar diffusion

    NASA Technical Reports Server (NTRS)

    Newman, W. I.; Sagan, C.

    1981-01-01

    A model is developed of the interstellar diffusion of galactic civilizations which takes into account the population dynamics of such civilizations. The problem is formulated in terms of potential theory, with a family of nonlinear partial differential and difference equations specifying population growth and diffusion for an organism with advantageous genes that undergoes random dispersal while increasing in population locally, and a population at zero population growth. In the case of nonlinear diffusion with growth and saturation, it is found that the colonization wavefront from the nearest independently arisen galactic civilization can have reached the earth only if its lifetime exceeds 2.6 million years, or 20 million years if discretization can be neglected. For zero population growth, the corresponding lifetime is 13 billion years. It is concluded that the earth is uncolonized not because interstellar spacefaring civilizations are rare, but because there are too many worlds to be colonized in the plausible colonization lifetime of nearby civilizations, and that there exist no very old galactic civilizations with a consistent policy of the conquest of inhabited worlds.

  2. Evolutionary Dynamics and Diversity in Microbial Populations

    NASA Astrophysics Data System (ADS)

    Thompson, Joel; Fisher, Daniel

    2013-03-01

    Diseases such as flu and cancer adapt at an astonishing rate. In large part, viruses and cancers are so difficult to prevent because they are continually evolving. Controlling such ``evolutionary diseases'' requires a better understanding of the underlying evolutionary dynamics. It is conventionally assumed that adaptive mutations are rare and therefore will occur and sweep through the population in succession. Recent experiments using modern sequencing technologies have illuminated the many ways in which real population sequence data does not conform to the predictions of conventional theory. We consider a very simple model of asexual evolution and perform simulations in a range of parameters thought to be relevant for microbes and cancer. Simulation results reveal complex evolutionary dynamics typified by competition between lineages with different sets of adaptive mutations. This dynamical process leads to a distribution of mutant gene frequencies different than expected under the conventional assumption that adaptive mutations are rare. Simulated gene frequencies share several conspicuous features with data collected from laboratory-evolved yeast and the worldwide population of influenza.

  3. Population clocks: motor timing with neural dynamics

    PubMed Central

    Buonomano, Dean V.; Laje, Rodrigo

    2010-01-01

    An understanding of sensory and motor processing will require elucidation of the mechanisms by which the brain tells time. Open questions relate to whether timing relies on dedicated or intrinsic mechanisms and whether distinct mechanisms underlie timing across scales and modalities. Although experimental and theoretical studies support the notion that neural circuits are intrinsically capable of sensory timing on short scales, few general models of motor timing have been proposed. For one class of models, population clocks, it is proposed that time is encoded in the time-varying patterns of activity of a population of neurons. We argue that population clocks emerge from the internal dynamics of recurrently connected networks, are biologically realistic and account for many aspects of motor timing. PMID:20889368

  4. Dynamic Artificial Neural Networks with Affective Systems

    PubMed Central

    Schuman, Catherine D.; Birdwell, J. Douglas

    2013-01-01

    Artificial neural networks (ANNs) are processors that are trained to perform particular tasks. We couple a computational ANN with a simulated affective system in order to explore the interaction between the two. In particular, we design a simple affective system that adjusts the threshold values in the neurons of our ANN. The aim of this paper is to demonstrate that this simple affective system can control the firing rate of the ensemble of neurons in the ANN, as well as to explore the coupling between the affective system and the processes of long term potentiation (LTP) and long term depression (LTD), and the effect of the parameters of the affective system on its performance. We apply our networks with affective systems to a simple pole balancing example and briefly discuss the effect of affective systems on network performance. PMID:24303015

  5. Computer Assisted Instruction of Population Dynamics: A New Approach to Population Education. Report No. T-19.

    ERIC Educational Resources Information Center

    Klaff, Vivian; Handler, Paul

    Available on the University of Illinois PLATO IV Computer system, the Population Dynamic Group computer-aided instruction program for teaching population dynamics is described and explained. The computer-generated visual graphics enable fast and intuitive understanding of the dynamics of population and of the concepts and data of population. The…

  6. Adaptive dynamics for physiologically structured population models.

    PubMed

    Durinx, Michel; Metz, J A J Hans; Meszéna, Géza

    2008-05-01

    We develop a systematic toolbox for analyzing the adaptive dynamics of multidimensional traits in physiologically structured population models with point equilibria (sensu Dieckmann et al. in Theor. Popul. Biol. 63:309-338, 2003). Firstly, we show how the canonical equation of adaptive dynamics (Dieckmann and Law in J. Math. Biol. 34:579-612, 1996), an approximation for the rate of evolutionary change in characters under directional selection, can be extended so as to apply to general physiologically structured population models with multiple birth states. Secondly, we show that the invasion fitness function (up to and including second order terms, in the distances of the trait vectors to the singularity) for a community of N coexisting types near an evolutionarily singular point has a rational form, which is model-independent in the following sense: the form depends on the strategies of the residents and the invader, and on the second order partial derivatives of the one-resident fitness function at the singular point. This normal form holds for Lotka-Volterra models as well as for physiologically structured population models with multiple birth states, in discrete as well as continuous time and can thus be considered universal for the evolutionary dynamics in the neighbourhood of singular points. Only in the case of one-dimensional trait spaces or when N = 1 can the normal form be reduced to a Taylor polynomial. Lastly we show, in the form of a stylized recipe, how these results can be combined into a systematic approach for the analysis of the (large) class of evolutionary models that satisfy the above restrictions. PMID:17943289

  7. Building the bridge between animal movement and population dynamics

    PubMed Central

    Morales, Juan M.; Moorcroft, Paul R.; Matthiopoulos, Jason; Frair, Jacqueline L.; Kie, John G.; Powell, Roger A.; Merrill, Evelyn H.; Haydon, Daniel T.

    2010-01-01

    While the mechanistic links between animal movement and population dynamics are ecologically obvious, it is much less clear when knowledge of animal movement is a prerequisite for understanding and predicting population dynamics. GPS and other technologies enable detailed tracking of animal location concurrently with acquisition of landscape data and information on individual physiology. These tools can be used to refine our understanding of the mechanistic links between behaviour and individual condition through ‘spatially informed’ movement models where time allocation to different behaviours affects individual survival and reproduction. For some species, socially informed models that address the movements and average fitness of differently sized groups and how they are affected by fission–fusion processes at relevant temporal scales are required. Furthermore, as most animals revisit some places and avoid others based on their previous experiences, we foresee the incorporation of long-term memory and intention in movement models. The way animals move has important consequences for the degree of mixing that we expect to find both within a population and between individuals of different species. The mixing rate dictates the level of detail required by models to capture the influence of heterogeneity and the dynamics of intra- and interspecific interaction. PMID:20566505

  8. Population Code Dynamics in Categorical Perception

    PubMed Central

    Tajima, Chihiro I.; Tajima, Satohiro; Koida, Kowa; Komatsu, Hidehiko; Aihara, Kazuyuki; Suzuki, Hideyuki

    2016-01-01

    Categorical perception is a ubiquitous function in sensory information processing, and is reported to have important influences on the recognition of presented and/or memorized stimuli. However, such complex interactions among categorical perception and other aspects of sensory processing have not been explained well in a unified manner. Here, we propose a recurrent neural network model to process categorical information of stimuli, which approximately realizes a hierarchical Bayesian estimation on stimuli. The model accounts for a wide variety of neurophysiological and cognitive phenomena in a consistent framework. In particular, the reported complexity of categorical effects, including (i) task-dependent modulation of neural response, (ii) clustering of neural population representation, (iii) temporal evolution of perceptual color memory, and (iv) a non-uniform discrimination threshold, are explained as different aspects of a single model. Moreover, we directly examine key model behaviors in the monkey visual cortex by analyzing neural population dynamics during categorization and discrimination of color stimuli. We find that the categorical task causes temporally-evolving biases in the neuronal population representations toward the focal colors, which supports the proposed model. These results suggest that categorical perception can be achieved by recurrent neural dynamics that approximates optimal probabilistic inference in the changing environment. PMID:26935275

  9. Evolutionary dynamics in finite populations with zealots.

    PubMed

    Nakajima, Yohei; Masuda, Naoki

    2015-02-01

    We investigate evolutionary dynamics of two-strategy matrix games with zealots in finite populations. Zealots are assumed to take either strategy regardless of the fitness. When the strategy selected by the zealots is the same, the fixation of the strategy selected by the zealots is a trivial outcome. We study fixation time in this scenario. We show that the fixation time is divided into three main regimes, in one of which the fixation time is short, and in the other two the fixation time is exponentially long in terms of the population size. Different from the case without zealots, there is a threshold selection intensity below which the fixation is fast for an arbitrary payoff matrix. We illustrate our results with examples of various social dilemma games. PMID:24610380

  10. Assessing the dynamics of wild populations

    SciTech Connect

    Eberhardt, L.L.

    1985-01-01

    Lotka's equations summarizing population dynamics can be approximated by functional models of the survivorship and reproductive curves, incorporating three stages of survival and reproduction, respectively. An abbreviated form uses a single reproductive parameter and two survival values. Survivorship and reproductive curves were fitted to data on northern fur seals (Callorhinus ursinus), domestic and feral sheep, white-tailed deer (Odocoileus virginianus), grizzly bears (Ursus arctos), African buffalo (Syncerus caffer), free-ranging horses, and fin whales (Balaenoptera physalus). Data for 10 species suggest a useful relationship between senescence parameters. A bias due to senescence may lead to serious underestimation of survival rates. Observed annual rates of increase of 18-20% for feral horses, 16% for southern fur seals (Arctocephalus gazella), and 60% for white-tailed deer are compatible with observed population parameters. 43 references, 11 figures, 3 tables.

  11. Noise-induced effects in population dynamics

    NASA Astrophysics Data System (ADS)

    Spagnolo, Bernardo; Cirone, Markus; La Barbera, Antonino; de Pasquale, Ferdinando

    2002-03-01

    We investigate the role of noise in the nonlinear relaxation of two ecosystems described by generalized Lotka-Volterra equations in the presence of multiplicative noise. Specifically we study two cases: (i) an ecosystem with two interacting species in the presence of periodic driving; (ii) an ecosystem with a great number of interacting species with random interaction matrix. We analyse the interplay between noise and periodic modulation for case (i) and the role of the noise in the transient dynamics of the ecosystem in the presence of an absorbing barrier in case (ii). We find that the presence of noise is responsible for the generation of temporal oscillations and for the appearance of spatial patterns in the first case. In the other case we obtain the asymptotic behaviour of the time average of the ith population and discuss the effect of the noise on the probability distributions of the population and of the local field.

  12. Monitoring microbial population dynamics at low densities

    NASA Astrophysics Data System (ADS)

    Julou, Thomas; Desprat, Nicolas; Bensimon, David; Croquette, Vincent

    2012-07-01

    We propose a new and simple method for the measurement of microbial concentrations in highly diluted cultures. This method is based on an analysis of the intensity fluctuations of light scattered by microbial cells under laser illumination. Two possible measurement strategies are identified and compared using simulations and measurements of the concentration of gold nanoparticles. Based on this comparison, we show that the concentration of Escherichia coli and Saccharomyces cerevisiae cultures can be easily measured in situ across a concentration range that spans five orders of magnitude. The lowest measurable concentration is three orders of magnitude (1000×) smaller than in current optical density measurements. We show further that this method can also be used to measure the concentration of fluorescent microbial cells. In practice, this new method is well suited to monitor the dynamics of population growth at early colonization of a liquid culture medium. The dynamic data thus obtained are particularly relevant for microbial ecology studies.

  13. Patterns and localized structures in population dynamics

    NASA Astrophysics Data System (ADS)

    Clerc, M. G.; Escaff, D.; Kenkre, V. M.

    2005-11-01

    Patterns, fronts, and localized structures of a prototypical model for population dynamics interaction are studied. The physical content of the model is the coexistence of a simple random walk for the motion of the individuals with a nonlinearity in the competitive struggle for resources which simultaneously stresses the Allee effect and interaction at a distance. Mathematically, the model is variational and exhibits coexistence between different stable extended states. Solutions are obtained, the phase diagram is constructed, and the emergence of localized structures is investigated.

  14. A population dynamics approach to biological aging

    NASA Astrophysics Data System (ADS)

    de Almeida, R. M. C.

    A dynamical model for aging in biological population is discussed where asexual reproduction is considered. The maximum life span is inherited from parent to offspring with some random mutations described by a transition matrix, and the fertile period begins at a defined age R. The intra species competition is modeled through a Verhulst-like factor. Discrete time evolution equations are iterated and the transient and asymptotic solutions are obtained. When only bad mutations are taken into account, the stationary solutions are obtained analytically. The results are applied to the Penna model.

  15. Protein crowding affects hydration structure and dynamics

    PubMed Central

    Harada, Ryuhei; Sugita, Yuji; Feig, Michael

    2012-01-01

    The effect of protein crowding on the structure and dynamics of water was examined from explicit solvent molecular dynamics simulations of a series of protein G and protein G/villin systems at different protein concentrations. Hydration structure was analyzed in terms of radial distribution functions, three-dimensional hydration sites, and preservation of tetrahedral coordination. Analysis of hydration dynamics focused on self-diffusion rates and dielectric constants as a function of crowding. The results show significant changes in both structure and dynamics of water under highly crowded conditions. The structure of water is altered mostly beyond the first solvation shell. Diffusion rates and dielectric constants are significantly reduced following linear trends as a function of crowding reflecting highly constrained water in crowded environments. The reduced dynamics of diffusion is expected to be strongly related to hydrodynamic properties of crowded cellular environments while the reduced dielectric constant under crowded conditions has implications for the stability of biomolecules in crowded environments. The results from this study suggest a prescription for modeling solvation in simulations of cellular environments. PMID:22352398

  16. [Population dynamics and development in the Caribbean].

    PubMed

    Boland, B

    1995-12-01

    The impact is examined of socioeconomic factors on Caribbean population dynamics. This work begins by describing the socioeconomic context of the late 1980s and early 1990s, under the influence of the economic changes and crises of the 1980s. The small size, openness, dependency, and lack of diversification of the Caribbean economies have made them vulnerable to external pressures. The Bahamas and Belize had economic growth rates exceeding 5% annually during 1981-90, but most of the countries had low or negative growth. Unemployment, poverty, the structural adjustment measures adopted in the mid-1980s, and declines in social spending exacerbated general economic conditions. In broad terms, the population situation of the Caribbean is marked by diversity of sizes and growth rates. A few countries oriented toward services and tourism had demographic growth rates exceeding 3%, while at least 7 had almost no growth or negative growth. Population growth rates reflected different combinations of natural increase and migration. Crude death rates ranged from around 5/1000 to 11/1000, except in Haiti, and all countries of the region except Haiti had life expectancies of 70 years or higher. Despite fertility decline, the average crude birth rate was still relatively high at 26/1000, and the rate of natural increase was 1.8% annually for the region. Nearly half of the regional population was under 15 or over 65 years old. The body of this work provides greater detail on mortality patterns, variations by sex, infant mortality, causes of death, and implications for policy. The discussion of fertility includes general patterns and trends, age specific fertility rates, contraceptive prevalence, levels of adolescent fertility and age factors in adolescent sexual behavior, characteristics of adolescent unions, contraceptive usage, health and social consequences of adolescent childbearing, and the search for solutions. The final section describes the magnitude and causes of

  17. A new ODE tumor growth modeling based on tumor population dynamics

    SciTech Connect

    Oroji, Amin; Omar, Mohd bin; Yarahmadian, Shantia

    2015-10-22

    In this paper a new mathematical model for the population of tumor growth treated by radiation is proposed. The cells dynamics population in each state and the dynamics of whole tumor population are studied. Furthermore, a new definition of tumor lifespan is presented. Finally, the effects of two main parameters, treatment parameter (q), and repair mechanism parameter (r) on tumor lifespan are probed, and it is showed that the change in treatment parameter (q) highly affects the tumor lifespan.

  18. A new ODE tumor growth modeling based on tumor population dynamics

    NASA Astrophysics Data System (ADS)

    Oroji, Amin; Omar, Mohd bin; Yarahmadian, Shantia

    2015-10-01

    In this paper a new mathematical model for the population of tumor growth treated by radiation is proposed. The cells dynamics population in each state and the dynamics of whole tumor population are studied. Furthermore, a new definition of tumor lifespan is presented. Finally, the effects of two main parameters, treatment parameter (q), and repair mechanism parameter (r) on tumor lifespan are probed, and it is showed that the change in treatment parameter (q) highly affects the tumor lifespan.

  19. Stochasticity and Determinism: How Density-Independent and Density-Dependent Processes Affect Population Variability

    PubMed Central

    Ohlberger, Jan; Rogers, Lauren A.; Stenseth, Nils Chr.

    2014-01-01

    A persistent debate in population ecology concerns the relative importance of environmental stochasticity and density dependence in determining variability in adult year-class strength, which contributes to future reproduction as well as potential yield in exploited populations. Apart from the strength of the processes, the timing of density regulation may affect how stochastic variation, for instance through climate, translates into changes in adult abundance. In this study, we develop a life-cycle model for the population dynamics of a large marine fish population, Northeast Arctic cod, to disentangle the effects of density-independent and density-dependent processes on early life-stages, and to quantify the strength of compensatory density dependence in the population. The model incorporates information from scientific surveys and commercial harvest, and dynamically links multiple effects of intrinsic and extrinsic factors on all life-stages, from eggs to spawners. Using a state-space approach we account for observation error and stochasticity in the population dynamics. Our findings highlight the importance of density-dependent survival in juveniles, indicating that this period of the life cycle largely determines the compensatory capacity of the population. Density regulation at the juvenile life-stage dampens the impact of stochastic processes operating earlier in life such as environmental impacts on the production of eggs and climate-dependent survival of larvae. The timing of stochastic versus regulatory processes thus plays a crucial role in determining variability in adult abundance. Quantifying the contribution of environmental stochasticity and compensatory mechanisms in determining population abundance is essential for assessing population responses to climate change and exploitation by humans. PMID:24893001

  20. Stochasticity and determinism: how density-independent and density-dependent processes affect population variability.

    PubMed

    Ohlberger, Jan; Rogers, Lauren A; Stenseth, Nils Chr

    2014-01-01

    A persistent debate in population ecology concerns the relative importance of environmental stochasticity and density dependence in determining variability in adult year-class strength, which contributes to future reproduction as well as potential yield in exploited populations. Apart from the strength of the processes, the timing of density regulation may affect how stochastic variation, for instance through climate, translates into changes in adult abundance. In this study, we develop a life-cycle model for the population dynamics of a large marine fish population, Northeast Arctic cod, to disentangle the effects of density-independent and density-dependent processes on early life-stages, and to quantify the strength of compensatory density dependence in the population. The model incorporates information from scientific surveys and commercial harvest, and dynamically links multiple effects of intrinsic and extrinsic factors on all life-stages, from eggs to spawners. Using a state-space approach we account for observation error and stochasticity in the population dynamics. Our findings highlight the importance of density-dependent survival in juveniles, indicating that this period of the life cycle largely determines the compensatory capacity of the population. Density regulation at the juvenile life-stage dampens the impact of stochastic processes operating earlier in life such as environmental impacts on the production of eggs and climate-dependent survival of larvae. The timing of stochastic versus regulatory processes thus plays a crucial role in determining variability in adult abundance. Quantifying the contribution of environmental stochasticity and compensatory mechanisms in determining population abundance is essential for assessing population responses to climate change and exploitation by humans. PMID:24893001

  1. Effects of spatial structure of population size on the population dynamics of barnacles across their elevational range.

    PubMed

    Fukaya, Keiichi; Okuda, Takehiro; Nakaoka, Masahiro; Noda, Takashi

    2014-11-01

    Explanations for why population dynamics vary across the range of a species reflect two contrasting hypotheses: (i) temporal variability of populations is larger in the centre of the range compared to the margins because overcompensatory density dependence destabilizes population dynamics and (ii) population variability is larger near the margins, where populations are more susceptible to environmental fluctuations. In both of these hypotheses, positions within the range are assumed to affect population variability. In contrast, the fact that population variability is often related to mean population size implies that the spatial structure of the population size within the range of a species may also be a useful predictor of the spatial variation in temporal variability of population size over the range of the species. To explore how population temporal variability varies spatially and the underlying processes responsible for the spatial variation, we focused on the intertidal barnacle Chthamalus dalli and examined differences in its population dynamics along the tidal levels it inhabits. Changes in coverage of barnacle populations were monitored for 10.5 years at 25 plots spanning the elevational range of this species. Data were analysed by fitting a population dynamics model to estimate the effects of density-dependent and density-independent processes on population growth. We also examined the temporal mean-variance relationship of population size with parameters estimated from the population dynamics model. We found that the relative variability of populations tended to increase from the centre of the elevational range towards the margins because of an increase in the magnitude of stochastic fluctuations of growth rates. Thus, our results supported hypothesis (2). We also found that spatial variations in temporal population variability were well characterized by Taylor's power law, the relative population variability being inversely related to the mean

  2. Dynamic analysis of a parasite population model

    NASA Astrophysics Data System (ADS)

    Sibona, G. J.; Condat, C. A.

    2002-03-01

    We study the dynamics of a model that describes the competitive interaction between an invading species (a parasite) and its antibodies in an living being. This model was recently used to examine the dynamical competition between Tripanosoma cruzi and its antibodies during the acute phase of Chagas' disease. Depending on the antibody properties, the model yields three types of outcomes, corresponding, respectively, to healing, chronic disease, and host death. Here, we study the dynamics of the parasite-antibody interaction with the help of simulations, obtaining phase trajectories and phase diagrams for the system. We show that, under certain conditions, the size of the parasite inoculation can be crucial for the infection outcome and that a retardation in the stimulated production of an antibody species may result in the parasite gaining a definitive advantage. We also find a criterion for the relative sizes of the parameters that are required if parasite-generated decoys are indeed to help the invasion. Decoys may also induce a qualitatively different outcome: a limit cycle for the antibody-parasite population phase trajectories.

  3. Osmolyte cooperation affects turgor dynamics in plants.

    PubMed

    Argiolas, Alfredo; Puleo, Gian Luigi; Sinibaldi, Edoardo; Mazzolai, Barbara

    2016-01-01

    Scientists have identified turgor-based actuation as a fundamental mechanism in plant movements. Plant cell turgor is generated by water influx due to the osmolyte concentration gradient through the cell wall and the plasma membrane behaving as an osmotic barrier. Previous studies have focused on turgor modulation with respect to potassium chloride (KCl) concentration changes, although KCl is not efficiently retained in the cell, and many other compounds, including L-glutamine (L-Gln) and D-glucose (D-Glc), are present in the cytosol. In fact, the contributions of other osmolytes to turgor dynamics remain to be elucidated. Here, we show the association of osmolytes and their consequent cooperative effects on the time-dependent turgor profile generated in a model cytosol consisting of KCl, D-Glc and L-Gln at experimentally measured plant motor/generic cell concentrations and at modified concentrations. We demonstrate the influence and association of the osmolytes using osmometry and NMR measurements. We also show, using a plant cell-inspired device we previously developed, that osmolyte complexes, rather than single osmolytes, permit to obtain higher turgor required by plant movements. We provide quantitative cues for deeper investigations of osmolyte transport for plant movement, and reveal the possibility of developing osmotic actuators exploiting a dynamically varying concentration of osmolytes. PMID:27445173

  4. Osmolyte cooperation affects turgor dynamics in plants

    PubMed Central

    Argiolas, Alfredo; Puleo, Gian Luigi; Sinibaldi, Edoardo; Mazzolai, Barbara

    2016-01-01

    Scientists have identified turgor-based actuation as a fundamental mechanism in plant movements. Plant cell turgor is generated by water influx due to the osmolyte concentration gradient through the cell wall and the plasma membrane behaving as an osmotic barrier. Previous studies have focused on turgor modulation with respect to potassium chloride (KCl) concentration changes, although KCl is not efficiently retained in the cell, and many other compounds, including L-glutamine (L-Gln) and D-glucose (D-Glc), are present in the cytosol. In fact, the contributions of other osmolytes to turgor dynamics remain to be elucidated. Here, we show the association of osmolytes and their consequent cooperative effects on the time-dependent turgor profile generated in a model cytosol consisting of KCl, D-Glc and L-Gln at experimentally measured plant motor/generic cell concentrations and at modified concentrations. We demonstrate the influence and association of the osmolytes using osmometry and NMR measurements. We also show, using a plant cell-inspired device we previously developed, that osmolyte complexes, rather than single osmolytes, permit to obtain higher turgor required by plant movements. We provide quantitative cues for deeper investigations of osmolyte transport for plant movement, and reveal the possibility of developing osmotic actuators exploiting a dynamically varying concentration of osmolytes. PMID:27445173

  5. Osmolyte cooperation affects turgor dynamics in plants

    NASA Astrophysics Data System (ADS)

    Argiolas, Alfredo; Puleo, Gian Luigi; Sinibaldi, Edoardo; Mazzolai, Barbara

    2016-07-01

    Scientists have identified turgor-based actuation as a fundamental mechanism in plant movements. Plant cell turgor is generated by water influx due to the osmolyte concentration gradient through the cell wall and the plasma membrane behaving as an osmotic barrier. Previous studies have focused on turgor modulation with respect to potassium chloride (KCl) concentration changes, although KCl is not efficiently retained in the cell, and many other compounds, including L-glutamine (L-Gln) and D-glucose (D-Glc), are present in the cytosol. In fact, the contributions of other osmolytes to turgor dynamics remain to be elucidated. Here, we show the association of osmolytes and their consequent cooperative effects on the time-dependent turgor profile generated in a model cytosol consisting of KCl, D-Glc and L-Gln at experimentally measured plant motor/generic cell concentrations and at modified concentrations. We demonstrate the influence and association of the osmolytes using osmometry and NMR measurements. We also show, using a plant cell-inspired device we previously developed, that osmolyte complexes, rather than single osmolytes, permit to obtain higher turgor required by plant movements. We provide quantitative cues for deeper investigations of osmolyte transport for plant movement, and reveal the possibility of developing osmotic actuators exploiting a dynamically varying concentration of osmolytes.

  6. When Should Harvest Evolution Matter to Population Dynamics?

    PubMed

    Nusslé, Sébastien; Hendry, Andrew P; Carlson, Stephanie M

    2016-07-01

    The potential for evolution to influence fishery sustainability remains a controversial topic. We highlight new modeling research from Dunlop et al. that explores when and how fisheries-induced evolution matters for population dynamics, while also emphasizing transient dynamics in population growth and life history-dependent responses that influence population stability and resiliency. PMID:27095380

  7. Subjective quality of life in war-affected populations

    PubMed Central

    2013-01-01

    Background Exposure to traumatic war events may lead to a reduction in quality of life for many years. Research suggests that these impairments may be associated with posttraumatic stress symptoms; however, wars also have a profound impact on social conditions. Systematic studies utilising subjective quality of life (SQOL) measures are particularly rare and research in post-conflict settings is scarce. Whether social factors independently affect SQOL after war in addition to symptoms has not been explored in large scale studies. Method War-affected community samples were recruited through a random-walk technique in five Balkan countries and through registers and networking in three Western European countries. The interviews were carried out on average 8 years after the war in the Balkans. SQOL was assessed on Manchester Short Assessment of Quality of Life - MANSA. We explored the impact of war events, posttraumatic stress symptoms and post-war environment on SQOL. Results We interviewed 3313 Balkan residents and 854 refugees in Western Europe. The MANSA mean score was 4.8 (SD = 0.9) for the Balkan sample and 4.7 (SD = 0.9) for refugees. In both samples participants were explicitly dissatisfied with their employment and financial situation. Posttraumatic stress symptoms had a strong negative impact on SQOL. Traumatic war events were directly linked with lower SQOL in Balkan residents. The post-war environment influenced SQOL in both groups: unemployment was associated with lower SQOL and recent contacts with friends with higher SQOL. Experiencing more migration-related stressors was linked to poorer SQOL in refugees. Conclusion Both posttraumatic stress symptoms and aspects of the post-war environment independently influence SQOL in war-affected populations. Aid programmes to improve wellbeing following the traumatic war events should include both treatment of posttraumatic symptoms and social interventions. PMID:23819629

  8. Studies of dynamical processes affecting global climate

    SciTech Connect

    Keller, C.; Cooper, D.; Eichinger, W.

    1998-12-31

    This is the final report of a three-year, Laboratory Directed Research and Development project at the Los Alamos National Laboratory (LANL). The main objective was, by a combined theoretical and observational approach, to develop improved models of dynamic processes in the oceans and atmosphere and to incorporate them into large climate codes, chiefly in four main areas: numerical physics, chemistry, water vapor, and ocean-atmosphere interactions. Main areas of investigation included studies of: cloud parameterizations for global climate codes, Lidar and the planetary boundary layer, chemistry, climate variability using coupled ocean-atmospheric models, and numerical physical methods. This project employed a unique approach that included participation of a number of University of California faculty, postdoctoral fellows and graduate students who collaborated with Los Alamos research staff on specific tasks, thus greatly enhancing the research output. Overall accomplishments during the sensing of the atmospheric planetary were: (1) first two- and three-dimensional remote sensing of the atmospheric planetary boundary layer using Lidars, (2) modeling of 20-year cycle in both pressure and sea surface temperatures in North Pacific, (3) modeling of low frequency internal variability, (4) addition of aerosols to stratosphere to simulate Pinatubo effect on ozone, (5) development of fast, comprehensive chemistry in the troposphere for urban pollution studies, (6) new prognostic cloud parameterization in global atmospheric code remedied problems with North Pacific atmospheric circulation and excessive equatorial precipitation, (7) development of a unique aerosol analysis technique, the aerosol time-of-flight mass spectrometer (ATOFMS), which allows real-time analysis of the size and chemical composition of individual aerosol particles, and (8) numerical physics applying Approximate Inertial Manifolds to ocean circulation. 14 refs., 6 figs.

  9. Mammal population regulation, keystone processes and ecosystem dynamics.

    PubMed Central

    Sinclair, A R E

    2003-01-01

    The theory of regulation in animal populations is fundamental to understanding the dynamics of populations, the causes of mortality and how natural selection shapes the life history of species. In mammals, the great range in body size allows us to see how allometric relationships affect the mode of regulation. Resource limitation is the fundamental cause of regulation. Top-down limitation through predators is determined by four factors: (i). body size; (ii). the diversity of predators and prey in the system; (iii). whether prey are resident or migratory; and (iv). the presence of alternative prey for predators. Body size in mammals has two important consequences. First, mammals, particularly large species, can act as keystones that determine the diversity of an ecosystem. I show how keystone processes can, in principle, be measured using the example of the wildebeest in the Serengeti ecosystem. Second, mammals act as ecological landscapers by altering vegetation succession. Mammals alter physical structure, ecological function and species diversity in most terrestrial biomes. In general, there is a close interaction between allometry, population regulation, life history and ecosystem dynamics. These relationships are relevant to applied aspects of conservation and pest management. PMID:14561329

  10. Dynamics of Genome Rearrangement in Bacterial Populations

    PubMed Central

    Darling, Aaron E.; Miklós, István; Ragan, Mark A.

    2008-01-01

    first characterization of genome arrangement evolution in a bacterial population evolving outside laboratory conditions. Insight into the process of genomic rearrangement may further the understanding of pathogen population dynamics and selection on the architecture of circular bacterial chromosomes. PMID:18650965

  11. Population structure of Columbia spotted frogs (Rana luteiventris) is strongly affected by the landscape

    USGS Publications Warehouse

    Funk, W.C.; Blouin, M.S.; Corn, P.S.; Maxell, B.A.; Pilliod, D.S.; Amish, S.; Allendorf, F.W.

    2005-01-01

    Landscape features such as mountains, rivers, and ecological gradients may strongly affect patterns of dispersal and gene flow among populations and thereby shape population dynamics and evolutionary trajectories. The landscape may have a particularly strong effect on patterns of dispersal and gene flow in amphibians because amphibians are thought to have poor dispersal abilities. We examined genetic variation at six microsatellite loci in Columbia spotted frogs (Rana luteiventris) from 28 breeding ponds in western Montana and Idaho, USA, in order to investigate the effects of landscape structure on patterns of gene flow. We were particularly interested in addressing three questions: (i) do ridges act as barriers to gene flow? (ii) is gene flow restricted between low and high elevation ponds? (iii) does a pond equal a 'randomly mating population' (a deme)? We found that mountain ridges and elevational differences were associated with increased genetic differentiation among sites, suggesting that gene flow is restricted by ridges and elevation in this species. We also found that populations of Columbia spotted frogs generally include more than a single pond except for very isolated ponds. There was also evidence for surprisingly high levels of gene flow among low elevation sites separated by large distances. Moreover, genetic variation within populations was strongly negatively correlated with elevation, suggesting effective population sizes are much smaller at high elevation than at low elevation. Our results show that landscape features have a profound effect on patterns of genetic variation in Columbia spotted frogs.

  12. Dynamics of a feline retrovirus (FeLV) in host populations with variable spatial structure.

    PubMed Central

    Fromont, E; Pontier, D; Langlais, M

    1998-01-01

    The predictions of epidemic models are remarkably affected by the underlying assumptions concerning host population dynamics and the relation between host density and disease transmission. Furthermore, hypotheses underlying distinct models are rarely tested. Domestic cats (Felis catus) can be used to compare models and test their predictions, because cat populations show variable spatial structure that probably results in variability in the relation between density and disease transmission. Cat populations also exhibit various dynamics. We compare four epidemiological models of Feline Leukaemia Virus (FeLV). We use two different incidence terms, i.e. proportionate mixing and pseudo-mass action. Population dynamics are modelled as logistic or exponential growth. Compared with proportionate mixing, mass action incidence with logistic growth results in a threshold population size under which the virus cannot persist in the population. Exponential growth of host populations results in systems where FeLV persistence at a steady prevalence and depression of host population growth are biologically unlikely to occur. Predictions of our models account for presently available data on FeLV dynamics in various populations of cats. Thus, host population dynamics and spatial structure can be determinant parameters in parasite transmission, host population depression, and disease control. PMID:9684375

  13. Population dynamics of Yellowstone grizzly bears

    USGS Publications Warehouse

    Knight, Richard R.; Eberhardt, L.L.

    1985-01-01

    Data on the population of grizzly bears in the environs of Yellowstone National Park suggest that the population has not recovered from the reductions following closure of garbage dumps in 1970 and 1971, and may continue to decline. A computer simulation model indicates that the risk of extirpation over the next 30 yr is small, if the present population parameters continue to prevail. A review and further analysis of the available data brings out the importance of enhancing adult female survival if the population is to recover, and assesses various research needs. In particular, a reliable index of population trend is needed to augment available data on the population.

  14. DEMOGRAPHIC PROCESSES: POPULATION DYNAMICS IN HETEROGENEOUS LANDSCAPES

    EPA Science Inventory

    Few topics have attracted the attention of ecologists more than fluctuations in the numbers of plants and animals through time and their variation in abundance through space. nderstanding population fluctuations, and thus population conservation, requires understanding the links ...

  15. Consequences of parental care on population dynamics

    NASA Astrophysics Data System (ADS)

    de Oliveira, S. Moss

    1999-12-01

    We review the results obtained using the Penna model for biological ageing (T.J.P. Penna, J. Stat. Phys. 78 (1995) 1629) when different strategies of parental care are introduced into evolving populations. These results concern to: longevity of semelparous populations; self-organization of female menopause; the spatial distribution of the populations and finally, sexual fidelity.

  16. Experimental evidence of antiphase population dynamics in lasers

    SciTech Connect

    Cabrera, Eduardo; Calderon, Oscar G.; Guerra, J.M.

    2005-10-15

    We report a direct experimental observation of antiphase oscillations in population dynamics in lasers. We show that these population oscillations are intrinsically related to the well-known antiphase polarization dynamics, i.e., the antiphase oscillations of two orthogonal polarization laser field states. We have used a class B Nd:YAG (yttrium aluminum garnet) laser.

  17. Factors affecting outdoor exposure in winter: population-based study

    NASA Astrophysics Data System (ADS)

    Mäkinen, Tiina M.; Raatikka, Veli-Pekka; Rytkönen, Mika; Jokelainen, Jari; Rintamäki, Hannu; Ruuhela, Reija; Näyhä, Simo; Hassi, Juhani

    2006-09-01

    The extent of outdoor exposure during winter and factors affecting it were examined in a cross-sectional population study in Finland. Men and women aged 25-74 years from the National FINRISK 2002 sub-study ( n=6,591) were queried about their average weekly occupational, leisure-time and total cold exposure during the past winter. The effects of gender, age, area of residence, occupation, ambient temperature, self-rated health, physical activity and education on cold exposure were analysed. The self-reported median total cold exposure time was 7 h/week (8 h men, 6 h women),<1 h/week (2 h men, 0 h women) at work, 4 h/week (5 h men, 4 h women) during leisure time and 1 h/week (1 h men, 1.5 h women) while commuting to work. Factors associated with increased occupational cold exposure among men were: being employed in agriculture, forestry and industry/mining/construction or related occupations, being less educated and being aged 55-64 years. Factors associated with increased leisure-time cold exposure among men were: employment in industry/mining/construction or related occupations, being a pensioner or unemployed, reporting at least average health, being physically active and having college or vocational education. Among women, being a housewife, pensioner or unemployed and engaged in physical activity increased leisure-time cold exposure, and young women were more exposed than older ones. Self-rated health was positively associated with leisure time cold exposure in men and only to a minor extent in women. In conclusion, the subjects reported spending 4% of their total time under cold exposure, most of it (71%) during leisure time. Both occupational and leisure-time cold exposure is greater among men than women.

  18. Relations between affective music and speech: evidence from dynamics of affective piano performance and speech production

    PubMed Central

    Liu, Xiaoluan; Xu, Yi

    2015-01-01

    This study compares affective piano performance with speech production from the perspective of dynamics: unlike previous research, this study uses finger force and articulatory effort as indexes reflecting the dynamics of affective piano performance and speech production respectively. Moreover, for the first time physical constraints such as piano fingerings and speech articulatory constraints are included due to their potential contribution to different patterns of dynamics. A piano performance experiment and speech production experiment were conducted in four emotions: anger, fear, happiness and sadness. The results show that in both piano performance and speech production, anger and happiness generally have high dynamics while sadness has the lowest dynamics. Fingerings interact with fear in the piano experiment and articulatory constraints interact with anger in the speech experiment, i.e., large physical constraints produce significantly higher dynamics than small physical constraints in piano performance under the condition of fear and in speech production under the condition of anger. Using production experiments, this study firstly supports previous perception studies on relations between affective music and speech. Moreover, this is the first study to show quantitative evidence for the importance of considering motor aspects such as dynamics in comparing music performance and speech production in which motor mechanisms play a crucial role. PMID:26217252

  19. Relations between affective music and speech: evidence from dynamics of affective piano performance and speech production.

    PubMed

    Liu, Xiaoluan; Xu, Yi

    2015-01-01

    This study compares affective piano performance with speech production from the perspective of dynamics: unlike previous research, this study uses finger force and articulatory effort as indexes reflecting the dynamics of affective piano performance and speech production respectively. Moreover, for the first time physical constraints such as piano fingerings and speech articulatory constraints are included due to their potential contribution to different patterns of dynamics. A piano performance experiment and speech production experiment were conducted in four emotions: anger, fear, happiness and sadness. The results show that in both piano performance and speech production, anger and happiness generally have high dynamics while sadness has the lowest dynamics. Fingerings interact with fear in the piano experiment and articulatory constraints interact with anger in the speech experiment, i.e., large physical constraints produce significantly higher dynamics than small physical constraints in piano performance under the condition of fear and in speech production under the condition of anger. Using production experiments, this study firstly supports previous perception studies on relations between affective music and speech. Moreover, this is the first study to show quantitative evidence for the importance of considering motor aspects such as dynamics in comparing music performance and speech production in which motor mechanisms play a crucial role. PMID:26217252

  20. Cycles, stochasticity and density dependence in pink salmon population dynamics.

    PubMed

    Krkosek, Martin; Hilborn, Ray; Peterman, Randall M; Quinn, Thomas P

    2011-07-01

    Complex dynamics of animal populations often involve deterministic and stochastic components. A fascinating example is the variation in magnitude of 2-year cycles in abundances of pink salmon (Oncorhynchus gorbuscha) stocks along the North Pacific rim. Pink salmon have a 2-year anadromous and semelparous life cycle, resulting in odd- and even-year lineages that occupy the same habitats but are reproductively isolated in time. One lineage is often much more abundant than the other in a given river, and there are phase switches in dominance between odd- and even-year lines. In some regions, the weak line is absent and in others both lines are abundant. Our analysis of 33 stocks indicates that these patterns probably result from stochastic perturbations of damped oscillations owing to density-dependent mortality caused by interactions between lineages. Possible mechanisms are cannibalism, disease transmission, food depletion and habitat degradation by which one lineage affects the other, although no mechanism has been well-studied. Our results provide comprehensive empirical estimates of lagged density-dependent mortality in salmon populations and suggest that a combination of stochasticity and density dependence drives cyclical dynamics of pink salmon stocks. PMID:21147806

  1. Evolutionary dynamics with fluctuating population sizes and strong mutualism

    NASA Astrophysics Data System (ADS)

    Chotibut, Thiparat; Nelson, David R.

    2015-08-01

    Game theory ideas provide a useful framework for studying evolutionary dynamics in a well-mixed environment. This approach, however, typically enforces a strictly fixed overall population size, deemphasizing natural growth processes. We study a competitive Lotka-Volterra model, with number fluctuations, that accounts for natural population growth and encompasses interaction scenarios typical of evolutionary games. We show that, in an appropriate limit, the model describes standard evolutionary games with both genetic drift and overall population size fluctuations. However, there are also regimes where a varying population size can strongly influence the evolutionary dynamics. We focus on the strong mutualism scenario and demonstrate that standard evolutionary game theory fails to describe our simulation results. We then analytically and numerically determine fixation probabilities as well as mean fixation times using matched asymptotic expansions, taking into account the population size degree of freedom. These results elucidate the interplay between population dynamics and evolutionary dynamics in well-mixed systems.

  2. Evolutionary dynamics with fluctuating population sizes and strong mutualism.

    PubMed

    Chotibut, Thiparat; Nelson, David R

    2015-08-01

    Game theory ideas provide a useful framework for studying evolutionary dynamics in a well-mixed environment. This approach, however, typically enforces a strictly fixed overall population size, deemphasizing natural growth processes. We study a competitive Lotka-Volterra model, with number fluctuations, that accounts for natural population growth and encompasses interaction scenarios typical of evolutionary games. We show that, in an appropriate limit, the model describes standard evolutionary games with both genetic drift and overall population size fluctuations. However, there are also regimes where a varying population size can strongly influence the evolutionary dynamics. We focus on the strong mutualism scenario and demonstrate that standard evolutionary game theory fails to describe our simulation results. We then analytically and numerically determine fixation probabilities as well as mean fixation times using matched asymptotic expansions, taking into account the population size degree of freedom. These results elucidate the interplay between population dynamics and evolutionary dynamics in well-mixed systems. PMID:26382443

  3. Earthworm ecology affects the population structure of their Verminephrobacter symbionts.

    PubMed

    Viana, Flávia; Jensen, Christopher Erik; Macey, Michael; Schramm, Andreas; Lund, Marie Braad

    2016-05-01

    Earthworms carry species-specific Verminephrobacter symbionts in their nephridia (excretory organs). The symbionts are vertically transmitted via the cocoon, can only colonize the host during early embryonic development, and have co-speciated with their host for about 100 million years. Although several studies have addressed Verminephrobacter diversity between worm species, the intra-species diversity of the symbiont population has never been investigated. In this study, symbiont population structure was examined by using a multi-locus sequence typing (MLST) approach on Verminephrobacter isolated from two contrasting ecological types of earthworm hosts: the high population density, fast reproducing compost worms, Eisenia andrei and Eisenia fetida, and the low-density, slow reproducing Aporrectodea tuberculata, commonly found in garden soils. Three distinct populations were investigated for both types and, according to MLST analysis of 193 Verminephrobacter isolates, the symbiont community in each worm individual was very homogeneous. The more solitary A. tuberculata carried unique symbiont populations in 9 out of 10 host individuals, whereas the symbiont populations in the social compost worms were homogeneous across host individuals from the same population. These data suggested that host ecology shaped the population structure of Verminephrobacter symbionts. The homogeneous symbiont populations in the compost worms led to the hypothesis that Verminephrobacter could be transferred bi-parentally or via leaky horizontal transmission in high-density, frequently mating worm populations. PMID:27040820

  4. [The effect of the new technological revolution on population dynamics].

    PubMed

    Wu, K

    1985-01-29

    The impact of modernization on population dynamics in China is examined. The author notes that the industrialization process involves the concentration of the population in urban areas and the mechanization of agriculture. The need to redistribute the urban population from major urban areas to smaller towns is noted. PMID:12314273

  5. Population dynamics of Yellowstone grizzly bears

    SciTech Connect

    Knight, R.R.; Eberhardt, L.L.

    1985-04-01

    Data on the population of grizzly bears in the environs of Yellowstone National Park suggest that the population has not recovered from the reductions following closure of garbage dumps in 1970 and 1971, and may continue to decline. A computer simulation model indicates that the risk of extirpation over the next 30 yr is small, if the present population parameters continue to prevail. A review an further analysis of the available data brings out the importance of enhancing adult female survival if the population is to recover, and assesses various research needs. In particular, a reliable index of population trend is needed to augment available data on the population. 12 references, 9 figures, 6 tables.

  6. [Population dynamics and education in Paraguay].

    PubMed

    1977-01-01

    Formulation of development plans and of demographic policies for Paraguay must take into consideration the national reality as a whole, with its cultural, moral, religious, and political values. Other factors to be considered are: 1) the relatively low density of the population; 2) the low mortality, which influences a rather rapid population growth; 3) the predominance of a population in young age; and, 4) the new tendency to urbanzation. PMID:12309623

  7. "Population dynamics of crustaceans": introduction to the symposium.

    PubMed

    Buhay, Jennifer E

    2011-10-01

    Crustaceans are a globally-distributed faunal group, found across all habitats from the equator to the poles. They are an ideal focal assemblage for assessment of the impacts of climatic change and anthropogenic disturbance on nonmodel systems, such as how sea currents influence the movements of zooplankton communities in the open ocean, or how ecosystem processes affect phytoplanktonic species with restricted geographic distributions across a cluster of island lakes that could be a new model system for studies of speciation. This symposium introduced early-career researchers working in the fields of phylogeography, ecogenomics, fisheries management, and ecosystem processes with the aim of highlighting the different genetic and ecological approaches to the study of population dynamics of freshwater, estuarine, and marine crustacean species. PMID:21856734

  8. Introducing Dynamic Analysis Using Malthus's Principle of Population.

    ERIC Educational Resources Information Center

    Pingle, Mark

    2003-01-01

    Declares the use of dynamic models is increasing in macroeconomics. Explains how to introduce dynamic models to students whose technical skills are modest or varied. Chooses Malthus's Principle of Population as a natural context for introducing dynamic analysis because it provides a method for reviewing the mathematical tools and theoretical…

  9. Exploitation of chemical signaling by parasitoids: impact on host population dynamics.

    PubMed

    Lof, Marjolein E; De Gee, Maarten; Dicke, Marcel; Gort, Gerrit; Hemerik, Lia

    2013-06-01

    Chemical information mediates species interactions in a wide range of organisms. Yet, the effect of chemical information on population dynamics is rarely addressed. We designed a spatio-temporal parasitoid--host model to investigate the population dynamics when both the insect host and the parasitic wasp that attacks it can respond to chemical information. The host species, Drosophila melanogaster, uses food odors and aggregation pheromone to find a suitable resource for reproduction. The larval parasitoid, Leptopilina heterotoma, uses these same odors to find its hosts. We show that when parasitoids can respond to food odors, this negatively affects fruit fly population growth. However, extra parasitoid responsiveness to aggregation pheromone does not affect fruit fly population growth. Our results indicate that the use of the aggregation pheromone by D. melanogaster does not lead to an increased risk of parasitism. Moreover, the use of aggregation pheromone by the host enhances its population growth and enables it to persist at higher parasitoid densities. PMID:23689875

  10. Local extinction synchronizes population dynamics in spatial networks.

    PubMed

    Matter, Stephen F; Roland, Jens

    2010-03-01

    Spatial population theory predicts that synchrony in the dynamics of local populations should decrease as dispersal among populations decreases. Thus, it would be expected that the extinction of local populations and the attendant loss of immigrants to surrounding populations would reduce synchrony. We tested this hypothesis through a large-scale experiment, simulation of the experimental system and general models. Experimental removal of two adjacent subpopulations of the Rocky Mountain Apollo butterfly, Parnassius smintheus within a network consisting of 15 other local populations resulted in a decrease in immigration to surrounding populations that was proportional to their connectivity to the removal populations. These populations also showed a significant increase in synchrony during population removal. The spatial extent of the synchrony showed good agreement with the predicted loss of immigrants owing to the removals. Simulation of the Parnassius system showed a similar short-term result and also indicated that permanent loss of populations produces structural changes increasing synchrony. General models indicate that an increase in synchrony following extinction occurs when populations undergoing extinction have different carrying capacities than surrounding populations. The result is not owing to biased migration per se, but rather is because of the number of immigrants relative to the carrying capacity. Synchrony following extinction should be most common for patchy populations, but can occur in any situation where carrying capacities differ. Overall, our results indicate that local extinction can create a positive feedback for extinction risk, increasing the probability of extinction for population networks by synchronizing their dynamics. PMID:19889700

  11. Positive Affect and the Complex Dynamics of Human Flourishing

    ERIC Educational Resources Information Center

    Fredrickson, Barbara L.; Losada, Marcial F.

    2005-01-01

    Extending B. L. Fredrickson's (1998) broaden-and-build theory of positive emotions and M. Losada's (1999) nonlinear dynamics model of team performance, the authors predict that a ratio of positive to negative affect at or above 2.9 will characterize individuals in flourishing mental health. Participants (N=188) completed an initial survey to…

  12. Delay driven spatiotemporal chaos in single species population dynamics models.

    PubMed

    Jankovic, Masha; Petrovskii, Sergei; Banerjee, Malay

    2016-08-01

    Questions surrounding the prevalence of complex population dynamics form one of the central themes in ecology. Limit cycles and spatiotemporal chaos are examples that have been widely recognised theoretically, although their importance and applicability to natural populations remains debatable. The ecological processes underlying such dynamics are thought to be numerous, though there seems to be consent as to delayed density dependence being one of the main driving forces. Indeed, time delay is a common feature of many ecological systems and can significantly influence population dynamics. In general, time delays may arise from inter- and intra-specific trophic interactions or population structure, however in the context of single species populations they are linked to more intrinsic biological phenomena such as gestation or resource regeneration. In this paper, we consider theoretically the spatiotemporal dynamics of a single species population using two different mathematical formulations. Firstly, we revisit the diffusive logistic equation in which the per capita growth is a function of some specified delayed argument. We then modify the model by incorporating a spatial convolution which results in a biologically more viable integro-differential model. Using the combination of analytical and numerical techniques, we investigate the effect of time delay on pattern formation. In particular, we show that for sufficiently large values of time delay the system's dynamics are indicative to spatiotemporal chaos. The chaotic dynamics arising in the wake of a travelling population front can be preceded by either a plateau corresponding to dynamical stabilisation of the unstable equilibrium or by periodic oscillations. PMID:27154920

  13. Reproductive interference between Rana dalmatina and Rana temporaria affects reproductive success in natural populations.

    PubMed

    Hettyey, Attila; Vági, Balázs; Kovács, Tibor; Ujszegi, János; Katona, Patrik; Szederkényi, Márk; Pearman, Peter B; Griggio, Matteo; Hoi, Herbert

    2014-10-01

    Experimental evidence suggests that reproductive interference between heterospecifics can seriously affect individual fitness; support from field studies for such an effect has, however, remained scarce. We studied reproductive interference in 25 natural breeding ponds in an area where two ranid frogs, Rana dalmatina and Rana temporaria, co-occur. The breeding seasons of the two species usually overlap and males of both species are often found in amplexus with heterospecific females, even though matings between heterospecifics produce no viable offspring. We estimated species abundance ratios based on the number of clutches laid and evaluated fertilization success. In ponds with low spatial complexity and a species abundance ratio biased towards R. temporaria, the average fertilization success of R. dalmatina eggs decreased, while this relationship was not detectable in spatially more complex ponds. Fertilization success of R. temporaria did not decrease with increasing relative numbers of heterospecifics. This asymmetry in fitness effects of reproductive interference may be attributed to R. temporaria males being more competitive in scramble competition for females than R. dalmatina males. Our study is among the first to demonstrate that in natural breeding populations of vertebrates interference among heterospecifics has the potential to substantially lower reproductive success at the population level, which may in turn affect population dynamics. PMID:25138258

  14. Maximizing the benefits of antiretroviral therapy for key affected populations

    PubMed Central

    Grubb, Ian R; Beckham, Sarah W; Kazatchkine, Michel; Thomas, Ruth M; Albers, Eliot R; Cabral, Mauro; Lange, Joep; Vella, Stefano; Kurian, Manoj; Beyrer, Chris

    2014-01-01

    Introduction Scientific research has demonstrated the clinical benefits of earlier initiation of antiretroviral treatment (ART), and that ART can markedly reduce HIV transmission to sexual partners. Ensuring universal access to ART for those who need it has long been a core principle of the HIV response, and extending the benefits of ART to key populations is critical to increasing the impact of ART and the overall effectiveness of the HIV response. However, this can only be achieved through coordinated efforts to address political, social, legal and economic barriers that key populations face in accessing HIV services. Discussion Recent analyses show that HIV prevalence levels among key populations are far higher than among the general population, and they experience a range of biological and behavioural factors, and social, legal and economic barriers that increase their vulnerability to HIV and have resulted in alarmingly low ART coverage. World Health Organization 2014 consolidated guidance on HIV among key populations offers the potential for increased access to ART by key populations, following the same principles as for the general adult population. However, it should not be assumed that key populations will achieve greater access to ART unless stigma, discrimination and punitive laws, policies and practices that limit access to ART and other HIV interventions in many countries are addressed. Conclusions Rights-based approaches and investments in critical enablers, such as supportive legal and policy environments, are essential to enable wider access to ART and other HIV interventions for key populations. The primary objective of ART should always be to treat the person living with HIV; prevention is an important, additional benefit. ART should be provided only with informed consent. The preventive benefits of treatment must not be used as a pretext for failure to provide other necessary HIV programming for key populations, including comprehensive harm

  15. Stochastic population dynamics under resource constraints

    NASA Astrophysics Data System (ADS)

    Gavane, Ajinkya S.; Nigam, Rahul

    2016-06-01

    This paper investigates the population growth of a certain species in which every generation reproduces thrice over a period of predefined time, under certain constraints of resources needed for survival of population. We study the survival period of a species by randomizing the reproduction probabilities within a window at same predefined ages and the resources are being produced by the working force of the population at a variable rate. This randomness in the reproduction rate makes the population growth stochastic in nature and one cannot predict the exact form of evolution. Hence we study the growth by running simulations for such a population and taking an ensemble averaged over 500 to 5000 such simulations as per the need. While the population reproduces in a stochastic manner, we have implemented a constraint on the amount of resources available for the population. This is important to make the simulations more realistic. The rate of resource production then is tuned to find the rate which suits the survival of the species. We also compute the mean life time of the species corresponding to different resource production rate. Study for these outcomes in the parameter space defined by the reproduction probabilities and rate of resource production is carried out.

  16. Network Diversity and Affect Dynamics: The Role of Personality Traits.

    PubMed

    Alshamsi, Aamena; Pianesi, Fabio; Lepri, Bruno; Pentland, Alex; Rahwan, Iyad

    2016-01-01

    People divide their time unequally among their social contacts due to time constraints and varying strength of relationships. It was found that high diversity of social communication, dividing time more evenly among social contacts, is correlated with economic well-being both at macro and micro levels. Besides economic well-being, it is not clear how the diversity of social communication is also associated with the two components of individuals' subjective well-being, positive and negative affect. Specifically, positive affect and negative affect are two independent dimensions representing the experience (feeling) of emotions. In this paper, we investigate the relationship between the daily diversity of social communication and dynamic affect states that people experience in their daily lives. We collected two high-resolution datasets that capture affect scores via daily experience sampling surveys and social interaction through wearable sensing technologies: sociometric badges for face-to-face interaction and smart phones for mobile phone calls. We found that communication diversity correlates with desirable affect states--e.g. an increase in the positive affect state or a decrease in the negative affect state--for some personality types, but correlates with undesirable affect states for others. For example, diversity in phone calls is experienced as good by introverts, but bad by extroverts; diversity in face-to-face interaction is experienced as good by people who tend to be positive by nature (trait) but bad for people who tend to be not positive by nature. More broadly, the moderating effect of personality type on the relationship between diversity and affect was detected without any knowledge of the type of social tie or the content of communication. This provides further support for the power of unobtrusive sensing in understanding social dynamics, and in measuring the effect of potential interventions designed to improve well-being. PMID:27035904

  17. Network Diversity and Affect Dynamics: The Role of Personality Traits

    PubMed Central

    Alshamsi, Aamena; Pianesi, Fabio; Lepri, Bruno; Pentland, Alex; Rahwan, Iyad

    2016-01-01

    People divide their time unequally among their social contacts due to time constraints and varying strength of relationships. It was found that high diversity of social communication, dividing time more evenly among social contacts, is correlated with economic well-being both at macro and micro levels. Besides economic well-being, it is not clear how the diversity of social communication is also associated with the two components of individuals’ subjective well-being, positive and negative affect. Specifically, positive affect and negative affect are two independent dimensions representing the experience (feeling) of emotions. In this paper, we investigate the relationship between the daily diversity of social communication and dynamic affect states that people experience in their daily lives. We collected two high-resolution datasets that capture affect scores via daily experience sampling surveys and social interaction through wearable sensing technologies: sociometric badges for face-to-face interaction and smart phones for mobile phone calls. We found that communication diversity correlates with desirable affect states–e.g. an increase in the positive affect state or a decrease in the negative affect state–for some personality types, but correlates with undesirable affect states for others. For example, diversity in phone calls is experienced as good by introverts, but bad by extroverts; diversity in face-to-face interaction is experienced as good by people who tend to be positive by nature (trait) but bad for people who tend to be not positive by nature. More broadly, the moderating effect of personality type on the relationship between diversity and affect was detected without any knowledge of the type of social tie or the content of communication. This provides further support for the power of unobtrusive sensing in understanding social dynamics, and in measuring the effect of potential interventions designed to improve well-being. PMID:27035904

  18. Daily Interpersonal and Affective Dynamics in Personality Disorder

    PubMed Central

    Wright, Aidan G.C.; Hopwood, Christopher J.; Simms, Leonard J.

    2015-01-01

    In this naturalistic study we adopt the lens of interpersonal theory to examine between-and within-person differences in dynamic processes of daily affect and interpersonal behaviors among individuals (N = 101) previously diagnosed with personality disorders who completed daily diaries over the course of 100 days. Dispositional ratings of interpersonal problems and measures of daily stress were used as predictors of daily shifts in interpersonal behavior and affect in multilevel models. Results indicate that ~40%–50% of the variance in interpersonal behavior and affect is due to daily fluctuations, which are modestly related to dispositional measures of interpersonal problems but strongly related to daily stress. The findings support conceptions of personality disorders as a dynamic form of psychopathology involving the individuals interacting with and regulating in response to the contextual features of their environment. PMID:26200849

  19. Factors affecting levels of genetic diversity in natural populations.

    PubMed Central

    Amos, W; Harwood, J

    1998-01-01

    Genetic variability is the clay of evolution, providing the base material on which adaptation and speciation depend. It is often assumed that most interspecific differences in variability are due primarily to population size effects, with bottlenecked populations carrying less variability than those of stable size. However, we show that population bottlenecks are unlikely to be the only factor, even in classic case studies such as the northern elephant seal and the cheetah, where genetic polymorphism is virtually absent. Instead, we suggest that the low levels of variability observed in endangered populations are more likely to result from a combination of publication biases, which tend to inflate the level of variability which is considered 'normal', and inbreeding effects, which may hasten loss of variability due to drift. To account for species with large population sizes but low variability we advance three hypotheses. First, it is known that certain metapopulation structures can result in effective population sizes far below the census size. Second, there is increasing evidence that heterozygous sites mutate more frequently than equivalent homozygous sites, plausibly because mismatch repair between homologous chromosomes during meiosis provides extra opportunities to mutate. Such a mechanism would undermine the simple relationship between heterozygosity and effective population size. Third, the fact that related species that differ greatly in variability implies that large amounts of variability can be gained or lost rapidly. We argue that such cases are best explained by rapid loss through a genome-wide selective sweep, and suggest a mechanism by which this could come about, based on forced changes to a control gene inducing coevolution in the genes it controls. Our model, based on meiotic drive in mammals, but easily extended to other systems, would tend to facilitate population isolation by generating molecular incompatabilities. Circumstances can even be

  20. Galactic civilizations: Population dynamics and interstellar diffusion

    NASA Technical Reports Server (NTRS)

    Newman, W. I.; Sagan, C.

    1978-01-01

    The interstellar diffusion of galactic civilizations is reexamined by potential theory; both numerical and analytical solutions are derived for the nonlinear partial differential equations which specify a range of relevant models, drawn from blast wave physics, soil science, and, especially, population biology. An essential feature of these models is that, for all civilizations, population growth must be limited by the carrying capacity of the environment. Dispersal is fundamentally a diffusion process; a density-dependent diffusivity describes interstellar emigration. Two models are considered: the first describing zero population growth (ZPG), and the second which also includes local growth and saturation of a planetary population, and for which an asymptotic traveling wave solution is found.

  1. Stochastic dynamics and logistic population growth.

    PubMed

    Méndez, Vicenç; Assaf, Michael; Campos, Daniel; Horsthemke, Werner

    2015-06-01

    The Verhulst model is probably the best known macroscopic rate equation in population ecology. It depends on two parameters, the intrinsic growth rate and the carrying capacity. These parameters can be estimated for different populations and are related to the reproductive fitness and the competition for limited resources, respectively. We investigate analytically and numerically the simplest possible microscopic scenarios that give rise to the logistic equation in the deterministic mean-field limit. We provide a definition of the two parameters of the Verhulst equation in terms of microscopic parameters. In addition, we derive the conditions for extinction or persistence of the population by employing either the momentum-space spectral theory or the real-space Wentzel-Kramers-Brillouin approximation to determine the probability distribution function and the mean time to extinction of the population. Our analytical results agree well with numerical simulations. PMID:26172687

  2. Stochastic dynamics and logistic population growth

    NASA Astrophysics Data System (ADS)

    Méndez, Vicenç; Assaf, Michael; Campos, Daniel; Horsthemke, Werner

    2015-06-01

    The Verhulst model is probably the best known macroscopic rate equation in population ecology. It depends on two parameters, the intrinsic growth rate and the carrying capacity. These parameters can be estimated for different populations and are related to the reproductive fitness and the competition for limited resources, respectively. We investigate analytically and numerically the simplest possible microscopic scenarios that give rise to the logistic equation in the deterministic mean-field limit. We provide a definition of the two parameters of the Verhulst equation in terms of microscopic parameters. In addition, we derive the conditions for extinction or persistence of the population by employing either the momentum-space spectral theory or the real-space Wentzel-Kramers-Brillouin approximation to determine the probability distribution function and the mean time to extinction of the population. Our analytical results agree well with numerical simulations.

  3. Parsimonious snow model explains reindeer population dynamics and ranging behavior

    NASA Astrophysics Data System (ADS)

    Kohler, J.; Aanes, R.; Hansen, B. B.; Loe, L.; Severinsen, T.; Stien, A.

    2008-12-01

    Winter snow is a key factor affecting polar ecosystems. One example is the strong negative correlation of winter precipitation with fluctuations in population in some high-arctic animal populations. Ice layers within and at the base of the snowpack have particularly deleterious effects on such populations. Svalbard reindeer have small home ranges and are vulnerable to local "locked pasture" events due to ground-ice formation. When pastures are locked, reindeer are faced with the decision of staying, living off a diminishing fat store, or trying to escape beyond the unknown spatial borders of the ice. Both strategies may inhibit reproduction and increase mortality, leading to population declines. Here we assess the impact of winter snow and ice on the population dynamics of an isolated herd of Svalbard reindeer near Ny-Ålesund, monitored annually since 1978, with a retrospective analysis of the winter snowpack. Because there are no long-term observational records of snow or snow properties, such as ice layers, we must recourse to snowpack modeling. A parsimonious model of snow and ground-ice thickness is driven with daily temperature and precipitation data collected at a nearby weather station. The model uses the degree-day concept and has three adjustable parameters which are tuned to correlate model snow and ground-ice thicknesses to the limited observations available: April snow accumulation measurements on two local glaciers, and a limited number of ground-ice observations made in recent years. Parameter values used are comparable to those reported elsewhere. We find that modeled mean winter ground-ice thickness explains a significant percentage of the observed variance in reindeer population growth rate. Adding other explanatory parameters, such as modeled mean winter snowpack thickness or previous years' population size does not significanly improve the relation. Furthermore, positioning data from a small subset of reindeer show that model icing events are

  4. Form of an evolutionary tradeoff affects eco-evolutionary dynamics in a predator–prey system

    PubMed Central

    Kasada, Minoru; Yamamichi, Masato; Yoshida, Takehito

    2014-01-01

    Evolution on a time scale similar to ecological dynamics has been increasingly recognized for the last three decades. Selection mediated by ecological interactions can change heritable phenotypic variation (i.e., evolution), and evolution of traits, in turn, can affect ecological interactions. Hence, ecological and evolutionary dynamics can be tightly linked and important to predict future dynamics, but our understanding of eco-evolutionary dynamics is still in its infancy and there is a significant gap between theoretical predictions and empirical tests. Empirical studies have demonstrated that the presence of genetic variation can dramatically change ecological dynamics, whereas theoretical studies predict that eco-evolutionary dynamics depend on the details of the genetic variation, such as the form of a tradeoff among genotypes, which can be more important than the presence or absence of the genetic variation. Using a predator–prey (rotifer–algal) experimental system in laboratory microcosms, we studied how different forms of a tradeoff between prey defense and growth affect eco-evolutionary dynamics. Our experimental results show for the first time to our knowledge that different forms of the tradeoff produce remarkably divergent eco-evolutionary dynamics, including near fixation, near extinction, and coexistence of algal genotypes, with quantitatively different population dynamics. A mathematical model, parameterized from completely independent experiments, explains the observed dynamics. The results suggest that knowing the details of heritable trait variation and covariation within a population is essential for understanding how evolution and ecology will interact and what form of eco-evolutionary dynamics will result. PMID:25336757

  5. Form of an evolutionary tradeoff affects eco-evolutionary dynamics in a predator-prey system.

    PubMed

    Kasada, Minoru; Yamamichi, Masato; Yoshida, Takehito

    2014-11-11

    Evolution on a time scale similar to ecological dynamics has been increasingly recognized for the last three decades. Selection mediated by ecological interactions can change heritable phenotypic variation (i.e., evolution), and evolution of traits, in turn, can affect ecological interactions. Hence, ecological and evolutionary dynamics can be tightly linked and important to predict future dynamics, but our understanding of eco-evolutionary dynamics is still in its infancy and there is a significant gap between theoretical predictions and empirical tests. Empirical studies have demonstrated that the presence of genetic variation can dramatically change ecological dynamics, whereas theoretical studies predict that eco-evolutionary dynamics depend on the details of the genetic variation, such as the form of a tradeoff among genotypes, which can be more important than the presence or absence of the genetic variation. Using a predator-prey (rotifer-algal) experimental system in laboratory microcosms, we studied how different forms of a tradeoff between prey defense and growth affect eco-evolutionary dynamics. Our experimental results show for the first time to our knowledge that different forms of the tradeoff produce remarkably divergent eco-evolutionary dynamics, including near fixation, near extinction, and coexistence of algal genotypes, with quantitatively different population dynamics. A mathematical model, parameterized from completely independent experiments, explains the observed dynamics. The results suggest that knowing the details of heritable trait variation and covariation within a population is essential for understanding how evolution and ecology will interact and what form of eco-evolutionary dynamics will result. PMID:25336757

  6. Dynamic population mapping using mobile phone data.

    PubMed

    Deville, Pierre; Linard, Catherine; Martin, Samuel; Gilbert, Marius; Stevens, Forrest R; Gaughan, Andrea E; Blondel, Vincent D; Tatem, Andrew J

    2014-11-11

    During the past few decades, technologies such as remote sensing, geographical information systems, and global positioning systems have transformed the way the distribution of human population is studied and modeled in space and time. However, the mapping of populations remains constrained by the logistics of censuses and surveys. Consequently, spatially detailed changes across scales of days, weeks, or months, or even year to year, are difficult to assess and limit the application of human population maps in situations in which timely information is required, such as disasters, conflicts, or epidemics. Mobile phones (MPs) now have an extremely high penetration rate across the globe, and analyzing the spatiotemporal distribution of MP calls geolocated to the tower level may overcome many limitations of census-based approaches, provided that the use of MP data is properly assessed and calibrated. Using datasets of more than 1 billion MP call records from Portugal and France, we show how spatially and temporarily explicit estimations of population densities can be produced at national scales, and how these estimates compare with outputs produced using alternative human population mapping methods. We also demonstrate how maps of human population changes can be produced over multiple timescales while preserving the anonymity of MP users. With similar data being collected every day by MP network providers across the world, the prospect of being able to map contemporary and changing human population distributions over relatively short intervals exists, paving the way for new applications and a near real-time understanding of patterns and processes in human geography. PMID:25349388

  7. Dynamic population mapping using mobile phone data

    PubMed Central

    Deville, Pierre; Martin, Samuel; Gilbert, Marius; Stevens, Forrest R.; Gaughan, Andrea E.; Blondel, Vincent D.; Tatem, Andrew J.

    2014-01-01

    During the past few decades, technologies such as remote sensing, geographical information systems, and global positioning systems have transformed the way the distribution of human population is studied and modeled in space and time. However, the mapping of populations remains constrained by the logistics of censuses and surveys. Consequently, spatially detailed changes across scales of days, weeks, or months, or even year to year, are difficult to assess and limit the application of human population maps in situations in which timely information is required, such as disasters, conflicts, or epidemics. Mobile phones (MPs) now have an extremely high penetration rate across the globe, and analyzing the spatiotemporal distribution of MP calls geolocated to the tower level may overcome many limitations of census-based approaches, provided that the use of MP data is properly assessed and calibrated. Using datasets of more than 1 billion MP call records from Portugal and France, we show how spatially and temporarily explicit estimations of population densities can be produced at national scales, and how these estimates compare with outputs produced using alternative human population mapping methods. We also demonstrate how maps of human population changes can be produced over multiple timescales while preserving the anonymity of MP users. With similar data being collected every day by MP network providers across the world, the prospect of being able to map contemporary and changing human population distributions over relatively short intervals exists, paving the way for new applications and a near real-time understanding of patterns and processes in human geography. PMID:25349388

  8. How a trend towards a stationary population affects consumer demand.

    PubMed

    Espenshade, T J

    1978-03-01

    Abstract During the great depression of the 1930seconomists in both the United States and Europe tried to analyse the economic consequences of declining rates of population growth. Not only were birth rates in many industrial countries at the lowest levels ever, but they coincided with high rates of unemployment. Of the many economists who held that demographic trends were partly responsible for the adverse economic conditions, a prominent example was John Maynard Keynes. According to his so-called stagnation thesis, population growth stimulates investment demand in two ways: more people need more goods and services and, hence, more investment in factories and machinery; and with population growing, businessmen are more likely to regard their investment misallocations as less serious than when the growth is slow or nil.(1)A minority of writers were more optimistic about the economic consequences of slower rates of population growth. For example, Thompson argued that with a lower ratio of consumers to producers the population would enjoy a higher standard of living and the education of children should improve.(2). PMID:22091937

  9. Effects of culling on mesopredator population dynamics.

    PubMed

    Beasley, James C; Olson, Zachary H; Beatty, William S; Dharmarajan, Guha; Rhodes, Olin E

    2013-01-01

    Anthropogenic changes in land use and the extirpation of apex predators have facilitated explosive growth of mesopredator populations. Consequently, many species have been subjected to extensive control throughout portions of their range due to their integral role as generalist predators and reservoirs of zoonotic disease. Yet, few studies have monitored the effects of landscape composition or configuration on the demographic or behavioral response of mesopredators to population manipulation. During 2007 we removed 382 raccoons (Procyon lotor) from 30 forest patches throughout a fragmented agricultural ecosystem to test hypotheses regarding the effects of habitat isolation on population recovery and role of range expansion and dispersal in patch colonization of mesopredators in heterogeneous landscapes. Patches were allowed to recolonize naturally and demographic restructuring of patches was monitored from 2008-2010 using mark-recapture. An additional 25 control patches were monitored as a baseline measure of demography. After 3 years only 40% of experimental patches had returned to pre-removal densities. This stagnant recovery was driven by low colonization rates of females, resulting in little to no within-patch recruitment. Colonizing raccoons were predominantly young males, suggesting that dispersal, rather than range expansion, was the primary mechanism driving population recovery. Contrary to our prediction, neither landscape connectivity nor measured local habitat attributes influenced colonization rates, likely due to the high dispersal capability of raccoons and limited role of range expansion in patch colonization. Although culling is commonly used to control local populations of many mesopredators, we demonstrate that such practices create severe disruptions in population demography that may be counterproductive to disease management in fragmented landscapes due to an influx of dispersing males into depopulated areas. However, given the slow repopulation

  10. Effects of Culling on Mesopredator Population Dynamics

    PubMed Central

    Beasley, James C.; Olson, Zachary H.; Beatty, William S.; Dharmarajan, Guha; Rhodes, Olin E.

    2013-01-01

    Anthropogenic changes in land use and the extirpation of apex predators have facilitated explosive growth of mesopredator populations. Consequently, many species have been subjected to extensive control throughout portions of their range due to their integral role as generalist predators and reservoirs of zoonotic disease. Yet, few studies have monitored the effects of landscape composition or configuration on the demographic or behavioral response of mesopredators to population manipulation. During 2007 we removed 382 raccoons (Procyon lotor) from 30 forest patches throughout a fragmented agricultural ecosystem to test hypotheses regarding the effects of habitat isolation on population recovery and role of range expansion and dispersal in patch colonization of mesopredators in heterogeneous landscapes. Patches were allowed to recolonize naturally and demographic restructuring of patches was monitored from 2008–2010 using mark-recapture. An additional 25 control patches were monitored as a baseline measure of demography. After 3 years only 40% of experimental patches had returned to pre-removal densities. This stagnant recovery was driven by low colonization rates of females, resulting in little to no within-patch recruitment. Colonizing raccoons were predominantly young males, suggesting that dispersal, rather than range expansion, was the primary mechanism driving population recovery. Contrary to our prediction, neither landscape connectivity nor measured local habitat attributes influenced colonization rates, likely due to the high dispersal capability of raccoons and limited role of range expansion in patch colonization. Although culling is commonly used to control local populations of many mesopredators, we demonstrate that such practices create severe disruptions in population demography that may be counterproductive to disease management in fragmented landscapes due to an influx of dispersing males into depopulated areas. However, given the slow

  11. PC BEEPOP - A PERSONAL COMPUTER HONEY BEE POPULATION DYNAMICS MODEL

    EPA Science Inventory

    PC BEEPOP is a computer model that simulates honey bee (Apis mellifera L.) colony population dynamics. he model consists of a system of interdependent elements, including colony condition, environmental variability, colony energetics, and contaminant exposure. t includes a mortal...

  12. A linear model of population dynamics

    NASA Astrophysics Data System (ADS)

    Lushnikov, A. A.; Kagan, A. I.

    2016-08-01

    The Malthus process of population growth is reformulated in terms of the probability w(n,t) to find exactly n individuals at time t assuming that both the birth and the death rates are linear functions of the population size. The master equation for w(n,t) is solved exactly. It is shown that w(n,t) strongly deviates from the Poisson distribution and is expressed in terms either of Laguerre’s polynomials or a modified Bessel function. The latter expression allows for considerable simplifications of the asymptotic analysis of w(n,t).

  13. Population dynamics of pond zooplankton, I. Diaptomus pallidus Herrick

    USGS Publications Warehouse

    Armitage, K.B.; Saxena, B.; Angino, E.E.

    1973-01-01

    The simultaneous and lag relationships between 27 environmental variables and seven population components of a perennial calanoid copepod were examined by simple and partial correlations and stepwise regression. The analyses consistently explained more than 70% of the variation of a population component. The multiple correlation coefficient (R) usually was highest in no lag or in 3-week or 4-week lag except for clutch size in which R was highest in 1-week lag. Population control, egg-bearing, and clutch size were affected primarily by environmental components categorized as weather; food apparently was relatively minor in affecting population control or reproduction. ?? 1973 Dr. W. Junk B.V. Publishers.

  14. Coral population dynamics across consecutive mass mortality events.

    PubMed

    Riegl, Bernhard; Purkis, Sam

    2015-11-01

    Annual coral mortality events due to increased atmospheric heat may occur regularly from the middle of the century and are considered apocalyptic for coral reefs. In the Arabian/Persian Gulf, this situation has already occurred and population dynamics of four widespread corals (Acropora downingi, Porites harrisoni, Dipsastrea pallida, Cyphastrea micropthalma) were examined across the first-ever occurrence of four back-to-back mass mortality events (2009-2012). Mortality was driven by diseases in 2009, bleaching and subsequent diseases in 2010/2011/2012. 2009 reduced P. harrisoni cover and size, the other events increasingly reduced overall cover (2009: -10%; 2010: -20%; 2011: -20%; 2012: -15%) and affected all examined species. Regeneration was only observed after the first disturbance. P. harrisoni and A. downingi severely declined from 2010 due to bleaching and subsequent white syndromes, while D. pallida and P. daedalea declined from 2011 due to bleaching and black-band disease. C. microphthalma cover was not affected. In all species, most large corals were lost while fission due to partial tissue mortality bolstered small size classes. This general shrinkage led to a decrease of coral cover and a dramatic reduction of fecundity. Transition matrices for disturbed and undisturbed conditions were evaluated as Life Table Response Experiment and showed that C. microphthalma changed the least in size-class dynamics and fecundity, suggesting they were 'winners'. In an ordered 'degradation cascade', impacts decreased from the most common to the least common species, leading to step-wise removal of previously dominant species. A potentially permanent shift from high- to low-coral cover with different coral community and size structure can be expected due to the demographic dynamics resultant from the disturbances. Similarities to degradation of other Caribbean and Pacific reefs are discussed. As comparable environmental conditions and mortality patterns must be

  15. Indirect effects of primary prey population dynamics on alternative prey.

    PubMed

    Barraquand, Frédéric; New, Leslie F; Redpath, Stephen; Matthiopoulos, Jason

    2015-08-01

    We develop a theory of generalist predation showing how alternative prey species are affected by changes in both mean abundance and variability (coefficient of variation) of their predator's primary prey. The theory is motivated by the indirect effects of cyclic rodent populations on ground-breeding birds, and developed through progressive analytic simplifications of an empirically-based model. It applies nonetheless to many other systems where primary prey have fast life-histories and can become superabundant, thus facilitating impact on alternative prey species and generating highly asymmetric interactions. Our results suggest that predator effects on alternative prey should generally decrease with mean primary prey abundance, and increase with primary prey variability (low to high CV)-unless predators have strong aggregative responses, in which case these results can be reversed. Approximations of models including predator dynamics (general numerical response with possible delays) confirm these results but further suggest that negative temporal correlation between predator and primary prey is harmful to alternative prey. Finally, we find that measurements of predator numerical responses are crucial to predict-even qualitatively-the response of ecosystems to changes in the dynamics of outbreaking prey species. PMID:25930160

  16. Thermoregulatory behaviour affects prevalence of chytrid fungal infection in a wild population of Panamanian golden frogs.

    PubMed

    Richards-Zawacki, Corinne L

    2010-02-22

    Predicting how climate change will affect disease dynamics requires an understanding of how the environment affects host-pathogen interactions. For amphibians, global declines and extinctions have been linked to a pathogenic chytrid fungus, Batrachochytrium dendrobatidis. Using a combination of body temperature measurements and disease assays conducted before and after the arrival of B. dendrobatidis, this study tested the hypothesis that body temperature affects the prevalence of infection in a wild population of Panamanian golden frogs (Atelopus zeteki). The timing of first detection of the fungus was consistent with that of a wave of epidemic infections spreading south and eastward through Central America. During the epidemic, many golden frogs modified their thermoregulatory behaviour, raising body temperatures above their normal set point. Odds of infection decreased with increasing body temperature, demonstrating that even slight environmental or behavioural changes have the potential to affect an individual's vulnerability to infection. The thermal dependency of the relationship between B. dendrobatidis and its amphibian hosts demonstrates how the progression of an epidemic can be influenced by complex interactions between host and pathogen phenotypes and the environments in which they are found. PMID:19864287

  17. Multistability in simplest models of the population dynamics

    NASA Astrophysics Data System (ADS)

    Zhdanova, Oksana L.; Frisman, Efim Ya.

    2016-06-01

    The investigation of dynamics behavior of population number and genetic structure has been conducted for a homogeneous limited population influenced by density-dependent selection in single di-allelic genetic locus. The detailed investigation of the mechanisms of the loss of stability in the considered model is carried out. It is shown that coexistence of several different asymptotic dynamic regimes (with own attraction basins) is possible in numerous enough parametric regions which are meaningful biologically.

  18. Temporal dynamics of a local fish community are strongly affected by immigration from the surrounding metacommunity

    PubMed Central

    Stoffels, Rick J; Clarke, Kenneth Robert; Linklater, Danielle S

    2015-01-01

    A 5-year time series of annual censuses was collected from a large floodplain lake to determine how dynamics of the local fish community were affected by changes in hydrological connectivity with the surrounding metacommunity. The lake was disconnected from the metacommunity for 1 year prior to our study and remained disconnected until 3 months before our third annual census, when a flood reconnected the lake to the metacommunity. We determined how changes in connectivity affected temporal dynamics of (1) local community composition and (2) the population composition, condition, and growth of catfish, to shed light on how immigration of other species might affect local population dynamics. Before reconnection, the community was likely shaped by interactions between the local environment and species traits. The reconnection caused significant immigration and change in community composition and correlated with a significant and abrupt decline in catfish condition, growth, and abundance; effects likely due to the immigration of a competitor with a similar trophic niche: carp. The community was slow to return to its preconnection state, which may be due to dispersal traits of the fishes, and a time-lag in the recovery of the local catfish population following transient intensification of species interactions. The dynamics observed were concordant with the species sorting and mass-effects perspectives of metacommunity theory. Floods cause episodic dispersal in floodplain fish metacommunities, and so, flood frequency determines the relative importance of regional and local processes. Local processes may be particularly important to certain species, but these species may need sufficient time between floods for population increase, before the next flood-induced dispersal episode brings competitors and predators that might cause population decline. Accordingly, species coexistence in these metacommunities may be facilitated by spatiotemporal storage effects, which may in

  19. The 5:1 Neptune Resonance: Dynamics and Population

    NASA Astrophysics Data System (ADS)

    Pike, Rosemary E.; Kavelaars, J. J.; Gladman, Brett; Petit, Jean-Marc; Alexandersen, Mike

    2014-11-01

    Based on 4 objects detected with semi-major axes near the 5:1 external resonance with Neptune, we estimate a substantial and previously unrecognized population of objects, perhaps more significant than the 3:2 (Plutino) resonance population. These external resonances are largely unexplored in both observations and dynamical simulations. However, understanding the characteristics and trapping history for objects in these populations is critical for constraining the dynamical history of the solar system. The 4 objects detected in the Canada-France Ecliptic Plane Survey (CFEPS) were classified using dynamical integrations. Three are resonant, and the last appears to be a resonant drop-off. The 3 objects are taken to be representative of the steady-state population, so by using these detections and the CFEPS characterization (pointings and detection limits) we calculate a population estimate for this resonance at ~3000(+5000 -2000) with Hg<8. This is at least as large as the Plutinos (3:2 resonance) at 90% confidence. The small number of detected objects results in such a large population estimate due to the numerous biases against detecting objects with semimajor axes at 88AU. Based on the dynamical behavior of the known objects, the trapping mechanism for the 5:1 resonance appears to be resonance sticking from the scattering objects. The long resonance lifetimes of some dynamical clones suggests that a steady state population could be maintained through periodic sticking.

  20. Explaining "Noise" as Environmental Variations in Population Dynamics

    SciTech Connect

    Ginn, Timothy R.; Loge, Frank J.; Scheibe, Timothy D.

    2007-03-01

    The impacts of human activities on our own and other populations on the plant are making news at an alarming pace. Global warming, ocean and freshwater contamination and acidification, deforestation, habitat destruction and incursion, and in general a burgeoning human population are associated with a complete spectrum of changes to the dynamics of populations. Effects on songbirds, insects, coral reefs, ocean mammals, anadromous fishes, just to name a few, and humans, have been linked to human industry and population growth. The linkage, however, remains often ghostly and often tenuous at best, because of the difficulty in quantitatively combining ecological processes with environmental fate and transport processes. Establishing quantitative tools, that is, models, for the combined dynamics of populations and environmental chemical/thermal things is needed. This truly interdisciplinary challenge is briefly reviewed, and two approaches to integrating chemical and biological intermingling are addressed in the context of salmon populations in the Pacific Northwest.

  1. AN INDIVIDUAL-BASED MODEL OF COTTUS POPULATION DYNAMICS

    EPA Science Inventory

    We explored population dynamics of a southern Appalachian population of Cottus bairdi using a spatially-explicit, individual-based model. The model follows daily growth, mortality, and spawning of individuals as a function of flow and temperature. We modeled movement of juveniles...

  2. Multiple Cancer Cell Population Dynamics in a Complex Ecology

    NASA Astrophysics Data System (ADS)

    Lin, Ke-Chih; Targa, Gonzalo; Pienta, Kenneth; Sturm, James; Austin, Robert

    We have developed a technology for study of complex ecology cancer population dynamics. The technology includes complex drug gradients, full bright field/dark field/fluorescence imaging of areas of several square millimeters and thin gas-permable membranes which allow single cell extraction and analysis. We will present results of studies of prostate cancer cell dynamics.

  3. A Particle Population Control Method for Dynamic Monte Carlo

    NASA Astrophysics Data System (ADS)

    Sweezy, Jeremy; Nolen, Steve; Adams, Terry; Zukaitis, Anthony

    2014-06-01

    A general particle population control method has been derived from splitting and Russian Roulette for dynamic Monte Carlo particle transport. A well-known particle population control method, known as the particle population comb, has been shown to be a special case of this general method. This general method has been incorporated in Los Alamos National Laboratory's Monte Carlo Application Toolkit (MCATK) and examples of it's use are shown for both super-critical and sub-critical systems.

  4. Temperament Affects Sympathetic Nervous Function in a Normal Population

    PubMed Central

    Kim, Bora; Lee, Jae-Hon; Kang, Eun-Ho

    2012-01-01

    Objective Although specific temperaments have been known to be related to autonomic nervous function in some psychiatric disorders, there are few studies that have examined the relationship between temperaments and autonomic nervous function in a normal population. In this study, we examined the effect of temperament on the sympathetic nervous function in a normal population. Methods Sixty eight healthy subjects participated in the present study. Temperament was assessed using the Korean version of the Cloninger Temperament and Character Inventory (TCI). Autonomic nervous function was determined by measuring skin temperature in a resting state, which was recorded for 5 minutes from the palmar surface of the left 5th digit using a thermistor secured with a Velcro® band. Pearson's correlation analysis and multiple linear regression were used to examine the relationship between temperament and skin temperature. Results A higher harm avoidance score was correlated with a lower skin temperature (i.e. an increased sympathetic tone; r=-0.343, p=0.004) whereas a higher persistence score was correlated with a higher skin temperature (r=0.433, p=0.001). Hierarchical linear regression analysis revealed that harm avoidance was able to predict the variance of skin temperature independently, with a variance of 7.1% after controlling for sex, blood pressure and state anxiety and persistence was the factor predicting the variance of skin temperature with a variance of 5.0%. Conclusion These results suggest that high harm avoidance is related to an increased sympathetic nervous function whereas high persistence is related to decreased sympathetic nervous function in a normal population. PMID:22993530

  5. Positive Affect and the Complex Dynamics of Human Flourishing

    PubMed Central

    Fredrickson, Barbara L.; Losada, Marcial F.

    2011-01-01

    Extending B. L. Fredrickson’s (1998) broaden-and-build theory of positive emotions and M. Losada’s (1999) nonlinear dynamics model of team performance, the authors predict that a ratio of positive to negative affect at or above 2.9 will characterize individuals in flourishing mental health. Participants (N = 188) completed an initial survey to identify flourishing mental health and then provided daily reports of experienced positive and negative emotions over 28 days. Results showed that the mean ratio of positive to negative affect was above 2.9 for individuals classified as flourishing and below that threshold for those not flourishing. Together with other evidence, these findings suggest that a set of general mathematical principles may describe the relations between positive affect and human flourishing. PMID:16221001

  6. Positive affect and the complex dynamics of human flourishing.

    PubMed

    Fredrickson, Barbara L; Losada, Marcial F

    2005-10-01

    Extending B. L. Fredrickson's (1998) broaden-and-build theory of positive emotions and M. Losada's (1999) nonlinear dynamics model of team performance, the authors predict that a ratio of positive to negative affect at or above 2.9 will characterize individuals in flourishing mental health. Participants (N=188) completed an initial survey to identify flourishing mental health and then provided daily reports of experienced positive and negative emotions over 28 days. Results showed that the mean ratio of positive to negative affect was above 2.9 for individuals classified as flourishing and below that threshold for those not flourishing. Together with other evidence, these findings suggest that a set of general mathematical principles may describe the relations between positive affect and human flourishing. PMID:16221001

  7. Long-Term Trends and Role of Climate in the Population Dynamics of Eurasian Reindeer.

    PubMed

    Uboni, Alessia; Horstkotte, Tim; Kaarlejärvi, Elina; Sévêque, Anthony; Stammler, Florian; Olofsson, Johan; Forbes, Bruce C; Moen, Jon

    2016-01-01

    Temperature is increasing in Arctic and sub-Arctic regions at a higher rate than anywhere else in the world. The frequency and nature of precipitation events are also predicted to change in the future. These changes in climate are expected, together with increasing human pressures, to have significant impacts on Arctic and sub-Arctic species and ecosystems. Due to the key role that reindeer play in those ecosystems, it is essential to understand how climate will affect the region's most important species. Our study assesses the role of climate on the dynamics of fourteen Eurasian reindeer (Rangifer tarandus) populations, using for the first time data on reindeer abundance collected over a 70-year period, including both wild and semi-domesticated reindeer, and covering more than half of the species' total range. We analyzed trends in population dynamics, investigated synchrony among population growth rates, and assessed the effects of climate on population growth rates. Trends in the population dynamics were remarkably heterogeneous. Synchrony was apparent only among some populations and was not correlated with distance among population ranges. Proxies of climate variability mostly failed to explain population growth rates and synchrony. For both wild and semi-domesticated populations, local weather, biotic pressures, loss of habitat and human disturbances appear to have been more important drivers of reindeer population dynamics than climate. In semi-domesticated populations, management strategies may have masked the effects of climate. Conservation efforts should aim to mitigate human disturbances, which could exacerbate the potentially negative effects of climate change on reindeer populations in the future. Special protection and support should be granted to those semi-domesticated populations that suffered the most because of the collapse of the Soviet Union, in order to protect the livelihood of indigenous peoples that depend on the species, and the multi

  8. Long-Term Trends and Role of Climate in the Population Dynamics of Eurasian Reindeer

    PubMed Central

    Horstkotte, Tim; Kaarlejärvi, Elina; Sévêque, Anthony; Stammler, Florian; Olofsson, Johan; Forbes, Bruce C.; Moen, Jon

    2016-01-01

    Temperature is increasing in Arctic and sub-Arctic regions at a higher rate than anywhere else in the world. The frequency and nature of precipitation events are also predicted to change in the future. These changes in climate are expected, together with increasing human pressures, to have significant impacts on Arctic and sub-Arctic species and ecosystems. Due to the key role that reindeer play in those ecosystems, it is essential to understand how climate will affect the region’s most important species. Our study assesses the role of climate on the dynamics of fourteen Eurasian reindeer (Rangifer tarandus) populations, using for the first time data on reindeer abundance collected over a 70-year period, including both wild and semi-domesticated reindeer, and covering more than half of the species’ total range. We analyzed trends in population dynamics, investigated synchrony among population growth rates, and assessed the effects of climate on population growth rates. Trends in the population dynamics were remarkably heterogeneous. Synchrony was apparent only among some populations and was not correlated with distance among population ranges. Proxies of climate variability mostly failed to explain population growth rates and synchrony. For both wild and semi-domesticated populations, local weather, biotic pressures, loss of habitat and human disturbances appear to have been more important drivers of reindeer population dynamics than climate. In semi-domesticated populations, management strategies may have masked the effects of climate. Conservation efforts should aim to mitigate human disturbances, which could exacerbate the potentially negative effects of climate change on reindeer populations in the future. Special protection and support should be granted to those semi-domesticated populations that suffered the most because of the collapse of the Soviet Union, in order to protect the livelihood of indigenous peoples that depend on the species, and the multi

  9. Co-infection alters population dynamics of infectious disease.

    PubMed

    Susi, Hanna; Barrès, Benoit; Vale, Pedro F; Laine, Anna-Liisa

    2015-01-01

    Co-infections by multiple pathogen strains are common in the wild. Theory predicts co-infections to have major consequences for both within- and between-host disease dynamics, but data are currently scarce. Here, using common garden populations of Plantago lanceolata infected by two strains of the pathogen Podosphaera plantaginis, either singly or under co-infection, we find the highest disease prevalence in co-infected treatments both at the host genotype and population levels. A spore-trapping experiment demonstrates that co-infected hosts shed more transmission propagules than singly infected hosts, thereby explaining the observed change in epidemiological dynamics. Our experimental findings are confirmed in natural pathogen populations-more devastating epidemics were measured in populations with higher levels of co-infection. Jointly, our results confirm the predictions made by theoretical and experimental studies for the potential of co-infection to alter disease dynamics across a large host-pathogen metapopulation. PMID:25569306

  10. Reconstructing local population dynamics in noisy metapopulations--the role of random catastrophes and Allee effects.

    PubMed

    Hart, Edmund M; Avilés, Leticia

    2014-01-01

    Reconstructing the dynamics of populations is complicated by the different types of stochasticity experienced by populations, in particular if some forms of stochasticity introduce bias in parameter estimation in addition to error. Identification of systematic biases is critical when determining whether the intrinsic dynamics of populations are stable or unstable and whether or not populations exhibit an Allee effect, i.e., a minimum size below which deterministic extinction should follow. Using a simulation model that allows for Allee effects and a range of intrinsic dynamics, we investigated how three types of stochasticity--demographic, environmental, and random catastrophes--affect our ability to reconstruct the intrinsic dynamics of populations. Demographic stochasticity aside, which is only problematic in small populations, we find that environmental stochasticity--positive and negative environmental fluctuations--caused increased error in parameter estimation, but bias was rarely problematic, except at the highest levels of noise. Random catastrophes, events causing large-scale mortality and likely to be more common than usually recognized, caused immediate bias in parameter estimates, in particular when Allee effects were large. In the latter case, population stability was predicted when endogenous dynamics were actually unstable and the minimum viable population size was overestimated in populations with small or non-existent Allee effects. Catastrophes also generally increased extinction risk, in particular when endogenous Allee effects were large. We propose a method for identifying data points likely resulting from catastrophic events when such events have not been recorded. Using social spider colonies (Anelosimus spp.) as models for populations, we show that after known or suspected catastrophes are accounted for, reconstructed growth parameters are consistent with intrinsic dynamical instability and substantial Allee effects. Our results are

  11. Reconstructing Local Population Dynamics in Noisy Metapopulations—The Role of Random Catastrophes and Allee Effects

    PubMed Central

    Hart, Edmund M.; Avilés, Leticia

    2014-01-01

    Reconstructing the dynamics of populations is complicated by the different types of stochasticity experienced by populations, in particular if some forms of stochasticity introduce bias in parameter estimation in addition to error. Identification of systematic biases is critical when determining whether the intrinsic dynamics of populations are stable or unstable and whether or not populations exhibit an Allee effect, i.e., a minimum size below which deterministic extinction should follow. Using a simulation model that allows for Allee effects and a range of intrinsic dynamics, we investigated how three types of stochasticity—demographic, environmental, and random catastrophes— affect our ability to reconstruct the intrinsic dynamics of populations. Demographic stochasticity aside, which is only problematic in small populations, we find that environmental stochasticity—positive and negative environmental fluctuations—caused increased error in parameter estimation, but bias was rarely problematic, except at the highest levels of noise. Random catastrophes, events causing large-scale mortality and likely to be more common than usually recognized, caused immediate bias in parameter estimates, in particular when Allee effects were large. In the latter case, population stability was predicted when endogenous dynamics were actually unstable and the minimum viable population size was overestimated in populations with small or non-existent Allee effects. Catastrophes also generally increased extinction risk, in particular when endogenous Allee effects were large. We propose a method for identifying data points likely resulting from catastrophic events when such events have not been recorded. Using social spider colonies (Anelosimus spp.) as models for populations, we show that after known or suspected catastrophes are accounted for, reconstructed growth parameters are consistent with intrinsic dynamical instability and substantial Allee effects. Our results are

  12. Is climate change affecting wolf populations in the high Arctic?

    USGS Publications Warehouse

    Mech, L.D.

    2004-01-01

    Global climate change may affect wolves in Canada's High Arctic (80DG N) acting through three trophic levels (vegetation, herbivores, and wolves). A wolf pack dependent on muskoxen and arctic hares in the Eureka area of Ellesmere Island denned and produced pups most years from at least 1986 through 1997. However when summer snow covered vegetation in 1997 and 2000 for the first time since records were kept, halving the herbivore nutrition-replenishment period, muskox and hare numbers dropped drastically, and the area stopped supporting denning wolves through 2003. The unusual weather triggering these events was consistent with global-climate-change phenomena.

  13. Is climate change affecting wolf populations in the high Arctic?

    USGS Publications Warehouse

    Mech, L.D.

    2004-01-01

    Gobal climate change may affect wolves in Canada's High Arctic (80?? N) acting through three trophic levels (vegetation, herbivores, and wolves). A wolf pack dependent on muskoxen and arctic hares in the Eureka area of Ellesmere Island denned and produced pups most years from at least 1986 through 1997. However, when summer snow covered vegetation in 1997 and 2000 for the first time since records were kept, halving the herbivore nutrition-replenishment period, muskox and hare numbers dropped drastically, and the area stopped supporting denning wolves through 2003. The unusual weather triggering these events was consistent with global-climate-change phenomena. ?? 2004 Kluwer Academic Publishers.

  14. Latin America: native populations affected by early onset periodontal disease.

    PubMed

    Nowzari, Hessam; Botero, Javier Enrique

    2011-06-01

    Millions of individuals are affected by early onset periodontal disease in Latin America, a continent that includes more than 20 countries. The decision-makers claim that the disease is not commonly encountered. In 2009, 280,919 authorized immigrants were registered in the United States versus 5,460,000 unauthorized (2,600,000 in California). The objective of the present article is to raise awareness about the high prevalence of the disease among Latin Americans and the good prognosis of preventive measures associated with minimal financial cost. PMID:21823496

  15. Growth dynamics and the evolution of cooperation in microbial populations

    NASA Astrophysics Data System (ADS)

    Cremer, Jonas; Melbinger, Anna; Frey, Erwin

    2012-02-01

    Microbes providing public goods are widespread in nature despite running the risk of being exploited by free-riders. However, the precise ecological factors supporting cooperation are still puzzling. Following recent experiments, we consider the role of population growth and the repetitive fragmentation of populations into new colonies mimicking simple microbial life-cycles. Individual-based modeling reveals that demographic fluctuations, which lead to a large variance in the composition of colonies, promote cooperation. Biased by population dynamics these fluctuations result in two qualitatively distinct regimes of robust cooperation under repetitive fragmentation into groups. First, if the level of cooperation exceeds a threshold, cooperators will take over the whole population. Second, cooperators can also emerge from a single mutant leading to a robust coexistence between cooperators and free-riders. We find frequency and size of population bottlenecks, and growth dynamics to be the major ecological factors determining the regimes and thereby the evolutionary pathway towards cooperation.

  16. A Quantitative Model of Honey Bee Colony Population Dynamics

    PubMed Central

    Khoury, David S.; Myerscough, Mary R.; Barron, Andrew B.

    2011-01-01

    Since 2006 the rate of honey bee colony failure has increased significantly. As an aid to testing hypotheses for the causes of colony failure we have developed a compartment model of honey bee colony population dynamics to explore the impact of different death rates of forager bees on colony growth and development. The model predicts a critical threshold forager death rate beneath which colonies regulate a stable population size. If death rates are sustained higher than this threshold rapid population decline is predicted and colony failure is inevitable. The model also predicts that high forager death rates draw hive bees into the foraging population at much younger ages than normal, which acts to accelerate colony failure. The model suggests that colony failure can be understood in terms of observed principles of honey bee population dynamics, and provides a theoretical framework for experimental investigation of the problem. PMID:21533156

  17. Uncovering the transmission dynamics of Plasmodium vivax using population genetics

    PubMed Central

    Barry, Alyssa E.; Waltmann, Andreea; Koepfli, Cristian; Barnadas, Celine; Mueller, Ivo

    2015-01-01

    Population genetic analysis of malaria parasites has the power to reveal key insights into malaria epidemiology and transmission dynamics with the potential to deliver tools to support control and elimination efforts. Analyses of parasite genetic diversity have suggested that Plasmodium vivax populations are more genetically diverse and less structured than those of Plasmodium falciparum indicating that P. vivax may be a more ancient parasite of humans and/or less susceptible to population bottlenecks, as well as more efficient at disseminating its genes. These population genetic insights into P. vivax transmission dynamics provide an explanation for its relative resilience to control efforts. Here, we describe current knowledge on P. vivax population genetic structure, its relevance to understanding transmission patterns and relapse and how this information can inform malaria control and elimination programmes. PMID:25891915

  18. Generational Spreading Speed and the Dynamics of Population Range Expansion.

    PubMed

    Bateman, Andrew W; Neubert, Michael G; Krkošek, Martin; Lewis, Mark A

    2015-09-01

    Some of the most fundamental quantities in population ecology describe the growth and spread of populations. Population dynamics are often characterized by the annual rate of increase, λ, or the generational rate of increase, R0. Analyses involving R0 have deepened our understanding of disease dynamics and life-history complexities beyond that afforded by analysis of annual growth alone. While range expansion is quantified by the annual spreading speed, a spatial analog of λ, an R0-like expression for the rate of spread is missing. Using integrodifference models, we derive the appropriate generational spreading speed for populations with complex (stage-structured) life histories. The resulting measure, relevant to locations near the expanding edge of a (re)colonizing population, incorporates both local population growth and explicit spatial dispersal rather than solely growth across a population, as is the case for R0. The calculations for generational spreading speed are often simpler than those for annual spreading speed, and analytic or partial analytic solutions can yield insight into the processes that facilitate or slow a population's spatial spread. We analyze the spatial dynamics of green crabs, sea otters, and teasel as examples to demonstrate the flexibility of our methods and the intuitive insights that they afford. PMID:26655354

  19. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... populations. 230.75 Section 230.75 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  20. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... populations. 230.75 Section 230.75 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  1. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... populations. 230.75 Section 230.75 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  2. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... populations. 230.75 Section 230.75 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  3. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... populations. 230.75 Section 230.75 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  4. Factors affecting minority population proximity to hazardous facilities

    SciTech Connect

    Nieves, L.A.; Nieves, A.L. |

    1995-04-01

    Disproportionate exposure of minority groups to environmental hazards has been attributed to ``environmental racism`` by some authors, without systematic investigation of the factors underlying this exposure pattern. This study examines regional differences in the proximity of African-Americans, Hispanics, Asians, and non-Hispanic Whites to a broad range of facility types and explores the effects of urban and income factors. A statistically significant inverse relationship is found between the percentage of non-Hispanic Whites and virtually all facility categories in all regions. Except for Hispanics in the South, all such associations for minority groups show a direct relationship, though some are nonsignificant. The geographic concentration of facilities is more closely tied to urbanization than to economic factors. Controlling for both urban and economic factors, minority population concentration is still a significant explanatory variable for some facility types in some regions. This finding is most consistent for African-Americans.

  5. A hierarchical state space approach to affective dynamics

    PubMed Central

    Lodewyckx, Tom; Tuerlinckx, Francis; Kuppens, Peter; Allen, Nicholas; Sheeber, Lisa

    2010-01-01

    Linear dynamical system theory is a broad theoretical framework that has been applied in various research areas such as engineering, econometrics and recently in psychology. It quantifies the relations between observed inputs and outputs that are connected through a set of latent state variables. State space models are used to investigate the dynamical properties of these latent quantities. These models are especially of interest in the study of emotion dynamics, with the system representing the evolving emotion components of an individual. However, for simultaneous modeling of individual and population differences, a hierarchical extension of the basic state space model is necessary. Therefore, we introduce a Bayesian hierarchical model with random effects for the system parameters. Further, we apply our model to data that were collected using the Oregon adolescent interaction task: 66 normal and 67 depressed adolescents engaged in a conflict interaction with their parents and second-to-second physiological and behavioral measures were obtained. System parameters in normal and depressed adolescents were compared, which led to interesting discussions in the light of findings in recent literature on the links between cardiovascular processes, emotion dynamics and depression. We illustrate that our approach is flexible and general: The model can be applied to any time series for multiple systems (where a system can represent any entity) and moreover, one is free to focus on whatever component of the versatile model. PMID:21516216

  6. Estimating Traveler Populations at Airport and Cruise Terminals for Population Distribution and Dynamics

    SciTech Connect

    Jochem, Warren C; Sims, Kelly M; Bright, Eddie A; Urban, Marie L; Rose, Amy N; Coleman, Phil R; Bhaduri, Budhendra L

    2013-01-01

    In recent years, uses of high-resolution population distribution databases are increasing steadily for environmental, socioeconomic, public health, and disaster-related research and operations. With the development of daytime population distribution, temporal resolution of such databases has been improved. However, the lack of incorporation of transitional population, namely business and leisure travelers, leaves a significant population unaccounted for within the critical infrastructure networks, such as at transportation hubs. This paper presents two general methodologies for estimating passenger populations in airport and cruise port terminals at a high temporal resolution which can be incorporated into existing population distribution models. The methodologies are geographically scalable and are based on, and demonstrate how, two different transportation hubs with disparate temporal population dynamics can be modeled utilizing publicly available databases including novel data sources of flight activity from the Internet which are updated in near-real time. The airport population estimation model shows great potential for rapid implementation for a large collection of airports on a national scale, and the results suggest reasonable accuracy in the estimated passenger traffic. By incorporating population dynamics at high temporal resolutions into population distribution models, we hope to improve the estimates of populations exposed to or at risk to disasters, thereby improving emergency planning and response, and leading to more informed policy decisions.

  7. Source population characteristics affect heterosis following genetic rescue of fragmented plant populations

    PubMed Central

    Pickup, M.; Field, D. L.; Rowell, D. M.; Young, A. G.

    2013-01-01

    Understanding the relative importance of heterosis and outbreeding depression over multiple generations is a key question in evolutionary biology and is essential for identifying appropriate genetic sources for population and ecosystem restoration. Here we use 2455 experimental crosses between 12 population pairs of the rare perennial plant Rutidosis leptorrhynchoides (Asteraceae) to investigate the multi-generational (F1, F2, F3) fitness outcomes of inter-population hybridization. We detected no evidence of outbreeding depression, with inter-population hybrids and backcrosses showing either similar fitness or significant heterosis for fitness components across the three generations. Variation in heterosis among population pairs was best explained by characteristics of the foreign source or home population, and was greatest when the source population was large, with high genetic diversity and low inbreeding, and the home population was small and inbred. Our results indicate that the primary consideration for maximizing progeny fitness following population augmentation or restoration is the use of seed from large, genetically diverse populations. PMID:23173202

  8. Strongly Deterministic Population Dynamics in Closed Microbial Communities

    NASA Astrophysics Data System (ADS)

    Frentz, Zak; Kuehn, Seppe; Leibler, Stanislas

    2015-10-01

    Biological systems are influenced by random processes at all scales, including molecular, demographic, and behavioral fluctuations, as well as by their interactions with a fluctuating environment. We previously established microbial closed ecosystems (CES) as model systems for studying the role of random events and the emergent statistical laws governing population dynamics. Here, we present long-term measurements of population dynamics using replicate digital holographic microscopes that maintain CES under precisely controlled external conditions while automatically measuring abundances of three microbial species via single-cell imaging. With this system, we measure spatiotemporal population dynamics in more than 60 replicate CES over periods of months. In contrast to previous studies, we observe strongly deterministic population dynamics in replicate systems. Furthermore, we show that previously discovered statistical structure in abundance fluctuations across replicate CES is driven by variation in external conditions, such as illumination. In particular, we confirm the existence of stable ecomodes governing the correlations in population abundances of three species. The observation of strongly deterministic dynamics, together with stable structure of correlations in response to external perturbations, points towards a possibility of simple macroscopic laws governing microbial systems despite numerous stochastic events present on microscopic levels.

  9. Population dynamics: Social security, markets, and families

    PubMed Central

    Lee, Ronald D.; Lee, Sang-Hyop

    2015-01-01

    Upward intergenerational flows – from the working ages to old age – are increasing substantially in the advanced industrialized countries and are much larger than in developing countries. Population aging is the most important factor leading to this change. Thus, in the absence of a major demographic shift, e.g., a return to high fertility, an increase in upward flows is inevitable. Even so, three other important factors will influence the magnitudes of upward flows. First, labor income varies at older ages due to differences in average age at retirement, productivity, unemployment, and hours worked. Second, the age patterns of consumption at older ages vary primarily due to differences in spending on health. Third, spending on human capital, i.e., spending child health and education, varies. Human capital spending competes with spending on the elderly, but it also increases the productivity of subsequent generations of workers and the resources available to support consumption in old age. All contemporary societies rely on a variety of institutions and economic mechanisms to shift economic resources from the working ages to the dependent ages – the young and the old. Three institutions dominate intergenerational flows: governments which implement social security, education, and other public transfer programs; markets which are key to the accumulation of assets, e.g., funded pensions and housing; and families which provide economic support to children in all societies and to the elderly in many. The objectives of this paper are, first, to describe how population aging and other changes influence the direction and magnitude of intergenerational flows; and, second, to contrast the institutional approaches to intergenerational flows as they are practiced around the world. The paper relies extensively on National Transfer Accounts, a system for measuring economic flows across age in a manner consistent with the UN System of National Accounts. These accounts are

  10. Inferences about ungulate population dynamics derived from age ratios

    USGS Publications Warehouse

    Harris, N.C.; Kauffman, M.J.; Mills, L.S.

    2008-01-01

    Age ratios (e.g., calf:cow for elk and fawn:doe for deer) are used regularly to monitor ungulate populations. However, it remains unclear what inferences are appropriate from this index because multiple vital rate changes can influence the observed ratio. We used modeling based on elk (Cervus elaphus) life-history to evaluate both how age ratios are influenced by stage-specific fecundity and survival and how well age ratios track population dynamics. Although all vital rates have the potential to influence calf:adult female ratios (i.e., calf:xow ratios), calf survival explained the vast majority of variation in calf:adult female ratios due to its temporal variation compared to other vital rates. Calf:adult female ratios were positively correlated with population growth rate (??) and often successfully indicated population trajectories. However, calf:adult female ratios performed poorly at detecting imposed declines in calf survival, suggesting that only the most severe declines would be rapidly detected. Our analyses clarify that managers can use accurate, unbiased age ratios to monitor arguably the most important components contributing to sustainable ungulate populations, survival rate of young and ??. However, age ratios are not useful for detecting gradual declines in survival of young or making inferences about fecundity or adult survival in ungulate populations. Therefore, age ratios coupled with independent estimates of population growth or population size are necessary to monitor ungulate population demography and dynamics closely through time.

  11. A general method for modeling population dynamics and its applications.

    PubMed

    Shestopaloff, Yuri K

    2013-12-01

    Studying populations, be it a microbe colony or mankind, is important for understanding how complex systems evolve and exist. Such knowledge also often provides insights into evolution, history and different aspects of human life. By and large, populations' prosperity and decline is about transformation of certain resources into quantity and other characteristics of populations through growth, replication, expansion and acquisition of resources. We introduce a general model of population change, applicable to different types of populations, which interconnects numerous factors influencing population dynamics, such as nutrient influx and nutrient consumption, reproduction period, reproduction rate, etc. It is also possible to take into account specific growth features of individual organisms. We considered two recently discovered distinct growth scenarios: first, when organisms do not change their grown mass regardless of nutrients availability, and the second when organisms can reduce their grown mass by several times in a nutritionally poor environment. We found that nutrient supply and reproduction period are two major factors influencing the shape of population growth curves. There is also a difference in population dynamics between these two groups. Organisms belonging to the second group are significantly more adaptive to reduction of nutrients and far more resistant to extinction. Also, such organisms have substantially more frequent and lesser in amplitude fluctuations of population quantity for the same periodic nutrient supply (compared to the first group). Proposed model allows adequately describing virtually any possible growth scenario, including complex ones with periodic and irregular nutrient supply and other changing parameters, which present approaches cannot do. PMID:24057917

  12. Have historical climate changes affected Gentoo penguin (Pygoscelis papua) populations in Antarctica?

    PubMed

    Peña M, Fabiola; Poulin, Elie; Dantas, Gisele P M; González-Acuña, Daniel; Petry, Maria Virginia; Vianna, Juliana A

    2014-01-01

    The West Antarctic Peninsula (WAP) has been suffering an increase in its atmospheric temperature during the last 50 years, mainly associated with global warming. This increment of temperature trend associated with changes in sea-ice dynamics has an impact on organisms, affecting their phenology, physiology and distribution range. For instance, rapid demographic changes in Pygoscelis penguins have been reported over the last 50 years in WAP, resulting in population expansion of sub-Antarctic Gentoo penguin (P. papua) and retreat of Antarctic Adelie penguin (P. adeliae). Current global warming has been mainly associated with human activities; however these climate trends are framed in a historical context of climate changes, particularly during the Pleistocene, characterized by an alternation between glacial and interglacial periods. During the last maximal glacial (LGM∼21,000 BP) the ice sheet cover reached its maximum extension on the West Antarctic Peninsula (WAP), causing local extinction of Antarctic taxa, migration to lower latitudes and/or survival in glacial refugia. We studied the HRVI of mtDNA and the nuclear intron βfibint7 of 150 individuals of the WAP to understand the demographic history and population structure of P. papua. We found high genetic diversity, reduced population genetic structure and a signature of population expansion estimated around 13,000 BP, much before the first paleocolony fossil records (∼1,100 BP). Our results suggest that the species may have survived in peri-Antarctic refugia such as South Georgia and North Sandwich islands and recolonized the Antarctic Peninsula and South Shetland Islands after the ice sheet retreat. PMID:24759777

  13. Have Historical Climate Changes Affected Gentoo Penguin (Pygoscelis papua) Populations in Antarctica?

    PubMed Central

    Peña M., Fabiola; Poulin, Elie; Dantas, Gisele P. M.; González-Acuña, Daniel; Petry, Maria Virginia; Vianna, Juliana A.

    2014-01-01

    The West Antarctic Peninsula (WAP) has been suffering an increase in its atmospheric temperature during the last 50 years, mainly associated with global warming. This increment of temperature trend associated with changes in sea-ice dynamics has an impact on organisms, affecting their phenology, physiology and distribution range. For instance, rapid demographic changes in Pygoscelis penguins have been reported over the last 50 years in WAP, resulting in population expansion of sub-Antarctic Gentoo penguin (P. papua) and retreat of Antarctic Adelie penguin (P. adeliae). Current global warming has been mainly associated with human activities; however these climate trends are framed in a historical context of climate changes, particularly during the Pleistocene, characterized by an alternation between glacial and interglacial periods. During the last maximal glacial (LGM∼21,000 BP) the ice sheet cover reached its maximum extension on the West Antarctic Peninsula (WAP), causing local extinction of Antarctic taxa, migration to lower latitudes and/or survival in glacial refugia. We studied the HRVI of mtDNA and the nuclear intron βfibint7 of 150 individuals of the WAP to understand the demographic history and population structure of P. papua. We found high genetic diversity, reduced population genetic structure and a signature of population expansion estimated around 13,000 BP, much before the first paleocolony fossil records (∼1,100 BP). Our results suggest that the species may have survived in peri-Antarctic refugia such as South Georgia and North Sandwich islands and recolonized the Antarctic Peninsula and South Shetland Islands after the ice sheet retreat. PMID:24759777

  14. Dynamics of Sequence -Discrete Bacterial Populations Inferred Using Metagenomes

    SciTech Connect

    Stevens, Sarah; Bendall, Matthew; Kang, Dongwan; Froula, Jeff; Egan, Rob; Chan, Leong-Keat; Tringe, Susannah; McMahon, Katherine; Malmstrom, Rex

    2014-03-14

    From a multi-year metagenomic time series of two dissimilar Wisconsin lakes we have assembled dozens of genomes using a novel approach that bins contigs into distinct genome based on sequence composition, e.g. kmer frequencies, and contig coverage patterns at various times points. Next, we investigated how these genomes, which represent sequence-discrete bacterial populations, evolved over time and used the time series to discover the population dynamics. For example, we explored changes in single nucleotide polymorphism (SNP) frequencies as well as patterns of gene gain and loss in multiple populations. Interestingly, SNP diversity was purged at nearly every genome position in some populations during the course of this study, suggesting these populations may have experienced genome-wide selective sweeps. This represents the first direct, time-resolved observations of periodic selection in natural populations, a key process predicted by the ecotype model of bacterial diversification.

  15. Real-Time Bioluminescent Tracking of Cellular Population Dynamics

    SciTech Connect

    Close, Dan; Sayler, Gary Steven; Xu, Tingting; Ripp, Steven Anthony

    2014-01-01

    Cellular population dynamics are routinely monitored across many diverse fields for a variety of purposes. In general, these dynamics are assayed either through the direct counting of cellular aliquots followed by extrapolation to the total population size, or through the monitoring of signal intensity from any number of externally stimulated reporter proteins. While both viable methods, here we describe a novel technique that allows for the automated, non-destructive tracking of cellular population dynamics in real-time. This method, which relies on the detection of a continuous bioluminescent signal produced through expression of the bacterial luciferase gene cassette, provides a low cost, low time-intensive means for generating additional data compared to alternative methods.

  16. Dynamics and recovery of a sediment-exposed Chironomus riparius population: A modelling approach.

    PubMed

    Diepens, Noël J; Beltman, Wim H J; Koelmans, Albert A; Van den Brink, Paul J; Baveco, Johannes M

    2016-06-01

    Models can be used to assess long-term risks of sediment-bound contaminants at the population level. However, these models usually lack the coupling between chemical fate in the sediment, toxicokinetic-toxicodynamic processes in individuals and propagation of individual-level effects to the population. We developed a population model that includes all these processes, and used it to assess the importance of chemical uptake routes on a Chironomus riparius population after pulsed exposure to the pesticide chlorpyrifos. We show that particle ingestion is an important additional exposure pathway affecting C. riparius population dynamics and recovery. Models ignoring particle ingestion underestimate the impact and the required recovery times, which implies that they underestimate risks of sediment-bound chemicals. Additional scenario studies showed the importance of selecting the biologically relevant sediment layer and showed population effects in the long term. PMID:27031571

  17. Complex Population Dynamics in Mussels Arising from Density-Linked Stochasticity

    PubMed Central

    Wootton, J. Timothy; Forester, James D.

    2013-01-01

    Population fluctuations are generally attributed to the deterministic consequences of strong non-linear interactions among organisms, or the effects of random stochastic environmental variation superimposed upon the deterministic skeleton describing population change. Analysis of the population dynamics of the mussel Mytilus californianus taken in 16 plots over 18-years found no evidence that these processes explained observed strong fluctuations. Instead, population fluctuations arose because environmental stochasticity varied with abundance, which we term density-linked stochasticity. This phenomenon arises from biologically relevant mechanisms: recruitment variation and transmission of disturbance among neighboring individuals. Density-linked stochasticity is probably present frequently in populations, as it arises naturally from several general ecological processes, including stage structure variation with density, ontogenetic niche shifts, and local transmission of stochastic perturbations. More thoroughly characterizing and interpreting deviations from the mean behavior of a system will lead to better ecological prediction and improved insight into the important processes affecting populations and ecosystems. PMID:24086617

  18. Simulation of mosquitoes population dynamic based on rainfall and average daily temperature

    NASA Astrophysics Data System (ADS)

    Widayani, H.; Seprianus, Nuraini, N.; Arum, J.

    2014-02-01

    This paper proposed rainfall and average daily temperature approximation functions using least square method with trigonometry polynomial. Error value from this method is better than Fast Fourier Transform method. This approximation is used to accommodate climatic factors into deterministic model of mosquitoes population by constructing a carrying capacity function which contains rainfall and average daily temperature functions. We develop a mathematical model for mosquitoes population dynamic which formulated by Yang et al (2010) with dynamic parameter of a daily rainfall as well as temperature on that model. Two fixed points, trivial and non-trivial, are obtained when constant entomological parameters assumed. Basic offspring number, Q0 as mosquitoes reproduction parameter is constructed. Non-trivial fixed point is stable if and only if Q0 > 1. Numerical simulation shown the dynamics of mosquitoes population significantly affected by rainfall and average daily temperature function.

  19. Network evolution induced by the dynamical rules of two populations

    NASA Astrophysics Data System (ADS)

    Platini, Thierry; Zia, R. K. P.

    2010-10-01

    We study the dynamical properties of a finite dynamical network composed of two interacting populations, namely extrovert (a) and introvert (b). In our model, each group is characterized by its size (Na and Nb) and preferred degree (κa and \\kappa_b\\ll \\kappa_a ). The network dynamics is governed by the competing microscopic rules of each population that consist of the creation and destruction of links. Starting from an unconnected network, we give a detailed analysis of the mean field approach which is compared to Monte Carlo simulation data. The time evolution of the restricted degrees langkbbrang and langkabrang presents three time regimes and a non-monotonic behavior well captured by our theory. Surprisingly, when the population sizes are equal Na = Nb, the ratio of the restricted degree θ0 = langkabrang/langkbbrang appears to be an integer in the asymptotic limits of the three time regimes. For early times (defined by t < t1 = κb) the total number of links presents a linear evolution, where the two populations are indistinguishable and where θ0 = 1. Interestingly, in the intermediate time regime (defined for t_1\\lt t\\lt t_2\\propto \\kappa_a and for which θ0 = 5), the system reaches a transient stationary state, where the number of contacts among introverts remains constant while the number of connections increases linearly in the extrovert population. Finally, due to the competing dynamics, the network presents a frustrated stationary state characterized by a ratio θ0 = 3.

  20. Population Dynamics with Global Regulation: The Conserved Fisher Equation

    NASA Astrophysics Data System (ADS)

    Newman, T. J.; Kolomeisky, E. B.; Antonovics, J.

    2004-06-01

    We introduce and study a conserved version of the Fisher equation. Within a population biology context, this model describes spatially extended populations in which the total number of individuals is fixed due to either biotic or environmental factors. We find a rich spectrum of dynamical phases including a pseudotraveling wave and, in the presence of the Allee effect, a phase transition from a locally constrained high density state to a low density fragmented state.

  1. Evolutionary History and Population Dynamics of Hepatitis E Virus

    PubMed Central

    Purdy, Michael A.; Khudyakov, Yury E.

    2010-01-01

    Background Hepatitis E virus (HEV) is an enterically transmitted hepatropic virus. It segregates as four genotypes. All genotypes infect humans while only genotypes 3 and 4 also infect several animal species. It has been suggested that hepatitis E is zoonotic, but no study has analyzed the evolutionary history of HEV. We present here an analysis of the evolutionary history of HEV. Methods and Findings The times to the most recent common ancestors for all four genotypes of HEV were calculated using BEAST to conduct a Bayesian analysis of HEV. The population dynamics for genotypes 1, 3 and 4 were analyzed using skyline plots. Bayesian analysis showed that the most recent common ancestor for modern HEV existed between 536 and 1344 years ago. The progenitor of HEV appears to have given rise to anthropotropic and enzootic forms of HEV, which evolved into genotypes 1 and 2 and genotypes 3 and 4, respectively. Population dynamics suggest that genotypes 1, 3 and 4 experienced a population expansion during the 20th century. Genotype 1 has increased in infected population size ∼30–35 years ago. Genotype 3 and 4 have experienced an increase in population size starting late in the 19th century until ca.1940-45, with genotype 3 having undergone additional rapid expansion until ca.1960. The effective population size for both genotype 3 and 4 rapidly declined to pre-expansion levels starting in ca.1990. Genotype 4 was further examined as Chinese and Japanese sequences, which exhibited different population dynamics, suggesting that this genotype experienced different evolutionary history in these two countries. Conclusions HEV appears to have evolved through a series of steps, in which the ancestors of HEV may have adapted to a succession of animal hosts leading to humans. Analysis of the population dynamics of HEV suggests a substantial temporal variation in the rate of transmission among HEV genotypes in different geographic regions late in the 20th Century. PMID:21203540

  2. An Individual-Based Model of Zebrafish Population Dynamics Accounting for Energy Dynamics

    PubMed Central

    Beaudouin, Rémy; Goussen, Benoit; Piccini, Benjamin; Augustine, Starrlight; Devillers, James; Brion, François; Péry, Alexandre R. R.

    2015-01-01

    Developing population dynamics models for zebrafish is crucial in order to extrapolate from toxicity data measured at the organism level to biological levels relevant to support and enhance ecological risk assessment. To achieve this, a dynamic energy budget for individual zebrafish (DEB model) was coupled to an individual based model of zebrafish population dynamics (IBM model). Next, we fitted the DEB model to new experimental data on zebrafish growth and reproduction thus improving existing models. We further analysed the DEB-model and DEB-IBM using a sensitivity analysis. Finally, the predictions of the DEB-IBM were compared to existing observations on natural zebrafish populations and the predicted population dynamics are realistic. While our zebrafish DEB-IBM model can still be improved by acquiring new experimental data on the most uncertain processes (e.g. survival or feeding), it can already serve to predict the impact of compounds at the population level. PMID:25938409

  3. Understanding long-term fruit fly (Diptera: Tephritidae) population dynamics: implications for areawide management.

    PubMed

    Aluja, Martín; Ordano, Mariano; Guillén, Larissa; Rull, Juan

    2012-06-01

    Fruit flies (Diptera: Tephritidae) are devastating agricultural pests worldwide but studies on their long-term population dynamics are sparse. Our aim was to determine the mechanisms driving long-term population dynamics as a prerequisite for ecologically based areawide pest management. The population density of three pestiferous Anastrepha species [Anastrepha ludens (Loew), Anastrepha obliqua (Macquart), and Anastrepha serpentina (Wiedemann)] was determined in grapefruit (Citrus x paradisi Macfad.), mango (Mangifera indica L.), and sapodilla [Manilkara zapota (L.) P. Royen] orchards in central Veracruz, México, on a weekly basis over an 11-yr period. Fly populations exhibited relatively stable dynamics over time. Population dynamics were mainly driven by a direct density-dependent effect and a seasonal feedback process. We discovered direct and delayed influences that were correlated with both local (rainfall and air temperature) and global climatic variation (El Niño Southern Oscillation [ENSO] and North Atlantic Oscillation [NAO]), and detected differences among species and location of orchards with respect to the magnitude and nature (linear or nonlinear) of the observed effects, suggesting that highly mobile pest outbreaks become uncertain in response to significant climatic events at both global and local levels. That both NAO and ENSO affected Anastrepha population dynamics, coupled with the high mobility of Anastrepha adults and the discovery that when measured as rate of population change, local population fluctuations exhibited stable dynamics over time, suggests potential management scenarios for the species studied lie beyond the local scale and should be approached from an areawide perspective. Localized efforts, from individual growers will probably prove ineffective, and nonsustainable. PMID:22812118

  4. Single-cell variation leads to population invariance in NF-κB signaling dynamics

    PubMed Central

    Hughey, Jacob J.; Gutschow, Miriam V.; Bajar, Bryce T.; Covert, Markus W.

    2015-01-01

    The activation dynamics of nuclear factor (NF)-κB have been shown to affect downstream gene expression. On activation, NF-κB shuttles back and forth across the nuclear envelope. Many dynamic features of this shuttling have been characterized, and most features vary significantly with respect to ligand type and concentration. Here, we report an invariant feature with regard to NF-κB dynamics in cellular populations: the distribution—the average, as well as the variance—of the time between two nuclear entries (the period). We find that this period is conserved, regardless of concentration and across several different ligands. Intriguingly, the distributions observed at the population level are not observed in individual cells over 20-h time courses. Instead, the average period of NF-κB nuclear translocation varies considerably among single cells, and the variance is much smaller within a cell than that of the population. Finally, analysis of daughter-cell pairs and isogenic populations indicates that the dynamics of the NF-κB response is heritable but diverges over multiple divisions, on the time scale of weeks to months. These observations are contrary to the existing theory of NF-κB dynamics and suggest an additional level of control that regulates the overall distribution of translocation timing at the population level. PMID:25473117

  5. Population and Evolutionary Dynamics based on Predator-Prey Relationships in a 3D Physical Simulation.

    PubMed

    Ito, Takashi; Pilat, Marcin L; Suzuki, Reiji; Arita, Takaya

    2016-01-01

    Recent studies have reported that population dynamics and evolutionary dynamics, occurring at different time scales, can be affected by each other. Our purpose is to explore the interaction between population and evolutionary dynamics using an artificial life approach based on a 3D physically simulated environment in the context of predator-prey and morphology-behavior coevolution. The morphologies and behaviors of virtual prey creatures are evolved using a genetic algorithm based on the predation interactions between predators and prey. Both population sizes are also changed, depending on the fitness. We observe two types of cyclic behaviors, corresponding to short-term and long-term dynamics. The former can be interpreted as a simple population dynamics of Lotka-Volterra type. It is shown that the latter cycle is based on the interaction between the changes in the prey strategy against predators and the long-term change in both population sizes, resulting partly from a tradeoff between their defensive success and the cost of defense. PMID:26934093

  6. Ecological change predicts population dynamics and genetic diversity over 120 000 years.

    PubMed

    Horreo, Jose Luis; Jiménez-Valverde, Alberto; Fitze, Patrick S

    2016-05-01

    While ecological effects on short-term population dynamics are well understood, their effects over millennia are difficult to demonstrate and convincing evidence is scant. Using coalescent methods, we analysed past population dynamics of three lizard species (Psammodromus hispanicus, P. edwardsianus, P. occidentalis) and linked the results with climate change data covering the same temporal horizon (120 000 years). An increase in population size over time was observed in two species, and in P. occidentalis, no change was observed. Temporal changes in temperature seasonality and the maximum temperature of the warmest month were congruent with changes in population dynamics observed for the three species and both variables affected population density, either directly or indirectly (via a life-history trait). These results constitute the first solid link between ecological change and long-term population dynamics. The results moreover suggest that ecological change leaves genetic signatures that can be retrospectively traced, providing evidence that ecological change is a crucial driver of genetic diversity and speciation. PMID:26666533

  7. A dynamic traffic simulator for roads affected by natural hasards

    NASA Astrophysics Data System (ADS)

    Voumard, J.; Jaboyedoff, M.; Derron, M.-H.

    2012-04-01

    This work focuses on the issue of natural hazards threatening roads. Nowadays, risk estimations of rock falls or landslides affecting whole sections of road are generally quite accurate and under relatively good control. Mitigation measures provide intervention means to reduce the hazards along roads. However, as classical models of risk calculation on communication routes do not take into account the dynamic traffic parameters, little is known on the way of reducing the risk at road level. It is not known precisely what really happens on the road when an event occurs and how vehicles interact. A dynamic traffic simulator in development provides information on factors having an impact on the risk level related to the road. Variables such as visibility, curvature radius of turns or vehicle type were included in the model. Varying these variables within dynamic traffic simulations can suggest solutions to minimize the risks for road users. These simulations can provide answers to various questions, such as: does speed have a significant impact on the risk incurred by drivers? Is it possible to significantly reduce the risk with appropriate speeds? The simulation is performed with the MATLAB © software. The model is yet to be calibrated and validated through in situ tests.

  8. Dynamic regimes of local homogeneous population model with time lag

    NASA Astrophysics Data System (ADS)

    Neverova, Galina; Frisman, Efim

    2016-06-01

    We investigated Moran - Ricker model with time lag 1. It is made analytical and numerical study of the model. It is shown there is co-existence of various dynamic regimes under the same values of parameters. The model simultaneously possesses several different limit regimes: stable state, periodic fluctuations, and chaotic attractor. The research results show if present population size substantially depends on population number of previous year then it is observed quasi-periodic oscillations. Fluctuations with period 2 occur when the growth of population size is regulated by density dependence in the current year.

  9. Disentangling seasonal bacterioplankton population dynamics by high-frequency sampling.

    PubMed

    Lindh, Markus V; Sjöstedt, Johanna; Andersson, Anders F; Baltar, Federico; Hugerth, Luisa W; Lundin, Daniel; Muthusamy, Saraladevi; Legrand, Catherine; Pinhassi, Jarone

    2015-07-01

    Multiyear comparisons of bacterioplankton succession reveal that environmental conditions drive community shifts with repeatable patterns between years. However, corresponding insight into bacterioplankton dynamics at a temporal resolution relevant for detailed examination of variation and characteristics of specific populations within years is essentially lacking. During 1 year, we collected 46 samples in the Baltic Sea for assessing bacterial community composition by 16S rRNA gene pyrosequencing (nearly twice weekly during productive season). Beta-diversity analysis showed distinct clustering of samples, attributable to seemingly synchronous temporal transitions among populations (populations defined by 97% 16S rRNA gene sequence identity). A wide spectrum of bacterioplankton dynamics was evident, where divergent temporal patterns resulted both from pronounced differences in relative abundance and presence/absence of populations. Rates of change in relative abundance calculated for individual populations ranged from 0.23 to 1.79 day(-1) . Populations that were persistently dominant, transiently abundant or generally rare were found in several major bacterial groups, implying evolution has favoured a similar variety of life strategies within these groups. These findings suggest that high temporal resolution sampling allows constraining the timescales and frequencies at which distinct populations transition between being abundant or rare, thus potentially providing clues about physical, chemical or biological forcing on bacterioplankton community structure. PMID:25403576

  10. Bacterial associations reveal spatial population dynamics in Anopheles gambiae mosquitoes.

    PubMed

    Buck, Moritz; Nilsson, Louise K J; Brunius, Carl; Dabiré, Roch K; Hopkins, Richard; Terenius, Olle

    2016-01-01

    The intolerable burden of malaria has for too long plagued humanity and the prospect of eradicating malaria is an optimistic, but reachable, target in the 21(st) century. However, extensive knowledge is needed about the spatial structure of mosquito populations in order to develop effective interventions against malaria transmission. We hypothesized that the microbiota associated with a mosquito reflects acquisition of bacteria in different environments. By analyzing the whole-body bacterial flora of An. gambiae mosquitoes from Burkina Faso by 16 S amplicon sequencing, we found that the different environments gave each mosquito a specific bacterial profile. In addition, the bacterial profiles provided precise and predicting information on the spatial dynamics of the mosquito population as a whole and showed that the mosquitoes formed clear local populations within a meta-population network. We believe that using microbiotas as proxies for population structures will greatly aid improving the performance of vector interventions around the world. PMID:26960555

  11. Bacterial associations reveal spatial population dynamics in Anopheles gambiae mosquitoes

    PubMed Central

    Buck, Moritz; Nilsson, Louise K. J.; Brunius, Carl; Dabiré, Roch K.; Hopkins, Richard; Terenius, Olle

    2016-01-01

    The intolerable burden of malaria has for too long plagued humanity and the prospect of eradicating malaria is an optimistic, but reachable, target in the 21st century. However, extensive knowledge is needed about the spatial structure of mosquito populations in order to develop effective interventions against malaria transmission. We hypothesized that the microbiota associated with a mosquito reflects acquisition of bacteria in different environments. By analyzing the whole-body bacterial flora of An. gambiae mosquitoes from Burkina Faso by 16 S amplicon sequencing, we found that the different environments gave each mosquito a specific bacterial profile. In addition, the bacterial profiles provided precise and predicting information on the spatial dynamics of the mosquito population as a whole and showed that the mosquitoes formed clear local populations within a meta-population network. We believe that using microbiotas as proxies for population structures will greatly aid improving the performance of vector interventions around the world. PMID:26960555

  12. Dynamics of Two Populations with Different Birth Rates

    NASA Astrophysics Data System (ADS)

    Hoffmann, Julia; Pekalski, Andrzej

    We propose a simple model describing the dynamics of a system of two populations — more numerous natives and less numerous immigrants. The immigrants' birth rate is higher than that of the natives. Several modifications of this model taking into account changes of the birth rates due to external factors and/or possibility of contacts between the populations, are also introduced. The model is studied within two approaches — by solving a set of differential equations and through a Monte Carlo simulations. We show that the question of which population will eventually dominate depends on such factors as the probability of producing offsprings of mixed origin, assimilation of the immigrants, the ratio of the birth rates, initial numbers of the populations and the average age of an individual. In all, but two extreme cases, both populations will survive.

  13. Mastoid Vibration Affects Dynamic Postural Control During Gait.

    PubMed

    Chien, Jung Hung; Mukherjee, Mukul; Stergiou, Nicholas

    2016-09-01

    Our objective was to investigate how manipulating sensory input through mastoid vibration (MV) could affect dynamic postural control during walking, with and without simultaneous manipulation of the visual and the somatosensory systems. We used three levels of MV (none, unilateral, and bilateral) via vibrating elements placed on the mastoid processes. We combined this with the six conditions of the Locomotor Sensory Organization Test (LSOT) paradigm to challenge the visual and somatosensory systems. We hypothesized that MV would affect both amount and temporal structure measures of sway variability during walking and that, in combination with manipulations of the visual and the somatosensory inputs, MV would augment the effects previously observed. The results confirmed that MV produced a significant increase in the amount of sway variability in both anterior-posterior and medial-lateral directions. Significant changes in the temporal structure of sway variability were only observed in the anterior-posterior direction. Bilateral MV produced larger effects than unilateral stimulation. We concluded that sensory input while walking could be affected using MV. Combining MV with manipulations of visual and somatosensory input could allow us to better understand the contributions of the sensory systems during locomotion. PMID:26833038

  14. Human-caused mortality influences spatial population dynamics: pumas in landscapes with varying mortality risks

    USGS Publications Warehouse

    Newby, Jesse R.; Mills, L. Scott; Ruth, Toni K.; Pletscher, Daniel H.; Mitchell, Michael S.; Quigley, Howard B.; Murphy, Kerry M.; DeSimone, Rich

    2013-01-01

    An understanding of how stressors affect dispersal attributes and the contribution of local populations to multi-population dynamics are of immediate value to basic and applied ecology. Puma (Puma concolor) populations are expected to be influenced by inter-population movements and susceptible to human-induced source–sink dynamics. Using long-term datasets we quantified the contribution of two puma populations to operationally define them as sources or sinks. The puma population in the Northern Greater Yellowstone Ecosystem (NGYE) was largely insulated from human-induced mortality by Yellowstone National Park. Pumas in the western Montana Garnet Mountain system were exposed to greater human-induced mortality, which changed over the study due to the closure of a 915 km2 area to hunting. The NGYE’s population growth depended on inter-population movements, as did its ability to act as a source to the larger region. The heavily hunted Garnet area was a sink with a declining population until the hunting closure, after which it became a source with positive intrinsic growth and a 16× increase in emigration. We also examined the spatial and temporal characteristics of individual dispersal attributes (emigration, dispersal distance, establishment success) of subadult pumas (N = 126). Human-caused mortality was found to negatively impact all three dispersal components. Our results demonstrate the influence of human-induced mortality on not only within population vital rates, but also inter-population vital rates, affecting the magnitude and mechanisms of local population’s contribution to the larger metapopulation.

  15. COMPARISON OF SAMPLING TECHNIQUES USED IN STUDYING LEPIDOPTERA POPULATION DYNAMICS

    EPA Science Inventory

    Four methods (light traps, foliage samples, canvas bands, and gypsy moth egg mass surveys) that are used to study the population dynamics of foliage-feeding Lepidoptera were compared for 10 species, including gypsy moth, Lymantria dispar L. Samples were collected weekly at 12 sit...

  16. Binary Populations and Stellar Dynamics in Young Clusters

    NASA Astrophysics Data System (ADS)

    Vanbeveren, D.; Belkus, H.; Van Bever, J.; Mennekens, N.

    2008-06-01

    We first summarize work that has been done on the effects of binaries on theoretical population synthesis of stars and stellar phenomena. Next, we highlight the influence of stellar dynamics in young clusters by discussing a few candidate UFOs (unconventionally formed objects) like intermediate mass black holes, η Car, ζ Pup, γ2 Velorum and WR 140.

  17. Population Dynamics, Demography, Dispersal and Spread of Bemisia tabaci

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bemisia tabaci is an insect pest of global significance. It attacks multiple crops and causes damage through feeding and transmission of plant viruses. This review focuses on the current state of knowledge of the population dynamics, demography and dispersal of this important pest. Sampling metho...

  18. Location of odor sources and the affected population in Imperial County, California

    SciTech Connect

    Hahn, J.L.

    1981-08-01

    This report is divided into four sections. The first two sections contain general background information on Imperial County. The third section is a general discussion of odor sources in Imperial County, and the fourth maps the specific odor sources, the expected areas of perception, and the affected populations. this mapping is done for the Imperial Valley and each of the four Imperial County KGRA's (Known Geothermal Resource Areas) where odor from the development of the geothermal energy may affect population.

  19. Population dynamics and mutualism: Functional responses of benefits and costs

    USGS Publications Warehouse

    Holland, J. Nathaniel; DeAngelis, Donald L.; Bronstein, Judith L.

    2002-01-01

    We develop an approach for studying population dynamics resulting from mutualism by employing functional responses based on density‐dependent benefits and costs. These functional responses express how the population growth rate of a mutualist is modified by the density of its partner. We present several possible dependencies of gross benefits and costs, and hence net effects, to a mutualist as functions of the density of its partner. Net effects to mutualists are likely a monotonically saturating or unimodal function of the density of their partner. We show that fundamental differences in the growth, limitation, and dynamics of a population can occur when net effects to that population change linearly, unimodally, or in a saturating fashion. We use the mutualism between senita cactus and its pollinating seed‐eating moth as an example to show the influence of different benefit and cost functional responses on population dynamics and stability of mutualisms. We investigated two mechanisms that may alter this mutualism's functional responses: distribution of eggs among flowers and fruit abortion. Differences in how benefits and costs vary with density can alter the stability of this mutualism. In particular, fruit abortion may allow for a stable equilibrium where none could otherwise exist.

  20. Evolution of complex dynamics in spatially structured populations

    PubMed Central

    Johst, K.; Doebeli, M.; Brandl, R.

    1999-01-01

    Dynamics of populations depend on demographic parameters which may change during evolution. In simple ecological models given by one-dimensional difference equations, the evolution of demographic parameters generally leads to equilibrium population dynamics. Here we show that this is not true in spatially structured ecological models. Using a multi-patch metapopulation model, we study the evolutionary dynamics of phenotypes that differ both in their response to local crowding, i.e. in their competitive behaviour within a habitat, and in their rate of dispersal between habitats. Our simulation results show that evolution can favour phenotypes that have the intrinsic potential for very complex dynamics provided that the environment is spatially structured and temporally variable. These phenotypes owe their evolutionary persistence to their large dispersal rates. They typically coexist with phenotypes that have low dispersal rates and that exhibit equilibrium dynamics when alone. This coexistence is brought about through the phenomenon of evolutionary branching, during which an initially uniform population splits into the two phenotypic classes.

  1. Conceptualizing the dynamics of a drought affected agricultural community

    NASA Astrophysics Data System (ADS)

    Kuil, Linda; Carr, Gemma; Viglione, Alberto; Bloeschl, Guenter

    2015-04-01

    Climate and especially water availability and variability play an important role in the development of our societies. This can be seen through the vast investments that are made in reaching water security and the economic impact regions experience when the rains fail. However, the limit of available fresh water is increasingly felt as our population increases and the demand for water continues to rise. But how do we as society respond? Are periods of drought making us more resilient? The answer to this question is sought through the development of a stylized model that is built within the spirit of the Easter Island model by Brander and Taylor and aimed at capturing the essence of the dynamics of water supply and demand. By explicitly incorporating feedbacks, but keeping the framework simple, the model seeks to understand qualitative behavior of our socio-hydrological system as opposed to predicting exact pathways. The model shows that carrying capacity dynamics are a determining factor for continued growth. Future work will explore the underlying relationships further, among others, through examination of case studies.

  2. Evolutionary dynamics of group interactions on structured populations: a review

    PubMed Central

    Perc, Matjaž; Gómez-Gardeñes, Jesús; Szolnoki, Attila; Floría, Luis M.; Moreno, Yamir

    2013-01-01

    Interactions among living organisms, from bacteria colonies to human societies, are inherently more complex than interactions among particles and non-living matter. Group interactions are a particularly important and widespread class, representative of which is the public goods game. In addition, methods of statistical physics have proved valuable for studying pattern formation, equilibrium selection and self-organization in evolutionary games. Here, we review recent advances in the study of evolutionary dynamics of group interactions on top of structured populations, including lattices, complex networks and coevolutionary models. We also compare these results with those obtained on well-mixed populations. The review particularly highlights that the study of the dynamics of group interactions, like several other important equilibrium and non-equilibrium dynamical processes in biological, economical and social sciences, benefits from the synergy between statistical physics, network science and evolutionary game theory. PMID:23303223

  3. Population dynamics of the epiphytic bromeliad Tillandsia butzii in cloud forest

    NASA Astrophysics Data System (ADS)

    Toledo-Aceves, Tarin; Hernández-Apolinar, Mariana

    2016-02-01

    Epiphytes are a major component of tropical montane cloud forests. Over-exploitation and forest loss and degradation affect remnant populations. In this study, we analysed the population dynamics of the epiphytic bromeliad Tillandsia butzii over a 2-y period in a tropical montane cloud forest fragment in southern Mexico. Matrix analysis revealed that the T. butzii population is likely to be stable at the study site. On average the λ value did not differ significantly from unity: λ (95% confidence interval) = 0.978 (0.936-1.001). λ was highly influenced by stasis, to a lesser extent by growth and only slightly by fecundity. Overall, adult plant stasis and phalanx growth habit played a fundamental role in population maintenance. T. butzii tolerance to xeric conditions may contribute to population stability in the studied region.

  4. Population dynamics of epiphytic orchids in a metapopulation context

    PubMed Central

    Winkler, Manuela; Hülber, Karl; Hietz, Peter

    2009-01-01

    Background and Aims Populations of many epiphytes show a patchy distribution where clusters of plants growing on individual trees are spatially separated and may thus function as metapopulations. Seed dispersal is necessary to (re)colonize unoccupied habitats, and to transfer seeds from high- to low-competition patches. Increasing dispersal distances, however, reduces local fecundity and the probability that seeds will find a safe site outside the original patch. Thus, there is a conflict between seed survival and colonization. Methods Populations of three epiphytic orchids were monitored over three years in a Mexican humid montane forest and analysed with spatially averaged and with spatially explicit matrix metapopulation models. In the latter, population dynamics at the scale of the subpopulations (epiphytes on individual host trees) are based on detailed stage-structured observations of transition probabilities and trees are connected by a dispersal function. Key Results Population growth rates differed among trees and years. While ignoring these differences, and averaging the population matrices over trees, yields negative population growth, metapopulation models predict stable or growing populations because the trees that support growing subpopulations determine the growth of the metapopulation. Stochastic models which account for the differences among years differed only marginally from deterministic models. Population growth rates were significantly lower, and extinctions of local patches more frequent in models where higher dispersal results in reduced local fecundity compared with hypothetical models where this is not the case. The difference between the two models increased with increasing mean dispersal distance. Though recolonization events increased with dispersal distance, this could not compensate the losses due to reduced local fecundity. Conclusions For epiphytes, metapopulation models are useful to capture processes beyond the level of the single

  5. Diversity Waves in Collapse-Driven Population Dynamics

    PubMed Central

    Maslov, Sergei; Sneppen, Kim

    2015-01-01

    Populations of species in ecosystems are often constrained by availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by comparable reduction in populations of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt and severe reduction in size of the population of a single species freeing up resources for the remaining ones. This mechanism may be relevant e.g. for communities of bacteria, with strain-specific collapses caused e.g. by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent dynamics of our system is characterized by cyclic ‘‘diversity waves’’ triggered by collapses of globally dominating populations. The population diversity peaks at the beginning of each wave and exponentially decreases afterwards. Species abundances have bimodal time-aggregated distribution with the lower peak formed by populations of recently collapsed or newly introduced species while the upper peak - species that has not yet collapsed in the current wave. In most waves both upper and lower peaks are composed of several smaller peaks. This self-organized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a scale-free tail of the time-aggregated population distribution with a universal exponent of 1.7. We show that diversity wave dynamics is robust with respect to variations in the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies. PMID:26367172

  6. Diversity waves in collapse-driven population dynamics

    SciTech Connect

    Maslov, Sergei; Sneppen, Kim

    2015-09-14

    Populations of species in ecosystems are often constrained by availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by comparable reduction in populations of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt and severe collapses of the entire population of a single species freeing up resources for the remaining ones. This mechanism may be relevant e.g. for communities of bacteria, with strain-specific collapses caused e.g. by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent dynamics of our system is cyclic ‘‘diversity waves’’ triggered by collapses of globally dominating populations. The population diversity peaks at the beginning of each wave and exponentially decreases afterwards. Species abundances are characterized by a bimodal time-aggregated distribution with the lower peak formed by populations of recently collapsed or newly introduced species while the upper peak - species that has not yet collapsed in the current wave. In most waves both upper and lower peaks are composed of several smaller peaks. This self-organized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a scale-free tail of the time-aggregated population distribution with a universal exponent of 1.7. We show that diversity wave dynamics is robust with respect to variations in the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies.

  7. Diversity waves in collapse-driven population dynamics

    DOE PAGESBeta

    Maslov, Sergei; Sneppen, Kim

    2015-09-14

    Populations of species in ecosystems are often constrained by availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by comparable reduction in populations of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt and severe collapses of the entire population of a single species freeing up resources for the remaining ones. This mechanism may be relevant e.g. for communities of bacteria, with strain-specific collapses caused e.g.more » by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent dynamics of our system is cyclic ‘‘diversity waves’’ triggered by collapses of globally dominating populations. The population diversity peaks at the beginning of each wave and exponentially decreases afterwards. Species abundances are characterized by a bimodal time-aggregated distribution with the lower peak formed by populations of recently collapsed or newly introduced species while the upper peak - species that has not yet collapsed in the current wave. In most waves both upper and lower peaks are composed of several smaller peaks. This self-organized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a scale-free tail of the time-aggregated population distribution with a universal exponent of 1.7. We show that diversity wave dynamics is robust with respect to variations in the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies.« less

  8. Diversity Waves in Collapse-Driven Population Dynamics.

    PubMed

    Maslov, Sergei; Sneppen, Kim

    2015-09-01

    Populations of species in ecosystems are often constrained by availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by comparable reduction in populations of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt and severe reduction in size of the population of a single species freeing up resources for the remaining ones. This mechanism may be relevant e.g. for communities of bacteria, with strain-specific collapses caused e.g. by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent dynamics of our system is characterized by cyclic ''diversity waves'' triggered by collapses of globally dominating populations. The population diversity peaks at the beginning of each wave and exponentially decreases afterwards. Species abundances have bimodal time-aggregated distribution with the lower peak formed by populations of recently collapsed or newly introduced species while the upper peak--species that has not yet collapsed in the current wave. In most waves both upper and lower peaks are composed of several smaller peaks. This self-organized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a scale-free tail of the time-aggregated population distribution with a universal exponent of 1.7. We show that diversity wave dynamics is robust with respect to variations in the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies. PMID:26367172

  9. Modeling structured population dynamics using data from unmarked individuals

    USGS Publications Warehouse

    Grant, Evan H. Campbell; Zipkin, Elise; Thorson, James T.; See, Kevin; Lynch, Heather J.; Kanno, Yoichiro; Chandler, Richard; Letcher, Benjamin H.; Royle, J. Andrew

    2014-01-01

    The study of population dynamics requires unbiased, precise estimates of abundance and vital rates that account for the demographic structure inherent in all wildlife and plant populations. Traditionally, these estimates have only been available through approaches that rely on intensive mark–recapture data. We extended recently developed N-mixture models to demonstrate how demographic parameters and abundance can be estimated for structured populations using only stage-structured count data. Our modeling framework can be used to make reliable inferences on abundance as well as recruitment, immigration, stage-specific survival, and detection rates during sampling. We present a range of simulations to illustrate the data requirements, including the number of years and locations necessary for accurate and precise parameter estimates. We apply our modeling framework to a population of northern dusky salamanders (Desmognathus fuscus) in the mid-Atlantic region (USA) and find that the population is unexpectedly declining. Our approach represents a valuable advance in the estimation of population dynamics using multistate data from unmarked individuals and should additionally be useful in the development of integrated models that combine data from intensive (e.g., mark–recapture) and extensive (e.g., counts) data sources.

  10. Metamodels for Transdisciplinary Analysis of Wildlife Population Dynamics

    PubMed Central

    Lacy, Robert C.; Miller, Philip S.; Nyhus, Philip J.; Pollak, J. P.; Raboy, Becky E.; Zeigler, Sara L.

    2013-01-01

    Wildlife population models have been criticized for their narrow disciplinary perspective when analyzing complexity in coupled biological – physical – human systems. We describe a “metamodel” approach to species risk assessment when diverse threats act at different spatiotemporal scales, interact in non-linear ways, and are addressed by distinct disciplines. A metamodel links discrete, individual models that depict components of a complex system, governing the flow of information among models and the sequence of simulated events. Each model simulates processes specific to its disciplinary realm while being informed of changes in other metamodel components by accessing common descriptors of the system, populations, and individuals. Interactions among models are revealed as emergent properties of the system. We introduce a new metamodel platform, both to further explain key elements of the metamodel approach and as an example that we hope will facilitate the development of other platforms for implementing metamodels in population biology, species risk assessments, and conservation planning. We present two examples – one exploring the interactions of dispersal in metapopulations and the spread of infectious disease, the other examining predator-prey dynamics – to illustrate how metamodels can reveal complex processes and unexpected patterns when population dynamics are linked to additional extrinsic factors. Metamodels provide a flexible, extensible method for expanding population viability analyses beyond models of isolated population demographics into more complete representations of the external and intrinsic threats that must be understood and managed for species conservation. PMID:24349567

  11. The population dynamics of an endemic collectible cactus

    NASA Astrophysics Data System (ADS)

    Mandujano, María C.; Bravo, Yolotzin; Verhulst, Johannes; Carrillo-Angeles, Israel; Golubov, Jordan

    2015-02-01

    Astrophytum is one of most collected genera in the cactus family. Around the world several species are maintained in collections and yearly, several plants are taken from their natural habitats. Populations of Astorphytum capricorne are found in the northern Chihuahuan desert, Mexico, and as many endemic cactus species, it has a highly restricted habitat. We conducted a demographic study from 2008 to 2010 of the northern populations found at Cuatro Ciénegas, Mexico. We applied matrix population models, included simulations, life table response experiments and descriptions of the population dynamics to evaluate the current status of the species, and detect key life table stages and demographic processes. Population growth rate decreased in both years and only 4% individual mortality can be attributed to looting, and a massive effort is needed to increase seedling recruitment and reduce adult mortality. The fate of individuals differed between years even having the same annual rainfall mainly in accentuated stasis, retrogression and high mortality in all size classes, which coupled with low seed production, no recruitment and collection of plants are the causes contributing to population decline, and hence, increase the risk in which A. capricorne populations are found. Reintroduction of seedlings and lowering adult mortality are urgently needed to revert the alarming demographic condition of A. capricorne populations.

  12. Aspiration dynamics of multi-player games in finite populations

    PubMed Central

    Du, Jinming; Wu, Bin; Altrock, Philipp M.; Wang, Long

    2014-01-01

    On studying strategy update rules in the framework of evolutionary game theory, one can differentiate between imitation processes and aspiration-driven dynamics. In the former case, individuals imitate the strategy of a more successful peer. In the latter case, individuals adjust their strategies based on a comparison of their pay-offs from the evolutionary game to a value they aspire, called the level of aspiration. Unlike imitation processes of pairwise comparison, aspiration-driven updates do not require additional information about the strategic environment and can thus be interpreted as being more spontaneous. Recent work has mainly focused on understanding how aspiration dynamics alter the evolutionary outcome in structured populations. However, the baseline case for understanding strategy selection is the well-mixed population case, which is still lacking sufficient understanding. We explore how aspiration-driven strategy-update dynamics under imperfect rationality influence the average abundance of a strategy in multi-player evolutionary games with two strategies. We analytically derive a condition under which a strategy is more abundant than the other in the weak selection limiting case. This approach has a long-standing history in evolutionary games and is mostly applied for its mathematical approachability. Hence, we also explore strong selection numerically, which shows that our weak selection condition is a robust predictor of the average abundance of a strategy. The condition turns out to differ from that of a wide class of imitation dynamics, as long as the game is not dyadic. Therefore, a strategy favoured under imitation dynamics can be disfavoured under aspiration dynamics. This does not require any population structure, and thus highlights the intrinsic difference between imitation and aspiration dynamics. PMID:24598208

  13. Second Cancers After Fractionated Radiotherapy: Stochastic Population Dynamics Effects

    NASA Technical Reports Server (NTRS)

    Sachs, Rainer K.; Shuryak, Igor; Brenner, David; Fakir, Hatim; Hahnfeldt, Philip

    2007-01-01

    When ionizing radiation is used in cancer therapy it can induce second cancers in nearby organs. Mainly due to longer patient survival times, these second cancers have become of increasing concern. Estimating the risk of solid second cancers involves modeling: because of long latency times, available data is usually for older, obsolescent treatment regimens. Moreover, modeling second cancers gives unique insights into human carcinogenesis, since the therapy involves administering well characterized doses of a well studied carcinogen, followed by long-term monitoring. In addition to putative radiation initiation that produces pre-malignant cells, inactivation (i.e. cell killing), and subsequent cell repopulation by proliferation can be important at the doses relevant to second cancer situations. A recent initiation/inactivation/proliferation (IIP) model characterized quantitatively the observed occurrence of second breast and lung cancers, using a deterministic cell population dynamics approach. To analyze ifradiation-initiated pre-malignant clones become extinct before full repopulation can occur, we here give a stochastic version of this I I model. Combining Monte Carlo simulations with standard solutions for time-inhomogeneous birth-death equations, we show that repeated cycles of inactivation and repopulation, as occur during fractionated radiation therapy, can lead to distributions of pre-malignant cells per patient with variance >> mean, even when pre-malignant clones are Poisson-distributed. Thus fewer patients would be affected, but with a higher probability, than a deterministic model, tracking average pre-malignant cell numbers, would predict. Our results are applied to data on breast cancers after radiotherapy for Hodgkin disease. The stochastic IIP analysis, unlike the deterministic one, indicates: a) initiated, pre-malignant cells can have a growth advantage during repopulation, not just during the longer tumor latency period that follows; b) weekend

  14. Spreading dynamics on heterogeneous populations: Multitype network approach

    NASA Astrophysics Data System (ADS)

    Vazquez, Alexei

    2006-12-01

    I study the spreading of infectious diseases in heterogeneous populations. The population structure is described by a contact graph where vertices represent agents and edges represent disease transmission channels among them. The population heterogeneity is taken into account by the agent’s subdivision in types and the mixing matrix among them. I introduce a type-network representation for the mixing matrix, allowing an intuitive understanding of the mixing patterns and the calculations. Using an iterative approach I obtain recursive equations for the probability distribution of the outbreak size as a function of time. I demonstrate that the expected outbreak size and its progression in time are determined by the largest eigenvalue of the reproductive number matrix and the characteristic distance between agents on the contact graph. Finally, I discuss the impact of intervention strategies to halt epidemic outbreaks. This work provides both a qualitative understanding and tools to obtain quantitative predictions for the spreading dynamics of heterogeneous populations.

  15. Simultaneous effects of food limitation and inducible resistance on herbivore population dynamics.

    PubMed

    Abbott, Karen C; Morris, William F; Gross, Kevin

    2008-02-01

    Many herbivore populations fluctuate temporally, but the causes of those fluctuations remain unclear. Plant inducible resistance can theoretically cause herbivore population fluctuations, because herbivory may induce plant changes that reduce the survival or reproduction of later-feeding herbivores. Herbivory can also simply reduce the quantity of food available for later feeders and this, too, can cause population fluctuations. Inducible resistance and food limitation often occur simultaneously, yet whether they jointly facilitate or suppress herbivore fluctuations remains largely unexplored. We present models that suggest that food limitation and inducible resistance may have synergistic effects on herbivore population dynamics. The population-level response of the food plant to herbivory and the details of how inducible resistance affects herbivore performance both influence the resulting herbivore dynamics. Our results identify some biological properties of plant-herbivore systems that might determine whether or not cycles occur, and suggest that future empirical and theoretical population dynamics studies should account for the effects of both food limitation and inducible resistance. PMID:17991500

  16. Assessing tiger population dynamics using photographic capture-recapture sampling

    USGS Publications Warehouse

    Karanth, K.U.; Nichols, J.D.; Kumar, N.S.; Hines, J.E.

    2006-01-01

    Although wide-ranging, elusive, large carnivore species, such as the tiger, are of scientific and conservation interest, rigorous inferences about their population dynamics are scarce because of methodological problems of sampling populations at the required spatial and temporal scales. We report the application of a rigorous, noninvasive method for assessing tiger population dynamics to test model-based predictions about population viability. We obtained photographic capture histories for 74 individual tigers during a nine-year study involving 5725 trap-nights of effort. These data were modeled under a likelihood-based, ?robust design? capture?recapture analytic framework. We explicitly modeled and estimated ecological parameters such as time-specific abundance, density, survival, recruitment, temporary emigration, and transience, using models that incorporated effects of factors such as individual heterogeneity, trap-response, and time on probabilities of photo-capturing tigers. The model estimated a random temporary emigration parameter of =K' =Y' 0.10 ? 0.069 (values are estimated mean ? SE). When scaled to an annual basis, tiger survival rates were estimated at S = 0.77 ? 0.051, and the estimated probability that a newly caught animal was a transient was = 0.18 ? 0.11. During the period when the sampled area was of constant size, the estimated population size Nt varied from 17 ? 1.7 to 31 ? 2.1 tigers, with a geometric mean rate of annual population change estimated as = 1.03 ? 0.020, representing a 3% annual increase. The estimated recruitment of new animals, Bt, varied from 0 ? 3.0 to 14 ? 2.9 tigers. Population density estimates, D, ranged from 7.33 ? 0.8 tigers/100 km2 to 21.73 ? 1.7 tigers/100 km2 during the study. Thus, despite substantial annual losses and temporal variation in recruitment, the tiger density remained at relatively high levels in Nagarahole. Our results are consistent with the hypothesis that protected wild tiger populations can remain

  17. Climate and density shape population dynamics of a marine top predator.

    PubMed Central

    Barbraud, Christophe; Weimerskirch, Henri

    2003-01-01

    Long-term studies have documented that climate fluctuations affect the dynamics of populations, but the relative influence of stochastic and density-dependent processes is still poorly understood and debated. Most studies have been conducted on terrestrial systems, and lacking are studies on marine systems explicitly integrating the fact that most populations live in seasonal environments and respond to regular or systematic environmental changes. We separated winter from summer mortality in a seabird population, the blue petrel Halobaena caerulea, in the southern Indian Ocean where the El Niño/Southern Oscillation effects occur with a 3-4-year lag. Seventy per cent of the mortality occurred in winter and was linked to climatic factors, being lower during anomalous warm events. The strength of density dependence was affected by climate, with population crashes occurring when poor conditions occurred at high densities. We found that an exceptionally long-lasting warming caused a ca. 40% decline of the population, suggesting that chronic climate change will strongly affect this top predator. These findings demonstrate that populations in marine systems are particularly susceptible to climate variation through complex interactions between seasonal mortality and density-dependent effects. PMID:14561273

  18. Time-lag in extinction dynamics in experimental populations: evidence for a genetic Allee effect?

    PubMed

    Vercken, Elodie; Vincent, Flora; Mailleret, Ludovic; Ris, Nicolas; Tabone, Elisabeth; Fauvergue, Xavier

    2013-05-01

    1. Propagule pressure, i.e. the number of individuals introduced, is thought to be a major predictor of the establishment success of introduced populations in the field. Its influence in laboratory experimental systems has however been questioned. In fact, other factors involved in long-term population persistence, like habitat size, were usually found to explain most of the dynamics of experimental populations. 2. To better understand the respective influence of short- and long-term factors and their potential interaction on extinction dynamics in experimental systems, we investigated the influence of propagule pressure, habitat size and genetic background on the early dynamics of laboratory-based populations of a hymenopteran parasitoid. 3. The amount of demographic variance differed between establishment and persistence phase and was influenced by habitat size and genetic background (geographic strain), but independent of propagule pressure. In contrast, the probability of extinction within five generations depended on the genetic background and on the interaction between propagule pressure and habitat size. Vulnerability to extinction in small size habitats was increased when populations were founded with a small number of individuals, but this effect was delayed until the third to fifth generations. 4. These results indicate that demographic stochasticity is influential during population establishment, but is not affected by the genetic variability of propagules. On the other hand, extinction might be influenced by a genetic Allee effect triggered by the combination of low propagule pressure and genetic drift. Finally, we documented consistent differences between genetic backgrounds in both deterministic and stochastic population dynamics patterns, with major consequences on extinction risk and ultimately population establishment. PMID:23398653

  19. Structural Drift: The Population Dynamics of Sequential Learning

    PubMed Central

    Crutchfield, James P.; Whalen, Sean

    2012-01-01

    We introduce a theory of sequential causal inference in which learners in a chain estimate a structural model from their upstream “teacher” and then pass samples from the model to their downstream “student”. It extends the population dynamics of genetic drift, recasting Kimura's selectively neutral theory as a special case of a generalized drift process using structured populations with memory. We examine the diffusion and fixation properties of several drift processes and propose applications to learning, inference, and evolution. We also demonstrate how the organization of drift process space controls fidelity, facilitates innovations, and leads to information loss in sequential learning with and without memory. PMID:22685387

  20. Evolutionary dynamics of a multigroup fluctuating-population system

    NASA Astrophysics Data System (ADS)

    Bhatia, D. P.; Arora, D.; Prasad, M. A.

    1993-03-01

    We studied the evolutionary dynamics of a population undergoing asexual reproduction in a flat-fitness landscape. The quantity of interest is the distribution of the overlap function q which is a measure of the similarity in the genome structure between two individuals. We obtain analytical expressions for , , and p(q) in a model with the following features: continuous time, fluctuating population divided into many compartments, and a finite number of genes per genome. A few special cases of interest are also discussed.

  1. Dynamics of a population of oscillatory and excitable elements

    NASA Astrophysics Data System (ADS)

    O'Keeffe, Kevin P.; Strogatz, Steven H.

    2016-06-01

    We analyze a variant of a model proposed by Kuramoto, Shinomoto, and Sakaguchi for a large population of coupled oscillatory and excitable elements. Using the Ott-Antonsen ansatz, we reduce the behavior of the population to a two-dimensional dynamical system with three parameters. We present the stability diagram and calculate several of its bifurcation curves analytically, for both excitatory and inhibitory coupling. Our main result is that when the coupling function is broad, the system can display bistability between steady states of constant high and low activity, whereas when the coupling function is narrow and inhibitory, one of the states in the bistable regime can show persistent pulsations in activity.

  2. Optimal control methods for controlling bacterial populations with persister dynamics

    NASA Astrophysics Data System (ADS)

    Cogan, N. G.

    2016-06-01

    Bacterial tolerance to antibiotics is a well-known phenomena; however, only recent studies of bacterial biofilms have shown how multifaceted tolerance really is. By joining into a structured community and offering shared protection and gene transfer, bacterial populations can protect themselves genotypically, phenotypically and physically. In this study, we collect a line of research that focuses on phenotypic (or plastic) tolerance. The dynamics of persister formation are becoming better understood, even though there are major questions that remain. The thrust of our results indicate that even without detailed description of the biological mechanisms, theoretical studies can offer strategies that can eradicate bacterial populations with existing drugs.

  3. Dynamical models of a sample of Population II stars

    NASA Astrophysics Data System (ADS)

    Levison, H. F.; Richstone, D. O.

    1986-09-01

    Dynamical models are constructed in order to investigate the implications of recent kinematic data of distant Population II stars on the emissivity distribution of those stars. Models are constructed using a modified Schwarzschild method in two extreme scale-free potentials, spherical and E6 elliptical. Both potentials produce flat rotation curves and velocity dispersion profiles. In all models, the distribution of stars in this sample is flat. Moreover, it is not possible to construct a model with a strictly spheroidal emissivity distribution. Most models have dimples at the poles. The dynamics of the models indicate that the system is supported by both the third integral and z angular momentum.

  4. The presence of Bt-transgenic oilseed rape in wild mustard populations affects plant growth.

    PubMed

    Liu, Yongbo; Stewart, C Neal; Li, Junsheng; Huang, Hai; Zhang, Xitao

    2015-12-01

    The adventitious presence of transgenic plants in wild plant populations is of ecological and regulatory concern, but the consequences of adventitious presence are not well understood. Here, we introduced Bacillus thuringiensis Cry1Ac (Bt)-transgenic oilseed rape (Bt OSR, Brassica napus) with various frequencies into wild mustard (Brassica juncea) populations. We sought to better understand the adventitious presence of this transgenic insecticidal crop in a wild-relative plant population. We assessed the factors of competition, resource availability and diamondback moth (Plutella xylostella) infestation on plant population dynamics. As expected, Bt OSR performed better than wild mustard in mixed populations under herbivore attack in habitats with enough resources, whereas wild mustard had higher fitness when Bt OSR was rarer in habitats with limited resources. Results suggest that the presence of insect-resistant transgenic plants could decrease the growth of wild mustard and Bt OSR plants and their populations, especially under high herbivore pressure. PMID:26338267

  5. Effect of temperature on the population dynamics of Aedes aegypti

    NASA Astrophysics Data System (ADS)

    Yusoff, Nuraini; Tokachil, Mohd Najir

    2015-10-01

    Aedes aegypti is one of the main vectors in the transmission of dengue fever. Its abundance may cause the spread of the disease to be more intense. In the study of its biological life cycle, temperature was found to increase the development rate of each stage of this species and thus, accelerate the process of the development from egg to adult. In this paper, a Lefkovitch matrix model will be used to study the stage-structured population dynamics of Aedes aegypti. In constructing the transition matrix, temperature will be taken into account. As a case study, temperature recorded at the Subang Meteorological Station for year 2006 until 2010 will be used. Population dynamics of Aedes aegypti at maximum, average and minimum temperature for each year will be simulated and compared. It is expected that the higher the temperature, the faster the mosquito will breed. The result will be compared to the number of dengue fever incidences to see their relationship.

  6. Recent range expansion of a terrestrial orchid corresponds with climate-driven variation in its population dynamics.

    PubMed

    van der Meer, Sascha; Jacquemyn, Hans; Carey, Peter D; Jongejans, Eelke

    2016-06-01

    The population dynamics and distribution limits of plant species are predicted to change as the climate changes. However, it remains unclear to what extent climate variables affect population dynamics, which vital rates are most sensitive to climate change, and whether the same vital rates drive population dynamics in different populations. In this study, we used long-term demographic data from two populations of the terrestrial orchid Himantoglossum hircinum growing at the northern edge of their geographic range to quantify the influence of climate change on demographic vital rates. Integral projection models were constructed to study how climate conditions between 1991 and 2006 affected population dynamics and to assess how projected future climate change will affect the long-term viability of this species. Based on the parameterised vital rate functions and the observed climatic conditions, one of the studied populations had an average population growth rate above 1 (λ = 1.04), while the other was declining at ca. 3 % year(-1) (λ = 0.97). Variation in temperature and precipitation mainly affected population growth through their effect on survival and fecundity. Based on UK Climate Projection 2009 estimates of future climate conditions for three greenhouse gas emission scenarios, population growth rates are expected to increase in one of the studied populations. Overall, our results indicate that the observed changes in climatic conditions appeared to be beneficial to the long-term survival of the species in the UK and suggest that they may have been the driving force behind the current range expansion of H. hircinum in England. PMID:26932468

  7. Effects of an organophosphate on Daphnia magna at suborganismal and organismal levels: implications for population dynamics.

    PubMed

    Duquesne, Sabine

    2006-10-01

    The effects and recovery of 24 h pulse exposure to paraoxon-methyl on Daphnia magna were recorded for various endpoints to study the propagation of effects through various biological levels of organization. Above a threshold concentration (2.2 microgL(-1)), all selected endpoints were affected. Thus, effects at the suborganismal level (e.g., the biomarker response: transient inhibition of cholinesterase (ChE) activity) were accompanied by effects at the organismal (survival, reduction in reproductive performance, decrease in body size) and population (reduced population growth rate) levels. At intermediate and sublethal concentrations, exposure induced a transient ChE inhibition that was also accompanied by effects at the organismal level and that exerted long-term effects on population dynamics. At lower concentrations, although ChE activity was affected, there was no propagation of effects to higher biological levels. This study shows that effects of pulse exposure to organophosphates propagate from the suborganismal level toward the population level and demonstrates the significance of transient ChE inhibition on population dynamics. PMID:16545452

  8. Factors Affecting the Distribution Pattern of Wild Plants with Extremely Small Populations in Hainan Island, China

    PubMed Central

    Chen, Yukai; Yang, Xiaobo; Yang, Qi; Li, Donghai; Long, Wenxing; Luo, Wenqi

    2014-01-01

    Understanding which factors affect the distribution pattern of extremely small populations is essential to the protection and propagation of rare and endangered plant species. In this study, we established 108 plots covering the entire Hainan Island, and measured the appearance frequency and species richness of plant species with extremely small populations, as well as the ecological environments and human disturbances during 2012–2013. We explored how the ecological environments and human activities affected the distribution pattern of these extremely small populations. Results showed that the extremely small populations underwent human disturbances and threats, and they were often found in fragmental habitats. The leading factors changing the appearance frequency of extremely small populations differed among plant species, and the direct factors making them susceptible to extinction were human disturbances. The peak richness of extremely small populations always occurred at the medium level across environmental gradients, and their species richness always decreased with increasing human disturbances. However, the appearance frequencies of three orchid species increased with the increasing human disturbances. Our study thus indicate that knowledge on how the external factors, such as the ecological environment, land use type, roads, human activity, etc., affect the distribution of the extremely small populations should be taken for the better protecting them in the future. PMID:24830683

  9. Factors affecting the distribution pattern of wild plants with extremely small populations in Hainan Island, China.

    PubMed

    Chen, Yukai; Yang, Xiaobo; Yang, Qi; Li, Donghai; Long, Wenxing; Luo, Wenqi

    2014-01-01

    Understanding which factors affect the distribution pattern of extremely small populations is essential to the protection and propagation of rare and endangered plant species. In this study, we established 108 plots covering the entire Hainan Island, and measured the appearance frequency and species richness of plant species with extremely small populations, as well as the ecological environments and human disturbances during 2012-2013. We explored how the ecological environments and human activities affected the distribution pattern of these extremely small populations. Results showed that the extremely small populations underwent human disturbances and threats, and they were often found in fragmental habitats. The leading factors changing the appearance frequency of extremely small populations differed among plant species, and the direct factors making them susceptible to extinction were human disturbances. The peak richness of extremely small populations always occurred at the medium level across environmental gradients, and their species richness always decreased with increasing human disturbances. However, the appearance frequencies of three orchid species increased with the increasing human disturbances. Our study thus indicate that knowledge on how the external factors, such as the ecological environment, land use type, roads, human activity, etc., affect the distribution of the extremely small populations should be taken for the better protecting them in the future. PMID:24830683

  10. Seasonal Population Dynamics of Three Potato Pests in Washington State.

    PubMed

    D'Auria, Elizabeth M; Wohleb, Carrie H; Waters, Timothy D; Crowder, David W

    2016-08-01

    Pest phenology models allow producers to anticipate pest outbreaks and deploy integrated pest management (IPM) strategies. Phenology models are particularly useful for cropping systems with multiple economically damaging pests throughout a season. Potato (Solanum tuberosum L.) crops of Washington State, USA, are attacked by many insect pests including the potato tuberworm (Phthorimaea operculella Zeller), the beet leafhopper (Circulifer tenellus Baker), and the green peach aphid (Myzus persicae Sulzer). Each of these pests directly damages potato foliage or tubers; C. tenellus and M. persicae also transmit pathogens that can drastically reduce potato yields. We monitored the seasonal population dynamics of these pests by conducting weekly sampling on a network of commercial farms from 2007 to 2014. Using these data, we developed phenology models to characterize the seasonal population dynamics of each pest based on accumulated degree-days (DD). All three pests exhibited consistent population dynamics across seasons that were mediated by temperature. Of the three pests, C. tenellus was generally the first detected in potato crops, with 90% of adults captured by 936 DD. In contrast, populations of P. operculella and M. persicae built up more slowly over the course of the season, with 90% cumulative catch by 1,590 and 2,634 DD, respectively. Understanding these seasonal patterns could help potato producers plan their IPM strategies while allowing them to move away from calendar-based applications of insecticides. More broadly, our results show how long-term monitoring studies that explore dynamics of multiple pest species can aid in developing IPM strategies in crop systems. PMID:27271946

  11. Learning to Estimate Dynamical State with Probabilistic Population Codes

    PubMed Central

    Sabes, Philip N.

    2015-01-01

    Tracking moving objects, including one’s own body, is a fundamental ability of higher organisms, playing a central role in many perceptual and motor tasks. While it is unknown how the brain learns to follow and predict the dynamics of objects, it is known that this process of state estimation can be learned purely from the statistics of noisy observations. When the dynamics are simply linear with additive Gaussian noise, the optimal solution is the well known Kalman filter (KF), the parameters of which can be learned via latent-variable density estimation (the EM algorithm). The brain does not, however, directly manipulate matrices and vectors, but instead appears to represent probability distributions with the firing rates of population of neurons, “probabilistic population codes.” We show that a recurrent neural network—a modified form of an exponential family harmonium (EFH)—that takes a linear probabilistic population code as input can learn, without supervision, to estimate the state of a linear dynamical system. After observing a series of population responses (spike counts) to the position of a moving object, the network learns to represent the velocity of the object and forms nearly optimal predictions about the position at the next time-step. This result builds on our previous work showing that a similar network can learn to perform multisensory integration and coordinate transformations for static stimuli. The receptive fields of the trained network also make qualitative predictions about the developing and learning brain: tuning gradually emerges for higher-order dynamical states not explicitly present in the inputs, appearing as delayed tuning for the lower-order states. PMID:26540152

  12. Development of paradigms for the dynamics of structured populations

    SciTech Connect

    Not Available

    1994-10-01

    This is a technical progress report on the dynamics of predator-prey systems in a patchy environment. A new phenomenon that might contribute to outbreaks in systems of discrete patches has been determined using a discrete time model with both spatial and age structure. A model for a single species in a patchy environment with migration, local population growth and disasters with in patches has been formulated and a brief description is included.

  13. Learning to Estimate Dynamical State with Probabilistic Population Codes.

    PubMed

    Makin, Joseph G; Dichter, Benjamin K; Sabes, Philip N

    2015-11-01

    Tracking moving objects, including one's own body, is a fundamental ability of higher organisms, playing a central role in many perceptual and motor tasks. While it is unknown how the brain learns to follow and predict the dynamics of objects, it is known that this process of state estimation can be learned purely from the statistics of noisy observations. When the dynamics are simply linear with additive Gaussian noise, the optimal solution is the well known Kalman filter (KF), the parameters of which can be learned via latent-variable density estimation (the EM algorithm). The brain does not, however, directly manipulate matrices and vectors, but instead appears to represent probability distributions with the firing rates of population of neurons, "probabilistic population codes." We show that a recurrent neural network-a modified form of an exponential family harmonium (EFH)-that takes a linear probabilistic population code as input can learn, without supervision, to estimate the state of a linear dynamical system. After observing a series of population responses (spike counts) to the position of a moving object, the network learns to represent the velocity of the object and forms nearly optimal predictions about the position at the next time-step. This result builds on our previous work showing that a similar network can learn to perform multisensory integration and coordinate transformations for static stimuli. The receptive fields of the trained network also make qualitative predictions about the developing and learning brain: tuning gradually emerges for higher-order dynamical states not explicitly present in the inputs, appearing as delayed tuning for the lower-order states. PMID:26540152

  14. Continuous probabilistic analysis to evolutionary game dynamics in finite populations.

    PubMed

    Gao, Meng

    2009-07-01

    Evolutionary game dynamics of two strategies in finite population is studied by continuous probabilistic approach. Besides frequency dependent selection, mutation was also included in this study. The equilibrium probability density functions of abundance, expected time to extinction or fixation were derived and their numerical solutions are calculated as illustrations. Meanwhile, individual-based computer simulations are also done. A comparison reveals the consistency between theoretical analysis and simulations. PMID:19219510

  15. Interacting trophic forcing and the population dynamics of herring.

    PubMed

    Lindegren, Martin; Ostman, Orjan; Gårdmark, Anna

    2011-07-01

    Small pelagic fish occupy a central position in marine ecosystems worldwide, largely by determining the energy transfer from lower trophic levels to predators at the top of the food web, including humans. Population dynamics of small pelagic fish may therefore be regulated neither strictly bottom-up nor top-down, but rather through multiple external and internal drivers. While in many studies single drivers have been identified, potential synergies of multiple factors, as well as their relative importance in regulating population dynamics of small pelagic fish, is a largely unresolved issue. Using a statistical, age-structured modeling approach, we demonstrate the relative importance and influence of bottom-up (e.g., climate, zooplankton availability) and top-down (i.e., fishing and predation) factors on the population dynamics of Bothnian Sea herring (Clupea harengus) throughout its life cycle. Our results indicate significant bottom-up effects of zooplankton and interspecific competition from sprat (Sprattus sprattus), particularly on younger age classes of herring. Although top-down forcing through fishing and predation by grey seals (Halichoerus grypus) and Atlantic cod (Gadus morhua) also was evident, these factors were less important than resource availability and interspecific competition. Understanding key ecological processes and interactions is fundamental to ecosystem-based management practices necessary to promote sustainable exploitation of small pelagic fish. PMID:21870614

  16. Inferring the Dynamics of Effective Population Size Using Autosomal Genomes.

    PubMed

    Hou, Zheng; Luo, Yin; Wang, Zhisheng; Zheng, Hong-Xiang; Wang, Yi; Zhou, Hang; Wu, Leqin; Jin, Li

    2016-01-01

    Next-generation sequencing technology has provided a great opportunity for inferring human demographic history by investigating changes in the effective population size (Ne). In this report, we introduce a strategy for estimating Ne dynamics, allowing the exploration of large multi-locus SNP datasets. We applied this strategy to the Phase 1 Han Chinese samples from the 1000 Genomes Project. The Han Chinese population has undergone a continuous expansion since 25,000 years ago, at first slowly from about 7,300 to 9,800 (at the end of the last glacial maximum about 15,000 YBP), then more quickly to about 46,000 (at the beginning of the Neolithic about 8,000 YBP), and then even more quickly to reach a population size of about 140,000 (recently). PMID:26832887

  17. Connection between dynamically derived IMF normalisation and stellar populations

    NASA Astrophysics Data System (ADS)

    McDermid, Richard M.

    2015-04-01

    In this contributed talk I present recent results on the connection between stellar population properties and the normalisation of the stellar initial mass function (IMF) measured using stellar dynamics, based on a large sample of 260 early-type galaxies observed as part of the ATLAS3D project. This measure of the IMF normalisation is found to vary non-uniformly with age- and metallicity-sensitive absorption line strengths. Applying single stellar population models, there are weak but measurable trends of the IMF with age and abundance ratio. Accounting for the dependence of stellar population parameters on velocity dispersion effectively removes these trends, but subsequently introduces a trend with metallicity, such that `heavy' IMFs favour lower metallicities. The correlations are weaker than those found from previous studies directly detecting low-mass stars, suggesting some degree of tension between the different approaches of measuring the IMF. Resolving these discrepancies will be the focus of future work.

  18. Inferring the Dynamics of Effective Population Size Using Autosomal Genomes

    PubMed Central

    Hou, Zheng; Luo, Yin; Wang, Zhisheng; Zheng, Hong-Xiang; Wang, Yi; Zhou, Hang; Wu, Leqin; Jin, Li

    2016-01-01

    Next-generation sequencing technology has provided a great opportunity for inferring human demographic history by investigating changes in the effective population size (Ne). In this report, we introduce a strategy for estimating Ne dynamics, allowing the exploration of large multi-locus SNP datasets. We applied this strategy to the Phase 1 Han Chinese samples from the 1000 Genomes Project. The Han Chinese population has undergone a continuous expansion since 25,000 years ago, at first slowly from about 7,300 to 9,800 (at the end of the last glacial maximum about 15,000 YBP), then more quickly to about 46,000 (at the beginning of the Neolithic about 8,000 YBP), and then even more quickly to reach a population size of about 140,000 (recently). PMID:26832887

  19. Evolutionary dynamics of social dilemmas in structured heterogeneous populations

    PubMed Central

    Santos, F. C.; Pacheco, J. M.; Lenaerts, Tom

    2006-01-01

    Real populations have been shown to be heterogeneous, in which some individuals have many more contacts than others. This fact contrasts with the traditional homogeneous setting used in studies of evolutionary game dynamics. We incorporate heterogeneity in the population by studying games on graphs, in which the variability in connectivity ranges from single-scale graphs, for which heterogeneity is small and associated degree distributions exhibit a Gaussian tale, to scale-free graphs, for which heterogeneity is large with degree distributions exhibiting a power-law behavior. We study the evolution of cooperation, modeled in terms of the most popular dilemmas of cooperation. We show that, for all dilemmas, increasing heterogeneity favors the emergence of cooperation, such that long-term cooperative behavior easily resists short-term noncooperative behavior. Moreover, we show how cooperation depends on the intricate ties between individuals in scale-free populations. PMID:16484371

  20. Evolutionary dynamics of social dilemmas in structured heterogeneous populations.

    PubMed

    Santos, F C; Pacheco, J M; Lenaerts, Tom

    2006-02-28

    Real populations have been shown to be heterogeneous, in which some individuals have many more contacts than others. This fact contrasts with the traditional homogeneous setting used in studies of evolutionary game dynamics. We incorporate heterogeneity in the population by studying games on graphs, in which the variability in connectivity ranges from single-scale graphs, for which heterogeneity is small and associated degree distributions exhibit a Gaussian tale, to scale-free graphs, for which heterogeneity is large with degree distributions exhibiting a power-law behavior. We study the evolution of cooperation, modeled in terms of the most popular dilemmas of cooperation. We show that, for all dilemmas, increasing heterogeneity favors the emergence of cooperation, such that long-term cooperative behavior easily resists short-term noncooperative behavior. Moreover, we show how cooperation depends on the intricate ties between individuals in scale-free populations. PMID:16484371

  1. Stochasticity and universal dynamics in communicating cellular populations

    NASA Astrophysics Data System (ADS)

    Noorbakhsh, Javad; Mehta, Pankaj; Allyson Sgro Collaboration; David Schwab Collaboration; Troy Mestler Collaboration; Thomas Gregor Collaboration

    2014-03-01

    A fundamental problem in biology is to understand how biochemical networks within individual cells coordinate and control population-level behaviors. Our knowledge of these biochemical networks is often incomplete, with little known about the underlying kinetic parameters. Here, we present a general modeling approach for overcoming these challenges based on universality. We apply our approach to study the emergence of collective oscillations of the signaling molecule cAMP in populations of the social amoebae Dictyostelium discoideum and show that a simple two-dimensional dynamical system can reproduce signaling dynamics of single cells and successfully predict novel population-level behaviors. We reduce all the important parameters of our model to only two and will study its behavior through a phase diagram. This phase diagram determines conditions under which cells are quiet or oscillating either coherently or incoherently. Furthermore it allows us to study the effect of different model components such as stochasticity, multicellularity and signal preprocessing. A central finding of our model is that Dictyostelium exploit stochasticity within biochemical networks to control population level behaviors.

  2. Drivers of waterfowl population dynamics: from teal to swans

    USGS Publications Warehouse

    Koons, David N.; Gunnarsson, Gunnar; Schmutz, Joel A.; Rotella, Jay J.

    2014-01-01

    Waterfowl are among the best studied and most extensively monitored species in the world. Given their global importance for sport and subsistence hunting, viewing and ecosystem functioning, great effort has been devoted since the middle part of the 20th century to understanding both the environmental and demographic mechanisms that influence waterfowl population and community dynamics. Here we use comparative approaches to summarise and contrast our understanding ofwaterfowl population dynamics across species as short-lived as the teal Anas discors and A.crecca to those such as the swans Cygnus sp. which have long life-spans. Specifically, we focus on population responses to vital rate perturbations across life history strategies, discuss bottom-up and top-down responses of waterfowlpopulations to global change, and summarise our current understanding of density dependence across waterfowl species. We close by identifying research needs and highlight ways to overcome the challenges of sustainably managing waterfowl populations in the 21st century.

  3. Food web dynamics affect Northeast Arctic cod recruitment

    PubMed Central

    Hjermann, Dag Ø; Bogstad, Bjarte; Eikeset, Anne Maria; Ottersen, Geir; Gjøsæter, Harald; Stenseth, Nils Chr

    2006-01-01

    Proper management of ecosystems requires an understanding of both the species interactions as well as the effect of climate variation. However, a common problem is that the available time-series are of different lengths. Here, we present a general approach for studying the dynamic structure of such interactions. Specifically, we analyse the recruitment of the world's largest cod stock, the Northeast Arctic cod. Studies based on data starting in the 1970–1980s indicate that this stock is affected by temperature through a variety of pathways. However, the value of such studies is somewhat limited by the fact that they are based on a quite specific ecological and climatic situation. Recently, this stock has consisted of fairly young fish and the spawning stock has consisted of relatively few age groups. In this study, we develop a model for the effect of capelin (the cod's main prey) and herring on cod recruitment since 1973. Based on this model, we analyse data on cod, herring and temperature going back to 1921 and find that food-web effects explain a significant part of the cod recruitment variation back to around 1950. PMID:17254990

  4. Tuning stochastic matrix models with hydrologic data to predict the population dynamics of a riverine fish

    USGS Publications Warehouse

    Sakaris, P.C.; Irwin, E.R.

    2010-01-01

    erratic and variable than population growth in the Coosa River. We encourage ecologists to develop similar models for other lotic species, particularly in regulated river systems. Successful management of fish populations in regulated systems requires that we are able to predict how hydrology affects recruitment and will ultimately influence the population dynamics of fishes. ?? 2010 by the Ecological Society of America.

  5. Population dynamics of Microtus pennsylvanicus in corridor-linked patches

    USGS Publications Warehouse

    Coffman, C.J.; Nichols, J.D.; Pollock, K.H.

    2001-01-01

    Corridors have become a key issue in the discussion of conservation planning: however, few empirical data exist on the use of corridors and their effects on population dynamics. The objective of this replicated, population level, capture-re-capture experiment on meadow voles was to estimate and compare population characteristics of voles between (1) corridor-linked fragments, (2) isolated or non-linked fragments, and (3) unfragmented areas. We conducted two field experiments involving 22600 captures of 5700 individuals. In the first, the maintained corridor study, corridors were maintained at the time of fragmentation, and in the second, the constructed corridor study, we constructed corridors between patches that had been fragmented for some period of time. We applied multistate capture-recapture models with the robust design to estimate adult movement and survival rates, population size, temporal variation in population size, recruitment, and juvenile survival rates. Movement rates increased to a greater extent on constructed corridor-linked grids than on the unfragmented or non-linked fragmented grids between the pre- and post-treatment periods. We found significant differences in local survival on the treated (corridor-linked) grids compared to survival on the fragmented and unfragmented grids between the pre- and post-treatment periods. We found no clear pattern of treatment effects on population size or recruitment in either study. However, in both studies, we found that unfragmented grids were more stable than the fragmented grids based on lower temporal variability in population size. To our knowledge, this is the first experimental study demonstrating that corridors constructed between existing fragmented populations can indeed cause increases in movement and associated changes in demography, supporting the use of constructed corridors for this purpose in conservation biology.

  6. Population Dynamics of Early Human Migration in Britain

    PubMed Central

    Vahia, Mayank N.; Ladiwala, Uma; Mahathe, Pavan; Mathur, Deepak

    2016-01-01

    Background Early human migration is largely determined by geography and human needs. These are both deterministic parameters when small populations move into unoccupied areas where conflicts and large group dynamics are not important. The early period of human migration into the British Isles provides such a laboratory which, because of its relative geographical isolation, may allow some insights into the complex dynamics of early human migration and interaction. Method and Results We developed a simulation code based on human affinity to habitable land, as defined by availability of water sources, altitude, and flatness of land, in choosing the path of migration. Movement of people on the British island over the prehistoric period from their initial entry points was simulated on the basis of data from the megalithic period. Topographical and hydro-shed data from satellite databases was used to define habitability, based on distance from water bodies, flatness of the terrain, and altitude above sea level. We simulated population movement based on assumptions of affinity for more habitable places, with the rate of movement tempered by existing populations. We compared results of our computer simulations with genetic data and show that our simulation can predict fairly accurately the points of contacts between different migratory paths. Such comparison also provides more detailed information about the path of peoples’ movement over ~2000 years before the present era. Conclusions We demonstrate an accurate method to simulate prehistoric movements of people based upon current topographical satellite data. Our findings are validated by recently-available genetic data. Our method may prove useful in determining early human population dynamics even when no genetic information is available. PMID:27148959

  7. Population dynamics in Asia and the Pacific: implications for development.

    PubMed

    1994-03-01

    This article is an excerpt from a recently published article on interactions between population and development in the "Economic and Social Survey of Asia and the Pacific, 1993." Topics include the dynamics of change (growth, age structure, sex composition, migration); implications for specific development issues (population and education, population and health, population and employment, and population and the environment); and policy approaches (slowing growth, spatial distribution, and the role of women). The Asian focus is on population policy and fertility declines. Different conditions specific to each country and varying degrees of program success give rise to country-specific differences in rates of growth and declines in fertility. Population compositions and pressures on spatial distribution differ among countries. Development demands differ for education, health, employment, and environmental controls. A common feature is that population is integrated into social and economic development policies. The links between population and the environment are recognized and will be integrated into policy as knowledge emerges. The ESCAP region has about 58% of world population, and fertility has declined to 3.1 children per woman. Fertility declines do not result in demonstrable changes in the rate of population growth, because the proportion of reproductive age women has increased and will continue to do so until 2010. Reductions in fertility are balanced by mortality declines. The annual rate of increase has gradually slowed, however the absolute size is still huge. The goal of the Bali Declaration of 1992 is to reach replacement level fertility of 2.2 children per woman by 2010 in the ESCAP region. The UN median variant projects 2.4 children per woman by 2010. The countries unlikely to reach replacement level fertility are India, the Philippines, Vietnam, Bangladesh, and Pakistan. Age structure will determine the need for services. For example, South Asia will

  8. Spatial structure and chaos in insect population dynamics

    NASA Astrophysics Data System (ADS)

    Hassell, Michael P.; Comins, Hugh N.; Mayt, Robert M.

    1991-09-01

    MOST environments are spatially subdivided, or patchy, and there has been much interest in the relationship between the dynamics of populations at the local and regional (metapopulation) scales1. Here we study mathematical models for host-parasitoid interactions, where in each generation specified fractions (µN and µp, respectively) of the host and parasitoid subpopulations in each patch move to adjacent patches; in most previous work, the movement is not localized but is to any other patch2. These simple and biologically sensible models with limited diffusive dispersal exhibit a remarkable range of dynamic behaviour: the density of the host and parasitoid subpopulations in a two-dimensional array of patches may exhibit complex patterns of spiral waves or spatially chaotic variation, they may show static 'crystal lattice' patterns, or they may become extinct. This range of behaviour is obtained with the local dynamics being deterministically unstable, with a constant host reproductive rate and no density dependence in the movement patterns. The dynamics depend on the host reproductive rate, and on the values of the parameters µN and µp. The results are relatively insensitive to the details of the interactions; we get essentially the same results from the mathematically-explicit Nicholon-Bailey model of host-parasitoid interactions, and from a very general 'cellular automaton' model in which only qualitative rules are specified. We conclude that local movement in a patchy environment can help otherwise unstable host and parasitoid populations to persist together, but that the deterministically generated spatial patterns in population density can be exceedingly complex (and sometimes indistinguishable from random environmental fluctuations).

  9. Dynamics of adaptive immunity against phage in bacterial populations

    NASA Astrophysics Data System (ADS)

    Bradde, Serena; Vucelja, Marija; Tesileanu, Tiberiu; Balasubramanian, Vijay

    The CRISPR (clustered regularly interspaced short palindromic repeats) mechanism allows bacteria to adaptively defend against phages by acquiring short genomic sequences (spacers) that target specific sequences in the viral genome. We propose a population dynamical model where immunity can be both acquired and lost. The model predicts regimes where bacterial and phage populations can co-exist, others where the populations oscillate, and still others where one population is driven to extinction. Our model considers two key parameters: (1) ease of acquisition and (2) spacer effectiveness in conferring immunity. Analytical calculations and numerical simulations show that if spacers differ mainly in ease of acquisition, or if the probability of acquiring them is sufficiently high, bacteria develop a diverse population of spacers. On the other hand, if spacers differ mainly in their effectiveness, their final distribution will be highly peaked, akin to a ``winner-take-all'' scenario, leading to a specialized spacer distribution. Bacteria can interpolate between these limiting behaviors by actively tuning their overall acquisition rate.

  10. Interactive effects of prey and p,p'-DDE on burrowing owl population dynamics.

    PubMed

    Gervais, Jennifer A; Hunter, Christine M; Anthony, Robert G

    2006-04-01

    We used population models to explore the effects of the organochlorine contaminant p,p'-DDE and fluctuations in vole availability on the population dynamics of Burrowing Owls (Athene cunicularia). Previous work indicated an interaction between low biomass of voles in the diet and moderate levels of p,p'-DDE in Burrowing Owl eggs that led to reproductive impairment. We constructed periodic and stochastic matrix models that incorporated three vole population states observed in the field: average, peak, and crash years. We modeled varying frequencies of vole crash years and a range of impairment of owl demographic rates in vole crash years. Vole availability had a greater impact on owl population growth rate than did reproductive impairment if vole populations peaked and crashed frequently. However, this difference disappeared as the frequency of vole crash years declined to once per decade. Fecundity, the demographic rate most affected by p,p'-DDE, had less impact on population growth rate than adult or juvenile survival. A life table response experiment of time-invariant matrices for average, peak, and crash vole conditions showed that low population growth under vole crash conditions was due to low adult and juvenile survival rates, whereas the extremely high population growth under vole peak conditions was due to increased fecundity. Our results suggest that even simple models can provide useful insights into complex ecological interactions. This is particularly valuable when temporal or spatial scales preclude manipulative experimental work in the field or laboratory. PMID:16711053

  11. Identifying consumer-resource population dynamics using paleoecological data.

    PubMed

    Einarsson, Árni; Hauptfleisch, Ulf; Leavitt, Peter R; Ives, Anthony R

    2016-02-01

    Ecologists have long been fascinated by cyclic population fluctuations, because they suggest strong interactions between exploiter and victim species. Nonetheless, even for populations showing high-amplitude fluctuations, it is often hard to identify which species are the key drivers of the dynamics, because data are generally only available for a single species. Here, we use a paleoecological approach to investigate fluctuations in the midge population in Lake Mývatn, Iceland, which ranges over several orders of magnitude in irregular, multigeneration cycles. Previous circumstantial evidence points to consumer-resource interactions between midges and their primary food, diatoms, as the cause of these high-amplitude fluctuations. Using a pair of sediment cores from the lake, we reconstructed 26 years of dynamics of midges using egg remains and of algal groups using diagnostic pigments. We analyzed these data using statistical methods that account for both the autocorrelated nature of paleoecological data and measurement error caused by the mixing of sediment layers. The analyses revealed a signature of consumer-resource interactions in the fluctuations of midges and diatoms: diatom abundance (as inferred from biomarker pigment diatoxanthin) increased when midge abundance was low, and midge abundance (inferred from egg capsules) decreased when diatom abundance was low. Similar patterns were not found for pigments characterizing the other dominant primary producer group in the lake (cyanobacteria), subdominant algae (cryptophytes), or ubiquitous but chemically unstable biomarkers of total algal abundance (chlorophyll a); however, a significant but weaker pattern was found for the chemically stable indicator of total algal populations (β-carotene) to which diatoms are the dominant contributor. These analyses provide the first paleoecological evaluation of specific trophic interactions underlying high amplitude population fluctuations in lakes. PMID:27145611

  12. How Archiving by Freezing Affects the Genome-Scale Diversity of Escherichia coli Populations.

    PubMed

    Sprouffske, Kathleen; Aguilar-Rodríguez, José; Wagner, Andreas

    2016-01-01

    In the experimental evolution of microbes such as Escherichia coli, many replicate populations are evolved from a common ancestor. Freezing a population sample supplemented with the cryoprotectant glycerol permits later analysis or restarting of an evolution experiment. Typically, each evolving population, and thus each sample archived in this way, consists of many unique genotypes and phenotypes. The effect of archiving on such a heterogeneous population is unknown. Here, we identified optimal archiving conditions for E. coli. We also used genome sequencing of archived samples to study the effects that archiving has on genomic population diversity. We observed no allele substitutions and mostly small changes in allele frequency. Nevertheless, principal component analysis of genome-scale allelic diversity shows that archiving affects diversity across many loci. We showed that this change in diversity is due to selection rather than drift. In addition, ∼1% of rare alleles that occurred at low frequencies were lost after treatment. Our observations imply that archived populations may be used to conduct fitness or other phenotypic assays of populations, in which the loss of a rare allele may have negligible effects. However, caution is appropriate when sequencing populations restarted from glycerol stocks, as well as when using glycerol stocks to restart or replay evolution. This is because the loss of rare alleles can alter the future evolutionary trajectory of a population if the lost alleles were strongly beneficial. PMID:26988250

  13. How Archiving by Freezing Affects the Genome-Scale Diversity of Escherichia coli Populations

    PubMed Central

    Sprouffske, Kathleen; Aguilar-Rodríguez, José; Wagner, Andreas

    2016-01-01

    In the experimental evolution of microbes such as Escherichia coli, many replicate populations are evolved from a common ancestor. Freezing a population sample supplemented with the cryoprotectant glycerol permits later analysis or restarting of an evolution experiment. Typically, each evolving population, and thus each sample archived in this way, consists of many unique genotypes and phenotypes. The effect of archiving on such a heterogeneous population is unknown. Here, we identified optimal archiving conditions for E. coli. We also used genome sequencing of archived samples to study the effects that archiving has on genomic population diversity. We observed no allele substitutions and mostly small changes in allele frequency. Nevertheless, principal component analysis of genome-scale allelic diversity shows that archiving affects diversity across many loci. We showed that this change in diversity is due to selection rather than drift. In addition, ∼1% of rare alleles that occurred at low frequencies were lost after treatment. Our observations imply that archived populations may be used to conduct fitness or other phenotypic assays of populations, in which the loss of a rare allele may have negligible effects. However, caution is appropriate when sequencing populations restarted from glycerol stocks, as well as when using glycerol stocks to restart or replay evolution. This is because the loss of rare alleles can alter the future evolutionary trajectory of a population if the lost alleles were strongly beneficial. PMID:26988250

  14. Survival and Population Dynamics of the Marabou Stork in an Isolated Population, Swaziland

    PubMed Central

    Monadjem, Ara; Kane, Adam; Botha, Andre; Dalton, Desire; Kotze, Antoinette

    2012-01-01

    Investigating the ecology of long lived birds is particularly challenging owing to the time scales involved. Here an analysis is presented of a long term study of the survival and population dynamics of the marabou stork (Leptoptilos crumeniferus), a wide ranging scavenging bird from Sub-Saharan Africa. Using resightings data of tagged nestlings and free flying birds we show that the stork population can be divided into three general life stages with unique survival probabilities and fecundities. Fecundity of the storks is inversely related to rainfall during their breeding season. Corroborative evidence for a metapopulation structure is discussed highlighting the impact of the Swaziland birds on the ecology of the species in the broader region. The importance of tag loss or illegibility over time is highlighted. Clearly, any attempt at conserving a species will require a detailed understanding of its population structure, of the sort examined here. PMID:23029517

  15. Size-dependent mortality induces life-history changes mediated through population dynamical feedbacks.

    PubMed

    van Kooten, Tobias; Persson, Lennart; de Roos, André M

    2007-08-01

    The majority of taxa grow significantly during life history, which often leads to individuals of the same species having different ecological roles, depending on their size or life stage. One aspect of life history that changes during ontogeny is mortality. When individual growth and development are resource dependent, changes in mortality can affect the outcome of size-dependent intraspecific resource competition, in turn affecting both life history and population dynamics. We study the outcome of varying size-dependent mortality on two life-history types, one that feeds on the same resource throughout life history and another that can alternatively cannibalize smaller conspecifics. Compensatory responses in the life history dampen the effect of certain types of size-dependent mortality, while other types of mortality lead to dramatic changes in life history and population dynamics, including population (de-)stabilization, and the growth of cannibalistic giants. These responses differ strongly among the two life-history types. Our analysis provides a mechanistic understanding of the population-level effects that come about through the interaction between individual growth and size-dependent mortality, mediated by resource dependence in individual vital rates. PMID:17874376

  16. Molecular crowding causes narrowing of population heterogeneity and restricts internal dynamics in a protein

    NASA Astrophysics Data System (ADS)

    Mondal, Samsuzzoha; Kallianpur, Mamata V.; Udgaonkar, Jayant B.; Krishnamoorthy, G.

    2016-03-01

    Macromolecular crowding is a distinguishing property of intracellular media. Knowledge on the structure and dynamics of a protein in a crowded environment is essential for a complete understanding of its function. Reduction in intermolecular space could cause structural and functional alterations. Here, we have studied a model protein barstar to see how polyethylene glycol (PEG)-induced crowding affects its various structural states (native, unfolded and molten-globule-like) with different extents of change in conformational heterogeneity. Intramolecular distances and distance distributions were determined by time-resolved Förster resonance energy transfer from Trp53 to several acceptor sites by analysis of fluorescence decay kinetics using the Maximum Entropy Method. We observed PEG-induced narrowing of population distributions along with shifting of populations towards more compact states. Structural compactness also resulted in the slowing down of internal dynamics of the protein as revealed by fluorescence anisotropy decay kinetics of the fluorophore IAEDANS attached at several sites.

  17. Dynamics of Affective Experience and Behavior in Depressed Adolescents

    ERIC Educational Resources Information Center

    Sheeber, Lisa B.; Allen, Nicholas B.; Leve, Craig; Davis, Betsy; Shortt, Joann Wu; Katz, Lynn Fainsilber

    2009-01-01

    Background: Depression is often characterized as a disorder of affect regulation. However, research focused on delineating the key dimensions of affective experience (other than valence) that are abnormal in depressive disorder has been scarce, especially in child and adolescent samples. As definitions of affect regulation center around processes…

  18. A Hierarchical Latent Stochastic Differential Equation Model for Affective Dynamics

    ERIC Educational Resources Information Center

    Oravecz, Zita; Tuerlinckx, Francis; Vandekerckhove, Joachim

    2011-01-01

    In this article a continuous-time stochastic model (the Ornstein-Uhlenbeck process) is presented to model the perpetually altering states of the core affect, which is a 2-dimensional concept underlying all our affective experiences. The process model that we propose can account for the temporal changes in core affect on the latent level. The key…

  19. Evolutionary dynamics for persistent cooperation in structured populations

    NASA Astrophysics Data System (ADS)

    Li, Yan; Liu, Xinsheng; Claussen, Jens Christian; Guo, Wanlin

    2015-06-01

    The emergence and maintenance of cooperative behavior is a fascinating topic in evolutionary biology and social science. The public goods game (PGG) is a paradigm for exploring cooperative behavior. In PGG, the total resulting payoff is divided equally among all participants. This feature still leads to the dominance of defection without substantially magnifying the public good by a multiplying factor. Much effort has been made to explain the evolution of cooperative strategies, including a recent model in which only a portion of the total benefit is shared by all the players through introducing a new strategy named persistent cooperation. A persistent cooperator is a contributor who is willing to pay a second cost to retrieve the remaining portion of the payoff contributed by themselves. In a previous study, this model was analyzed in the framework of well-mixed populations. This paper focuses on discussing the persistent cooperation in lattice-structured populations. The evolutionary dynamics of the structured populations consisting of three types of competing players (pure cooperators, defectors, and persistent cooperators) are revealed by theoretical analysis and numerical simulations. In particular, the approximate expressions of fixation probabilities for strategies are derived on one-dimensional lattices. The phase diagrams of stationary states, and the evolution of frequencies and spatial patterns for strategies are illustrated on both one-dimensional and square lattices by simulations. Our results are consistent with the general observation that, at least in most situations, a structured population facilitates the evolution of cooperation. Specifically, here we find that the existence of persistent cooperators greatly suppresses the spreading of defectors under more relaxed conditions in structured populations compared to that obtained in well-mixed populations.

  20. a Simple Probabilistic, Biologically Informed Model of the Population Dynamics of Desert Shrubs

    NASA Astrophysics Data System (ADS)

    Worman, S.; Furbish, D. J.; Clarke, J. H.; Roberts, A. S.

    2010-12-01

    In arid environments, spatiotemporal variations in the processes of erosion and deposition are strongly coupled with the structure and dynamics of plant communities as well as the specific life behavior of individual plants. Understanding how physical transport processes affect the evolution of the land surface on geomorphic time-scales therefore requires considering how long-term changes in plant dynamics may in turn impact such processes. The development of this desert shrub population dynamics model is therefore motivated by the need to link rain-splash induced mound building at the shrub-scale with the unfolding ‘biological play’ occurring on a hillslope. Using the Master Equation to conserve shrub age, probabilistic and biologically informed statements for recruitment and mortality are formulated to function as source and sink terms respectively. This simple accounting framework, by tracking the number of individuals entering and leaving a population, captures the changes in shrub count that can be expected in time as the key variables driving the dynamics of these plant communities (i.e. precipitation) also change in time. The result is a tool through which it is possible to statistically describe the aggregate spatiotemporal behavior of different shrub populations, with their own characteristic life-cycles and physical dimensions, under different external forcing scenarios. This model features inputs that have a solid biophysical basis and insofar as it has the capacity to mimic key features of real processes, leads to outputs which appear consistent with findings reported in the literature.

  1. Tillage and Multiple Cropping Systems and Population Dynamics of Phytoparasitic Nematodes

    PubMed Central

    Gallaher, R. N.; Dickson, D. W.; Corella, J. F.; Hewlett, T. E.

    1988-01-01

    The effect of two cropping and tillage systems on the population dynamics of four nematode species was evaluated on a loamy sand. Hairy vetch succeeded by corn or grain sorghum was seeded in split plots randomized within whole plots of no-tillage versus conventional tillage over four growing seasons (1980-83). The vetch-corn cropping system increased the density of Meloidogyne incognita 2.9 x more than the vetch-grain sorghum cropping system. In contrast, the vetch-grain sorghum cropping system increased the density of Criconemella ornata 0.7 x more than the vetch-corn cropping system. Meloidogyne incognita and C. ornata were affected more by these cropping systems than were Pratylenchus brachyurus or Paratrichodorus minor. Multiple cropping systems, vetch varieties, and crop host preference affected nematode population densities, whereas tillage treatments, conventional or no-tillage, had little effect on them. PMID:19290311

  2. Slicing and dicing globular clusters: dynamically evolved single stellar populations

    NASA Astrophysics Data System (ADS)

    Sippel, Anna C.; Hurley, Jarrod R.

    2016-04-01

    We utilize direct N-body models of globular clusters including stellar evolution to calculate magnitudes for each star in the Hubble Space Telescope Advanced Camera for Surveys 555, 606 and 814 filters. This enables us to analyse the colour of dynamically evolved single stellar populations over time in colour-magnitude diagrams of both, resolved and integrated globular clusters. We find that the change of integrated cluster colour is driven predominantly by the colour of the brightest stars available and hence by stellar evolution, but not by the removal of low-mass stars. We show that even in mass-segregated clusters, different stellar populations are distributed over the entire cluster. This implies that evolved stars also exist within and outside the half-mass radius.

  3. State-dependent neutral delay equations from population dynamics.

    PubMed

    Barbarossa, M V; Hadeler, K P; Kuttler, C

    2014-10-01

    A novel class of state-dependent delay equations is derived from the balance laws of age-structured population dynamics, assuming that birth rates and death rates, as functions of age, are piece-wise constant and that the length of the juvenile phase depends on the total adult population size. The resulting class of equations includes also neutral delay equations. All these equations are very different from the standard delay equations with state-dependent delay since the balance laws require non-linear correction factors. These equations can be written as systems for two variables consisting of an ordinary differential equation (ODE) and a generalized shift, a form suitable for numerical calculations. It is shown that the neutral equation (and the corresponding ODE--shift system) is a limiting case of a system of two standard delay equations. PMID:25117688

  4. The island syndrome and population dynamics of introduced rats.

    PubMed

    Russell, James C; Ringler, David; Trombini, Aurélien; Le Corre, Matthieu

    2011-11-01

    The island syndrome predicts directional changes in the morphology and demography of insular vertebrates, due to changes in trophic complexity and migration rates caused by island size and isolation. However, the high rate of human-mediated species introductions to some islands also increases trophic complexity, and this will reduce the perceived insularity on any such island. We test four hypotheses on the role of increased trophic complexity on the island syndrome, using introduced black rats (Rattus rattus) on two isolated coral atolls in the Mozambique Channel. Europa Island has remained relatively pristine and insular, with few species introductions, whereas Juan de Nova Island has had many species introductions, including predators and competitors of rats, anthropogenically increasing its trophic complexity. In the most insular environments, the island syndrome is expected to generate increases in body size and densities of rodents but decreases in the rates of reproduction and population cycling. Morphology and reproduction were compared using linear regression and canonical discriminant analysis, while density and population cycling were compared using spatially explicit capture-recapture analysis. Results were compared to other insular black rat populations in the Mozambique Channel and were consistent with predictions from the island syndrome. The manifestation of an island syndrome in rodents depends upon the trophic composition of a community, and may not relate to island size alone when many species additions, such as invasions, have occurred. The differing patterns of rodent population dynamics on each island provide information for future rodent eradication operations. PMID:21643994

  5. Evolutionary game dynamics in populations with different learners

    PubMed Central

    Chatterjee, Krishnendu; Zufferey, Damien; Nowak, Martin A.

    2012-01-01

    We study evolutionary game theory in a setting where individuals learn from each other. We extend the traditional approach by assuming that a population contains individuals with different learning abilities. In particular we explore the situation where individuals have different search spaces, when attempting to learn the strategies of others. The search space of an individual specifies the set of strategies learnable by that individual. The search space is genetically given and does not change under social evolutionary dynamics. We introduce a general framework and study a specific example in the context of direct reciprocity. For this example we obtain the counter intuitive result that cooperation can only evolve for intermediate benefit-to-cost ratios, while small and large benefit-to-cost ratios favor defection. Our paper is a step toward making a connection between computational learning theory and evolutionary game dynamics. PMID:22394652

  6. Population Dynamics of Patients with Bacterial Resistance in Hospital Environment.

    PubMed

    Qu, Leilei; Pan, Qiuhui; Gao, Xubin; He, Mingfeng

    2016-01-01

    During the past decades, the increase of antibiotic resistance has become a major concern worldwide. The researchers found that superbugs with new type of resistance genes (NDM-1) have two aspects of transmission characteristics; the first is that the antibiotic resistance genes can horizontally transfer among bacteria, and the other is that the superbugs can spread between humans through direct contact. Based on these two transmission mechanisms, we study the dynamics of population in hospital environment where superbugs exist. In this paper, we build three mathematic models to illustrate the dynamics of patients with bacterial resistance in hospital environment. The models are analyzed using stability theory of differential equations. Positive equilibrium points of the system are investigated and their stability analysis is carried out. Moreover, the numerical simulation of the proposed model is also performed which supports the theoretical findings. PMID:26904150

  7. Population Dynamics of Patients with Bacterial Resistance in Hospital Environment

    PubMed Central

    Qu, Leilei; Pan, Qiuhui; Gao, Xubin; He, Mingfeng

    2016-01-01

    During the past decades, the increase of antibiotic resistance has become a major concern worldwide. The researchers found that superbugs with new type of resistance genes (NDM-1) have two aspects of transmission characteristics; the first is that the antibiotic resistance genes can horizontally transfer among bacteria, and the other is that the superbugs can spread between humans through direct contact. Based on these two transmission mechanisms, we study the dynamics of population in hospital environment where superbugs exist. In this paper, we build three mathematic models to illustrate the dynamics of patients with bacterial resistance in hospital environment. The models are analyzed using stability theory of differential equations. Positive equilibrium points of the system are investigated and their stability analysis is carried out. Moreover, the numerical simulation of the proposed model is also performed which supports the theoretical findings. PMID:26904150

  8. Auctions with Dynamic Populations: Efficiency and Revenue Maximization

    NASA Astrophysics Data System (ADS)

    Said, Maher

    We study a stochastic sequential allocation problem with a dynamic population of privately-informed buyers. We characterize the set of efficient allocation rules and show that a dynamic VCG mechanism is both efficient and periodic ex post incentive compatible; we also show that the revenue-maximizing direct mechanism is a pivot mechanism with a reserve price. We then consider sequential ascending auctions in this setting, both with and without a reserve price. We construct equilibrium bidding strategies in this indirect mechanism where bidders reveal their private information in every period, yielding the same outcomes as the direct mechanisms. Thus, the sequential ascending auction is a natural institution for achieving either efficient or optimal outcomes.

  9. Mosquito population dynamics from cellular automata-based simulation

    NASA Astrophysics Data System (ADS)

    Syafarina, Inna; Sadikin, Rifki; Nuraini, Nuning

    2016-02-01

    In this paper we present an innovative model for simulating mosquito-vector population dynamics. The simulation consist of two stages: demography and dispersal dynamics. For demography simulation, we follow the existing model for modeling a mosquito life cycles. Moreover, we use cellular automata-based model for simulating dispersal of the vector. In simulation, each individual vector is able to move to other grid based on a random walk. Our model is also capable to represent immunity factor for each grid. We simulate the model to evaluate its correctness. Based on the simulations, we can conclude that our model is correct. However, our model need to be improved to find a realistic parameters to match real data.

  10. Population-dynamics method with a multicanonical feedback control

    NASA Astrophysics Data System (ADS)

    Nemoto, Takahiro; Bouchet, Freddy; Jack, Robert L.; Lecomte, Vivien

    2016-06-01

    We discuss the Giardinà-Kurchan-Peliti population dynamics method for evaluating large deviations of time-averaged quantities in Markov processes [Phys. Rev. Lett. 96, 120603 (2006), 10.1103/PhysRevLett.96.120603]. This method exhibits systematic errors which can be large in some circumstances, particularly for systems with weak noise, with many degrees of freedom, or close to dynamical phase transitions. We show how these errors can be mitigated by introducing control forces within the algorithm. These forces are determined by an iteration-and-feedback scheme, inspired by multicanonical methods in equilibrium sampling. We demonstrate substantially improved results in a simple model, and we discuss potential applications to more complex systems.

  11. Population-dynamics method with a multicanonical feedback control.

    PubMed

    Nemoto, Takahiro; Bouchet, Freddy; Jack, Robert L; Lecomte, Vivien

    2016-06-01

    We discuss the Giardinà-Kurchan-Peliti population dynamics method for evaluating large deviations of time-averaged quantities in Markov processes [Phys. Rev. Lett. 96, 120603 (2006)PRLTAO0031-900710.1103/PhysRevLett.96.120603]. This method exhibits systematic errors which can be large in some circumstances, particularly for systems with weak noise, with many degrees of freedom, or close to dynamical phase transitions. We show how these errors can be mitigated by introducing control forces within the algorithm. These forces are determined by an iteration-and-feedback scheme, inspired by multicanonical methods in equilibrium sampling. We demonstrate substantially improved results in a simple model, and we discuss potential applications to more complex systems. PMID:27415224

  12. Front acceleration by dynamic selection in Fisher population waves

    NASA Astrophysics Data System (ADS)

    Bénichou, O.; Calvez, V.; Meunier, N.; Voituriez, R.

    2012-10-01

    We introduce a minimal model of population range expansion in which the phenotypes of individuals present no selective advantage and differ only in their diffusion rate. We show that such neutral phenotypic variability (i.e., that does not modify the growth rate) alone can yield phenotype segregation at the front edge, even in absence of genetic noise, and significantly impact the dynamical properties of the expansion wave. We present an exact asymptotic traveling wave solution and show analytically that phenotype segregation accelerates the front propagation. The results are compatible with field observations such as invasions of cane toads in Australia or bush crickets in Britain.

  13. Periodically varying externally imposed environmental effects on population dynamics

    NASA Astrophysics Data System (ADS)

    Ballard, M.; Kenkre, V. M.; Kuperman, M. N.

    2004-09-01

    Effects of externally imposed periodic changes in the environment on population dynamics are studied with the help of a simple model. The environmental changes are represented by the temporal and spatial dependence of the competition terms in a standard equation of evolution. Possible applications of the analysis are on the one hand to bacteria in Petri dishes and on the other to rodents in the context of the spread of the Hantavirus epidemic. The analysis shows that spatiotemporal structures emerge, with interesting features which depend on the interplay of separately controllable aspects of the externally imposed environmental changes.

  14. Time-delayed coupled logistic capacity model in population dynamics

    NASA Astrophysics Data System (ADS)

    Cáceres, Manuel O.

    2014-08-01

    This study proposes a delay-coupled system based on the logistic equation that models the interaction of a population with its varying environment. The integro-diferential equations of the model are presented in terms of a distributed time-delayed coupled logistic-capacity equation. The model eliminates the need for a prior knowledge of the maximum saturation environmental carrying capacity value. Therefore the dynamics toward the final attractor in a distributed time-delayed coupled logistic-capacity model is studied. Exact results are presented, and analytical conclusions have been done in terms of the two parameters of the model.

  15. Monitored and modeled coral population dynamics and the refuge concept.

    PubMed

    Riegl, B; Purkis, S J; Keck, J; Rowlands, G P

    2009-01-01

    With large-scale impacts on coral reefs due to global climatic change projected to increase dramatically, and suitability of many areas for reef growth projected to decrease, the question arises whether particular settings might serve as refugia that can maintain higher coral populations than surrounding areas. We examine this hypothesis on a small, local scale in Honduras, western Caribbean. Dense coral thickets containing high numbers of the endangered coral Acropora cervicornis occur on offshore banks while being rare on the fringing reef on nearby Roatán. Geomorphological setting and community dynamics were evaluated and monitored from 1996 to 2005. A model of population dynamics was developed to test assumptions derived from monitoring. Coral cover on the fringing reef declined in 1998 from >30% to <20%, but the banks maintained areas of very dense coral cover (32% cover by A. cervicornis on the banks but <1% on the fringing reef). Bathymetry from satellite images showed the banks to be well-separated from the fringing reef, making asexual connectivity between banks and fringing reef impossible but protecting the banks from direct land-runoff during storms. Exposure to SE tradewinds also causes good flushing. Only four A. cervicornis recruits were recorded on the fringing reef over 6 years. Runoff associated with hurricanes caused greater mortality than did bleaching in 1998 and 2005 on the fringing reef, but not on the banks. Since 1870, our analysis suggests that corals on the banks may have been favored during 17 runoff events associated with tropical depressions and storms and potentially also during five bleaching events, but this is more uncertain. Our model suggests that under this disturbance regime, the banks will indeed maintain higher coral populations than the fringing reef and supports the assumption that offshore banks could serve as refugia with the capacity to subsidize depleted mainland populations. PMID:19100585

  16. Inferring population and metapopulation dynamics of Liparis loeselii from single-census and inventory data

    NASA Astrophysics Data System (ADS)

    Oostermeijer, J. G. B.; Hartman, Y.

    2014-10-01

    To conserve endangered species, information is needed on (meta)population responses to habitat quality and management. As possibilities for long-term studies are generally limited, it is important to obtain as much information as possible in a single field season. We obtained such single-census data for the orchid Liparis loeselii, a European Habitat Directive species. Stage structures of 15 Dutch dune and fen populations were related to vegetation structure, environmental indicators, and management. Botanical inventory records from 1930 to 2003 were used to infer population life spans. Cluster analysis did not reveal successional stage structure types. Dense populations with high recruitment mainly occurred in open, young-successional vegetation with high soil pH. High soil humidity and acidification negatively affected orchid densities. Early mowing was preferable over late mowing in dune slacks, because the latter reduced juvenile densities. The predominant population life span was three to eight years, and similar for dune slacks and fens. Longer life spans were occasionally observed at mown sites with influx of base-rich water. Our results suggest high metapopulation dynamics. Long-term metapopulation viability requires the formation of new habitat by dune slack formation in dunes and peat removal in fens. Population persistence can be prolonged to some extent by mowing, extensive grazing, or sod removal if natural habitat formation is impossible. Our study demonstrates that useful information on (meta)population ecology and viability can be obtained in a single field season.

  17. Defoliation by pastoralists affects savanna tree seedling dynamics by limiting the facilitative role of canopy cover.

    PubMed

    Bufford, Jennifer L; Gaoue, Orou G

    2015-07-01

    Recurrent tree defoliation by pastoralists, akin to herbivory, can negatively affect plant reproduction and population dynamics. However, our understanding of the indirect role of defoliation in seedling recruitment and tree-grass dynamics in tropical savanna is limited. In West African savanna, Fulani pastoralists frequently defoliate several fodder tree species to feed livestock in the dry season. We investigated the direct and indirect effects of recurrent defoliation of African mahogany (Khaya senegalensis) by Fulani people on seedling (< 2 cm basal diameter) and sapling dynamics in West Africa using four years of demographic data on seedling and sapling density, growth, and survival, coupled with fruit production and microhabitat data over the same time period. Tree canopy cover facilitated seedlings but had negative effects on sapling growth possibly via intraspecific competition with adult plants. Interspecific competition with grasses strongly reduced seedling survival but had a weak effect on sapling growth. Fire reduced seedling survival and weakly reduced growth of seedlings and saplings, but did not affect sapling survival. These results indicate that the effect of fire on seedlings and saplings is distinct, a mechanism suitable for an episodic recruitment of seedlings into the sapling stage and consistent with predictions from the demographic bottleneck model. Defoliation affected seedling density and sapling growth through changes in canopy cover, but had no effect on seedling growth and sapling survival. In the moist region, sapling density was higher in sites with low-intensity defoliation, indicating that defoliation may strengthen the tree recruitment bottleneck. Our study suggests that large-scale defoliation can alter the facilitative role of nurse trees on seedling dynamics and tree-sapling competition. Given that tree defoliation by local people is a widespread activity throughout savanna-forest systems in West Africa, it has the potential to

  18. Dynamical analysis of seasonal migrating population; the effect of regular hunting to the coexistence

    NASA Astrophysics Data System (ADS)

    Sambas, T. J. M.; Khaliq, B. F.; Waluyo, D. S. Y. S.; Putra, P. S.; Soewono, E.

    2016-04-01

    Seasonal migration among wild populations is commonly seen especially in the wild life region. The migration takes place during a certain season where logistical condition and the existing territory can no longer support the life of the whole population. In this case portion of the population migrate to the better place as part of their survival, and returning back to the home place when the logistical condition is improved. Here we model the dynamic of North-South annual migration of Impala population in Zimbabwe, where portion of population in the Southern part move to the North in the beginning of the dry season and portion of them return back to the South in the wet season. Here the North area has a better environmental carrying capacity than the South. Different processes take place during the year, partial migration to the south (during the month of December and January), partial migration to the north (during the month of June and July), and birth process (during the month of November and December). We construct a discrete dynamical model for simulating the annual migrating process. It is found that a stable co-existence always occurs when no hunting takes place in all season. When hunting is allowed, the co-existence could be severely affected. We obtain here a threshold condition for co-existence and show numerical simulations for different hunting scenarios.

  19. Demographic heterogeneity and the dynamics of open populations.

    PubMed

    Noonburg, Erik G; Chen, Adam; Shima, Jeffrey S; Swearer, Stephen E

    2015-05-01

    Individuals vary in their phenotype and propensity for growth and survival, but the demographic consequences of this remain poorly understood. We extend previous theoretical work on benthic marine populations and formulate a new model to evaluate how demographic heterogeneity among newly settled reef fish affects population stability. We simulated settlement, growth, and mortality of a small reef fish, the common triplefin (Forsterygion lapillurn) in an open "subpopulation" using a delay-differential equation model framework. We modeled demographic heterogeneity with a discrete number of "quality" types, motivated by our previous empirical observations: individuals were either "high quality" (immigrants from nearby subpopulations) or "low quality" (immigrants from distant subpopulations); in our model, quality influences how quickly individuals develop at a given competitor density. Our results demonstrate how demographic heterogeneity and juvenile competition interact to qualitatively alter the effects of settlement on population stability. Specifically, our model suggests that a mixture of quality types can stabilize the equilibrium even when equal settlement of either type alone would result in an unstable equilibrium. These results highlight the importance of among-individual variation in a metapopulation context, and suggest that in systems where dispersal influences individual quality, connectivity may serve to stabilize local populations. PMID:26236830

  20. [On the relation between encounter rate and population density: Are classical models of population dynamics justified?].

    PubMed

    Nedorezov, L V

    2015-01-01

    A stochastic model of migrations on a lattice and with discrete time is considered. It is assumed that space is homogenous with respect to its properties and during one time step every individual (independently of local population numbers) can migrate to nearest nodes of lattice with equal probabilities. It is also assumed that population size remains constant during certain time interval of computer experiments. The following variants of estimation of encounter rate between individuals are considered: when for the fixed time moments every individual in every node of lattice interacts with all other individuals in the node; when individuals can stay in nodes independently, or can be involved in groups in two, three or four individuals. For each variant of interactions between individuals, average value (with respect to space and time) is computed for various values of population size. The samples obtained were compared with respective functions of classic models of isolated population dynamics: Verhulst model, Gompertz model, Svirezhev model, and theta-logistic model. Parameters of functions were calculated with least square method. Analyses of deviations were performed using Kolmogorov-Smirnov test, Lilliefors test, Shapiro-Wilk test, and other statistical tests. It is shown that from traditional point of view there are no correspondence between the encounter rate and functions describing effects of self-regulatory mechanisms on population dynamics. Best fitting of samples was obtained with Verhulst and theta-logistic models when using the dataset resulted from the situation when every individual in the node interacts with all other individuals. PMID:26606790

  1. Population dynamics of minimally cognitive individuals. Part I: Introducing knowledge into the dynamics

    SciTech Connect

    Schmieder, R.W.

    1995-07-01

    The author presents a new approach for modeling the dynamics of collections of objects with internal structure. Based on the fact that the behavior of an individual in a population is modified by its knowledge of other individuals, a procedure for accounting for knowledge in a population of interacting objects is presented. It is assumed that each object has partial (or complete) knowledge of some (or all) other objects in the population. The dynamical equations for the objects are then modified to include the effects of this pairwise knowledge. This procedure has the effect of projecting out what the population will do from the much larger space of what it could do, i.e., filtering or smoothing the dynamics by replacing the complex detailed physical model with an effective model that produces the behavior of interest. The procedure therefore provides a minimalist approach for obtaining emergent collective behavior. The use of knowledge as a dynamical quantity, and its relationship to statistical mechanics, thermodynamics, information theory, and cognition microstructure are discussed.

  2. Effects of harvest and climate on population dynamics of northern bobwhites in south Florida

    USGS Publications Warehouse

    Rolland, V.; Hostetler, J.A.; Hines, T.C.; Johnson, F.A.; Percival, H.F.; Oli, M.K.

    2011-01-01

    Context Hunting-related (hereafter harvest) mortality is assumed to be compensatory in many exploited species. However, when harvest mortality is additive, hunting can lead to population declines, especially on public land where hunting pressure can be intense. Recent studies indicate that excessive hunting may have contributed to the decline of a northern bobwhite (Colinus virginianus) population in south Florida. Aims This study aimed to estimate population growth rates to determine potential and actual contribution of vital rates to annual changes in population growth rates, and to evaluate the role of harvest and climatic variables on bobwhite population decline. Methods We used demographic parameters estimated from a six-year study to parameterise population matrix models and conduct prospective and retrospective perturbation analyses. Key results The stochastic population growth rate (?? S=0.144) was proportionally more sensitive to adult winter survival and survival of fledglings, nests and broods from first nesting attempts; the same variables were primarily responsible for annual changes in population growth rate. Demographic parameters associated with second nesting attempts made virtually no contribution to population growth rate. All harvest scenarios consistently revealed a substantial impact of harvest on bobwhite population dynamics. If the lowest harvest level recorded in the study period (i.e. 0.08 birds harvested per day per km2 in 2008) was applied, S would increase by 32.1%. Winter temperatures and precipitation negatively affected winter survival, and precipitation acted synergistically with harvest in affecting winter survival. Conclusions Our results suggest that reduction in winter survival due to overharvest has been an important cause of the decline in our study population, but that climatic factors might have also played a role. Thus, for management actions to be effective, assessing the contribution of primary (e.g. harvesting) but also

  3. Multiplicative and Additive Modulation of Neuronal Tuning with Population Activity Affects Encoded Information.

    PubMed

    Arandia-Romero, Iñigo; Tanabe, Seiji; Drugowitsch, Jan; Kohn, Adam; Moreno-Bote, Rubén

    2016-03-16

    Numerous studies have shown that neuronal responses are modulated by stimulus properties and also by the state of the local network. However, little is known about how activity fluctuations of neuronal populations modulate the sensory tuning of cells and affect their encoded information. We found that fluctuations in ongoing and stimulus-evoked population activity in primate visual cortex modulate the tuning of neurons in a multiplicative and additive manner. While distributed on a continuum, neurons with stronger multiplicative effects tended to have less additive modulation and vice versa. The information encoded by multiplicatively modulated neurons increased with greater population activity, while that of additively modulated neurons decreased. These effects offset each other so that population activity had little effect on total information. Our results thus suggest that intrinsic activity fluctuations may act as a "traffic light" that determines which subset of neurons is most informative. PMID:26924437

  4. Effects of plant genotype and insect dispersal rate on the population dynamics of a forest pest.

    PubMed

    Moran, Emily V; Bewick, Sharon; Cobbold, Christina A

    2013-12-01

    It has been shown that plant genotype can strongly affect not only individual herbivore performance, but also community composition and ecosystem function. Few studies, however, have addressed how plant genotype affects herbivore population dynamics. In this paper, we used a simulation modeling approach to ask how the genetic composition of a forest influences pest outbreak dynamics, using the example of aspen (Populus tremuloides) and forest tent caterpillars (FTC; Malacosoma disstria). Specifically, we examined how plant genotype, the relative size of genotypic patches, and the rate of insect dispersal between them, affect the frequency, amplitude, and duration of outbreaks. We found that coupling two different genotypes does not necessarily result in an averaging of insect dynamics. Instead, depending on the ratio of patch sizes, when dispersal rates are moderate, outbreaks in the two-genotype case may be more or less severe than in forests of either genotype alone. Thresholds for different dynamic behaviors were similar for all genotypic combinations. Thus, the qualitative behavior of a stand of two different genotypes can be predicted based on the response of the insect to each genotype, the relative sizes of the two patches, and the scale of insect dispersal. PMID:24597225

  5. Population dynamics of minimally cognitive individuals. Part 2: Dynamics of time-dependent knowledge

    SciTech Connect

    Schmieder, R.W.

    1995-07-01

    The dynamical principle for a population of interacting individuals with mutual pairwise knowledge, presented by the author in a previous paper for the case of constant knowledge, is extended to include the possibility that the knowledge is time-dependent. Several mechanisms are presented by which the mutual knowledge, represented by a matrix K, can be altered, leading to dynamical equations for K(t). The author presents various examples of the transient and long time asymptotic behavior of K(t) for populations of relatively isolated individuals interacting infrequently in local binary collisions. Among the effects observed in the numerical experiments are knowledge diffusion, learning transients, and fluctuating equilibria. This approach will be most appropriate to small populations of complex individuals such as simple animals, robots, computer networks, agent-mediated traffic, simple ecosystems, and games. Evidence of metastable states and intermittent switching leads them to envision a spectroscopy associated with such transitions that is independent of the specific physical individuals and the population. Such spectra may serve as good lumped descriptors of the collective emergent behavior of large classes of populations in which mutual knowledge is an important part of the dynamics.

  6. Impact of simian immunodeficiency virus infection on chimpanzee population dynamics.

    PubMed

    Rudicell, Rebecca S; Holland Jones, James; Wroblewski, Emily E; Learn, Gerald H; Li, Yingying; Robertson, Joel D; Greengrass, Elizabeth; Grossmann, Falk; Kamenya, Shadrack; Pintea, Lilian; Mjungu, Deus C; Lonsdorf, Elizabeth V; Mosser, Anna; Lehman, Clarence; Collins, D Anthony; Keele, Brandon F; Goodall, Jane; Hahn, Beatrice H; Pusey, Anne E; Wilson, Michael L

    2010-01-01

    Like human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus of chimpanzees (SIVcpz) can cause CD4+ T cell loss and premature death. Here, we used molecular surveillance tools and mathematical modeling to estimate the impact of SIVcpz infection on chimpanzee population dynamics. Habituated (Mitumba and Kasekela) and non-habituated (Kalande) chimpanzees were studied in Gombe National Park, Tanzania. Ape population sizes were determined from demographic records (Mitumba and Kasekela) or individual sightings and genotyping (Kalande), while SIVcpz prevalence rates were monitored using non-invasive methods. Between 2002-2009, the Mitumba and Kasekela communities experienced mean annual growth rates of 1.9% and 2.4%, respectively, while Kalande chimpanzees suffered a significant decline, with a mean growth rate of -6.5% to -7.4%, depending on population estimates. A rapid decline in Kalande was first noted in the 1990s and originally attributed to poaching and reduced food sources. However, between 2002-2009, we found a mean SIVcpz prevalence in Kalande of 46.1%, which was almost four times higher than the prevalence in Mitumba (12.7%) and Kasekela (12.1%). To explore whether SIVcpz contributed to the Kalande decline, we used empirically determined SIVcpz transmission probabilities as well as chimpanzee mortality, mating and migration data to model the effect of viral pathogenicity on chimpanzee population growth. Deterministic calculations indicated that a prevalence of greater than 3.4% would result in negative growth and eventual population extinction, even using conservative mortality estimates. However, stochastic models revealed that in representative populations, SIVcpz, and not its host species, frequently went extinct. High SIVcpz transmission probability and excess mortality reduced population persistence, while intercommunity migration often rescued infected communities, even when immigrating females had a chance of being SIVcpz infected

  7. Effects of ocean acidification on population dynamics and community structure of crustose coralline algae.

    PubMed

    Ordoñez, Alexandra; Doropoulos, Christopher; Diaz-Pulido, Guillermo

    2014-06-01

    Calcification and growth of crustose coralline algae (CCA) are affected by elevated seawater pCO2 and associated changes in carbonate chemistry. However, the effects of ocean acidification (OA) on population and community-level responses of CCA have barely been investigated. We explored changes in community structure and population dynamics (size structure and reproduction) of CCA in response to OA. Recruited from an experimental flow-through system, CCA settled onto the walls of plastic aquaria and developed under exposure to one of three pCO2 treatments (control [present day, 389±6 ppm CO2], medium [753±11 ppm], and high [1267±19 ppm]). Elevated pCO2 reduced total CCA abundance and affected community structure, in particular the density of the dominant species Pneophyllum sp. and Porolithon onkodes. Meanwhile, the relative abundance of P. onkodes declined from 24% under control CO2 to 8.3% in high CO2 (65% change), while the relative abundance of Pneophyllum sp. remained constant. Population size structure of P. onkodes differed significantly across treatments, with fewer larger individuals under high CO2. In contrast, the population size structure and number of reproductive structures (conceptacles) per crust of Pneophyllum sp. was similar across treatments. The difference in the magnitude of the response of species abundance and population size structure between species may have the potential to induce species composition changes in the future. These results demonstrate that the impacts of OA on key coral reef builders go beyond declines in calcification and growth, and suggest important changes to aspects of population dynamics and community ecology. PMID:25070869

  8. [Population dynamics of thrushes and seasonal resource partition].

    PubMed

    Burskiĭ, O V; Demidova, E Iu; Morkovin, A A

    2014-01-01

    We studied seasonal population dynamics in birds using four thrush species from the Yenisei middle taiga region as an example. Long-term data on bird route censuses, capture-mark-recapture, and nest observa- tions were incorporated in the analysis. Particularly, methodological problems that complicate a direct comparison between assessed numbers at different phases of the annual cycle are considered. The integrated analysis of the results allowed comparing changes in numbers, energy expenditure, age structure, migrating status, and density distribution of selected populations during the snowless period and relating them to seasonal changes in food resource abundance. Thrush population numbers within the breeding range, and their energy consumption in the Yenisei middle taiga proportionately reflect the seasonal change in abundance of food resources. The compliance between resource intake and carrying capacity of the environment is attained by: timing of arrival and departure regarding to the species' range of tolerance; change in numbers as a result of reproduction and mortality; change in numbers due to habitat changes and long-distance movements; increasing energetic expenditures during reproduction and molt; timing, intensity and replication of nesting attempts; timing of molt and proportion of molting individuals in a population; individual variations of the annual cycle. Reproductive growth of local bird populations is not fast enough to catch up with seasonal growth of ecosystems productivity. Superabundance of invertebrates at the peak of the season offers a temporal niche which, on the one hand, is suitable for species capable of diet switching, while, on the other hand, may be used by specialized consumers, namely tropical migrants for whom, at high resource level, a shortened breeding period suffices. PMID:25786310

  9. Population size and relatedness affect fitness of a self-incompatible invasive plant.

    PubMed

    Elam, Diane R; Ridley, Caroline E; Goodell, Karen; Ellstrand, Norman C

    2007-01-01

    One of the lingering paradoxes in invasion biology is how founder populations of an introduced species are able to overcome the limitations of small size and, in a "reversal of fortune," proliferate in a new habitat. The transition from colonist to invader is especially enigmatic for self-incompatible species, which must find a mate to reproduce. In small populations, the inability to find a mate can result in the Allee effect, a positive relationship between individual fitness and population size or density. Theoretically, the Allee effect should be common in founder populations of self-incompatible colonizing species and may account for the high rate of failed introductions, but little supporting evidence exists. We created a field experiment to test whether the Allee effect affects the maternal fitness of a self-incompatible invasive species, wild radish (Raphanus sativus). We created populations of varying size and relatedness. We measured maternal fitness in terms of both fruit set per flower and seed number per fruit. We found that both population size and the level of genetic relatedness among individuals influence maternal reproductive success. Our results explicitly define an ecological genetic obstacle faced by populations of an exotic species on its way to becoming invasive. Such a mechanistic understanding of the invasions of species that require a mate can and should be exploited for both controlling current outbreaks and reducing their frequency in the future. PMID:17197422

  10. Linking populations to landscapes: richness scenarios resulting from changes in the dynamics of an ecosystem engineer.

    PubMed

    Wright, Justin P

    2009-12-01

    Predicting the effects of the loss of individual species on diversity represents one of the primary challenges facing community ecology. One pathway by which organisms of one species affect the distribution of species is ecosystem engineering. Changes in the dynamics of ecosystem engineers that lead to changes in the distribution of the patches of altered habitat are likely to lead to changes in diversity. I link data on the distribution of plant species found in the riparian zone of the Adirondacks (New York, USA) in patches modified by beaver and in unmodified forest patches to a model connecting the dynamics of ecosystem engineers to the dynamics of the patches that they create. These analyses demonstrate that changes in key parameters of the model, such as decreases in beaver colonization rates and rate of patch abandonment, lead to changes in species richness of up to 45% at the landscape scale, and that these changes are likely to occur over long time scales. This general approach of linking the population dynamics or behavior of a single species to changes in species richness at the landscape scale provides a means for both testing the importance of ecosystem engineering in different systems and developing scenarios to predict how changes in the dynamics of a single species are likely to affect species richness. PMID:20120810

  11. Population dynamics of microbial communities in the zebrafish gut

    NASA Astrophysics Data System (ADS)

    Jemielita, Matthew; Taormina, Michael; Burns, Adam; Hampton, Jennifer; Rolig, Annah; Wiles, Travis; Guillemin, Karen; Parthasarathy, Raghuveer

    2015-03-01

    The vertebrate intestine is home to a diverse microbial community, which plays a crucial role in the development and health of its host. Little is known about the population dynamics and spatial structure of this ecosystem, including mechanisms of growth and interactions between species. We have constructed an experimental model system with which to explore these issues, using initially germ-free larval zebrafish inoculated with defined communities of fluorescently tagged bacteria. Using light sheet fluorescence microscopy combined with computational image analysis we observe and quantify the entire bacterial community of the intestine during the first 24 hours of colonization, during which time the bacterial population grows from tens to tens of thousands of bacteria. We identify both individual bacteria and clusters of bacteria, and quantify the growth rate and spatial distribution of these distinct subpopulations. We find that clusters of bacteria grow considerably faster than individuals and are located in specific regions of the intestine. Imaging colonization by two species reveals spatial segregation and competition. These data and their analysis highlight the importance of spatial organization in the establishment of gut microbial communities, and can provide inputs to physical models of real-world ecological dynamics.

  12. Does Leisure Time as a Stress Coping Resource Increase Affective Complexity? Applying the Dynamic Model of Affect (DMA).

    PubMed

    Qian, Xinyi Lisa; Yarnal, Careen M; Almeida, David M

    2013-01-01

    Affective complexity, a manifestation of psychological well-being, refers to the relative independence between positive and negative affect (PA, NA). According to the Dynamic Model of Affect (DMA), stressful situations lead to highly inverse PA-NA relationship, reducing affective complexity. Meanwhile, positive events can sustain affective complexity by restoring PA-NA independence. Leisure, a type of positive events, has been identified as a coping resource. This study used the DMA to assess whether leisure time helps restore affective complexity on stressful days. We found that on days with more leisure time than usual, an individual experienced less negative PA-NA relationship after daily stressful events. The finding demonstrates the value of leisure time as a coping resource and the DMA's contribution to coping research. PMID:24659826

  13. Inferring Network Dynamics and Neuron Properties from Population Recordings

    PubMed Central

    Linaro, Daniele; Storace, Marco; Mattia, Maurizio

    2011-01-01

    Understanding the computational capabilities of the nervous system means to “identify” its emergent multiscale dynamics. For this purpose, we propose a novel model-driven identification procedure and apply it to sparsely connected populations of excitatory integrate-and-fire neurons with spike frequency adaptation (SFA). Our method does not characterize the system from its microscopic elements in a bottom-up fashion, and does not resort to any linearization. We investigate networks as a whole, inferring their properties from the response dynamics of the instantaneous discharge rate to brief and aspecific supra-threshold stimulations. While several available methods assume generic expressions for the system as a black box, we adopt a mean-field theory for the evolution of the network transparently parameterized by identified elements (such as dynamic timescales), which are in turn non-trivially related to single-neuron properties. In particular, from the elicited transient responses, the input–output gain function of the neurons in the network is extracted and direct links to the microscopic level are made available: indeed, we show how to extract the decay time constant of the SFA, the absolute refractory period and the average synaptic efficacy. In addition and contrary to previous attempts, our method captures the system dynamics across bifurcations separating qualitatively different dynamical regimes. The robustness and the generality of the methodology is tested on controlled simulations, reporting a good agreement between theoretically expected and identified values. The assumptions behind the underlying theoretical framework make the method readily applicable to biological preparations like cultured neuron networks and in vitro brain slices. PMID:22016731

  14. [Gypsy moth Lymantria dispar L. in the South Urals: Patterns in population dynamics and modelling].

    PubMed

    Soukhovolsky, V G; Ponomarev, V I; Sokolov, G I; Tarasova, O V; Krasnoperova, P A

    2015-01-01

    The analysis is conducted on population dynamics of gypsy moth from different habitats of the South Urals. The pattern of cyclic changes in population density is examined, the assessment of temporal conjugation in time series of gypsy moth population dynamics from separate habitats of the South Urals is carried out, the relationships between population density and weather conditions are studied. Based on the results obtained, a statistical model of gypsy moth population dynamics in the South Urals is designed, and estimations are given of regulatory and modifying factors effects on the population dynamics. PMID:26201216

  15. Bipolar disorder dynamics: affective instabilities, relaxation oscillations and noise

    PubMed Central

    Geddes, John R.; Goodwin, Guy M.; Holmes, Emily A.

    2015-01-01

    Bipolar disorder is a chronic, recurrent mental illness characterized by extreme episodes of depressed and manic mood, interspersed with less severe but highly variable mood fluctuations. Here, we develop a novel mathematical approach for exploring the dynamics of bipolar disorder. We investigate how the dynamics of subjective experience of mood in bipolar disorder can be understood using a relaxation oscillator (RO) framework and test the model against mood time-series fluctuations from a set of individuals with bipolar disorder. We show that variable mood fluctuations in individuals diagnosed with bipolar disorder can be driven by the coupled effects of deterministic dynamics (captured by ROs) and noise. Using a statistical likelihood-based approach, we show that, in general, mood dynamics are described by two independent ROs with differing levels of endogenous variability among individuals. We suggest that this sort of nonlinear approach to bipolar disorder has neurobiological, cognitive and clinical implications for understanding this mental illness through a mechacognitive framework. PMID:26577592

  16. Sharp gene pool transition in a population affected by phenotype-based selective hunting

    NASA Astrophysics Data System (ADS)

    Brigatti, E.; Sá Martins, J. S.; Roditi, I.

    2005-06-01

    We use a microscopic model of population dynamics, a modified version of the well known Penna model, to study some aspects of microevolution. This research is motivated by recent reports on the effect of selective hunting on the gene pool of bighorn sheep living in the Ram Mountain region, in Canada. Our model finds a sharp transition in the structure of the gene pool as some threshold for the number of animals hunted is reached.

  17. Herbivory by an introduced Asian weevil negatively affects population growth of an invasive Brazilian shrub in Florida.

    PubMed

    Stricker, Kerry Bohl; Stiling, Peter

    2012-08-01

    The enemy release hypothesis (ERH) is often cited to explain why some plants successfully invade natural communities while others do not. This hypothesis maintains that plant populations are regulated by coevolved enemies in their native range but are relieved of this pressure where their enemies have not been co-introduced. Some studies have shown that invasive plants sustain lower levels of herbivore damage when compared to native species, but how damage affects fitness and population dynamics remains unclear. We used a system of co-occurring native and invasive Eugenia congeners in south Florida (USA) to experimentally test the ERH, addressing deficiencies in our understanding of the role of natural enemies in plant invasion at the population level. Insecticide was used to experimentally exclude insect herbivores from invasive Eugenia uniflora and its native co-occurring congeners in the field for two years. Herbivore damage, plant growth, survival, and population growth rates for the three species were then compared for control and insecticide-treated plants. Our results contradict the ERH, indicating that E. uniflora sustains more herbivore damage than its native congeners and that this damage negatively impacts stem height, survival, and population growth. In addition, most damage to E. uniflora, a native of Brazil, is carried out by Myllocerus undatus, a recently introduced weevil from Sri Lanka, and M. undatus attacks a significantly greater proportion of E. uniflora leaves than those of its native congeners. This interaction is particularly interesting because M. undatus and E. uniflora share no coevolutionary history, having arisen on two separate continents and come into contact on a third. Our study is the first to document negative population-level effects for an invasive plant as a result of the introduction of a novel herbivore. Such inhibitory interactions are likely to become more prevalent as suites of previously noninteracting species continue to

  18. Population structure and dynamics of Magnaporthe grisea in the Indian Himalayas.

    PubMed Central

    Kumar, J; Nelson, R J; Zeigler, R S

    1999-01-01

    The population genetics of Magnaporthe grisea, the rice blast pathogen, were analyzed in a center of rice diversity (the Uttar Pradesh hills of the Indian Himalayas) using multilocus and single-, or low-copy, DNA markers. Based on DNA fingerprinting with the multilocus probe MGR586 and single-locus probes, 157 haplotypes clustered into 56 lineages (at >/=70% MGR586 band similarity, each with unique single-locus profiles) and high diversity indices were detected among 458 isolates collected from 29 sites during 1992-1995. Most valleys sampled had distinct populations (73% of the lineages were site specific) with some containing one or a few lineages, confirming the importance of clonal propagation, and others were very diverse. Widely distributed lineages suggested that migration occurs across the region and into the Indo-Gangetic plains. Repeated sampling at one site, Matli, (170 isolates, 1992-1995) yielded 19 lineages and diversity significantly greater than that reported from similar samples from Colombia and the Philippines. Analysis of allelic associations using pairwise comparisons and multilocus variance analysis failed to reject the hypothesis of gametic phase equilibrium. The Matli population shifted from highly diverse in 1992 to almost complete dominance by one lineage in 1995. Such population dynamics are consistent with recombination followed by differential survival of clonal descendants of recombinant progeny. At another site, Ranichauri, population (n = 84) composition changed from 2 to 11 lineages over 2 yr and yielded additional evidence for equilibrium. Sexually fertile and hermaphrodite isolates of both mating types were recovered from rice in both Matli and Ranichauri. We demonstrate that Himalayan M. grisea populations are diverse and dynamic and conclude that the structure of some populations may be affected to some extent by sexual recombination. PMID:10388817

  19. Riding the tide of emotions with mindfulness: Mindfulness, affect dynamics, and the mediating role of coping.

    PubMed

    Keng, Shian-Ling; Tong, Eddie M W

    2016-08-01

    Little research has examined ways in which mindfulness is associated with affect dynamics, referring to patterns of affect fluctuations in daily life. Using ecological momentary assessment (EMA), the present study examined the associations between trait mindfulness and several types of affect dynamics, namely affect variability, affect inertia, affect switch, and affect instability. Three hundred ninety undergraduate students from Singapore reported their current emotions and coping styles up to 19 times per day across 2 days. Results showed that trait mindfulness correlated negatively with variability, instability, and inertia of negative affect and positively with negative-to-positive affect switch. These relationships were independent of openness, habitual reappraisal, habitual suppression, depression, and self-esteem. Importantly, lower maladaptive coping was found to mediate these relationships. The study suggests that trait mindfulness independently promotes adaptive patterns of affective experiences in daily life by inhibiting maladaptive coping styles. (PsycINFO Database Record PMID:27064290

  20. How vegetation patterning affects sediment dynamics in complex landscapes

    NASA Astrophysics Data System (ADS)

    Baartman, Jantiene; Temme, Arnaud; Saco, Patricia

    2016-04-01

    Semi-arid ecosystems are often spatially self-organized in typical patterns of vegetation bands with high plant cover interspersed with bare soil areas, also known as 'tigerbush'. Tigerbush dynamics have been studied using model simulations on flat synthetic landscapes, although in some cases straight slopes were used. The feedbacks between vegetation and more realistic and complex landscapes have not been studied yet, even though these landscapes are much more prevalent. Hence, our objective was to determine the effect of landform variation on vegetation patterning and sediment dynamics. We linked two existing models that simulate (a) plant growth, death and dispersal of vegetation, and (b) erosion and sedimentation. The model was calibrated on a straight planar hillslope and then applied to (i) a set of synthetic but more complex topographies and (ii) three real-world landscapes. Furthermore, sediment dynamics were evaluated by comparing simulated sediment output with and without vegetation dynamics. Results show banded vegetation patterning on all synthetic topographies, always perpendicular to the slope gradient. For real topographies, banded vegetation was simulated in the relatively flat, rolling landscape and in the dissected landscape when slopes were gentle. In the steep dissected landscape and the alluvial fan, vegetation was simulated to grow in local depressions where moisture is present whereas hilltops were bare. Including vegetation dynamics resulted in significantly less simulated erosion and relatively more deposition compared to simulations with uniformly distributed vegetation.

  1. Effective population size dynamics and the demographic collapse of Bornean orang-utans.

    PubMed

    Sharma, Reeta; Arora, Natasha; Goossens, Benoit; Nater, Alexander; Morf, Nadja; Salmona, Jordi; Bruford, Michael W; Van Schaik, Carel P; Krützen, Michael; Chikhi, Lounès

    2012-01-01

    Bornean orang-utans experienced a major demographic decline and local extirpations during the Pleistocene and Holocene due to climate change, the arrival of modern humans, of farmers and recent commercially-driven habitat loss and fragmentation. The recent loss of habitat and its dramatic fragmentation has affected the patterns of genetic variability and differentiation among the remaining populations and increased the extinction risk of the most isolated ones. However, the contribution of recent demographic events to such genetic patterns is still not fully clear. Indeed, it can be difficult to separate the effects of recent anthropogenic fragmentation from the genetic signature of prehistoric demographic events. Here, we investigated the genetic structure and population size dynamics of orang-utans from different sites. Altogether 126 individuals were analyzed and a full-likelihood Bayesian approach was applied. All sites exhibited clear signals of population decline. Population structure is known to generate spurious bottleneck signals and we found that it does indeed contribute to the signals observed. However, population structure alone does not easily explain the observed patterns. The dating of the population decline varied across sites but was always within the 200-2000 years period. This suggests that in some sites at least, orang-utan populations were affected by demographic events that started before the recent anthropogenic effects that occurred in Borneo. These results do not mean that the recent forest exploitation did not leave its genetic mark on orang-utans but suggests that the genetic pool of orang-utans is also impacted by more ancient events. While we cannot identify the main cause for this decline, our results suggests that the decline may be related to the arrival of the first farmers or climatic events, and that more theoretical work is needed to understand how multiple demographic events impact the genome of species and how we can assess

  2. Effective Population Size Dynamics and the Demographic Collapse of Bornean Orang-Utans

    PubMed Central

    Goossens, Benoit; Nater, Alexander; Morf, Nadja; Salmona, Jordi; Bruford, Michael W.; Van Schaik, Carel P.; Krützen, Michael; Chikhi, Lounès

    2012-01-01

    Bornean orang-utans experienced a major demographic decline and local extirpations during the Pleistocene and Holocene due to climate change, the arrival of modern humans, of farmers and recent commercially-driven habitat loss and fragmentation. The recent loss of habitat and its dramatic fragmentation has affected the patterns of genetic variability and differentiation among the remaining populations and increased the extinction risk of the most isolated ones. However, the contribution of recent demographic events to such genetic patterns is still not fully clear. Indeed, it can be difficult to separate the effects of recent anthropogenic fragmentation from the genetic signature of prehistoric demographic events. Here, we investigated the genetic structure and population size dynamics of orang-utans from different sites. Altogether 126 individuals were analyzed and a full-likelihood Bayesian approach was applied. All sites exhibited clear signals of population decline. Population structure is known to generate spurious bottleneck signals and we found that it does indeed contribute to the signals observed. However, population structure alone does not easily explain the observed patterns. The dating of the population decline varied across sites but was always within the 200–2000 years period. This suggests that in some sites at least, orang-utan populations were affected by demographic events that started before the recent anthropogenic effects that occurred in Borneo. These results do not mean that the recent forest exploitation did not leave its genetic mark on orang-utans but suggests that the genetic pool of orang-utans is also impacted by more ancient events. While we cannot identify the main cause for this decline, our results suggests that the decline may be related to the arrival of the first farmers or climatic events, and that more theoretical work is needed to understand how multiple demographic events impact the genome of species and how we can assess

  3. Language evolution and population dynamics in a system of two interacting species

    NASA Astrophysics Data System (ADS)

    Kosmidis, Kosmas; Halley, John M.; Argyrakis, Panos

    2005-08-01

    We use Monte Carlo simulations and assumptions from evolutionary game theory in order to study the evolution of words and the population dynamics of a system made of two interacting species which initially speak two different languages. The species are characterized by their identity, vocabulary, and have different initial fitness, i.e. reproduction capability. We investigate how different initial fitness affects the vocabulary of the species or the population dynamics by leading to a permanent populational advantage. We further find that the spatial distributions of the species may cause the system to exhibit pattern formation or segregation. We show that an initial fitness advantage, even though very quickly balanced, leads to better spatial arrangement and enhances survival probabilities of the species. In most cases the system will arrive at a final state where both languages coexist. However, in cases where one species greatly outnumbers the other in population and fitness, then only one species survives with its “final” language having a slightly richer vocabulary than its initial language. Thus, our results offer an explanation for the existence and origin of synonyms in spoken languages.

  4. Nonlinear Dynamics, Noise and Cooperative Behavior in Affective Disorders

    NASA Astrophysics Data System (ADS)

    Huber, Martin

    2001-03-01

    Mood disorders tend to be recurrent and progressive and illness patterns typically evolve from isolated episodes at the beginning to more rapid, rhythmic and finally irregular "chaotic" mood patterns. This chararacteristic timecourse prompted the consideration of nonlinear dynamics as a way to describe and analyze course and disease states of mood disorders. Indeed, some evidences now exist indicating that low-dimensional dynamics underly the illness progression. To gain an understanding of prinicple mechanisms that might underly the course and disease patterns of mood disorders, we developed a phenomenological mathematical model for the disease course. In doing so, we made use of a neuronal analogy that exists between disease patterns and neuronal spike patterns and which is commonly referred to as the kindling model of mood disorders (Post, Am J of Psychiatry 1992,149:999-1010; Huber, Braun, Krieg, Biol Psychiatry 1999,46:256-262; Huber, Braun, Krieg, Biol Psychiatry 2000,47:634-642). Using a computational implementation of this approach we investigated the possible relevance of nonlinear dynamics for the disease course, the role of cooperative interactions between nonlinear and noisy dynamics as well as the effect of sensitization mechanisms between disease episodes and disease system. Our simulations show that a low-dimensional model can phenomenologically map the timecourse of mood disorders. From a functional perspective, the model indicates an important role for stochastic fluctuations which can amplify subthreshold states into disease states and can induce transitions to irregular rapidly changing disease patterns. Interesting dynamics are observed with respect to deterministically defined disease states and their dependence on noise intensity. Finally, our simulations show how sensitization effects quite naturally lead to a disease course which ends in irregular fluctuating disease patterns as observed in clinical data. Our findings indicate the usefulness

  5. Population variation affects interactions between two California salt marsh plant species more than precipitation.

    PubMed

    Noto, Akana E; Shurin, Jonathan B

    2016-02-01

    Species that occur along broad environmental gradients often vary in phenotypic traits that make them better adapted to local conditions. Variation in species interactions across gradients could therefore be due to either phenotypic differences among populations or environmental conditions that shift the balance between competition and facilitation. To understand how the environment (precipitation) and variation among populations affect species interactions, we conducted a common garden experiment using two common salt marsh plant species, Salicornia pacifica and Jaumea carnosa, from six salt marshes along the California coast encompassing a large precipitation gradient. Plants were grown alone or with an individual of the opposite species from the same site and exposed to one of three precipitation regimes. J. carnosa was negatively affected in the presence of S. pacifica, while S. pacifica was facilitated by J. carnosa. The strength of these interactions varied by site of origin but not by precipitation treatment. These results suggest that phenotypic variation among populations can affect interaction strength more than environment, despite a threefold difference in precipitation. Geographic intraspecific variation may therefore play an important role in determining the strength of interactions in communities. PMID:26481794

  6. Famine-affected, refugee, and displaced populations: recommendations for public health issues.

    PubMed

    1992-07-24

    During the past three decades, the most common emergencies affecting the health of large populations in developing countries have involved famine and forced migrations. The public health consequences of mass population displacement have been extensively documented. On some occasions, these migrations have resulted in extremely high rates of mortality, morbidity, and malnutrition. The most severe consequences of population displacement have occurred during the acute emergency phase, when relief efforts are in the early stage. During this phase, deaths--in some cases--were 60 times the crude mortality rate (CMR) among non-refugee populations in the country of origin (1). Although the quality of international disaster response efforts has steadily improved, the human cost of forced migration remains high. Since the early 1960s, most emergencies involving refugees and displaced persons have taken place in less developed countries where local resources have been insufficient for providing prompt and adequate assistance. The international community's response to the health needs of these populations has been at times inappropriate, relying on teams of foreign medical personnel with little or no training. Hospitals, clinics, and feeding centers have been set up without assessment of preliminary needs, and essential prevention programs have been neglected. More recent relief programs, however, emphasize a primary health care (PHC) approach, focusing on preventive programs such as immunization and oral rehydration therapy (ORT), promoting involvement by the refugee community in the provision of health services, and stressing more effective coordination and information gathering. The PHC approach offers long-term advantages, not only for the directly affected population, but also for the country hosting the refugees. A PHC strategy is sustainable and strengthens the national health development program. PMID:1326713

  7. Uncoupling the Effects of Seed Predation and Seed Dispersal by Granivorous Ants on Plant Population Dynamics

    PubMed Central

    Arnan, Xavier; Molowny-Horas, Roberto; Rodrigo, Anselm; Retana, Javier

    2012-01-01

    Secondary seed dispersal is an important plant-animal interaction, which is central to understanding plant population and community dynamics. Very little information is still available on the effects of dispersal on plant demography and, particularly, for ant-seed dispersal interactions. As many other interactions, seed dispersal by animals involves costs (seed predation) and benefits (seed dispersal), the balance of which determines the outcome of the interaction. Separate quantification of each of them is essential in order to understand the effects of this interaction. To address this issue, we have successfully separated and analyzed the costs and benefits of seed dispersal by seed-harvesting ants on the plant population dynamics of three shrub species with different traits. To that aim a stochastic, spatially-explicit individually-based simulation model has been implemented based on actual data sets. The results from our simulation model agree with theoretical models of plant response dependent on seed dispersal, for one plant species, and ant-mediated seed predation, for another one. In these cases, model predictions were close to the observed values at field. Nonetheless, these ecological processes did not affect in anyway a third species, for which the model predictions were far from the observed values. This indicates that the balance between costs and benefits associated to secondary seed dispersal is clearly related to specific traits. This study is one of the first works that analyze tradeoffs of secondary seed dispersal on plant population dynamics, by disentangling the effects of related costs and benefits. We suggest analyzing the effects of interactions on population dynamics as opposed to merely analyzing the partners and their interaction strength. PMID:22880125

  8. Wave trains in a model of gypsy moth population dynamics

    NASA Astrophysics Data System (ADS)

    Wilder, J. W.; Vasquez, D. A.; Christie, I.; Colbert, J. J.

    1995-12-01

    A recent model of gypsy moth [Lymantria dispar (Lepidoptera: Lymantriidae)] populations led to the observation of traveling waves in a one-dimensional spatial model. In this work, these waves are studied in more detail and their nature investigated. It was observed that when there are no spatial effects the model behaves chaotically under certain conditions. Under the same conditions, when diffusion is allowed, traveling waves develop. The biomass densities involved in the model, when examined at one point in the spatial domain, are found to correspond to a limit cycle lying on the surface of the chaotic attractor of the spatially homogeneous model. Also observed are wave trains that have modulating maxima, and which when examined at one point in the spatial domain show a quasiperiodic temporal behavior. This complex behavior is determined to be due to the interaction of the traveling wave and the chaotic background dynamics.

  9. On signals of phase transitions in salmon population dynamics.

    PubMed

    Krkošek, Martin; Drake, John M

    2014-06-01

    Critical slowing down (CSD) reflects the decline in resilience of equilibria near a bifurcation and may reveal early warning signals (EWS) of ecological phase transitions. We studied CSD in the recruitment dynamics of 120 stocks of three Pacific salmon (Oncorhynchus spp.) species in relation to critical transitions in fishery models. Pink salmon (Oncorhynchus gorbuscha) exhibited increased variability and autocorrelation in populations that had a growth parameter, r, close to zero, consistent with EWS of extinction. However, models and data for sockeye salmon (Oncorhynchus nerka) indicate that portfolio effects from heterogeneity in age-at-maturity may obscure EWS. Chum salmon (Oncorhynchus keta) show intermediate results. The data do not reveal EWS of Ricker-type bifurcations that cause oscillations and chaos at high r. These results not only provide empirical support for CSD in some ecological systems, but also indicate that portfolio effects of age structure may conceal EWS of some critical transitions. PMID:24759855

  10. Richards-like two species population dynamics model.

    PubMed

    Ribeiro, Fabiano; Cabella, Brenno Caetano Troca; Martinez, Alexandre Souto

    2014-12-01

    The two-species population dynamics model is the simplest paradigm of inter- and intra-species interaction. Here, we present a generalized Lotka-Volterra model with intraspecific competition, which retrieves as particular cases, some well-known models. The generalization parameter is related to the species habitat dimensionality and their interaction range. Contrary to standard models, the species coupling parameters are general, not restricted to non-negative values. Therefore, they may represent different ecological regimes, which are derived from the asymptotic solution stability analysis and are represented in a phase diagram. In this diagram, we have identified a forbidden region in the mutualism regime, and a survival/extinction transition with dependence on initial conditions for the competition regime. Also, we shed light on two types of predation and competition: weak, if there are species coexistence, or strong, if at least one species is extinguished. PMID:25112794

  11. Urban aerosols harbor diverse and dynamic bacterial populations

    PubMed Central

    Brodie, Eoin L.; DeSantis, Todd Z.; Parker, Jordan P. Moberg; Zubietta, Ingrid X.; Piceno, Yvette M.; Andersen, Gary L.

    2007-01-01

    Considering the importance of its potential implications for human health, agricultural productivity, and ecosystem stability, surprisingly little is known regarding the composition or dynamics of the atmosphere's microbial inhabitants. Using a custom high-density DNA microarray, we detected and monitored bacterial populations in two U.S. cities over 17 weeks. These urban aerosols contained at least 1,800 diverse bacterial types, a richness approaching that of some soil bacterial communities. We also reveal the consistent presence of bacterial families with pathogenic members including environmental relatives of select agents of bioterrorism significance. Finally, using multivariate regression techniques, we demonstrate that temporal and meteorological influences can be stronger factors than location in shaping the biological composition of the air we breathe. PMID:17182744

  12. Neural Population Dynamics Modeled by Mean-Field Graphs

    NASA Astrophysics Data System (ADS)

    Kozma, Robert; Puljic, Marko

    2011-09-01

    In this work we apply random graph theory approach to describe neural population dynamics. There are important advantages of using random graph theory approach in addition to ordinary and partial differential equations. The mathematical theory of large-scale random graphs provides an efficient tool to describe transitions between high- and low-dimensional spaces. Recent advances in studying neural correlates of higher cognition indicate the significance of sudden changes in space-time neurodynamics, which can be efficiently described as phase transitions in the neuropil medium. Phase transitions are rigorously defined mathematically on random graph sequences and they can be naturally generalized to a class of percolation processes called neuropercolation. In this work we employ mean-field graphs with given vertex degree distribution and edge strength distribution. We demonstrate the emergence of collective oscillations in the style of brains.

  13. Dynamical criticality in the collective activity of a neural population

    NASA Astrophysics Data System (ADS)

    Mora, Thierry

    The past decade has seen a wealth of physiological data suggesting that neural networks may behave like critical branching processes. Concurrently, the collective activity of neurons has been studied using explicit mappings to classic statistical mechanics models such as disordered Ising models, allowing for the study of their thermodynamics, but these efforts have ignored the dynamical nature of neural activity. I will show how to reconcile these two approaches by learning effective statistical mechanics models of the full history of the collective activity of a neuron population directly from physiological data, treating time as an additional dimension. Applying this technique to multi-electrode recordings from retinal ganglion cells, and studying the thermodynamics of the inferred model, reveals a peak in specific heat reminiscent of a second-order phase transition.

  14. [Phlebotomines of Senegal (Diptera: Psychodidae): population and population dynamics of the Mont-Rolland region].

    PubMed

    Ba, Y; Trouillet, J; Thonnon, J; Fontenille, D

    1998-06-01

    Phlebotomine sandflies were captured on a monthly basis from May 1995 to April 1996 in the Mont-Rolland district in Western Senegal. The objectives were to study the population dynamics of sandflies and to make an inventory of the viruses they transmit. Among 10,315 specimens captured, belonging to 14 species, Sergentomyia dubia (35.9%), S. schwetzi (27.7%) and S. buxtoni (24.5%) were the most abundant. Species from the genus Sergentomyia accounted for 99.6% versus 0.4% for the genus Phlebotomus. The sandflies population was observed to peak in February. The most populated resting sites of the captured insects were in decreasing order tree-holes, termite-hills and burrows. S. dubia was the most abundant species captured in tree-holes. It was S. buxtoni in termite-hills, while S. schwetzi was found to dwell most often in burrows. No virus was isolated from 2,114 specimens tested. PMID:9754310

  15. The Challenges and Recommendations of Accessing to Affected Population for Humanitarian Assistance: A Narrative Review

    PubMed Central

    Moslehi, Shandiz; Fatemi, Farin; Mahboubi, Mohammad; Mozafarsaadati, Hossein; Karami, Shirzad

    2015-01-01

    Objective: Access to affected people pays an important role in United Nation Organization for Coordination and Humanitarian Affairs (OCHA). The aim of this article is to identify the main obstacles of humanitarian access and the humanitarian organization responses to these obstacles and finally suggest some recommendations and strategies. Methods: In this narrative study the researchers searched in different databases. This study focused on the data from five countries in the following areas: access challenges and constraints to affected population and response strategies selected for operations in the affected countries by humanitarian organizations. Results: Three main issues were studied: security threats, bureaucratic restrictions and indirect constraint, which each of them divided to three subcategories. Finally, nine related subcategories emerged from this analysis. Conclusion: Most of these constraints relate to political issues. Changes in policy structures, negotiations and advocacy can be recommended to solve most of the problems in access issues. PMID:25948440

  16. Beyond trauma-focused psychiatric epidemiology: bridging research and practice with war-affected populations.

    PubMed

    Miller, Kenneth E; Kulkarni, Madhur; Kushner, Hallie

    2006-10-01

    This article examines the centrality of trauma-focused psychiatric epidemiology (TFPE) in research with war-affected populations. The authors question the utility of the dominant focus on posttraumatic stress disorder and other disorders of Western psychiatry, and they identify a set of critical research foci related to mental health work with communities affected by political violence. Core assumptions of TFPE and its roots in logical positivism and the biomedical model of contemporary psychiatry are explored. The authors suggest that an alternative framework--social constructivism--can serve as a bridge between researchers and practitioners by helping to refocus research efforts in ways that are conceptually and methodologically more attuned to the needs of war-affected communities and those working to address their mental health needs. PMID:17209709

  17. Population Dynamics of Aphids on Cereals: Digging in the Time-Series Data to Reveal Population Regulation Caused by Temperature

    PubMed Central

    Brabec, Marek; Honěk, Alois; Pekár, Stano; Martinková, Zdenka

    2014-01-01

    Aphid populations show periodic fluctuations and many causes are attributed to their dynamic. We investigated the regulation by temperature of the aphid populations composed of Metopolophium dirhodum, Sitobion avenae, and Rhopalosiphum padi on winter wheat using a 24 years long time series data. We computed the sum of daily temperatures above 5°C, the threshold temperature for aphid development, and the sum of daily temperatures within the [0(threshold for wheat development),5] °C interval. Applying Generalised Additive Model framework we tested influences of temperature history expressed via degree days before the start of the aphid immigration on the length of their occurrence. We aimed to estimate the magnitude and direction of this influence, and how far to the past before the start of the aphid season the temperature effect goes and then identify processes responsible for the effect. We fitted four models that differed in the way of correcting for abundance in the previous year and in specification of temperature effects. Abundance in the previous year did not affect the length of period of aphid population growth on wheat. The temperature effect on the period length increased up to 123 days before the start of the current season, i.e. when wheat completed vernalization. Increased sum of daily temperatures above 5°C and the sum of daily temperatures within the [0,5] °C interval both shortened the length of period of aphid population growth. Stronger effect of the latter suggests that wheat can escape from aphid attacks if during winter temperatures range from 0 to 5°C. The temperature influence was not homogeneous in time. The strongest effect of past temperature was about 50 to 80 and 90 to 110 days before the beginning of the current aphid season indicating important role of termination of aphid egg dormancy and egg hatching. PMID:25184219

  18. Far from random: dynamical groupings among the NEO population

    NASA Astrophysics Data System (ADS)

    de la Fuente Marcos, C.; de la Fuente Marcos, R.

    2016-03-01

    Among the near-Earth object (NEO) population, there are comets and active asteroids which are sources of fragments that initially move together; in addition, some NEOs follow orbits temporarily trapped in a web of secular resonances. These facts contribute to increasing the risk of meteoroid strikes on Earth, making its proper quantification difficult. The identification and subsequent study of groups of small NEOs that appear to move in similar trajectories are necessary steps in improving our understanding of the impact risk associated with meteoroids. Here, we present results of a search for statistically significant dynamical groupings among the NEO population. Our Monte Carlo-based methodology recovers well-documented groupings like the Taurid Complex or the one resulting from the split comet 73P/Schwassmann-Wachmann 3, and new ones that may have been the source of past impacts. Among the most conspicuous are the Mjolnir and Ptah groups, perhaps the source of recent impact events like Almahata Sitta and Chelyabinsk, respectively. Meteoroid 2014 AA, that hit the Earth on 2014 January 2, could have its origin in a marginally significant grouping associated with Bennu. We find that most of the substructure present within the orbital domain of the NEOs is of resonant nature, probably induced by secular resonances and the Kozai mechanism that confine these objects into specific paths with well-defined perihelia.

  19. Population dynamics in a metastable neon magneto-optical trap

    NASA Astrophysics Data System (ADS)

    Glover, R. D.; Calvert, J. E.; Sang, R. T.

    2013-02-01

    We observe the population dynamics within a metastable neon magneto-optical trap (MOT) through the measurement of the average squared Clebsch-Gordan coefficient C2 over a range of laser detunings. The magnitude of C2 is dependent on the internal quantum state of an atom interacting with the light field and is found to show a strong dependence on the applied laser detuning. Previously it has been reported [Townsend , Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.52.1423 52, 1423 (1995)] that trapped atoms in a MOT are pumped towards the states that interact most strongly with the local field and therefore the measured value of C2 is larger than the average over all possible transitions. For the 3P2-to-3D3 cooling transition in metastable neon the average C2 value is equal to 0.46; however, we have measured 0.29±0.03populations are measured via fluorescence in a MOT.

  20. Replication, Communication, and the Population Dynamics of Scientific Discovery

    PubMed Central

    McElreath, Richard; Smaldino, Paul E.

    2015-01-01

    Many published research results are false (Ioannidis, 2005), and controversy continues over the roles of replication and publication policy in improving the reliability of research. Addressing these problems is frustrated by the lack of a formal framework that jointly represents hypothesis formation, replication, publication bias, and variation in research quality. We develop a mathematical model of scientific discovery that combines all of these elements. This model provides both a dynamic model of research as well as a formal framework for reasoning about the normative structure of science. We show that replication may serve as a ratchet that gradually separates true hypotheses from false, but the same factors that make initial findings unreliable also make replications unreliable. The most important factors in improving the reliability of research are the rate of false positives and the base rate of true hypotheses, and we offer suggestions for addressing each. Our results also bring clarity to verbal debates about the communication of research. Surprisingly, publication bias is not always an obstacle, but instead may have positive impacts—suppression of negative novel findings is often beneficial. We also find that communication of negative replications may aid true discovery even when attempts to replicate have diminished power. The model speaks constructively to ongoing debates about the design and conduct of science, focusing analysis and discussion on precise, internally consistent models, as well as highlighting the importance of population dynamics. PMID:26308448

  1. Modelling Multi-Pulse Population Dynamics from Ultrafast Spectroscopy

    PubMed Central

    van Wilderen, Luuk J. G. W.; Lincoln, Craig N.; van Thor, Jasper J.

    2011-01-01

    Current advanced laser, optics and electronics technology allows sensitive recording of molecular dynamics, from single resonance to multi-colour and multi-pulse experiments. Extracting the occurring (bio-) physical relevant pathways via global analysis of experimental data requires a systematic investigation of connectivity schemes. Here we present a Matlab-based toolbox for this purpose. The toolbox has a graphical user interface which facilitates the application of different reaction models to the data to generate the coupled differential equations. Any time-dependent dataset can be analysed to extract time-independent correlations of the observables by using gradient or direct search methods. Specific capabilities (i.e. chirp and instrument response function) for the analysis of ultrafast pump-probe spectroscopic data are included. The inclusion of an extra pulse that interacts with a transient phase can help to disentangle complex interdependent pathways. The modelling of pathways is therefore extended by new theory (which is included in the toolbox) that describes the finite bleach (orientation) effect of single and multiple intense polarised femtosecond pulses on an ensemble of randomly oriented particles in the presence of population decay. For instance, the generally assumed flat-top multimode beam profile is adapted to a more realistic Gaussian shape, exposing the need for several corrections for accurate anisotropy measurements. In addition, the (selective) excitation (photoselection) and anisotropy of populations that interact with single or multiple intense polarised laser pulses is demonstrated as function of power density and beam profile. Using example values of real world experiments it is calculated to what extent this effectively orients the ensemble of particles. Finally, the implementation includes the interaction with multiple pulses in addition to depth averaging in optically dense samples. In summary, we show that mathematical modelling is

  2. Population sex-ratio affecting behavior and physiology of overwintering bank voles (Myodes glareolus).

    PubMed

    Sipari, Saana; Haapakoski, Marko; Klemme, Ines; Palme, Rupert; Sundell, Janne; Ylönen, Hannu

    2016-05-15

    Many boreal rodents are territorial during the breeding season but during winter become social and aggregate for more energy efficient thermoregulation. Communal winter nesting and social interactions are considered to play an important role for the winter survival of these species, yet the topic is relatively little explored. Females are suggested to be the initiators of winter aggregations and sometimes reported to survive better than males. This could be due to the higher social tolerance observed in overwintering females than males. Hormonal status could also affect winter behavior and survival. For instance, chronic stress can have a negative effect on survival, whereas high gonadal hormone levels, such as testosterone, often induce aggressive behavior. To test if the winter survival of females in a boreal rodent is better than that of males, and to assess the role of females in the winter aggregations, we generated bank vole (Myodes glareolus) populations of three different sex ratios (male-biased, female-biased and even density) under semi-natural conditions. We monitored survival, spatial behavior and hormonal status (stress and testosterone) during two winter months. We observed no significant differences in survival between the sexes or among populations with differing sex-ratios. The degree of movement area overlap was used as an indicator of social tolerance and potential communal nesting. Individuals in male biased populations showed a tendency to be solitary, whereas in female biased populations there was an indication of winter aggregation. Females living in male-biased populations had higher stress levels than the females from the other populations. The female-biased sex-ratio induced winter breeding and elevated testosterone levels in males. Thus, our results suggest that the sex-ratio of the overwintering population can lead to divergent overwintering strategies in bank voles. PMID:26976741

  3. Population dynamics of Hawaiian seabird colonies vulnerable to sea-level rise.

    PubMed

    Hatfield, Jeff S; Reynolds, Michelle H; Seavy, Nathaniel E; Krause, Crystal M

    2012-08-01

    Globally, seabirds are vulnerable to anthropogenic threats both at sea and on land. Seabirds typically nest colonially and show strong fidelity to natal colonies, and such colonies on low-lying islands may be threatened by sea-level rise. We used French Frigate Shoals, the largest atoll in the Hawaiian Archipelago, as a case study to explore the population dynamics of seabird colonies and the potential effects sea-level rise may have on these rookeries. We compiled historic observations, a 30-year time series of seabird population abundance, lidar-derived elevations, and aerial imagery of all the islands of French Frigate Shoals. To estimate the population dynamics of 8 species of breeding seabirds on Tern Island from 1980 to 2009, we used a Gompertz model with a Bayesian approach to infer population growth rates, density dependence, process variation, and observation error. All species increased in abundance, in a pattern that provided evidence of density dependence. Great Frigatebirds (Fregata minor), Masked Boobies (Sula dactylatra), Red-tailed Tropicbirds (Phaethon rubricauda), Spectacled Terns (Onychoprion lunatus), and White Terns (Gygis alba) are likely at carrying capacity. Density dependence may exacerbate the effects of sea-level rise on seabirds because populations near carrying capacity on an island will be more negatively affected than populations with room for growth. We projected 12% of French Frigate Shoals will be inundated if sea level rises 1 m and 28% if sea level rises 2 m. Spectacled Terns and shrub-nesting species are especially vulnerable to sea-level rise, but seawalls and habitat restoration may mitigate the effects of sea-level rise. Losses of seabird nesting habitat may be substantial in the Hawaiian Islands by 2100 if sea levels rise 2 m. Restoration of higher-elevation seabird colonies represent a more enduring conservation solution for Pacific seabirds. PMID:22624702

  4. Population dynamics of Hawaiian seabird colonies vulnerable to sea-level rise

    USGS Publications Warehouse

    Hatfield, Jeff S.; Reynolds, Michelle H.; Seavy, Nathaniel E.; Krause, Crystal M.

    2012-01-01

    Globally, seabirds are vulnerable to anthropogenic threats both at sea and on land. Seabirds typically nest colonially and show strong fidelity to natal colonies, and such colonies on low-lying islands may be threatened by sea-level rise. We used French Frigate Shoals, the largest atoll in the Hawaiian Archipelago, as a case study to explore the population dynamics of seabird colonies and the potential effects sea-level rise may have on these rookeries. We compiled historic observations, a 30-year time series of seabird population abundance, lidar-derived elevations, and aerial imagery of all the islands of French Frigate Shoals. To estimate the population dynamics of 8 species of breeding seabirds on Tern Island from 1980 to 2009, we used a Gompertz model with a Bayesian approach to infer population growth rates, density dependence, process variation, and observation error. All species increased in abundance, in a pattern that provided evidence of density dependence. Great Frigatebirds (Fregata minor), Masked Boobies (Sula dactylatra), Red-tailed Tropicbirds (Phaethon rubricauda), Spectacled Terns (Onychoprion lunatus), and White Terns (Gygis alba) are likely at carrying capacity. Density dependence may exacerbate the effects of sea-level rise on seabirds because populations near carrying capacity on an island will be more negatively affected than populations with room for growth. We projected 12% of French Frigate Shoals will be inundated if sea level rises 1 m and 28% if sea level rises 2 m. Spectacled Terns and shrub-nesting species are especially vulnerable to sea-level rise, but seawalls and habitat restoration may mitigate the effects of sea-level rise. Losses of seabird nesting habitat may be substantial in the Hawaiian Islands by 2100 if sea levels rise 2 m. Restoration of higher-elevation seabird colonies represent a more enduring conservation solution for Pacific seabirds.

  5. Dynamical effects during compaction band formation affecting their spatial periodicity

    NASA Astrophysics Data System (ADS)

    Cecinato, Francesco; Gajo, Alessandro

    2014-10-01

    Compaction bands (CBs) are responsible for significant anisotropy alterations of permeability in geological materials; hence, understanding their formation conditions appears of key importance to all applications involving fluid extraction/injection from/into the ground. While most of the available models to understand CB formation are focused on interpreting the onset of a single CB, little effort has been so far dedicated to understand the documented periodicity of CBs. In this paper, the role of dynamical effects in inducing the post onset evolution of CBs is analyzed by means of a dedicated model for porous media with compressible constituents, with reference to a horizontal layer of sandy, water-saturated material. Elastic waves are generated as a first CB occurs due to sudden, localized volumetric collapse. If the waves are reflected at the interface with a softer material or with a previously formed CB, they produce significant local effective stress concentrations, which can promote the formation of further CBs in a cascade fashion, according to a regular geometric pattern. The spatial distribution of dynamically generated CBs, as well as the extent of the phenomenon, depends on the geometry of the domain and on the material's permeability. Sensitivity analysis is also performed to assess the key properties that promote dynamical CB in situ formation, identifying as the most influential conditions large stratum stiffness (increasing with depth) and the presence of softer layers. In contrast, the presence of less permeable and/or stiffer layers is not believed to play a major role in the proposed mechanism.

  6. Dynamical evolution and spatial mixing of multiple population globular clusters

    NASA Astrophysics Data System (ADS)

    Vesperini, Enrico; McMillan, Stephen L. W.; D'Antona, Francesca; D'Ercole, Annibale

    2013-03-01

    Numerous spectroscopic and photometric observational studies have provided strong evidence for the widespread presence of multiple stellar populations in globular clusters. In this paper, we study the long-term dynamical evolution of multiple population clusters, focusing on the evolution of the spatial distributions of the first- (FG) and second-generation (SG) stars. In previous studies, we have suggested that SG stars formed from the ejecta of FG AGB stars are expected initially to be concentrated in the cluster inner regions. Here, by means of N-body simulations, we explore the time-scales and the dynamics of the spatial mixing of the FG and the SG populations and their dependence on the SG initial concentration. Our simulations show that, as the evolution proceeds, the radial profile of the SG/FG number ratio, NSG/NFG, is characterized by three regions: (1) a flat inner part; (2) a declining part in which FG stars are increasingly dominant and (3) an outer region where the NSG/NFG profile flattens again (the NSG/NFG profile may rise slightly again in the outermost cluster regions). Until mixing is complete and the NSG/NFG profile is flat over the entire cluster, the radial variation of NSG/NFG implies that the fraction of SG stars determined by observations covering a limited range of radial distances is not, in general, equal to the SG global fraction, (NSG/NFG)glob. The distance at which NSG/NFG equals (NSG/NFG)glob is approximately between 1 and 2 cluster half-mass radii. The time-scale for complete mixing depends on the SG initial concentration, but in all cases complete mixing is expected only for clusters in advanced evolutionary phases, having lost at least 60-70 per cent of their mass due to two-body relaxation (in addition to the early FG loss due to the cluster expansion triggered by SNII ejecta and gas expulsion).The results of our simulations suggest that in many Galactic globular clusters the SG should still be more spatially concentrated than the

  7. Affective Dynamics of Leadership: An Experimental Test of Affect Control Theory

    ERIC Educational Resources Information Center

    Schroder, Tobias; Scholl, Wolfgang

    2009-01-01

    Affect Control Theory (ACT; Heise 1979, 2007) states that people control social interactions by striving to maintain culturally shared feelings about the situation. The theory is based on mathematical models of language-based impression formation. In a laboratory experiment, we tested the predictive power of a new German-language ACT model with…

  8. Statistical characteristics of dynamics for population migration driven by the economic interests

    NASA Astrophysics Data System (ADS)

    Huo, Jie; Wang, Xu-Ming; Zhao, Ning; Hao, Rui

    2016-06-01

    Population migration typically occurs under some constraints, which can deeply affect the structure of a society and some other related aspects. Therefore, it is critical to investigate the characteristics of population migration. Data from the China Statistical Yearbook indicate that the regional gross domestic product per capita relates to the population size via a linear or power-law relation. In addition, the distribution of population migration sizes or relative migration strength introduced here is dominated by a shifted power-law relation. To reveal the mechanism that creates the aforementioned distributions, a dynamic model is proposed based on the population migration rule that migration is facilitated by higher financial gains and abated by fewer employment opportunities at the destination, considering the migration cost as a function of the migration distance. The calculated results indicate that the distribution of the relative migration strength is governed by a shifted power-law relation, and that the distribution of migration distances is dominated by a truncated power-law relation. These results suggest the use of a power-law to fit a distribution may be not always suitable. Additionally, from the modeling framework, one can infer that it is the randomness and determinacy that jointly create the scaling characteristics of the distributions. The calculation also demonstrates that the network formed by active nodes, representing the immigration and emigration regions, usually evolves from an ordered state with a non-uniform structure to a disordered state with a uniform structure, which is evidenced by the increasing structural entropy.

  9. Evolution of virulence driven by predator-prey interaction: Possible consequences for population dynamics.

    PubMed

    Morozov, A Yu; Adamson, M W

    2011-05-01

    The evolution of pathogen virulence in natural populations has conventionally been considered as a result of selection caused by the interactions of the host with its pathogen(s). The host population, however, is generally embedded in complex trophic interactions with other populations in the community, in particular, intensive predation on the infected host can increase its mortality, and this can affect the course of virulence evolution. Reciprocally, in the long run, the evolution of virulence within an infected host can affect the patterns of population dynamics of a predator consuming the host (e.g. resulting in large amplitude oscillations, causing a severe drop in the population size, etc.). Surprisingly, neither the effect of predation on the evolution of virulence within a host, nor the influence of the evolution of virulence upon the consumer's dynamics has been addressed in the literature yet. In this paper, we consider a classical S-I ecoepidemiological model in which the infected host is consumed by a predator. We are particularly interested in the evolutionarily stable virulence of the pathogen in the model and its dependence upon ecologically relevant parameters. We show that predation can prominently shift the evolutionarily stable virulence towards more severe strains as compared to the same system without predation. We demonstrate that the evolution of virulence can result in a succession of dynamical regimes and can even lead to the extinction of the predator in the long run. The presence of a predator can indirectly affect the evolution within its prey since the evolutionarily stable virulence becomes a function of the prey growth rate, which would not be the case in a predator-free system. We find that the evolutionarily stable virulence largely depends on the carrying capacity K of the prey in a non-monotonous way. The model also predicts that in an eutrophic environment the shift of virulence towards evolutionarily stable benign strains can

  10. [Factors affecting access to health care institutions by the internally displaced population in Colombia].

    PubMed

    Mogollón-Pérez, Amparo Susana; Vázquez, María Luisa

    2008-04-01

    In Colombia, the on-going armed conflict causes displacement of thousands of persons that suffer its economic, social, and health consequences. Despite government regulatory efforts, displaced people still experience serious problems in securing access to health care. In order to analyze the institutional factors that affect access to health care by the internally displaced population, a qualitative, exploratory, and descriptive study was carried out by means of semi-structured individual interviews with a criterion sample of stakeholders (81). A narrative content analysis was performed, with mixed generation of categories and segmentation of data by themes and informants. Inadequate funding, providers' problems with reimbursement by insurers, and lack of clear definition as to coverage under the Social Security System in Health pose barriers to access to health care by the internally displaced population. Bureaucratic procedures, limited inter- and intra-sector coordination, and scarce available resources for public health service providers also affect access. Effective government action is required to ensure the right to health care for this population. PMID:18392351

  11. Haemoglobin polymorphisms affect the oxygen-binding properties in Atlantic cod populations

    PubMed Central

    Andersen, Øivind; Wetten, Ola Frang; De Rosa, Maria Cristina; Andre, Carl; Carelli Alinovi, Cristiana; Colafranceschi, Mauro; Brix, Ole; Colosimo, Alfredo

    2008-01-01

    A major challenge in evolutionary biology is to identify the genes underlying adaptation. The oxygen-transporting haemoglobins directly link external conditions with metabolic needs and therefore represent a unique system for studying environmental effects on molecular evolution. We have discovered two haemoglobin polymorphisms in Atlantic cod populations inhabiting varying temperature and oxygen regimes in the North Atlantic. Three-dimensional modelling of the tetrameric haemoglobin structure demonstrated that the two amino acid replacements Met55β1Val and Lys62β1Ala are located at crucial positions of the α1β1 subunit interface and haem pocket, respectively. The replacements are proposed to affect the oxygen-binding properties by modifying the haemoglobin quaternary structure and electrostatic feature. Intriguingly, the same molecular mechanism for facilitating oxygen binding is found in avian species adapted to high altitudes, illustrating convergent evolution in water- and air-breathing vertebrates to reduction in environmental oxygen availability. Cod populations inhabiting the cold Arctic waters and the low-oxygen Baltic Sea seem well adapted to these conditions by possessing the high oxygen affinity Val55–Ala62 haplotype, while the temperature-insensitive Met55–Lys62 haplotype predominates in the southern populations. The distinct distributions of the functionally different haemoglobin variants indicate that the present biogeography of this ecologically and economically important species might be seriously affected by global warming. PMID:19033139

  12. Dynamics of Populations of Planetary Systems (IAU C197)

    NASA Astrophysics Data System (ADS)

    Knezevic, Zoran; Milani, Andrea

    2005-05-01

    population of asteroids in the 2:1 mean motion resonance with Jupiter revised Miroslav Broz, D. Vokrouhlicky, F. Roig, D. Nesvorny, W. F. Bottke and A. Morbidelli; 22. On the reliability of computation of maximum Lyapunov Characteristic Exponents for asteroids Zoran Knezevic and Slobodan Ninkovic; 23. Nekhoroshev stability estimates for different models of the Trojan asteroids Christos Efthymiopoulos; 24. The role of the resonant 'stickiness' in the dynamical evolution of Jupiter family comets A. Alvarez-Canda and F. Roig; 25. Regimes of stability and scaling relations for the removal time in the asteroid belt: a simple kinetic model and numerical tests Mihailo Cubrovic; 26. Virtual asteroids and virtual impactors Andrea Milani; 27. Asteroid population models Alessandro Morbidelli; 28. Linking Very Large Telescope asteroid observations M. Granvik, K. Muinonen, J. Virtanen, M. Delbó, L. Saba, G. De Sanctis, R. Morbidelli, A. Cellino and E. Tedesco; 29. Collision orbits and phase transition for 2004 AS1 at discovery Jenni Virtanen, K. Muinonen, M. Granvik and T. Laakso; 30. The size of collision solutions in orbital elements space G. B. Valsecchi, A. Rossi, A. Milani and S. R. Chesley; 31. Very short arc orbit determination: the case of asteroid 2004 FU162 Steven R. Chesley; 32. Nonlinear impact monitoring: 2-dimensional sampling Giacomo Tommei; 33. Searching for gravity assisted trajectories to accessible near-Earth asteroids Stefan Berinde; 34. KLENOT - Near Earth and other unusual objects observations Michal Kocer, Jana Tichá and M. Tichy; 35. Transport of comets to the Inner Solar System Hans Rickman; 36. Nongravitational Accelerations on Comets Steven R. Chesley and Donald K. Yeomans; 37. Interaction of planetesimals with the giant planets and the shaping of the trans-Neptunian belt Harold F. Levison and Alessandro Morbidelli; 38. Transport of comets to the outer p

  13. Wolbachia infections in natural Anopheles populations affect egg laying and negatively correlate with Plasmodium development.

    PubMed

    Shaw, W Robert; Marcenac, Perrine; Childs, Lauren M; Buckee, Caroline O; Baldini, Francesco; Sawadogo, Simon P; Dabiré, Roch K; Diabaté, Abdoulaye; Catteruccia, Flaminia

    2016-01-01

    The maternally inherited alpha-proteobacterium Wolbachia has been proposed as a tool to block transmission of devastating mosquito-borne infectious diseases like dengue and malaria. Here we study the reproductive manipulations induced by a recently identified Wolbachia strain that stably infects natural mosquito populations of a major malaria vector, Anopheles coluzzii, in Burkina Faso. We determine that these infections significantly accelerate egg laying but do not induce cytoplasmic incompatibility or sex-ratio distortion, two parasitic reproductive phenotypes that facilitate the spread of other Wolbachia strains within insect hosts. Analysis of 221 blood-fed A. coluzzii females collected from houses shows a negative correlation between the presence of Plasmodium parasites and Wolbachia infection. A mathematical model incorporating these results predicts that infection with these endosymbionts may reduce malaria prevalence in human populations. These data suggest that Wolbachia may be an important player in malaria transmission dynamics in Sub-Saharan Africa. PMID:27243367

  14. Wolbachia infections in natural Anopheles populations affect egg laying and negatively correlate with Plasmodium development

    PubMed Central

    Shaw, W. Robert; Marcenac, Perrine; Childs, Lauren M.; Buckee, Caroline O.; Baldini, Francesco; Sawadogo, Simon P.; Dabiré, Roch K.; Diabaté, Abdoulaye; Catteruccia, Flaminia

    2016-01-01

    The maternally inherited alpha-proteobacterium Wolbachia has been proposed as a tool to block transmission of devastating mosquito-borne infectious diseases like dengue and malaria. Here we study the reproductive manipulations induced by a recently identified Wolbachia strain that stably infects natural mosquito populations of a major malaria vector, Anopheles coluzzii, in Burkina Faso. We determine that these infections significantly accelerate egg laying but do not induce cytoplasmic incompatibility or sex-ratio distortion, two parasitic reproductive phenotypes that facilitate the spread of other Wolbachia strains within insect hosts. Analysis of 221 blood-fed A. coluzzii females collected from houses shows a negative correlation between the presence of Plasmodium parasites and Wolbachia infection. A mathematical model incorporating these results predicts that infection with these endosymbionts may reduce malaria prevalence in human populations. These data suggest that Wolbachia may be an important player in malaria transmission dynamics in Sub-Saharan Africa. PMID:27243367

  15. Migration strategy affects avian influenza dynamics in mallards (Anas platyrhynchos).

    PubMed

    Hill, Nichola J; Takekawa, John Y; Ackerman, Joshua T; Hobson, Keith A; Herring, Garth; Cardona, Carol J; Runstadler, Jonathan A; Boyce, Walter M

    2012-12-01

    Studies of pathogen transmission typically overlook that wildlife hosts can include both migrant and resident populations when attempting to model circulation. Through the application of stable isotopes in flight feathers, we estimated the migration strategy of mallards (Anas platyrhynchos) occurring on California wintering grounds. Our study demonstrates that mallards- a principal host of avian influenza virus (AIV) in nature, contribute differently to virus gene flow depending on migration strategy. No difference in AIV prevalence was detected between resident (9.6%), intermediate-distance (9.6%) and long-distance migrants (7.4%). Viral diversity among the three groups was also comparable, possibly owing to viral pool mixing when birds converge at wetlands during winter. However, migrants and residents contributed differently to the virus gene pool at wintering wetlands. Migrants introduced virus from northern breeding grounds (Alaska and the NW Pacific Rim) into the wintering population, facilitating gene flow at continental scales, but circulation of imported virus appeared to be limited. In contrast, resident mallards acted as AIV reservoirs facilitating year-round circulation of limited subtypes (i.e. H5N2) at lower latitudes. This study supports a model of virus exchange in temperate regions driven by the convergence of wild birds with separate geographic origins and exposure histories. PMID:22971007

  16. Migration strategy affects avian influenza dynamics in mallards (Anas platyrhynchos).

    USGS Publications Warehouse

    Takekawa, John Y.; Hill, Nichola J.; Ackerman, Joshua T.; Herring, Garth; Hobson, Keith; Cardona, Carol J.; Runstadler, Jonathan; Boyce, Walter M.

    2012-01-01

    Studies of pathogen transmission typically overlook that wildlife hosts can include both migrant and resident populations when attempting to model circulation. Through the application of stable isotopes in flight feathers, we estimated the migration strategy of mallards (Anas platyrhynchos) occurring on California wintering grounds. Our study demonstrates that mallards- a principal host of avian influenza virus (AIV) in nature, contribute differently to virus gene flow depending on migration strategy. No difference in AIV prevalence was detected between resident (9.6%), intermediate-distance (9.6%) and long-distance migrants (7.4%). Viral diversity among the three groups was also comparable, possibly owing to viral pool mixing when birds converge at wetlands during winter. However, migrants and residents contributed differently to the virus gene pool at wintering wetlands. Migrants introduced virus from northern breeding grounds (Alaska and the NW Pacific Rim) into the wintering population, facilitating gene flow at continental scales, but circulation of imported virus appeared to be limited. In contrast, resident mallards acted as AIV reservoirs facilitating year-round circulation of limited subtypes (i.e. H5N2) at lower latitudes. This study supports a model of virus exchange in temperate regions driven by the convergence of wild birds with separate geographic origins and exposure histories.

  17. Why are some animal populations unaffected or positively affected by roads?

    PubMed

    Rytwinski, Trina; Fahrig, Lenore

    2013-11-01

    In reviews on effects of roads on animal population abundance we found that most effects are negative; however, there are also many neutral and positive responses [Fahrig and Rytwinski (Ecol Soc 14:21, 2009; Rytwinski and Fahrig (Biol Conserv 147:87-98, 2012)]. Here we use an individual-based simulation model to: (1) confirm predictions from the existing literature of the combinations of species traits and behavioural responses to roads that lead to negative effects of roads on animal population abundance, and (2) improve prediction of the combinations of species traits and behavioural responses to roads that lead to neutral and positive effects of roads on animal population abundance. Simulations represented a typical situation in which road mitigation is contemplated, i.e. rural landscapes containing a relatively low density (up to 1.86 km/km(2)) of high-traffic roads, with continuous habitat between the roads. In these landscapes, the simulations predict that populations of species with small territories and movement ranges, and high reproductive rates, i.e. many small mammals and birds, should not be reduced by roads. Contrary to previous suggestions, the results also predict that populations of species that obtain a resource from roads (e.g. vultures) do not increase with increasing road density. In addition, our simulations support the predation release hypothesis for positive road effects on prey (both small- and large-bodied prey), whereby abundance of a prey species increased with increasing road density due to reduced predation by generalist road-affected predators. The simulations also predict an optimal road density for the large-bodied prey species if it avoids roads or traffic emissions. Overall, the simulation results suggest that in rural landscapes containing high-traffic roads, there are many species for which road mitigation may not be necessary; mitigation efforts should be tailored to the species that show negative population responses to roads

  18. Effects of tick population dynamics and host densities on the persistence of tick-borne infections.

    PubMed

    Rosà, Roberto; Pugliese, Andrea

    2007-07-01

    The transmission and the persistence of tick-borne infections are strongly influenced by the densities and the structure of host populations. By extending previous models and analysis, in this paper we analyse how the persistence of ticks and pathogens, is affected by the dynamics of tick populations, and by their host densities. The effect of host densities on infection persistence is explored through the analysis and simulation of a series of models that include different assumptions on tick-host dynamics and consider different routes of infection transmission. Ticks are assumed to feed on two types of host species which vary in their reservoir competence. Too low densities of competent hosts (i.e., hosts where transmission can occur) do not sustain the infection cycle, while too high densities of incompetent hosts may dilute the competent hosts so much to make infection persistence impossible. A dilution effect may occur also for competent hosts as a consequence of reduced tick to host ratio; this is possible only if the regulation of tick populations is such that tick density does not increase linearly with host densities. PMID:17125804

  19. A hybrid model of molecular regulation and population dynamics for yeast autophagy.

    PubMed

    Jin, Huiqin; Lei, Jinzhi

    2016-08-01

    Autophagy is an evolutionarily conserved lysosome-based degradation process that is involved in maintaining cellular homeostasis and stress responses. Dysregulation of autophagy is known to associate with many diseases. In this paper, we establish a Hybrid model of Molecular regulation and Population dynamics (HMP model) for yeast autophagy to study how autophagy regulation at molecular level affects the cell population dynamics under the stress of starvation. The model includes interactions between amino acids, TORC1, Atg1 complex, and Atg8 lipidation at the molecular level, and cell death and division at the cell behavior level. Two feedback loops are involved in autophagy induction, in which the negative feedback of TORC1 activation has been known previously, and the positive feedback between TORC1 and Atg1 complex formation is introduced according to the similarity of Drosophila and mammalian cells. We demonstrate that the two feedback loops play distinct roles in autophagy regulation. The positive feedback is pro-survival, whereas the negative feedback has little effect on the survival of population during starvation. In addition, autophagy deficient cells can be rescued from starvation by amino acid exchanges from their neighboring wild type cells. PMID:27103581

  20. Modelling Anopheles gambiae s.s. Population Dynamics with Temperature- and Age-Dependent Survival.

    PubMed

    Christiansen-Jucht, Céline; Erguler, Kamil; Shek, Chee Yan; Basáñez, María-Gloria; Parham, Paul E

    2015-06-01

    Climate change and global warming are emerging as important threats to human health, particularly through the potential increase in vector- and water-borne diseases. Environmental variables are known to affect substantially the population dynamics and abundance of the poikilothermic vectors of disease, but the exact extent of this sensitivity is not well established. Focusing on malaria and its main vector in Africa, Anopheles gambiae sensu stricto, we present a set of novel mathematical models of climate-driven mosquito population dynamics motivated by experimental data suggesting that in An. gambiae, mortality is temperature and age dependent. We compared the performance of these models to that of a "standard" model ignoring age dependence. We used a longitudinal dataset of vector abundance over 36 months in sub-Saharan Africa for comparison between models that incorporate age dependence and one that does not, and observe that age-dependent models consistently fitted the data better than the reference model. This highlights that including age dependence in the vector component of mosquito-borne disease models may be important to predict more reliably disease transmission dynamics. Further data and studies are needed to enable improved fitting, leading to more accurate and informative model predictions for the An. gambiae malaria vector as well as for other disease vectors. PMID:26030468

  1. Modelling Anopheles gambiae s.s. Population Dynamics with Temperature- and Age-Dependent Survival

    PubMed Central

    Christiansen-Jucht, Céline; Erguler, Kamil; Shek, Chee Yan; Basáñez, María-Gloria; Parham, Paul E.

    2015-01-01

    Climate change and global warming are emerging as important threats to human health, particularly through the potential increase in vector- and water-borne diseases. Environmental variables are known to affect substantially the population dynamics and abundance of the poikilothermic vectors of disease, but the exact extent of this sensitivity is not well established. Focusing on malaria and its main vector in Africa, Anopheles gambiae sensu stricto, we present a set of novel mathematical models of climate-driven mosquito population dynamics motivated by experimental data suggesting that in An. gambiae, mortality is temperature and age dependent. We compared the performance of these models to that of a “standard” model ignoring age dependence. We used a longitudinal dataset of vector abundance over 36 months in sub-Saharan Africa for comparison between models that incorporate age dependence and one that does not, and observe that age-dependent models consistently fitted the data better than the reference model. This highlights that including age dependence in the vector component of mosquito-borne disease models may be important to predict more reliably disease transmission dynamics. Further data and studies are needed to enable improved fitting, leading to more accurate and informative model predictions for the An. gambiae malaria vector as well as for other disease vectors. PMID:26030468

  2. POPULATION DYNAMICS OF AMBIENT AND ALTERED EARTHWORM COMMUNITIES IN ROW-CROP AGROECOSYSTEMS IN OHIO, USA

    EPA Science Inventory

    Although earthworms are known to influence agroecosystem processes, there are relatively few long-term studies addressing population dynamics under cropping systems in which earthworm populations were intentionally altered. We assessed earthworm communities from fall 1994 to spr...

  3. Cryptic Population Dynamics: Rapid Evolution Masks Trophic Interactions

    PubMed Central

    Yoshida, Takehito; Ellner, Stephen P; Jones, Laura E; Bohannan, Brendan J. M; Lenski, Richard E; Hairston, Nelson G

    2007-01-01

    Trophic relationships, such as those between predator and prey or between pathogen and host, are key interactions linking species in ecological food webs. The structure of these links and their strengths have major consequences for the dynamics and stability of food webs. The existence and strength of particular trophic links has often been assessed using observational data on changes in species abundance through time. Here we show that very strong links can be completely missed by these kinds of analyses when changes in population abundance are accompanied by contemporaneous rapid evolution in the prey or host species. Experimental observations, in rotifer-alga and phage-bacteria chemostats, show that the predator or pathogen can exhibit large-amplitude cycles while the abundance of the prey or host remains essentially constant. We know that the species are tightly linked in these experimental microcosms, but without this knowledge, we would infer from observed patterns in abundance that the species are weakly or not at all linked. Mathematical modeling shows that this kind of cryptic dynamics occurs when there is rapid prey or host evolution for traits conferring defense against attack, and the cost of defense (in terms of tradeoffs with other fitness components) is low. Several predictions of the theory that we developed to explain the rotifer-alga experiments are confirmed in the phage-bacteria experiments, where bacterial evolution could be tracked. Modeling suggests that rapid evolution may also confound experimental approaches to measuring interaction strength, but it identifies certain experimental designs as being more robust against potential confounding by rapid evolution. PMID:17803356

  4. Comparative Population Dynamics of Two Closely Related Species Differing in Ploidy Level

    PubMed Central

    Černá, Lucie; Münzbergová, Zuzana

    2013-01-01

    Background Many studies compare the population dynamics of single species within multiple habitat types, while much less is known about the differences in population dynamics in closely related species in the same habitat. Additionally, comparisons of the effect of habitat types and species are largely missing. Methodology and Principal Findings We estimated the importance of the habitat type and species for population dynamics of plants. Specifically, we compared the dynamics of two closely related species, the allotetraploid species Anthericum liliago and the diploid species Anthericum ramosum, occurring in the same habitat type. We also compared the dynamics of A. ramosum in two contrasting habitats. We examined three populations per species and habitat type. The results showed that single life history traits as well as the mean population dynamics of A. liliago and A. ramosum from the same habitat type were more similar than the population dynamics of A. ramosum from the two contrasting habitats. Conclusions Our findings suggest that when transferring knowledge regarding population dynamics between populations, we need to take habitat conditions into account, as these conditions appear to be more important than the species involved (ploidy level). However, the two species differ significantly in their overall population growth rates, indicating that the ploidy level has an effect on species performance. In contrast to what has been suggested by previous studies, we observed a higher population growth rate in the diploid species. This is in agreement with the wider range of habitats occupied by the diploid species. PMID:24116057

  5. A spatial ecosystem and populations dynamics model (SEAPODYM) Modeling of tuna and tuna-like populations

    NASA Astrophysics Data System (ADS)

    Lehodey, Patrick; Senina, Inna; Murtugudde, Raghu

    2008-09-01

    An enhanced version of the spatial ecosystem and population dynamics model SEAPODYM is presented to describe spatial dynamics of tuna and tuna-like species in the Pacific Ocean at monthly resolution over 1° grid-boxes. The simulations are driven by a bio-physical environment predicted from a coupled ocean physical-biogeochemical model. This new version of SEAPODYM includes expanded definitions of habitat indices, movements, and natural mortality based on empirical evidences. A thermal habitat of tuna species is derived from an individual heat budget model. The feeding habitat is computed according to the accessibility of tuna predator cohorts to different vertically migrating and non-migrating micronekton (mid-trophic) functional groups. The spawning habitat is based on temperature and the coincidence of spawning fish with presence or absence of predators and food for larvae. The successful larval recruitment is linked to spawning stock biomass. Larvae drift with currents, while immature and adult tuna can move of their own volition, in addition to being advected by currents. A food requirement index is computed to adjust locally the natural mortality of cohorts based on food demand and accessibility to available forage components. Together these mechanisms induce bottom-up and top-down effects, and intra- (i.e. between cohorts) and inter-species interactions. The model is now fully operational for running multi-species, multi-fisheries simulations, and the structure of the model allows a validation from multiple data sources. An application with two tuna species showing different biological characteristics, skipjack ( Katsuwonus pelamis) and bigeye ( Thunnus obesus), is presented to illustrate the capacity of the model to capture many important features of spatial dynamics of these two different tuna species in the Pacific Ocean. The actual validation is presented in a companion paper describing the approach to have a rigorous mathematical parameter optimization

  6. Population dynamics and ecology of Arcobacter in sewage

    PubMed Central

    Fisher, Jenny C.; Levican, Arturo; Figueras, María J.; McLellan, Sandra L.

    2014-01-01

    Arcobacter species are highly abundant in sewage where they often comprise approximately 5–11% of the bacterial community. Oligotyping of sequences amplified from the V4V5 region of the 16S rRNA gene revealed Arcobacter populations from different cities were similar and dominated by 1–3 members, with extremely high microdiversity in the minor members. Overall, nine subgroups within the Arcobacter genus accounted for >80% of the total Arcobacter sequences in all samples analyzed. The distribution of oligotypes varied by both sample site and temperature, with samples from the same site generally being more similar to each other than other sites. Seven oligotypes matched with 100% identity to characterized Arcobacter species, but the remaining 19 abundant oligotypes appear to be unknown species. Sequences representing the two most abundant oligotypes matched exactly to the reference strains for A. cryaerophilus group 1B (CCUG 17802) and group 1A (CCUG 17801T), respectively. Oligotype 1 showed generally lower relative abundance in colder samples and higher relative abundance in warmer samples; the converse was true for Oligotype 2. Ten other oligotypes had significant positive or negative correlations between temperature and proportion in samples as well. The oligotype that corresponded to A. butzleri, the Arcobacter species most commonly isolated by culturing in sewage studies, was only the eleventh most abundant oligotype. This work suggests that Arcobacter populations within sewer infrastructure are modulated by temperature. Furthermore, current culturing methods used for identification of Arcobacter fail to identify some abundant members of the community and may underestimate the presence of species with affinities for growth at lower temperatures. Understanding the ecological factors that affect the survival and growth of Arcobacter spp. in sewer infrastructure may better inform the risks associated with these emerging pathogens. PMID:25426103

  7. Phenotypic plasticity in growth and fecundity induced by strong population fluctuations affects reproductive traits of female fish.

    PubMed

    Karjalainen, Juha; Urpanen, Olli; Keskinen, Tapio; Huuskonen, Hannu; Sarvala, Jouko; Valkeajärvi, Pentti; Marjomäki, Timo J

    2016-02-01

    Fish are known for their high phenotypic plasticity in life-history traits in relation to environmental variability, and this is particularly pronounced among salmonids in the Northern Hemisphere. Resource limitation leads to trade-offs in phenotypic plasticity between life-history traits related to the reproduction, growth, and survival of individual fish, which have consequences for the age and size distributions of populations, as well as their dynamics and productivity. We studied the effect of plasticity in growth and fecundity of vendace females on their reproductive traits using a series of long-term incubation experiments. The wild parental fish originated from four separate populations with markedly different densities, and hence naturally induced differences in their growth and fecundity. The energy allocation to somatic tissues and eggs prior to spawning served as a proxy for total resource availability to individual females, and its effects on offspring survival and growth were analyzed. Vendace females allocated a rather constant proportion of available energy to eggs (per body mass) despite different growth patterns depending on the total resources in the different lakes; investment into eggs thus dictated the share remaining for growth. The energy allocation to eggs per mass was higher in young than in old spawners and the egg size and the relative fecundity differed between them: Young females produced more and smaller eggs and larvae than old spawners. In contrast to earlier observations of salmonids, a shortage of maternal food resources did not increase offspring size and survival. Vendace females in sparse populations with ample resources and high growth produced larger eggs and larvae. Vendace accommodate strong population fluctuations by their high plasticity in growth and fecundity, which affect their offspring size and consequently their recruitment and productivity, and account for their persistence and resilience in the face of high

  8. Reheating dynamics affects non-perturbative decay of spectator fields

    NASA Astrophysics Data System (ADS)

    Enqvist, Kari; Lerner, Rose N.; Rusak, Stanislav

    2013-11-01

    The behaviour of oscillating scalar spectator fields after inflation depends on the thermal background produced by inflaton decay. Resonant decay of the spectator is often blocked by large induced thermal masses. We account for the finite decay width of the inflaton and the protracted build-up of the thermal bath to determine the early evolution of a homogeneous spectator field σ coupled to the Higgs Boson Φ through the term g2σ2Φ2, the only renormalisable coupling of a new scalar to the Standard Model. We find that for very large higgs-spectator coupling ggtrsim10-3, the resonance is not always blocked as was previously suggested. As a consequence, the oscillating spectator can decay quickly. For other parameter values, we find that although qualitative features of the thermal blocking still hold, the dynamics are altered compared to the instant decay case. These findings are important for curvaton models, where the oscillating field must be relatively long lived in order to produce the curvature perturbation. They are also relevant for other spectator fields, which must decay sufficiently early to avoid spoiling the predictions of baryogenesis and nucleosynthesis.

  9. Dynamic touch is affected in children with cerebral palsy.

    PubMed

    Ocarino, Juliana M; Fonseca, Sergio T; Silva, Paula L P; Gonçalves, Gabriela G P; Souza, Thales R; Mancini, Marisa C

    2014-02-01

    Children with developmental disorders such as cerebral palsy have limited opportunities for effortful interactions with objects and tools. The goal of the study was to investigate whether children with cerebral palsy have deficits in their ability to perceive object length by dynamic touch when compared to typically developing children. Fourteen children with typical development and 12 children with cerebral palsy were asked to report the length of hand-held rods after wielding them out of sight. Multilevel regression models indicated that I1 (maximum principal moment of inertia) was a significant predictor of perceived length - LP (p<.0001). The effect of I1 on LP was significantly different among children (p=.001) and the presence of cerebral palsy (group factor) partially explained such variance (p=.002). In addition, accuracy and reliability of the length judgments made by children with cerebral palsy were significantly lower than the typically developing children (p<.05). Theoretical and clinical implications of these results were identified and discussed. PMID:24054355

  10. Reheating dynamics affects non-perturbative decay of spectator fields

    SciTech Connect

    Enqvist, Kari; Lerner, Rose N.; Rusak, Stanislav E-mail: rose.lerner@helsinki.fi

    2013-11-01

    The behaviour of oscillating scalar spectator fields after inflation depends on the thermal background produced by inflaton decay. Resonant decay of the spectator is often blocked by large induced thermal masses. We account for the finite decay width of the inflaton and the protracted build-up of the thermal bath to determine the early evolution of a homogeneous spectator field σ coupled to the Higgs Boson Φ through the term g{sup 2}σ{sup 2}Φ{sup 2}, the only renormalisable coupling of a new scalar to the Standard Model. We find that for very large higgs-spectator coupling g∼>10{sup −3}, the resonance is not always blocked as was previously suggested. As a consequence, the oscillating spectator can decay quickly. For other parameter values, we find that although qualitative features of the thermal blocking still hold, the dynamics are altered compared to the instant decay case. These findings are important for curvaton models, where the oscillating field must be relatively long lived in order to produce the curvature perturbation. They are also relevant for other spectator fields, which must decay sufficiently early to avoid spoiling the predictions of baryogenesis and nucleosynthesis.

  11. Effects of Infection on Honey Bee Population Dynamics: A Model

    PubMed Central

    Betti, Matt I.; Wahl, Lindi M.; Zamir, Mair

    2014-01-01

    We propose a model that combines the dynamics of the spread of disease within a bee colony with the underlying demographic dynamics of the colony to determine the ultimate fate of the colony under different scenarios. The model suggests that key factors in the survival or collapse of a honey bee colony in the face of an infection are the rate of transmission of the infection and the disease-induced death rate. An increase in the disease-induced death rate, which can be thought of as an increase in the severity of the disease, may actually help the colony overcome the disease and survive through winter. By contrast, an increase in the transmission rate, which means that bees are being infected at an earlier age, has a drastic deleterious effect. Another important finding relates to the timing of infection in relation to the onset of winter, indicating that in a time interval of approximately 20 days before the onset of winter the colony is most affected by the onset of infection. The results suggest further that the age of recruitment of hive bees to foraging duties is a good early marker for the survival or collapse of a honey bee colony in the face of infection, which is consistent with experimental evidence but the model provides insight into the underlying mechanisms. The most important result of the study is a clear distinction between an exposure of the honey bee colony to an environmental hazard such as pesticides or insecticides, or an exposure to an infectious disease. The results indicate unequivocally that in the scenarios that we have examined, and perhaps more generally, an infectious disease is far more hazardous to the survival of a bee colony than an environmental hazard that causes an equal death rate in foraging bees. PMID:25329468

  12. Population dynamics of a pathogen: the conundrum of vivax malaria.

    PubMed

    McQueen, Philip G

    2010-08-01

    Building a mathematical model of population dynamics of pathogens within their host involves considerations of factors similar to those in ecology, as pathogens can prey on cells in the host. But within the multicellular host, attacked cell types are integrated with other cellular systems, which in turn intervene in the infection. For example, immune responses attempt to sense and then eliminate or contain pathogens, and homeostatic mechanisms try to compensate for cell loss. This review focuses on modeling applied to malarias, diseases caused by single-cell eukaryote parasites that infect red blood cells, with special concern given to vivax malaria, a disease often thought to be benign (if sometimes incapacitating) because the parasite only attacks a small proportion of red blood cells, the very youngest ones. However, I will use mathematical modeling to argue that depletion of this pool of red blood cells can be disastrous to the host if growth of the parasite is not vigorously check by host immune responses. Also, modeling can elucidate aspects of new field observations that indicate that vivax malaria is more dangerous than previously thought. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s12551-010-0034-3) contains supplementary material, which is available to authorized users. PMID:20730124

  13. Spatiotemporal dynamics of insect pest population under viral infection.

    PubMed

    Ghosh, Suma; Bhattacharyya, Samit

    2013-07-01

    The interrelationship between pathogen infection and host mobility is of great importance for successful spread of disease in spatial pest population. As spread of infection depends on horizontal transmission of pathogen, there are numerous factors like susceptibility, latent period, host movement that influence overall effectiveness of the control policy. Initiation of new infection cycle depends on density of infected inoculum in the site. So, spatial movement of infected hosts during the course of infection influence the dynamics. Also, infected individuals are more vulnerable to predators and hence production of virus particles in the site depends on predation to some extent. We derive a four dimensional delayed reaction-diffusion model in one spatial dimension and compute the minimum travelling speed of transmission of infection. We show that the minimum speed is sensitive to several parameters of the system. For example, the minimum speed decreases only with increase in delay in lysis process, but otherwise it increases with increase in force of infection, diffusivity of infectives or per capita virus production. A concluding discussion with numerical simulation is presented in the end. PMID:23562890

  14. Fluctuation Relations of Fitness and Information in Population Dynamics

    NASA Astrophysics Data System (ADS)

    Kobayashi, Tetsuya J.; Sughiyama, Yuki

    2015-12-01

    Phenotype switching with and without sensing environment is a common strategy of organisms to survive in a fluctuating environment. Understanding the evolutionary advantages of switching and sensing requires a quantitative evaluation of their fitness gain and its fluctuation together with the conditions for the switching and sensing strategies being adapted to a given environment. In this work, by using a pathwise formulation of the population dynamics, we show that the optimal switching strategy is characterized by a consistency condition for time-forward and backward path probabilities. The formulation also clarifies the underlying information-theoretic aspect of selection as a passive information compression. The loss of fitness by a suboptimal strategy is also shown to satisfy a fluctuation relation, which provides us with the information on how environmental fluctuation impacts the advantages of the optimal strategy. These results are naturally extended to the situation that organisms can use an environmental signal by actively sensing the environment. The fluctuation relations of the fitness gain by sensing are derived in which the multivariate mutual information among the phenotype, the environment, and the signal plays the role to quantify the relevant information in the signal for the fitness gain.

  15. Tropical forest landscape dynamics: Population consequences for neotropical lianas, genus Passiflora

    NASA Astrophysics Data System (ADS)

    Plowes, Robert Merrick

    Treefall gaps in rainforest landscapes play a crucial role in providing opportunities for establishment and growth of rare, light-demanding plants such as Passifora vines in Corcovado rainforests, Costa Rica. This study considers the interplay of landscape dynamics with plant life history traits and strategies in an ephemeral patch network. In Chapter One, I show how patch quality dynamics and propagule dispersal affect colonization of treefall gaps by Passifora vitifolia. Recruitment required high patch quality, exceeding 3 hours of sunlight and patches closed after about 6 years. Colonization by seed dispersal (80%) was constrained by patch quality and isolation, while clonal growth from dormant plants (20%) was limited to rare adjacent patches. Since patch turnover is critical in these systems, Chapter Two is focused on factors affecting canopy structure. I showed that prior landuse altered the dynamics of frequent, small-scale disturbances during succession following a single, large deforestation event. Here, I used Landsat subpixel analysis, aerial photographs and field surveys to demonstrate major changes in dynamics of regenerating canopies following release from agricultural activity in 1975. Little work has considered the role of life history traits in persistence of patchy populations, and so in Chapter Three I asked what life history strategies are used by 9 Passiflora species that occur in these transient forest gaps. Although Passiflora species exhibited differences in dormancy or dispersal strategies, abundance was not associated with any one strategy. Elasticities of vital rates (stasis, growth and fecundity) of P. vitifolia differed empirically in old growth and regenerating forests. To explore population responses to changes in landscape parameters or life history strategies, I created a spatially-explicit individual-based model. Simulations indicate that plant types with a dormancy phase have a greater suite of responses since they persist after

  16. Oral impacts affecting daily performance in a low dental disease Thai population.

    PubMed

    Adulyanon, S; Vourapukjaru, J; Sheiham, A

    1996-12-01

    The aim of the study was to measure incidence of oral impacts on daily performances and their related features in a low dental disease population. 501 people aged 35-44 years in 16 rural villages in Ban Phang district, Khon Kaen, Thailand, were interviewed about oral impacts on nine physical, psychological and social aspects of performance during the past 6 months, and then had an oral examination. The clinical and behavioural data showed that the sample had low caries (DMFT = 2.7) and a low utilization of dental services. 73.6% of all subjects had at least one daily performance affected by an oral impact. The highest incidence of performances affected were Eating (49.7%), Emotional stability (46.5%) and Smiling (26.1%). Eating, Emotional stability and Cleaning teeth performances had a high frequency or long duration of impacts, but a low severity. The low frequency performances; Physical activities, Major role activity and Sleeping were rated as high severity. Pain and discomfort were mainly perceived as the causes of impacts (40.1%) for almost every performance except Smiling. Toothache was the major causal oral condition (32.7%) of almost all aspects of performance. It was concluded that this low caries people have as high an incidence of oral impacts as industrialized, high dental disease populations. Frequency and severity presented the paradoxical effect on different performances and should both be taken into account for overall estimation of impacts. PMID:9007354

  17. Evolutionary Game Dynamics in Finite Populations with Strong Selection and Weak Mutation

    PubMed Central

    Fudenberg, Drew; Nowak, Martin A.; Taylor, Christine

    2011-01-01

    We study stochastic game dynamics in finite populations. To this end we extend the classical Moran process to incorporate frequency-dependent selection and mutation. For 2 × 2 games, we give a complete analysis of the long-run behavior when mutation rates are small. For 3 × 3 coordination games, we provide a simple rule to determine which strategy will be selected in large populations. The expected motion in our model resembles the standard replicator dynamics when the population is large, but is qualitatively different when the population is small. Our analysis shows that even in large finite populations the behavior of a replicator-like system can be different from that of the standard replicator dynamics. As an application, we consider selective language dynamics. We determine which language will be spoken in finite large populations. The results have an intuitive interpretation but would not be expected from an analysis of the replicator dynamics. PMID:16987535

  18. An indication of major genes affecting hip and elbow dysplasia in four Finnish dog populations.

    PubMed

    Mäki, K; Janss, L L G; Groen, A F; Liinamo, A-E; Ojala, M

    2004-05-01

    The aim of the study was to assess the possible existence of major genes influencing hip and elbow dysplasia in four dog populations. A Bayesian segregation analysis was performed separately on each population. In total, 34 140 dogs were included in the data set. Data were analysed with both a polygenic and a mixed inheritance model. Polygenic models included fixed and random environmental effects and additive genetic effects. To apply mixed inheritance models, the effect of a major gene was added to the polygenic models. The major gene was modelled as an autosomal biallelic locus with Mendelian transmission probabilities. Gibbs sampling and a Monte Carlo Markov Chain algorithm were used. The goodness-of-fit of the different models were compared using the residual sum-of-squares. The existence of a major gene was considered likely for hip dysplasia in all the breeds and for elbow dysplasia in one breed. Several procedures were followed to exclude the possible false detection of major genes based on non-normality of data: permuted datasets were analysed, data-transformations were applied, and residuals were judged for normality. Allelic effects at the major gene locus showed nearly to complete dominance, with a recessive, unfavourable allele in both traits. Relatively high estimates of the frequencies of unfavourable alleles in each breed suggest that considerable genetic progress would be possible by selection against major genes. However, the major genes that are possibly affecting hip and elbow dysplasia in these populations will require further study. PMID:14997179

  19. Histopathology of growth anomaly affecting the coral, Montipora capitata: implications on biological functions and population viability.

    PubMed

    Burns, John H R; Takabayashi, Misaki

    2011-01-01

    Growth anomalies (GAs) affect the coral, Montipora capitata, at Wai'ōpae, southeast Hawai'i Island. Our histopathological analysis of this disease revealed that the GA tissue undergoes changes which compromise anatomical machinery for biological functions such as defense, feeding, digestion, and reproduction. GA tissue exhibited significant reductions in density of ova (66.1-93.7%), symbiotic dinoflagellates (38.8-67.5%), mesenterial filaments (11.2-29.0%), and nematocytes (28.8-46.0%). Hyperplasia of the basal body wall but no abnormal levels of necrosis and algal or fungal invasion was found in GA tissue. Skeletal density along the basal body wall was significantly reduced in GAs compared to healthy or unaffected sections. The reductions in density of the above histological features in GA tissue were collated with disease severity data to quantify the impact of this disease at the colony and population level. Resulting calculations showed this disease reduces the fecundity of M. capitata colonies at Wai'ōpae by 0.7-49.6%, depending on GA severity, and the overall population fecundity by 2.41±0.29%. In sum, GA in this M. capitata population reduces the coral's critical biological functions and increases susceptibility to erosion, clearly defining itself as a disease and an ecological threat. PMID:22205976

  20. Local divergence of thermal reaction norms among amphibian populations is affected by pond temperature variation.

    PubMed

    Richter-Boix, Alex; Katzenberger, Marco; Duarte, Helder; Quintela, María; Tejedo, Miguel; Laurila, Anssi

    2015-08-01

    Although temperature variation is known to cause large-scale adaptive divergence, its potential role as a selective factor over microgeographic scales is less well-understood. Here, we investigated how variation in breeding pond temperature affects divergence in multiple physiological (thermal performance curve and critical thermal maximum [CTmax]) and life-history (thermal developmental reaction norms) traits in a network of Rana arvalis populations. The results supported adaptive responses to face two main constraints limiting the evolution of thermal adaptation. First, we found support for the faster-slower model, indicating an adaptive response to compensate for the thermodynamic constraint of low temperatures in colder environments. Second, we found evidence for the generalist-specialist trade-off with populations from colder and less thermally variable environments exhibiting a specialist phenotype performing at higher rates but over a narrower range of temperatures. By contrast, the local optimal temperature for locomotor performance and CTmax did not match either mean or maximum pond temperatures. These results highlight the complexity of the adaptive multiple-trait thermal responses in natural populations, and the role of local thermal variation as a selective force driving diversity in life-history and physiological traits in the presence of gene flow. PMID:26118477

  1. Retrospective analysis of lung function abnormalities of Bhopal gas tragedy affected population

    PubMed Central

    De, Sajal

    2012-01-01

    Background & objectives: A large numbers of subjects were exposed to the aerosol of methyl isocyanate (MIC) during Bhopal gas disaster and lung was one of the most commonly affected organs. The aim of the present study was to analyze retrospectively the lung function abnormalities among the surviving MIC exposed population (gas victims) and to compare it with the non-MIC exposed (non gas exposed) population. Methods: The spirometry data of both gas victims and non gas exposed population who attended the Bhopal Memorial Hospital & Research Centre for evaluation of their respiratory complaints from August 2001 to December 2009, were retrospectively evaluated and compared. Results: A total 4782 gas victims and 1190 non gas exposed individuals performed spirometry during the study period. Among the gas victims, obstructive pattern was the commonest (50.8%) spirometric abnormality followed by restrictive pattern (13.3%). The increased relative risk of developing restrictive abnormality among gas victims was observed in 20-29 yr age group only (adjusted relative risk: 2.94, P<0.001). Male gas victims were more affected by severe airflow obstruction than females and the overall increased relative risk (1.33 to 1.45, P<0.001) of developing obstructive pattern among gas victims was observed. Interpretation & conclusions: The present study showed that the relative risk for pulmonary function abnormalities in gas victims was significantly more among those who were young at the time of disaster. Increased smoking habit among gas victims might have played an additive effect on predominance of obstructive pattern in spirometry. PMID:22446861

  2. The relative importance of direct and indirect effects of hunting mortality on the population dynamics of brown bears.

    PubMed

    Gosselin, Jacinthe; Zedrosser, Andreas; Swenson, Jon E; Pelletier, Fanie

    2015-01-01

    There is increasing evidence of indirect effects of hunting on populations. In species with sexually selected infanticide (SSI), hunting may decrease juvenile survival by increasing male turnover. We aimed to evaluate the relative importance of direct and indirect effects of hunting via SSI on the population dynamics of the Scandinavian brown bear (Ursus arctos). We performed prospective and retrospective demographic perturbation analyses for periods with low and high hunting pressures. All demographic rates, except yearling survival, were lower under high hunting pressure, which led to a decline in population growth under high hunting pressure (λ = 0.975; 95% CI = 0.914-1.011). Hunting had negative indirect effects on the population through an increase in SSI, which lowered cub survival and possibly also fecundity rates. Our study suggests that SSI could explain 13.6% of the variation in population growth. Hunting also affected the relative importance of survival and fecundity of adult females for population growth, with fecundity being more important under low hunting pressure and survival more important under high hunting pressure. Our study sheds light on the importance of direct and indirect effects of hunting on population dynamics, and supports the contention that hunting can have indirect negative effects on populations through SSI. PMID:25392469

  3. Ecological and Dynamical Study of the Creative Process and Affects of Scientific Students Working in Groups

    ERIC Educational Resources Information Center

    Peilloux, Aurélien; Botella, Marion

    2016-01-01

    Although creativity has drawn the attention of researchers during the past century, collaborative processes have barely been investigated. In this article, the collective dimension of a creative process is investigated, based on a dynamic and ecological approach that includes an affective component. "Dynamic" means that the creative…

  4. Does cannibalism of larvae by adults affect settlement and connectivity of mussel populations?

    NASA Astrophysics Data System (ADS)

    Porri, Francesca; Jordaan, Tembisa; McQuaid, Christopher D.

    2008-09-01

    Intertidal population dynamics are driven by a complex series of processes, including larval supply and the possibility of larval predation by benthic animals such as filter-feeders. We hypothesised that cannibalism by adults could play a major role in the population connectivity of mussel populations by removing larvae as they attempt to settle in the adult habitat. Specifically, we tested hypotheses that consumption of mussel larvae by adults removes a significant proportion of potential settlers and is influenced by both settlement intensity and tidal state (flooding or ebbing). Predation of mussel larvae by adult mussels was investigated on incoming and ebbing tides during four spring tides by analysing the gut contents of adult Perna perna and Mytilus galloprovincialis collected from the low intertidal mussel zone between October 2005 and January 2006. Consumption rates were then compared with estimates of successful settler densities on natural beds. The results showed that mortality of competent mussel larvae through adult ingestion removes up to 77% a of potential settlers. Rates of larval consumption were highest during months of intense settlement, suggesting that mussels feed opportunistically, filtering a relatively fixed volume of water and removing particles, including larvae, in proportion to their densities in the water. Rates of larviphagy were also higher during receding than incoming tides. We suggest that this is due to changes in larval density or, more probably, in adult filtration efficiency that are related to the state of the tide. Despite significant effects of both tidal state and settlement intensity on rates of larval ingestion, neither had a significant effect on the proportion of potential settlers removed. During settlement more than half of all potential settlers are lost through cannibalism, with potentially serious consequences for population maintenance. The results highlight the paradoxical nature of the evolution of settlement

  5. A dynamical-systems approach for computing ice-affected streamflow

    USGS Publications Warehouse

    Holtschlag, David J.

    1996-01-01

    A dynamical-systems approach was developed and evaluated for computing ice-affected streamflow. The approach provides for dynamic simulation and parameter estimation of site-specific equations relating ice effects to routinely measured environmental variables. Comparison indicates that results from the dynamical-systems approach ranked higher than results from 11 analytical methods previously investigated on the basis of accuracy and feasibility criteria. Additional research will likely lead to further improvements in the approach.

  6. The Dynamic Role of Personality States in Mediating the Relationship between Extraversion and Positive Affect

    PubMed Central

    Wilt, Joshua; Noftle, Erik E.; Fleeson, William; Spain, Jana S.

    2012-01-01

    Objective One of the most noteworthy and robust findings in personality psychology is the relationship between extraversion and positive affect. Existing theories have debated the origins and nature of this relationship, offering both structural/fixed and environmental/dynamic explanations. We tested the novel and straightforward dynamic hypothesis that part of the reason trait extraversion predicts trait positive affect is through an increased propensity to enact extraverted states, which in turn leads to experiencing more positive affect states. Method We report five experience sampling studies (and a meta-analysis of primary studies) conducted in natural environments and laboratory settings in which undergraduate participants (N = 241) provided ratings of trait extraversion, trait positive affect, extraversion states, and positive affect states. Results Results of primary studies and the meta analysis showed that relationships between trait extraversion and trait positive affect were partially mediated by aggregated extraversion states and aggregated positive affect states. Conclusions The results supported our dynamic hypothesis and suggested that dynamic explanations of the relationship between trait extraversion and trait positive affect are compatible with structural explanations. An important implication of these findings is that individuals might be able to increase their happiness by self-regulating their extraverted states. PMID:22092066

  7. Regulatory effects on the population dynamics and wave propagation in a cell lineage model.

    PubMed

    Wang, Mao-Xiang; Ma, Yu-Qiang; Lai, Pik-Yin

    2016-03-21

    We consider the interplay of cell proliferation, cell differentiation (and de-differentiation), cell movement, and the effect of feedback regulations on the population and propagation dynamics of different cell types in a cell lineage model. Cells are assumed to secrete and respond to negative feedback molecules which act as a control on the cell lineage. The cell densities are described by coupled reaction-diffusion partial differential equations, and the propagating wave front solutions in one dimension are investigated analytically and by numerical solutions. In particular, wavefront propagation speeds are obtained analytically and verified by numerical solutions of the equations. The emphasis is on the effects of the feedback regulations on different stages in the cell lineage. It is found that when the progenitor cell is negatively regulated, the populations of the cell lineage are strongly down-regulated with the steady growth rate of the progenitor cell being driven to zero beyond a critical regulatory strength. An analytic expression for the critical regulation strength in terms of the model parameters is derived and verified by numerical solutions. On the other hand, if the inhibition is acting on the differentiated cells, the change in the population dynamics and wave propagation speed is small. In addition, it is found that only the propagating speed of the progenitor cells is affected by the regulation when the diffusion of the differentiated cells is large. In the presence of de-differentiation, the effect on down-regulating the progenitor population is weakened and there is no effect on the propagation speed due to regulation, suggesting that the effect of regulatory control is diminished by de-differentiation pathways. PMID:26796226

  8. DYNAMICS OF NEMATODE POPULATIONS IN CACAO GROWN UNDER TRADIONALLY SYSTEM OF MANAGEMENT IN PERUVIAN AMAZON

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nature of crops and management systems greatly influences population dynamics of parasitic and nonparasitic nematodes in soil. An experiment was undertaken at Tropical Crop Research institute (ICT), Tarapoto, Peru to assess the population dynamics of nematodes in a Cocoa (Theobroma cacao L.)-Banana ...

  9. Genetic Diversity Affects the Daily Transcriptional Oscillations of Marine Microbial Populations

    PubMed Central

    Shilova, Irina N.; Robidart, Julie C.; DeLong, Edward F.; Zehr, Jonathan P.

    2016-01-01

    Marine microbial communities are genetically diverse but have robust synchronized daily transcriptional patterns at the genus level that are similar across a wide variety of oceanic regions. We developed a microarray-inspired gene-centric approach to resolve transcription of closely-related but distinct strains/ecotypes in high-throughput sequence data. Applying this approach to the existing metatranscriptomics datasets collected from two different oceanic regions, we found unique and variable patterns of transcription by individual taxa within the abundant picocyanobacteria Prochlorococcus and Synechococcus, the alpha Proteobacterium Pelagibacter and the eukaryotic picophytoplankton Ostreococcus. The results demonstrate that marine microbial taxa respond differentially to variability in space and time in the ocean. These intra-genus individual transcriptional patterns underlie whole microbial community responses, and the approach developed here facilitates deeper insights into microbial population dynamics. PMID:26751368

  10. Identification and synthetic modeling of factors affecting American black duck populations

    USGS Publications Warehouse

    Conroy, Michael J.; Miller, Mark W.; Hines, James E.

    2002-01-01

    We reviewed the literature on factors potentially affecting the population status of American black ducks (Anas rupribes). Our review suggests that there is some support for the influence of 4 major, continental-scope factors in limiting or regulating black duck populations: 1) loss in the quantity or quality of breeding habitats; 2) loss in the quantity or quality of wintering habitats; 3) harvest, and 4) interactions (competition, hybridization) with mallards (Anas platyrhychos) during the breeding and/or wintering periods. These factors were used as the basis of an annual life cycle model in which reproduction rates and survival rates were modeled as functions of the above factors, with parameters of the model describing the strength of these relationships. Variation in the model parameter values allows for consideration of scientific uncertainty as to the degree each of these factors may be contributing to declines in black duck populations, and thus allows for the investigation of the possible effects of management (e.g., habitat improvement, harvest reductions) under different assumptions. We then used available, historical data on black duck populations (abundance, annual reproduction rates, and survival rates) and possible driving factors (trends in breeding and wintering habitats, harvest rates, and abundance of mallards) to estimate model parameters. Our estimated reproduction submodel included parameters describing negative density feedback of black ducks, positive influence of breeding habitat, and negative influence of mallard densities; our survival submodel included terms for positive influence of winter habitat on reproduction rates, and negative influences of black duck density (i.e., compensation to harvest mortality). Individual models within each group (reproduction, survival) involved various combinations of these factors, and each was given an information theoretic weight for use in subsequent prediction. The reproduction model with highest

  11. Sensitivity Analysis for Assessing Effects of Tree Population Dynamics on Soil Bioturbation

    NASA Astrophysics Data System (ADS)

    Martin, Y. E.; Johnson, E. A.

    2012-12-01

    Bioturbation due to tree root throw is thought to be an important process in soil production and soil mixing. Despite progress in our understanding of root throw processes, the tree population dynamics affecting the occurrence and timing of root throw events remain much less well explained. Unfortunately, research about forest dynamics is not always undertaken from the perspective of those interested in tree death, tree topple and associated root throw. As a result, the necessary field data about tree population dynamics is often unavailable for many locations. The acquisition of such data would allow for improved interpretation of root throw observations and for incorporation within numerical models of tree root throw occurrence. The present study uses our earlier tree population dynamics model calibrated for subalpine forests in the Canadian Rockies to test the sensitivity of forest parameters within the model that determine tree death, tree topple, root throw and soil bioturbation. Crown wildfire disturbance is the primary driver of tree population dynamics, with wind throw being mainly of local importance. The recruitment and mortality of trees during multiple generations of forest determine the number of live trees on the landscape at any given time. Tree death may occur due to competition/thinning of trees between wildfire events or as a result of the wildfire itself. Unless trees die due to sudden wind throw events (as mentioned above, this is only of local significance in our study area), they remain standing for some time period after tree death and before tree topple; these trees are referred to as standing dead trees. The duration of this time window and several other factors influence if a tree breaks at its base or upheaves a relatively intact root plate with attached sediment. Our field research has also suggested that a minimum dbh is required before a root plate is large enough to upheave notable amounts of sediment. Modelling results in this study

  12. Predicting shifts in dynamics of cannibalistic field populations using individual-based models.

    PubMed

    Persson, Lennart; de Roos, André M; Bertolo, Andrea

    2004-12-01

    The occurrence of qualitative shifts in population dynamical regimes has long been the focus of population biologists. Nonlinear ecological models predict that these shifts in dynamical regimes may occur as a result of parameter shifts, but unambiguous empirical evidence is largely restricted to laboratory populations. We used an individual-based modelling approach to predict dynamical shifts in field fish populations where the capacity to cannibalize differed between species. Model-generated individual growth trajectories that reflect different population dynamics were confronted with empirically observed growth trajectories, showing that our ordering and quantitative estimates of the different cannibalistic species in terms of life-history characteristics led to correct qualitative predictions of their dynamics. PMID:15590600

  13. New Mexico and the southwestern US are affected by a unique population of tomato spotted wilt virus (TSWV) strains.

    PubMed

    French, J M; Goldberg, N P; Randall, J J; Hanson, S F

    2016-04-01

    Tomato spotted wilt virus (TSWV) is an important pathogen of many ornamental, greenhouse and agronomic crops worldwide. TSWV also causes sporadic problems in a number of crops in New Mexico (NM). Nucleocapsid gene sequences obtained from six different crop species across the state over four different years were used to characterize the NM TSWV population. This analysis shows that NM is affected by a unique TSWV population that is part of larger independent population present in the southwestern US. This population likely arose due to geographic isolation and is related to other TSWV populations from the US, Spain, and Italy. PMID:26721573

  14. The protective function of personal growth initiative among a genocide-affected population in Rwanda.

    PubMed

    Blackie, Laura E R; Jayawickreme, Eranda; Forgeard, Marie J C; Jayawickreme, Nuwan

    2015-07-01

    The aim of the current study was to investigate the extent to which individual differences in personal growth initiative (PGI) were associated with lower reports of functional impairment of daily activities among a genocide-affected population in Rwanda. PGI measures an individual's motivation to develop as a person and the extent to which he or she is active in setting goals that work toward achieving self-improvement. We found that PGI was negatively associated with functional impairment when controlling for depression, posttraumatic stress disorder, and other demographic factors. Our results suggest that PGI may constitute an important mindset for facilitating adaptive functioning in the aftermath of adversity and in the midst of psychological distress, and as such they might have practical applications for the development of intervention programs. PMID:26147518

  15. Weather factors influencing the population dynamics of Culex pipiens (Diptera: Culicidae) in the Po Plain Valley, Italy (1997-2011).

    PubMed

    Carrieri, Marco; Fariselli, Piero; Maccagnani, Bettina; Angelini, Paola; Calzolari, Mattia; Bellini, Romeo

    2014-04-01

    The impact of weather variables on Culex pipiens L. (Diptera: Culicidae) population dynamics in the Po Valley, Northern Italy, a densely populated region containing the largest industrial and agricultural areas in Italy, was investigated. Monitoring of mosquitoes was carried out by using CO(2)-baited traps without light, collecting data weekly from 1700 to 0900 hours during the period May-September, from 1997 to 2011. Daily minimum, average, and maximum relative humidity; daily minimum, maximum, and average temperature; rainfall; and hydroclimatic balance (rainfall-potential evapotranspiration) were obtained from three weather stations within the surveillance zone. The average population dynamic trend over the 15-yr period showed a bell-shaped curve with a major peak in June and a secondary peak at the end of August in the rural areas, whereas bimodality was not evidenced in the urban areas. The correlation analyses showed that the mosquito seasonal population and the population in the period of maximum West Nile virus circulation (August-September) was mostly affected by the relative humidity registered from March to July, particularly in May, and, to a lower extent, also by hydroclimatic balance registered in April-July, and by the rainfall occurred in June-July. In addition, the rate of increase of the population during the spring months influenced the development of the mosquito population of the following months. PMID:24763101

  16. [Nonlinear effects on population dynamics related to age structure and fishery impact].

    PubMed

    Frisman, E Ia; Last, E V

    2005-01-01

    Population dynamics of commercial fish populations with an age structure was studied by the example of salmons. The relationship between the amount of catch on fishing efforts and total abundance of a stock fished is described by a nonlinear "trophic" function. Special attention is given to the analysis of population dynamics stability under conditions for maximum profit. Simulation results are compared to statistical data on the catch of Pacific salmon species in the Bering Sea. PMID:16240747

  17. Ontogenetic shifts in plant interactions vary with environmental severity and affect population structure.

    PubMed

    le Roux, Peter C; Shaw, Justine D; Chown, Steven L

    2013-10-01

    Environmental conditions and plant size may both alter the outcome of inter-specific plant-plant interactions, with seedlings generally facilitated more strongly than larger individuals in stressful habitats. However, the combined impact of plant size and environmental severity on interactions is poorly understood. Here, we tested explicitly for the first time the hypothesis that ontogenetic shifts in interactions are delayed under increasingly severe conditions by examining the interaction between a grass, Agrostis magellanica, and a cushion plant, Azorella selago, along two severity gradients. The impact of A. selago on A. magellanica abundance, but not reproductive effort, was related to A. magellanica size, with a trend for delayed shifts towards more negative interactions under greater environmental severity. Intermediate-sized individuals were most strongly facilitated, leading to differences in the size-class distribution of A. magellanica on the soil and on A. selago. The A. magellanica size-class distribution was more strongly affected by A. selago than by environmental severity, demonstrating that the plant-plant interaction impacts A. magellanica population structure more strongly than habitat conditions. As ontogenetic shifts in plant-plant interactions cannot be assumed to be constant across severity gradients and may impact species population structure, studies examining the outcome of interactions need to consider the potential for size- or age-related variation in competition and facilitation. PMID:23738758

  18. Ovarian Stimulation Affects the Population of Mouse Uterine NK Cells at Early Pregnancy

    PubMed Central

    Dorfeshan, Parvin; Moazzeni, Seyed Mohammad

    2013-01-01

    The aim of this study was to determine the influence of ovarian stimulation on endometrial mouse NK cell population. For superovulation, the female adult NMRI mice were injected i.p. with 10 IU of the pregnant mare serum gonadotropin followed 48 h later by an i.p. injection of 10 IU human chorionic gonadotropin hormone. Ovarian stimulated and nonstimulated mice were mated with fertile male. The presence of vaginal plug proved natural pregnancy, and this day was considered as day one of pregnancy. Tissue samples were prepared from the uterine horn and spleen of both groups of study on 7th day of pregnancy. Serum estradiol-17β and progesterone were measured at the same time. The tissue cryosections were prepared and double stained for CD 161 and CD3 markers, and NK cells population was analyzed. Relative frequency of NK cells was significantly lower in stroma and myometrium in hyperstimulated mice compared with the control group. However, no difference was seen in percentage of NK cells in spleen. The ovarian stimulation influences the proportion of uterine NK cells and may affect the embryo implantation. PMID:24350248

  19. Factors Enabling Access to HIV Voluntary Counseling and Testing for Key Affected Populations in Thailand.

    PubMed

    Thepthien, Bang-on; Srivanichakorn, Supattra; Apipornchaisakul, Kanya

    2015-10-01

    The objective was to study the factors that enabled persons at risk of HIV to obtain voluntary counseling and testing (VCT) in Thailand. This research was a cross-sectional study and data were collected during May to July 2013 in 8, purposively selected provinces. The method for selecting respondents used time-location quota sampling to achieve a total sample of 751 persons. The proportion who had VCT in the year prior to the survey was 56%.The significant enabling factors associated with VCT were having someone encourage them to go for testing and receiving information about VCT In addition, other significant factors for female sex workers were self-assessed risk for HIV and having had risk behavior, and for men who have sex with men the factors were awareness of eligibility for VCT. Thus, in order to achieve the VCT target for higher risk populations by 2016, there should be special mechanisms to inform the different groups, along with improvements in outreach services to make VCT more convenient for key affected populations. PMID:26069165

  20. [Comparative chromosomal analysis of populations of phytophilous chironomidae Glyptotendipes glaucus (Mg.) from Chernobyl-affected territory].

    PubMed

    Belianina, S I

    2014-09-01

    The karyopools of the phytophilous chiromomid species of Glyptotendipes glaucus (Mg.) were studied. Chironomids originated from a number of reservoirs located in the Novozybkovsky rayon of the Bryansk region, which was affected by the Chernobyl radioactive release, and two reservoirs located in the Saratov region. Differences in the inversion spectrum and frequencies, both among Bryansk and between Bryansk and Saratov populations, were found. There were no new inversions in the Novozybkovsky populations; however, structurally small rearrangements in long chromosomes were noted. Typical abnormalities included mosaicism of the chromosome morphotypes in cells of the same saline gland, which was especially distinctive in the larvae from the forbidden zone; decondensation of the telomere regions of chromosomes; and mosaic asynapsis of the chromosome IV homologs (up to complete disjunction). Also, several larvae were polyploids. Other species of Glyptotendipes inhabiting the Novozybkovsky reservoirs were represented by the single species of G. paripes (near the Korchy settlement). The karyotypes of its several larvae were represented by an unorganized chromosomal substance. The other Glyptotendipes species seem to have lower adaptive abilities under the conditions in question and were eliminated from precatastrophe biotopes, while G. glaucus succeeded in adaptating to the new environment. PMID:25735132

  1. Data Driven Approach for High Resolution Population Distribution and Dynamics Models

    SciTech Connect

    Bhaduri, Budhendra L; Bright, Eddie A; Rose, Amy N; Liu, Cheng; Urban, Marie L; Stewart, Robert N

    2014-01-01

    High resolution population distribution data are vital for successfully addressing critical issues ranging from energy and socio-environmental research to public health to human security. Commonly available population data from Census is constrained both in space and time and does not capture population dynamics as functions of space and time. This imposes a significant limitation on the fidelity of event-based simulation models with sensitive space-time resolution. This paper describes ongoing development of high-resolution population distribution and dynamics models, at Oak Ridge National Laboratory, through spatial data integration and modeling with behavioral or activity-based mobility datasets for representing temporal dynamics of population. The model is resolved at 1 km resolution globally and describes the U.S. population for nighttime and daytime at 90m. Integration of such population data provides the opportunity to develop simulations and applications in critical infrastructure management from local to global scales.

  2. High population variability and source-sink dynamics in a solitary bee species.

    PubMed

    Franzén, Markus; Nilsson, Sven G

    2013-06-01

    Although solitary bees are considered to play key roles in ecosystem functions, surprisingly few studies have explored their population dynamics. We investigated the population dynamics of a rare, declining, solitary bee (Andrena humilis) in a landscape of 80 km2 in southern Sweden from 2003 to 2011. Only one population was persistent throughout all years studied; most likely this population supplied the surrounding landscape with 11 smaller, temporary local populations. Despite stable pollen availability, the size of the persistent population fluctuated dramatically in a two-year cycle over the nine years, with 490-1230 nests in odd-numbered years and 21-48 nests in even-numbered years. These fluctuations were not significantly related to climatic variables or pollen availability. Nineteen colonization and 14 extinction events were recorded. Occupancy decreased with distance from the persistent population and increased with increasing resource (pollen) availability. There were significant positive correlations between the size of the persistent population and patch occupancy and colonization. Colonizations were generally more common in patches closer to the persistent population, whereas extinctions were independent of distance from the persistent population. Our results highlight the complex population dynamics that exist for this solitary bee species, which could be due to source-sink dynamics, a prolonged diapause, or can represent a bet-hedging strategy to avoid natural enemies and survive in small habitat patches. If large fluctuations in solitary bee populations prove to be widespread, it will have important implications for interpreting ecological relationships, bee conservation, and pollination. PMID:23923503

  3. Population dynamics of the estuarine isopod Sphaeroma rugicauda

    NASA Astrophysics Data System (ADS)

    Heath, David J.; Khazaeli, Aziz A.

    1985-01-01

    Population density, spatial distribution, size distribution, sex ratio and fecundity were studied in a population over a three-year period. Young are produced in the summer, overwinter, reproduce and then die. Population densities decrease due to mortality from March to June and increase due to natality from July to September. Climate has a significant effect on population density. An abnormally warm summer (1976) led to earlier breeding, reduced fecundity, faster growth and higher mortality of juveniles. This led to fewer, larger, breeding adults in 1977. Two years which were climatically similar showed similar population trends. Egg and offspring number were positively correlated with female size but differed between years. Brood pouch mortality was estimated at 17%. Marked changes in population sex ratio were shown to be artefacts due to differences in swimming activity of the sexes.

  4. Intraspecific Competition and Population Dynamics of Aedes aegypti

    NASA Astrophysics Data System (ADS)

    Paixão, C. A.; Charret, I. C.; Lima, R. R.

    2012-04-01

    We report computational simulations for the evolution of the population of the dengue vector, Aedes aegypti mosquitoes. The results suggest that controlling the mosquito population, on the basis of intraspecific competition at the larval stage, can be an efficient mechanism for controlling the spread of the epidemic. The results also show the presence of a kind of genetic evolution in vector population, which results mainly in increasing the average lifespan of individuals in adulthood.

  5. Dynamics of single-species population growth: stability or chaos

    SciTech Connect

    Mueller, L.D.; Ayala, F.J.

    1981-01-01

    We have examined stability at the carrying capacity for 25 genetically different populations of Drosophila melanogaster. In spite of their genetic heterogeneity, 20 of the populations yield stable equilibria and none have eigenvalues significantly greater than one. Computer simulations demonstrate how selection at the individual level may account for population stability (and, hence, that group selection is not necessary for the evolution of stability). Recent theoretical studies on density-dependent selection in random environments provide predictions consistent with our empirical findings.

  6. Soil microbes and plant invasions—how soil-borne pathogens regulate plant populations and affect plant invasions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Exotic plant invaders are a major global threat to biodiversity and ecosystem function. Here I present multiple lines of evidence suggesting that soil microbial communities affect the population growth rates of Prunus serotina in its native range and affect its invasiveness abroad. Research often ...

  7. Spatial variation in water loss predicts terrestrial salamander distribution and population dynamics.

    PubMed

    Peterman, W E; Semlitsch, R D

    2014-10-01

    Many patterns observed in ecology, such as species richness, life history variation, habitat use, and distribution, have physiological underpinnings. For many ectothermic organisms, temperature relationships shape these patterns, but for terrestrial amphibians, water balance may supersede temperature as the most critical physiologically limiting factor. Many amphibian species have little resistance to water loss, which restricts them to moist microhabitats, and may significantly affect foraging, dispersal, and courtship. Using plaster models as surrogates for terrestrial plethodontid salamanders (Plethodon albagula), we measured water loss under ecologically relevant field conditions to estimate the duration of surface activity time across the landscape. Surface activity time was significantly affected by topography, solar exposure, canopy cover, maximum air temperature, and time since rain. Spatially, surface activity times were highest in ravine habitats and lowest on ridges. Surface activity time was a significant predictor of salamander abundance, as well as a predictor of successful recruitment; the probability of a juvenile salamander occupying an area with high surface activity time was two times greater than an area with limited predicted surface activity. Our results suggest that survival, recruitment, or both are demographic processes that are affected by water loss and the ability of salamanders to be surface-active. Results from our study extend our understanding of plethodontid salamander ecology, emphasize the limitations imposed by their unique physiology, and highlight the importance of water loss to spatial population dynamics. These findings are timely for understanding the effects that fluctuating temperature and moisture conditions predicted for future climates will have on plethodontid salamanders. PMID:25154754

  8. A BASIC Program for Use in Teaching Population Dynamics.

    ERIC Educational Resources Information Center

    Kidd, N. A. C.

    1984-01-01

    Describes an interactive simulation model which can be used to demonstrate population growth with discrete or overlapping populations and the effects of random, constant, or density-dependent mortality. The program listing (for Commodore PET 4032 microcomputer) is included. (Author/DH)

  9. Historical and anthropogenic factors affecting the population genetic structure of Ontario's inland lake populations of Walleye (Sander vitreus).

    PubMed

    Walter, Ryan P; Cena, Christopher J; Morgan, George E; Heath, Daniel D

    2012-01-01

    Populations existing in formerly glaciated areas often display composite historical and contemporary patterns of genetic structure. For Canadian freshwater fishes, population genetic structure is largely reflective of dispersal from glacial refugia and isolation within drainage basins across a range of scales. Enhancement of sport fisheries via hatchery stocking programs and other means has the potential to alter signatures of natural evolutionary processes. Using 11 microsatellite loci genotyped from 2182 individuals, we analyzed the genetic structure of 46 inland lake walleye (Sander vitreus) populations spanning five major drainage basins within the province of Ontario, Canada. Population genetic analyses coupled with genotype assignment allowed us to: 1) characterize broad- and fine-scale genetic structure among Ontario walleye populations; and 2) determine if the observed population divergence is primarily due to natural or historical processes, or recent anthropogenic events. The partitioning of genetic variation revealed higher genetic divergence among lakes than among drainage basins or proposed ancestries-indicative of relatively high isolation among lakes, study-wide. Walleye genotypes were clustered into three major groups, likely reflective of Missourian, Mississippian, and Atlantic glacial refugial ancestry. Despite detectable genetic signatures indicative of anthropogenic influences, province-wide spatial genetic structure remains consistent with the hypothesis of dispersal from distinct glacial refugia and subsequent isolation of lakes within primary drainage basins. Our results provide a novel example of minimal impacts from fishery enhancement to the broad-scale genetic structure of inland fish populations. PMID:23125407

  10. Influence of food availability on demography and local population dynamics in a long-lived seabird.

    PubMed Central

    Oro, Daniel; Cam, Emmanuelle; Pradel, Roger; Martínez-Abraín, Alejandro

    2004-01-01

    Few studies have addressed the effects of food availability as a proximate factor affecting local adult survival in long-lived organisms and their consequences at local population dynamics. We used capture-recapture analysis of resightings of 10 birth cohorts of ringed Audouin's gulls, Larus audouinii, to estimate adult survival and dispersal (both emigration and immigration). For the first time, permanent emigration (the transient effect in capture-recapture analysis) was modelled for the whole population and not only for the newly marked birds. Gulls exploit to a large extent fishes discarded from trawlers, and a trawling moratorium established since 1991 has decreased food supply for the colony. This was used as a natural experiment of food availability to assess its effects on adult survival and emigration. These and other demographic parameters were used in a projection modelling to assess the probabilities of extinction of the colony under two scenarios of lower and higher food availability. Food availability (together with the age of individuals) influenced emigration probabilities, but not adult survival, which was estimated at 0.91 (s.e. = 0.02). When food was in shorter supply during the chick-rearing period, emigration was very high (ca. 65%) for younger breeders, although this rate decreased sharply with age. Probabilities of extinction were very high when food availability was low, and when environmental stochasticity was introduced, and only stochastic immigration from the outside seemed to prevent extinction. The results highlight the importance of dispersal processes in the population dynamics of long-lived organisms. PMID:15101698

  11. Hydrologic Variability Governs Population Dynamics of a Vulnerable Amphibian in an Arid Environment

    PubMed Central

    Zylstra, Erin R.; Steidl, Robert J.; Swann, Don E.; Ratzlaff, Kristina

    2015-01-01

    Dynamics of many amphibian populations are governed by the distribution and availability of water. Therefore, understanding the hydrological mechanisms that explain spatial and temporal variation in occupancy and abundance will improve our ability to conserve and recover populations of vulnerable amphibians. We used 16 years of survey data from intermittent mountain streams in the Sonoran Desert to evaluate how availability of surface water affected survival and adult recruitment of a threatened amphibian, the lowland leopard frog (Lithobates yavapaiensis). Across the entire study period, monthly survival of adults ranged from 0.72 to 0.99 during summer and 0.59 to 0.94 during winter and increased with availability of surface water (Z = 7.66; P < 0.01). Recruitment of frogs into the adult age class occurred primarily during winter and ranged from 1.9 to 3.8 individuals/season/pool; like survival, recruitment increased with availability of surface water (Z = 3.67; P < 0.01). Although abundance of frogs varied across seasons and years, we found no evidence of a systematic trend during the 16-year study period. Given the strong influence of surface water on population dynamics of leopard frogs, conservation of many riparian obligates in this and similar arid regions likely depends critically on minimizing threats to structures and ecosystem processes that maintain surface waters. Understanding the influence of surface-water availability on riparian organisms is particularly important because climate change is likely to decrease precipitation and increase ambient temperatures in desert riparian systems, both of which have the potential to alter fundamentally the hydrology of these systems. PMID:26030825

  12. Hydrologic variability governs population dynamics of a vulnerable amphibian in an arid environment.

    PubMed

    Zylstra, Erin R; Steidl, Robert J; Swann, Don E; Ratzlaff, Kristina

    2015-01-01

    Dynamics of many amphibian populations are governed by the distribution and availability of water. Therefore, understanding the hydrological mechanisms that explain spatial and temporal variation in occupancy and abundance will improve our ability to conserve and recover populations of vulnerable amphibians. We used 16 years of survey data from intermittent mountain streams in the Sonoran Desert to evaluate how availability of surface water affected survival and adult recruitment of a threatened amphibian, the lowland leopard frog (Lithobates yavapaiensis). Across the entire study period, monthly survival of adults ranged from 0.72 to 0.99 during summer and 0.59 to 0.94 during winter and increased with availability of surface water (Z = 7.66; P < 0.01). Recruitment of frogs into the adult age class occurred primarily during winter and ranged from 1.9 to 3.8 individuals/season/pool; like survival, recruitment increased with availability of surface water (Z = 3.67; P < 0.01). Although abundance of frogs varied across seasons and years, we found no evidence of a systematic trend during the 16-year study period. Given the strong influence of surface water on population dynamics of leopard frogs, conservation of many riparian obligates in this and similar arid regions likely depends critically on minimizing threats to structures and ecosystem processes that maintain surface waters. Understanding the influence of surface-water availability on riparian organisms is particularly important because climate change is likely to decrease precipitation and increase ambient temperatures in desert riparian systems, both of which have the potential to alter fundamentally the hydrology of these systems. PMID:26030825

  13. Herbivory affects salt marsh succession dynamics by suppressing the recovery of dominant species.

    PubMed

    Daleo, Pedro; Alberti, Juan; Pascual, Jesús; Canepuccia, Alejandro; Iribarne, Oscar

    2014-05-01

    Disturbance can generate heterogeneous environments and profoundly influence plant diversity by creating patches at different successional stages. Herbivores, in turn, can govern plant succession dynamics by determining the rate of species replacement, ultimately affecting plant community structure. In a south-western Atlantic salt marsh, we experimentally evaluated the role of herbivory in the recovery following disturbance of the plant community and assessed whether herbivory affects the relative importance of sexual and clonal reproduction on these dynamics. Our results show that herbivory strongly affects salt marsh secondary succession by suppressing seedlings and limiting clonal colonization of the dominant marsh grass, allowing subordinate species to dominate disturbed patches. These results demonstrate that herbivores can have an important role in salt marsh community structure and function, and can be a key force during succession dynamics. PMID:24549938

  14. q-deformations and the dynamics of the larch bud-moth population cycles

    NASA Astrophysics Data System (ADS)

    Iyengar, Sudharsana V.; Balakrishnan, J.

    2014-07-01

    The concept of q-deformation of numbers is applied here to improve and modify a tritrophic population dynamics model to understand defoliation of the coniferous larch trees due to outbreaks of the larch bud-moth insect population. The results are in qualitative agreement with observed behavior, with the larch needle lengths, bud-moth population and parasitoid populations all showing 9-period cycles which are mutually synchronized.

  15. Age and Gender Affect the Composition of Fungal Population of the Human Gastrointestinal Tract.

    PubMed

    Strati, Francesco; Di Paola, Monica; Stefanini, Irene; Albanese, Davide; Rizzetto, Lisa; Lionetti, Paolo; Calabrò, Antonio; Jousson, Olivier; Donati, Claudio; Cavalieri, Duccio; De Filippo, Carlotta

    2016-01-01

    The fungal component of the human gut microbiota has been neglected for long time due to the low relative abundance of fungi with respect to bacteria, and only recently few reports have explored its composition and dynamics in health or disease. The application of metagenomics methods to the full understanding of fungal communities is currently limited by the under representation of fungal DNA with respect to the bacterial one, as well as by the limited ability to discriminate passengers from colonizers. Here, we investigated the gut mycobiota of a cohort of healthy subjects in order to reduce the gap of knowledge concerning fungal intestinal communities in the healthy status further screening for phenotypical traits that could reflect fungi adaptation to the host. We studied the fecal fungal populations of 111 healthy subjects by means of cultivation on fungal selective media and by amplicon-based ITS1 metagenomics analysis on a subset of 57 individuals. We then characterized the isolated fungi for their tolerance to gastrointestinal (GI) tract-like challenges and their susceptibility to antifungals. A total of 34 different fungal species were isolated showing several phenotypic characteristics associated with intestinal environment such as tolerance to body temperature (37°C), to acidic and oxidative stress, and to bile salts exposure. We found a high frequency of azoles resistance in fungal isolates, with potential and significant clinical impact. Analyses of fungal communities revealed that the human gut mycobiota differs in function of individuals' life stage in a gender-related fashion. The combination of metagenomics and fungal cultivation allowed an in-depth understanding of the fungal intestinal community structure associated to the healthy status and the commensalism-related traits of isolated fungi. We further discussed comparatively the results of sequencing and cultivation to critically evaluate the application of metagenomics-based approaches to

  16. Age and Gender Affect the Composition of Fungal Population of the Human Gastrointestinal Tract

    PubMed Central

    Strati, Francesco; Di Paola, Monica; Stefanini, Irene; Albanese, Davide; Rizzetto, Lisa; Lionetti, Paolo; Calabrò, Antonio; Jousson, Olivier; Donati, Claudio; Cavalieri, Duccio; De Filippo, Carlotta

    2016-01-01

    The fungal component of the human gut microbiota has been neglected for long time due to the low relative abundance of fungi with respect to bacteria, and only recently few reports have explored its composition and dynamics in health or disease. The application of metagenomics methods to the full understanding of fungal communities is currently limited by the under representation of fungal DNA with respect to the bacterial one, as well as by the limited ability to discriminate passengers from colonizers. Here, we investigated the gut mycobiota of a cohort of healthy subjects in order to reduce the gap of knowledge concerning fungal intestinal communities in the healthy status further screening for phenotypical traits that could reflect fungi adaptation to the host. We studied the fecal fungal populations of 111 healthy subjects by means of cultivation on fungal selective media and by amplicon-based ITS1 metagenomics analysis on a subset of 57 individuals. We then characterized the isolated fungi for their tolerance to gastrointestinal (GI) tract-like challenges and their susceptibility to antifungals. A total of 34 different fungal species were isolated showing several phenotypic characteristics associated with intestinal environment such as tolerance to body temperature (37°C), to acidic and oxidative stress, and to bile salts exposure. We found a high frequency of azoles resistance in fungal isolates, with potential and significant clinical impact. Analyses of fungal communities revealed that the human gut mycobiota differs in function of individuals' life stage in a gender-related fashion. The combination of metagenomics and fungal cultivation allowed an in-depth understanding of the fungal intestinal community structure associated to the healthy status and the commensalism-related traits of isolated fungi. We further discussed comparatively the results of sequencing and cultivation to critically evaluate the application of metagenomics-based approaches to

  17. Population dynamics of a natural red deer population over 200 years detected via substantial changes of genetic variation.

    PubMed

    Hoffmann, Gunther Sebastian; Johannesen, Jes; Griebeler, Eva Maria

    2016-05-01

    Most large mammals have constantly been exposed to anthropogenic influence over decades or even centuries. Because of their long generation times and lack of sampling material, inferences of past population genetic dynamics, including anthropogenic impacts, have only relied on the analysis of the structure of extant populations. Here, we investigate for the first time the change in the genetic constitution of a natural red deer population over two centuries, using up to 200-year-old antlers (30 generations) stored in trophy collections. To the best of our knowledge, this is the oldest DNA source ever used for microsatellite population genetic analyses. We demonstrate that government policy and hunting laws may have strong impacts on populations that can lead to unexpectedly rapid changes in the genetic constitution of a large mammal population. A high ancestral individual polymorphism seen in an outbreeding population (1813-1861) was strongly reduced in descendants (1923-1940) during the mid-19th and early 20th century by genetic bottlenecks. Today (2011), individual polymorphism and variance among individuals is increasing in a constant-sized (managed) population. Differentiation was high among periods (F ST > ***); consequently, assignment tests assigned individuals to their own period with >85% probability. In contrast to the high variance observed at nuclear microsatellite loci, mtDNA (D-loop) was monomorphic through time, suggesting that male immigration dominates the genetic evolution in this population. PMID:27096075

  18. Population dynamics and angler exploitation of the unique muskellunge population in Shoepack Lake, Voyageurs National Park, Minnesota

    USGS Publications Warehouse

    Frohnauer, N.K.; Pierce, C.L.; Kallemeyn, L.W.

    2007-01-01

    A unique population of muskellunge Esox masquinongy inhabits Shoepack Lake in Voyageurs National Park, Minnesota. Little is known about its status, dynamics, and angler exploitation, and there is concern for the long-term viability of this population. We used intensive sampling and mark-recapture methods to quantify abundance, survival, growth, condition, age at maturity and fecundity and angler surveys to quantify angler pressure, catch rates, and exploitation. During our study, heavy rain washed out a dam constructed by beavers Castor canadensis which regulates the water level at the lake outlet, resulting in a nearly 50% reduction in surface area. We estimated a population size of 1,120 adult fish at the beginning of the study. No immediate reduction in population size was detected in response to the loss of lake area, although there was a gradual, but significant, decline in population size over the 2-year study. Adults grew less than 50 mm per year, and relative weight (W r) averaged roughly 80. Anglers were successful in catching, on average, two fish during a full day of angling, but harvest was negligible. Shoepack Lake muskellunge exhibit much slower growth rates and lower condition, but much higher densities and angler catch per unit effort (CPUE), than other muskellunge populations. The unique nature, limited distribution, and location of this population in a national park require special consideration for management. The results of this study provide the basis for assessing the long-term viability of the Shoepack Lake muskellunge population through simulations of long-term population dynamics and genetically effective population size. ?? Copyright by the American Fisheries Society 2007.

  19. Density but not climate affects the population growth rate of guanacos ( Lama guanicoe) (Artiodactyla, Camelidae).

    PubMed

    Zubillaga, María; Skewes, Oscar; Soto, Nicolás; Rabinovich, Jorge E

    2013-01-01

    We analyzed the effects of population density and climatic variables on the rate of population growth in the guanaco ( Lama guanicoe), a wild camelid species in South America. We used a time series of 36 years (1977-2012) of population sampling in Tierra del Fuego, Chile. Individuals were grouped in three age-classes: newborns, juveniles, and adults; for each year a female population transition matrix was constructed, and the population growth rate (λ) was estimated for each year as the matrix highest positive eigenvalue. We applied a regression analysis with finite population growth rate (λ) as dependent variable, and total guanaco population, sheep population, annual mean precipitation, and winter mean temperature as independent variables, with and without time lags. The effect of guanaco population size was statistically significant, but the effects of the sheep population and the climatic variables on guanaco population growth rate were not statistically significant. PMID:25187878

  20. Density but not climate affects the population growth rate of guanacos ( Lama guanicoe) (Artiodactyla, Camelidae)

    PubMed Central

    Zubillaga, María; Skewes, Oscar; Soto, Nicolás; Rabinovich, Jorge E

    2014-01-01

    We analyzed the effects of population density and climatic variables on the rate of population growth in the guanaco ( Lama guanicoe), a wild camelid species in South America. We used a time series of 36 years (1977-2012) of population sampling in Tierra del Fuego, Chile. Individuals were grouped in three age-classes: newborns, juveniles, and adults; for each year a female population transition matrix was constructed, and the population growth rate (λ) was estimated for each year as the matrix highest positive eigenvalue. We applied a regression analysis with finite population growth rate (λ) as dependent variable, and total guanaco population, sheep population, annual mean precipitation, and winter mean temperature as independent variables, with and without time lags. The effect of guanaco population size was statistically significant, but the effects of the sheep population and the climatic variables on guanaco population growth rate were not statistically significant. PMID:25187878

  1. Use of epidemiological data and direct bioassay for prioritization of affected populations in a large-scale radiation emergency.

    PubMed

    Miller, Charles W; Ansari, Armin; Martin, Colleen; Chang, Art; Buzzell, Jennifer; Whitcomb, Robert C

    2011-08-01

    Following a radiation emergency, evacuated, sheltered or other members of the public would require monitoring for external and/or internal contamination and, if indicated, decontamination. In addition, the potentially-impacted population would be identified for biodosimetry/bioassay or needed medical treatment (chelation therapy, cytokine treatment, etc.) and prioritized for follow-up. Expeditious implementation of these activities presents many challenges, especially when a large population is affected. Furthermore, experience from previous radiation incidents has demonstrated that the number of people seeking monitoring for radioactive contamination (both external and internal) could be much higher than the actual number of contaminated individuals. In the United States, the Department of Health and Human Services is the lead agency to coordinate federal support for population monitoring activities. Population monitoring includes (1) monitoring people for external contamination; (2) monitoring people for internal contamination; (3) population decontamination; (4) collecting epidemiologic data regarding potentially exposed and/or contaminated individuals to prioritize the affected population for limited medical resources; (5) administering available pharmaceuticals for internal decontamination as deemed necessary by appropriate health officials; (6) performing dose reconstruction; and (7) establishing a registry to conduct long-term monitoring of this population for potential long-term health effects. This paper will focus on screening for internal contamination and will describe the use of early epidemiologic data as well as direct bioassay techniques to rapidly identify and prioritize the affected population for further analysis and medical attention. PMID:21709510

  2. POPULATION DYNAMICS OF FUNGA, NEMATODE, BACTERIA AND ALGAL POPULATION IN A SOIL OF MAZON REGION OF PERU

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil microbes are mainly responsible for litter decomposition and nutrient cycling in the forest ecosystems. Population dynamics of soil microbes (fungus, bacteria, nematodes, algae) under secondary forest in tropical region is not well understood. An experiment was implemented at Tropical Crop Rese...

  3. [The relationship between population dynamics and the process of development: an interdependence requiring the definition of population policies].

    PubMed

    1989-01-01

    The case of Senegal is used to illustrate the impact of population dynamics on the economic development of a country and the process of creating a population policy. 1 of the 6 principles of the Kilimanjaro Program of Action concerning African population and autonomous development was the interdependence between population and development, but interest in the problem was only sporadic until the deepening of the economic crisis. Population growth is now regarded as a major constraint on improvement of welfare for the population. The population of the Sahel countries has almost doubled in the past 2 decades as a consequence of very high fertility rates and declining mortality rates. About 44% of the Sahel population is under 15 years old and only about 53% is aged 15-64. The population is unequally distributed and the proportion urban increased from 18 to 23% between 1982-85. The general opinion is that the African population is increasing more rapidly than available resources. From 1973-83, Senegal's gross national product increased by 2.2%/year on average, less than the population increase of 2.5%. Cereal production increased by 1%/year between 1973-81. Investments in agriculture have declined continuously since 1973. Cereal needs are on the order of 6.69 million tons, while production is only 4.4 million tons. According to the World Bank the literacy rate for 5 Sahel countries was only 15% in 1982, and only 35% of school aged children are enrolled. The constant increase of population is also putting pressure on health services. In response to these problems, Senegal developed its population policy in 3 phases. In the 1st phase, 3 commissions and a working group carried out research and documentation around the country, producing sectorial documents. In the 2nd phase, workshops and seminars were held for the critical examination of the sectorial documents, culminating in presentation of a synthesis to the National Commission on Population and to the

  4. POPULATION DYNAMICS OF SMALL MAMMALS ACROSS A NITROGEN AMENDED LANDSCAPE

    EPA Science Inventory

    Biogeochemical alterations of the nitrogen cycle from anthropogenic activities could have significant effects on ecological processes at the population, community and ecosystem levels. Nitrogen additions in grasslands have produced qualitative and quantitative changes in vegetat...

  5. Population dynamics of aquatic snails in Pampulha reservoir.

    PubMed

    Freitas, J R; Bedê, L C; De Marco Júnior, P; Rocha, L A; Santos, M B

    1987-01-01

    An attempt was made to determine more accurately the density of molluskan populations in the Pampulha reservoir, using the quadrate method, intending to detect the fluctuation of the populations density, the habitat conditions and the possible competitive interactions among Biomphalaria tenagophila, Melanoides tuberculata, Pomacea haustrum and Biomphalaria glabrata, through the analysis of populational parameters. Among the most significative facts observed in the reservoir it has to be mentioned: the almost disappearance of B. glabrata; the invasion, colonization, fixation and fast growing of M. tuberculata population until reaching about 11,000 individuals/m2; the density fluctuations of B. tenagophila, P. haustrum and M. tuberculata alives and deads; differences on the habitat preference of these three molluskan species at the edge (at the limit earth-water, at 0.70m and 1.40m from the shore line); monthly mortality rates and reproduction seasons of the species. PMID:3509186

  6. Extinction dynamics of a discrete population in an oasis

    NASA Astrophysics Data System (ADS)

    Berti, Stefano; Cencini, Massimo; Vergni, Davide; Vulpiani, Angelo

    2015-07-01

    Understanding the conditions ensuring the persistence of a population is an issue of primary importance in population biology. The first theoretical approach to the problem dates back to the 1950s with the Kierstead, Slobodkin, and Skellam (KiSS) model, namely a continuous reaction-diffusion equation for a population growing on a patch of finite size L surrounded by a deadly environment with infinite mortality, i.e., an oasis in a desert. The main outcome of the model is that only patches above a critical size allow for population persistence. Here we introduce an individual-based analog of the KiSS model to investigate the effects of discreteness and demographic stochasticity. In particular, we study the average time to extinction both above and below the critical patch size of the continuous model and investigate the quasistationary distribution of the number of individuals for patch sizes above the critical threshold.

  7. Causes and consequences of complex population dynamics in an annual plant, Cardamine pensylvanica

    SciTech Connect

    Crone, E.E.

    1995-11-08

    The relative importance of density-dependent and density-independent factors in determining the population dynamics of plants has been widely debated with little resolution. In this thesis, the author explores the effects of density-dependent population regulation on population dynamics in Cardamine pensylvanica, an annual plant. In the first chapter, she shows that experimental populations of C. pensylvanica cycled from high to low density in controlled constant-environment conditions. These cycles could not be explained by external environmental changes or simple models of direct density dependence (N{sub t+1} = f[N{sub t}]), but they could be explained by delayed density dependence (N{sub t+1} = f[N{sub t}, N{sub t+1}]). In the second chapter, she shows that the difference in the stability properties of population growth models with and without delayed density dependence is due to the presence of Hopf as well as slip bifurcations from stable to chaotic population dynamics. She also measures delayed density dependence due to effects of parental density on offspring quality in C. pensylvanica and shows that this is large enough to be the cause of the population dynamics observed in C. pensylvanica. In the third chapter, the author extends her analyses of density-dependent population growth models to include interactions between competing species. In the final chapter, she compares the effects of fixed spatial environmental variation and variation in population size on the evolutionary response of C. pensylvanica populations.

  8. Changing facial affect recognition in schizophrenia: Effects of training on brain dynamics

    PubMed Central

    Popova, Petia; Popov, Tzvetan G.; Wienbruch, Christian; Carolus, Almut M.; Miller, Gregory A.; Rockstroh, Brigitte S.

    2014-01-01

    Deficits in social cognition including facial affect recognition and their detrimental effects on functional outcome are well established in schizophrenia. Structured training can have substantial effects on social cognitive measures including facial affect recognition. Elucidating training effects on cortical mechanisms involved in facial affect recognition may identify causes of dysfunctional facial affect recognition in schizophrenia and foster remediation strategies. In the present study, 57 schizophrenia patients were randomly assigned to (a) computer-based facial affect training that focused on affect discrimination and working memory in 20 daily 1-hour sessions, (b) similarly intense, targeted cognitive training on auditory-verbal discrimination and working memory, or (c) treatment as usual. Neuromagnetic activity was measured before and after training during a dynamic facial affect recognition task (5 s videos showing human faces gradually changing from neutral to fear or to happy expressions). Effects on 10–13 Hz (alpha) power during the transition from neutral to emotional expressions were assessed via MEG based on previous findings that alpha power increase is related to facial affect recognition and is smaller in schizophrenia than in healthy subjects. Targeted affect training improved overt performance on the training tasks. Moreover, alpha power increase during the dynamic facial affect recognition task was larger after affect training than after treatment-as-usual, though similar to that after targeted perceptual–cognitive training, indicating somewhat nonspecific benefits. Alpha power modulation was unrelated to general neuropsychological test performance, which improved in all groups. Results suggest that specific neural processes supporting facial affect recognition, evident in oscillatory phenomena, are modifiable. This should be considered when developing remediation strategies targeting social cognition in schizophrenia. PMID:25379427

  9. Web Intervention for Adolescents Affected by Disaster: Population-Based Randomized Controlled Trial

    PubMed Central

    Ruggiero, Kenneth J.; Price, Matthew; Adams, Zachary; Stauffacher, Kirstin; McCauley, Jenna; Danielson, Carla Kmett; Knapp, Rebecca; Hanson, Rochelle F.; Davidson, Tatiana M.; Amstadter, Ananda B.; Carpenter, Matthew J.; Saunders, Benjamin E.; Kilpatrick, Dean G.; Resnick, Heidi S.

    2015-01-01

    Objective To assess the efficacy of Bounce Back Now (BBN), a modular, web-based intervention for disaster-affected adolescents and their parents. Method A population-based randomized controlled trial used address-based sampling to enroll 2,000 adolescents and parents from communities affected by tornadoes in Joplin, MO, and Alabama. Data collection via baseline and follow-up semi-structured telephone interviews was completed between September 2011 and August 2013. All families were invited to access the BBN study web portal irrespective of mental health status at baseline. Families who accessed the web portal were assigned randomly to 3 groups: (1) BBN, which featured modules for adolescents and parents targeting adolescents’ mental health symptoms; (2) BBN plus additional modules targeting parents’ mental health symptoms; or (3) assessment only. The primary outcomes were adolescent symptoms of posttraumatic stress disorder (PTSD) and depression. Results Nearly 50% of families accessed the web portal. Intent-to-treat analyses revealed time × condition interactions for PTSD symptoms (B=−0.24, SE=0.08, p<.01) and depressive symptoms (B=−0.23, SE=0.09, p<.01). Post-hoc comparisons revealed fewer PTSD and depressive symptoms for adolescents in the experimental vs. control conditions at 12-month follow-up (PTSD: B=−0.36, SE=0.19, p=.06; depressive symptoms: B=−0.42, SE=0.19, p=0.03). A time × condition interaction also was found favoring the BBN vs. BBN + parent self-help condition for PTSD symptoms (B=0.30, SE=0.12, p=.02), but not depressive symptoms (B=0.12, SE=0.12, p=.33). Conclusion Results supported the feasibility and initial efficacy of BBN as a scalable disaster mental health intervention for adolescents. Technology-based solutions have tremendous potential value if found to reduce the mental health burden of disasters. PMID:26299292

  10. Population dynamics of the endangered Cape Sable seaside-sparrow

    USGS Publications Warehouse

    Curnutt, J.L.; Mayer, A.L.; Brooks, T.M.; Manne, L.; Bass, O.L., Jr.; Fleming, D.M.; Philip, Nott M.; Pimm, S.L.

    1998-01-01

    The Cape Sable seaside-sparrow (Ammodramus maritimus mirabilis) has disappeared from its only known breeding areas episodically since its discovery early this century. Systematic surveys across its range in the southern Everglades find the sparrow's range to be fragmented into six subpopulations. The sparrow population decreased by 58% between 1992 and 1995, with the near extinction of the western half of the population and the temporary local extinction of some eastern populations. Other similar grassland sparrows have populations that vary considerably from year to year. Yet the decline in the western subpopulation and the local extinction of some of the peripheral populations cannot be explained by natural variability alone. Hurricane Andrew passed over several subpopulations prior to the particularly poor year of 1993. However, the geographical and temporal patterns of subpopulation decline are not consistent with what would be expected following a hurricane. Frequent fires prevent successful breeding as does flooding during the breeding season. Better management can prevent frequent fires and episodic flooding. However, the long-term survival of the sparrow depends on managing the unanticipated risks that attend its small, fragmented population.

  11. Recombination affects accumulation of damaging and disease-associated mutations in human populations.

    PubMed

    Hussin, Julie G; Hodgkinson, Alan; Idaghdour, Youssef; Grenier, Jean-Christophe; Goulet, Jean-Philippe; Gbeha, Elias; Hip-Ki, Elodie; Awadalla, Philip

    2015-04-01

    Many decades of theory have demonstrated that, in non-recombining systems, slightly deleterious mutations accumulate non-reversibly, potentially driving the extinction of many asexual species. Non-recombining chromosomes in sexual organisms are thought to have degenerated in a similar fashion; however, it is not clear the extent to which damaging mutations accumulate along chromosomes with highly variable rates of crossing over. Using high-coverage sequencing data from over 1,400 individuals in the 1000 Genomes and CARTaGENE projects, we show that recombination rate modulates the distribution of putatively deleterious variants across the entire human genome. Exons in regions of low recombination are significantly enriched for deleterious and disease-associated variants, a signature varying in strength across worldwide human populations with different demographic histories. Regions with low recombination rates are enriched for highly conserved genes with essential cellular functions and show an excess of mutations with demonstrated effects on health, a phenomenon likely affecting disease susceptibility in humans. PMID:25685891

  12. The burden of acute respiratory infections in crisis-affected populations: a systematic review

    PubMed Central

    2010-01-01

    Crises due to armed conflict, forced displacement and natural disasters result in excess morbidity and mortality due to infectious diseases. Historically, acute respiratory infections (ARIs) have received relatively little attention in the humanitarian sector. We performed a systematic review to generate evidence on the burden of ARI in crises, and inform prioritisation of relief interventions. We identified 36 studies published since 1980 reporting data on the burden (incidence, prevalence, proportional morbidity or mortality, case-fatality, attributable mortality rate) of ARI, as defined by the International Classification of Diseases, version 10 and as diagnosed by a clinician, in populations who at the time of the study were affected by natural disasters, armed conflict, forced displacement, and nutritional emergencies. We described studies and stratified data by age group, but did not do pooled analyses due to heterogeneity in case definitions. The published evidence, mainly from refugee camps and surveillance or patient record review studies, suggests very high excess morbidity and mortality (20-35% proportional mortality) and case-fatality (up to 30-35%) due to ARI. However, ARI disease burden comparisons with non-crisis settings are difficult because of non-comparability of data. Better epidemiological studies with clearer case definitions are needed to provide the evidence base for priority setting and programme impact assessments. Humanitarian agencies should include ARI prevention and control among infants, children and adults as priority activities in crises. Improved data collection, case management and vaccine strategies will help to reduce disease burden. PMID:20181220

  13. Both population size and patch quality affect local extinctions and colonizations.

    PubMed

    Franzén, Markus; Nilsson, Sven G

    2010-01-01

    Currently, the habitat of many species is fragmented, resulting in small local populations with individuals occasionally dispersing between the remaining habitat patches. In a solitary bee metapopulation, extinction probability was related to both local bee population sizes and pollen resources measured as host plant population size. Patch size, on the other hand, had no additional predictive power. The turnover rate of local bee populations in 63 habitat patches over 4 years was high, with 72 extinction events and 31 colonization events, but the pollen plant population was stable with no extinctions or colonizations. Both pollen resources and bee populations had strong and independent effects on extinction probability, but connectivity was not of importance. Colonizations occurred more frequently within larger host plant populations. For metapopulation survival of the bee, large pollen plant populations are essential, independent of current bee population size. PMID:19793747

  14. A dynamic urban air pollution population exposure assessment study using model and population density data derived by mobile phone traffic

    NASA Astrophysics Data System (ADS)

    Gariazzo, Claudio; Pelliccioni, Armando; Bolignano, Andrea

    2016-04-01

    A dynamic city-wide air pollution exposure assessment study has been carried out for the urban population of Rome, Italy, by using time resolved population distribution maps, derived by mobile phone traffic data, and modelled air pollutants (NO2, O3 and PM2.5) concentrations obtained by an integrated air dispersion modelling system. More than a million of persons were tracked during two months (March and April 2015) for their position within the city and its surroundings areas, with a time resolution of 15 min and mapped over an irregular grid system with a minimum resolution of 0.26 × 0.34 Km2. In addition, demographics information (as gender and age ranges) were available in a separated dataset not connected with the total population one. Such BigData were matched in time and space with air pollution model results and then used to produce hourly and daily resolved cumulative population exposures during the studied period. A significant mobility of population was identified with higher population densities in downtown areas during daytime increasing of up to 1000 people/Km2 with respect to nigh-time one, likely produced by commuters, tourists and working age population. Strong variability (up to ±50% for NO2) of population exposures were detected as an effect of both mobility and time/spatial changing in pollutants concentrations. A comparison with the correspondent stationary approach based on National Census data, allows detecting the inability of latter in estimating the actual variability of population exposure. Significant underestimations of the amount of population exposed to daily PM2.5 WHO guideline was identified for the Census approach. Very small differences (up to a few μg/m3) on exposure were detected for gender and age ranges population classes.

  15. Population dynamics of pond zooplankton II Daphnia ambigua Scourfield

    USGS Publications Warehouse

    Angino, E.E.; Armitage, K.B.; Saxena, B.

    1973-01-01

    Calcium was the most important of 27 environmental components affecting density for a 50 week period. Simultaneous stepwise regression accounted for more variability in total number/1 and in the number of ovigerous females/1 than did any of the lag analyses; 1-week lag accounted for the greatest amount of variability in clutch size. Total number and clutch size were little affected by measures of food. ?? 1973 Dr. W. Junk b.v. Publishers.

  16. An overview of the population dynamics in Malaysia.

    PubMed

    Arshat, H; Tey Nai Peng

    1988-06-01

    Between 1900 and 1985 the population of Malaysia has increased from 2 million to 16 million. Before World War II most of the growth was due to immigration from China and India; after World War II it was due to natural increase. The crude birth rate appears to be leveling off at about 31.3 and the crude death rate at 5.3. At the current rate of growth the total population will be about 32 million by 2015. The proportion of urban population increased from 27% in 1979 to 34% in 1980. In 1980 83% of the population lived in Peninsular Malaysia (39% of the land area), and 17% lived in Sabah and Sarawak (61% of the land area). Population density ranges from 12 persons per square kilometer in Sarawak to 4521 in the Federal Republic of Kuala Lumpur. The median age of the population is 17.4 years; 40% are under 14, and 3.6% are over 65. In most age groups there are more women than men. The annual growth rate for Malays is higher than for Chinese and Indians, and Malays constituted 55% of the population in 1980. 34% are Chinese and 10% are Indian. Total fertility rate declined from 68/1000 in 1957 to 39/1000 in 1985. Malay fertility (4.8 children) is higher than either Indian (2.9) or Chinese (2.7) Malay fertility has been increasing while that of Indians and Chinese is decreasing due to contraception. Also, among all 3 groups age at marriage has increased. Data from the 1984/85 Malaysian Population and Family Survey show that the differential fertility of the 3 groups is due largely to rural/urban distribution, education, and work patterns. Ideal family size, according to the survey, is 4.8. The National Population and Family Development Program would like to achieve a growth rate of 2%/year, and family planning knowledge has become virtually universal. KAP surveys show that by 1984 contraceptive prevalence was 51%; however 42% of all eligible women were using unreliable methods. In terms of efficient methods, contraceptive prevalence rate was 16% for Malays, 47% for Chinese

  17. Universality in exact quantum state population dynamics and control

    SciTech Connect

    Wu, Lian-Ao; Segal, Dvira; Brumer, Paul; Egusquiza, Inigo L.

    2010-09-15

    We consider an exact population transition, defined as the probability of finding a state at a final time that is exactly equal to the probability of another state at the initial time. We prove that, given a Hamiltonian, there always exists a complete set of orthogonal states that can be employed as time-zero states for which this exact population transition occurs. The result is general: It holds for arbitrary systems, arbitrary pairs of initial and final states, and for any time interval. The proposition is illustrated with several analytic models. In particular, we demonstrate that in some cases, by tuning the control parameters, a complete transition might occur, where a target state, vacant at t=0, is fully populated at time {tau}.

  18. Time series analysis of fine particulate matter and asthma reliever dispensations in populations affected by forest fires

    PubMed Central

    2013-01-01

    Background Several studies have evaluated the association between forest fire smoke and acute exacerbations of respiratory diseases, but few have examined effects on pharmaceutical dispensations. We examine the associations between daily fine particulate matter (PM2.5) and pharmaceutical dispensations for salbutamol in forest fire-affected and non-fire-affected populations in British Columbia (BC), Canada. Methods We estimated PM2.5 exposure for populations in administrative health areas using measurements from central monitors. Remote sensing data on fires were used to classify the populations as fire-affected or non-fire-affected, and to identify extreme fire days. Daily counts of salbutamol dispensations between 2003 and 2010 were extracted from the BC PharmaNet database. We estimated rate ratios (RR) and 95% confidence intervals (CIs) for each population during all fire seasons and on extreme fire days, adjusted for temperature, humidity, and temporal trends. Overall effects for fire-affected and non-fire-affected populations were estimated via meta-regression. Results Fire season PM2.5 was positively associated with salbutamol dispensations in all fire-affected populations, with a meta-regression RR (95% CI) of 1.06 (1.04-1.07) for a 10 ug/m3 increase. Fire season PM2.5 was not significantly associated with salbutamol dispensations in non-fire-affected populations, with a meta-regression RR of 1.00 (0.98-1.01). On extreme fire days PM2.5 was positively associated with salbutamol dispensations in both population types, with a global meta-regression RR of 1.07 (1.04 - 1.09). Conclusions Salbutamol dispensations were clearly associated with fire-related PM2.5. Significant associations were observed in smaller populations (range: 8,000 to 170,000 persons, median: 26,000) than those reported previously, suggesting that salbutamol dispensations may be a valuable outcome for public health surveillance during fire events. PMID:23356966

  19. Population dynamics and range expansion in nine-banded armadillos.

    PubMed

    Loughry, William J; Perez-Heydrich, Carolina; McDonough, Colleen M; Oli, Madan K

    2013-01-01

    Understanding why certain species can successfully colonize new areas while others do not is a central question in ecology. The nine-banded armadillo (Dasypus novemcinctus) is a conspicuous example of a successful invader, having colonized much of the southern United States in the last 200 years. We used 15 years (1992-2006) of capture-mark-recapture data from a population of armadillos in northern Florida in order to estimate, and examine relationships among, various demographic parameters that may have contributed to this ongoing range expansion. Modeling across a range of values for γ, the probability of juveniles surviving in the population until first capture, we found that population growth rates varied from 0.80 for γ = 0.1, to 1.03 for γ = 1.0. Growth rates approached 1.0 only when γ ≥ 0.80, a situation that might not occur commonly because of the high rate of disappearance of juveniles. Net reproductive rate increased linearly with γ, but life expectancy (estimated at 3 years) was independent of γ. We also found that growth rates were lower during a 3-year period of hardwood removal that removed preferred habitat than in the years preceding or following. Life-table response experiment (LTRE) analysis indicated the decrease in growth rate during logging was primarily due to changes in survival rates of adults. Likewise, elasticity analyses of both deterministic and stochastic population growth rates revealed that survival parameters were more influential on population growth than were those related to reproduction. Collectively, our results are consistent with recent theories regarding biological invasions which posit that populations no longer at the leading edge of range expansion do not exhibit strong positive growth rates, and that high reproductive output is less critical in predicting the likelihood of successful invasion than are life-history strategies that emphasize allocation of resources to future, as opposed to current, reproduction

  20. Population Dynamics and Range Expansion in Nine-Banded Armadillos

    PubMed Central

    Loughry, William J.; Perez-Heydrich, Carolina; McDonough, Colleen M.; Oli, Madan K.

    2013-01-01

    Understanding why certain species can successfully colonize new areas while others do not is a central question in ecology. The nine-banded armadillo (Dasypus novemcinctus) is a conspicuous example of a successful invader, having colonized much of the southern United States in the last 200 years. We used 15 years (1992–2006) of capture-mark-recapture data from a population of armadillos in northern Florida in order to estimate, and examine relationships among, various demographic parameters that may have contributed to this ongoing range expansion. Modeling across a range of values for γ, the probability of juveniles surviving in the population until first capture, we found that population growth rates varied from 0.80 for γ = 0.1, to 1.03 for γ = 1.0. Growth rates approached 1.0 only when γ ≥0.80, a situation that might not occur commonly because of the high rate of disappearance of juveniles. Net reproductive rate increased linearly with γ, but life expectancy (estimated at 3 years) was independent of γ. We also found that growth rates were lower during a 3-year period of hardwood removal that removed preferred habitat than in the years preceding or following. Life-table response experiment (LTRE) analysis indicated the decrease in growth rate during logging was primarily due to changes in survival rates of adults. Likewise, elasticity analyses of both deterministic and stochastic population growth rates revealed that survival parameters were more influential on population growth than were those related to reproduction. Collectively, our results are consistent with recent theories regarding biological invasions which posit that populations no longer at the leading edge of range expansion do not exhibit strong positive growth rates, and that high reproductive output is less critical in predicting the likelihood of successful invasion than are life-history strategies that emphasize allocation of resources to future, as opposed to current

  1. A Quantative Adverse Outcome Pathway Linking Aromatase Inhibition in Fathead Minnows with Population Dynamics

    EPA Science Inventory

    A Quantitative Adverse Outcome Pathway Linking Aromatase Inhibition in Fathead Minnows with Population DynamicsAn adverse outcome pathway (AOP) is a qualitative description linking a molecular initiating event (MIE) with measureable key events leading to an adverse outcome (AO). ...

  2. Population dynamics of flaviviruses revealed by molecular phylogenies.

    PubMed Central

    Zanotto, P M; Gould, E A; Gao, G F; Harvey, P H; Holmes, E C

    1996-01-01

    The phylogeny of 123 complete envelope gene sequences was reconstructed in order to understand the evolution of tick- and mosquito-borne flaviviruses. An analysis of phylogenetic tree structure reveals a continual and asymmetric branching process in the tick-borne flaviviruses, compared with an explosive radiation in the last 200 years in viruses transmitted by mosquitoes. The distinction between these two viral groups probably reflects differences in modes of dispersal, propagation, and changes in the size of host populations. The most serious implication of this work is that growing human populations are being exposed to an expanding range of increasingly diverse viral strains. PMID:8570593

  3. Influence of climatic variability on local population dynamics of a Sonoran Desert platyopuntia

    USGS Publications Warehouse

    Bowers, Janice E.

    2005-01-01

    Age-based population dynamics of Opuntia engelmannii, a shrubby cactus with flattened cladodes, were investigated at a Sonoran Desert site protected from grazing since 1907. Demographic statistics were determined from births and deaths on six permanent vegetation plots mapped four times between 1968 and 2001. Moderate longevity (13-56 years) and modest per capita annual survival (0.9298) were associated with fairly rapid turnover; cycles of population growth and decline were thus evident over relatively short periods. Age-frequency distribution, determined for subpopulations in two neighboring habitats in 1996 and 2003, was used to calculate residual regeneration, an index of the difference between observed cohort size and idealized survivorship. Establishment peaks occurred in the late 1970s, the mid-1980s, and the early to mid-1990s and coincided with increased winter moisture in the years before germination, ample summer rain in the year of germination, and decreased drought in the years after germination, reflecting favorable conditions for fruit production, seed germination, and seedling survival. Regionally, pulses and gaps in establishment coincide with the frequency and amplitude of large-scale climatic phenomena that affect cycles of moisture and drought on decadal and interdecadal scales. Because of local factors, however, subpopulations within a few km of one another can experience virtually identical climates yet differ strikingly in age structure and density. ?? 2004 Elsevier Ltd. All rights reserved.

  4. Transmission or Within-Host Dynamics Driving Pulses of Zoonotic Viruses in Reservoir–Host Populations

    PubMed Central

    Plowright, Raina K.; Peel, Alison J.; Streicker, Daniel G.; Gilbert, Amy T.; McCallum, Hamish; Wood, James; Baker, Michelle L.; Restif, Olivier

    2016-01-01

    Progress in combatting zoonoses that emerge from wildlife is often constrained by limited knowledge of the biology of pathogens within reservoir hosts. We focus on the host–pathogen dynamics of four emerging viruses associated with bats: Hendra, Nipah, Ebola, and Marburg viruses. Spillover of bat infections to humans and domestic animals often coincides with pulses of viral excretion within bat populations, but the mechanisms driving such pulses are unclear. Three hypotheses dominate current research on these emerging bat infections. First, pulses of viral excretion could reflect seasonal epidemic cycles driven by natural variations in population densities and contact rates among hosts. If lifelong immunity follows recovery, viruses may disappear locally but persist globally through migration; in either case, new outbreaks occur once births replenish the susceptible pool. Second, epidemic cycles could be the result of waning immunity within bats, allowing local circulation of viruses through oscillating herd immunity. Third, pulses could be generated by episodic shedding from persistently infected bats through a combination of physiological and ecological factors. The three scenarios can yield similar patterns in epidemiological surveys, but strategies to predict or manage spillover risk resulting from each scenario will be different. We outline an agenda for research on viruses emerging from bats that would allow for differentiation among the scenarios and inform development of evidence-based interventions to limit threats to human and animal health. These concepts and methods are applicable to a wide range of pathogens that affect humans, domestic animals, and wildlife. PMID:27489944

  5. Genetic reconstruction of the population dynamics of a carnivorous marsupial (Antechinus flavipes) in response to floods.

    PubMed

    Lada, Hania; Mac Nally, Ralph; Taylor, Andrea C

    2007-07-01

    Human activities such as regulating river flows, logging and removing fallen timber adversely affect floodplain ecosystems around the world. Studies of the dynamics of floodplain-dwelling populations will help to understand the effects of altered flood regimes and to manage and restore floodplains. The yellow-footed antechinus (Antechinus flavipes) is the only small, native, carnivorous mammal (Marsupialia) on many degraded floodplains in south-eastern Australia, where its abundance appears to increase with proximity to floods, which is partly due to enhanced survival (as inferred from increased abundance of second-year females). We analysed population genetic patterns and maternity among samples collected following the period of postnatal dispersal, in the years preceding and following planned floods, at different distances from flood locations along the Murray River. Our genic and genotypic analyses of mitochondrial DNA (mtDNA) control region haplotypes and 11 microsatellite loci demonstrated high immigration rates into sites in close proximity to floods. All sampled males emigrated from their natal sites to points of capture, while some females were philopatric. There were high rates of dispersal of males among all sites within a partially flooded forest, while females dispersed more to locations closest to inundations rather than to distant places. These results suggest that environmental flows are beneficial to antechinus both by enhancing adult survival and promoting dispersal of females. PMID:17614908

  6. Transmission or Within-Host Dynamics Driving Pulses of Zoonotic Viruses in Reservoir-Host Populations.

    PubMed

    Plowright, Raina K; Peel, Alison J; Streicker, Daniel G; Gilbert, Amy T; McCallum, Hamish; Wood, James; Baker, Michelle L; Restif, Olivier

    2016-08-01

    Progress in combatting zoonoses that emerge from wildlife is often constrained by limited knowledge of the biology of pathogens within reservoir hosts. We focus on the host-pathogen dynamics of four emerging viruses associated with bats: Hendra, Nipah, Ebola, and Marburg viruses. Spillover of bat infections to humans and domestic animals often coincides with pulses of viral excretion within bat populations, but the mechanisms driving such pulses are unclear. Three hypotheses dominate current research on these emerging bat infections. First, pulses of viral excretion could reflect seasonal epidemic cycles driven by natural variations in population densities and contact rates among hosts. If lifelong immunity follows recovery, viruses may disappear locally but persist globally through migration; in either case, new outbreaks occur once births replenish the susceptible pool. Second, epidemic cycles could be the result of waning immunity within bats, allowing local circulation of viruses through oscillating herd immunity. Third, pulses could be generated by episodic shedding from persistently infected bats through a combination of physiological and ecological factors. The three scenarios can yield similar patterns in epidemiological surveys, but strategies to predict or manage spillover risk resulting from each scenario will be different. We outline an agenda for research on viruses emerging from bats that would allow for differentiation among the scenarios and inform development of evidence-based interventions to limit threats to human and animal health. These concepts and methods are applicable to a wide range of pathogens that affect humans, domestic animals, and wildlife. PMID:27489944

  7. Effect of reaction-step-size noise on the switching dynamics of stochastic populations.

    PubMed

    Be'er, Shay; Heller-Algazi, Metar; Assaf, Michael

    2016-05-01

    In genetic circuits, when the messenger RNA lifetime is short compared to the cell cycle, proteins are produced in geometrically distributed bursts, which greatly affects the cellular switching dynamics between different metastable phenotypic states. Motivated by this scenario, we study a general problem of switching or escape in stochastic populations, where influx of particles occurs in groups or bursts, sampled from an arbitrary distribution. The fact that the step size of the influx reaction is a priori unknown and, in general, may fluctuate in time with a given correlation time and statistics, introduces an additional nondemographic reaction-step-size noise into the system. Employing the probability-generating function technique in conjunction with Hamiltonian formulation, we are able to map the problem in the leading order onto solving a stationary Hamilton-Jacobi equation. We show that compared to the "usual case" of single-step influx, bursty influx exponentially decreases the population's mean escape time from its long-lived metastable state. In particular, close to bifurcation we find a simple analytical expression for the mean escape time which solely depends on the mean and variance of the burst-size distribution. Our results are demonstrated on several realistic distributions and compare well with numerical Monte Carlo simulations. PMID:27300840

  8. Effect of reaction-step-size noise on the switching dynamics of stochastic populations

    NASA Astrophysics Data System (ADS)

    Be'er, Shay; Heller-Algazi, Metar; Assaf, Michael

    2016-05-01

    In genetic circuits, when the messenger RNA lifetime is short compared to the cell cycle, proteins are produced in geometrically distributed bursts, which greatly affects the cellular switching dynamics between different metastable phenotypic states. Motivated by this scenario, we study a general problem of switching or escape in stochastic populations, where influx of particles occurs in groups or bursts, sampled from an arbitrary distribution. The fact that the step size of the influx reaction is a priori unknown and, in general, may fluctuate in time with a given correlation time and statistics, introduces an additional nondemographic reaction-step-size noise into the system. Employing the probability-generating function technique in conjunction with Hamiltonian formulation, we are able to map the problem in the leading order onto solving a stationary Hamilton-Jacobi equation. We show that compared to the "usual case" of single-step influx, bursty influx exponentially decreases the population's mean escape time from its long-lived metastable state. In particular, close to bifurcation we find a simple analytical expression for the mean escape time which solely depends on the mean and variance of the burst-size distribution. Our results are demonstrated on several realistic distributions and compare well with numerical Monte Carlo simulations.

  9. Imperfect or Perfect Dynamic Bipolarity? The Case of Antonymous Affective Judgments

    ERIC Educational Resources Information Center

    Vautier, Stephane; Steyer, Rolf; Jmel, Said; Raufaste, Eric

    2005-01-01

    How is affective change rated with positive adjectives such as good related to change rated with negative adjectives such as bad? Two nested perfect and imperfect forms of dynamic bipolarity are defined using latent change structural equation models based on tetrads of items. Perfect bipolarity means that latent change scores correlate -1.…

  10. School Factors Explaining Achievement on Cognitive and Affective Outcomes: Establishing a Dynamic Model of Educational Effectiveness

    ERIC Educational Resources Information Center

    Creemers, Bert; Kyriakides, Leonidas

    2010-01-01

    The dynamic model of educational effectiveness defines school level factors associated with student outcomes. Emphasis is given to the two main aspects of policy, evaluation, and improvement in schools which affect quality of teaching and learning at both the level of teachers and students: a) teaching and b) school learning environment. Five…

  11. Environmental Factors Affecting Computer Assisted Language Learning Success: A Complex Dynamic Systems Conceptual Model

    ERIC Educational Resources Information Center

    Marek, Michael W.; Wu, Wen-Chi Vivian

    2014-01-01

    This conceptual, interdisciplinary inquiry explores Complex Dynamic Systems as the concept relates to the internal and external environmental factors affecting computer assisted language learning (CALL). Based on the results obtained by de Rosnay ["World Futures: The Journal of General Evolution", 67(4/5), 304-315 (2011)], who observed…

  12. Investigating the Effects of Sweat Therapy on Group Dynamics and Affect

    ERIC Educational Resources Information Center

    Colmant, Stephen A.; Eason, Evan A.; Winterowd, Carrie L.; Jacobs, Sue C.; Cashel, Chris

    2005-01-01

    In this study, we examined the effects of sweat therapy on group dynamics and affect. Sweat therapy is the combination of intense heat exposure with psychotherapy or counseling (Colmant & Merta, 1999; 2000). Twenty-four undergraduates were separated by sex and randomly assigned to eight sessions of either a sweat or non-sweat group counseling…

  13. Dynamic population flow based risk analysis of infectious disease propagation in a metropolis.

    PubMed

    Zhang, Nan; Huang, Hong; Duarte, Marlyn; Zhang, Junfeng Jim

    2016-09-01

    Knowledge on the characteristics of infectious disease propagation in metropolises plays a critical role in guiding public health intervention strategies to reduce death tolls, disease incidence, and possible economic losses. Based on the SIR model, we established a comprehensive spatiotemporal risk assessment model to compute infectious disease propagation within an urban setting using Beijing, China as a case study. The model was developed for a dynamic population distribution using actual data on location, density of residences and offices, and means of public transportation (e.g., subways, buses and taxis). We evaluated four influencing factors including biological, behavioral, environmental parameters and infectious sources. The model output resulted in a set of maps showing how the four influencing factors affected the trend and characteristics of airborne infectious disease propagation in Beijing. We compared the scenarios for the long-term dynamic propagation of infectious disease without governmental interventions versus scenarios with government intervention and hospital coordinated emergency responses. Lastly, the sensitivity of the average number of people at different location in spreading infections is analyzed. Based on our results, we provide valuable recommendations to governmental agencies and the public in order to minimize the disease propagation. PMID:27107973

  14. A stage-based model of manatee population dynamics

    USGS Publications Warehouse

    Runge, M.C.; Langtimm, C.A.; Kendall, W.L.

    2004-01-01

    A stage-structured population model for the Florida manatee (Trichechus manatus latirostris) was developed that explicitly incorporates uncertainty in parameter estimates. The growth rates calculated with this model reflect the status of the regional populations over the most recent 10-yr period. The Northwest and Upper St. Johns River regions have growth rates (8) of 1.037 (95% interval, 1.016?1.056) and 1.062 (1.037?1.081), respectively. The Southwest region has a growth rate of 0.989 (0.946?1.024), suggesting this population has been declining at about 1.1% per year. The estimated growth rate in the Atlantic region is 1.010 (0.988?1.029), but there is some uncertainty about whether adult survival rates have been constant over the last 10 yr; using the mean survival rates from the most recent 5-yr period, the estimated growth rate in this region is 0.970 (0.938?0.998). Elasticity analysis indicates that the most effective management actions should seek to increase adult survival rates. Decomposition of the uncertainty in the growth rates indicates that uncertainty about population status can best be reduced through increased monitoring of adult survival rate.

  15. POPULATION DYNAMICS OF THE CACTUS MOTH, CACTOBLASTIS CACTORUM IN FLORIDA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field populations of the cactus moth, Cactoblastis cactorum were surveyed weekly beginning in July 2006. We sampled the native cactus, Opuntia stricta visually to determine the densities and development of immature stages. Adult males were collected using a synthetic pheromone and a sticky wing trap...

  16. Breeding site heterogeneity reduces variability in frog recruitment and population dynamics

    USGS Publications Warehouse

    McCaffery, Rebecca M.; Eby, Lisa A.; Maxell, Bryce A.; Corn, Paul Stephen

    2013-01-01

    Environmental stochasticity can have profound effects on the dynamics and viability of wild populations, and habitat heterogeneity provides one mechanism by which populations may be buffered against the negative effects of environmental fluctuations. Heterogeneity in breeding pond hydroperiod across the landscape may allow amphibian populations to persist despite variable interannual precipitation. We examined recruitment dynamics over 10 yr in a high-elevation Columbia spotted frog (Rana luteiventris) population that breeds in ponds with a variety of hydroperiods. We combined these data with matrix population models to quantify the consequences of heterogeneity in pond hydroperiod on net recruitment (i.e. number of metamorphs produced) and population growth rates. We compared our heterogeneous system to hypothetical homogeneous environments with only ephemeral ponds, only semi-permanent ponds, and only permanent ponds. We also examined the effects of breeding pond habitat loss on population growth rates. Most eggs were laid in permanent ponds each year, but survival to metamorphosis was highest in the semi-permanent ponds. Recruitment success varied by both year and pond type. Net recruitment and stochastic population growth rate were highest under a scenario with homogeneous semi-permanent ponds, but variability in recruitment was lowest in the scenario with the observed heterogeneity in hydroperiods. Loss of pond habitat decreased population growth rate, with greater decreases associated with loss of permanent and semi-permanent habitat. The presence of a diversity of pond hydroperiods on the landscape will influence population dynamics, including reducing variability in recruitment in an uncertain climatic future.

  17. Fluctuations in Electronic Energy Affecting Singlet Fission Dynamics and Mixing with Charge-Transfer State: Quantum Dynamics Study.

    PubMed

    Fujihashi, Yuta; Ishizaki, Akihito

    2016-02-01

    Singlet fission is a spin-allowed process by which a singlet excited state is converted to two triplet states. To understand mechanisms of the ultrafast fission via a charge transfer (CT) state, one has investigated the dynamics through quantum-dynamical calculations with the uncorrelated fluctuation model; however, the electronic states are expected to experience the same fluctuations induced by the surrounding molecules because the electronic structure of the triplet pair state is similar to that of the singlet state except for the spin configuration. Therefore, the fluctuations in the electronic energies could be correlated, and the 1D reaction coordinate model may adequately describe the fission dynamics. In this work we develop a model for describing the fission dynamics to explain the experimentally observed behaviors. We also explore impacts of fluctuations in the energy of the CT state on the fission dynamics and the mixing with the CT state. The overall behavior of the dynamics is insensitive to values of the reorganization energy associated with the transition from the singlet state to the CT state, although the coherent oscillation is affected by the fluctuations. This result indicates that the mixing with the CT state is rather robust under the fluctuations in the energy of the CT state as well as the high-lying CT state. PMID:26732701

  18. Weather, Topoclimate, and Phenology: Population Dynamics of Checkerspot Butterflies in Complex Terrain

    NASA Astrophysics Data System (ADS)

    Weiss, S. B.

    2008-12-01

    The pathways leading from climate and weather to the distribution and abundance of organisms need to be clarified as rapid climate change affects ecosystems. This presentation describes population dynamics of the threatened Bay checkerspot butterfly, Euphydryas editha bayensis, in topographically complex habitat and demonstrates how weather and topoclimate drives those dynamics through phenology of butterflies and larval hostplants. We sampled densities of postdiapause larvae at sites in a 100 ha reserve, stratified by Mar 21 potential insolation, to estimate numbers and microdistribution of larvae. Larval numbers ranged from 27,000 to 900,000 over the 24-year study (1985-2008). Four consecutive drought years from 1987 to 1990 led to a 96% decrease in numbers, and sharp declines were observed following warmer than average growing seasons. Changes in larval numbers were negatively correlated to mean growing season temperatures (r2 = 0.36, p < 0.02), and the best stepwise regression model included April temperature, and November and April rainfall (r2 = 0.57, p < 0.001). Changes in the microdistribution of larvae cross the topoclimatic gradient was correlated with change in numbers (r2 = 0.41, p < 0.01) -- when larval numbers increased, the distribution of larvae shifted towards warmer slopes, and when numbers decreased, the distribution shifted toward cooler slopes. Larval densities were least variable on cooler slopes, indicating that cooler slopes provided core habitat and refugia from warm temperatures. The length of the phenological window between peak flight and hostplant senescence predicted population response (r2 = 0.44, p < 0.005). Hostplant senescence patterns across slopes - plants remain green for 4 or more weeks later on cool N-facing slopes than on warm S-facing slopes - explains microdistributional shifts. Many species depend on phenological coincidence with host resources, and occupy complex terrain as well, and these patterns and mechanisms may be

  19. Designing Molecular Dynamics Simulations to Shift Populations of the Conformational States of Calmodulin

    PubMed Central

    Aykut, Ayse Ozlem; Atilgan, Ali Rana; Atilgan, Canan

    2013-01-01

    We elucidate the mechanisms that lead to population shifts in the conformational states of calcium-loaded calmodulin (Ca2+-CaM). We design extensive molecular dynamics simulations to classify the effects that are responsible for adopting occupied conformations available in the ensemble of NMR structures. Electrostatic interactions amongst the different regions of the protein and with its vicinal water are herein mediated by lowering the ionic strength or the pH. Amino acid E31, which is one of the few charged residues whose ionization state is highly sensitive to pH differences in the physiological range, proves to be distinctive in its control of population shifts. E31A mutation at low ionic strength results in a distinct change from an extended to a compact Ca2+-CaM conformation within tens of nanoseconds, that otherwise occur on the time scales of microseconds. The kinked linker found in this particular compact form is observed in many of the target-bound forms of Ca2+-CaM, increasing the binding affinity. This mutation is unique in controlling C-lobe dynamics by affecting the fluctuations between the EF-hand motif helices. We also monitor the effect of the ionic strength on the conformational multiplicity of Ca2+-CaM. By lowering the ionic strength, the tendency of nonspecific anions in water to accumulate near the protein surface increases, especially in the vicinity of the linker. The change in the distribution of ions in the vicinal layer of water allows N- and C- lobes to span a wide variety of relative orientations that are otherwise not observed at physiological ionic strength. E31 protonation restores the conformations associated with physiological environmental conditions even at low ionic strength. PMID:24339763

  20. Population dynamics of bowfin in a south Georgia reservoir: latitudinal comparisons of population structure, growth, and mortality

    USGS Publications Warehouse

    Porter, Nicholas J.; Bonvechio, Timothy F.; McCormick, Joshua L.; Quist, Michael

    2014-01-01

    The objectives of this study were to evaluate the population dynamics of bowfin (Amia calva) in Lake Lindsay Grace, Georgia, and to compare those dynamics to other bowfin populations. Relative abundance of bowfin sampled in 2010 in Lake Lindsay Grace was low and variable (mean±SD; 2.7±4.7 fish per hour of electrofishing). Total length (TL) of bowfin collected in Lake Lindsay Grace varied from 233–683 mm. Age of bowfin in Lake Lindsay Grace varied from 0–5 yr. Total annual mortality (A) was estimated at 68%. Both sexes appeared to be fully mature by age 2 with gonadosomatic index values above 8 for females and close to 1 for males. The majority of females were older, longer, and heavier than males. Bowfin in Lake Lindsay Grace had fast growth up to age 4 and higher total annual mortality than the other populations examined in this study. A chi-square test indicated that size structure of bowfin from Lake Lindsay Grace was different than those of a Louisiana population and two bowfin populations from the upper Mississippi River. To further assess bowfin size structure, we proposed standard length (i.e., TL) categories: stock (200 mm, 8 inches), quality (350 mm, 14 inches), preferred (460 mm, 18 inches), memorable (560 mm, 22, inches), and trophy (710 mm, 28 inches). Because our knowledge of bowfin ecology is limited, additional understanding of bowfin population dynamics provides important insight that can be used in management of bowfin across their distribution.

  1. Demography of the Early Neolithic Population in Central Balkans: Population Dynamics Reconstruction Using Summed Radiocarbon Probability Distributions

    PubMed Central

    2016-01-01

    The Central Balkans region is of great importance for understanding the spread of the Neolithic in Europe but the Early Neolithic population dynamics of the region is unknown. In this study we apply the method of summed calibrated probability distributions to a set of published radiocarbon dates from the Republic of Serbia in order to reconstruct population dynamics in the Early Neolithic in this part of the Central Balkans. The results indicate that there was a significant population growth after ~6200 calBC, when the Neolithic was introduced into the region, followed by a bust at the end of the Early Neolithic phase (~5400 calBC). These results are broadly consistent with the predictions of the Neolithic Demographic Transition theory and the patterns of population booms and busts detected in other regions of Europe. These results suggest that the cultural process that underlies the patterns observed in Central and Western Europe was also in operation in the Central Balkan Neolithic and that the population increase component of this process can be considered as an important factor for the spread of the Neolithic as envisioned in the demic diffusion hypothesis. PMID:27508413

  2. Demography of the Early Neolithic Population in Central Balkans: Population Dynamics Reconstruction Using Summed Radiocarbon Probability Distributions.

    PubMed

    Porčić, Marko; Blagojević, Tamara; Stefanović, Sofija

    2016-01-01

    The Central Balkans region is of great importance for understanding the spread of the Neolithic in Europe but the Early Neolithic population dynamics of the region is unknown. In this study we apply the method of summed calibrated probability distributions to a set of published radiocarbon dates from the Republic of Serbia in order to reconstruct population dynamics in the Early Neolithic in this part of the Central Balkans. The results indicate that there was a significant population growth after ~6200 calBC, when the Neolithic was introduced into the region, followed by a bust at the end of the Early Neolithic phase (~5400 calBC). These results are broadly consistent with the predictions of the Neolithic Demographic Transition theory and the patterns of population booms and busts detected in other regions of Europe. These results suggest that the cultural process that underlies the patterns observed in Central and Western Europe was also in operation in the Central Balkan Neolithic and that the population increase component of this process can be considered as an important factor for the spread of the Neolithic as envisioned in the demic diffusion hypothesis. PMID:27508413

  3. When stable-stage equilibrium is unlikely: integrating transient population dynamics improves asymptotic methods

    PubMed Central

    Tremblay, Raymond L.; Raventos, Josep; Ackerman, James D.

    2015-01-01

    Background and Aims Evaluation of population projection matrices (PPMs) that are focused on asymptotically based properties of populations is a commonly used approach to evaluate projected dynamics of managed populations. Recently, a set of tools for evaluating the properties of transient dynamics has been expanded to evaluate PPMs and to consider the dynamics of populations prior to attaining the stable-stage distribution, a state that may never be achieved in disturbed or otherwise ephemeral habitats or persistently small populations. This study re-evaluates data for a tropical orchid and examines the value of including such analyses in an integrative approach. Methods Six small populations of Lepanthes rubripetala were used as a model system and the R software package popdemo was used to produce estimates of the indices for the asymptotic growth rate (lambda), sensitivities, reactivity, first-time step attenuation, maximum amplification, maximum attenuation, maximal inertia and maximal attenuation. The response in lambda to perturbations of demographic parameters using transfer functions and multiple perturbations on growth, stasis and fecundity were also determined. The results were compared with previously published asymptotic indices. Key Results It was found that combining asymptotic and transient dynamics expands the understanding of possible population changes. Comparison of the predicted density from reactivity and first-time step attenuation with the observed change in population size in two orchid populations showed that the observed density was within the predicted range. However, transfer function analysis suggests that the traditional approach of measuring perturbation of growth rates and persistence (inertia) may be misleading and is likely to result in erroneous management decisions. Conclusions Based on the results, an integrative approach is recommended using traditional PPMs (asymptotic processes) with an evaluation of the diversity of dynamics

  4. A life-history perspective on the demographic drivers of structured population dynamics in changing environments.

    PubMed

    Koons, David N; Iles, David T; Schaub, Michael; Caswell, Hal

    2016-09-01

    Current understanding of life-history evolution and how demographic parameters contribute to population dynamics across species is largely based on assumptions of either constant environments or stationary environmental variation. Meanwhile, species are faced with non-stationary environmental conditions (changing mean, variance, or both) created by climate and landscape change. To close the gap between contemporary reality and demographic theory, we develop a set of transient life table response experiments (LTREs) for decomposing realised population growth rates into contributions from specific vital rates and components of population structure. Using transient LTREs in a theoretical framework, we reveal that established concepts in population biology will require revision because of reliance on approaches that do not address the influence of unstable population structure on population growth and mean fitness. Going forward, transient LTREs will enhance understanding of demography and improve the explanatory power of models used to understand ecological and evolutionary dynamics. PMID:27401966

  5. Quantitative high-throughput population dynamics in continuous-culture by automated microscopy.

    PubMed

    Merritt, Jason; Kuehn, Seppe

    2016-01-01

    We present a high-throughput method to measure abundance dynamics in microbial communities sustained in continuous-culture. Our method uses custom epi-fluorescence microscopes to automatically image single cells drawn from a continuously-cultured population while precisely controlling culture conditions. For clonal populations of Escherichia coli our instrument reveals history-dependent resilience and growth rate dependent aggregation. PMID:27616752

  6. Bacterial population dynamics during the ensiling of Medicago sativa (alfalfa) and subsequent exposure to air

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aims: To describe, at high resolution, the bacterial population dynamics and chemical transformations during the ensiling of alfalfa and subsequent exposure to air. Methods and Results: Samples of alfalfa, ensiled alfalfa, and silage exposed to air were collected and their bacterial population stru...

  7. Mortality and Population Dynamics of Bemisia tabaci within a Multi-Crop System

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The population dynamics of mobile polyphagous pests is governed by a complex set of interacting factors that involve multiple host-plants, seasonality, movement and demography. Bemisia tabaci is a multivoltine insect with no diapause that maintains population continuity by moving from one host to a...

  8. Bacterial population structure and dynamics during the development of almond drupes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aims: To describe the bacterial populations and their dynamics during the development of almond drupes. Methods and Results: We examined 16S rRNA gene libraries derived from the bacterial populations on almond drupes at three stages of development: 1) when the drupes were full sized, but before embr...

  9. Effects of temporal variation in temperature and density dependence on insect population dynamics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding effects of environmental variation on insect populations is important in light of predictions about increasing future climatic variability. In order to understand the effects of changing environmental variation on population dynamics and life history evolution in insects one would need...

  10. The influence of historical climate on the population dynamics of three dominant sagebrush steppe plants.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Climate change could alter the population growth of dominant species, leading to profound effects on community structure and ecosystem dynamics. Understanding the links between historical variation in climate and population vital rates (survival, growth, recruitment) is one way to predict the impact...

  11. Does population size affect genetic diversity? A test with sympatric lizard species.

    PubMed

    Hague, M T J; Routman, E J

    2016-01-01

    Genetic diversity is a fundamental requirement for evolution and adaptation. Nonetheless, the forces that maintain patterns of genetic variation in wild populations are not completely understood. Neutral theory posits that genetic diversity will increase with a larger effective population size and the decreasing effects of drift. However, the lack of compelling evidence for a relationship between genetic diversity and population size in comparative studies has generated some skepticism over the degree that neutral sequence evolution drives overall patterns of diversity. The goal of this study was to measure genetic diversity among sympatric populations of related lizard species that differ in population size and other ecological factors. By sampling related species from a single geographic location, we aimed to reduce nuisance variance in genetic diversity owing to species differences, for example, in mutation rates or historical biogeography. We compared populations of zebra-tailed lizards and western banded geckos, which are abundant and short-lived, to chuckwallas and desert iguanas, which are less common and long-lived. We assessed population genetic diversity at three protein-coding loci for each species. Our results were consistent with the predictions of neutral theory, as the abundant species almost always had higher levels of haplotype diversity than the less common species. Higher population genetic diversity in the abundant species is likely due to a combination of demographic factors, including larger local population sizes (and presumably effective population sizes), faster generation times and high rates of gene flow with other populations. PMID:26306730

  12. Local Cattle and Badger Populations Affect the Risk of Confirmed Tuberculosis in British Cattle Herds

    PubMed Central

    Vial, Flavie; Johnston, W. Thomas; Donnelly, Christl A.

    2011-01-01

    Background The control of bovine tuberculosis (bTB) remains a priority on the public health agenda in Great Britain, after launching in 1998 the Randomised Badger Culling Trial (RBCT) to evaluate the effectiveness of badger (Meles meles) culling as a control strategy. Our study complements previous analyses of the RBCT data (focusing on treatment effects) by presenting analyses of herd-level risks factors associated with the probability of a confirmed bTB breakdown in herds within each treatment: repeated widespread proactive culling, localized reactive culling and no culling (survey-only). Methodology/Principal Findings New cases of bTB breakdowns were monitored inside the RBCT areas from the end of the first proactive badger cull to one year after the last proactive cull. The risk of a herd bTB breakdown was modeled using logistic regression and proportional hazard models adjusting for local farm-level risk factors. Inside survey-only and reactive areas, increased numbers of active badger setts and cattle herds within 1500 m of a farm were associated with an increased bTB risk. Inside proactive areas, the number of M. bovis positive badgers initially culled within 1500 m of a farm was the strongest predictor of the risk of a confirmed bTB breakdown. Conclusions/Significance The use of herd-based models provide insights into how local cattle and badger populations affect the bTB breakdown risks of individual cattle herds in the absence of and in the presence of badger culling. These measures of local bTB risks could be integrated into a risk-based herd testing programme to improve the targeting of interventions aimed at reducing the risks of bTB transmission. PMID:21464920

  13. POPULATION DYNAMICS OF HISPID COTTON RATS (SIGMODON HISPIDUS) ACROSS A NITROGEN AMENDED LANDSCAPE

    EPA Science Inventory

    Population dynamics of some small-mammal species appear to be regulated by plant-community structure, vegetative cover, plant diversity, and food quality. Thus, plant community changes associated with nitrogen additions would likely impact dynamics and structure of small-mammal ...

  14. Self-organized populations interacting under pursuit-evasion dynamics

    NASA Astrophysics Data System (ADS)

    Goudon, Thierry; Nkonga, Boniface; Rascle, Michel; Ribot, Magali

    2015-06-01

    We discuss the modeling of interacting populations through pursuit-evasion-or attraction-repulsion-principles : preys try to escape chasers, chasers are attracted by the presence of preys. We construct a hierarchy of models, ranging from ODEs systems with finite numbers of individuals of each population, to hydrodynamic systems. First-order macroscopic models look like generalized "two-species Keller-Segel equations". But, due to cross-interactions, we can show that the system does not exhibit any blow up phenomena in finite time. We also obtain second-order models, that have the form of systems of balance laws, derived from kinetic models. We bring out a few remarkable features of the models based either on mathematical analysis or numerical simulations.

  15. Two-population dynamics in a growing network model

    NASA Astrophysics Data System (ADS)

    Ivanova, Kristinka; Iordanov, Ivan

    2012-02-01

    We introduce a growing network evolution model with nodal attributes. The model describes the interactions between potentially violent V and non-violent N agents who have different affinities in establishing connections within their own population versus between the populations. The model is able to generate all stable triads observed in real social systems. In the framework of rate equations theory, we employ the mean-field approximation to derive analytical expressions of the degree distribution and the local clustering coefficient for each type of nodes. Analytical derivations agree well with numerical simulation results. The assortativity of the potentially violent network qualitatively resembles the connectivity pattern in terrorist networks that was recently reported. The assortativity of the network driven by aggression shows clearly different behavior than the assortativity of the networks with connections of non-aggressive nature in agreement with recent empirical results of an online social system.

  16. A DYNAMICAL SIGNATURE OF MULTIPLE STELLAR POPULATIONS IN 47 TUCANAE

    SciTech Connect

    Richer, Harvey B.; Heyl, Jeremy; Anderson, Jay; Kalirai, Jason S.; Shara, Michael M.; Dotter, Aaron; Fahlman, Gregory G.; Rich, R. Michael E-mail: heyl@phas.ubc.ca E-mail: jkalarai@stsci.edu E-mail: aaron.dotter@gmail.com E-mail: rmr@astro.ucla.edu

    2013-07-01

    Based on the width of its main sequence, and an actual observed split when viewed through particular filters, it is widely accepted that 47 Tucanae contains multiple stellar populations. In this contribution, we divide the main sequence of 47 Tuc into four color groups, which presumably represent stars of various chemical compositions. The kinematic properties of each of these groups are explored via proper motions, and a strong signal emerges of differing proper-motion anisotropies with differing main-sequence color; the bluest main-sequence stars exhibit the largest proper-motion anisotropy which becomes undetectable for the reddest stars. In addition, the bluest stars are also the most centrally concentrated. A similar analysis for Small Magellanic Cloud stars, which are located in the background of 47 Tuc on our frames, yields none of the anisotropy exhibited by the 47 Tuc stars. We discuss implications of these results for possible formation scenarios of the various populations.

  17. Worldwide Phylogenetic Distributions and Population Dynamics of the Genus Histoplasma

    PubMed Central

    Taylor, Maria L.; Gómez, Beatriz L.; Theodoro, Raquel C.; de Hoog, Sybren; Engelthaler, David M.; Zancopé-Oliveira, Rosely M.; Felipe, Maria S. S.

    2016-01-01

    Background Histoplasma capsulatum comprises a worldwide complex of saprobiotic fungi mainly found in nitrogen/phosphate (often bird guano) enriched soils. The microconidia of Histoplasma species may be inhaled by mammalian hosts, and is followed by a rapid conversion to yeast that can persist in host tissues causing histoplasmosis, a deep pulmonary/systemic mycosis. Histoplasma capsulatum sensu lato is a complex of at least eight clades geographically distributed as follows: Australia, Netherlands, Eurasia, North American classes 1 and 2 (NAm 1 and NAm 2), Latin American groups A and B (LAm A and LAm B) and Africa. With the exception of the Eurasian cluster, those clades are considered phylogenetic species. Methodology/Principal Findings Increased Histoplasma sampling (n = 234) resulted in the revision of the phylogenetic distribution and population structure using 1,563 aligned nucleotides from four protein-coding regions. The LAm B clade appears to be divided into at least two highly supported clades, which are geographically restricted to either Colombia/Argentina or Brazil respectively. Moreover, a complex population genetic structure was identified within LAm A clade supporting multiple monophylogenetic species, which could be driven by rapid host or environmental adaptation (~0.5 MYA). We found two divergent clades, which include Latin American isolates (newly named as LAm A1 and LAm A2), harboring a cryptic cluster in association with bats. Conclusions/Significance At least six new phylogenetic species are proposed in the Histoplasma species complex supported by different phylogenetic and population genetics methods, comprising LAm A1, LAm A2, LAm B1, LAm B2, RJ and BAC-1 phylogenetic species. The genetic isolation of Histoplasma could be a result of differential dispersion potential of naturally infected bats and other mammals. In addition, the present study guides isolate selection for future population genomics and genome wide association studies in this

  18. An investigation of factors affecting elementary school students' BMI values based on the system dynamics modeling.

    PubMed

    Lan, Tian-Syung; Chen, Kai-Ling; Chen, Pin-Chang; Ku, Chao-Tai; Chiu, Pei-Hsuan; Wang, Meng-Hsiang

    2014-01-01

    This study used system dynamics method to investigate the factors affecting elementary school students' BMI values. The construction of the dynamic model is divided into the qualitative causal loop and the quantitative system dynamics modeling. According to the system dynamics modeling, this study consisted of research on the four dimensions: student's personal life style, diet-relevant parenting behaviors, advocacy and implementation of school nutrition education, and students' peer interaction. The results of this study showed that students with more adequate health concepts usually have better eating behaviors and consequently have less chance of becoming obese. In addition, this study also verified that educational attainment and socioeconomic status of parents have a positive correlation with students' amounts of physical activity, and nutrition education has a prominent influence on changing students' high-calorie diets. PMID:24701250

  19. Population-level consequences of herbivory, changing climate, and source-sink dynamics on a long-lived invasive shrub.

    PubMed

    van Klinken, R D; Pichancourt, J B

    2015-12-01

    Long-lived plant species are highly valued environmentally, economically, and socially, but can also cause substantial harm as invaders. Realistic demographic predictions can guide management decisions, and are particularly valuable for long-lived species where population response times can be long. Long-lived species are also challenging, given population dynamics can be affected by factors as diverse as herbivory, climate, and dispersal. We developed a matrix model to evaluate the effects of herbivory by a leaf-feeding biological control agent released in Australia against a long-lived invasive shrub (mesquite, Leguminoseae: Prosopis spp.). The stage-structured, density-dependent model used an annual time step and 10 climatically diverse years of field data. Mesquite population demography is sensitive to source-sink dynamics as most seeds are consumed and redistributed spatially by livestock. In addition, individual mesquite plants, because they are long lived, experience natural climate variation that cycles over decadal scales, as well as anthropogenic climate change. The model therefore explicitly considered the effects of both net dispersal and climate variation. Herbivory strongly regulated mesquite populations through reduced growth and fertility, but additional mortality of older plants will be required to reach management goals within a reasonable time frame. Growth and survival of seeds and seedlings were correlated with daily soil moisture. As a result, population dynamics were sensitive to rainfall scenario, but population response times were typically slow (20-800 years to reach equilibrium or extinction) due to adult longevity. Equilibrium population densities were expected to remain 5% higher, and be more dynamic, if historical multi-decadal climate patterns persist, the effect being dampened by herbivory suppressing seed production irrespective of preceding rainfall. Dense infestations were unlikely to form under a drier climate, and required net

  20. Evolutionary dynamics of fluctuating populations with strong mutualism

    NASA Astrophysics Data System (ADS)

    Chotibut, Thiparat; Nelson, David

    2013-03-01

    Evolutionary game theory with finite interacting populations is receiving increased attention, including subtle phenomena associated with number fluctuations, i.e., ``genetic drift.'' Models of cooperation and competition often utilize a simplified Moran model, with a strictly fixed total population size. We explore a more general evolutionary model with independent fluctuations in the numbers of two distinct species, in a regime characterized by ``strong mutualism.'' The model has two absorbing states, each corresponding to fixation of one of the two species, and allows exploration of the interplay between growth, competition, and mutualism. When mutualism is favored, number fluctuations eventually drive the system away from a stable fixed point, characterized by cooperation, to one of the absorbing states. Well-mixed populations will thus be taken over by a single species in a finite time, despite the bias towards cooperation. We calculate both the fixation probability and the mean fixation time as a function of the initial conditions and carrying capacities in the strong mutualism regime, using the method of matched asymptotic expansions. Our results are compared to computer simulations.

  1. Analysis of Bacillus thuringiensis Population Dynamics and Its Interaction With Pseudomonas fluorescens in Soil

    PubMed Central

    Rojas-Ruiz, Norma Elena; Sansinenea-Royano, Estibaliz; Cedillo-Ramirez, Maria Lilia; Marsch-Moreno, Rodolfo; Sanchez-Alonso, Patricia; Vazquez-Cruz, Candelario

    2015-01-01

    Background: Bacillus thuringiensis is the most successful biological control agent, however, studies so far have shown that B. thuringiensis is very sensitive to environmental factors such as soil moisture and pH. Ultraviolet light from the sun had been considered as the main limiting factor for its persistence in soil and it has recently been shown that the antagonism exerted by other native soil organisms, such as Pseudomonas fluorescens, is a determining factor in the persistence of this bacterium under in vitro culture conditions. Objectives: The aim of the present investigation was to analyze the population dynamics of B. thuringiensis and its interaction with P. fluorescens using microbiological and molecular methods in soil, under different conditions, and to determinate the effect of nutrients and moisture on its interaction. Materials and Methods: The monitoring was performed by microbiological methods, such as viable count of bacteria, and molecular methods such as Polymerase Chain Reaction (PCR) and hybridization, using the direct extraction of DNA from populations of inoculated soil. Results: The analysis of the interaction between B. thuringiensis and P. fluorescens in soil indicated that the disappearance of B. thuringiensis IPS82 is not dependent on the moisture but the composition of nutrients that may be affecting the secretion of toxic compounds in the environment of P. fluorescens. The results showed that the recovered cells were mostly spores and not vegetative cells in all proved treatments. The molecular methods were effective for monitoring bacterial population inoculated in soil. Conclusions: Bacillus thuringiensis is very sensitive to the interaction of P. fluorescens, however is capable to survive in soil due to its capacity of sporulate. Some of the cells in the form of spores germinated and folded slightly and remained in a constant cycle of sporulation and germination. This confirms that B. thuringiensis IPS82 can germinate, grow and

  2. Population dynamics of the Concho Water Snake in rivers and reservoirs

    USGS Publications Warehouse

    Whiting, M.J.; Dixon, J.R.; Greene, B.D.; Mueller, J.M.; Thornton, O.W., Jr.; Hatfield, J.S.; Nichols, J.D.; Hines, J.E.

    2008-01-01

    The Concho Water Snake (Nerodia harteri paucimaculata) is confined to the Concho-Colorado River valley of central Texas, thereby occupying one of the smallest geographic ranges of any North American snake. In 1986, N. h. paucimaculata was designated as a federally threatened species, in large part because of reservoir projects that were perceived to adversely affect the amount of habitat available to the snake. During a ten-year period (1987-1996), we conducted capture-recapture field studies to assess dynamics of five subpopulations of snakes in both natural (river) and man-made (reservoir) habitats. Because of differential sampling of subpopulations, we present separate results for all five subpopulations combined (including large reservoirs) and three of the five subpopuiations (excluding large reservoirs). We used multistate capture-recapture models to deal with stochastic transitions between pre-reproductive and reproductive size classes and to allow for the possibility of different survival and capture probabilities for the two classes. We also estimated both the finite rate of increase (??) for a deterministic, stage-based, female-only matrix model using the average litter size, and the average rate of adult population change, ??, which describes changes in numbers of adult snakes, using a direct capture-recapture approach to estimation. Average annual adult survival was about 0.23 and similar for males and females. Average annual survival for subadults was about 0.14. The parameter estimates from the stage-based projection matrix analysis all yielded asymptotic values of ?? < 1, suggesting populations that are not viable. However, the direct estimates of average adult ?? for the three subpopulations excluding major reservoirs were ?? = 1.26, SE??(??) = 0.18 and ?? = 0.99, SE??(??) = 0.79, based on two different models. Thus, the direct estimation approach did not provide strong evidence of population declines of the riverine subpopulations, but the

  3. Dynamic Association Between Negative Affect and Alcohol Lapses Following Alcohol Treatment

    PubMed Central

    Witkiewitz, Katie; Villarroel, Nadia Aracelliz

    2009-01-01

    Clinical research has found a strong associat