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Sample records for algal population dynamics

  1. A mechanistic analysis of density dependence in algal population dynamics

    Directory of Open Access Journals (Sweden)

    Adrian eBorlestean

    2015-04-01

    Full Text Available Population density regulation is a fundamental principle in ecology, but the specific process underlying functional expression of density dependence remains to be fully elucidated. One view contends that patterns of density dependence are largely fixed across a species irrespective of environmental conditions, whereas another is that the strength and expression of density dependence are fundamentally variable depending on the nature of exogenous or endogenous constraints acting on the population. We conducted a study investigating the expression of density dependence in Chlamydomonas spp. grown under a gradient from low to high nutrient density. We predicted that the relationship between per capita growth rate (pgr and population density would vary from concave up to concave down as nutrient density became less limiting and populations experienced weaker density regulation. Contrary to prediction, we found that the relationship between pgr and density became increasingly concave-up as nutrient levels increased. We also found that variation in pgr increased, and pgr levels reached higher maxima in nutrient-limited environments. Most likely, these results are attributable to population growth suppression in environments with high intraspecific competition due to limited nutrient resources. Our results suggest that density regulation is strongly variable depending on exogenous and endogenous processes acting on the population, implying that expression of density dependence depends extensively on local conditions. Additional experimental work should reveal the mechanisms influencing how the expression of density dependence varies across populations through space and time.

  2. [Effects of water temperature and edible algal density on the population dynamics and sexual reproduction of Moina irrasa].

    Science.gov (United States)

    Li, Yu-Ying; Deng, Dao-Gui; Lei, Juan; Xi, Yi-Long

    2011-12-01

    This paper studied the population dynamics and sexual reproduction of Moina irrasa at different water temperature and edible algal density. The population density of M. irrasa was obviously higher at high than at medium and low densities of edible algae, with the maximum at high edible algal density and 20 degrees C. At the same temperatures, the average number of the offsprings first produced by per female M. irrasa declined with decreasing edible algal density, and the maximum value appeared at 25 degrees C and at high edible algal density. The male offsprings produced were obviously higher at high than at medium and low edible algal densities. There was a significant correlation between the male density and the population density of M. irrasa. The number of ephippia produced by M. irrasa declined with decreasing edible algal density, and was higher at 25 degrees C than at other temperatures. Edible algal density had larger effects on the population dynamics and sexual reproduction of M. irrasa, as compared with temperature.

  3. Population dynamics of an algal bacterial cenosis in closed ecological system

    Science.gov (United States)

    Pisman, T. I.; Galayda, Ya. V.; Loginova, N. S.

    The paper deals with microalgae-bacteria interrelationships in the "autotroph-heterotroph" aquatic biotic cycle. Explanations of why and how algal-bacterial ecosystems are formed still remain controversial. The paper presents results of experimental and theoretical investigations of the functioning of the algal-bacterial cenosis (the microalga Chlorella vulgaris and concomitant microflora). The Chlorella microbial community is dominated by representatives of the genus Pseudomonas. Experiments with non-sterile batch cultures of Chlorella on Tamiya medium showed that the biomass of microorganisms increases simultaneously with the increase in microalgal biomass. The microflora of Chlorella can grow on organic substances released by photosynthesizing Chlorella. Microorganisms can also use dying Chlorella cells, i.e. form a "producer-reducer" biocycle. To get a better insight into the cenosis-forming role of microalgae, a mathematical model of the "autotroph-heterotroph" aquatic biotic cycle has been constructed, taking into account the utilization of Chlorella photosynthates and dead cells by microorganisms and the contribution of the components to the nitrogen cycle. A theoretical study showed that the biomass of concomitant bacteria grown on glucose and detritus is larger than the biomass of bacteria utilizing only microalgal photosynthates, which agrees well with the experimental data.

  4. Effects of photoperiod on nutrient removal, biomass production, and algal-bacterial population dynamics in lab-scale photobioreactors treating municipal wastewater.

    Science.gov (United States)

    Lee, Chang Soo; Lee, Sang-Ah; Ko, So-Ra; Oh, Hee-Mock; Ahn, Chi-Yong

    2015-01-01

    Effects of photoperiod were investigated in lab-scale photobioreactors containing algal-bacterial consortia to reduce organic nutrients from municipal wastewater. Under three photoperiod conditions (12 h:12 h, 36 h:12 h, and 60 h:12 h dark–light cycles), nutrient removals and biomass productions were measured along with monitoring microbial population dynamics. After a batch operation for 12 days, 59–80% carbon, 35–88% nitrogen, and 43–89% phosphorus were removed from influents, respectively. In this study, carbon removal was related positively to the length of dark cycles, while nitrogen and phosphorus removals inversely. On the contrast, the highest microbial biomass in terms of chlorophyll a, dry cell weight, and algal/bacterial rRNA gene markers was produced under the 12 h:12 h dark–light cycle among the three photoperiods. The results showed 1) simultaneous growths between algae and bacteria in the microbial consortia and 2) efficient nitrogen and phosphorus removals along with high microbial biomass production under prolonged light conditions. Statistical analyses indicated that carbon removal was significantly related to the ratio of bacteria to algae in the microbial consortia along with prolonged dark conditions (p < 0.05). In addition, the ratio of nitrogen removal to phosphorus removal decreased significantly under prolonged dark conditions (p < 0.001). These results indicated that the photoperiod condition has remarkable impacts on adjusting nutrient removal, producing microbial biomass, and altering algal-bacterial population dynamics. Therefore, the control of photoperiod was suggested as an important operating parameter in the algal wastewater treatment.

  5. The extended Kalman filter for forecast of algal bloom dynamics.

    Science.gov (United States)

    Mao, J Q; Lee, Joseph H W; Choi, K W

    2009-09-01

    A deterministic ecosystem model is combined with an extended Kalman filter (EKF) to produce short term forecasts of algal bloom and dissolved oxygen dynamics in a marine fish culture zone (FCZ). The weakly flushed FCZ is modelled as a well-mixed system; the tidal exchange with the outer bay is lumped into a flushing rate that is numerically determined from a three-dimensional hydrodynamic model. The ecosystem model incorporates phytoplankton growth kinetics, nutrient uptake, photosynthetic production, nutrient sources from organic fish farm loads, and nutrient exchange with a sediment bed layer. High frequency field observations of chlorophyll, dissolved oxygen (DO) and hydro-meteorological parameters (sampling interval Deltat=1 day, 2h, 1h, respectively) and bi-weekly nutrient data are assimilated into the model to produce the combined state estimate accounting for the uncertainties. In addition to the water quality state variables, the EKF incorporates dynamic estimation of algal growth rate and settling velocity. The effectiveness of the EKF data assimilation is studied for a wide range of sampling intervals and prediction lead-times. The chlorophyll and dissolved oxygen estimated by the EKF are compared with field data of seven algal bloom events observed at Lamma Island, Hong Kong. The results show that the EKF estimate well captures the nonlinear error evolution in time; the chlorophyll level can be satisfactorily predicted by the filtered model estimate with a mean absolute error of around 1-2 microg/L. Predictions with 1-2 day lead-time are highly correlated with the observations (r=0.7-0.9); the correlation stays at a high level for a lead-time of 3 days (r=0.6-0.7). Estimated algal growth and settling rates are in accord with field observations; the more frequent DO data can compensate for less frequent algal biomass measurements. The present study is the first time the EKF is successfully applied to forecast an entire algal bloom cycle, suggesting the

  6. Population dynamics

    Directory of Open Access Journals (Sweden)

    Cooch, E. G.

    2004-06-01

    Full Text Available Increases or decreases in the size of populations over space and time are, arguably, the motivation for much of pure and applied ecological research. The fundamental model for the dynamics of any population is straightforward: the net change over time in the abundance of some population is the simple difference between the number of additions (individuals entering the population minus the number of subtractions (individuals leaving the population. Of course, the precise nature of the pattern and process of these additions and subtractions is often complex, and population biology is often replete with fairly dense mathematical representations of both processes. While there is no doubt that analysis of such abstract descriptions of populations has been of considerable value in advancing our, there has often existed a palpable discomfort when the ‘beautiful math’ is faced with the often ‘ugly realities’ of empirical data. In some cases, this attempted merger is abandoned altogether, because of the paucity of ‘good empirical data’ with which the theoretician can modify and evaluate more conceptually–based models. In some cases, the lack of ‘data’ is more accurately represented as a lack of robust estimates of one or more parameters. It is in this arena that methods developed to analyze multiple encounter data from individually marked organisms has seen perhaps the greatest advances. These methods have rapidly evolved to facilitate not only estimation of one or more vital rates, critical to population modeling and analysis, but also to allow for direct estimation of both the dynamics of populations (e.g., Pradel, 1996, and factors influencing those dynamics (e.g., Nichols et al., 2000. The interconnections between the various vital rates, their estimation, and incorporation into models, was the general subject of our plenary presentation by Hal Caswell (Caswell & Fujiwara, 2004. Caswell notes that although interest has traditionally

  7. Dynamics of ellipsoidal tracers in swimming algal suspensions

    Science.gov (United States)

    Yang, Ou; Peng, Yi; Liu, Zhengyang; Tang, Chao; Xu, Xinliang; Cheng, Xiang

    2016-10-01

    Enhanced diffusion of passive tracers immersed in active fluids is a universal feature of active fluids and has been extensively studied in recent years. Similar to microrheology for equilibrium complex fluids, the unusual enhanced particle dynamics reveal intrinsic properties of active fluids. Nevertheless, previous studies have shown that the translational dynamics of spherical tracers are qualitatively similar, independent of whether active particles are pushers or pullers—the two fundamental classes of active fluids. Is it possible to distinguish pushers from pullers by simply imaging the dynamics of passive tracers? Here, we investigated the diffusion of isolated ellipsoids in algal C. reinhardtii suspensions—a model for puller-type active fluids. In combination with our previous results on pusher-type E. coli suspensions [Peng et al., Phys. Rev. Lett. 116, 068303 (2016), 10.1103/PhysRevLett.116.068303], we showed that the dynamics of asymmetric tracers show a profound difference in pushers and pullers due to their rotational degree of freedom. Although the laboratory-frame translation and rotation of ellipsoids are enhanced in both pushers and pullers, similar to spherical tracers, the anisotropic diffusion in the body frame of ellipsoids shows opposite trends in the two classes of active fluids. An ellipsoid diffuses fastest along its major axis when immersed in pullers, whereas it diffuses slowest along the major axis in pushers. This striking difference can be qualitatively explained using a simple hydrodynamic model. In addition, our study on algal suspensions reveals that the influence of the near-field advection of algal swimming flows on the translation and rotation of ellipsoids shows different ranges and strengths. Our work provides not only new insights into universal organizing principles of active fluids, but also a convenient tool for detecting the class of active particles.

  8. 温度和食用藻密度对发头裸腹潘种群动态和两性生殖的影响%Effects of water temperature and edible algal density on the population dynamics and sexual reproduction of Moina irrasa

    Institute of Scientific and Technical Information of China (English)

    李玉颖; 邓道贵; 雷娟; 席贻龙

    2011-01-01

    Taihu River basin; macrobenthos; community structure; TWINSPAN; DCA; CCAThis paper studied the population dynamics and sexual reproduction of Moina irrasa at different water temperature and edible algal density. The population density of M. Irrasa was obviously higher at high than at medium and low densities of edible algae, with the maximum at high edible algal density and 20 %. At the same temperatures, the average number of the offsprings first produced by per female M. Irrasa declined with decreasing edible algal density, and the maximum value appeared at 25℃ and at high edible algal density. The male offsprings produced were obviously higher at high than at medium and low edible algal densities. There was a significant correlation- between the male density and the population density of M. Irrasa. The number of ephippia produced by M. Irrasa declined with decreasing edible algal density, and was higher at 25 ℃ than at other temperatures. Edible algal density had larger effects on the population dynamics and sexual reproduction of M. Irrasa, as compared with temperature.%研究了不同温度和食用藻密度对发头裸腹潘种群动态和两性生殖的影响.结果表明:温度、食用藻密度对发头裸腹溞的种群密度、雄体密度和卵鞍数均有显著影响.高食用藻密度组的发头裸腹潘种群密度明显高于中、低食用藻密度组,其最大种群密度出现在20℃下的高食用藻密度组.在相同的温度下,发头裸腹溞的首次产幼溞数随食用藻密度的降低而减少,平均每个母潘首次产出的最大幼潘数出现在25℃下的高食用藻密度组.高食用藻密度组发头裸腹潘产生的雄体密度明显高于中、低食用藻密度组.发头裸腹溞的雄体密度与其种群密度之间存在极显著的相关性.发头裸腹溞所产的卵鞍数随食用藻密度的下降而下降,且25℃下发头裸腹溞所产的卵鞍数明显高于其他温度组.与温度相比,食用藻密度

  9. Carbon conversion efficiency and population dynamics of a marine algae–bacteria consortium growing on simplified synthetic digestate: First step in a bioprocess coupling algal production and anaerobic digestion

    OpenAIRE

    Vasseur, C.; Bougaran, G.; Garnier, M.; Hamelin, J.; Leboulanger, Christophe; Le Chevanton, M.; Mostajir, B; Sialve, B.; Steyer, J. P.; Fouilland, E.

    2012-01-01

    Association of microalgae culture and anaerobic digestion seems a promising technology for sustainable algal biomass and biogas production. The use of digestates for sustaining the growth of microalgae reduces the costs and the environmental impacts associated with the substantial algal nutrient requirements. A natural marine algae–bacteria consortium was selected by growing on a medium containing macro nutrients (ammonia, phosphate and acetate) specific of a digestate, and was submitted to a...

  10. From benchtop to raceway : spectroscopic signatures of dynamic biological processes in algal communities.

    Energy Technology Data Exchange (ETDEWEB)

    Trahan, Christine Alexandra; Garcia, Omar Fidel; Martino, Anthony A.; Raymer, Michelle; Collins, Aaron M.; Hanson, David T. (University of New Mexico, Albuquerque, NM); Turner, Tom (University of New Mexico, Albuquerque, NM); Powell, Amy Jo; James, Scott Carlton (Sandia National Laboratories, Livermore, CA); Timlin, Jerilyn Ann; Scholle, Steven (University of New Mexico, Albuquerque, NM); Dwyer, Brian P.; Ruffing, Anne; Jones, Howland D. T.; Ricken, James Bryce; Reichardt, Thomas A. (Sandia National Laboratories, Livermore, CA)

    2010-08-01

    The search is on for new renewable energy and algal-derived biofuel is a critical piece in the multi-faceted renewable energy puzzle. It has 30x more oil than any terrestrial oilseed crop, ideal composition for biodiesel, no competition with food crops, can be grown in waste water, and is cleaner than petroleum based fuels. This project discusses these three goals: (1) Conduct fundamental research into the effects that dynamic biotic and abiotic stressors have on algal growth and lipid production - Genomics/Transcriptomics, Bioanalytical spectroscopy/Chemical imaging; (2) Discover spectral signatures for algal health at the benchtop and greenhouse scale - Remote sensing, Bioanalytical spectroscopy; and (3) Develop computational model for algal growth and productivity at the raceway scale - Computational modeling.

  11. Algal epibiosis on Megabalanus tintinnabulum and its role in segregation of the Balanus amphitrite population

    Digital Repository Service at National Institute of Oceanography (India)

    Eswaran, R.; Khandeparker, L.

    . Ecol. (Evol. Persp.), vol.35(4); 2014; 492-505 Algal epibiosis on Megabalanus tintinnabulum and its role in segregation of Balanus amphitrite population Ranjith E and Lidita Khandeparker* Council of Scientific and Industrial Research... & BPA were maintained on ZMA and BPA slants as described by Konya et al. (1995). The isolated bacteria (Table I) were identified following ‘Bergey’s manual of systematic bacteriology (Holt et al. 1994) and manual for the identification of medical...

  12. Effects of DDT and dicofol on population growth of Brachionus calyciflorus under different algal (Scenedesmus obliquus) densities.

    Science.gov (United States)

    Xu, Xiao-Ping; Xi, Yi-Long; Chu, Zhao-Xia; Xiang, Xian-Ling

    2014-09-01

    A number of organochlorine pesticides, including DDT and dicofol, used to be important in crop protection and management. Their residues may reach water bodies and eventually affect the non-target organisms such as rotifers. In the present study, we evaluated the effects of DDT (0.05, 0.1, 0.2 and 0.4 mg l(-1)) and dicofol (0.1, 0.2, 0.4 and 0.8 mg l(-1)) on the population growth of rotifer Brachionus calyciflorus under two levels of Scenedesmus obliquus (1.0 x 10(6) and 3.0 x 10(6) cell ml(-1)). Regardless of the food level, DDT was more toxic than dicofol to B. calyciflorus. Under low food level, DDT at 0.1 and 0.2 mg l(-1) decreased the population growth rate (r), and DDT at 0.05-0.4 mg l(-1) decreased the maximum population density (K). Dicofol at 0.4 and 0.8 mg l(-1) decreased r and K, but dicofol at 0.2 mg l(-1) increased K. Under high food level, DDT at 0.05-0.2 mg l(-1) increased K, whereas DDT at 0.4 mg l(-1) as well as dicofol at 0.4 and 0.8 mg l(-1) decreased r and K. Increase in food level increased r exposed to DDT at 0.05-0.2 mg l(-1) as well as dicofol at 0.8 mg l(-1), and Kexposed to DDTat 0.05-0.2 mg l(-1) as well as dicofol at 0.1 and 0.2 mg l(-1). DDT concentration, algal density and their interaction affected r and K of B. calyciflorus. Both dicofol concentration and algal density affected r. Dicofol concentration, algal density and their interaction affected K. Both r and K were suitable endpoints for assessing the effects of DDT and dicofol on the rotifers population dynamics under two algal densities, and the latter was more sensitive.

  13. Assessment of Algal Farm Designs using a Dynamic Modular Approach

    Energy Technology Data Exchange (ETDEWEB)

    Abodeely, Jared M. [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology; Stevens, Daniel M. [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology; Ray, Allison E. [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology; Newby, Deborah T. [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology; Coleman, Andre M. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Hydrology Technical Group; Cafferty, Kara G. [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology

    2014-07-01

    The notion of renewable energy provides an importantmechanism for diversifying an energy portfolio,which ultimately would have numerous benefits including increased energy resilience, reduced reliance on foreign energysupplies, reduced GHG emissions, development of a green energy sector that contributes to economic growth,and providing a sustainable energy supply. The conversion of autotrophic algae to liquid transportation fuels is the basis of several decades of research to competitively bring energy-scale production into reality; however, many challenges still remain for making algal biofuels economically viable. Addressing current challenges associatedwith algal production systems, in part, requires the ability to assess spatial and temporal variability, rapidly evaluate alternative algal production system designs, and perform large-scale assessments considering multiple scenarios for thousands of potential sites. We introduce the development and application of the Algae Logistics Model (ALM) which is tailored to help address these challenges. The flexible nature of the ALM architecture allows the model to: 1) interface with external biomass production and resource assessment models, as well as other relevant datasets including those with spatiotemporal granularity; 2) interchange design processes to enable operational and economic assessments ofmultiple design configurations, including the integration of current and new innovative technologies; and 3) conduct trade-off analysis to help understand the site-specific techno-economic trade-offs and inform technology decisions. This study uses the ALM to investigate a baseline open-pond production system determined by model harmonization efforts conducted by the U.S. Department of Energy. Six sites in the U.S. southern-tierwere sub-selected and assessed using daily site-specific algaebiomass productivity data to determine the economic viability of large-scale open-pond systems. Results show that costs can vary

  14. Assessment of Algal Farm Designs Using a Dynamic Modular Approach

    Energy Technology Data Exchange (ETDEWEB)

    Abodeely, Jared [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology; Coleman, Andre M. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Hydrology Technical Group; Stevens, Daniel M. [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology; Ray, Allison E. [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology; Cafferty, Kara G. [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology; Newby, Deborah T. [Idaho National Laboratory (INL), Idaho Falls, ID (United States). Biofuels and Renewable Energy Technology

    2014-07-01

    The notion of renewable energy provides an important mechanism for diversifying an energy portfolio, which ultimately would have numerous benefits including increased energy resilience, reduction of foreign energy supplies, reduced GHG emissions, development of a green energy sector that contributes to economic growth, and providing a sustainable energy supply. The conversion of autotrophic algae to liquid transportation fuels is the basis of several decades of research to competitively bring energy-scale production into reality; however, many challenges still remain for making algal biofuels economically viable. Addressing current challenges associated with algal production systems, in part, requires the ability to assess spatial and temporal variability, rapidly evaluate alternative algal production system designs, and perform large-scale assessments considering multiple scenarios for thousands of potential sites. We introduce the Algae Logistics Model (ALM) which helps to address these challenges. The flexible nature of the ALM architecture allows the model to: 1) interface with external biomass production and resource assessment models, as well as other relevant datasets including those with spatiotemporal granularity; 2) interchange design processes to enable operational and economic assessments of multiple design configurations, including the integration of current and new innovative technologies; and 3) conduct trade-off analysis to help understand the site-specific techno-economic trade-offs and inform technology decisions. This study uses the ALM to investigate a baseline open-pond production system determined by model harmonization efforts conducted by the U.S. Department of Energy. Six sites in the U.S. southern-tier were sub-selected and assessed using daily site-specific algae biomass productivity data to determine the economic viability of large-scale open-pond systems. Results show that costs can vary significantly depending on location and biomass

  15. In situ oxygen dynamics in coral-algal interactions.

    Directory of Open Access Journals (Sweden)

    Daniel Wangpraseurt

    Full Text Available BACKGROUND: Coral reefs degrade globally at an alarming rate, with benthic algae often replacing corals. However, the extent to which benthic algae contribute to coral mortality, and the potential mechanisms involved, remain disputed. Recent laboratory studies suggested that algae kill corals by inducing hypoxia on the coral surface, through stimulated microbial respiration. METHODS/FINDINGS: We examined the main premise of this hypothesis by measuring in situ oxygen microenvironments at the contact interface between the massive coral Porites spp. and turf algae, and between Porites spp. and crustose coralline algae (CCA. Oxygen levels at the interface were similar to healthy coral tissue and ranged between 300-400 µM during the day. At night, the interface was hypoxic (~70 µM in coral-turf interactions and close to anoxic (~2 µM in coral-CCA interactions, but these values were not significantly different from healthy tissue. The diffusive boundary layer (DBL was about three times thicker at the interface than above healthy tissue, due to a depression in the local topography. A numerical model, developed to analyze the oxygen profiles above the irregular interface, revealed strongly reduced net photosynthesis and dark respiration rates at the coral-algal interface compared to unaffected tissue during the day and at night, respectively. CONCLUSIONS/SIGNIFICANCE: Our results showed that hypoxia was not a consistent feature in the microenvironment of the coral-algal interface under in situ conditions. Therefore, hypoxia alone is unlikely to be the cause of coral mortality. Due to the modified topography, the interaction zone is distinguished by a thicker diffusive boundary layer, which limits the local metabolic activity and likely promotes accumulation of potentially harmful metabolic products (e.g., allelochemicals and protons. Our study highlights the importance of mass transfer phenomena and the need for direct in situ measurements of

  16. Market Squid Population Dynamics

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains population dynamics data on paralarvae, juvenile and adult market squid collected off California and the US Pacific Northwest. These data were...

  17. STABILITY AND BIFURCATION BEHAVIORS ANALYSIS IN A NONLINEAR HARMFUL ALGAL DYNAMICAL MODEL

    Institute of Scientific and Technical Information of China (English)

    WANG Hong-li; FENG Jian-feng; SHEN Fei; SUN Jing

    2005-01-01

    A food chain made up of two typical algae and a zooplankton was considered. Based on ecological eutrophication, interaction of the algal and the prey of the zooplankton, a nutrient nonlinear dynamic system was constructed. Using the methods of the modern nonlinear dynamics, the bifurcation behaviors and stability of the model equations by changing the control parameter r were discussed. The value of r for bifurcation point was calculated, and the stability of the limit cycle was also discussed. The result shows that through quasi-periodicity bifurcation the system is lost in chaos.

  18. Language dynamics in finite populations.

    Science.gov (United States)

    Komarova, Natalia L; Nowak, Martin A

    2003-04-01

    Any mechanism of language acquisition can only learn a restricted set of grammars. The human brain contains a mechanism for language acquisition which can learn a restricted set of grammars. The theory of this restricted set is universal grammar (UG). UG has to be sufficiently specific to induce linguistic coherence in a population. This phenomenon is known as "coherence threshold". Previously, we have calculated the coherence threshold for deterministic dynamics and infinitely large populations. Here, we extend the framework to stochastic processes and finite populations. If there is selection for communicative function (selective language dynamics), then the analytic results for infinite populations are excellent approximations for finite populations; as expected, finite populations need a slightly higher accuracy of language acquisition to maintain coherence. If there is no selection for communicative function (neutral language dynamics), then linguistic coherence is only possible for finite populations.

  19. Influence of Diadema antillarum populations (Echinodermata: Diadematidae) on algal community structure in Jardines de la Reina, Cuba.

    Science.gov (United States)

    Martín Blanco, Félix; Clero Alonso, Lídice; González Sansón, Gaspar; Amargós Fabián, Pina

    2011-09-01

    The 1983-1984 mass mortality of Diadema antillarum produced severe damages on Caribbean reefs contributing to substantial changes in community structure that still persist. Despite the importance of Diadema grazing in structuring coral reefs, available information on current abundances and algal-urchin interactions in Cuba is scarce. We analyzed spatial variations in Diadema abundance and its influence on algal community structure in 22 reef sites in Jardines de la Reina, in June/2004 and April/2005. Urchins were counted in five 30 x 2m transects per site, and algal coverage was estimated in randomly located 0.25m side quadrats (15 per site). Abundances of Diadema were higher at reef crests (0.013-1.553 ind/m2), while reef slope populations showed values up to three orders of magnitude lower and were overgrown by macroalgae (up to 87%, local values). Algal community structure at reef slopes were dominated by macroalgae, especially Dictyota, Lobophora and Halimeda while the most abundant macroalgae at reef crests were Halimeda and Amphiroa. Urchin densities were negatively and positively correlated with mean coverage of macroalgae and crustose coralline algae, respectively, when analyzing data pooled across all sites, but not with data from separate habitats (specially reef crest), suggesting, along with historical fish biomass, that shallow reef community structure is being shaped by the synergistic action of other factors (e.g. fish grazing) rather than the influence of Diadema alone. However, we observed clear signs of Diadema grazing at reef crests and decreased macroalgal cover according to 2001 data, what suggest that grazing intensity at this habitat increased at the same time that Diadema recruitment began to be noticeable. Furthermore, the excessive abundance of macroalgae at reef slopes and the scarcity of crustose coralline algae seems to be due by the almost complete absence of D. antillarum at mid depth reefs, where local densities of this urchin were

  20. AMPHIBIAN POPULATION DYNAMICS

    Science.gov (United States)

    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...

  1. Africa population dynamics

    NARCIS (Netherlands)

    Akinyoade, A.; Damen, J.C.M.; Dietz, A.J.; Kilama, B.; Omme, van G.

    2014-01-01

    Africa's population has grown extremely rapidly over the last fifty years from 289 million inhabitants in 1961 to more than 1 billion today. This is a growth rate of 350% in just half a century and the number of urban residents has increased even more quickly: from 65 million in 1960 to 460 million

  2. Optimizing algal cultivation & productivity : an innovative, multidiscipline, and multiscale approach.

    Energy Technology Data Exchange (ETDEWEB)

    Murton, Jaclyn K.; Hanson, David T. (University of New Mexico, Albuquerque, NM); Turner, Tom (University of New Mexico, Albuquerque, NM); Powell, Amy Jo; James, Scott Carlton (Sandia National Laboratories, Livermore, CA); Timlin, Jerilyn Ann; Scholle, Steven (University of New Mexico, Albuquerque, NM); August, Andrew (Sandia National Laboratories, Livermore, CA); Dwyer, Brian P.; Ruffing, Anne; Jones, Howland D. T.; Ricken, James Bryce; Reichardt, Thomas A. (Sandia National Laboratories, Livermore, CA)

    2010-04-01

    Progress in algal biofuels has been limited by significant knowledge gaps in algal biology, particularly as they relate to scale-up. To address this we are investigating how culture composition dynamics (light as well as biotic and abiotic stressors) describe key biochemical indicators of algal health: growth rate, photosynthetic electron transport, and lipid production. Our approach combines traditional algal physiology with genomics, bioanalytical spectroscopy, chemical imaging, remote sensing, and computational modeling to provide an improved fundamental understanding of algal cell biology across multiple cultures scales. This work spans investigations from the single-cell level to ensemble measurements of algal cell cultures at the laboratory benchtop to large greenhouse scale (175 gal). We will discuss the advantages of this novel, multidisciplinary strategy and emphasize the importance of developing an integrated toolkit to provide sensitive, selective methods for detecting early fluctuations in algal health, productivity, and population diversity. Progress in several areas will be summarized including identification of spectroscopic signatures for algal culture composition, stress level, and lipid production enabled by non-invasive spectroscopic monitoring of the photosynthetic and photoprotective pigments at the single-cell and bulk-culture scales. Early experiments compare and contrast the well-studied green algae chlamydomonas with two potential production strains of microalgae, nannochloropsis and dunnaliella, under optimal and stressed conditions. This integrated approach has the potential for broad impact on algal biofuels and bioenergy and several of these opportunities will be discussed.

  3. Effects on the population dynamics of Brachionus rubens (Rotifera) caused by mercury and cadmium administered through medium and algal food Chlorella vulgaris%在培养基和食料中添加铅和镉对轮虫种群动态的影响

    Institute of Scientific and Technical Information of China (English)

    S.S.S.SARMA; Hilda Fabiola NUNEZ-CRUZ; S.NANDINI

    2005-01-01

    Due to industrial activities,heavy metal concentrations in aquatic systems of Mexico,are on the rise.Zooplankton,particularly rotifers,being sensitive and common components of freshwater,are widely used in ecotoxicological tests for establishing water quality criteria.Depending on the route of exposure (i.e.via medium or algal food),the toxicity of heavy metals varies.In the present study we evaluated the effect of cadmium and mercury exposed through medium and via algal food for the rotifer B.rubens.For both the heavy metals,we exposed rotifers via medium containing Chlorella at 0.5×106 cells/ml or fed daily on previously exposed (1,2 and 4 h) alga to the toxicants (using 5 times the value of LC50 for B.rubens).For cadmium toxicity through medium,we used 3 toxicant levels (0.1,0.2 and 0.4 mg/L) and for mercury,we used 0.005,0.010 and 0.015 mg/L.Based on the LC50,B.rubens was 24 times more sensitive to mercury (0.035±0.002 mg/L) than cadmium.At a concentration of 0.4 mg/L,cadmium through the medium caused increased lag phase of B.rubens.When grown on Chlorella exposed for different durations to cadmium,the rotifer density decreased with the increasing duration of algal exposure to the heavy metal.When mercury was used in the medium or via algal food,the trends in the population growth of B.rubens were similar to those for cadmium.An increase in heavy metal concentration in the medium resulted in a decrease of the rate of population increase per day (r).The r varied from 0.33 (in control) to 0.02 d-1 (in heavy metal treatment) depending on the mode of exposure though medium or via algal food[Acta Zoologica Sinica 51(1):46-52,2005].%由于工业活动的影响,墨西哥水体环境中的重金属浓度在上升.浮游动物,尤其是轮虫类,由于对环境变化十分敏感而且是淡水中的常见组成部分,因此被广泛用于生态毒理试验以确定水质标准.在不同的胁迫途径下(如通过培养基或食料),重金属的毒性是不同的.在

  4. Diversity and dynamics of algal Megaviridae members during a harmful brown tide caused by the pelagophyte, Aureococcus anophagefferens.

    Science.gov (United States)

    Moniruzzaman, Mohammad; Gann, Eric R; LeCleir, Gary R; Kang, Yoonja; Gobler, Christopher J; Wilhelm, Steven W

    2016-05-01

    Many giant dsDNA algal viruses share a common ancestor with Mimivirus--one of the largest viruses, in terms of genetic content. Together, these viruses form the proposed 'Megaviridae' clade of nucleocytoplasmic large DNA viruses. To gauge Megaviridae diversity, we designed degenerate primers targeting the major capsid protein genes of algae-infecting viruses within this group and probed the clade's diversity during the course of a brown tide bloom caused by the harmful pelagophyte,Aureococcus anophagefferens We amplified target sequences in water samples from two distinct locations (Weesuck Creek and Quantuck Bay, NY) covering 12 weeks concurrent with the proliferation and demise of a bloom. In total, 475 amplicons clustered into 145 operational taxonomic units (OTUs) at 97% identity. One OTU contained 19 sequences with ≥97% identity to AaV, a member of the Megaviridae clade that infects A. anophagefferens, suggesting AaV was present during the bloom. Unifrac analysis showed clear temporal patterns in algal Megaviridae dynamics, with a shift in the virus community structure that corresponded to the Aureococcus bloom decline in both locations. Our data provide insights regarding the environmental relevance of algal Megaviridae members and raise important questions regarding their phylodynamics across different environmental gradients.

  5. Population dynamics in variable environments

    CERN Document Server

    Tuljapurkar, Shripad

    1990-01-01

    Demography relates observable facts about individuals to the dynamics of populations. If the dynamics are linear and do not change over time, the classical theory of Lotka (1907) and Leslie (1945) is the central tool of demography. This book addresses the situation when the assumption of constancy is dropped. In many practical situations, a population will display unpredictable variation over time in its vital rates, which must then be described in statistical terms. Most of this book is concerned with the theory of populations which are subject to random temporal changes in their vital rates, although other kinds of variation (e. g. , cyclical) are also dealt with. The central questions are: how does temporal variation work its way into a population's future, and how does it affect our interpretation of a population's past. The results here are directed at demographers of humans and at popula­ tion biologists. The uneven mathematical level is dictated by the material, but the book should be accessible to re...

  6. Models of ungulate population dynamics

    Directory of Open Access Journals (Sweden)

    L. L. Eberhardt

    1991-10-01

    Full Text Available A useful theory for analyzing ungulate population dynamics is available in the form of equations based on the work of A. J. Lotka. Because the Leslie matrix model yields identical results and is widely known, it is convenient to label the resulting equations as the "Lotka-Leslie" model. The approach is useful for assessing population trends and attempting to predict the outcomes of various management actions. A broad list of applications to large mammals, and two examples specific to caribou are presented with a simple spreadsheet approach to calculations.

  7. Population growth of the Cladoceran, Daphnia magna: a quantitative analysis of the effects of different algal food.

    Directory of Open Access Journals (Sweden)

    Jong-Yun Choi

    Full Text Available In this study, we examined the effects of two phytoplankton species, Chlorella vulgaris and Stephanodiscus hantzschii, on growth of the zooplankton Daphnia magna. Our experimental approach utilized stable isotopes to determine the contribution of food algae to offspring characteristics and to the size of adult D. magna individuals. When equal amounts of food algae were provided (in terms of carbon content, the size of individuals, adult zooplankton, and their offspring increased significantly following the provision of S. hantzschii, but not after the provision of C. vulgaris or of a combination of the two species. Offspring size was unaffected when C. vulgaris or a mixture of the two algal species was delivered, whereas providing only S. hantzschii increased the production of larger-sized offspring. Stable isotope analysis revealed significant assimilation of diatom-derived materials that was important for the growth of D. magna populations. Our results confirm the applicability of stable isotope approaches for clarifying the contribution of different food algae and elucidate the importance of food quality for growth of D. magna individuals and populations. Furthermore, we expect that stable isotope analysis will help to further precisely examine the contribution of prey to predators or grazers in controlled experiments.

  8. Nonlinear dynamics of interacting populations

    CERN Document Server

    Bazykin, Alexander D

    1998-01-01

    This book contains a systematic study of ecological communities of two or three interacting populations. Starting from the Lotka-Volterra system, various regulating factors are considered, such as rates of birth and death, predation and competition. The different factors can have a stabilizing or a destabilizing effect on the community, and their interplay leads to increasingly complicated behavior. Studying and understanding this path to greater dynamical complexity of ecological systems constitutes the backbone of this book. On the mathematical side, the tool of choice is the qualitative the

  9. Analysis of Population Dynamics in World Economy

    OpenAIRE

    Martin, Gress

    2011-01-01

    Population dynamics is an important topic in current world economy. The size and growth of population have an impact on economic growth and development of individual countries and vice versa, economic development influences demographic variables in a country. The aim of the article is to analyze historical development of world population, population stock change and relations between population stock change and economic development.

  10. Population Dynamics of Viral Inactivation

    Science.gov (United States)

    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.

  11. Phytoplankton dynamics with a special emphasis on harmful algal blooms in the Mar Piccolo of Taranto (Ionian Sea, Italy).

    Science.gov (United States)

    Caroppo, Carmela; Cerino, Federica; Auriemma, Rocco; Cibic, Tamara

    2016-07-01

    The response of phytoplankton assemblages to the closure of urban sewage outfalls (USOs) was examined for the Mar Piccolo of Taranto (Mediterranean Sea), a productive semi-enclosed coastal marine ecosystem devoted to shellfish farming. Phytoplankton dynamics were investigated in relation to environmental variables, with a particular emphasis on harmful algal blooms (HABs). Recent analyses evidenced a general reduction of the inorganic nutrient loads, except for nitrates and silicates. Also phytoplankton biomass (chlorophyll a) and abundances were characterized by a decrease of the values, except for the inner area of the basin (second inlet). The phytoplankton composition changed, with nano-sized species, indicators of oligotrophic conditions, becoming dominant over micro-sized species. If the closure of the USOs affected phytoplankton dynamics, however, it did not preserve the Mar Piccolo from HABs and anoxia crises. About 25 harmful species have been detected throughout the years, such as the potentially domoic acid producers Pseudo-nitzschia cf. galaxiae and P seudo-nitzschia cf. multistriata, identified for the first time in these waters. The presence of HABs represents a threat for human health and aquaculture. Urgent initiatives are needed to improve the communication with authorities responsible for environmental protection, economic development, and public health for a sustainable mussel culture in the Mar Piccolo.

  12. Population dynamics and population control of Galium aparine L.

    NARCIS (Netherlands)

    Weide, van der R.Y.

    1993-01-01

    The population biology of Galium aparine L. needs to be better understood, in order to be able to rationalize decisions about the short- and long-term control of this weed species for different cropping practices.A population dynamics model was developed to simulate the basic processes of the life c

  13. Population Dynamics of Genetic Regulatory Networks

    Science.gov (United States)

    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.

  14. Comparing models of Red Knot population dynamics

    Science.gov (United States)

    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.

  15. How Resource Phenology Affects Consumer Population Dynamics.

    Science.gov (United States)

    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.

  16. Curating Transient Population in Urban Dynamics System

    CERN Document Server

    Thakur, Gautam S; Stewart, Robert N; Urban, Marie L; Bhaduri, Budhendra L

    2016-01-01

    For past several decades, research efforts in population modelling has proven its efficacy in understanding the basic information about residential and commercial areas, as well as for the purposes of planning, development and improvement of the community as an eco-system. More or less, such efforts assume static nature of population distribution, in turn limited by the current ability to capture the dynamics of population change at a finer resolution of space and time. Fast forward today, more and more people are becoming mobile, traveling across borders impacting the nuts and bolts of our urban fabric. Unfortunately, our current efforts are being surpassed by the need to capture such transient population. It is becoming imperative to identify and define them, as well as measure their dynamics and interconnectedness. In this work, we intend to research urban population mobility patterns, gauge their transient nature, and extend our knowledge of their visited locations. We plan to achieve this by designing an...

  17. Population Dynamics and Air Pollution

    DEFF Research Database (Denmark)

    Flachs, Esben Meulengracht; Sørensen, Jan; Bønløkke, Jacob

    2013-01-01

    Objective. To explore how three different assumptions on demographics affect the health impact of Danish emitted air pollution in Denmark from 2005 to 2030, with health impact modeled from 2005 to 2050. Methods. Modeled air pollution from Danish sources was used as exposure in a newly developed......) a static year 2005 population, (2) morbidity and mortality fixed at the year 2005 level, or (3) an expected development. Results. The health impact of air pollution was estimated at 672,000, 290,000, and 280,000 lost life years depending on demographic assumptions and the corresponding social costs at 430.......4 M€, 317.5 M€, and 261.6 M€ through the modeled years 2005–2050. Conclusion. The modeled health impact of air pollution differed widely with the demographic assumptions, and thus demographics and assumptions on demographics played a key role in making health impact assessments on air pollution....

  18. A physical-biological coupled model for algal dynamics in lakes.

    Science.gov (United States)

    Franke, U; Hutter, K; Jöhnk, K

    1999-03-01

    A coupled model is presented for simulating physical and biological dynamics in fresh water lakes. The physical model rests upon the assumption that the turbulent kinetic energy in a water column of the lake is fully contained in a mixed layer of variable depth. Below this layer the mechanical energy content is assumed to vanish. Additionally, the horizontal currents are ignored. This one-dimensional two-layered model describes the internal conversion of the mechanical and thermal energy input from the atmosphere into an evolution of the mixed layer depth by entrainment and detrainment mechanisms. It is supposed to form the physical domain in which the simulation of the biological processes takes place. The biological model describes mathematically the typical properties of phyto- and zooplankton, their interactions and their response to the physical environment. This description then allows the study of the behaviour of Lagrangian clusters of virtual plankton that are subjected to such environments. The essence of the model is the dynamical simulation of an arbitrary number of nutrient limited phytoplankton species and one species of zooplankton. The members of the food web above and below affect the model only statically. The model is able to reproduce the typical progression of a predator-prey interaction between phyto- and zooplankton as well as the exploitative competition for nutrients between two phytoplankton species under grazing pressure of Daphnia. It suggests that the influence of the biological system on the physical system results in a weak increase of the surface temperature for coupled simulations, but a considerably higher seasonal thermocline in spring and a lower one in autumn.

  19. Population dynamical responses to climate change

    DEFF Research Database (Denmark)

    Forchhammer, Mads; Schmidt, Niels Martin; Høye, Toke Thomas

    2008-01-01

    it is well established that climatic as well as biological factors, in concert, form the mechanistic basis for our understanding of how populations develop over time and across space. Although this seemingly suggests simplicity, the climate-biology dichotomy of population dynamics embraces...... a bewildering number of interactions. For example, individuals within a population may compete for space and other resources and, being embedded in an ecosystem, individuals in any population may also interact with individuals of competing species as well as those from adjacent trophic levels. In principal...

  20. Detection, Diversity, and Population Dynamics of Waterborne Phytophthora ramorum Populations.

    Science.gov (United States)

    Eyre, C A; Garbelotto, M

    2015-01-01

    Sudden oak death, the tree disease caused by Phytophthora ramorum, has significant environmental and economic impacts on natural forests on the U.S. west coast, plantations in the United Kingdom, and in the worldwide nursery trade. Stream baiting is vital for monitoring and early detection of the pathogen in high-risk areas and is performed routinely; however, little is known about the nature of water-borne P. ramorum populations. Two drainages in an infested California forest were monitored intensively using stream-baiting for 2 years between 2009 and 2011. Pathogen presence was determined both by isolation and polymerase chain reaction (PCR) from symptomatic bait leaves. Isolates were analyzed using simple sequence repeats to study population dynamics and genetic structure through time. Isolation was successful primarily only during spring conditions, while PCR extended the period of pathogen detection to most of the year. Water populations were extremely diverse, and changed between seasons and years. A few abundant genotypes dominated the water during conditions considered optimal for aerial populations, and matched those dominant in aerial populations. Temporal patterns of genotypic diversification and evenness were identical among aerial, soil, and water populations, indicating that all three substrates are part of the same epidemiological cycle, strongly influenced by rainfall and sporulation on leaves. However, there was structuring between substrates, likely arising due to reduced selection pressure in the water. Additionally, water populations showed wholesale mixing of genotypes without the evident spatial autocorrelation present in leaf and soil populations.

  1. [Development and testing of theories of population dynamics]. First annual report

    Energy Technology Data Exchange (ETDEWEB)

    Murdoch, W.W.; Bence, J.R.; McCauley, E.; Nisbet, R.M.

    1990-03-15

    We report new analyses to test competing models of the Daphnia/algal interaction. Our model is good at predicting equilibrium algal densities, and if our new insights can account for stability in this system across a wide range of natural environments, this may contribute to understanding predator-prey dynamics in general.

  2. Population dynamics in an intermittent refuge

    Science.gov (United States)

    Colombo, E. H.; Anteneodo, C.

    2016-10-01

    Population dynamics is constrained by the environment, which needs to obey certain conditions to support population growth. We consider a standard model for the evolution of a single species population density, which includes reproduction, competition for resources, and spatial spreading, while subject to an external harmful effect. The habitat is spatially heterogeneous, there existing a refuge where the population can be protected. Temporal variability is introduced by the intermittent character of the refuge. This scenario can apply to a wide range of situations, from a laboratory setting where bacteria can be protected by a blinking mask from ultraviolet radiation, to large-scale ecosystems, like a marine reserve where there can be seasonal fishing prohibitions. Using analytical and numerical tools, we investigate the asymptotic behavior of the total population as a function of the size and characteristic time scales of the refuge. We obtain expressions for the minimal size required for population survival, in the slow and fast time scale limits.

  3. Interactions between algal-bacterial populations and trace metals in fjord surface waters during a nutrient stimulated summer bloom

    DEFF Research Database (Denmark)

    Muller, F.; Larsen, A.; Stedmon, C.;

    2005-01-01

    this period, the weaker Cu-binding ligands appeared to have the same source or production process as the proteinlike fluorophores detected in these coastal waters. Zinc speciation was controlled by complexation with a single class of organic ligands that appeared to be released inadvertently upon the death......We examined how variations in algal-bacterial community structure relate to Cu, Zn, and Mn speciation during a diatom-rich bloom that was induced by daily additions of inorganic macronutrients to fjord waters in August 2002. The experiments were carried out in 11-m3 floating mesocosm bags deployed...... and/or grazing of phytoplankton. Labile manganese fluctuations were inversely synchronized with the abundance of heterotrophic bacteria until the coastal waters experienced a massive rain event on day 17 of the experiment. The rainfall, which was a source of nitrogen and micronutrients, appeared...

  4. Towards a Population Dynamics Theory for Evolutionary Computing: Learning from Biological Population Dynamics in Nature

    Science.gov (United States)

    Ma, Zhanshan (Sam)

    In evolutionary computing (EC), population size is one of the critical parameters that a researcher has to deal with. Hence, it was no surprise that the pioneers of EC, such as De Jong (1975) and Holland (1975), had already studied the population sizing from the very beginning of EC. What is perhaps surprising is that more than three decades later, we still largely depend on the experience or ad-hoc trial-and-error approach to set the population size. For example, in a recent monograph, Eiben and Smith (2003) indicated: "In almost all EC applications, the population size is constant and does not change during the evolutionary search." Despite enormous research on this issue in recent years, we still lack a well accepted theory for population sizing. In this paper, I propose to develop a population dynamics theory forEC with the inspiration from the population dynamics theory of biological populations in nature. Essentially, the EC population is considered as a dynamic system over time (generations) and space (search space or fitness landscape), similar to the spatial and temporal dynamics of biological populations in nature. With this conceptual mapping, I propose to 'transplant' the biological population dynamics theory to EC via three steps: (i) experimentally test the feasibility—whether or not emulating natural population dynamics improves the EC performance; (ii) comparatively study the underlying mechanisms—why there are improvements, primarily via statistical modeling analysis; (iii) conduct theoretical analysis with theoretical models such as percolation theory and extended evolutionary game theory that are generally applicable to both EC and natural populations. This article is a summary of a series of studies we have performed to achieve the general goal [27][30]-[32]. In the following, I start with an extremely brief introduction on the theory and models of natural population dynamics (Sections 1 & 2). In Sections 4 to 6, I briefly discuss three

  5. Extinction rate fragility in population dynamics.

    Science.gov (United States)

    Khasin, M; Dykman, M I

    2009-08-01

    Population extinction is of central interest for population dynamics. It may occur from a large rare fluctuation. We find that, in contrast to related large-fluctuation effects like noise-induced interstate switching, quite generally extinction rates in multipopulation systems display fragility, where the height of the effective barrier to be overcome in the fluctuation depends on the system parameters nonanalytically. We show that one of the best-known models of epidemiology, the susceptible-infectious-susceptible model, is fragile to total population fluctuations.

  6. Dispersive models describing mosquitoes’ population dynamics

    Science.gov (United States)

    Yamashita, W. M. S.; Takahashi, L. T.; Chapiro, G.

    2016-08-01

    The global incidences of dengue and, more recently, zica virus have increased the interest in studying and understanding the mosquito population dynamics. Understanding this dynamics is important for public health in countries where climatic and environmental conditions are favorable for the propagation of these diseases. This work is based on the study of nonlinear mathematical models dealing with the life cycle of the dengue mosquito using partial differential equations. We investigate the existence of traveling wave solutions using semi-analytical method combining dynamical systems techniques and numerical integration. Obtained solutions are validated through numerical simulations using finite difference schemes.

  7. Algal biofuels.

    Science.gov (United States)

    Razeghifard, Reza

    2013-11-01

    The world is facing energy crisis and environmental issues due to the depletion of fossil fuels and increasing CO2 concentration in the atmosphere. Growing microalgae can contribute to practical solutions for these global problems because they can harvest solar energy and capture CO2 by converting it into biofuel using photosynthesis. Microalgae are robust organisms capable of rapid growth under a variety of conditions including in open ponds or closed photobioreactors. Their reduced biomass compounds can be used as the feedstock for mass production of a variety of biofuels. As another advantage, their ability to accumulate or secrete biofuels can be controlled by changing their growth conditions or metabolic engineering. This review is aimed to highlight different forms of biofuels produced by microalgae and the approaches taken to improve their biofuel productivity. The costs for industrial-scale production of algal biofuels in open ponds or closed photobioreactors are analyzed. Different strategies for photoproduction of hydrogen by the hydrogenase enzyme of green algae are discussed. Algae are also good sources of biodiesel since some species can make large quantities of lipids as their biomass. The lipid contents for some of the best oil-producing strains of algae in optimized growth conditions are reviewed. The potential of microalgae for producing petroleum related chemicals or ready-make fuels such as bioethanol, triterpenic hydrocarbons, isobutyraldehyde, isobutanol, and isoprene from their biomass are also presented.

  8. Population mixture model for nonlinear telomere dynamics

    Science.gov (United States)

    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.

  9. Galactic civilizations - Population dynamics and interstellar diffusion

    Science.gov (United States)

    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.

  10. A dynamic network in a dynamic population: asymptotic properties

    CERN Document Server

    Britton, Tom; Turova, Tatyana

    2011-01-01

    We derive asymptotic properties for a stochastic dynamic network model in a stochastic dynamic population. In the model, nodes give birth to new nodes until they die, each node being equipped with a social index given at birth. During the life of a node it creates edges to other nodes, nodes with high social index at higher rate, and edges disappear randomly in time. For this model we derive criterion for when a giant connected component exists after the process has evolved for a long period of time, assuming the node population grows to infinity. We also obtain an explicit expression for the degree correlation $\\rho$ (of neighbouring nodes) which shows that $\\rho$ is always positive irrespective of parameter values in one of the two treated submodels, and may be either positive or negative in the other model, depending on the parameters.

  11. Population Code Dynamics in Categorical Perception.

    Science.gov (United States)

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

    2016-03-03

    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.

  12. Nonlocal Crowd Dynamics Models for several Populations

    CERN Document Server

    Colombo, Rinaldo M

    2011-01-01

    This paper develops the basic analytical theory related to some recently introduced crowd dynamics models. Where well posedness was known only locally in time, it is here extended to all of $\\reali^+$. The results on the stability with respect to the equations are improved. Moreover, here the case of several populations is considered, obtaining the well posedness of systems of multi-D non-local conservation laws. The basic analytical tools are provided by the classical Kruzkov theory of scalar conservation laws in several space dimensions.

  13. NONLOCAL CROWD DYNAMICS MODELS FOR SEVERAL POPULATIONS

    Institute of Scientific and Technical Information of China (English)

    Rinaldo M. Colombo; Magali Lécureux-Mercier

    2012-01-01

    This paper develops the basic analytical theory related to some recently introduced crowd dynamics models.Where well posedness was known only locally in time,it is here extended to all of R+.The results on the stability with respect to the equations are improved.Moreover,here the case of several populations is considered,obtaining the well posedness of systems of multi-D non-local conservation laws.The basic analytical tools are provided by the classical Kru(z)kov theory of scalar conservation laws in several space dimensions.

  14. A population dynamics approach to biological aging

    Science.gov (United States)

    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. [Population dynamics and development in the Caribbean].

    Science.gov (United States)

    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

  16. Algal functional annotation tool

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, D. [UCLA; Casero, D. [UCLA; Cokus, S. J. [UCLA; Merchant, S. S. [UCLA; Pellegrini, M. [UCLA

    2012-07-01

    The Algal Functional Annotation Tool is a web-based comprehensive analysis suite integrating annotation data from several pathway, ontology, and protein family databases. The current version provides annotation for the model alga Chlamydomonas reinhardtii, and in the future will include additional genomes. The site allows users to interpret large gene lists by identifying associated functional terms, and their enrichment. Additionally, expression data for several experimental conditions were compiled and analyzed to provide an expression-based enrichment search. A tool to search for functionally-related genes based on gene expression across these conditions is also provided. Other features include dynamic visualization of genes on KEGG pathway maps and batch gene identifier conversion.

  17. Genetic diversity of Ulva prolifera population in Qingdao coastal water during the green algal blooms revealed by microsatellite.

    Science.gov (United States)

    Li, Yue; Huang, Hong-Jia; Li, Hongye; Liu, Jiesheng; Yang, Weidong

    2016-10-15

    Green tides have occurred in Qingdao coast in China for seven consecutive years from 2007 to 2013. To provide information on the genetic structure of these blooms, 210 free-floating green algae samples isolated from the green tide in Qingdao coast on June 19, 2013 were identified based on the ITS, rbcL and 5S sequence, and genetic diversity was investigated by microsatellite markers. According to ITS, rbcL and 5S sequence, all the 210 samples belonged to Ulva prolifera. Nei's genetic diversity and Shannon index estimated using eight microsatellite markers indicated that the genetic diversity of U. prolifera population within Qingdao's green bloom in 2013 was low. Taking into account previous reports about life history and physiology of U. prolifera, we proposed that the limited origin area of the free-floating biomass and asexual reproduction of U. prolifera might be responsible for the lower diversity of free floating U. prolifera.

  18. Population dynamics of species-rich ecosystems: the mixture of matrix population models approach

    DEFF Research Database (Denmark)

    Mortier, Frédéric; Rossi, Vivien; Guillot, Gilles;

    2013-01-01

    Matrix population models are widely used to predict population dynamics, but when applied to species-rich ecosystems with many rare species, the small population sample sizes hinder a good fit of species-specific models. This issue can be overcome by assigning species to groups to increase the size...... species with similar population dynamics....

  19. Uncovering the Complex Transcriptome Response of Mytilus chilensis against Saxitoxin: Implications of Harmful Algal Blooms on Mussel Populations

    Science.gov (United States)

    Detree, Camille; Núñez-Acuña, Gustavo; Roberts, Steven; Gallardo-Escárate, Cristian

    2016-01-01

    Saxitoxin (STX), a principal phycotoxin contributing to paralytic shellfish poisoning, is largely produced by marine microalgae of the genus Alexandrium. This toxin affects a wide range of species, inducing massive deaths in fish and other marine species. However, marine bivalves can resist and accumulate paralytic shellfish poisons. Despite numerous studies on the impact of STX in marine bivalves, knowledge regarding STX recognition at molecular level by benthic species remains scarce. Therefore, the aim of this study was to identify novel genes that interact with STX in the Chilean mussel Mytilus chilensis. For this, RNA-seq and RT-qPCR approaches were used to evaluate the transcriptomic response of M. chilensis to a purified STX as well as in vivo Alexandrium catenella exposure. Approximately 800 million reads were assembled, generating 138,883 contigs that were blasted against the UniProt Mollusca database. Pattern Recognition Receptors (PRRs) involved in mussel immunity, such as Toll-like receptors, tumor necrosis factor receptors, and scavenger-like receptors were found to be strongly upregulated at 8 and 16 h post-STX injection. These results suggest an involvement of PRRs in the response to STX, as well as identifying potential, novel STX-interacting receptors in this Chilean mussel. This study is the first transcriptomic overview of the STX-response in the edible species M. chilensis. However, the most significant contribution of this work is the identification of immune receptors and pathways potentially involved in the recognition and defense against STX’s toxicity and its impact of harmful algae blooms on wild and cultivated mussel populations. PMID:27764234

  20. Occupation Dynamics and Impacts of Damselfish Territoriality on Recovering Populations of the Threatened Staghorn Coral, Acropora cervicornis.

    Science.gov (United States)

    Schopmeyer, Stephanie A; Lirman, Diego

    2015-01-01

    Large-scale coral reef restoration is needed to help recover structure and function of degraded coral reef ecosystems and mitigate continued coral declines. In situ coral propagation and reef restoration efforts have scaled up significantly in past decades, particularly for the threatened Caribbean staghorn coral, Acropora cervicornis, but little is known about the role that native competitors and predators, such as farming damselfishes, have on the success of restoration. Steep declines in A. cervicornis abundance may have concentrated the negative impacts of damselfish algal farming on a much lower number of coral prey/colonies, thus creating a significant threat to the persistence and recovery of depleted coral populations. This is the first study to document the prevalence of resident damselfishes and negative effects of algal lawns on A. cervicornis along the Florida Reef Tract (FRT). Impacts of damselfish lawns on A. cervicornis colonies were more prevalent (21.6% of colonies) than those of other sources of mortality (i.e., disease (1.6%), algal/sponge overgrowth (5.6%), and corallivore predation (7.9%)), and damselfish activities caused the highest levels of tissue mortality (34.6%) among all coral stressors evaluated. The probability of damselfish occupation increased as coral colony size and complexity increased and coral growth rates were significantly lower in colonies with damselfish lawns (15.4 vs. 29.6 cm per year). Reduced growth and mortality of existing A. cervicornis populations may have a significant effect on population dynamics by potentially reducing important genetic diversity and the reproductive potential of depleted populations. On a positive note, however, the presence of resident damselfishes decreased predation by other corallivores, such as Coralliophila and Hermodice, and may offset some negative impacts caused by algal farming. While most negative impacts of damselfishes identified in this study affected large individual colonies and

  1. Occupation Dynamics and Impacts of Damselfish Territoriality on Recovering Populations of the Threatened Staghorn Coral, Acropora cervicornis.

    Directory of Open Access Journals (Sweden)

    Stephanie A Schopmeyer

    Full Text Available Large-scale coral reef restoration is needed to help recover structure and function of degraded coral reef ecosystems and mitigate continued coral declines. In situ coral propagation and reef restoration efforts have scaled up significantly in past decades, particularly for the threatened Caribbean staghorn coral, Acropora cervicornis, but little is known about the role that native competitors and predators, such as farming damselfishes, have on the success of restoration. Steep declines in A. cervicornis abundance may have concentrated the negative impacts of damselfish algal farming on a much lower number of coral prey/colonies, thus creating a significant threat to the persistence and recovery of depleted coral populations. This is the first study to document the prevalence of resident damselfishes and negative effects of algal lawns on A. cervicornis along the Florida Reef Tract (FRT. Impacts of damselfish lawns on A. cervicornis colonies were more prevalent (21.6% of colonies than those of other sources of mortality (i.e., disease (1.6%, algal/sponge overgrowth (5.6%, and corallivore predation (7.9%, and damselfish activities caused the highest levels of tissue mortality (34.6% among all coral stressors evaluated. The probability of damselfish occupation increased as coral colony size and complexity increased and coral growth rates were significantly lower in colonies with damselfish lawns (15.4 vs. 29.6 cm per year. Reduced growth and mortality of existing A. cervicornis populations may have a significant effect on population dynamics by potentially reducing important genetic diversity and the reproductive potential of depleted populations. On a positive note, however, the presence of resident damselfishes decreased predation by other corallivores, such as Coralliophila and Hermodice, and may offset some negative impacts caused by algal farming. While most negative impacts of damselfishes identified in this study affected large individual

  2. Biotic Population Dynamics: Creative Biotic Patterns

    Science.gov (United States)

    Sabelli, Hector; Kovacevic, Lazar

    We present empirical studies and computer models of population dynamics that demonstrate creative features and we speculate that these creative processes may underline evolution. Changes in population size of lynx, muskrat, beaver, salmon, and fox display diversification, episodic changes in pattern, novelty, and evidence for nonrandom causation. These features of creativity characterize bios, and rule out random, periodic, chaotic, and random walk patterns. Biotic patterns are also demonstrated in time series generated with multi-agent predator-prey simulations. These results indicate that evolutionary processes are continually operating. In contrast to standard evolutionary theory (random variation, competition for scarce resources, selection by survival of the fittest, and directionless, meaningless evolution), we propose that biological evolution is a creative development from simple to complex in which (1) causal actions generate biological variation; (2) bipolar feedback (synergy and antagonism, abundance and scarcity) generates information (diversification, novelty and complexity); (3) connections (of molecules, genes, species) construct systems in which simple processes have priority for survival but complex processes acquire supremacy.

  3. Variability of phytoplankton absorption in the northern South China Sea: influence of the size structure and pigment composition of algal populations

    Institute of Scientific and Technical Information of China (English)

    WANG Guifen; CAO Wenxi; XU Dazhi; YANG Yuezhong

    2007-01-01

    Data from three cruises conducted in the Zhujiang River (ZR), coastal waters of Guangdong (CWGD) and the northern South China Sea (NSCS) during 2003 and 2004 were examined for assessing the relative importance of pigment composition and packaging effect in modifying the specific absorption coefficients of phytoplankton. The three survey regions differ widely in their phytoplankton community with large cells dominating the ZR and CWGD waters and small cells dominating the NSCS region. Variations in the size structure and the accessory pigments have much effect on the chlorophyll a-specific absorption coefficient of phytoplankton. The size index accounted for about 42% and 33% of the variation of the specific absorption coefficient at 440 and 675 nm, respectively. Using the multiple regression analysis approach, pigment concentrations for each sample were calculated. The accessory pigments other than chlorophyll a contribute to absorption mainly in the blue - to - green region of the spectrum and their absorptions account for about 44%, 43% and 53% on the average of the total phytoplankton absorption at 440 nm for the ZR, CWGD and NSCS regions. Among the accessory pigments, the photosynthetic carotenoids (noted PSC) play a dominant role in the ZR and CWGD waters, while in the NSCS the nonphotosynthetic carotenoids (noted PPG) as well as PSC have important contributions. Because the variations of both the size structure and accessory pigments in algal populations contributed to the variability of the specific absorption coefficient in the study regions, these factors may be considered explicitly in future bio - optical algorithms to derive chlorophyll a concentration more accurately.

  4. Biological control of harmful algal blooms: A modelling study

    Science.gov (United States)

    Solé, Jordi; Estrada, Marta; Garcia-Ladona, Emilio

    2006-07-01

    A multispecies dynamic simulation model (ERSEM) was used to examine the influence of allelopathic and trophic interactions causing feeding avoidance by predators, on the formation of harmful algal blooms, under environmental scenarios typical of a Mediterranean harbour (Barcelona). The biological state variables of the model included four functional groups of phytoplankton (diatoms, toxic and non-toxic flagellates and picophytoplankton), heterotrophic flagellates, micro- and mesozooplankton and bacteria. The physical-chemical forcing (irradiance, temperature and major nutrient concentrations) was based on an actual series of measurements taken along a year cycle in the Barcelona harbour. In order to evaluate potential effects of advection, some runs were repeated after introducing a biomass loss term. Numerical simulations showed that allelopathic effects of a toxic alga on a non-toxic but otherwise similar competitor did not have appreciable influence on the dynamics of the system. However, induction of avoidance of the toxic alga by predators, which resulted on increased predation pressure on other algal groups had a significant effect on the development of algal and predator populations. The presence of advection overrided the effect of these interactions and only allowed organisms with sufficiently high potential growth rates to thrive.

  5. Perturbation analysis of transient population dynamics using matrix projection models

    DEFF Research Database (Denmark)

    Stott, Iain

    2016-01-01

    Non-stable populations exhibit short-term transient dynamics: size, growth and structure that are unlike predicted long-term asymptotic stable, stationary or equilibrium dynamics. Understanding transient dynamics of non-stable populations is important for designing effective population management...... strategies, predicting the responses of populations to environmental change or disturbance, and understanding population processes and life-history evolution in variable environments. Transient perturbation analyses are vital tools for achieving these aims. They assess how transient dynamics are affected...... of model being analysed, the perturbation structure, the population response of interest, nonlinear response to perturbation, standardization for asymptotic dynamics, the initial population structure, and the time frame of interest. I discuss these with reference to the application of transient...

  6. Population dynamic theory of size-dependent cannibalism

    NARCIS (Netherlands)

    Claessen, D.; de Roos, A.M.; Persson, L.

    2004-01-01

    Cannibalism is characterized by four aspects: killing victims, gaining energy from victims, size-dependent interactions and intraspecific competition. In this review of mathematical models of cannibalistic populations, we relate the predicted population dynamic consequences of cannibalism to its fou

  7. Dynamics of genome rearrangement in bacterial populations.

    Directory of Open Access Journals (Sweden)

    Aaron E Darling

    represent the 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.

  8. Water quality and algal community dynamics of three deepwater lakes in Minnesota utilizing CE-QUAL-W2 models

    Science.gov (United States)

    Smith, Erik A.; Kiesling, Richard L.; Galloway, Joel M.; Ziegeweid, Jeffrey R.

    2014-01-01

    Water quality, habitat, and fish in Minnesota lakes will potentially be facing substantial levels of stress in the coming decades primarily because of two stressors: (1) land-use change (urban and agricultural) and (2) climate change. Several regional and statewide lake modeling studies have identified the potential linkages between land-use and climate change on reductions in the volume of suitable lake habitat for coldwater fish populations. In recent years, water-resource scientists have been making the case for focused assessments and monitoring of sentinel systems to address how these stress agents change lakes over the long term. Currently in Minnesota, a large-scale effort called “Sustaining Lakes in a Changing Environment” is underway that includes a focus on monitoring basic watershed, water quality, habitat, and fish indicators of 24 Minnesota sentinel lakes across a gradient of ecoregions, depths, and nutrient levels. As part of this effort, the U.S. Geological Survey, in cooperation with the Minnesota Department of Natural Resources, developed predictive water quality models to assess water quality and habitat dynamics of three select deepwater lakes in Minnesota. The three lakes (Lake Carlos in Douglas County, Elk Lake in Clearwater County, and Trout Lake in Cook County) were assessed under recent (2010–11) meteorological conditions. The three selected lakes contain deep, coldwater habitats that remain viable during the summer months for coldwater fish species. Hydrodynamics and water-quality characteristics for each of the three lakes were simulated using the CE-QUAL-W2 model, which is a carbon-based, laterally averaged, two-dimensional water-quality model. The CE-QUAL-W2 models address the interaction between nutrient cycling, primary production, and trophic dynamics to predict responses in the distribution of temperature and oxygen in lakes. The CE-QUAL-W2 models for all three lakes successfully predicted water temperature, on the basis of the

  9. Evolutionary dynamics with fluctuating population sizes and strong mutualism

    Science.gov (United States)

    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.

  10. Bounds on the dynamics of sink populations with noisy immigration

    DEFF Research Database (Denmark)

    Eager, Eric Alan; Guiver, Chris; Hodgson, Dave

    2014-01-01

    Sink populations are doomed to decline to extinction in the absence of immigration. The dynamics of sink populations are not easily modelled using the standard framework of per capita rates of immigration, because numbers of immigrants are determined by extrinsic sources (for example, source...... populations, or population managers). Here we appeal to a systems and control framework to place upper and lower bounds on both the transient and future dynamics of sink populations that are subject to noisy immigration. Immigration has a number of interpretations and can fit a wide variety of models found...

  11. Synchronization Phenomena in an Array of Population Dynamic Systems

    DEFF Research Database (Denmark)

    Postnov, D.E.; Balanov, A.G.; Mosekilde, Erik

    1998-01-01

    The paper applies continuation methods to examine synchronization phenomena that can arise in a cascaded system of population dynamic models. The individual model describes a bacterial population interacting with a population of viruses that attack the cells. Coupling between the subsystems...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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…

  14. Algal Supply System Design - Harmonized Version

    Energy Technology Data Exchange (ETDEWEB)

    Jared Abodeely; Daniel Stevens; Allison Ray; Debor

    2013-03-01

    The objective of this design report is to provide an assessment of current technologies used for production, dewatering, and converting microalgae cultivated in open-pond systems to biofuel. The original draft design was created in 2011 and has subsequently been brought into agreement with the DOE harmonized model. The design report extends beyond this harmonized model to discuss some of the challenges with assessing algal production systems, including the ability to (1) quickly assess alternative algal production system designs, (2) assess spatial and temporal variability, and (3) perform large-scale assessments considering multiple scenarios for thousands of potential sites. The Algae Logistics Model (ALM) was developed to address each of these limitations of current modeling efforts to enable assessment of the economic feasibility of algal production systems across the United States. The (ALM) enables (1) dynamic assessments using spatiotemporal conditions, (2) exploration of algal production system design configurations, (3) investigation of algal production system operating assumptions, and (4) trade-off assessments with technology decisions and operating assumptions. The report discusses results from the ALM, which is used to assess the baseline design determined by harmonization efforts between U.S. DOE national laboratories. Productivity and resource assessment data is provided by coupling the ALM with the Biomass Assessment Tool developed at PNNL. This high-fidelity data is dynamically passed to the ALM and used to help better understand the impacts of spatial and temporal constraints on algal production systems by providing a cost for producing extracted algal lipids annually for each potential site.

  15. Statistical Dynamics of Regional Populations and Economies

    CERN Document Server

    Huo, Jie; Hao, Rui; Wang, Peng

    2016-01-01

    A practical statistical analysis on the regional populations and GDPs of China is conducted. The result shows that the distribution of the populations and that of the GDPs obeys the shifted power law, respectively. To understand these characteristics, a generalized Langevin equation describing variation of population is proposed based on the correlation between population and GDP as well as the random fluctuations of the related factors. The equation is transformed into the Fokker-Plank equation, and the solution demonstrates a transform of population distribution from the normal Gaussian distribution to a shifted power law. It also suggests a critical point of time at which the transform occurs. The shifted power law distribution in the supercritical situation is qualitatively in accordance with the practical result. The distribution of the GDPs is derived based on the Cobb-Douglas production function, and presents a change from a shifted power law to the Gaussian distribution. This result indicates that the...

  16. Role of finite populations in determining evolutionary dynamics

    Science.gov (United States)

    Ray, Tane S.; Payne, Karl A.; Moseley, L. Leo

    2008-02-01

    The connection between the finite size of an evolving population and its dynamical behavior is examined through analytical and computational studies of a simple model of evolution. The infinite population limit of the model is shown to be governed by a special case of the quasispecies equations. A flat fitness landscape yields identical results for the dynamics of infinite and finite populations. On the other hand, a monotonically increasing fitness landscape shows “epochs” in the dynamics of finite populations that become more pronounced as the rate of mutation decreases. The details of the dynamics are profoundly different for any two simulation runs in that events arising from the stochastic noise in the pseudorandom number sequence are amplified. As the population size is increased or, equivalently, the mutation rate is increased, these epochs become smaller but do not entirely disappear.

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

    Science.gov (United States)

    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.

  18. Phase-space approach to multi-population dynamics

    CERN Document Server

    Budko, Neil V

    2015-01-01

    Simultaneous deterministic dynamics of multiple populations described by a large set of ODE's is considered in the phase space of population sizes and ODE's parameters. The problem is formulated as a multidimensional phase-space conservation law and is solved explicitly for non-interacting multi-population models. Solutions for populations competing for a limited resource and populations with migration are obtained by simple iterative methods. The proposed approach also allows considering phase-space interaction between populations, which is intractable by other methods.

  19. Population dynamics of the king rails, Rallus elegans

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report describes the findings of research conducted by a team of biologists from East Carolina University. The project ‘Population Dynamics of the King Rail,...

  20. A linear model of population dynamics

    Science.gov (United States)

    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).

  1. Real-Time Bioluminescent Tracking of Cellular Population Dynamics

    OpenAIRE

    Close, Dan; Xu, Tingling; Ripp, Steven; Sayler, Gary

    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 pop...

  2. The effects of mixed algal diets on population growth, egg productivity and nutritional profiles in cyclopoid copepods (Thermocyclops hyalinus and Mesocyclops aspericornis

    Directory of Open Access Journals (Sweden)

    Kumar Vidhya

    2014-03-01

    Full Text Available This experiment was carried out to evaluate the effect of mixed algal diet on dietary profiles of copepods. The microalgae like Spirulina platensis, Chlorella vulgaris and Azolla pinnata were mass cultured in artificial medium for a period of 20 days, cells are harvested, dried, powdered and used as feed. The small freshwater cyclopoids Thermocyclops hyalinus were compared to Mesocyclops aspericornis a species of copepod genera commonly preferred by most of the fish larvae. Both species are easily maintained in culture, when fed with mixed algal diets of equal ratios (1:1:1. Biochemical composition, egg production ratios, growth performance and fatty acids profile of the two different species were analyzed after an experimental period of 15 days, all the nutritional values were found to be high and statistically variable. On the basis of biochemical composition, egg production ratio, growth performance, amino acids and fatty acids profile it is found that M. aspericornis was the suitable candidate for larval fish diets.

  3. Stage-Structured Population Dynamics of AEDES AEGYPTI

    Science.gov (United States)

    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.

  4. Passivity analysis of higher order evolutionary dynamics and population games

    KAUST Repository

    Mabrok, Mohamed

    2017-01-05

    Evolutionary dynamics describe how the population composition changes in response to the fitness levels, resulting in a closed-loop feedback system. Recent work established a connection between passivity theory and certain classes of population games, namely so-called “stable games”. In particular, it was shown that a combination of stable games and (an analogue of) passive evolutionary dynamics results in stable convergence to Nash equilibrium. This paper considers the converse question of necessary conditions for evolutionary dynamics to exhibit stable behaviors for all generalized stable games. Using methods from robust control analysis, we show that if an evolutionary dynamic does not satisfy a passivity property, then it is possible to construct a generalized stable game that results in instability. The results are illustrated on selected evolutionary dynamics with particular attention to replicator dynamics, which are also shown to be lossless, a special class of passive systems.

  5. Contributions of Alan C. Lazer to mathematical population dynamics

    Directory of Open Access Journals (Sweden)

    Chris Cosner

    2000-10-01

    Full Text Available This paper is a survey of the contributions that Professor Alan C. Lazer has made to the mathematical theory of population dynamics. Specific areas where Professor Lazer has made important contributions include time periodic population models with diffusion and nonautonomous models for many competing species.

  6. The frankincense tree of Ethiopia : ecology, productivity and population dynamics

    NARCIS (Netherlands)

    Eshete Wassie, A.

    2011-01-01

    Keywords: Boswellian papyrifera, Frankincense tree, matrix model, population dynamics,
    population bottleneck, tapping. Combretum – Terminalia woodlands and Acacia – Commiphora woodlands are the two
    dominant vegetation types that cover large parts of the dry land areas in Eth

  7. AN INVARIANCE PRINCIPLE IN LARGE POPULATION STOCHASTIC DYNAMIC GAMES

    Institute of Scientific and Technical Information of China (English)

    Minyi HUANG; Peter E. CAINES; Roland P. MALHAM(E)

    2007-01-01

    We study large population stochastic dynamic games where the so-called Nash certainty equivalence based control laws are implemented by the individual players. We first show a martingale property for the limiting control problem of a single agent and then perform averaging across the population; this procedure leads to a constant value for the martingale which shows an invariance property of the population behavior induced by the Nash strategies.

  8. feedback between population and evolutionary dynamics determines the fate of social microbial populations.

    Directory of Open Access Journals (Sweden)

    Alvaro Sanchez

    Full Text Available The evolutionary spread of cheater strategies can destabilize populations engaging in social cooperative behaviors, thus demonstrating that evolutionary changes can have profound implications for population dynamics. At the same time, the relative fitness of cooperative traits often depends upon population density, thus leading to the potential for bi-directional coupling between population density and the evolution of a cooperative trait. Despite the potential importance of these eco-evolutionary feedback loops in social species, they have not yet been demonstrated experimentally and their ecological implications are poorly understood. Here, we demonstrate the presence of a strong feedback loop between population dynamics and the evolutionary dynamics of a social microbial gene, SUC2, in laboratory yeast populations whose cooperative growth is mediated by the SUC2 gene. We directly visualize eco-evolutionary trajectories of hundreds of populations over 50-100 generations, allowing us to characterize the phase space describing the interplay of evolution and ecology in this system. Small populations collapse despite continual evolution towards increased cooperative allele frequencies; large populations with a sufficient number of cooperators "spiral" to a stable state of coexistence between cooperator and cheater strategies. The presence of cheaters does not significantly affect the equilibrium population density, but it does reduce the resilience of the population as well as its ability to adapt to a rapidly deteriorating environment. Our results demonstrate the potential ecological importance of coupling between evolutionary dynamics and the population dynamics of cooperatively growing organisms, particularly in microbes. Our study suggests that this interaction may need to be considered in order to explain intraspecific variability in cooperative behaviors, and also that this feedback between evolution and ecology can critically affect the

  9. feedback between population and evolutionary dynamics determines the fate of social microbial populations.

    Science.gov (United States)

    Sanchez, Alvaro; Gore, Jeff

    2013-01-01

    The evolutionary spread of cheater strategies can destabilize populations engaging in social cooperative behaviors, thus demonstrating that evolutionary changes can have profound implications for population dynamics. At the same time, the relative fitness of cooperative traits often depends upon population density, thus leading to the potential for bi-directional coupling between population density and the evolution of a cooperative trait. Despite the potential importance of these eco-evolutionary feedback loops in social species, they have not yet been demonstrated experimentally and their ecological implications are poorly understood. Here, we demonstrate the presence of a strong feedback loop between population dynamics and the evolutionary dynamics of a social microbial gene, SUC2, in laboratory yeast populations whose cooperative growth is mediated by the SUC2 gene. We directly visualize eco-evolutionary trajectories of hundreds of populations over 50-100 generations, allowing us to characterize the phase space describing the interplay of evolution and ecology in this system. Small populations collapse despite continual evolution towards increased cooperative allele frequencies; large populations with a sufficient number of cooperators "spiral" to a stable state of coexistence between cooperator and cheater strategies. The presence of cheaters does not significantly affect the equilibrium population density, but it does reduce the resilience of the population as well as its ability to adapt to a rapidly deteriorating environment. Our results demonstrate the potential ecological importance of coupling between evolutionary dynamics and the population dynamics of cooperatively growing organisms, particularly in microbes. Our study suggests that this interaction may need to be considered in order to explain intraspecific variability in cooperative behaviors, and also that this feedback between evolution and ecology can critically affect the demographic fate of

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

    Science.gov (United States)

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

    2015-01-08

    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.

  11. Modelling the Dynamics of an Aedes albopictus Population

    CERN Document Server

    Basuki, Thomas Anung; Barbuti, Roberto; Maggiolo-Schettini, Andrea; Milazzo, Paolo; Rossi, Elisabetta; 10.4204/EPTCS.33.2

    2010-01-01

    We present a methodology for modelling population dynamics with formal means of computer science. This allows unambiguous description of systems and application of analysis tools such as simulators and model checkers. In particular, the dynamics of a population of Aedes albopictus (a species of mosquito) and its modelling with the Stochastic Calculus of Looping Sequences (Stochastic CLS) are considered. The use of Stochastic CLS to model population dynamics requires an extension which allows environmental events (such as changes in the temperature and rainfalls) to be taken into account. A simulator for the constructed model is developed via translation into the specification language Maude, and used to compare the dynamics obtained from the model with real data.

  12. Modelling the Dynamics of an Aedes albopictus Population

    Directory of Open Access Journals (Sweden)

    Thomas Anung Basuki

    2010-08-01

    Full Text Available We present a methodology for modelling population dynamics with formal means of computer science. This allows unambiguous description of systems and application of analysis tools such as simulators and model checkers. In particular, the dynamics of a population of Aedes albopictus (a species of mosquito and its modelling with the Stochastic Calculus of Looping Sequences (Stochastic CLS are considered. The use of Stochastic CLS to model population dynamics requires an extension which allows environmental events (such as changes in the temperature and rainfalls to be taken into account. A simulator for the constructed model is developed via translation into the specification language Maude, and used to compare the dynamics obtained from the model with real data.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    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.

  15. Interacting trophic forcing and the population dynamics of herring

    DEFF Research Database (Denmark)

    Lindegren, Martin; Ostman, Orjan; Gardmark, Anna

    2011-01-01

    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...

  16. Real-Time Bioluminescent Tracking of Cellular Population Dynamics

    Science.gov (United States)

    Close, Dan; Xu, Tingling; Ripp, Steven; Sayler, Gary

    2015-01-01

    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. PMID:24166372

  17. Real-Time Bioluminescent Tracking of Cellular Population Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Close, Dan [University of Tennessee, Knoxville (UTK); Sayler, Gary Steven [ORNL; Xu, Tingting [ORNL; Ripp, Steven Anthony [ORNL

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  19. Stochastic population dynamics of a montane ground-dwelling squirrel.

    Directory of Open Access Journals (Sweden)

    Jeffrey A Hostetler

    Full Text Available Understanding the causes and consequences of population fluctuations is a central goal of ecology. We used demographic data from a long-term (1990-2008 study and matrix population models to investigate factors and processes influencing the dynamics and persistence of a golden-mantled ground squirrel (Callospermophilus lateralis population, inhabiting a dynamic subalpine habitat in Colorado, USA. The overall deterministic population growth rate λ was 0.94±SE 0.05 but it varied widely over time, ranging from 0.45±0.09 in 2006 to 1.50±0.12 in 2003, and was below replacement (λ<1 for 9 out of 18 years. The stochastic population growth rate λ(s was 0.92, suggesting a declining population; however, the 95% CI on λ(s included 1.0 (0.52-1.60. Stochastic elasticity analysis showed that survival of adult females, followed by survival of juvenile females and litter size, were potentially the most influential vital rates; analysis of life table response experiments revealed that the same three life history variables made the largest contributions to year-to year changes in λ. Population viability analysis revealed that, when the influences of density dependence and immigration were not considered, the population had a high (close to 1.0 in 50 years probability of extinction. However, probability of extinction declined to as low as zero when density dependence and immigration were considered. Destabilizing effects of stochastic forces were counteracted by regulating effects of density dependence and rescue effects of immigration, which allowed our study population to bounce back from low densities and prevented extinction. These results suggest that dynamics and persistence of our study population are determined synergistically by density-dependence, stochastic forces, and immigration.

  20. Cumulant dynamics in a finite population linkage equilibrium theory

    CERN Document Server

    Rattray, M; Rattray, Magnus; Shapiro, Jonathan L.

    1999-01-01

    The evolution of a finite population at linkage equilibrium is described in terms of the dynamics of phenotype distribution cumulants. This provides a powerful method for describing evolutionary transients and we elucidate the relationship between the cumulant dynamics and the diffusion approximation. A separation of time-scales between the first and higher cumulants for low mutation rates is demonstrated in the diffusion limit and provides a significant simplification of the dynamical system. However, the diffusion limit may not be appropriate for strong selection as the standard Fisher-Wright model of genetic drift can break down in this case. Two novel examples of this effect are considered: we shown that the dynamics may depend on the number of loci under strong directional selection and that environmental variance results in a reduced effective population size. We also consider a simple model of a changing environment which cannot be described by a diffusion equation and we derive the optimal mutation ra...

  1. An individual-based model of zebrafish population dynamics accounting for energy dynamics.

    Directory of Open Access Journals (Sweden)

    Rémy Beaudouin

    Full Text Available 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.

  2. An age-structured population balance model for microbial dynamics

    Directory of Open Access Journals (Sweden)

    Duarte M.V.E.

    2003-01-01

    Full Text Available This work presents an age-structured population balance model (ASPBM for a bioprocess in a continuous stirred-tank fermentor. It relates the macroscopic properties and dynamic behavior of biomass to the operational parameters and microscopic properties of cells. Population dynamics is governed by two time- and age-dependent density functions for living and dead cells, accounting for the influence of substrate and dissolved oxygen concentrations on cell division, aging and death processes. The ASPBM described biomass and substrate oscillations in aerobic continuous cultures as experimentally observed. It is noteworthy that a small data set consisting of nonsegregated measurements was sufficient to adjust a complex segregated mathematical model.

  3. Competitive Lotka-Volterra Population Dynamics with Jumps

    CERN Document Server

    Bao, Jianhai; Yin, Geroge; Yuan, Chenggui

    2011-01-01

    This paper considers competitive Lotka-Volterra population dynamics with jumps. The contributions of this paper are as follows. (a) We show stochastic differential equation (SDE) with jumps associated with the model has a unique global positive solution; (b) We discuss the uniform boundedness of $p$th moment with $p>0$ and reveal the sample Lyapunov exponents; (c) Using a variation-of-constants formula for a class of SDEs with jumps, we provide explicit solution for 1-dimensional competitive Lotka-Volterra population dynamics with jumps, and investigate the sample Lyapunov exponent for each component and the extinction of our $n$-dimensional model.

  4. Locally dispersing populations in heterogeneous dynamic landscapes with spatiotemporal correlations. II. Habitat driven by voter dynamics.

    Science.gov (United States)

    Hiebeler, David E; Hill, Jack L

    2016-10-21

    We examine a spatially explicit population model on a dynamic landscape with suitable and unsuitable habitat driven by voter or contagion dynamics. We consider four cases, consisting of all combinations of local and global interactions for both population dispersal and habitat dynamics. For both local and global population dispersal, using local habitat dynamics always increases population density relative to the case with global habitat dynamics, due to the resulting segregation of habitat turnover, decrease in effective habitat turnover rate, and presence of stable habitat corridors. With global habitat dynamics, a population using local dispersal exhibits lower density than one with global dispersal due to local crowding as well as frequent disturbance due to habitat transitions. On the other hand, with local habitat dynamics, a population using local dispersal can exploit suitable habitat patches and use dynamic corridors to colonize new regions. The latter effect is not seen with static landscapes, where clustered habitat can lead to the isolation of suitable patches due to surrounding unsuitable habitat.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    Miller, David A; Clark, William R; Arnold, Stevan J; Bronikowski, Anne M

    2011-08-01

    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 (lambda(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 lambda(s). The magnitude of variation in the proportion of gravid females and its effect on lambda(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 lambda(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

  7. Workshop on Populations & Crowds: Dynamics, Disruptions and their Computational Models

    Science.gov (United States)

    2015-01-01

    behavior and, ultimately, what can be done to block contagion of hostile behavior in both population and crowd contexts. The workshop was organized at the...powerful in their ability to spread information and rapidly alter their collective behavior . Crowds can transition from loosely to tightly organized and...7 September, 2012 concentrating on organization , dynamics and disruption of populations and crowds. The purpose of this workshop was to bring

  8. The population dynamical consequences of density-dependent prophylaxis.

    Science.gov (United States)

    Reynolds, Jennifer J H; White, Andrew; Sherratt, Jonathan A; Boots, Mike

    2011-11-07

    When infectious disease transmission is density-dependent, the risk of infection will tend to increase with host population density. Since host defence mechanisms can be costly, individual hosts may benefit from increasing their investment in immunity in response to increasing population density. Such "density-dependent prophylaxis" (DDP) has now indeed been demonstrated experimentally in several species. However, it remains unclear how DDP will affect the population dynamics of the host-pathogen interaction, with previous theoretical work making conflicting predictions. We develop a general host-pathogen model and assess the role of DDP on the population dynamics. The ability of DDP to drive population cycles is critically dependent on the time delay between the change in density and the subsequent phenotypic change in the level of resistance. When the delay is absent or short, DDP destabilises the system. As the delay increases, its destabilising effect first diminishes and then DDP becomes increasingly stabilising. Our work highlights the significance of the time delay and suggests that it must be estimated experimentally or varied in theoretical investigations in order to understand the implications of DDP for the population dynamics of particular systems.

  9. Dynamical quorum sensing and clustering dynamics in a population of spatially distributed active rotators

    Science.gov (United States)

    Sakaguchi, Hidetsugu; Maeyama, Satomi

    2013-02-01

    A model of clustering dynamics is proposed for a population of spatially distributed active rotators. A transition from excitable to oscillatory dynamics is induced by the increase of the local density of active rotators. It is interpreted as dynamical quorum sensing. In the oscillation regime, phase waves propagate without decay, which generates an effectively long-range interaction in the clustering dynamics. The clustering process becomes facilitated and only one dominant cluster appears rapidly as a result of the dynamical quorum sensing. An exact localized solution is found to a simplified model equation, and the competitive dynamics between two localized states is studied numerically.

  10. Viral lysis of Phaeocystis pouchetii: implications for algal population dynamics and heterotrophic C, N and P cycling

    DEFF Research Database (Denmark)

    Haaber, Jakob Brandt Borup; Middelboe, Mathias

    2009-01-01

    and phosphorus mineralization. Lysis of P. pouchetii by PpV had strong positive effects on bacterial and HNF abundance, and the mass balance of C, N and P suggested an efficient transfer of organic material from P. pouchetii to bacterial and HNF biomass through viral lysis. At the same time, the degradation of P....... pouchetii lysates was associated with significant regeneration of inorganic N and P resulting in 148 microg N l(-1) and 7 microg P l(-1), corresponding to 78% and 26% of lysate N and P being mineralized to NH(4)(+) and PO(4)(3-), respectively. These results showed that the turnover of viral lysates...... in the microbial food web was associated with significant N and P mineralization, supporting the current view that viral lysates can be an important source of inorganic nutrients in marine systems. In the presence of R. salina, the generated NH(4)(+) supported 11% of the observed R. salina growth. Regrowth...

  11. Within- and among-population variation in vital rates and population dynamics in a variable environment.

    Science.gov (United States)

    Vincenzi, Simone; Mangel, Marc; Jesensˇek, Dusˇan; Garza, John C; Crivelli, Alain J

    2016-10-01

    Understanding the causes of within- and among-population differences in vital rates, life histories, and population dynamics is a central topic in ecology. To understand how within- and among-population variation emerges, we need long-term studies that include episodic events and contrasting environmental conditions, data to characterize individual and shared variation, and statistical models that can tease apart shared and individual contribution to the observed variation. We used long-term tag-recapture data to investigate and estimate within- and among-population differences in vital rates, life histories, and population dynamics of marble trout Salmo marmoratus, an endemic freshwater salmonid with a narrow range. Only ten populations of pure marble trout persist in headwaters of Alpine rivers in western Slovenia. Marble trout populations are also threatened by floods and landslides, which have already caused the extinction of two populations in recent years. We estimated and determined causes of variation in growth, survival, and recruitment both within and among populations, and evaluated trade-offs between them. Specifically, we estimated the responses of these traits to variation in water temperature, density, sex, early life conditions, and extreme events. We found that the effects of population density on traits were mostly limited to the early stages of life and that growth trajectories were established early in life. We found no clear effects of water temperature on vital rates. Population density varied over time, with flash floods and debris flows causing massive mortalities (>55% decrease in survival with respect to years with no floods) and threatening population persistence. Apart from flood events, variation in population density within streams was largely determined by variation in recruitment, with survival of older fish being relatively constant over time within populations, but substantially different among populations. Marble trout show a fast

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

    Science.gov (United States)

    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.

  13. Dynamics of adaptive immunity against phage in bacterial populations

    CERN Document Server

    Bradde, Serena; Tesileanu, Tiberiu; Balasubramanian, Vijay

    2015-01-01

    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 ...

  14. Binary Populations and Stellar Dynamics in Young Clusters

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 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.

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

    Science.gov (United States)

    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...

  17. Neuronal population dynamic model:An analytic approach

    Institute of Scientific and Technical Information of China (English)

    Wentao Huang; Licheng Jiao; Yuelei Xu; Shiping Ma; Jianhua Jia

    2009-01-01

    rom this,the stationary solution and the firing rate of the stationary states are given.Last,by the Fourier transform,the time dependent solution is also obtained.This method can be used to analyze the various dynamic behaviors of neuronal populations.

  18. Population Receptive Field Dynamics in Human Visual Cortex

    NARCIS (Netherlands)

    Haak, Koen V.; Cornelissen, Frans W.; Morland, Antony B.

    2012-01-01

    Seminal work in the early nineties revealed that the visual receptive field of neurons in cat primary visual cortex can change in location and size when artificial scotomas are applied. Recent work now suggests that these single neuron receptive field dynamics also pertain to the neuronal population

  19. Population dynamics of light-limited phytoplankton : Microcosm experiments

    NARCIS (Netherlands)

    Huisman, Jef

    1999-01-01

    This paper investigates the extent to which the predictions of an elementary model for light-limited growth are matched by laboratory experiments with light-limited phytoplankton. The model and experiments link the population dynamics of phytoplankton species with changes in the light gradient cause

  20. Binary populations and stellar dynamics in young clusters

    CERN Document Server

    Vanbeveren, D; Van Bever, J; Mennekens, N

    2008-01-01

    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, Eta Carinae, Zeta Puppis, Gamma Velorum and WR 140.

  1. Distribution and population dynamics of Rhizobium sp. introduced into soil.

    NARCIS (Netherlands)

    Postma, J.

    1989-01-01

    In this thesis the population dynamics of bacteria introduced into soil was studied. In the introduction, the existence of microhabitats favourable for the survival of indigenous bacteria is discussed. Knowledge about the distribution of introduced bacteria over such microhabitats,

  2. Do farming practices influence population dynamics of rodents?

    DEFF Research Database (Denmark)

    Massawe, A W; Rwamugira, W; Leirs, Herwig

    2007-01-01

    and slash and burn fields, cropping systems (mono- and inter-crop) had little effect on the population dynamics of M. natalensis [F(1,8) = 6.50; P > 0.05]. The study shows that land preparation methods should be considered a component of rodent pest management in ecologically based or integrated management...

  3. Equilibrium solutions for microscopic stochastic systems in population dynamics.

    Science.gov (United States)

    Lachowicz, Mirosław; Ryabukha, Tatiana

    2013-06-01

    The present paper deals with the problem of existence of equilibrium solutions of equations describing the general population dynamics at the microscopic level of modified Liouville equation (individually--based model) corresponding to a Markov jump process. We show the existence of factorized equilibrium solutions and discuss uniqueness. The conditions guaranteeing uniqueness or non-uniqueness are proposed under the assumption of periodic structures.

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

    Science.gov (United States)

    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.

  5. Estimating spatio-temporal dynamics of size-structured populations

    DEFF Research Database (Denmark)

    Kristensen, Kasper; Thygesen, Uffe Høgsbro; Andersen, Ken Haste

    2014-01-01

    Spatial distributions of structured populations are usually estimated by fitting abundance surfaces for each stage and at each point of time separately, ignoring correlations that emerge from growth of individuals. Here, we present a statistical model that combines spatio-temporal correlations...... with simple stock dynamics, to estimate simultaneously how size distributions and spatial distributions develop in time. We demonstrate the method for a cod population sampled by trawl surveys. Particular attention is paid to correlation between size classes within each trawl haul due to clustering...... of individuals with similar size. The model estimates growth, mortality and reproduction, after which any aspect of size-structure, spatio-temporal population dynamics, as well as the sampling process can be probed. This is illustrated by two applications: 1) tracking the spatial movements of a single cohort...

  6. Evolutionary dynamics of group interactions on structured populations: A review

    CERN Document Server

    Perc, Matjaz; Szolnoki, Attila; Floría, Luis M; Moreno, Yamir; 10.1098/rsif.2012.0997

    2013-01-01

    Interactions among living organisms, from bacteria colonies to human societies, are inherently more complex than interactions among particles and nonliving 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 proven valuable for studying pattern formation, equilibrium selection, and self-organisation in evolutionary games. Here we review recent advances in the study of evolutionary dynamics of group interactions on 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...

  7. Nonequilibrium population dynamics of phenotype conversion of cancer cells.

    Directory of Open Access Journals (Sweden)

    Joseph Xu Zhou

    Full Text Available Tumorigenesis is a dynamic biological process that involves distinct cancer cell subpopulations proliferating at different rates and interconverting between them. In this paper we proposed a mathematical framework of population dynamics that considers both distinctive growth rates and intercellular transitions between cancer cell populations. Our mathematical framework showed that both growth and transition influence the ratio of cancer cell subpopulations but the latter is more significant. We derived the condition that different cancer cell types can maintain distinctive subpopulations and we also explain why there always exists a stable fixed ratio after cell sorting based on putative surface markers. The cell fraction ratio can be shifted by changing either the growth rates of the subpopulations (Darwinism selection or by environment-instructed transitions (Lamarckism induction. This insight can help us to understand the dynamics of the heterogeneity of cancer cells and lead us to new strategies to overcome cancer drug resistance.

  8. Modeling structured population dynamics using data from unmarked individuals

    Science.gov (United States)

    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.

  9. Rethinking the logistic approach for population dynamics of mutualistic interactions.

    Science.gov (United States)

    García-Algarra, Javier; Galeano, Javier; Pastor, Juan Manuel; Iriondo, José María; Ramasco, José J

    2014-12-21

    Mutualistic communities have an internal structure that makes them resilient to external perturbations. Late research has focused on their stability and the topology of the relations between the different organisms to explain the reasons of the system robustness. Much less attention has been invested in analyzing the systems dynamics. The main population models in use are modifications of the r-K formulation of logistic equation with additional terms to account for the benefits produced by the interspecific interactions. These models have shortcomings as the so-called r-K formulation diverges under some conditions. In this work, we introduce a model for population dynamics under mutualism that preserves the original logistic formulation. It is mathematically simpler than the widely used type II models, although it shows similar complexity in terms of fixed points and stability of the dynamics. We perform an analytical stability analysis and numerical simulations to study the model behavior in general interaction scenarios including tests of the resilience of its dynamics under external perturbations. Despite its simplicity, our results indicate that the model dynamics shows an important richness that can be used to gain further insights in the dynamics of mutualistic communities.

  10. National Algal Biofuels Technology Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    Ferrell, John [Dept. of Energy (DOE), Washington DC (United States); Sarisky-Reed, Valerie [Dept. of Energy (DOE), Washington DC (United States)

    2010-05-01

    The framework for National Algal Biofuels Technology Roadmap was constructed at the Algal Biofuels Technology Roadmap Workshop, held December 9-10, 2008, at the University of Maryland-College Park. The Workshop was organized by the Biomass Program to discuss and identify the critical challenges currently hindering the development of a domestic, commercial-scale algal biofuels industry. This Roadmap presents information from a scientific, economic, and policy perspectives that can support and guide RD&D investment in algal biofuels. While addressing the potential economic and environmental benefits of using algal biomass for the production of liquid transportation fuels, the Roadmap describes the current status of algae RD&D. In doing so, it lays the groundwork for identifying challenges that likely need to be overcome for algal biomass to be used in the production of economically viable biofuels.

  11. The population dynamics of an endemic collectible cactus

    Science.gov (United States)

    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. An individual-based model of Zebrafish population dynamics accounting for energy dynamics

    DEFF Research Database (Denmark)

    Beaudouin, Remy; Goussen, Benoit; Piccini, Benjamin

    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...

  13. Advanced Algal Systems Fact Sheet

    Energy Technology Data Exchange (ETDEWEB)

    None

    2016-06-01

    Research and development (R&D) on advanced algal biofuels and bioproducts presents an opportunity to sustainably expand biomass resource potential in the United States. The Bioenergy Technologies Office’s (BETO’s) Advanced Algal Systems Program is carrying out a long-term, applied R&D strategy to lower the costs of algal biofuel production by working with partners to develop revolutionary technologies and conduct crosscutting analyses to better understand the potential

  14. How Predation and Landscape Fragmentation Affect Vole Population Dynamics

    DEFF Research Database (Denmark)

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

    2011-01-01

    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...

  15. Population dynamics in Er3+-doped fluoride glasses

    Science.gov (United States)

    Bogdanov, V. K.; Booth, D. J.; Gibbs, W. E.; Javorniczky, J. S.; Newman, P. J.; Macfarlane, D. R.

    2001-05-01

    A detailed study of the energy-transfer processes in Er3+: flouride glasses with doping concentrations of 0.2-18 mol % is presented. Fluorescence wave forms for 11 erbium transitions were measured under 802-nm, 1.5-μm, 975-nm, 520-nm, and 403-nm excitation from a high-energy short-pulse source. The analysis of these data provided a physical understanding of the processes responsible for the temporal behavior of the populations of a large number of energy levels. A comprehensive nine-level rate-equation model of the Er3+ population dynamics in these fluoride glasses is developed. The model performs well in predicting the observed fluorescence behavior of the main fluorescing lines under all pumping conditions. The modeling process allowed 14 ion-ion energy-transfer processes that are important for the population dynamics in these fluoride glasses to be identified and their rate constants obtained. Noticeably, the inclusion of seven three-ion processes was found necessary in order to obtain good fits to the experimental fluorescence wave forms. It was also found that some three-ion processes have a significant effect on the population dynamics of the levels even in lower doping concentrations.

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

    Science.gov (United States)

    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. Integrating population dynamics into mapping human exposure to seismic hazard

    Directory of Open Access Journals (Sweden)

    S. Freire

    2012-11-01

    Full Text Available Disaster risk is not fully characterized without taking into account vulnerability and population exposure. Assessment of earthquake risk in urban areas would benefit from considering the variation of population distribution at more detailed spatial and temporal scales, and from a more explicit integration of this improved demographic data with existing seismic hazard maps. In the present work, "intelligent" dasymetric mapping is used to model population dynamics at high spatial resolution in order to benefit the analysis of spatio-temporal exposure to earthquake hazard in a metropolitan area. These night- and daytime-specific population densities are then classified and combined with seismic intensity levels to derive new spatially-explicit four-class-composite maps of human exposure. The presented approach enables a more thorough assessment of population exposure to earthquake hazard. Results show that there are significantly more people potentially at risk in the daytime period, demonstrating the shifting nature of population exposure in the daily cycle and the need to move beyond conventional residence-based demographic data sources to improve risk analyses. The proposed fine-scale maps of human exposure to seismic intensity are mainly aimed at benefiting visualization and communication of earthquake risk, but can be valuable in all phases of the disaster management process where knowledge of population densities is relevant for decision-making.

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

    Science.gov (United States)

    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.

  19. Changes in Population Dynamics in Mutualistic versus Pathogenic Viruses

    Directory of Open Access Journals (Sweden)

    Marilyn J. Roossinck

    2011-01-01

    Full Text Available Although generally regarded as pathogens, viruses can also be mutualists. A number of examples of extreme mutualism (i.e., symbiogenesis have been well studied. Other examples of mutualism are less common, but this is likely because viruses have rarely been thought of as having any beneficial effects on their hosts. The effect of mutualism on the population dynamics of viruses is a topic that has not been addressed experimentally. However, the potential for understanding mutualism and how a virus might become a mutualist may be elucidated by understanding these dynamics.

  20. Changes in population dynamics in mutualistic versus pathogenic viruses.

    Science.gov (United States)

    Roossinck, Marilyn J

    2011-01-01

    Although generally regarded as pathogens, viruses can also be mutualists. A number of examples of extreme mutualism (i.e., symbiogenesis) have been well studied. Other examples of mutualism are less common, but this is likely because viruses have rarely been thought of as having any beneficial effects on their hosts. The effect of mutualism on the population dynamics of viruses is a topic that has not been addressed experimentally. However, the potential for understanding mutualism and how a virus might become a mutualist may be elucidated by understanding these dynamics.

  1. Algal biofuels from wastewater treatment high rate algal ponds.

    Science.gov (United States)

    Craggs, R J; Heubeck, S; Lundquist, T J; Benemann, J R

    2011-01-01

    This paper examines the potential of algae biofuel production in conjunction with wastewater treatment. Current technology for algal wastewater treatment uses facultative ponds, however, these ponds have low productivity (∼10 tonnes/ha.y), are not amenable to cultivating single algal species, require chemical flocculation or other expensive processes for algal harvest, and do not provide consistent nutrient removal. Shallow, paddlewheel-mixed high rate algal ponds (HRAPs) have much higher productivities (∼30 tonnes/ha.y) and promote bioflocculation settling which may provide low-cost algal harvest. Moreover, HRAP algae are carbon-limited and daytime addition of CO(2) has, under suitable climatic conditions, the potential to double production (to ∼60 tonnes/ha.y), improve bioflocculation algal harvest, and enhance wastewater nutrient removal. Algae biofuels (e.g. biogas, ethanol, biodiesel and crude bio-oil), could be produced from the algae harvested from wastewater HRAPs, The wastewater treatment function would cover the capital and operation costs of algal production, with biofuel and recovered nutrient fertilizer being by-products. Greenhouse gas abatement results from both the production of the biofuels and the savings in energy consumption compared to electromechanical treatment processes. However, to achieve these benefits, further research is required, particularly the large-scale demonstration of wastewater treatment HRAP algal production and harvest.

  2. Trends and population dynamics of a Velvet Scoter (Melanitta fusca) population: influence of density dependence and winter climate

    NARCIS (Netherlands)

    Hartman, G.; Kölzsch, A.; Larsson, K.; Nordberg, M.; Höglund, J.

    2013-01-01

    As many seaduck populations around the world have been reported to be in decline, there is an increasing demand for knowledge about intrinsic and extrinsic factors determining population dynamics of these species. In this study, we analyzed long-term dynamics of the summer population of Velvet Scote

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

    Science.gov (United States)

    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.

  4. Combined effect of successive competition periods on population dynamics

    OpenAIRE

    Anazawa, Masahiro

    2010-01-01

    This study investigates the effect of competition between individuals on population dynamics when they compete for different resources during different seasons or during different growth stages. Individuals are assumed to compete for a single resource during each of these periods according to one of the following competition types: scramble, contest, or an intermediate between the two. The effect of two successive competition periods is determined to be expressed by simple relations on produc...

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

    Science.gov (United States)

    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.

  6. Nonlinear modeling of neural population dynamics for hippocampal prostheses

    OpenAIRE

    Song, Dong; Chan, Rosa H.M.; Vasilis Z Marmarelis; Hampson, Robert E.; Deadwyler, Sam A.; Berger, Theodore W.

    2009-01-01

    Developing a neural prosthesis for the damaged hippocampus requires restoring the transformation of population neural activities performed by the hippocampal circuitry. To bypass a damaged region, output spike trains need to be predicted from the input spike trains and then reinstated through stimulation. We formulate a multiple-input, multiple-output (MIMO) nonlinear dynamic model for the input–output transformation of spike trains. In this approach, a MIMO model comprises a series of physio...

  7. Development of paradigms for the dynamics of structured populations

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Directory of Open Access Journals (Sweden)

    Joseph G Makin

    2015-11-01

    Full Text Available 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.

  9. Network Evolution Induced by the Dynamical Rules of Two Populations

    CERN Document Server

    Platini, T

    2010-01-01

    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 ($N_a$ and $N_b$) and preferred degree ($\\kappa_a$ 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 $\\moyenne{k_{bb}}$ and $\\moyenne{k_{ab}}$ presents three time regimes and a non monotonic behavior well captured by our theory. Surprisingly, when the population size are equal $N_a=N_b$, the ratio of the restricted degree $\\theta_0=\\moyenne{k_{ab}}/\\moyenne{k_{bb}}$ appears to be an integer in the asymptotic limits of the three time regimes. For early times (defined by $t

  10. Physiologically structured populations with diffusion and dynamic boundary conditions.

    Science.gov (United States)

    Farkas, József Z; Hinow, Peter

    2011-04-01

    We consider a linear size-structured population model with diffusion in the size-space. Individuals are recruited into the population at arbitrary sizes. We equip the model with generalized Wentzell-Robin (or dynamic) boundary conditions. This approach allows the modelling of populations in which individuals may have distinguished physiological states. We establish existence and positivity of solutions by showing that solutions are governed by a positive quasicontractive semigroup of linear operators on the biologically relevant state space. These results are obtained by establishing dissipativity of a suitably perturbed semigroup generator. We also show that solutions of the model exhibit balanced exponential growth, that is, our model admits a finite-dimensional global attractor. In case of strictly positive fertility we are able to establish that solutions in fact exhibit asynchronous exponential growth.

  11. Pattern formation and coexistence domains for a nonlocal population dynamics

    CERN Document Server

    da Cunha, J A R; Oliveira, F A

    2011-01-01

    In this communication we propose a most general equation to study pattern formation for one-species population and their limit domains in systems of length L. To accomplish this we include non-locality in the growth and competition terms where the integral kernels are now depend on characteristic length parameters alpha and beta. Therefore, we derived a parameter space (alpha,beta) where it is possible to analyze a coexistence curve alpha*=alpha*(\\beta) which delimits domains for the existence (or not) of pattern formation in population dynamics systems. We show that this curve has an analogy with coexistence curve in classical thermodynamics and critical phenomena physics. We have successfully compared this model with experimental data for diffusion of Escherichia coli populations.

  12. Past and present population dynamics of narwhals Monodon monoceros

    DEFF Research Database (Denmark)

    Garde, Eva

    , meat and mattak. Concerns have been raised about the sustainability of the hunt, which have led to implementation of hunting quotas in both countries. Hunting quotas are usually calculated from population dynamics models where survival and reproductive rates, based on reliable age distributions...... through analysis of ancient and modern mitochondrial DNA (mtDNA). Very low levels of genetic diversity have been observed in modern narwhals from Canada and Greenland, resembling that of species that have endured through severe bottlenecks. The hypothesis is that the current narwhal populations were......, are vital. Estimation of life history parameters for the narwhal has previously been hindered by lack of a reliable age estimation technique. The Aspartic Acid Racemization (AAR) technique is a relatively novel method that I have applied to narwhals. This PhD thesis focuses, in part, on current population...

  13. Connection between dynamically derived IMF normalisation and stellar populations

    CERN Document Server

    McDermid, Richard M

    2015-01-01

    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 w...

  14. IMF shape constraints from stellar populations and dynamics from CALIFA

    CERN Document Server

    Lyubenova, M; van de Ven, G; Falcón-Barroso, J; Galbany, L; Gallazzi, A; García-Benito, R; Delgado, R González; Husemann, B; La Barbera, F; Marino, R A; Mast, D; Mendez-Abreu, J; Peletier, R F P; Sánchez-Blázquez, P; Sánchez, S F; Trager, S C; Bosch, R C E van den; Vazdekis, A; Walcher, C J; Zhu, L; Zibetti, S; Ziegler, B; Bland-Hawthorn, J

    2016-01-01

    In this letter we describe how we use stellar dynamics information to constrain the shape of the stellar IMF in a sample of 27 early-type galaxies from the CALIFA survey. We obtain dynamical and stellar mass-to-light ratios, $\\Upsilon_\\mathrm{dyn}$ and $\\Upsilon_{\\ast}$, over a homogenous aperture of 0.5~$R_{e}$. We use the constraint $\\Upsilon_\\mathrm{dyn} \\ge \\Upsilon_{\\ast}$ to test two IMF shapes within the framework of the extended MILES stellar population models. We rule out a single power law IMF shape for 75% of the galaxies in our sample. Conversely, we find that a double power law IMF shape with a varying high-mass end slope is compatible (within 1$\\sigma$) with 95% of the galaxies. We also show that dynamical and stellar IMF mismatch factors give consistent results for the systematic variation of the IMF in these galaxies.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 cervicornis on the banks but 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.

  17. Connection between dynamically derived IMF normalisation and stellar population parameters

    CERN Document Server

    McDermid, Richard M; Alatalo, Katherine; Bayet, Estelle; Blitz, Leo; Bois, Maxime; Bournaud, Frederic; Bureau, Martin; Crocker, Alison F; Davies, Roger L; Davis, Timothy A; de Zeeuw, P T; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnovic, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M

    2014-01-01

    We report on empirical trends between the dynamically determined stellar initial mass function (IMF) and stellar population properties for a complete, volume-limited sample of 260 early-type galaxies from the Atlas3D project. We study trends between our dynamically-derived IMF normalisation and absorption line strengths, and interpret these via single stellar population- (SSP-) equivalent ages, abundance ratios (measured as [alpha/Fe]), and total metallicity, [Z/H]. We find that old and alpha-enhanced galaxies tend to have on average heavier (Salpeter-like) mass normalisation of the IMF, but stellar population does not appear to be a good predictor of the IMF, with a large range of normalisation at a given population parameter. As a result, we find weak IMF-[alpha/Fe] and IMF-age correlations, and no significant IMF-[Z/H] correlation. The observed trends appear significantly weaker than those reported in studies that measure the IMF normalisation via low-mass star demographics inferred through stellar spectra...

  18. Border Collision Bifurcations in a Generalized Model of Population Dynamics

    Directory of Open Access Journals (Sweden)

    Lilia M. Ladino

    2016-01-01

    Full Text Available We analyze the dynamics of a generalized discrete time population model of a two-stage species with recruitment and capture. This generalization, which is inspired by other approaches and real data that one can find in literature, consists in considering no restriction for the value of the two key parameters appearing in the model, that is, the natural death rate and the mortality rate due to fishing activity. In the more general case the feasibility of the system has been preserved by posing opportune formulas for the piecewise map defining the model. The resulting two-dimensional nonlinear map is not smooth, though continuous, as its definition changes as any border is crossed in the phase plane. Hence, techniques from the mathematical theory of piecewise smooth dynamical systems must be applied to show that, due to the existence of borders, abrupt changes in the dynamic behavior of population sizes and multistability emerge. The main novelty of the present contribution with respect to the previous ones is that, while using real data, richer dynamics are produced, such as fluctuations and multistability. Such new evidences are of great interest in biology since new strategies to preserve the survival of the species can be suggested.

  19. Environmental influence on population dynamics of the bivalve Anomalocardia brasiliana

    Science.gov (United States)

    Corte, Guilherme Nascimento; Coleman, Ross A.; Amaral, A. Cecília Z.

    2017-03-01

    Understanding how species respond to the environment in terms of population attributes (e.g. abundance, growth, mortality, fecundity, and productivity) is essential to protect ecologically and economically important species. Nevertheless, responses of macrobenthic populations to environmental features are overlooked due to the need of consecutive samplings and time-consuming measurements. We examined the population dynamics of the filter-feeding bivalve Anomalocardia brasiliana on a tidal flat over the course of one year to investigate the hypothesis that, as accepted for macrobenthic communities, populations inhabiting environments with low hydrodynamic conditions such as tidal flat should have higher attributes than populations inhabiting more energetic habitats (i.e. areas more influenced by wave energy such as reflective and intermediate beaches). This would be expected because the harsh conditions of more energetic habitats force organisms to divert more energy towards maintenance, resulting in lower population attributes. We found that A. brasiliana showed moderate growth and secondary production at the study area. Moreover the recruitment period was restricted to a few months. A comparison with previous studies showed that, contrary to expected, A. brasiliana populations from areas with low hydrodynamic conditions have lower abundance, growth, recruitment and turnover rate. It is likely that morphodynamic characteristics recorded in these environments, such as larger periods of air exposure and lower water circulation, may affect food conditions for filter-feeding species and increase competition. In addition, these characteristics may negatively affect macrobenthic species by enhancing eutrophication processes and anoxia. Overall, our results suggest that models accepted and applied at the macrobenthic community level might not be directly extended to A. brasiliana populations.

  20. Population Dynamics of Early Human Migration in Britain

    Science.gov (United States)

    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

  1. Population Dynamics of Early Human Migration in Britain.

    Directory of Open Access Journals (Sweden)

    Mayank N Vahia

    Full Text Available 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.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.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.

  2. Stationary Stability for Evolutionary Dynamics in Finite Populations

    Directory of Open Access Journals (Sweden)

    Marc Harper

    2016-08-01

    Full Text Available We demonstrate a vast expansion of the theory of evolutionary stability to finite populations with mutation, connecting the theory of the stationary distribution of the Moran process with the Lyapunov theory of evolutionary stability. We define the notion of stationary stability for the Moran process with mutation and generalizations, as well as a generalized notion of evolutionary stability that includes mutation called an incentive stable state (ISS candidate. For sufficiently large populations, extrema of the stationary distribution are ISS candidates and we give a family of Lyapunov quantities that are locally minimized at the stationary extrema and at ISS candidates. In various examples, including for the Moran and Wright–Fisher processes, we show that the local maxima of the stationary distribution capture the traditionally-defined evolutionarily stable states. The classical stability theory of the replicator dynamic is recovered in the large population limit. Finally we include descriptions of possible extensions to populations of variable size and populations evolving on graphs.

  3. Dynamic distributions and population declines of Golden-winged Warblers

    Science.gov (United States)

    Rosenberg, Kenneth V.; Will, Tom; Buehler, David A.; Barker Swarthout, Sara; Thogmartin, Wayne E.; Chandler, Richard

    2016-01-01

    With an estimated breeding population in 2010 of 383,000 pairs, the Golden-winged Warbler (Vermivora chrysoptera) is among the most vulnerable and steeply declining of North American passerines. This species also has exhibited among the most dynamic breeding distributions, with populations expanding and then contracting over the past 150 years in response to regional habitat changes, interactions with closely related Blue-winged Warblers (V. cyanoptera), and possibly climate change. Since 1966, the rangewide population has declined by >70% (-2.3% per year; latest North American Breeding Bird Survey data), with much steeper declines in the Appalachian Mountains bird conservation region (-8.3% per year, 98% overall decline). Despite apparently stable or increasing populations in the northwestern part of the range (Minnesota, Manitoba), population estimates for Golden-winged Warbler have continued to decline by 18% from the decade of the 1990s to the 2000s. Population modeling predicts a further decline to roughly 37,000 individuals by 2100, with the species likely to persist only in Manitoba, Minnesota, and possibly Ontario. To delineate the present-day distribution and to identify population concentrations that could serve as conservation focus areas, we compiled rangewide survey data collected in 2000-2006 in 21 states and 3 Canadian provinces, as part of the Golden-winged Warbler Atlas Project (GOWAP), supplemented by state and provincial Breeding Bird Atlas data and more recent observations in eBird. Based on >8,000 GOWAP surveys for Golden-winged and Blue-winged warblers and their hybrids, we mapped occurrence of phenotypically pure and mixed populations in a roughly 0.5-degree grid across the species’ ranges. Hybrids and mixed Golden-winged-Blue-winged populations occurred in a relatively narrow zone across Minnesota, Wisconsin, Michigan, southern Ontario, and northern New York. Phenotypically pure Golden-winged Warbler populations occurred north of this

  4. Population Dynamics of the Giant Clam, Tridacna maxima, at Rose Atoll

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — There is a paucity of knowledge on the population dynamics of the giant clams of the family Tridacnidae. Such information on population dynamics is necessary for...

  5. Dynamical population synthesis: Constructing the stellar single and binary contents of galactic field populations

    CERN Document Server

    Marks, Michael

    2011-01-01

    [abridged] The galactic field's late-type stellar single and binary population is calculated on the supposition that all stars form as binaries in embedded star clusters. A recently developed tool (Marks, Kroupa & Oh) is used to evolve the binary star distributions in star clusters for a few Myr so that a particular mixture of single and binary stars is achieved. On cluster dissolution the population enters the galactic field with these characteristics. The different contributions of single stars and binaries from individual star clusters which are selected from a power-law embedded star cluster mass function are then added up. This gives rise to integrated galactic field binary distribution functions (IGBDFs) resembling a galactic field's stellar content (Dynamical Population Synthesis). It is found that the binary proportion in the galactic field of a galaxy is larger the lower the minimum cluster mass, the lower the star formation rate, the steeper the embedded star cluster mass function and the larger...

  6. Population Dynamics in the Capitalist World-Economy

    Directory of Open Access Journals (Sweden)

    Daniela Danna

    2015-08-01

    Full Text Available World-systems analysis has given scant attention to population dynamics. Overlooked are large-scale macrohistorical population trends and their microhistorical foundation on procreative decisions-decisions which are taken by a historically changing subject of procreation: local elders or other authorities, head(s of the household, couples, and women. The discipline of demography is also not as helpful as it could be, given its basis in modernization theory, which fails to recognize intentionality in reproduction in pre-capitalist societies. It assumes a model of "demographic transition" from a state of "natural fertility" to a state of conscious family planning, while also treating mortality as independent of fertility Marxism recognized the importance of population as a source of labor for profit and capital accumulation. With its tools Sydney Coontz developed a demand for labor theory explaining in particular the decrease in the birth rate in England and the United States at the turn of the century This theory was f urther developed by anthropologists of the "mode of product ion and population pat terns " who, with other authors, offer useful theories and insights to advance world-historical research on population. This article explores connections between population dy namics and world-systems analysis. I explore six key questions at different levels of analysis, including: 1 Are there world-systems ' imperatives concerning human reproduction?; 2 Do human reproduction imperatives differ across world-systems.'?; 3 How do the (eventual systems requirements get transmitted to households and individuals'?; 4 Why do people have children.'?; 5 Who is the subject of procreation decisions'?; and 6 How is the number of offspring chosen? Finally, I offer guidelines for applying the six questions to the capitalist world-economy.

  7. Mechanical reaction-diffusion model for bacterial population dynamics

    CERN Document Server

    Ngamsaad, Waipot

    2015-01-01

    The effect of mechanical interaction between cells on the spreading of bacterial population was investigated in one-dimensional space. A nonlinear reaction-diffusion equation has been formulated as a model for this dynamics. In this model, the bacterial cells are treated as the rod-like particles that interact, when contacting each other, through the hard-core repulsion. The repulsion introduces the exclusion process that causes the fast diffusion in bacterial population at high density. The propagation of the bacterial density as the traveling wave front in long time behavior has been analyzed. The analytical result reveals that the front speed is enhanced by the exclusion process---and its value depends on the packing fraction of cell. The numerical solutions of the model have been solved to confirm this prediction.

  8. Spatial and temporal dynamics of infected populations: the Mexican epidemic

    CERN Document Server

    Rodriguez-Meza, Mario A

    2012-01-01

    Recently the A/H1N1-2009 virus pandemic appeared in Mexico and in other nations. We present a study of this pandemic in the Mexican case using the SIR model to describe epidemics. This model is one of the simplest models but it has been a successful description of some epidemics of closed populations. We consider the data for the Mexican case and use the SIR model to make some predictions. Then, we generalize the SIR model in order to describe the spatial dynamics of the disease. We make a study of the spatial and temporal spread of the infected population with model parameters that are consistent with temporal SIR model parameters obtained by fitting to the Mexican case.

  9. pedagog: software for simulating eco-evolutionary population dynamics.

    Science.gov (United States)

    Coombs, Jason A; Letcher, B H; Nislow, K H

    2010-05-01

    pedagog is a Windows program that can be used to determine power for, and validate inferences drawn from, eco-evolutionary studies. It models dynamics of multiple populations and their interactions through individual-based simulations while simultaneously recording genotype, pedigree and trait information at the individual level. pedagog also allows for specification of heritable traits, natural and sexual selection acting upon those traits, population sampling schemes and incorporation of genetic and demographic errors into the output. Overall, parameters can be specified for genetic diversity, demographics, mating design, genetic and demographic errors, individual growth models, trait heritability and selection, and output formatting. Demographic parameters can be either age or function based, and all parameters can be drawn from 12 statistical distributions where appropriate. Simulation results can be automatically formatted for 57 existing software programs to facilitate postsimulation analyses. pedagog is freely available for download at https://bcrc.bio.umass.edu/pedigreesoftware/.

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

    Science.gov (United States)

    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.

  11. Knowledge epidemics and population dynamics models for describing idea diffusion

    CERN Document Server

    Vitanov, Nikolay K

    2012-01-01

    The diffusion of ideas is often closely connected to the creation and diffusion of knowledge and to the technological evolution of society. Because of this, knowledge creation, exchange and its subsequent transformation into innovations for improved welfare and economic growth is briefly described from a historical point of view. Next, three approaches are discussed for modeling the diffusion of ideas in the areas of science and technology, through (i) deterministic, (ii) stochastic, and (iii) statistical approaches. These are illustrated through their corresponding population dynamics and epidemic models relative to the spreading of ideas, knowledge and innovations. The deterministic dynamical models are considered to be appropriate for analyzing the evolution of large and small societal, scientific and technological systems when the influence of fluctuations is insignificant. Stochastic models are appropriate when the system of interest is small but when the fluctuations become significant for its evolution...

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

    Directory of Open Access Journals (Sweden)

    Leilei Qu

    2016-01-01

    Full Text Available 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.

  13. Mosquito population dynamics from cellular automata-based simulation

    Science.gov (United States)

    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.

  14. Algal Biofuels; Algal Biofuels R&D at NREL (Brochure)

    Energy Technology Data Exchange (ETDEWEB)

    2010-09-01

    An overview of NREL's algal biofuels projects, including U.S. Department of Energy-funded work, projects with U.S. and international partners, and Laboratory Directed Research and Development projects.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Directory of Open Access Journals (Sweden)

    Rebecca S Rudicell

    Full Text Available 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

  18. The model of fungal population dynamics affected by nystatin

    Science.gov (United States)

    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

  19. Representation of dynamical stimuli in populations of threshold neurons.

    Directory of Open Access Journals (Sweden)

    Tatjana Tchumatchenko

    2011-10-01

    Full Text Available Many sensory or cognitive events are associated with dynamic current modulations in cortical neurons. This raises an urgent demand for tractable model approaches addressing the merits and limits of potential encoding strategies. Yet, current theoretical approaches addressing the response to mean- and variance-encoded stimuli rarely provide complete response functions for both modes of encoding in the presence of correlated noise. Here, we investigate the neuronal population response to dynamical modifications of the mean or variance of the synaptic bombardment using an alternative threshold model framework. In the variance and mean channel, we provide explicit expressions for the linear and non-linear frequency response functions in the presence of correlated noise and use them to derive population rate response to step-like stimuli. For mean-encoded signals, we find that the complete response function depends only on the temporal width of the input correlation function, but not on other functional specifics. Furthermore, we show that both mean- and variance-encoded signals can relay high-frequency inputs, and in both schemes step-like changes can be detected instantaneously. Finally, we obtain the pairwise spike correlation function and the spike triggered average from the linear mean-evoked response function. These results provide a maximally tractable limiting case that complements and extends previous results obtained in the integrate and fire framework.

  20. Algal Bloom: Boon or Bane?

    Digital Repository Service at National Institute of Oceanography (India)

    LokaBharathi, P.A.

    Algal blooms occur in response to nutrient deplete or replete conditions. Nitrogen fixing forms proliferate under oligotrophic conditions when nutrient levels are low. Replete conditions in response to upwelling creates the most biologically...

  1. Seasonal and annual dynamics of harmful algae and algal toxins revealed through weekly monitoring at two coastal ocean sites off southern California, USA

    KAUST Repository

    Seubert, Erica L.

    2013-01-04

    Reports of toxic harmful algal blooms (HABs) attributed to the diatom Pseudo-nitzschia spp. have been increasing in California during the last several decades. Whether this increase can be attributed to enhanced awareness and monitoring or to a dramatic upswing in the development of HAB events remains unresolved. Given these uncertainties, the ability to accurately and rapidly identify an emerging HAB event is of high importance. Monitoring of HAB species and other pertinent chemical/physical parameters at two piers in southern California, Newport and Redondo Beach, was used to investigate the development of a site-specific bloom definition for identifying emerging domoic acid (DA) events. Emphasis was given to abundances of the Pseudo-nitzschia seriata size category of Pseudo-nitzschia due to the prevalence of this size class in the region. P. seriata bloom thresholds were established for each location based on deviations from their respective long-term mean abundances, allowing the identification of major and minor blooms. Sixty-five percent of blooms identified at Newport Beach coincided with measurable DA concentrations, while 36 % of blooms at Redondo Beach coincided with measurable DA. Bloom definitions allowed for increased specificity in multiple regression analysis of environmental forcing factors significant to the presence of DA and P. seriata. The strongest relationship identified was between P. seriata abundances 2 weeks following upwelling events at Newport Beach. © 2012 Springer-Verlag Berlin Heidelberg.

  2. Comparative dynamics and life histories of coexisting dragonfly populations

    Energy Technology Data Exchange (ETDEWEB)

    Benke, A.C.; Benke, S.S.

    Several species of coexisting dragonfly larvae were studied for four consecutive years in a 1-ha old farm pond. Larval development, emergence patterns, and adult flight patterns showed that the most abundant species were univoltine and developed relatively synchronously (i.e., like a cohort). Three of the common species emerged in early spring, and the others emerged later in the summer. The common genera with the most similar microhabitat had a distinct temporal separation that may serve in reducing interspecific competition. However, coexisting congeneric species had almost identical life histories, supporting the hypothesis that ecological homologues can coexist because of ''errors of exploitation'' of the dominant species. The larval population dynamics of each dominant species (Ladona deplanata, Epitheca spp., and Celithemis fasciata) was characterized by a constant percentage numerical decline, coupled with with a dramatic biomass increase from time of hatching to final instar. Larval mortality during this period averaged 92 percent per annum, but population biomass increased at least tenfold during the same period for each species. Comparison of larval estimates with emergence data revealed that at least 80 percent of the final instars die just before leaving the water to emerge. Life history variations among species smoothed out composite density and biomass trends which averaged about 1,000 individuals/m/sup 2/ and 2 g dry wt/m/sup 2/, respectively. In general, population dynamics from year to year were quite consistent, indicating a relatively high degree of stability in terms of species composition and densities. (auth)

  3. Fueling Future with Algal Genomics

    Energy Technology Data Exchange (ETDEWEB)

    Grigoriev, Igor

    2012-07-05

    Algae constitute a major component of fundamental eukaryotic diversity, play profound roles in the carbon cycle, and are prominent candidates for biofuel production. The US Department of Energy Joint Genome Institute (JGI) is leading the world in algal genome sequencing (http://jgi.doe.gov/Algae) and contributes of the algal genome projects worldwide (GOLD database, 2012). The sequenced algal genomes offer catalogs of genes, networks, and pathways. The sequenced first of its kind genomes of a haptophyte E.huxleyii, chlorarachniophyte B.natans, and cryptophyte G.theta fill the gaps in the eukaryotic tree of life and carry unique genes and pathways as well as molecular fossils of secondary endosymbiosis. Natural adaptation to conditions critical for industrial production is encoded in algal genomes, for example, growth of A.anophagefferens at very high cell densities during the harmful algae blooms or a global distribution across diverse environments of E.huxleyii, able to live on sparse nutrients due to its expanded pan-genome. Communications and signaling pathways can be derived from simple symbiotic systems like lichens or complex marine algae metagenomes. Collectively these datasets derived from algal genomics contribute to building a comprehensive parts list essential for algal biofuel development.

  4. Neural Population Dynamics Modeled by Mean-Field Graphs

    Science.gov (United States)

    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.

  5. Mean-field games with logistic population dynamics

    KAUST Repository

    Gomes, Diogo A.

    2013-12-01

    In its standard form, a mean-field game can be defined by coupled system of equations, a Hamilton-Jacobi equation for the value function of agents and a Fokker-Planck equation for the density of agents. Traditionally, the latter equation is adjoint to the linearization of the former. Since the Fokker-Planck equation models a population dynamic, we introduce natural features such as seeding and birth, and nonlinear death rates. In this paper we analyze a stationary meanfield game in one dimension, illustrating various techniques to obtain regularity of solutions in this class of systems. In particular we consider a logistic-type model for birth and death of the agents which is natural in problems where crowding affects the death rate of the agents. The introduction of these new terms requires a number of new ideas to obtain wellposedness. In a forthcoming publication we will address higher dimensional models. ©2013 IEEE.

  6. Particle tagging and its implications for stellar population dynamics

    CERN Document Server

    Bret, Theo Le; Cooper, Andrew P; Frenk, Carlos; Zolotov, Adi; Brooks, Alyson M; Governato, Fabio; Parry, Owen H

    2015-01-01

    We establish a controlled comparison between the properties of galactic stellar halos obtained with hydrodynamical simulations and with `particle tagging'. Tagging is a fast way to obtain stellar population dynamics: instead of tracking gas and star formation, it `paints' stars directly onto a suitably defined subset of dark matter particles in a collisionless, dark-matter-only simulation.Our study shows that there are conditions under which particle tagging generates good fits to the hydrodynamical stellar density profiles of a central Milky-Way-like galaxy and its most prominent substructure. Phase-space diffusion processes are crucial to reshaping the distribution of stars in infalling spheroidal systems and hence the final stellar halo. We conclude that the success of any particular tagging scheme hinges on this diffusion being taken into account, at a minimum by making use of `live' tagging schemes, in which particles are regularly tagged throughout the evolution of a galaxy.

  7. Sensory dynamics of visual hallucinations in the normal population

    Science.gov (United States)

    Pearson, Joel; Chiou, Rocco; Rogers, Sebastian; Wicken, Marcus; Heitmann, Stewart; Ermentrout, Bard

    2016-01-01

    Hallucinations occur in both normal and clinical populations. Due to their unpredictability and complexity, the mechanisms underlying hallucinations remain largely untested. Here we show that visual hallucinations can be induced in the normal population by visual flicker, limited to an annulus that constricts content complexity to simple moving grey blobs, allowing objective mechanistic investigation. Hallucination strength peaked at ~11 Hz flicker and was dependent on cortical processing. Hallucinated motion speed increased with flicker rate, when mapped onto visual cortex it was independent of eccentricity, underwent local sensory adaptation and showed the same bistable and mnemonic dynamics as sensory perception. A neural field model with motion selectivity provides a mechanism for both hallucinations and perception. Our results demonstrate that hallucinations can be studied objectively, and they share multiple mechanisms with sensory perception. We anticipate that this assay will be critical to test theories of human consciousness and clinical models of hallucination. DOI: http://dx.doi.org/10.7554/eLife.17072.001 PMID:27726845

  8. Dynamic equilibrium of reconstituting hematopoietic stem cell populations.

    Science.gov (United States)

    O'Quigley, John

    2010-12-01

    Clonal dominance in hematopoietic stem cell populations is an important question of interest but not one we can directly answer. Any estimates are based on indirect measurement. For marked populations, we can equate empirical and theoretical moments for binomial sampling, in particular we can use the well-known formula for the sampling variation of a binomial proportion. The empirical variance itself cannot always be reliably estimated and some caution is needed. We describe the difficulties here and identify ready solutions which only require appropriate use of variance-stabilizing transformations. From these we obtain estimators for the steady state, or dynamic equilibrium, of the number of hematopoietic stem cells involved in repopulating the marrow. The calculations themselves are not too involved. We give the distribution theory for the estimator as well as simple approximations for practical application. As an illustration, we rework on data recently gathered to address the question as to whether or not reconstitution of marrow grafts in the clinical setting might be considered to be oligoclonal.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    Marcos, C de la Fuente

    2016-01-01

    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 C...

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Richard McElreath

    Full Text Available 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.

  13. Population dynamics of caribou herds in southwestern Alaska

    Directory of Open Access Journals (Sweden)

    Patrick Valkenburg

    2003-04-01

    Full Text Available The five naturally occurring and one transplanted caribou (Rangifer tarandus granti herd in southwestern Alaska composed about 20% of Alaska's caribou population in 2001. All five of the naturally occurring herds fluctuated considerably in size between the late 1800s and 2001 and for some herds the data provide an indication of long-term periodic (40-50 year fluctuations. At the present time, the Unimak (UCH and Southern Alaska Peninsula (SAP are recovering from population declines, the Northern Alaska Peninsula Herd (NAP appears to be nearing the end of a protracted decline, and the Mulchatna Herd (MCH appears to now be declining after 20 years of rapid growth. The remaining naturally occurring herd (Kilbuck has virtually disappeared. Nutrition had a significant effect on the size of 4-month-old and 10-month-old calves in the NAP and the Nushagak Peninsula Herd (NPCH and probably also on population growth in at least 4 (SAP, NAP, NPCH, and MCH of the six caribou herds in southwestern Alaska. Predation does not appear to be sufficient to keep caribou herds in southwestern Alaska from expanding, probably because rabies is endemic in red foxes (Vulpes vulpes and is periodically transferred to wolves (Canis lupus and other canids. However, we found evidence that pneumonia and hoof rot may result in significant mortality of caribou in southwestern Alaska, whereas there is no evidence that disease is important in the dynamics of Interior herds. Cooperative conservation programs, such as the Kilbuck Caribou Management Plan, can be successful in restraining traditional harvest and promoting growth in caribou herds. In southwestern Alaska we also found evidence that small caribou herds can be swamped and assimilated by large herds, and fidelity to traditional calving areas can be lost.

  14. Theoretical lessons for increasing algal biofuel: Evolution of oil accumulation to avert carbon starvation in microalgae.

    Science.gov (United States)

    Akita, Tetsuya; Kamo, Masashi

    2015-09-07

    Microalgae-derived oil is considered as a feasible alternative to fossil-derived oil. To produce more algal biomass, both algal population size and oil accumulation in algae must be maximized. Most of the previous studies have concentrated on only one of these issues, and relatively little attention has been devoted to considering the tradeoff between them. In this paper, we first theoretically investigated evolutionary reasons for oil accumulation and then by coupling population and evolutionary dynamics, we searched for conditions that may provide better yields. Using our model, we assume that algae allocate assimilated carbon to growth, maintenance, and carbon accumulation as biofuel and that the amount of essential materials (carbon and nitrate) are strongly linked in fixed proportions. Such stoichiometrically explicit models showed that (i) algae with more oil show slower population growth; therefore, the use of such algae results in lower total yields of biofuel and (ii) oil accumulation in algae is caused by carbon and not nitrate starvation. The latter can be interpreted as a strategy for avoiding the risk of increased death rate by carbon starvation. Our model also showed that both strong carbon starvation and moderately limited nitrate will promote total biofuel production. Our results highlight considering the life-history traits for a higher total yields of biofuel, which leads to insight into both establishing a prolonged culture and collection of desired strains from a natural environment.

  15. Sapphire Energy - Integrated Algal Biorefinery

    Energy Technology Data Exchange (ETDEWEB)

    White, Rebecca L. [Sapphire Energy, Inc., Columbus, NM (United States). Columbus Algal Biomass Farm; Tyler, Mike [Sapphire Energy, Inc., San Diego, CA (United States)

    2015-07-22

    Sapphire Energy, Inc. (SEI) is a leader in large-scale photosynthetic algal biomass production, with a strongly cohesive research, development, and operations program. SEI takes a multidiscipline approach to integrate lab-based strain selection, cultivation and harvest and production scale, and extraction for the production of Green Crude oil, a drop in replacement for traditional crude oil.. SEI’s technical accomplishments since 2007 have produced a multifunctional platform that can address needs for fuel, feed, and other higher value products. Figure 1 outlines SEI’s commercialization process, including Green Crude production and refinement to drop in fuel replacements. The large scale algal biomass production facility, the SEI Integrated Algal Biorefinery (IABR), was built in Luna County near Columbus, New Mexico (see fig 2). The extraction unit was located at the existing SEI facility in Las Cruces, New Mexico, approximately 95 miles from the IABR. The IABR facility was constructed on time and on budget, and the extraction unit expansion to accommodate the biomass output from the IABR was completed in October 2012. The IABR facility uses open pond cultivation with a proprietary harvesting method to produce algal biomass; this biomass is then shipped to the extraction facility for conversion to Green Crude. The operation of the IABR and the extraction facilities has demonstrated the critical integration of traditional agricultural techniques with algae cultivation knowledge for algal biomass production, and the successful conversion of the biomass to Green Crude. All primary unit operations are de-risked, and at a scale suitable for process demonstration. The results are stable, reliable, and long-term cultivation of strains for year round algal biomass production. From June 2012 to November 2014, the IABR and extraction facilities produced 524 metric tons (MT) of biomass (on a dry weight basis), and 2,587 gallons of Green Crude. Additionally, the IABR

  16. Population dynamics and monitoring applied to decision-making

    Directory of Open Access Journals (Sweden)

    Conroy, M. J.

    2004-06-01

    influence diagrams to capture the stochastic, temporal processes of managing cheetah population in Kenya. The model predicts likely anagement decisions made by various actors within these countries, (e.g., the President, the Environmental Protection Agency, and rural residents and the resulting probability of cheetah extinction following these decisions. By approaching the problem in both its political and ecological contexts one avoids consideration of decisions that, while beneficial from a purely conservation point of view, are unlikely to be implemented because of conflicting political objectives. Haas’s analysis demonstrates both the promise and challenges of this type of modeling, and he offers suggestions for overcoming inherent technical difficulties such as model calibration. The second paper, by Simon Hoyle and Mark Maunder (Hoyle & Maunder, 2004, uses a Bayesian approach to model population dynamics and the effects of commercial fishing bycatch for the eastern Pacific Ocean spotted dolphin (Stenella attenuata. Their paper provides a good example of why Bayesian analysis is particularly suited to many management problems. Namely, because it allows the integration of disparate pieces of monitoring data in the simultaneous estimation of population parameters; allows forincorporation of expert judgment and data from other systems and species; and provides for explicit consideration of uncertainty in decision–making. Alternative management scenarios can then be explored via forward simulations. In the third paper, Chris Fonnesbeck and Mike Conroy (Fonnesbeck & Conroy, 2004 present an integrated approach for estimating parameters and predicting abundance of American black duck (Anas rubripes populations. They also employ a ayesian approach and overcome some of the computational challenges by using Markov chain–Monte Carlo methods. Ring–recovery and harvest data are used to estimate fall age ratios under alternative reproductive models. These in turn are used to

  17. Cryptic population dynamics: rapid evolution masks trophic interactions.

    Directory of Open Access Journals (Sweden)

    Takehito Yoshida

    2007-09-01

    Full Text Available 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.

  18. Algal taxonomy forum: Algal Taxonomist, Let Serendipity Reign!

    Science.gov (United States)

    Druehl, Louis

    2013-04-01

    The publication of a mini-review by Olivier De Clerck et al. in this issue of the Journal of Phycology presented an opportunity to open a dialogue on challenges faced by contemporary algal taxonomists. The Editorial Office solicited the following two additional contributions in response to De Clerck et al.'s paper; the responses were edited solely for clarity, space and format.

  19. Dynamics of Betula ermanni population in subalpine vegetation in Changbai Mountain, Northeast China

    Institute of Scientific and Technical Information of China (English)

    Zou Chunjing; Han Shijie; Wang Xiaochun

    1999-01-01

    Betula ermanni population was divided into three groups: the upper population (2 000~2 200 m), the middle population (1 700~2000 m), and the down population (1 400~1 700 m) in Changbai Mountain. The dynamics of Betula ermanni populations in subalpine vegetation are studied and the population life table,fecundity schedule, survival curves, age structure, and fecundity curves were established. The results showed that the middle population is obviously the transition from the upper population to the down population.

  20. A spatial ecosystem and populations dynamics model (SEAPODYM) Modeling of tuna and tuna-like populations

    Science.gov (United States)

    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

  1. EVOLUTIONARY DYNAMIC MODEL OF POPULATION WITH NICHE CONSTRUCTION AND ITS APPLICATION RESEARCH

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on the theories and approaches in biomechanics, the mechanism and pattern of niche construction were discussed systematically. Through establishing the spatial pattern of niche and its measuring-fitness formula, and the dynamic system models of single- and two-population with niche construction, including corresponding theoretical analysis and numerical simulation on their evolutionary dynamics of population and the mechanism of competitive coexistence, the co-evolutionary relationship between organisms and their environments was revealed. The results indicate that population dynamics is governed by positive feedback between primary ecological factors and resource content.Niche construction generates an evolutionary effect in system by influencing the fitness of population. A threshold effect exists in single population dynamic system. In dynamic system of two competitive populations, niche construction can lead to alternative competitive consequences, which may be a potential mechanism to explain the competitive coexistence of species.

  2. Algal Systems for Hydrogen Photoproduction

    Energy Technology Data Exchange (ETDEWEB)

    Ghirardi, Maria L [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-10-08

    The National Renewable Energy Laboratory (NREL), under the guidance of Drs. Michael Seibert (retired, Fellow Emeritus) and Maria Ghirardi (Fellow), led 15 years of research addressing the issue of algal H2 photoproduction. This project resulted in greatly increased rates and yields of algal hydrogen production; increased understanding of the H2 metabolism in the green alga, Chlamydomonas reinhardtii; expanded our knowledge of other physiological aspects relevant to sustained algal photosynthetic H2 production; led to the genetic identification, cloning and manipulation of algal hydrogenase genes; and contributed to a broader, fundamental understanding of the technical and scientific challenges to improving the conversion efficiencies in order to reach the U.S. Department of Energy’s Fuel Cell Technologies Office’s targets. Some of the tangible results are: (i) 64 publications and 6 patents, (ii) international visibility to NREL, (iii) reinvigoration of national and international biohydrogen research, and (iv) research progress that helped stimulate new funding from other DOE and non-DOE programs, including the AFOSR and the DOE Office of Science.

  3. From home range dynamics to population cycles: validation and realism of a common vole population model for pesticide risk assessment.

    Science.gov (United States)

    Wang, Magnus

    2013-04-01

    Despite various attempts to establish population models as standard tools in pesticide risk assessment, population models still receive limited acceptance by risk assessors and authorities in Europe. A main criticism of risk assessors is that population models are often not, or not sufficiently, validated. Hence the realism of population-level risk assessments conducted with such models remains uncertain. We therefore developed an individual-based population model for the common vole, Microtus arvalis, and demonstrate how population models can be validated in great detail based on published data. The model is developed for application in pesticide risk assessment, therefore, the validation covers all areas of the biology of the common vole that are relevant for the analysis of potential effects and recovery after application of pesticides. Our results indicate that reproduction, survival, age structure, spatial behavior, and population dynamics reproduced from the model are comparable to field observations. Also interannual population cycles, which are frequently observed in field studies of small mammals, emerge from the population model. These cycles were shown to be caused by the home range behavior and dispersal. As observed previously in the field, population cycles in the model were also stronger for longer breeding season length. Our results show how validation can help to evaluate the realism of population models, and we discuss the importance of taking field methodology and resulting bias into account. Our results also demonstrate how population models can help to test or understand biological mechanisms in population ecology.

  4. Algal assay research in programs for Euthrophic Lake management: laboratory and field studies

    Energy Technology Data Exchange (ETDEWEB)

    Lindmark, G.

    1979-01-01

    The present study is an attempt to clarify whether relations between viruses (cyanophages) and their algal hosts can be affected by manipulations in the environment. Is is possible to activate cyanophages and accelerate lysis of blue-green algal populations or to enhance the resistance of blue-green algae to attack from cynaophages. The experiments presented here were performed under laboratory conditions with a well-known algal - canophage system, Plectonema boryanum and cyanophage LPP-1 (attacking strains of Lyngbya, Phormidium and Plectonema). The work was done in close connection with field experiments on natural blue-green algal communities, however, because the nature of the induced blue-green algal collapse in plastic enclosures suggested lysis of the algal cells. The rate of LPP-1 cyanophage replication and lysis of plectonema was studied in relation to: (a) pH alterations by CO/sub 2//air additions, (b) algal host culture age and density, (c) nutrient concentrations and (d) presence of additional algal species.

  5. Mosquito population dynamic (diptera: culicidae in a eutrophised dam

    Directory of Open Access Journals (Sweden)

    ED. Wermelinger

    Full Text Available This study observed the mosquito population in a rural eutrophised dam. Larvae of L3 and L4 stages and pupae were dipped out during twelve month collections and the reared to the adult stage for identification. The collections were done along nine metres from the edge of the dam divided in three parts (P1, P2 and P3, each part being 3 m long. P1 did not have vegetation (grass along its edge,which would reach or sink into the water to promote some shade on the marginal water. A total of 217 adults of four species was identified with the following constancies and frequencies: Culex quinquefasciatus (Say, 1823 (83% and 40.6%, Anopheles (Nyssorhynchus evansae (Brèthes, 1926 (92% and 26.7%, Anopheles (Nyssorhynchus rangeli (Gabaldon, Cova Garcia and Lopez, 1940 (83% and 14.3% and Culex nigripalpus (Theobald, 1901 (33% and 18.4%. C. quinquefasciatus, A. evansae, A. rangeli and C. nigripalpus were more frequent in the quarters Nov./Dec./Jan. (85.7%, May/June/July (75%, Aug./Sept./Oct. (29.4% and Aug./Sept./Oct. (23.5% particularly in the months of December (88.4% Sept.tember (48.94, (38.3 and August (47.62 respectively. The presence of C. quinquefasciatus and the high incidence of Daphinia sp. and also the levels of Organic Nitrogen (0.28 mg/L and of total Phosphorus (0.02 mg/L are indications of the eutrophication of the dam. There was a difference regarding the total of Anopheles (A. avansae + A. rangeli and Culex species (C. quinquefasciatus + C. nigripalpis between P1 and P2 (χ² = 0.0097, P1 and P3 (χ² = 0.0005, but not between P2 and P3 (χ² = 0.2045.The high C. quinquefasciatus constancy and frequency were confirmed to be a good biological indicator for a eutrophised environment and A. evansae showed a good potential for this environment. Vegetation can be an important factor for anopheline population dynamic also in eutrophic breeding sites.

  6. Mosquito population dynamic (Diptera: Culicidae) in a eutrophised dam.

    Science.gov (United States)

    Wermelinger, E D; Benigno, C V; Machado, R N M; Cabello, P H; Meira, A M; Ferreira, A P; Zanuncio, J C

    2012-11-01

    This study observed the mosquito population in a rural eutrophised dam. Larvae of L3 and L4 stages and pupae were dipped out during twelve month collections and the reared to the adult stage for identification. The collections were done along nine metres from the edge of the dam divided in three parts (P1, P2 and P3), each part being 3 m long. P1 did not have vegetation (grass) along its edge,which would reach or sink into the water to promote some shade on the marginal water. A total of 217 adults of four species was identified with the following constancies and frequencies: Culex quinquefasciatus (Say, 1823) (83% and 40.6%), Anopheles (Nyssorhynchus) evansae (Brèthes, 1926) (92% and 26.7%), Anopheles (Nyssorhynchus) rangeli (Gabaldon, Cova Garcia and Lopez, 1940) (83% and 14.3%) and Culex nigripalpus (Theobald, 1901) (33% and 18.4%). C. quinquefasciatus, A. evansae, A. rangeli and C. nigripalpus were more frequent in the quarters Nov./Dec./Jan. (85.7%), May/June/July (75%), Aug./Sept./Oct. (29.4%) and Aug./Sept./Oct. (23.5%) particularly in the months of December (88.4%) Sept.tember (48.94), (38.3) and August (47.62) respectively. The presence of C. quinquefasciatus and the high incidence of Daphinia sp. and also the levels of Organic Nitrogen (0.28 mg/L) and of total Phosphorus (0.02 mg/L) are indications of the eutrophication of the dam. There was a difference regarding the total of Anopheles (A. avansae + A. rangeli) and Culex species (C. quinquefasciatus + C. nigripalpis) between P1 and P2 (χ(2) = 0.0097), P1 and P3 (χ(2) = 0.0005), but not between P2 and P3 (χ(2) = 0.2045).The high C. quinquefasciatus constancy and frequency were confirmed to be a good biological indicator for a eutrophised environment and A. evansae showed a good potential for this environment. Vegetation can be an important factor for anopheline population dynamic also in eutrophic breeding sites.

  7. Quantifying Salmonella population dynamics in water and biofilms.

    Science.gov (United States)

    Sha, Qiong; Vattem, Dhiraj A; Forstner, Michael R J; Hahn, Dittmar

    2013-01-01

    Members of the bacterial genus Salmonella are recognized worldwide as major zoonotic pathogens often found to persist in non-enteric environments including heterogeneous aquatic biofilms. In this study, Salmonella isolates that had been detected repeatedly over time in aquatic biofilms at different sites in Spring Lake, San Marcos, Texas, were identified as serovars Give, Thompson, Newport and -:z10:z39. Pathogenicity results from feeding studies with the nematode Caenorhabditis elegans as host confirmed that these strains were pathogenic, with Salmonella-fed C. elegans dying faster (mean survival time between 3 and 4 days) than controls, i.e., Escherichia coli-fed C. elegans (mean survival time of 9.5 days). Cells of these isolates inoculated into water at a density of up to 10(6) ml(-1) water declined numerically by 3 orders of magnitude within 2 days, reaching the detection limit of our quantitative polymerase chain reaction (qPCR)-based quantification technique (i.e., 10(3) cells ml(-1)). Similar patterns were obtained for cells in heterogeneous aquatic biofilms developed on tiles and originally free of Salmonella that were kept in the inoculated water. Cell numbers increased during the first days to more than 10(7) cells cm(-2), and then declined over time. Ten-fold higher cell numbers of Salmonella inoculated into water or into biofilm resulted in similar patterns of population dynamics, though cells in biofilms remained detectable with numbers around 10(4) cells cm(-2) after 4 weeks. Independent of detectability by qPCR, samples of all treatments harbored viable salmonellae that resembled the inoculated isolates after 4 weeks of incubation. These results demonstrate that pathogenic salmonellae were isolated from heterogeneous aquatic biofilms and that they could persist and stay viable in such biofilms in high numbers for some time.

  8. Geographic coupling of juvenile and adult habitat shapes spatial population dynamics of a coral reef fish

    NARCIS (Netherlands)

    Huijbers, C.M.; Nagelekerken, I.; Debrot, A.O.; Jongejans, E.

    2013-01-01

    Marine spatial population dynamics are often addressed with a focus on larval dispersal, without taking into account movement behavior of individuals in later life stages. Processes occurring during demersal life stages may also drive spatial population dynamics if habitat quality is perceived diffe

  9. Species-specific earthworm population responses in relation to flooding dynamics in a Dutch floodplain soil

    NARCIS (Netherlands)

    Zorn, M.I.; Gestel, van C.A.M.; Eijsackers, H.J.P.

    2005-01-01

    Earthworms dominate the animal biomass in moist floodplain soils. They are known to survive long periods in aerated water, but little is known about earthworm population dynamics in floodplain systems with changing inundation frequencies. This study determined earthworm population dynamics in a floo

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

    Energy Technology Data Exchange (ETDEWEB)

    Oroji, Amin; Omar, Mohd bin [Institute of Mathematical Sciences, Faculty of Science University of Malaya, 50603 Kuala Lumpur, Malaysia amin.oroji@siswa.um.edu.my, mohd@um.edu.my (Malaysia); Yarahmadian, Shantia [Mathematics Department Mississippi State University, USA Syarahmadian@math.msstate.edu (United States)

    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.

  11. Population dynamic of the swallowtail butterfly, Papilio polytes (Lepidoptera: Papilionidae) in dry and wet seasons

    OpenAIRE

    SUWARNO

    2010-01-01

    Suwarno (2010) Population dynamic of the swallowtail butterfly, Papilio polytes (Lepidoptera: Papilionidae) in dry and wet seasons. Biodiversitas 11: 19-23. The population dynamic of Papilio polytes L. (Lepidoptera: Papilionidae) in dry and wet seasons was investigated in the citrus orchard in Tasek Gelugor, Pulau Pinang, Malaysia. Population of immature stages of P. polytes was observed alternate day from January to March 2006 (dry season, DS), from April to July 2006 (secondary wet season, ...

  12. Data Driven Approach for High Resolution Population Distribution and Dynamics Models

    Energy Technology Data Exchange (ETDEWEB)

    Bhaduri, Budhendra L [ORNL; Bright, Eddie A [ORNL; Rose, Amy N [ORNL; Liu, Cheng [ORNL; Urban, Marie L [ORNL; Stewart, Robert N [ORNL

    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.

  13. Intraspecific Competition and Population Dynamics of Aedes aegypti

    Science.gov (United States)

    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.

  14. Smith, Malthus and Recent Evidence in Global Population Dynamics

    OpenAIRE

    Xiao Jiang; Luis Villanueva

    2015-01-01

    In conventional economic theories, population is determined outside of the economic system. However, classical political economists such as Adam Smith and Thomas Malthus have long argued for the endogenous determination of population, hence establishing a connection between economics and demography. Foley (2000) used empirically established global per capita output-fertility schedule based on the 1960-1992 Extended Penn World Tables to project the population stabilizing level of world per cap...

  15. Algal biofuels: challenges and opportunities.

    Science.gov (United States)

    Leite, Gustavo B; Abdelaziz, Ahmed E M; Hallenbeck, Patrick C

    2013-10-01

    Biodiesel production using microalgae is attractive in a number of respects. Here a number of pros and cons to using microalgae for biofuels production are reviewed. Algal cultivation can be carried out using non-arable land and non-potable water with simple nutrient supply. In addition, algal biomass productivities are much higher than those of vascular plants and the extractable content of lipids that can be usefully converted to biodiesel, triacylglycerols (TAGs) can be much higher than that of the oil seeds now used for first generation biodiesel. On the other hand, practical, cost-effective production of biofuels from microalgae requires that a number of obstacles be overcome. These include the development of low-cost, effective growth systems, efficient and energy saving harvesting techniques, and methods for oil extraction and conversion that are environmentally benign and cost-effective. Promising recent advances in these areas are highlighted.

  16. Confidence interval for number of population in dynamical stochastic exponential population growth models

    Directory of Open Access Journals (Sweden)

    Morteza Khodabin

    2013-06-01

    Full Text Available In this paper, the confidence interval for the solution of stochastic exponential population growth model where the so-called parameter, population growth rate is not completely definite and it depends on some random environmental effects is obtained. We use Iran population data in the period 1921-2006 as an example.

  17. Dynamic of population-dynamics in a medically important snail species Lymnaea (Radix Luteola (Lamarck

    Directory of Open Access Journals (Sweden)

    T. K. Misra

    1993-09-01

    Full Text Available The life-cycle parameters of the snail Lymnaea (Radix luteola and the factors influencing the same have been studied under laboratory conditions. Ins each month, from July 1990 to June 1991, a batch of 100 zero-day old individual were considered for studies. The snails of April batch survived for 19.42 days while those in December batch survived for 87.45 days. The May batch individual though survived for 65.67 days gained maximum shell size (15.84 mm in length and body weight (419.87 mg. All individuals of April batch died prior to attainment of sexual maturity. In the remaining 11 batches the snails became sexually mature between 32 and 53 days. At this stage, they were with varying shell lengths, 9.3 mm to 13,11 mm in respect to batches. The reproduction period varied from 1-67 days. An individual laid, on an average, 0,25 (March batch to 443.67 (May batch eggs in its life-span. A batch of such snails would leave 24312, 22520, 720268, 80408, 76067, 418165, 214, 9202, 0, 0, 2459386 and 127894 individuals at the end of 352nd day. Since the environmental conditions were almost similar the 'dynamic' of population dynamics seems to be involved with the 'strain' of the snail individuals of the batches concerned.

  18. Population dynamics of some coccids (Coccoidea: Hemiptera) infesting sandal (Santalum album) in Bangalore, India

    Institute of Scientific and Technical Information of China (English)

    Ramachandran Sundararaj; Raja Muthukrishnan

    2011-01-01

    A study was conducted to investigate the population dynamics of four important coccids viz., Aonidiella orientalis (Newstead), Ceroplastes actiniformis Green, Cardiococcus bivalvata (Green) and Parasaissetia nigra (Nietner) infesting sandal in Bangalore, India. Meteorological data viz., monthly mean maximum and minimum temperatures,morning and evening relative humidity and total rainfall were also collected during the experimental period for statistical analysis to ascertain their influence on the population of ceccids. The results show that all the four coccids are infesting sandal throughout the year. Maximum temperature exhibited significantly negative correlation with the population dynamics of A.orientalis, while other weather parameters did not show much influence on its incidence. In case of C. bivalvata, minimum temperature and morning relative humidity exhibited significant positive correlation with its population dynamics while other weather parameters had less significant effect on its population dynamics. For C.actiniformis and P. nigra, none of the weather factors seem to have influence on their incidences.

  19. Suppression of Beneficial Mutations in Dynamic Microbial Populations

    Science.gov (United States)

    Bittihn, Philip; Hasty, Jeff; Tsimring, Lev S.

    2017-01-01

    Quantitative predictions for the spread of mutations in bacterial populations are essential to interpret evolution experiments and to improve the stability of synthetic gene circuits. We derive analytical expressions for the suppression factor for beneficial mutations in populations that undergo periodic dilutions, covering arbitrary population sizes, dilution factors, and growth advantages in a single stochastic model. We find that the suppression factor grows with the dilution factor and depends nontrivially on the growth advantage, resulting in the preferential elimination of mutations with certain growth advantages. We confirm our results by extensive numerical simulations.

  20. Population dynamics of a natural red deer population over 200 years detected via substantial changes of genetic variation.

    Science.gov (United States)

    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.

  1. Development and validation of an individual based Daphnia magna population model: The influence of crowding on population dynamics

    NARCIS (Netherlands)

    Preuss, T.G.; Hammers-Wirtz, M.; Hommen, U.; Rubach, M.N.; Ratte, H.T.

    2009-01-01

    An individual-based model was developed to predict the population dynamics of Daphnia magna at laboratory conditions from individual life-history traits observed in experiments with different feeding conditions. Within the model, each daphnid passes its individual life cycle including feeding on alg

  2. The demographic drivers of local population dynamics in two rare migratory birds.

    Science.gov (United States)

    Schaub, Michael; Reichlin, Thomas S; Abadi, Fitsum; Kéry, Marc; Jenni, Lukas; Arlettaz, Raphaël

    2012-01-01

    The exchange of individuals among populations can have strong effects on the dynamics and persistence of a given population. Yet, estimation of immigration rates remains one of the greatest challenges for animal demographers. Little empirical knowledge exists about the effects of immigration on population dynamics. New integrated population models fitted using Bayesian methods enable simultaneous estimation of fecundity, survival and immigration, as well as the growth rate of a population of interest. We applied this novel analytical framework to the demography of two populations of long-distance migratory birds, hoopoe Upupa epops and wryneck Jynx torquilla, in a study area in south-western Switzerland. During 2002-2010, the hoopoe population increased annually by 11%, while the wryneck population remained fairly stable. Apparent juvenile and adult survival probability was nearly identical in both species, but fecundity and immigration were slightly higher in the hoopoe. Hoopoe population growth rate was strongly correlated with juvenile survival, fecundity and immigration, while that of wrynecks strongly correlated only with immigration. This indicates that demographic components impacting the arrival of new individuals into the populations were more important for their dynamics than demographic components affecting the loss of individuals. The finding that immigration plays a crucial role in the population growth rates of these two rare species emphasizes the need for a broad rather than local perspective for population studies, and the development of wide-scale conservation actions.

  3. Population dynamics of aquatic snails in Pampulha reservoir

    Directory of Open Access Journals (Sweden)

    J. R. Freitas

    1987-01-01

    Full Text Available 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/[square metre]; 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.

  4. Causes and consequences of complex population dynamics in an annual plant, Cardamine pensylvanica

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    OpenAIRE

    Jonas Cremer; Anna Melbinger; Erwin Frey

    2012-01-01

    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 c...

  6. [The relationship between population dynamics and the process of development: an interdependence requiring the definition of population policies].

    Science.gov (United States)

    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

  7. Dynamics of a physiologically structured population in a time-varying environment

    DEFF Research Database (Denmark)

    Heilmann, Irene Louise Torpe; Starke, Jens; Andersen, Ken Haste;

    2016-01-01

    or less regularly. In order to understand the interaction between an external environmental forcing and the internal dynamics in a population, we examine the response of a physiologically structured population model to a periodic variation in the food resource. We explore the addition of forcing in two......Physiologically structured population models have become a valuable tool to model the dynamics of populations. In a stationary environment such models can exhibit equilibrium solutions as well as periodic solutions. However, for many organisms the environment is not stationary, but varies more...

  8. Dynamical Mueller's Ratchet: Population Size Dependence of Evolutionary Paths in Bacteria

    Science.gov (United States)

    Lorenz, Dirk; Park, Jeong-Man; Deem, Michael; Michael Deem Team

    2011-03-01

    Experimental evolution has recently enabled the complete quantitative description of small-dimensional fitness landscapes. Quasispecies theory allows the mathematical modeling of evolution on such a landscape. Typically, analytic solutions for these models are only exactly solvable for the case of an infinite population. Here we use a functional integral representation of population dynamics and solve it using the Schwinger Boson method. This allows us to compute the first-order correction to the average fitness for finite populations. We will use these results to explain the experimental observations of dynamics of evolution in finite populations.

  9. Fast game theory coupled to slow population dynamics: the case of domestic cat populations.

    Science.gov (United States)

    Auger, P; Pontier, D

    1998-02-01

    We study a deterministic model of a population where individuals alternatively adopt hawk and dove tactics. It is assumed that the hawk and dove individuals compete for some resources at a fast time scale. This fast part of the model is coupled to a slow part that describes the growth of the population. It is shown that, in a constant game matrix, the population grows according to a logistic curve whose r and K parameters are related to the payoff of the tactics. Results show that the highest population density is obtained when all individuals are dove. We also study a density-dependent game matrix for which the gain is a function of the population density. In this case, we show that two stable equilibria can occur, a first one at low density with a high proportion of hawk individuals and a second one at large density with a low proportion of hawk individuals. Our model is applied to domestic cat populations for which the behavior of individuals in competition with one another can be modeled by two tactics: hawk and dove. Such tactics change with density of population. The results of the model agree well with observed data: high-density populations of domestic cats are mainly doves, whereas low-density populations are mainly hawks.

  10. Methods for removing contaminants from algal oil

    Energy Technology Data Exchange (ETDEWEB)

    Lupton, Francis Stephen

    2016-09-27

    Methods for removing contaminants from algal oil are provided. In an embodiment, a method comprises the steps of combining a sulfuric acid-aqueous solution that has a pH of about 1 or less with a contaminant-containing algal oil at treatment conditions effective to form an effluent. The effluent comprises a treated algal oil phase and contaminants in an acidic aqueous phase. The contaminants comprise metals, phosphorus, or combinations thereof. The acidic aqueous phase is removed from the effluent to form a contaminant-depleted algal oil.

  11. Modelling population dynamics model formulation, fitting and assessment using state-space methods

    CERN Document Server

    Newman, K B; Morgan, B J T; King, R; Borchers, D L; Cole, D J; Besbeas, P; Gimenez, O; Thomas, L

    2014-01-01

    This book gives a unifying framework for estimating the abundance of open populations: populations subject to births, deaths and movement, given imperfect measurements or samples of the populations.  The focus is primarily on populations of vertebrates for which dynamics are typically modelled within the framework of an annual cycle, and for which stochastic variability in the demographic processes is usually modest. Discrete-time models are developed in which animals can be assigned to discrete states such as age class, gender, maturity,  population (within a metapopulation), or species (for multi-species models). The book goes well beyond estimation of abundance, allowing inference on underlying population processes such as birth or recruitment, survival and movement. This requires the formulation and fitting of population dynamics models.  The resulting fitted models yield both estimates of abundance and estimates of parameters characterizing the underlying processes.  

  12. Midcontinental Native American population dynamics and late Holocene hydroclimate extremes

    Science.gov (United States)

    Bird, Broxton W.; Wilson, Jeremy J.; Gilhooly, William P., III; Steinman, Byron A.; Stamps, Lucas

    2017-01-01

    Climate’s influence on late Pre-Columbian (pre-1492 CE), maize-dependent Native American populations in the midcontinental United States (US) is poorly understood as regional paleoclimate records are sparse and/or provide conflicting perspectives. Here, we reconstruct regional changes in precipitation source and seasonality and local changes in warm-season duration and rainstorm events related to the Pacific North American pattern (PNA) using a 2100-year-long multi-proxy lake-sediment record from the midcontinental US. Wet midcontinental climate reflecting negative PNA-like conditions occurred during the Medieval Climate Anomaly (950–1250 CE) as Native American populations adopted intensive maize agriculture, facilitating population aggregation and the development of urban centers between 1000–1200 CE. Intensifying midcontinental socio-political instability and warfare between 1250–1350 CE corresponded with drier positive PNA-like conditions, culminating in the staggered abandonment of many major Native American river valley settlements and large urban centers between 1350–1450 CE during an especially severe warm-season drought. We hypothesize that this sustained drought interval rendered it difficult to support dense populations and large urban centers in the midcontinental US by destabilizing regional agricultural systems, thereby contributing to the host of socio-political factors that led to population reorganization and migration in the midcontinent and neighboring regions shortly before European contact.

  13. Midcontinental Native American population dynamics and late Holocene hydroclimate extremes

    Science.gov (United States)

    Bird, Broxton W.; Wilson, Jeremy J.; Gilhooly III, William P.; Steinman, Byron A.; Stamps, Lucas

    2017-01-01

    Climate’s influence on late Pre-Columbian (pre-1492 CE), maize-dependent Native American populations in the midcontinental United States (US) is poorly understood as regional paleoclimate records are sparse and/or provide conflicting perspectives. Here, we reconstruct regional changes in precipitation source and seasonality and local changes in warm-season duration and rainstorm events related to the Pacific North American pattern (PNA) using a 2100-year-long multi-proxy lake-sediment record from the midcontinental US. Wet midcontinental climate reflecting negative PNA-like conditions occurred during the Medieval Climate Anomaly (950–1250 CE) as Native American populations adopted intensive maize agriculture, facilitating population aggregation and the development of urban centers between 1000–1200 CE. Intensifying midcontinental socio-political instability and warfare between 1250–1350 CE corresponded with drier positive PNA-like conditions, culminating in the staggered abandonment of many major Native American river valley settlements and large urban centers between 1350–1450 CE during an especially severe warm-season drought. We hypothesize that this sustained drought interval rendered it difficult to support dense populations and large urban centers in the midcontinental US by destabilizing regional agricultural systems, thereby contributing to the host of socio-political factors that led to population reorganization and migration in the midcontinent and neighboring regions shortly before European contact. PMID:28139698

  14. Evolutionary game dynamics in populations with heterogenous structures.

    Directory of Open Access Journals (Sweden)

    Wes Maciejewski

    2014-04-01

    Full Text Available Evolutionary graph theory is a well established framework for modelling the evolution of social behaviours in structured populations. An emerging consensus in this field is that graphs that exhibit heterogeneity in the number of connections between individuals are more conducive to the spread of cooperative behaviours. In this article we show that such a conclusion largely depends on the individual-level interactions that take place. In particular, averaging payoffs garnered through game interactions rather than accumulating the payoffs can altogether remove the cooperative advantage of heterogeneous graphs while such a difference does not affect the outcome on homogeneous structures. In addition, the rate at which game interactions occur can alter the evolutionary outcome. Less interactions allow heterogeneous graphs to support more cooperation than homogeneous graphs, while higher rates of interactions make homogeneous and heterogeneous graphs virtually indistinguishable in their ability to support cooperation. Most importantly, we show that common measures of evolutionary advantage used in homogeneous populations, such as a comparison of the fixation probability of a rare mutant to that of the resident type, are no longer valid in heterogeneous populations. Heterogeneity causes a bias in where mutations occur in the population which affects the mutant's fixation probability. We derive the appropriate measures for heterogeneous populations that account for this bias.

  15. Evolutionary game dynamics in populations with heterogenous structures.

    Science.gov (United States)

    Maciejewski, Wes; Fu, Feng; Hauert, Christoph

    2014-04-01

    Evolutionary graph theory is a well established framework for modelling the evolution of social behaviours in structured populations. An emerging consensus in this field is that graphs that exhibit heterogeneity in the number of connections between individuals are more conducive to the spread of cooperative behaviours. In this article we show that such a conclusion largely depends on the individual-level interactions that take place. In particular, averaging payoffs garnered through game interactions rather than accumulating the payoffs can altogether remove the cooperative advantage of heterogeneous graphs while such a difference does not affect the outcome on homogeneous structures. In addition, the rate at which game interactions occur can alter the evolutionary outcome. Less interactions allow heterogeneous graphs to support more cooperation than homogeneous graphs, while higher rates of interactions make homogeneous and heterogeneous graphs virtually indistinguishable in their ability to support cooperation. Most importantly, we show that common measures of evolutionary advantage used in homogeneous populations, such as a comparison of the fixation probability of a rare mutant to that of the resident type, are no longer valid in heterogeneous populations. Heterogeneity causes a bias in where mutations occur in the population which affects the mutant's fixation probability. We derive the appropriate measures for heterogeneous populations that account for this bias.

  16. Population dynamics of active and total ciliate populations in arable soil amended with wheat

    DEFF Research Database (Denmark)

    Ekelund, F.; Frederiksen, Helle B.; Ronn, R.

    2002-01-01

    of ciliate growth, the population of cystic ciliates increased 100-fold. We suggest that internal population regulation is the major factor governing ciliate encystment and that the rate of encystment depends on ciliate density. This model provides a quantitative explanation of ciliatostasis and can explain...

  17. Effective population size and evolutionary dynamics in outbred laboratory populations of Drosophila

    Indian Academy of Sciences (India)

    Laurence D. Mueller; Amitabh Joshi; Marta Santos; Michael R. Rose

    2013-12-01

    Census population size, sex-ratio and female reproductive success were monitored in 10 laboratory populations of Drosophila melanogaster selected for different ages of reproduction. With this demographic information, we estimated eigenvalue, variance and probability of allele loss effective population sizes. We conclude that estimates of effective size based on genefrequency change at a few loci are biased downwards. We analysed the relative roles of selection and genetic drift in maintaining genetic variation in laboratory populations of Drosophila. We suggest that rare, favourable genetic variants in our laboratory populations have a high chance of being lost if their fitness effect is weak, e.g. 1% or less. However, if the fitness effect of this variation is 10% or greater, these rare variants are likely to increase to high frequency. The demographic information developed in this study suggests that some of our laboratory populations harbour more genetic variation than expected. One explanation for this finding is that part of the genetic variation in these outbred laboratory Drosophila populations may be maintained by some form of balancing selection. We suggest that, unlike bacteria, medium-term adaptation of laboratory populations of fruit flies is not primarily driven by new mutations, but rather by changes in the frequency of preexisting alleles.

  18. Plankton communities and summertime declines in algal abundance associated with low dissolved oxygen in the Tualatin River, Oregon

    Science.gov (United States)

    Carpenter, Kurt D.; Rounds, Stewart A.

    2013-01-01

    Phytoplankton populations in the Tualatin River in northwestern Oregon are an important component of the dissolved oxygen (DO) budget of the river and are critical for maintaining DO levels in summer. During the low-flow summer period, sufficient nutrients and a long residence time typically combine with ample sunshine and warm water to fuel blooms of cryptophyte algae, diatoms, green and blue-green algae in the low-gradient, slow-moving reservoir reach of the lower river. Algae in the Tualatin River generally drift with the water rather than attach to the river bottom as a result of moderate water depths, slightly elevated turbidity caused by suspended colloidal material, and dominance of silty substrates. Growth of algae occurs as if on a “conveyor belt” of streamflow, a dynamic system that is continually refreshed with inflowing water. Transit through the system can take as long as 2 weeks during the summer low-flow period. Photosynthetic production of DO during algal blooms is important in offsetting oxygen consumption at the sediment-water interface caused by the decomposition of organic matter from primarily terrestrial sources, and the absence of photosynthesis can lead to low DO concentrations that can harm aquatic life. The periods with the lowest DO concentrations in recent years (since 2003) typically occur in August following a decline in algal abundance and activity, when DO concentrations often decrease to less than State standards for extended periods (nearly 80 days). Since 2003, algal populations have tended to be smaller and algal blooms have terminated earlier compared to conditions in the 1990s, leading to more frequent declines in DO to levels that do not meet State standards. This study was developed to document the current abundance and species composition of phytoplankton in the Tualatin River, identify the possible causes of the general decline in algae, and evaluate hypotheses to explain why algal blooms diminish in midsummer. Plankton

  19. Ecological change, group territoriality, and population dynamics in Serengeti lions.

    Science.gov (United States)

    Packer, Craig; Hilborn, Ray; Mosser, Anna; Kissui, Bernard; Borner, Markus; Hopcraft, Grant; Wilmshurst, John; Mduma, Simon; Sinclair, Anthony R E

    2005-01-21

    Territorial behavior is expected to buffer populations against short-term environmental perturbations, but we have found that group living in African lions causes a complex response to long-term ecological change. Despite numerous gradual changes in prey availability and vegetative cover, regional populations of Serengeti lions remained stable for 10- to 20-year periods and only shifted to new equilibria in sudden leaps. Although gradually improving environmental conditions provided sufficient resources to permit the subdivision of preexisting territories, regional lion populations did not expand until short-term conditions supplied enough prey to generate large cohorts of surviving young. The results of a simulation model show that the observed pattern of "saltatory equilibria" results from the lions' grouping behavior.

  20. An overview of the population dynamics in Malaysia.

    Science.gov (United States)

    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

  1. State aggregation and population dynamics in linear systems.

    Science.gov (United States)

    Rowe, Jonathan E; Vose, Michael D; Wright, Alden H

    2005-01-01

    We consider complex systems that are composed of many interacting elements, evolving under some dynamics. We are interested in characterizing the ways in which these elements may be grouped into higher-level, macroscopic states in a way that is compatible with those dynamics. Such groupings may then be thought of as naturally emergent properties of the system. We formalize this idea and, in the case that the dynamics are linear, prove necessary and sufficient conditions for this to happen. In cases where there is an underlying symmetry among the components of the system, group theory may be used to provide a strong sufficient condition. These observations are illustrated with some artificial life examples.

  2. Muskrat population dynamics and vegetation utilization : A management plan : Report on 1980 field season

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Report for the 1980 field season on a study of muskrat population dynamics and vegetation utilization, being led by Utah State University for a doctorate...

  3. The population dynamical implications of male-biased parasitism in different mating systems.

    Directory of Open Access Journals (Sweden)

    Martin R Miller

    Full Text Available Although there is growing evidence that males tend to suffer higher levels of parasitism than females, the implications of this for the population dynamics of the host population are not yet understood. Here we build on an established 'two-sex' model and investigate how increased susceptibility to infection in males affects the dynamics, under different mating systems. We investigate the effect of pathogenic disease at different case mortalities, under both monogamous and polygynous mating systems. If the case mortality is low, then male-biased parasitism appears similar to unbiased parasitism in terms of its effect on the population dynamics. At higher case mortalities, we identified significant differences between male-biased and unbiased parasitism. A host population may therefore be differentially affected by male-biased and unbiased parasitism. The dynamical outcome is likely to depend on a complex interaction between the host's mating system and demography, and the parasite virulence.

  4. Modeling regional population-employment dynamics across different sectors of the economy

    NARCIS (Netherlands)

    Graaff, T. de; Oort, F.G. van; Florax, R.

    2012-01-01

    An important subset of the literature on agglomeration externalities hypothesizes that intrasectoral and intersectoral relations are endogenously determined in models of local and regional economic growth. Remarkably, structural adjustment models describing the spatio-temporal dynamics of population

  5. Muskrat population dynamics and vegetation utilization : A management plan : Quarterly progress report : April, May, June 1979

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Quarterly report on a study of muskrat population dynamics and vegetation utilization, being led by Utah State University for a doctorate dissertation. The study...

  6. Approximation of solutions to retarded differential equations with applications to population dynamics

    Directory of Open Access Journals (Sweden)

    D. Bahuguna

    2005-01-01

    Full Text Available We consider a retarded differential equation with applications to population dynamics. We establish the convergence of a finite-dimensional approximations of a unique solution, the existence and uniqueness of which are also proved in the process.

  7. Population dynamics in central and edge populations of a narrowly endemic plant.

    Science.gov (United States)

    Aikens, Melissa L; Roach, Deborah A

    2014-07-01

    Species' range limits can be caused by environmental gradients, and in such cases, abundance is thought to be highest in the center of a species range and decline towards the edge (the abundant-center model). Although in theory decreased abundance is caused by a decline in performance at the edge, it has been shown that performance and abundance are not necessarily related. Few studies have compared abundance and performance in center and edge populations of endemic species, whose ranges may be restricted by the availability of specialized habitat rather than environmental gradients across their range. Additionally, range-wide studies that examine both northern and southern edge populations are rare. We used Roan Mountain rattlesnake-root (Prenanthes roanensis), a perennial plant endemic to the Southern Appalachians (USA), to compare abundance and performance between central populations and populations at the northern and southern edges of the range. To account for multiple fitness components across the life cycle, we measured performance of edge populations as vital-rate contributions to population growth rate compared to the center. Abundance did not decline at the range edge, but some vital-rate contributions were lower in edge populations compared to central populations. However, each edge population differed in which vital-rate contributions were lower compared to the center. Our results do not support the abundant-center model, and it appears that local factors are important in structuring the range of this endemic species. It is important to recognize that when implementing conservation or management plans, populations in close proximity may have substantial variation in demographic rates due to differences in the local environment.

  8. Population, environment dynamics, poverty and quality of life in China.

    Science.gov (United States)

    Gu, B

    1996-12-01

    This article focuses on the growth in poverty, environmental concerns, and Chinese government efforts to eliminate poverty with integrated programs. China had 1.2 billion people in February 1995, or 20% of total world population on 7% of the world's arable land. The rate of natural increase was 1.1% in 1996. China's population could double to 2.4 billion by 2060. About 14 million people are added every year. China has about 300 million women of childbearing age. Even with 1 child per woman, population would grow by 300 million. 18 provinces have population growth over the national average of 1.49%. Many of these provinces are also provinces with high population density, high poverty ratios, and higher than 2 birth orders. The highest growth is in western China. Poor households have a lower quality of life, more disabled members, high rates of endemic disease, and illiteracy. Among the very poor without adequate food or clothing, environmental protection is a meaningless concept. Poverty alleviation strategies have shifted from relief to economic development. State support combined with local resources in a pooling approach pays for poverty alleviation programs. The central government's share will increase until the year 2000. The number of poor was 80 million in 1994 (9% of total population) living in 592 poor counties in remote and mountainous areas. The number of poor was reduced to 65 million in 1996. An integrated approach of family planning and poverty alleviation operates in Jinzhai County of Anhui province. China is determined to reorient to a "service-oriented, client- centered, woman-sensitive, and rural-emphasized approach."

  9. The dynamics of discrete populations and series of events

    CERN Document Server

    Hopcraft, Keith Iain; Ridley, Kevin D

    2014-01-01

    IntroductionReferencesStatistical PreliminariesIntroductionProbability DistributionsMoment-Generating FunctionsDiscrete ProcessesSeries of EventsSummaryFurther ReadingMarkovian Population ProcessesIntroductionBirths and DeathsImmigration and the Poisson ProcessThe Effect of MeasurementCorrelation of CountsSummaryFurther ReadingThe Birth-Death-Immigration ProcessIntroductionRate Equations for the ProcessEquation for the Generating FunctionGeneral Time-Dependent SolutionFluctuation Characteristics of a Birth-Death-Immigration PopulationSampling and Measurement ProcessesCorrelation of CountsSumma

  10. A dynamic urban air pollution population exposure assessment study using model and population density data derived by mobile phone traffic

    Science.gov (United States)

    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.

  11. Modeling complex spatial dynamics of two-population interaction in urbanization process

    CERN Document Server

    Chen, Yanguang

    2013-01-01

    This paper is mainly devoted to lay an empirical foundation for further research on complex spatial dynamics of two-population interaction. Based on the US population census data, a rural and urban population interaction model is developed. Subsequently a logistic equation on percentage urban is derived from the urbanization model so that spatial interaction can be connected mathematically with logistic growth. The numerical experiment by using the discretized urban-rural population interaction model of urbanization shows a period-doubling bifurcation and chaotic behavior, which is identical in patterns to those from the simple mathematical models of logistic growth in ecology. This suggests that the complicated dynamics of logistic growth may come from some kind of the nonlinear interaction. The results from this study help to understand urbanization, urban-rural population interaction, chaotic dynamics, and spatial complexity of geographical systems.

  12. Transients drive the demographic dynamics of plant populations in variable environments

    DEFF Research Database (Denmark)

    McDonald, Jenni L; Stott, Iain; Townley, Stuart;

    2016-01-01

    clear patterns related to growth form. We find a surprising tendency for plant populations to boom rather than bust in response to temporal changes in vital rates and that stochastic growth rates increase with increasing tendency to boom. Synthesis. Transient dynamics contribute significantly......The dynamics of structured plant populations in variable environments can be decomposed into the ‘asymptotic’ growth contributed by vital rates, and ‘transient’ growth caused by deviation from stable stage structure. We apply this framework to a large, global data base of longitudinal studies...... of projection matrix models for plant populations. We ask, what is the relative contribution of transient boom and bust to the dynamic trajectories of plant populations in stochastic environments? Is this contribution patterned by phylogeny, growth form or the number of life stages per population and per...

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

    NARCIS (Netherlands)

    McLean, Nina; Lawson, C.R.; Leech, David; Van de Pol, M.

    2016-01-01

    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

  14. How predation and landscape fragmentation affect vole population dynamics

    DEFF Research Database (Denmark)

    Dalkvist, Trine; Sibly, Richard; Topping, Christopher John

    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...

  15. Mapping Populations: An Objective Measurement of Revolutionary Dynamics

    Science.gov (United States)

    2013-06-01

    achieving common national interest and identifying the parties within states that will breed political discontent and instability is available with the...contract because of government corruption, illegitimate political practices, or repressive policies that incite insurrection where the means and...easier to affect, because it evokes an emotional response from the population in a two dimensional manner. Positive fervor and negative fervor are

  16. A stage-based model of manatee population dynamics

    Science.gov (United States)

    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.

  17. Food-dependent individual growth and population dynamics in fishes

    NARCIS (Netherlands)

    L. Persson; A.M. de Roos

    2006-01-01

    It is long since well established that growth and development in fish individuals are heavily dependent on food intake. Yet, this dependence of individual development on food levels has only to a limited extent been taken into consideration when studying fish population and community processes. Usin

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

    Directory of Open Access Journals (Sweden)

    Alessia Uboni

    Full Text Available 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

  19. Breeding site heterogeneity reduces variability in frog recruitment and population dynamics

    Science.gov (United States)

    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.

  20. Structural perturbations to population skeletons: transient dynamics, coexistence of attractors and the rarity of chaos.

    Directory of Open Access Journals (Sweden)

    Brajendra K Singh

    Full Text Available Simple models of insect populations with non-overlapping generations have been instrumental in understanding the mechanisms behind population cycles, including wild (chaotic fluctuations. The presence of deterministic chaos in natural populations, however, has never been unequivocally accepted. Recently, it has been proposed that the application of chaos control theory can be useful in unravelling the complexity observed in real population data. This approach is based on structural perturbations to simple population models (population skeletons. The mechanism behind such perturbations to control chaotic dynamics thus far is model dependent and constant (in size and direction through time. In addition, the outcome of such structurally perturbed models is [almost] always equilibrium type, which fails to commensurate with the patterns observed in population data.We present a proportional feedback mechanism that is independent of model formulation and capable of perturbing population skeletons in an evolutionary way, as opposed to requiring constant feedbacks. We observe the same repertoire of patterns, from equilibrium states to non-chaotic aperiodic oscillations to chaotic behaviour, across different population models, in agreement with observations in real population data. Model outputs also indicate the existence of multiple attractors in some parameter regimes and this coexistence is found to depend on initial population densities or the duration of transient dynamics. Our results suggest that such a feedback mechanism may enable a better understanding of the regulatory processes in natural populations.

  1. Effects of climate change and variability on population dynamics in a long-lived shorebird

    NARCIS (Netherlands)

    van de Pol, Martijn; Vindenes, Yngvild; Saether, Bernt-Erik; Engen, Steinar; Ens, Bruno J.; Oosterbeek, Kees; Tinbergen, Joost M.

    2010-01-01

    Climate change affects both the mean and variability of climatic variables, but their relative impact on the dynamics of populations is still largely unexplored. Based on a long-term study of the demography of a declining Eurasian Oystercatcher (Haematopus ostralegus) population, we quantify the eff

  2. Dynamics of Microbial Populations during Fermentation of Wines from the Utiel-Requena Region of Spain

    OpenAIRE

    Pardo, Isabel; García, María José; Zúñiga, Manuel; Uruburu, Federico

    1989-01-01

    The dynamics of fungi, yeasts, and lactic acid bacteria during fermentation of four musts were studied. Fungi disappeared quickly in the fermenting must. The lactic acid bacteria population diminished during alcoholic fermentation, then they increased and performed malolactic fermentation. Yeasts grew quickly, reaching maximum populations at different times depending on the vinification treatment.

  3. Site-specific dynamics in remnant populations of Northern Wheatears Oenanthe oenanthe in the Netherlands

    NARCIS (Netherlands)

    Oosten, van H.H.; Turnhout, van C.; Hallmann, C.A.; Majoor, F.; Roodbergen, M.; Schekkerman, H.; Versluijs, R.; Waasdorp, S.; Siepel, H.

    2015-01-01

    Dynamics of populations may be synchronized at large spatial scales, indicating driving forces acting beyond local scales, but may also vary locally as a result of site-specific conditions. Conservation measures for fragmented and declining populations may need to address such local effects to avoid

  4. Modelling of population dynamics of red king crab using Bayesian approach

    Directory of Open Access Journals (Sweden)

    Bakanev Sergey ...

    2012-10-01

    Modeling population dynamics based on the Bayesian approach enables to successfully resolve the above issues. The integration of the data from various studies into a unified model based on Bayesian parameter estimation method provides a much more detailed description of the processes occurring in the population.

  5. Eel population dynamic and habitat relationships in the European southern tip.

    Directory of Open Access Journals (Sweden)

    Ramon José De Miguel

    2015-11-01

    According to our previous results, the eel population in the most southern region in Europe shows similar averages in dynamic population indicators compared to other European areas. On the other hand, no environmental predictors showed major influence on catchability, except for, those related to previous abundant rainfalls.

  6. Strong persistent growth differences govern individual performance and population dynamics in a tropical forest understorey palm

    NARCIS (Netherlands)

    Jansen, M.; Zuidema, P.A.; Anten, N.P.R.; Martínez-Ramos, M.

    2012-01-01

    1. Persistent variation in growth rate between individual plants can have strong effects on population dynamics as fast growers reach the reproductive size at an earlier age and thus potentially contribute more to population growth than slow growers. In tropical forests, such persistent growth diffe

  7. A DYNAMICAL SIGNATURE OF MULTIPLE STELLAR POPULATIONS IN 47 TUCANAE

    Energy Technology Data Exchange (ETDEWEB)

    Richer, Harvey B.; Heyl, Jeremy [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Anderson, Jay; Kalirai, Jason S. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Shara, Michael M. [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 (United States); Dotter, Aaron [Research School of Astronomy and Astrophysics, Australian National University, Weston, ACT 2611 (Australia); Fahlman, Gregory G. [National Research Council, Herzberg Institute of Astrophysics, Victoria, BC V9E 2E7 (Canada); Rich, R. Michael, E-mail: richer@astro.ubc.ca, E-mail: heyl@phas.ubc.ca, E-mail: jayander@stsci.edu, E-mail: jkalarai@stsci.edu, E-mail: mshara@amnh.org, E-mail: aaron.dotter@gmail.com, E-mail: greg.fahlman@nrc-cnrc.gc.ca, E-mail: rmr@astro.ucla.edu [Division of Astronomy and Astrophysics, University of California at Los Angeles, Los Angeles, CA 90095 (United States)

    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.

  8. Population dynamics of Streptococcus mitis in its natural habitat

    DEFF Research Database (Denmark)

    Hohwy, J.; Reinholdt, Jesper; Kilian, Mogens

    2001-01-01

    The purpose of this study was to examine the genetic structure of the typical commensal Streptococcus mitis biovar 1 in its natural habitat in the human oral cavity and pharynx and to investigate the role that selected microbial properties and host, spatial, and temporal factors play in determining...... the structure of the bacterial population. Consecutive samples were collected from buccal and pharyngeal mucosal surfaces of two infants, their four parents, and two elderly individuals over a period of approximately 1 year. A total of 751 isolates identified as S. mitis biovar 1 were typed by restriction...... that previously observed for intestinal populations of Escherichia coli. The study provides evidence of the existence of both transient and persistent clones in adult individuals. In the two infants, however, none of 42 demonstrated clones were detected on more than a single occasion. Statistical calculations...

  9. Two-Population Dynamics in a Growing Network Model

    CERN Document Server

    Ivanova, Kristinka

    2011-01-01

    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.

  10. Worldwide Phylogenetic Distributions and Population Dynamics of the Genus Histoplasma.

    Directory of Open Access Journals (Sweden)

    Marcus de M Teixeira

    2016-06-01

    Full Text Available 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.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.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 important pathogen complex.

  11. Quantification of Dynamic Excitation Potential of Pedestrian Population Crossing Footbridges

    Directory of Open Access Journals (Sweden)

    Stana Žcaronivanović

    2011-01-01

    Full Text Available Due to their slenderness, many modern footbridges may vibrate significantly under pedestrian traffic. Consequently, the vibration serviceability of these structures under human-induced dynamic loading is becoming their governing design criterion. Many current vibration serviceability design guidelines, concerned with prediction of the vibration in the vertical direction, estimate a single response level that corresponds to an "average" person crossing the bridge with the step frequency that matches a footbridge natural frequency. However, different pedestrians have different dynamic excitation potential, and therefore could generate significantly different vibration response of the bridge structure. This paper aims to quantify this potential by estimating the range of structural vibrations (in the vertical direction that could be induced by different individuals and the probability of occurrence of any particular vibration level. This is done by introducing the inter- and intra-subject variability in the walking force modelling. The former term refers to inability of a pedestrian to induce an exactly the same force with each step while the latter refers to different forces (in terms of their magnitude, frequency and crossing speed induced by different people. Both types of variability are modelled using the appropriate probability density functions. The probability distributions were then implemented into a framework procedure for vibration response prediction under a single person excitation. Instead of a single response value obtained using currently available design guidelines, this new framework yields a range of possible acceleration responses induced by different people and a distribution function for these responses. The acceleration ranges estimated are then compared with experimental data from two real-life footbridges. The substantial differences in the dynamic response induced by different people are obtained in both the numerical and

  12. Evolutionary dynamics of fluctuating populations with strong mutualism

    Science.gov (United States)

    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.

  13. Recovery of methanotrophs from disturbance: population dynamics, evenness and functioning.

    Science.gov (United States)

    Ho, Adrian; Lüke, Claudia; Frenzel, Peter

    2011-04-01

    Biodiversity is claimed to be essential for ecosystem functioning, but is threatened by anthropogenic disturbances. Prokaryotes have been assumed to be functionally redundant and virtually inextinguishable. However, recent work indicates that microbes may well be sensitive to environmental disturbance. Focusing on methane-oxidizing bacteria as model organisms, we simulated disturbance-induced mortality by mixing native with sterilized paddy soil in two ratios, 1:4 and 1:40, representing moderate and severe die-offs. Disturbed microcosms were compared with an untreated control. Recovery of activity and populations was followed over 4 months by methane uptake measurements, pmoA-qPCR, pmoA-based terminal restriction fragment length polymorphism and a pmoA-based diagnostic microarray. Diversity and evenness of methanotrophs decreased in disturbed microcosms, but functioning was not compromised. We consistently observed distinctive temporal shifts between type I and type II methanotrophs, and a rapid population growth leading to even higher cell numbers comparing disturbed microcosms with the control. Overcompensating mortality suggested that population size in the control was limited by competition with other bacteria. Overall, methanotrophs showed a remarkable ability to compensate for die-offs.

  14. Population Dynamics of Soil Pseudomonads in the Rhizosphere of Potato (Solanum tuberosum L.)

    OpenAIRE

    Joyce E Loper; Haack, Caryn; Schroth, Milton N.

    1985-01-01

    Rhizosphere population dynamics of seven Pseudomonas fluorescens and Pseudomonas putida strains isolated from rhizospheres of various agricultural plants were studied on potato (Solanum tuberosum L.) in field soil under controlled environmental conditions. Rhizosphere populations of two strains (B10 and B4) were quantitatively related to initial seed piece inoculum levels when plants were grown at −0.3 bar matric potential. At a given inoculum level, rhizosphere populations of strain B4 were ...

  15. Dynamics of biomass and population density of fucus algae of the Kola Bay, Barents Sea

    Directory of Open Access Journals (Sweden)

    Malavenda S. S.

    2016-03-01

    Full Text Available The long-term dynamics of biomass and population density of Fucus distichus and F. vesiculosus in the southern and middle knees of the Kola Bay have been analyzed. The feedbacks between these parameters and their changes over several years have been revealed for the first time. Changing the prevalence of biomass and population density can be considered as an adaptation at the population level to maintain the stability of algae communities in chronic pollution

  16. NREL Algal Biofuels Projects and Partnerships

    Energy Technology Data Exchange (ETDEWEB)

    2016-10-01

    This fact sheet highlights several algal biofuels research and development projects focused on improving the economics of the algal biofuels production process. These projects should serve as a foundation for the research efforts toward algae as a source of fuels and other chemicals.

  17. Population dynamics of mallards breeding in eastern Washington

    Science.gov (United States)

    Dugger, Bruce D.; Coluccy, John M.; Dugger, Katie M.; Fox, Trevor T.; Kraege, Donald K.; Petrie, Mark J.

    2016-01-01

    Variation in regional population trends for mallards breeding in the western United States indicates that additional research into factors that influence demographics could contribute to management and understanding the population demographics of mallards across North America. We estimated breeding incidence and adult female, nest, and brood survival in eastern Washington in 2006 and 2007 by monitoring female mallards with radio telemetry and tested how those parameters were influenced by study year (2006 vs. 2007), landscape type (agricultural vs. natural), and age (second year [SY] vs. after second year [ASY]). We also investigated the effects of female body condition and capture date on breeding incidence, and nest initiation date and hatch date on nest and brood survival, respectively. We included population parameters in a stage-based demographic model and conducted a perturbation analysis to identify which vital rates were most influential on population growth rate (λ). Adult female survival was best modeled with a constant weekly survival rate (0.994, SE = 0.003). Breeding incidence differed between years and was higher for birds in better body condition. Nest survival was higher for ASY females (0.276, SE = 0.118) than SY females (0.066, SE = 0.052), and higher on publicly managed lands (0.383, SE = 0.212) than agricultural (0.114, SE = 0.058) landscapes. Brood survival was best modeled with a constant rate for the 7-week monitoring period (0.50, SE = 0.155). The single variable having the greatest influence on λ was non-breeding season survival, but the combination of parameters from the breeding grounds explained a greater percent of the variance in λ. Mallard population growth rate was most sensitive to changes in non-breeding survival, nest success, brood survival, and breeding incidence. Future management decisions should focus on activities that improve these vital rates if managers want to increase the production of

  18. Do resources or natural enemies drive bee population dynamics in fragmented habitats?

    Science.gov (United States)

    Steffan-Dewenter, Ingolf; Schiele, Susanne

    2008-05-01

    The relative importance of bottom-up or top-down forces has been mainly studied for herbivores but rarely for pollinators. Habitat fragmentation might change driving forces of population dynamics by reducing the area of resource-providing habitats, disrupting habitat connectivity, and affecting natural enemies more than their host species. We studied spatial and temporal population dynamics of the solitary bee Osmia rufa (Hymenoptera: Megachilidae) in 30 fragmented orchard meadows ranging in size from 0.08 to 5.8 ha in an agricultural landscape in central Germany. From 1998 to 2003, we monitored local bee population size, rate of parasitism, and rate of larval and pupal mortality in reed trap nests as an accessible and standardized nesting resource. Experimentally enhanced nest site availability resulted in a steady increase of mean local population size from 80 to 2740 brood cells between 1998 and 2002. Population size and species richness of natural enemies increased with habitat area, whereas rate of parasitism and mortality only varied among years. Inverse density-dependent parasitism in three study years with highest population size suggests rather destabilizing instead of regulating effects of top-down forces. Accordingly, an analysis of independent time series showed on average a negative impact of population size on population growth rates but provides no support for top-down regulation by natural enemies. We conclude that population dynamics of O. rufa are mainly driven by bottom-up forces, primarily nest site availability.

  19. Evolutionary dynamics of the most populated genotype on rugged fitness landscapes

    Science.gov (United States)

    Jain, Kavita

    2007-09-01

    We consider an asexual population evolving on rugged fitness landscapes which are defined on the multidimensional genotypic space and have many local optima. We track the most populated genotype as it changes when the population jumps from a fitness peak to a better one during the process of adaptation. This is done using the dynamics of the shell model which is a simplified version of the quasispecies model for infinite populations and standard Wright-Fisher dynamics for large finite populations. We show that the population fraction of a genotype obtained within the quasispecies model and the shell model match for fit genotypes and at short times, but the dynamics of the two models are identical for questions related to the most populated genotype. We calculate exactly several properties of the jumps in infinite populations, some of which were obtained numerically in previous works. We also present our preliminary simulation results for finite populations. In particular, we measure the jump distribution in time and find that it decays as t-2 as in the quasispecies problem.

  20. Potential impact of harvesting on the population dynamics of two epiphytic bromeliads

    Science.gov (United States)

    Toledo-Aceves, Tarin; Hernández-Apolinar, Mariana; Valverde, Teresa

    2014-08-01

    Large numbers of epiphytes are extracted from cloud forests for ornamental use and illegal trade in Latin America. We examined the potential effects of different harvesting regimes on the population dynamics of the epiphytic bromeliads Tillandsia multicaulis and Tillandsia punctulata. The population dynamics of these species were studied over a 2-year period in a tropical montane cloud forest in Veracruz, Mexico. Prospective and retrospective analyses were used to identify which demographic processes and life-cycle stages make the largest relative contribution to variation in population growth rate (λ). The effect of simulated harvesting levels on population growth rates was analysed for both species. λ of both populations was highly influenced by survival (stasis), to a lesser extent by growth, and only slightly by fecundity. Vegetative growth played a central role in the population dynamics of these organisms. The λ value of the studied populations did not differ significantly from unity: T. multicaulis λ (95% confidence interval) = 0.982 (0.897-1.060) and T. punctulata λ = 0.967 (0.815-1.051), suggesting population stability. However, numerical simulation of different levels of extraction showed that λ would drop substantially even under very low (2%) harvesting levels. Matrix analysis revealed that T. multicaulis and T. punctulata populations are likely to decline and therefore commercial harvesting would be unsustainable. Based on these findings, management recommendations are outlined.

  1. Dynamics of climate-based malaria transmission model with age-structured human population

    Science.gov (United States)

    Addawe, Joel; Pajimola, Aprimelle Kris

    2016-10-01

    In this paper, we proposed to study the dynamics of malaria transmission with periodic birth rate of the vector and an age-structure for the human population. The human population is divided into two compartments: pre-school (0-5 years) and the rest of the human population. We showed the existence of a disease-free equilibrium point. Using published epidemiological parameters, we use numerical simulations to show potential effect of climate change in the dynamics of age-structured malaria transmission. Numerical simulations suggest that there exists an asymptotically attractive solution that is positive and periodic.

  2. Trypanosoma cruzi population dynamics in the Central Ecuadorian Coast.

    Science.gov (United States)

    Costales, Jaime A; Jara-Palacios, Miguel A; Llewellyn, Martin S; Messenger, Louisa A; Ocaña-Mayorga, Sofía; Villacís, Anita G; Tibayrenc, Michel; Grijalva, Mario J

    2015-11-01

    Chagas disease is the most important parasitic disease in Latin America. The causative agent, Trypanosoma cruzi, displays high genetic diversity and circulates in complex transmission cycles among domestic, peridomestic and sylvatic environments. In Ecuador, Rhodnius ecuadoriensis is known to be the major vector species implicated in T. cruzi transmission. However, across vast areas of Ecuador, little is known about T. cruzi genetic diversity in relation to different parasite transmission scenarios. Fifty-eight T. cruzi stocks from the central Ecuadorian coast, most of them derived from R. ecuadoriensis, were included in the study. All of them were genotyped as T. cruzi discrete typing unit I (DTU TcI). Analysis of 23 polymorphic microsatellite loci through neighbor joining and discriminant analysis of principal components yielded broadly congruent results and indicate genetic subdivision between sylvatic and peridomestic transmission cycles. However, both analyses also suggest that any barriers are imperfect and significant gene flow between parasite subpopulations in different habitats exists. Also consistent with moderate partition and residual gene flow between subpopulations, the fixation index (FST) was significant, but of low magnitude. Finally, the lack of private alleles in the domestic/peridomestic transmission cycle suggests the sylvatic strains constitute the ancestral population. The T. cruzi population in the central Ecuadorian coast shows moderate tendency to subdivision according to transmission cycle. However, connectivity between cycles exists and the sylvatic T. cruzi population harbored by R. ecuadoriensis vectors appears to constitute a source from which the parasite invades human domiciles and their surroundings in this region. We discuss the implications these findings have for the planning, implementation and evaluation of local Chagas disease control interventions.

  3. Postfire seedling dynamics and performance in Pinus halepensis Mill. populations

    Science.gov (United States)

    Daskalakou, Evangelia N.; Thanos, Costas A.

    2010-09-01

    Postfire dynamics of Aleppo pine seedling density, survival and growth were assessed in five burned forests of Attica, Greece (Stamata, Villia, Avlona, Kapandriti and Agios Stefanos) through the establishment of permanent experimental plots. All emerging seedlings were tagged and their survival and growth monitored at regular intervals. Seedling density dynamics show an initial, steep increase (to maximum values 2.9-4.6 seedlings m -2) followed by a gradual decrease that levels off at the second and third postfire year (1.3-3.0 seedlings m -2); similarly, postfire seedling survival more or less stabilised at 30-50%, 2-3 years after fire. On the basis of density and mortality trends as well as relevant bibliographic data, it is predicted that very dense, mature forests (10.000 trees ha -1 or more) will be reinstated within 15-20 years. During the first 5-7 postfire years, seedling/sapling annual height followed linear trends with various yearly rates, ranging mostly between 8 and 15 cm (and 27-30 cm in two exceptional, fast growing cases). Within an individual growth season, seedling height dynamics were found to follow sigmoid curves with growth increment peaks in mid-spring. The time (on a monthly basis) of seedling emergence did not affect seedling growth or survival. On the other hand, for the first time under natural conditions, it has been shown that cotyledon number per seedling, an indirect measure of both seed size and initial photosynthetic capacity, significantly affected seedling survival but not growth. Seedlings bearing a higher number of cotyledons, presumably derived from larger seeds, showed greater survival at the end of the first postfire year than seedlings with fewer cotyledons. A postfire selective pressure, favouring large seed size, is postulated to counteract with a contrasting one, which favours small seed size, expressed during fire-free conditions.

  4. Population dynamics of spotted owls in the Sierra Nevada, California

    Science.gov (United States)

    Blakesley, J.A.; Seamans, M.E.; Conner, M.M.; Franklin, A.B.; White, Gary C.; Gutierrez, R.J.; Hines, J.E.; Nichols, J.D.; Munton, T.E.; Shaw, D.W.H.; Keane, J.J.; Steger, G.N.; McDonald, T.L.

    2010-01-01

    The California spotted owl (Strix occidentalis occidentalis) is the only spotted owl subspecies not listed as threatened or endangered under the United States Endangered Species Act despite petitions to list it as threatened. We conducted a meta-analysis of population data for 4 populations in the southern Cascades and Sierra Nevada, California, USA, from 1990 to 2005 to assist a listing evaluation by the United States Fish and Wildlife Service. Our study areas (from N to S) were on the Lassen National Forest (LAS), Eldorado National Forest (ELD), Sierra National Forest (SIE), and Sequoia and Kings Canyon National Parks (SKC). These study areas represented a broad spectrum of habitat and management conditions in these mountain ranges. We estimated apparent survival probability, reproductive output, and rate of population change for spotted owls on individual study areas and for all study areas combined (meta-analysis) using model selection or model-averaging based on maximum-likelihood estimation. We followed a formal protocol to conduct this analysis that was similar to other spotted owl meta-analyses. Consistency of field and analytical methods among our studies reduced confounding methodological effects when evaluating results. We used 991 marked spotted owls in the analysis of apparent survival. Apparent survival probability was higher for adult than for subadult owls. There was little difference in apparent survival between male and female owls. Model-averaged mean estimates of apparent survival probability of adult owls varied from 0.811 ?? 0.021 for females at LAS to 0.890 ?? 0.016 for males at SKC. Apparent survival increased over time for owls of all age classes at LAS and SIE, for adults at ELD, and for second-year subadults and adults at SKC. The meta-analysis of apparent survival, which included only adult owls, confirmed an increasing trend in survival over time. Survival rates were higher for owls on SKC than on the other study areas. We analyzed data

  5. Constraints to commercialization of algal fuels.

    Science.gov (United States)

    Chisti, Yusuf

    2013-09-10

    Production of algal crude oil has been achieved in various pilot scale facilities, but whether algal fuels can be produced in sufficient quantity to meaningfully displace petroleum fuels, has been largely overlooked. Limitations to commercialization of algal fuels need to be understood and addressed for any future commercialization. This review identifies the major constraints to commercialization of transport fuels from microalgae. Algae derived fuels are expensive compared to petroleum derived fuels, but this could change. Unfortunately, improved economics of production are not sufficient for an environmentally sustainable production, or its large scale feasibility. A low-cost point supply of concentrated carbon dioxide colocated with the other essential resources is necessary for producing algal fuels. An insufficiency of concentrated carbon dioxide is actually a major impediment to any substantial production of algal fuels. Sustainability of production requires the development of an ability to almost fully recycle the phosphorous and nitrogen nutrients that are necessary for algae culture. Development of a nitrogen biofixation ability to support production of algal fuels ought to be an important long term objective. At sufficiently large scale, a limited supply of freshwater will pose a significant limitation to production even if marine algae are used. Processes for recovering energy from the algal biomass left after the extraction of oil, are required for achieving a net positive energy balance in the algal fuel oil. The near term outlook for widespread use of algal fuels appears bleak, but fuels for niche applications such as in aviation may be likely in the medium term. Genetic and metabolic engineering of microalgae to boost production of fuel oil and ease its recovery, are essential for commercialization of algal fuels. Algae will need to be genetically modified for improved photosynthetic efficiency in the long term.

  6. Population synthesis of planet formation using a torque formula with dynamic effects

    CERN Document Server

    Sasaki, Takanori

    2016-01-01

    Population synthesis studies into planet formation have suggested that distributions consistent with observations can only be reproduced if the actual Type I migration timescale is at least an order of magnitude longer than that deduced from linear theories. Although past studies considered the effect of the Type I migration of protoplanetary embryos, in most cases they used a conventional formula based on static torques in isothermal disks, and employed a reduction factor to account for uncertainty in the mechanism details. However, in addition to static torques, a migrating planet experiences dynamic torques that are proportional to the migration rate. These dynamic torques can impact on planet migration and predicted planetary populations. In this study, we derived a new torque formula for Type I migration by taking into account dynamic corrections. This formula was used to perform population synthesis simulations with and without the effect of dynamic torques. In many cases, inward migration was slowed si...

  7. Reproductive success is predicted by social dynamics and kinship in managed animal populations.

    Science.gov (United States)

    Newman, Saul J; Eyre, Simon; Kimble, Catherine H; Arcos-Burgos, Mauricio; Hogg, Carolyn; Easteal, Simon

    2016-01-01

    Kin and group interactions are important determinants of reproductive success in many species. Their optimization could, therefore, potentially improve the productivity and breeding success of managed populations used for agricultural and conservation purposes. Here we demonstrate this potential using a novel approach to measure and predict the effect of kin and group dynamics on reproductive output in a well-known species, the meerkat Suricata suricatta. Variation in social dynamics predicts 30% of the individual variation in reproductive success of this species in managed populations, and accurately forecasts reproductive output at least two years into the future. Optimization of social dynamics in captive meerkat populations doubles their projected reproductive output. These results demonstrate the utility of a quantitative approach to breeding programs informed by social and kinship dynamics. They suggest that this approach has great potential for improvements in the management of social endangered and agricultural species.

  8. Climate effects and feedback structure determining weed population dynamics in a long-term experiment.

    Science.gov (United States)

    Lima, Mauricio; Navarrete, Luis; González-Andujar, José Luis

    2012-01-01

    Pest control is one of the areas in which population dynamic theory has been successfully applied to solve practical problems. However, the links between population dynamic theory and model construction have been less emphasized in the management and control of weed populations. Most management models of weed population dynamics have emphasized the role of the endogenous process, but the role of exogenous variables such as climate have been ignored in the study of weed populations and their management. Here, we use long-term data (22 years) on two annual weed species from a locality in Central Spain to determine the importance of endogenous and exogenous processes (local and large-scale climate factors). Our modeling study determined two different feedback structures and climate effects in the two weed species analyzed. While Descurainia sophia exhibited a second-order feedback and low climate influence, Veronica hederifolia was characterized by a first-order feedback structure and important effects from temperature and rainfall. Our results strongly suggest the importance of theoretical population dynamics in understanding plant population systems. Moreover, the use of this approach, discerning between the effect of exogenous and endogenous factors, can be fundamental to applying weed management practices in agricultural systems and to controlling invasive weedy species. This is a radical change from most approaches currently used to guide weed and invasive weedy species managements.

  9. Climate Effects and Feedback Structure Determining Weed Population Dynamics in a Long-Term Experiment

    Science.gov (United States)

    Lima, Mauricio; Navarrete, Luis; González-Andujar, José Luis

    2012-01-01

    Pest control is one of the areas in which population dynamic theory has been successfully applied to solve practical problems. However, the links between population dynamic theory and model construction have been less emphasized in the management and control of weed populations. Most management models of weed population dynamics have emphasized the role of the endogenous process, but the role of exogenous variables such as climate have been ignored in the study of weed populations and their management. Here, we use long-term data (22 years) on two annual weed species from a locality in Central Spain to determine the importance of endogenous and exogenous processes (local and large-scale climate factors). Our modeling study determined two different feedback structures and climate effects in the two weed species analyzed. While Descurainia sophia exhibited a second-order feedback and low climate influence, Veronica hederifolia was characterized by a first-order feedback structure and important effects from temperature and rainfall. Our results strongly suggest the importance of theoretical population dynamics in understanding plant population systems. Moreover, the use of this approach, discerning between the effect of exogenous and endogenous factors, can be fundamental to applying weed management practices in agricultural systems and to controlling invasive weedy species. This is a radical change from most approaches currently used to guide weed and invasive weedy species managements. PMID:22272362

  10. Population-reaction model and microbial experimental ecosystems for understanding hierarchical dynamics of ecosystems.

    Science.gov (United States)

    Hosoda, Kazufumi; Tsuda, Soichiro; Kadowaki, Kohmei; Nakamura, Yutaka; Nakano, Tadashi; Ishii, Kojiro

    2016-02-01

    Understanding ecosystem dynamics is crucial as contemporary human societies face ecosystem degradation. One of the challenges that needs to be recognized is the complex hierarchical dynamics. Conventional dynamic models in ecology often represent only the population level and have yet to include the dynamics of the sub-organism level, which makes an ecosystem a complex adaptive system that shows characteristic behaviors such as resilience and regime shifts. The neglect of the sub-organism level in the conventional dynamic models would be because integrating multiple hierarchical levels makes the models unnecessarily complex unless supporting experimental data are present. Now that large amounts of molecular and ecological data are increasingly accessible in microbial experimental ecosystems, it is worthwhile to tackle the questions of their complex hierarchical dynamics. Here, we propose an approach that combines microbial experimental ecosystems and a hierarchical dynamic model named population-reaction model. We present a simple microbial experimental ecosystem as an example and show how the system can be analyzed by a population-reaction model. We also show that population-reaction models can be applied to various ecological concepts, such as predator-prey interactions, climate change, evolution, and stability of diversity. Our approach will reveal a path to the general understanding of various ecosystems and organisms.

  11. Role of seasonality on predator-prey-subsidy population dynamics.

    Science.gov (United States)

    Levy, Dorian; Harrington, Heather A; Van Gorder, Robert A

    2016-05-07

    The role of seasonality on predator-prey interactions in the presence of a resource subsidy is examined using a system of non-autonomous ordinary differential equations (ODEs). The problem is motivated by the Arctic, inhabited by the ecological system of arctic foxes (predator), lemmings (prey), and seal carrion (subsidy). We construct two nonlinear, nonautonomous systems of ODEs named the Primary Model, and the n-Patch Model. The Primary Model considers spatial factors implicitly, and the n-Patch Model considers space explicitly as a "Stepping Stone" system. We establish the boundedness of the dynamics, as well as the necessity of sufficiently nutritional food for the survival of the predator. We investigate the importance of including the resource subsidy explicitly in the model, and the importance of accounting for predator mortality during migration. We find a variety of non-equilibrium dynamics for both systems, obtaining both limit cycles and chaotic oscillations. We were then able to discuss relevant implications for biologically interesting predator-prey systems including subsidy under seasonal effects. Notably, we can observe the extinction or persistence of a species when the corresponding autonomous system might predict the opposite.

  12. Population dynamics of the pioneer population of Daphnia parvula, Fordyce during the invasion of Lake Candia (Northern Italy

    Directory of Open Access Journals (Sweden)

    Fiorenza MARGARITORA

    2004-02-01

    Full Text Available Since the 1970s Daphnia parvula, Fordyce, originally distributed in the New World, has been invading Europe. In Italy D. parvula first appeared in the shallow, eutrophic Lake Candia (Piedmont, Northern Italy during September 2002. Although several studies have documented D. parvula dispersal in European habitats, little is known about the life cycle and ecology of this invader in its new habitats. Invasion success depends on the ability of the invader population to perform well in the new ecosystem, which in turn results from the interaction between the characteristics of the invader and those of the invaded environment and its resident community. Early detection of D. parvula in the intensively studied Lake Candia offered an excellent opportunity to study the performance of the pioneer population and to document the early phases of invasion. Following the dynamics of the pioneer D. parvula population provided evidence of a high level of gamogenetic reproduction during most periods of population development. The production of males started at the onset of population growth prior to ephippia formation. The sex ratio ranged from 0.1 to 0.33 males per female with a maximum in October when males accounted for up to 24% of the total population density. The percentage of ephippia (free ephippia + ephippial females out of the total population density ranged from 3 to 23%. The large pool of resting eggs produced by the pioneer population of D. parvula in Lake Candia might reflect a strategy for increasing the probability of survival and establishment in the new environment.

  13. Reinforcement learning in complementarity game and population dynamics

    Science.gov (United States)

    Jost, Jürgen; Li, Wei

    2014-02-01

    We systematically test and compare different reinforcement learning schemes in a complementarity game [J. Jost and W. Li, Physica A 345, 245 (2005), 10.1016/j.physa.2004.07.005] played between members of two populations. More precisely, we study the Roth-Erev, Bush-Mosteller, and SoftMax reinforcement learning schemes. A modified version of Roth-Erev with a power exponent of 1.5, as opposed to 1 in the standard version, performs best. We also compare these reinforcement learning strategies with evolutionary schemes. This gives insight into aspects like the issue of quick adaptation as opposed to systematic exploration or the role of learning rates.

  14. Linking animal population dynamics to alterations in foraging behaviour

    DEFF Research Database (Denmark)

    Nabe-Nielsen, Jacob; Sibly, Richard; Tougaard, Jakob;

    was not jeopardized even when disturbances were simulated to have a relatively large and persistent effect on the behavior of individual animals. Porpoises were simulated to move away from noisy objects, preventing them from returning to the known food patches in that area. This resulted in decreasing energy reserves...... to disturbances by moving away are prevented from accessing the food in the disturbed areas and may also be prevented from dispersing among areas where food is available at different times of the year. Such disturbance effects may play a particularly large role for marine mammals that live in environments...... realistic movement patterns in scenarios where animals were not exposed to noise. Results/Conclusions The main results of the study were that the effects of disturbances were highly dependent on how fast the food recovered after being eaten, but that the long-term survival of the population...

  15. Population dynamics of the Kaminuriak caribou herd, 1968 - 1985

    Directory of Open Access Journals (Sweden)

    Douglas C. Heard

    1986-06-01

    Full Text Available The Kaminuraik caribou herd apparently declined from about 120 000 animals in 1950 to 63 000 in 1968. Beginning in 1968 documentation of herd trend was based on the estimate of the number of breeding (pregnant and post-partum females on the calving ground during the birth peak. It appeared as if we understood the basic population processes responsible for the decline when we correctly predicted a drop from 14 800 breeding females in 1977 to 13 000 in 1980. However a three-fold increase, to 41 000 breeding females in 1982, and continued growth thereafter, was unanticipated. Most of that increase must have resulted from an immigration of cows to the herd's traditional calving ground around Kaminuriak Lake, although increased birth rates, and increased survival rates also contributed to herd growth. Immigrant cows probably came from the northeastern mainland of the NWT

  16. Population Dynamics and Ecology of Arcobacter in Sewage

    Directory of Open Access Journals (Sweden)

    Jenny C Fisher

    2014-11-01

    Full Text Available 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 one to three 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 type strains for A. cryaerophilus group 1B (CCUG 17802 and group 1A (CCUG17801, 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 occupy unique niches in sewer infrastructure and 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

  17. Effects of infection on honey bee population dynamics: a model.

    Directory of Open Access Journals (Sweden)

    Matt I Betti

    Full Text Available 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.

  18. Spatially explicit modeling of habitat dynamics and fish population persistence in an intermittent lowland stream.

    Science.gov (United States)

    Perry, George L W; Bond, Nicholas R

    2009-04-01

    In temperate and arid climate zones many streams and rivers flow intermittently, seasonally contracting to a sequence of isolated pools or waterholes over the dry period, before reconnecting in the wetter parts of the year. This seasonal drying process is central to our understanding of the population dynamics of aquatic organisms such as fish and invertebrates in these systems. However, there is a dearth of empirical data on the temporal dynamics of such populations. We describe a spatially explicit individual-based model (SEIBM) of fish population dynamics in such systems, which we use to explore the long-term population viability of the carp gudgeon Hypseleotris spp. in a lowland stream in southeastern Australia. We explicitly consider the impacts of interannual variability in stream flow, for example, due to drought, on habitat availability and hence population persistence. Our results support observations that these populations are naturally highly variable, with simulated fish population sizes typically varying over four orders of magnitude within a 50-year simulation run. The most sensitive parameters in the model relate to the amount of water (habitat) in the system: annual rainfall, seepage loss from the pools, and the carrying capacity (number of individuals per cubic meter) of the pools as they dry down. It seems likely that temporal source sink dynamics allow the fish populations to persist in these systems, with good years (high rainfall and brief cease-to-flow [CTF] periods) buffering against periods of drought. In dry years during which the stream may contract to very low numbers of pools, each of these persistent pools becomes crucial for the persistence of the population in the system. Climate change projections for this area suggest decreases in rainfall and increased incidence of drought; under these environmental conditions the long-term persistence of these fish populations is uncertain.

  19. 'Wildlife 2001: Populations', an International Conference on Population Dynamics and Management of Vertebrates

    CERN Document Server

    Barrett, Reginald

    1992-01-01

    In 1984, a conference called Wildlife 2000: Modeling habitat relationships of terrestrial vertebrates, was held at Stanford Sierra Camp at Fallen Leaf Lake in the Sierra Nevada Mountains of California. The conference was well-received, and the published volume (Verner, J. , M. L. Morrison, and C. J. Ralph, editors. 1986. Wildlife 2000: modeling habitat relationships of terrestrial vertebrates, University of Wisconsin Press, Madison, Wisconsin, USA) proved to be a landmark publication that received a book award by The Wildlife Society. Wildlife 2001: populations was a followup conference with emphasis on the other major biological field of wildlife conservation and management, populations. It was held on July 29-31, 1991, at the Oakland Airport Hilton Hotel in Oakland, California, in accordance with our intent that this conference have a much stronger international representation than did Wildlife 2000. The goal of the conference was to bring together an international group of specialists to address the state ...

  20. Remote Sensing Marine Ecology: Wind-driven algal blooms in the open oceans and their ecological impacts

    Science.gov (United States)

    Tang, DanLing

    2016-07-01

    Algal bloom not only can increase the primary production but also could result in negative ecological consequence, e.g., Harmful Algal Blooms (HABs). According to the classic theory for the formation of algal blooms "critical depth" and "eutrophication", oligotrophic sea area is usually difficult to form a large area of algal blooms, and actually the traditional observation is only sporadic capture to the existence of algal blooms. Taking full advantage of multiple data of satellite remote sensing, this study: 1), introduces "Wind-driven algal blooms in open oceans: observation and mechanisms" It explained except classic coastal Ekman transport, the wind through a variety of mechanisms affecting the formation of algal blooms. Proposed a conceptual model of "Strong wind -upwelling-nutrient-phytoplankton blooms" in Western South China Sea (SCS) to assess role of wind-induced advection transport in phytoplankton bloom formation. It illustrates the nutrient resources that support long-term offshore phytoplankton blooms in the western SCS; 2), Proposal of the theory that "typhoons cause vertical mixing, induce phytoplankton blooms", and quantify their important contribution to marine primary production; Proposal a new ecological index for typhoon. Proposed remote sensing inversion models. 3), Finding of the spatial and temporaldistributions pattern of harmful algal bloom (HAB)and species variations of HAB in the South Yellow Sea and East China Sea, and in the Pearl River estuary, and their oceanic dynamic mechanisms related with monsoon; The project developed new techniques and generated new knowledge, which significantly improved understanding of the formation mechanisms of algal blooms. 1), It proposed "wind-pump" mechanism integrates theoretical system combing "ocean dynamics, development of algal blooms, and impact on primary production", which will benefit fisheries management. 2), A new interdisciplinary subject "Remote Sensing Marine Ecology"(RSME) has been

  1. Connecting Florida Bay algal blooms to freshwater nutrient sources

    Science.gov (United States)

    Blakey, T.; Melesse, A. M.

    2013-12-01

    factors influencing the nutrient circulation that is pertinent to observed patterns in Florida Bay algal blooms. These results point to the utility of regional hydrogeologic characterizations at fine spatial and temporal resolutions in tracking seasonally variable hydrologic inputs in complex and dynamic systems.

  2. Demographic characteristics of circumpolar caribou populations: ecotypes, ecological constraints, releases, and population dynamics

    OpenAIRE

    Mallory, F.F.; T.L. Hillis

    1998-01-01

    Data on the status of caribou {Rangifer tarandus) herds throughout the circumpolar region during the last 20 years were obtained from the literature and personal communication with researchers. Information was analysed in relation to ecotype (insular, montane, barren-ground, and woodland/forest), population status (increasing, stable, decreasing), herd size, human impact, and temporal change in number. The data support the conclusions (1) that each ecotype is exposed to different ecological c...

  3. Analysis of algal bloom risk with uncertainties in lakes by integrating self-organizing map and fuzzy information theory

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qiuwen, E-mail: qchen@rcees.ac.cn [RCEES, Chinese Academy of Sciences, Shuangqinglu 18, Beijing 10085 (China); China Three Gorges University, Daxuelu 8, Yichang 443002 (China); CEER, Nanjing Hydraulics Research Institute, Guangzhoulu 223, Nanjing 210029 (China); Rui, Han; Li, Weifeng; Zhang, Yanhui [RCEES, Chinese Academy of Sciences, Shuangqinglu 18, Beijing 10085 (China)

    2014-06-01

    Algal blooms are a serious problem in waters, which damage aquatic ecosystems and threaten drinking water safety. However, the outbreak mechanism of algal blooms is very complex with great uncertainty, especially for large water bodies where environmental conditions have obvious variation in both space and time. This study developed an innovative method which integrated a self-organizing map (SOM) and fuzzy information diffusion theory to comprehensively analyze algal bloom risks with uncertainties. The Lake Taihu was taken as study case and the long-term (2004–2010) on-site monitoring data were used. The results showed that algal blooms in Taihu Lake were classified into four categories and exhibited obvious spatial–temporal patterns. The lake was mainly characterized by moderate bloom but had high uncertainty, whereas severe blooms with low uncertainty were observed in the northwest part of the lake. The study gives insight on the spatial–temporal dynamics of algal blooms, and should help government and decision-makers outline policies and practices on bloom monitoring and prevention. The developed method provides a promising approach to estimate algal bloom risks under uncertainties. - Highlights: • An innovative method is developed to analyze algal bloom risks with uncertainties. • The algal blooms in Taihu Lake showed obvious spatial and temporal patterns. • The lake is mainly characterized as moderate bloom but with high uncertainty. • Severe bloom with low uncertainty appeared occasionally in the northwest part. • The results provide important information to bloom monitoring and management.

  4. Variation in foraging success among predators and its implications for population dynamics.

    Science.gov (United States)

    Okuyama, Toshinori

    2017-01-01

    The effects of the expected predation rate on population dynamics have been studied intensively, but little is known about the effects of predation rate variability (i.e., predator individuals having variable foraging success) on population dynamics. In this study, variation in foraging success among predators was quantified by observing the predation of the wolf spider Pardosa pseudoannulata on the cricket Gryllus bimaculatus in the laboratory. A population model was then developed, and the effect of foraging variability on predator-prey dynamics was examined by incorporating levels of variation comparable to those quantified in the experiment. The variability in the foraging success among spiders was greater than would be expected by chance (i.e., the random allocation of prey to predators). The foraging variation was density-dependent; it became higher as the predator density increased. A population model that incorporates foraging variation shows that the variation influences population dynamics by affecting the numerical response of predators. In particular, the variation induces negative density-dependent effects among predators and stabilizes predator-prey dynamics.

  5. Complex transient dynamics of stage-structured populations in response to environmental changes.

    Science.gov (United States)

    Massie, Thomas M; Ryabov, Alexei; Blasius, Bernd; Weithoff, Guntram; Gaedke, Ursula

    2013-07-01

    Stage structures of populations can have a profound influence on their dynamics. However, not much is known about the transient dynamics that follow a disturbance in such systems. Here we combined chemostat experiments with dynamical modeling to study the response of the phytoplankton species Chlorella vulgaris to press perturbations. From an initially stable steady state, we altered either the concentration or dilution rate of a growth-limiting resource. This disturbance induced a complex transient response-characterized by the possible onset of oscillations-before population numbers relaxed to a new steady state. Thus, cell numbers could initially change in the opposite direction of the long-term change. We present quantitative indexes to characterize the transients and to show that the dynamic response is dependent on the degree of synchronization among life stages, which itself depends on the state of the population before perturbation. That is, we show how identical future steady states can be approached via different transients depending on the initial population structure. Our experimental results are supported by a size-structured model that accounts for interplay between cell-cycle and population-level processes and that includes resource-dependent variability in cell size. Our results should be relevant to other populations with a stage structure including organisms of higher order.

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

    Science.gov (United States)

    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.

  7. The importance of temperature fluctuations in understanding mosquito population dynamics and malaria risk

    Science.gov (United States)

    Nelson, William A.; Paaijmans, Krijn P.; Thomas, Matthew B.; Bjørnstad, Ottar N.

    2017-01-01

    Temperature is a key environmental driver of Anopheles mosquito population dynamics; understanding its central role is important for these malaria vectors. Mosquito population responses to temperature fluctuations, though important across the life history, are poorly understood at a population level. We used stage-structured, temperature-dependent delay-differential equations to conduct a detailed exploration of the impacts of diurnal and annual temperature fluctuations on mosquito population dynamics. The model allows exploration of temperature-driven temporal changes in adult age structure, giving insights into the population’s capacity to vector malaria parasites. Because of temperature-dependent shifts in age structure, the abundance of potentially infectious mosquitoes varies temporally, and does not necessarily mirror the dynamics of the total adult population. In addition to conducting the first comprehensive theoretical exploration of fluctuating temperatures on mosquito population dynamics, we analysed observed temperatures at four locations in Africa covering a range of environmental conditions. We found both temperature and precipitation are needed to explain the observed malaria season in these locations, enhancing our understanding of the drivers of malaria seasonality and how temporal disease risk may shift in response to temperature changes. This approach, tracking both mosquito abundance and age structure, may be a powerful tool for understanding current and future malaria risk.

  8. The influence of synaptic weight distribution on neuronal population dynamics.

    Directory of Open Access Journals (Sweden)

    Ramakrishnan Iyer

    2013-10-01

    Full Text Available The manner in which different distributions of synaptic weights onto cortical neurons shape their spiking activity remains open. To characterize a homogeneous neuronal population, we use the master equation for generalized leaky integrate-and-fire neurons with shot-noise synapses. We develop fast semi-analytic numerical methods to solve this equation for either current or conductance synapses, with and without synaptic depression. We show that its solutions match simulations of equivalent neuronal networks better than those of the Fokker-Planck equation and we compute bounds on the network response to non-instantaneous synapses. We apply these methods to study different synaptic weight distributions in feed-forward networks. We characterize the synaptic amplitude distributions using a set of measures, called tail weight numbers, designed to quantify the preponderance of very strong synapses. Even if synaptic amplitude distributions are equated for both the total current and average synaptic weight, distributions with sparse but strong synapses produce higher responses for small inputs, leading to a larger operating range. Furthermore, despite their small number, such synapses enable the network to respond faster and with more stability in the face of external fluctuations.

  9. Modelling the dynamics of feral alfalfa populations and its management implications.

    Directory of Open Access Journals (Sweden)

    Muthukumar V Bagavathiannan

    Full Text Available BACKGROUND: Feral populations of cultivated crops can pose challenges to novel trait confinement within agricultural landscapes. Simulation models can be helpful in investigating the underlying dynamics of feral populations and determining suitable management options. METHODOLOGY/PRINCIPAL FINDINGS: We developed a stage-structured matrix population model for roadside feral alfalfa populations occurring in southern Manitoba, Canada. The model accounted for the existence of density-dependence and recruitment subsidy in feral populations. We used the model to investigate the long-term dynamics of feral alfalfa populations, and to evaluate the effectiveness of simulated management strategies such as herbicide application and mowing in controlling feral alfalfa. Results suggest that alfalfa populations occurring in roadside habitats can be persistent and less likely to go extinct under current roadverge management scenarios. Management attempts focused on controlling adult plants alone can be counterproductive due to the presence of density-dependent effects. Targeted herbicide application, which can achieve complete control of seedlings, rosettes and established plants, will be an effective strategy, but the seedbank population may contribute to new recruits. In regions where roadside mowing is regularly practiced, devising a timely mowing strategy (early- to mid-August for southern Manitoba, one that can totally prevent seed production, will be a feasible option for managing feral alfalfa populations. CONCLUSIONS/SIGNIFICANCE: Feral alfalfa populations can be persistent in roadside habitats. Timely mowing or regular targeted herbicide application will be effective in managing feral alfalfa populations and limit feral-population-mediated gene flow in alfalfa. However, in the context of novel trait confinement, the extent to which feral alfalfa populations need to be managed will be dictated by the tolerance levels established by specific production

  10. Abundance, biomass and composition of spring ice algal and phytoplankton communities of the Laptev Sea (Arctic)

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Abundance, biomass and composition of the ice algal and phytoplankton communities were investigated in the southeastern Laptev Sea in spring 1999.Diatoms dominated the algal communities and pennate diatoms dominated the diatom population. 12 dominant algal species occurred within sea ice and underlying water column, including Fragilariopsis oceanica, F. cylindrus, Nitzschia frigida , N. promare, Achnanthes taeniata , Nitzschia neofrigida , Navicula pelagica , N. vanhoef fenii, N. septentrionalis, Melosira arctica , Clindrotheca closterium and Pyramimonas sp. The algal abundance of bottom 10 cm sea ice varied between 14.6 and 1562.2 × 104 cells l-1 with an average of 639.0 × 104cells l-1 , and the algal biomass ranged from 7.89 to 2093.5 μg C l-1 with an average of 886.9 μg C l-1 , which were generally one order of magnitude higher than those of sub-bottom ice and two orders of magnitude higher than those of underlying surface water. The integrated algal abundance and biomass of lowermost 20 cm ice column were averagely 7.7 and 12.2 times as those of upper 20 m water column, respectively, suggesting that the ice algae might play an important role in maintaining the coastal marine ecosystem before the thawing of sea ice. Ice algae influenced the phytoplankton community of the underlying water column.However, the "seeding" of ice algae for phytoplankton bloom was negligible because of the low phytoplankton biomass within the underlying water column.

  11. Raman microspectroscopy based sensor of algal lipid unsaturation

    Science.gov (United States)

    Samek, Ota; Pilát, Zdeněk; Jonáš, Alexandr; Zemánek, Pavel; Šerý, Mojmír; Ježek, Jan; Bernatová, Silvie; Nedbal, Ladislav; Trtílek, Martin

    2011-05-01

    Raman spectroscopy is a powerful tool for chemical analysis. This technique can elucidate fundamental questions about the metabolic processes and intercellular variability on a single cell level. Therefore, Raman spectroscopy can significantly contribute to the study and use of microalgae in systems biology and biofuel technology. Raman spectroscopy can be combined with optical tweezers. We have employed microfluidic system to deliver the sampled microalgae to the Raman-tweezers. This instrument is able to measure chemical composition of cells and to track metabolic processes in vivo, in real-time and label-free making it possible to detect population variability in a wide array of traits. Moreover, employing an active sorting switch, cells can be separated depending on input parameters obtained from Raman spectra. We focus on algal lipids which are promising potential products for biofuel as well as for nutrition. Important parameter characterizing the algal lipids is the degree of unsaturation of the constituent fatty acids. We demonstrate the capacity of our Raman tweezers based sensor to sort cells according to the degree of unsaturation in lipid storage bodies of individual living algal cells.

  12. Sustainable Algal Energy Production and Environmental Remediation

    Energy Technology Data Exchange (ETDEWEB)

    Cooke, William E. [College of William and Mary, Williamsburg, VA (United States). Dept. of Physics

    2012-07-14

    Overall, our results confirm that wild algal species sequester a wide range of organic and metal contaminants and excess nutrients (PAHs, trace metals, and nutrients) from natural waters, and suggest parameters that could be useful in predicting uptake rates for algae growing on an algal floway or other algal growth systems in the environment or in industrial processes. The implication for various fuel production processes differ with the detailed unit operations involved, and these results will be of use in the developing of scaling experiments for various types of engineering process designs.

  13. Mesola red deer: physical characteristics, population dynamics and conservation perspectives

    Directory of Open Access Journals (Sweden)

    Stefano Mattioli

    2003-10-01

    Full Text Available Abstract The biometry, demography and genetics of red deer Cervus elaphus of Mesola Wood (NE Italy, are presented and discussed in relation to the conservation of this population. Modest body size, low stature, oversimplified antlers and a low reproductive performance characterise red deer from Mesola Wood. The mitochondrial genome showed a private haplotype, different from other red deer in Italy and central Europe. The uniqueness of this nucleus and its biogeographic importance make a long-term conservation plan particularly urgent. Management measures such as fallow deer reduction, winter feeding and pasture mowing were tested, giving promising results. The physical condition of the animals improved, calf and adult mortality declined, and a few cases of antlers with bez tine or crown were reported in this study after four decades. Riassunto Il Cervo della Mesola: caratteristiche fisiche, dinamica di popolazione e prospettive di conservazione La biometria, la demografia e la genetica del cervo Cervus elaphus del Gran Bosco della Mesola (Italia nord-orientale, vengono presentate e discusse in relazione alla salvaguardia di questa popolazione. Il cervo della Mesola risulta caratterizzato dalle modeste dimensioni corporee, dalla struttura semplificata dei palchi e da un basso rendimento riproduttivo. L'analisi del genoma mitocondriale ha evidenziato un aplotipo privato, diverso da quello degli altri cervi italiani e centroeuropei. L'unicità di questo nucleo e la sua importanza biogeografica rendono particolarmente urgente un piano di conservazione a lungo termine. Sono stati verificati interventi gestionali quali la riduzione numerica dei daini, il foraggiamento invernale e lo sfalcio delle superfici a pascolo, con risultati promettenti. Le condizioni fisiche degli animali sono migliorate, la mortalità tra i piccoli e gli adulti è diminuita, e sono stati registrati alcuni

  14. Population genetic structure and historical population dynamics of the South American sea lion, Otaria flavescens, in north-central Patagonia.

    Science.gov (United States)

    Túnez, Juan I; Cappozzo, Humberto L; Nardelli, Maximiliano; Cassini, Marcelo H

    2010-08-01

    The north-central Patagonian coast is the sea lions most abundant area in Argentina. As occurs along the entire Atlantic coast, the distribution of breeding colonies at this smaller geographical scale is also patchy, showing at least three areas with breeding activity. We study the genetic structure and historical population dynamics of the species in five colonies in this area, analysing a 508 base-pair segment of the D-loop control region. Otaria flavescens showed 10 haplotypes with 12 polymorphic sites. The genealogical relationship between haplotypes revealed a shallow pattern of phylogeographic structure. The analysis of molecular variance showed significant differences between colonies, however, pairwise comparisons only indicate significant differences between a pair of colonies belonging to different breeding areas. The pattern of haplotype differentiation and the mismatch distribution analysis suggest a possible bottleneck that would have occurred 64,000 years ago, followed by a demographic expansion of the three southernmost colonies. Thus, the historical population dynamics of O. flavescens in north-central Patagonia appears to be closely related with the dynamics of the Late Pleistocene glaciations.

  15. Exploring the Utilization of Complex Algal Communities to Address Algal Pond Crash and Increase Annual Biomass Production for Algal Biofuels

    Energy Technology Data Exchange (ETDEWEB)

    Hamilton, Cyd E. [Dept. of Energy (DOE), Washington DC (United States).

    2014-03-25

    This white paper briefly reviews the research literature exploring complex algal communities as a means of increasing algal biomass production via increased tolerance, resilience, and resistance to a variety of abiotic and biotic perturbations occurring within harvesting timescales. This paper identifies what data are available and whether more research utilizing complex communities is needed to explore the potential of complex algal community stability (CACS) approach as a plausible means to increase biomass yields regardless of ecological context and resulting in decreased algal-based fuel prices by reducing operations costs. By reviewing the literature for what we do and do not know, in terms of CACS methodologies, this report will provide guidance for future research addressing pond crash phenomena.

  16. Boom or bust? A comparative analysis of transient population dynamics in plants

    DEFF Research Database (Denmark)

    Stott, Iain; Franco, Miguel; Carslake, David

    2010-01-01

    researchers as further possible effectors of complicated dynamics. Previously published methods of transient analysis have tended to require knowledge of initial population structure. However, this has been overcome by the recent development of the parametric Kreiss bound (which describes how large...... a population must become before reaching its maximum possible transient amplification following a disturbance) and the extension of this and other transient indices to simultaneously describe both amplified and attenuated transient dynamics. We apply the Kreiss bound and other transient indices to a data base...... worrying artefact of basic model parameterization. Synthesis. Transient indices describe how big or how small plant populations can get, en route to long-term stable rates of increase or decline. The patterns we found in the potential for transient dynamics, across many species of plants, suggest...

  17. A framework for studying transient dynamics of population projection matrix models

    DEFF Research Database (Denmark)

    Stott, Iain; Townley, Stuart; Hodgson, David James

    2011-01-01

    arise even from simple models following ecological disturbances or perturbations. Recent interest in such transient dynamics has led to diverse methodologies for their quantification in density-independent, time-invariant population projection matrix (PPM) models, but the fragmented nature...... of this literature has stifled the widespread analysis of transients. We review the literature on transient analyses of linear PPM models and synthesise a coherent framework. We promote the use of standardised indices, and categorise indices according to their focus on either convergence times or transient...... population density, and on either transient bounds or case-specific transient dynamics. We use a large database of empirical PPM models to explore relationships between indices of transient dynamics. This analysis promotes the use of population inertia as a simple, versatile and informative predictor...

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

    Science.gov (United States)

    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. Improving Bayesian population dynamics inference: a coalescent-based model for multiple loci.

    Science.gov (United States)

    Gill, Mandev S; Lemey, Philippe; Faria, Nuno R; Rambaut, Andrew; Shapiro, Beth; Suchard, Marc A

    2013-03-01

    Effective population size is fundamental in population genetics and characterizes genetic diversity. To infer past population dynamics from molecular sequence data, coalescent-based models have been developed for Bayesian nonparametric estimation of effective population size over time. Among the most successful is a Gaussian Markov random field (GMRF) model for a single gene locus. Here, we present a generalization of the GMRF model that allows for the analysis of multilocus sequence data. Using simulated data, we demonstrate the improved performance of our method to recover true population trajectories and the time to the most recent common ancestor (TMRCA). We analyze a multilocus alignment of HIV-1 CRF02_AG gene sequences sampled from Cameroon. Our results are consistent with HIV prevalence data and uncover some aspects of the population history that go undetected in Bayesian parametric estimation. Finally, we recover an older and more reconcilable TMRCA for a classic ancient DNA data set.

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

    Science.gov (United States)

    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.

  1. Predation, Competition, and Abiotic Disturbance: Population Dynamics of Small Mammals

    Energy Technology Data Exchange (ETDEWEB)

    Yunger, John A.; /Northern Illinois U. /Northern Illinois U.

    1996-01-01

    Predation and food availability have been implicated in annual non-cyclic fluctuations of vertebrate prey at mid-latitudes. The timing and magnitude of these factors are unclear due to a lack of large-scale field experiments, little attention to interactions, and a failure to closely link vertebrate predators with their prey. From October 1992 to January 1996, small mammal populations were censused on eight 0.6 ha plots at monthly intervals in a 32-ha prairie restoration at Fermi National Accelerator Laboratory, Illinois. Terrestrial vertebrate predators were excluded after July 1993 from four of the eight plots and canid diets monitored. Both terrestrial and avian vertebrate predators were excluded in March 1994. During 1993 small mammal densities (i.e., Microtus Pennsylvanicus, Peromyscus leucopus, and P. maniculatus) were relatively high. Following peak densities in late summer, Microtus numbers wer 2-3x greater on exclusion plots relative to controls due to preferential selection of Microtus by canids, as reflected in dits. Following an ice-storm and crash in small mammal numbers (particularly Microtus), vertebrate predator exclusion had no detectable effect on P. leucopus numbers, probably due to an abundance of alternative prey (i.e., Sylvilagus floridanus). Meadow vole numbers began to increase in Fall 1995, and a numerical effect of predator exclusion, similar to that in 1993, was observed. Predator exclusion had no detectable effect on the movements and spatial patterns of Microtus during 1993. There was a significant decrease in home range and a significant increase in home range overlap for P. leucopus on the predator exclusion plots. The change in spatial behavior may be due to interspecific competition with Microtus resulting from increased densities on exclusion plots. Thus, predators had an indirect effect on P. leucopus spatial patterns mediated through M. Pennsylvanicus. The role of food limitation was studied using natural and manipulative

  2. An Algorithm for the Stochastic Simulation of Gene Expression and Heterogeneous Population Dynamics

    CERN Document Server

    Charlebois, Daniel A; Fraser, Dawn; Kaern, Mads

    2011-01-01

    We present an algorithm for the stochastic simulation of gene expression and heterogeneous population dynamics. The algorithm combines an exact method to simulate molecular-level fluctuations in single cells and a constant-number Monte Carlo method to simulate time-dependent statistical characteristics of growing cell populations. To benchmark performance, we compare simulation results with steadystate and time-dependent analytical solutions for several scenarios, including steadystate and time-dependent gene expression, and the effects on population heterogeneity of cell growth, division, and DNA replication. This comparison demonstrates that the algorithm provides an efficient and accurate approach to simulate how complex biological features influence gene expression. We also use the algorithm to model gene expression dynamics within "bet-hedging" cell populations during their adaption to environmental stress. These simulations indicate that the algorithm provides a framework suitable for simulating and ana...

  3. The demography of climate-driven and density-regulated population dynamics in a perennial plant

    DEFF Research Database (Denmark)

    Dahlgren, Johan; Bengstsson, Karin; Ehrlén, Johan

    2016-01-01

    Identifying the internal and external drivers of population dynamics is a key objective in ecology, currently accentuated by the need to forecast the effects of climate change on species distributions and abundances. The interplay between environmental and density effects is one particularly...... to be driven solely by the environment can overestimate extinction risks if there is density dependence. We conclude that density regulation can dampen effects of climate change on Fumana population size, and discuss the need to quantify density dependence in predictions of population responses...... important aspect of such forecasts. We examined the simultaneous impact of climate and intraspecific density on vital rates of the dwarf shrub Fumana procumbens over 20 yr, using generalized additive mixed models. We then analyzed effects on population dynamics using integral projection models...

  4. Population dynamics of the brown alga Himanthalia elongata under harvesting pressure

    Science.gov (United States)

    Stagnol, Doriane; Michel, Renaud; Davoult, Dominique

    2016-06-01

    Through experimental harvesting, followed by a 12-month monitoring of demographic attributes, we tested the influence of harvesting on the population dynamics of Himanthalia elongata. We further explore the data to test the hypothesis that the canopy would exert a negative effect on the other developmental stages (intraspecific competition) throughout the recovery cycle of the population. This showed that the H. elongata canopy plays a marked seasonal role not by precluding the presence of other developmental stages but by delaying or preventing their growth and development. The removal of the canopy facilitates the transition from one developmental stage to another, eventually permitting a fast recovery of size structure in the population. This study allows us to integrate population dynamics and intraspecific relationships in our understanding of macroalgal recovery patterns.

  5. Predicting extinction risks under climate change: coupling stochastic population models with dynamic bioclimatic habitat models.

    Science.gov (United States)

    Keith, David A; Akçakaya, H Resit; Thuiller, Wilfried; Midgley, Guy F; Pearson, Richard G; Phillips, Steven J; Regan, Helen M; Araújo, Miguel B; Rebelo, Tony G

    2008-10-23

    Species responses to climate change may be influenced by changes in available habitat, as well as population processes, species interactions and interactions between demographic and landscape dynamics. Current methods for assessing these responses fail to provide an integrated view of these influences because they deal with habitat change or population dynamics, but rarely both. In this study, we linked a time series of habitat suitability models with spatially explicit stochastic population models to explore factors that influence the viability of plant species populations under stable and changing climate scenarios in South African fynbos, a global biodiversity hot spot. Results indicate that complex interactions between life history, disturbance regime and distribution pattern mediate species extinction risks under climate change. Our novel mechanistic approach allows more complete and direct appraisal of future biotic responses than do static bioclimatic habitat modelling approaches, and will ultimately support development of more effective conservation strategies to mitigate biodiversity losses due to climate change.

  6. Temporal analysis of genetic structure to assess population dynamics of reintroduced swift foxes.

    Science.gov (United States)

    Cullingham, Catherine I; Moehrenschlager, Axel

    2013-12-01

    Reintroductions are increasingly used to reestablish species, but a paucity of long-term postrelease monitoring has limited understanding of whether and when viable populations subsequently persist. We conducted temporal genetic analyses of reintroduced populations of swift foxes (Vulpes velox) in Canada (Alberta and Saskatchewan) and the United States (Montana). We used samples collected 4 years apart, 17 years from the initiation of the reintroduction, and 3 years after the conclusion of releases. To assess program success, we genotyped 304 hair samples, subsampled from the known range in 2000 and 2001, and 2005 and 2006, at 7 microsatellite loci. We compared diversity, effective population size, and genetic connectivity over time in each population. Diversity remained stable over time and there was evidence of increasing effective population size. We determined population structure in both periods after correcting for differences in sample sizes. The geographic distribution of these populations roughly corresponded with the original release locations, which suggests the release sites had residual effects on the population structure. However, given that both reintroduction sites had similar source populations, habitat fragmentation, due to cropland, may be associated with the population structure we found. Although our results indicate growing, stable populations, future connectivity analyses are warranted to ensure both populations are not subject to negative small-population effects. Our results demonstrate the importance of multiple sampling years to fully capture population dynamics of reintroduced populations. Análisis Temporal de la Estructura Genética para Evaluar la Dinámica Poblacional de Zorros (Vulpes velox) Reintroducidos.

  7. Population Dynamics and the Optical Absorption in Hybrid Metal Nanoparticle - Semiconductor Quantum dot Nanosystem

    CERN Document Server

    Kim, Nam-Chol; Ko, Myong-Chol; So, Guang Hyok; Kim, Il-Guang

    2015-01-01

    We studied theoretically the population dynamics and the absorption spectrum of hybrid nanosystem consisted of a matal nanoparticle (MNP) and a semiconductor quantum dot(SQD). We investigated the exciton-plasmon coupling effects on the population dynamics and the absorption properties of the nanostructure. Our results show that the nonlinear optical response of the hybrid nanosystem can be greatly enhanced or depressed due to the exciton-plasmon couplings. The results obtained here may have the potential applications of nanoscale optical devices such as optical switches and quantum devices such as a single photon transistor.

  8. Metastable states and quasicycles in a stochastic Wilson-Cowan model of neuronal population dynamics

    KAUST Repository

    Bressloff, Paul C.

    2010-11-03

    We analyze a stochastic model of neuronal population dynamics with intrinsic noise. In the thermodynamic limit N→∞, where N determines the size of each population, the dynamics is described by deterministic Wilson-Cowan equations. On the other hand, for finite N the dynamics is described by a master equation that determines the probability of spiking activity within each population. We first consider a single excitatory population that exhibits bistability in the deterministic limit. The steady-state probability distribution of the stochastic network has maxima at points corresponding to the stable fixed points of the deterministic network; the relative weighting of the two maxima depends on the system size. For large but finite N, we calculate the exponentially small rate of noise-induced transitions between the resulting metastable states using a Wentzel-Kramers- Brillouin (WKB) approximation and matched asymptotic expansions. We then consider a two-population excitatory or inhibitory network that supports limit cycle oscillations. Using a diffusion approximation, we reduce the dynamics to a neural Langevin equation, and show how the intrinsic noise amplifies subthreshold oscillations (quasicycles). © 2010 The American Physical Society.

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

    Science.gov (United States)

    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.

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

    OpenAIRE

    Holdridge, Erica M.; Cuellar‐Gempeler, Catalina; terHorst, Casey P.

    2016-01-01

    Abstract 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 ...

  11. Birth, growth and death as structuring tools in bacterial population dynamics

    OpenAIRE

    Lavric, Vasile; Graham, David W.

    2010-01-01

    Abstract A new model is presented that describes microbial population dynamics that emerge from complex interactions among birth, growth and death as oriented, discrete events. Specifically, birth and death act as structuring operators for individual organisms within the population, which become synchronised as age clusters (called cell-generations that are structured in age-classes) that are born at the same time and die in concert; a pattern very consistent with recent experiment...

  12. Population dynamics of the brown alga Himanthalia elongata under harvesting pressure

    OpenAIRE

    2016-01-01

    International audience; Through experimental harvesting, followed by a 12-month monitoring of demographic attributes, we tested the influence of harvesting on the population dynamics of Himanthalia elongata. We further explore the data to test the hypothesis that the canopy would exert a negative effect on the other developmental stages (intraspecific competition) throughout the recovery cycle of the population. This showed that the H. elongata canopy plays a marked seasonal role not by precl...

  13. Modeling population dynamics of solitary bees in relation to habitat quality

    OpenAIRE

    Ulbrich, K.; Seidelmann, K.

    2001-01-01

    To understand associations between habitat, individual behaviour, and population development of solitary bees we developed an individual-based model. This model is based on field observations of Osmia rufa (L) (Apoideae: Megachilidae) and describes population dynamics of solitary bees. Model rules are focused on maternal investment, in particular on the female’s individual decisions about sex and size of progeny. In the present paper, we address the effect of habi...

  14. Evolutionary dynamics of finite populations in games with polymorphic fitness equilibria.

    Science.gov (United States)

    Ficici, Sevan G; Pollack, Jordan B

    2007-08-07

    The hawk-dove (HD) game, as defined by Maynard Smith [1982. Evolution and the Theory of Games. Cambridge University Press, Cambridge], allows for a polymorphic fitness equilibrium (PFE) to exist between its two pure strategies; this polymorphism is the attractor of the standard replicator dynamics [Taylor, P.D., Jonker, L., 1978. Evolutionarily stable strategies and game dynamics. Math. Biosci. 40, 145-156; Hofbauer, J., Sigmund, K., 1998. Evolutionary Games and Population Dynamics. Cambridge University Press, Cambridge] operating on an infinite population of pure-strategists. Here, we consider stochastic replicator dynamics, operating on a finite population of pure-strategists playing games similar to HD; in particular, we examine the transient behavior of the system, before it enters an absorbing state due to sampling error. Though stochastic replication prevents the population from fixing onto the PFE, selection always favors the under-represented strategy. Thus, we may naively expect that the mean population state (of the pre-absorption transient) will correspond to the PFE. The empirical results of Fogel et al. [1997. On the instability of evolutionary stable states. BioSystems 44, 135-152] show that the mean population state, in fact, deviates from the PFE with statistical significance. We provide theoretical results that explain their observations. We show that such deviation away from the PFE occurs when the selection pressures that surround the fitness-equilibrium point are asymmetric. Further, we analyze a Markov model to prove that a finite population will generate a distribution over population states that equilibrates selection-pressure asymmetry; the mean of this distribution is generally not the fitness-equilibrium state.

  15. Locally dispersing populations in heterogeneous dynamic landscapes with spatiotemporal correlations. I. Block disturbance.

    Science.gov (United States)

    Hiebeler, David E; Houle, Jennifer; Drummond, Frank; Bilodeau, Peter; Merckens, Jeffery

    2016-10-21

    Locally dispersing populations are generally favorably affected by increasing the scale of habitat heterogeneity because they can exploit contiguous patches of suitable habitat. Increasing the spatial scale of landscape disturbances (such as by applying a pesticide to control an unwanted species) drives down population density because of reasons including dispersal-limited recolonization and the resulting increase in temporal variability. Here, we examine how population density changes as the spatial scale of landscape disturbance increases: does it increase due to increases in spatial correlations in landscape habitat type, or does it decrease due to the various spatial and temporal effects of larger-scale disturbances? We use simulations, mean field approximations, pair approximations, landscape-improved pair approximations (LIPA), and block probabilities to investigate a model of a locally dispersing species on a dynamic landscape with spatiotemporally structured heterogeneous habitat. Pesticide is applied at a given spatial scale, leaving habitat unsuitable for some time before dissipating and allowing the habitat to revert to a suitable state. We found that increasing the spatial scale of disturbances (while keeping the overall disturbance rate fixed) can increase population density, but generally only when landscape turnover is slow relative to population dynamics and when the population is somewhat close to its extinction threshold. Applying control measures at larger spatial scales may allow them to be more effective with the same overall treatment rate. The optimal spatial strategy for applying disturbances depends on both habitat availability as well as the turnover rate of the control measure being used. For the large-scale habitat dynamics in our model, it is possible to analytically calculate spatial correlations in habitat types over arbitrary scales. However, including exact habitat correlations at the triplet scale but approximating population

  16. Catalysis of Protein Folding by Chaperones Accelerates Evolutionary Dynamics in Adapting Cell Populations

    OpenAIRE

    Murat Cetinbaş; Shakhnovich, Eugene I.

    2013-01-01

    Although molecular chaperones are essential components of protein homeostatic machinery, their mechanism of action and impact on adaptation and evolutionary dynamics remain controversial. Here we developed a physics-based ab initio multi-scale model of a living cell for population dynamics simulations to elucidate the effect of chaperones on adaptive evolution. The 6-loci genomes of model cells encode model proteins, whose folding and interactions in cellular milieu can be evaluated exactly f...

  17. Plankton communities and summertime declines in algal abundance associated with low dissolved oxygen in the Tualatin River, Oregon

    Science.gov (United States)

    Carpenter, Kurt D.; Rounds, Stewart A.

    2013-01-01

    Phytoplankton populations in the Tualatin River in northwestern Oregon are an important component of the dissolved oxygen (DO) budget of the river and are critical for maintaining DO levels in summer. During the low-flow summer period, sufficient nutrients and a long residence time typically combine with ample sunshine and warm water to fuel blooms of cryptophyte algae, diatoms, green and blue-green algae in the low-gradient, slow-moving reservoir reach of the lower river. Algae in the Tualatin River generally drift with the water rather than attach to the river bottom as a result of moderate water depths, slightly elevated turbidity caused by suspended colloidal material, and dominance of silty substrates. Growth of algae occurs as if on a “conveyor belt” of streamflow, a dynamic system that is continually refreshed with inflowing water. Transit through the system can take as long as 2 weeks during the summer low-flow period. Photosynthetic production of DO during algal blooms is important in offsetting oxygen consumption at the sediment-water interface caused by the decomposition of organic matter from primarily terrestrial sources, and the absence of photosynthesis can lead to low DO concentrations that can harm aquatic life. The periods with the lowest DO concentrations in recent years (since 2003) typically occur in August following a decline in algal abundance and activity, when DO concentrations often decrease to less than State standards for extended periods (nearly 80 days). Since 2003, algal populations have tended to be smaller and algal blooms have terminated earlier compared to conditions in the 1990s, leading to more frequent declines in DO to levels that do not meet State standards. This study was developed to document the current abundance and species composition of phytoplankton in the Tualatin River, identify the possible causes of the general decline in algae, and evaluate hypotheses to explain why algal blooms diminish in midsummer. Plankton

  18. Tracing the early development of harmful algal blooms with the aid of Lagrangian coherent structures

    CERN Document Server

    Olascoaga, M J; Brand, L E; Koçak, H

    2007-01-01

    Several theories have been proposed to explain the development of harmful algal blooms (HABs) produced by the toxic dinoflagellate \\emph{Karenia brevis} on the West Florida Shelf. However, because the early stages of HAB development are usually not detected, these theories have been so far very difficult to verify. In this paper we employ simulated \\emph{Lagrangian coherent structures} (LCSs) to trace the early location of a HAB in late 2004 before it was transported to an area where it could be detected by satellite imagery, and then we make use of a population dynamics model to infer the factors that may have led to its development. The LCSs, which are computed based on a surface flow description provided by an ocean circulation model, delineate past and future histories of boundaries of passively advected fluid domains. The population dynamics model determines nitrogen in two components, nutrients and phytoplankton, which are assumed to be passively advected by the simulated surface currents. Two nearshore...

  19. Recent Advances in Algal Genetic Tool Development

    Energy Technology Data Exchange (ETDEWEB)

    R. Dahlin, Lukas; T. Guarnieri, Michael

    2016-06-24

    The goal of achieving cost-effective biofuels and bioproducts derived from algal biomass will require improvements along the entire value chain, including identification of robust, high-productivity strains and development of advanced genetic tools. Though there have been modest advances in development of genetic systems for the model alga Chlamydomonas reinhardtii, progress in development of algal genetic tools, especially as applied to non-model algae, has generally lagged behind that of more commonly utilized laboratory and industrial microbes. This is in part due to the complex organellar structure of algae, including robust cell walls and intricate compartmentalization of target loci, as well as prevalent gene silencing mechanisms, which hinder facile utilization of conventional genetic engineering tools and methodologies. However, recent progress in global tool development has opened the door for implementation of strain-engineering strategies in industrially-relevant algal strains. Here, we review recent advances in algal genetic tool development and applications in eukaryotic microalgae.

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

    Science.gov (United States)

    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.

  1. Interaction between stocking density and settlement on population dynamics in suspended mussel culture

    Science.gov (United States)

    Cubillo, Alhambra M.; Fuentes-Santos, Isabel; Labarta, Uxío

    2015-01-01

    Population dynamics on mussels growing on suspended culture depend mainly on the balance of several processes: mortality and/or dislodgements from the ropes, recruitment and growth. The negative effect of overcrowding on mussel growth and survival has been widely studied. Other works have addressed the effect of population size on recruitment on bottom beds. This study aims to provide insight into the processes underlying population dynamics. To this purpose, we analyzed the effect of stocking density on mussel growth, survival and seed settlement, and the post-settlement interaction between adults and recruits in suspended culture. The temporal pattern of the variables involved in population dynamics was fitted by GAM models, which in contrast with parametric models does not assume any prior relationships between variables. Our results show that mussel growth and survival depend on a trade-off between competition for resources at high densities and the risk of great settlements in less crowded adult mussel populations. Intracohort competition increased with stocking density, while seed settlement, which increases the risk of mussel dislodgements and leads to intercohort competition, was higher at moderate stocking densities. Post-settlement competitive pressures were driven by total population density and size composition. Both intracohort competition in adults and asymmetric competition between adults and recruits increase with higher adult-recruit ratios. All these density-dependent processes should be considered in future management strategies and research experimental designs.

  2. Can ocean acidification affect population dynamics of the barnacle Semibalanus balanoides at its southern range edge?

    Science.gov (United States)

    Findlay, Helen S; Burrows, Michael T; Kendall, Michael A; Spicer, John I; Widdicombe, Stephen

    2010-10-01

    The global ocean and atmosphere are warming. There is increasing evidence suggesting that, in addition to other environmental factors, climate change is affecting species distributions and local population dynamics. Additionally, as a consequence of the growing levels of atmospheric carbon dioxide (CO2), the oceans are taking up increasing amounts of this CO2, causing ocean pH to decrease (ocean acidification). The relative impacts of ocean acidification on population dynamics have yet to be investigated, despite many studies indicating that there will be at least a sublethal impact on many marine organisms, particularly key calcifying organisms. Using empirical data, we forced a barnacle (Semibalanus balanoides) population model to investigate the relative influence of sea surface temperature (SST) and ocean acidification on a population nearing the southern limit of its geographic distribution. Hindcast models were compared to observational data from Cellar Beach (southwestern United Kingdom). Results indicate that a declining pH trend (-0.0017 unit/yr), indicative of ocean acidification over the past 50 years, does not cause an observable impact on the population abundance relative to changes caused by fluctuations in temperature. Below the critical temperature (here T(crit) = 13.1 degrees C), pH has a more significant affect on population dynamics at this southern range edge. However, above this value, SST has the overriding influence. At lower SST, a decrease in pH (according to the National Bureau of Standards, pHNBs) from 8.2 to 7.8 can significantly decrease the population abundance. The lethal impacts of ocean acidification observed in experiments on early life stages reduce cumulative survival by approximately 25%, which again will significantly alter the population level at this southern limit. Furthermore, forecast predictions from this model suggest that combined acidification and warming cause this local population to die out 10 years earlier than

  3. Structure and dynamics of natural populations of the endangered plant Euryodendron excelsum H. T. Chang

    Institute of Scientific and Technical Information of China (English)

    Shikang SHEN; Haiying MA; Yuehua WANG; Boyi WANG; Guozhu SHEN

    2009-01-01

    Euryodendron excelsum H. T. Chang is an endangered species of the family Theaceae endemic to China. It is listed as a second-class endangered plant for state protection in the Red Data Book of Plants in the People's Republic of China. The species is restricted to one remnant population with less than 200 individuals in the Bajia region of Yangchun County, Guangdong Province.This study was conducted to determine the status of the population, analyze the past population structure and forecast the future population dynamics of E. excelsum.The size structure and height structure of the population of E. excelsum were tabulated and analyzed. Based on these data, we estimated the values of the parameters such as survival curve, mortality curve and life expectancy.Population dynamics was predicted by a time-sequence model. The size distribution of the whole population generally fit a reverse "J" type curve, suggesting a stable population. The number of young individuals was larger than that of middle-aged and old individuals. The analysis of life table and survival curves show that under environmental screening and human disturbance, the population had one peak of mortality in size class Ⅱ and only 11.43% individuals could survive from size class Ⅱ to size class III. The life expectancy of E. excelsum was the highest in size class IV. The survival curve of the population belongs to the Deevey-III type. Time-sequence models for E. excelsum population predict that the number of different size classes will increase after two and five years. As a result, the crucial factors for the natural regeneration and restoration of E. excelsum are the protection of living individuals and their habitat.

  4. Direct conversion of algal biomass to biofuel

    Science.gov (United States)

    Deng, Shuguang; Patil, Prafulla D; Gude, Veera Gnaneswar

    2014-10-14

    A method and system for providing direct conversion of algal biomass. Optionally, the method and system can be used to directly convert dry algal biomass to biodiesels under microwave irradiation by combining the reaction and combining steps. Alternatively, wet algae can be directly processed and converted to fatty acid methyl esters, which have the major components of biodiesels, by reacting with methanol at predetermined pressure and temperature ranges.

  5. Dynamical behaviour of an epidemic on complex networks with population mobility

    Institute of Scientific and Technical Information of China (English)

    Zhang Hai-Feng; Small Michael; Fu Xin-Chu; Wang Bing-Hong

    2009-01-01

    In this paper,we study the dynamical behaviour of an epidemic on complex networks with population mobility.In our model,the number of people on each node is unrestricted as the nodes of the network are considered as cities,communities,and so on. Because people can travel between different cities,we study the effect of a population's mobility on the epidemic spreading. In view of the population's mobility,we suppose that the usceptible individual can be infected by an infected individual in the same city or other connected cities. Simulations are presented to verify our analysis.

  6. Algal and fungal diversity in Antarctic lichens.

    Science.gov (United States)

    Park, Chae Haeng; Kim, Kyung Mo; Elvebakk, Arve; Kim, Ok-Sun; Jeong, Gajin; Hong, Soon Gyu

    2015-01-01

    The composition of lichen ecosystems except mycobiont and photobiont has not been evaluated intensively. In addition, recent studies to identify algal genotypes have raised questions about the specific relationship between mycobiont and photobiont. In the current study, we analyzed algal and fungal community structures in lichen species from King George Island, Antarctica, by pyrosequencing of eukaryotic large subunit (LSU) and algal internal transcribed spacer (ITS) domains of the nuclear rRNA gene. The sequencing results of LSU and ITS regions indicated that each lichen thallus contained diverse algal species. The major algal operational taxonomic unit (OTU) defined at a 99% similarity cutoff of LSU sequences accounted for 78.7-100% of the total algal community in each sample. In several cases, the major OTUs defined by LSU sequences were represented by two closely related OTUs defined by 98% sequence similarity of ITS domain. The results of LSU sequences indicated that lichen-associated fungi belonged to the Arthoniomycetes, Eurotiomycetes, Lecanoromycetes, Leotiomycetes, and Sordariomycetes of the Ascomycota, and Tremellomycetes and Cystobasidiomycetes of the Basidiomycota. The composition of major photobiont species and lichen-associated fungal community were mostly related to the mycobiont species. The contribution of growth forms or substrates on composition of photobiont and lichen-associated fungi was not evident.

  7. Nonbreeding-Season Drivers of Population Dynamics in Seasonal Migrants: Conservation Parallels Across Taxa

    Directory of Open Access Journals (Sweden)

    Anna M. Calvert

    2009-12-01

    Full Text Available For seasonal migrants, logistical constraints have often limited conservation efforts to improving survival and reproduction during the breeding season only. Yet, mounting empirical evidence suggests that events occurring throughout the migratory life cycle can critically alter the demography of many migrant species. Herein, we build upon recent syntheses of avian migration research to review the role of non-breeding seasons in determining the population dynamics and fitness of diverse migratory taxa, including salmonid fishes, marine mammals, ungulates, sea turtles, butterflies, and numerous bird groups. We discuss several similarities across these varied migrants: (i non-breeding survivorship tends to be a strong driver of population growth; (ii non-breeding events can affect fitness in subsequent seasons through seasonal interactions at individual- and population-levels; (iii broad-scale climatic influences often alter non-breeding resources and migration timing, and may amplify population impacts through covariation among seasonal vital rates; and (iv changes to both stationary and migratory non-breeding habitats can have important consequences for abundance and population trends. Finally, we draw on these patterns to recommend that future conservation research for seasonal migrants will benefit from: (1 more explicit recognition of the important parallels among taxonomically diverse migratory animals; (2 an expanded research perspective focused on quantification of all seasonal vital rates and their interactions; and (3 the development of detailed population projection models that account for complexity and uncertainty in migrant population dynamics.

  8. Disentangling the effects of climate, density dependence, and harvest on an iconic large herbivore's population dynamics

    DEFF Research Database (Denmark)

    Koons, David; Colchero, Fernando; Hersey, Kent

    2015-01-01

    Understanding the relative effects of climate, harvest, and density dependence on population dynamics is critical for guiding sound population management, especially for ungulates in arid and semi-arid environments experiencing climate change. To address these issues for bison in southern Utah, we...... applied a Bayesian state-space model to a 72-year time series of abundance counts. While accounting for known harvest (as well as live removal) from the population, we found that the bison population in southern Utah exhibited strong potential to grow from low density (β0 = 0.26; Bayesian credible...... interval based on 95% of the highest posterior density: BCI = 0.19 to 0.33), and weak but statistically significant density dependence (β1 = -0.02, BCI = -0.04 to -0.004). Early spring temperatures also had strong positive effects on population growth (βfebaprtemp1 = 0.09, BCI = 0.04 to 0.14), much more so...

  9. Population dynamics of dominant demersal fishes caught in Tambelan Islands waters, Riau Archipelago Province

    Directory of Open Access Journals (Sweden)

    YONVITNER

    2012-10-01

    Full Text Available The population of demersal fishesal tend to be decline in the last few decades. The decline was due to the increased of intensive catches, fishing effort and illegal fishing practices. This study aimed to examine aspects of population dynamics such as mortality, recruitment, opportunity capture and population estimation. The study was conducted in six locations at Tambelan waters, on 4-16 November 2010. Collected data included the fish species, size and biomass catch. The analyses performed included mortality, recruitment, opportunity capture and population estimates (VPA. The data indicated that the Genus of Nemipterus and Lutjanus possess the highest total mortality rate that was respectively 1.62 and 2.55. The highest recruitment presentation of the population which has an annual period as Pentapodus was 16%. Catch opportunities tend to be higher than actual fishing, while the alleged biomass of steady state conditions reached 12.2 tons/yr.

  10. Monitoring methanogenic population dynamics in a full-scale anaerobic digester to facilitate operational management.

    Science.gov (United States)

    Williams, Julie; Williams, Haydn; Dinsdale, Richard; Guwy, Alan; Esteves, Sandra

    2013-07-01

    Microbial populations in a full-scale anaerobic digester fed on food waste were monitored over an 18-month period using qPCR. The digester exhibited a highly dynamic environment in which methanogenic populations changed constantly in response to availability of substrates and inhibitors. The methanogenic population in the digester was dominated by Methanosaetaceae, suggesting that aceticlastic methanogenesis was the main route for the production of methane. Sudden losses (69%) in Methanosaetaceae were followed by a build-up of VFAs which were subsequently consumed when populations recovered. A build up of ammonium inhibited Methanosaetaceae and resulted in shifts from acetate to hydrogen utilization. Addition of trace elements and alkalinity when propionate levels were high stimulated microbial growth. Routine monitoring of microbial populations and VFAs provided valuable insights into the complex processes occurring within the digester and could be used to predict digester stability and facilitate digester optimization.

  11. Sterol phylogenesis and algal evolution

    Energy Technology Data Exchange (ETDEWEB)

    Nes, W.D.; Norton, R.A.; Crumley, F.G. (Richard B. Russell Research Center, Athens, GA (USA)); Madigan, S.J.; Katz, E.R. (State Univ. of New York at Stony Brook (USA))

    1990-10-01

    The stereochemistry of several sterol precursors and end products synthesized by two fungal-like microorganisms Prototheca wickerhamii (I) and Dictyostelium discoideum (II) have been determined by chromatographic (TLC, GLC, and HPLC) and spectral (UV, MS, and {sup 1}H NMR) methods. From I and II the following sterols were isolated from the cells: cycloartenol, cyclolaudenol, 24(28)-methylenecy-cloartanol, ergosterol, protothecasterol, 4{alpha}-methylergostanol, 4{alpha}-methylclionastanol, clionastanol, 24{beta}-ethylcholesta-8,22-enol, and dictyosterol. In addition, the mechanism of C-24 methylation was investigated in both organisms by feeding to I (2-{sup 3}H)lanosterol, (2-{sup 3}H)cycloartenol, (24{sup 3}H)lanosterol, and (methyl-{sup 2}H{sub 3})methionine and by feeding to II (methyl-{sup 2}H{sub 3})methionine. The results demonstrate that the 24{beta} configuration is formed by different alkylation routes in I and II. The authors conclude that Prototheca is an apoplastic Chlorella (i.e., an alga) and that Dictyostelium as well as the other soil amoebae that synthesize cycloartenol evolved from algal rather than fungal ancestors.

  12. Towards developing algal synthetic biology.

    Science.gov (United States)

    Scaife, Mark Aden; Smith, Alison Gail

    2016-06-15

    The genetic, physiological and metabolic diversity of microalgae has driven fundamental research into photosynthesis, flagella structure and function, and eukaryotic evolution. Within the last 10 years these organisms have also been investigated as potential biotechnology platforms, for example to produce high value compounds such as long chain polyunsaturated fatty acids, pigments and antioxidants, and for biodiesel precursors, in particular triacylglycerols (TAGs). Transformation protocols, molecular tools and genome sequences are available for a number of model species including the green alga Chlamydomonas reinhardtii and the diatom Phaeodactylum tricornutum, although for both species there are bottlenecks to be overcome to allow rapid and predictable genetic manipulation. One approach to do this would be to apply the principles of synthetic biology to microalgae, namely the cycle of Design-Build-Test, which requires more robust, predictable and high throughput methods. In this mini-review we highlight recent progress in the areas of improving transgene expression, genome editing, identification and design of standard genetic elements (parts), and the use of microfluidics to increase throughput. We suggest that combining these approaches will provide the means to establish algal synthetic biology, and that application of standard parts and workflows will avoid parallel development and capitalize on lessons learned from other systems.

  13. Marine harmful algal blooms, human health and wellbeing

    DEFF Research Database (Denmark)

    Berdalet, Elisa; Fleming, Lora E.; Gowen, Richard

    2016-01-01

    Microalgal blooms are a natural part of the seasonal cycle of photosynthetic organisms in marine ecosystems. They are key components of the structure and dynamics of the oceans and thus sustain the benefits that humans obtain from these aquatic environments. However, some microalgal blooms can...... cause harm to humans and other organisms. These harmful algal blooms (HABs) have direct impacts on human health and negative influences on human wellbeing, mainly through their consequences to coastal ecosystem services (fisheries, tourism and recreation) and other marine organisms and environments...

  14. Population dynamics of thrips prey and their mite predators in a refuge

    NARCIS (Netherlands)

    Magalhães, S.; Van Rijn, P.C.J.; Montserrat, M.; Pallini, A.; Sabelis, M.W.

    2007-01-01

    Prey refuges are expected to affect population dynamics, but direct experimental tests of this hypothesis are scarce. Larvae of western flower thrips Frankliniella occidentalis use the web produced by spider mites as a refuge from predation by the predatory mite Neoseiulus cucumeris. Thrips incur a

  15. Influence of plant species on population dynamics, genotypic diversity and antibiotic production by indigenous Pseudomonas spp

    NARCIS (Netherlands)

    Bergsma-Vlami, M.; Prins, M.E.; Raaijmakers, J.M.

    2005-01-01

    The population dynamics, genotypic diversity and activity of naturally-occurring 2,4-diacetylphloroglucinol (DAPG)-producing Pseudomonas spp. was investigated for four plant species (wheat, sugar beet, potato, lily) grown in two different soils. All four plant species tested, except lily and in some

  16. Population dynamics of Ascaridia galli following single infection in young chickens

    DEFF Research Database (Denmark)

    Ferdushy, Tania; Luna Olivares, Luz Adilia; Nejsum, Peter;

    2013-01-01

    SUMMARY The population dynamics of Ascaridia galli was studied in 70 ISA Brown layer pullets, 42 of them were each experimentally infected with 500 embryonated A. galli eggs and 28 chickens were kept as uninfected controls. Six chickens from the infected group and 4 from the control group were ne...

  17. Nonlinear dynamic analysis of voice: A normative study in the Indian population

    Directory of Open Access Journals (Sweden)

    Jacqueline B. Fernandes, Radish Kumar Balasubramanium, Arivudai Nambi Pitchaimuthu, Jayashree S. Bhat

    2014-03-01

    Full Text Available Background: The aim of this study was to establish normative data for the Indian population using Nonlinear dynamic analysis. In this study, correlation dimension, a measure of nonlinear dynamic analysis was performed for normophonic young, middle aged and elderly voices. Materials and Methods: For this purpose, normophonic young, middle aged and elderly individuals were selected without a history of voice/respiratory problems and vocal abuse/ misuse. 60 participants were selected in each group. All of these individuals had a normal voice as evaluated through GRBAS scale. Sound Recorder, on a computer desktop was used for voice recording and “convert” code in MATLAB as well as D2.ini.writer software based on TISEAN package (Hegger, Kantz & Schreiber, 1999 was used for the calculation of Correlation dimension (D2. Correlation dimension measures were obtained for each participant, for both steady vowel phonations (/a/, /i/, /u/ as well as narration samples. Results: The correlation dimension measures across the group revealed a significant main effect of the groups indicating correlation dimension increases with increase in age. Conclusions: The application of nonlinear dynamic measures in the assessment of voice is a novel venture and thus this study provides normative data for correlation dimensions in the Indian population for future comparisons against the disordered voice samples. Further studies are warranted to investigate the same in the clinical population. Also other nonlinear dynamic analysis methods need to be investigated to obtain the normative data in the Indian population.

  18. Horn fly population dynamics as prediction tool for the fixation of pesticide resistance

    Science.gov (United States)

    This research project was conducted to establish the population dynamics of the horn fly. Two cattle herds were monitored to establish if contrasting climatic regional conditions, in addition to temperature and precipitation, related to the number of rainy days as a factor influencing horn fly infes...

  19. Field weed population dynamics : a review of model approaches and applications

    NARCIS (Netherlands)

    Holst, N.; Rasmussen, I.A.; Bastiaans, L.

    2007-01-01

    Mathematical modelling is a commonly used tool for studying the long-term dynamics of weed populations in agriculture. This was reflected in our review by the large number of scientific papers (134 original publications) and the continuing need to gain an overview over this fast developing field (20

  20. Numerical simulation of the one-dimensional population dynamics with nonlocal competitive losses and convection

    Science.gov (United States)

    Aleutdinova, V. A.; Borisov, A. V.; Shaparev, V. É.; Shapovalov, A. V.

    2011-09-01

    Numerical solutions of the generalized one-dimensional Fisher-Kolmogorov-Petrovskii-Piskunov equation with nonlocal competitive losses and convection are constructed. The influence function for nonlocal losses is chosen in the form of a Gaussian distribution. The effect of convection on the dynamics of the spatially inhomogeneous distribution of the population density is investigated.

  1. Population dynamics of european ground squirrels (Spermophilus citellus) in a suburban area

    NARCIS (Netherlands)

    Hoffmann, IE; Millesi, E; Everts, LG; Dittami, JP

    2003-01-01

    We monitored European ground squirrels (Spermophilus citellus) in a recreation area near Vienna, Austria, over a 7-year period to follow their population dynamics. Data were obtained by mark-recapture and daily checklists in an attempt to track the fates of individuals present in a defined area. Abu

  2. Cost-effectiveness of screening programs for Chlamydia trachomatis - A population-based dynamic approach

    NARCIS (Netherlands)

    Welte, R; Kretzschmar, M; Leidl, R; Van den Hoek, A; Jager, JC; Postma, MJ

    2000-01-01

    Background: Models commonly used for the economic assessment of chamydial screening programs do not consider population effects. Goal: To develop a novel dynamic approach for the economic evaluation of chlamydial prevention measures and to determine the cost-effectiveness of a general practitioner-b

  3. Application of homotopy-perturbation method to nonlinear population dynamics models

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, M.S.H. [School of Mathematical Sciences, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor (Malaysia); Hashim, I. [School of Mathematical Sciences, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor (Malaysia)], E-mail: ishak_h@ukm.my; Abdulaziz, O. [School of Mathematical Sciences, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor (Malaysia)

    2007-08-20

    In this Letter, the homotopy-perturbation method (HPM) is employed to derive approximate series solutions of nonlinear population dynamics models. The nonlinear models considered are the multispecies Lotka-Volterra equations. The accuracy of this method is examined by comparison with the available exact and the fourth-order Runge-Kutta method (RK4)

  4. Evolutionarily stable disequilibrium: endless dynamics of evolution in a stationary population

    NARCIS (Netherlands)

    Takeuchi, Nobuto; Kaneko, Kunihiko; Hogeweg, P

    2016-01-01

    Evolution is often conceived as changes in the properties of a population over generations. Does this notion exhaust the possible dynamics of evolution? Life is hierarchically organized, and evolution can operate at multiple levels with conflicting tendencies. Using a minimal model of such conflicti

  5. What controls the population dynamics of the invasive thistle Carduus nutans in its native range?

    NARCIS (Netherlands)

    Jongejans, E.; Sheppard, A.W.; Shea, K.

    2006-01-01

    1. The invasive thistle Carduus nutans causes major economic losses in the Americas, Australia and New Zealand. For the first time, we have modelled its population dynamics in its native range, Eurasia, where it rarely reaches problematic densities, in order to identify ways to improve management st

  6. Population dynamic of the swallowtail butterfly, Papilio polytes (Lepidoptera: Papilionidae in dry and wet seasons

    Directory of Open Access Journals (Sweden)

    SUWARNO

    2010-01-01

    Full Text Available Suwarno (2010 Population dynamic of the swallowtail butterfly, Papilio polytes (Lepidoptera: Papilionidae in dry and wet seasons. Biodiversitas 11: 19-23. The population dynamic of Papilio polytes L. (Lepidoptera: Papilionidae in dry and wet seasons was investigated in the citrus orchard in Tasek Gelugor, Pulau Pinang, Malaysia. Population of immature stages of P. polytes was observed alternate day from January to March 2006 (dry season, DS, from April to July 2006 (secondary wet season, SWS, and from October to December 2006 (primary wet season, PWS. The population dynamics of the immature stages of P. polytes varied between seasons. The immature stages of P. polytes are more abundance and significantly different in the PWS than those of the DS and the SWS. The larval densities in all seasons decreased with progressive development of the instar stages. Predators and parasitoids are the main factor in regulating the population abundance of immature stages of P. polytes. There were positive correlations between the abundance of immature stages of P. polytes and their natural enemies abundance in each season. Ooencyrtus papilioni Ashmead (Hymenoptera: Encyrtidae is the most egg parasitoid. Oxyopes quadrifasciatus L. Koch. and O. elegans L. Koch. (Araneae: Oxyopidae are the main predators in the young larvae, meanwhile Sycanus dichotomus Stal. (Heteroptera: Reduviidae, Calotes versicolor Fitzinger (Squamata: Agamidae, birds and praying mantis attacked the older larvae.

  7. Predator-Prey-Subsidy Population Dynamics on Stepping-Stone Domains.

    Science.gov (United States)

    Shen, Lulan; Van Gorder, Robert A

    2017-03-16

    Predator-prey-subsidy dynamics on stepping-stone domains are examined using a variety of network configurations. Our problem is motivated by the interactions between arctic foxes (predator) and lemmings (prey) in the presence of seal carrion (subsidy) provided by polar bears. We use the n-Patch Model, which considers space explicitly as a "Stepping Stone" system. We consider the role that the carrying capacity, predator migration rate, input subsidy rate, predator mortality rate, and proportion of predators surviving migration play in the predator-prey-subsidy population dynamics. We find that for certain types of networks, added mobility will help predator populations, allowing them to survive or coexist when they would otherwise go extinct if confined to one location, while in other situations (such as when sparsely distributed nodes in the network have few resources available) the added mobility will hurt the predator population. We also find that a combination of favorable conditions for the prey and subsidy can lead to the formation of limit cycles (boom and bust dynamic) from stable equilibrium states. These modifications to the dynamics vary depending on the specific network structure employed, highlighting the fact that network structure can strongly influence the predator-prey-subsidy dynamics in stepping-stone domains.

  8. Assessing the status and trend of bat populations across broad geographic regions with dynamic distribution models

    Science.gov (United States)

    Rodhouse, Thomas J.; Ormsbee, Patricia C.; Irvine, Kathryn M.; Vierling, Lee A.; Szewczak, Joseph M.; Vierling, Kerri T.

    2012-01-01

    Bats face unprecedented threats from habitat loss, climate change, disease, and wind power development, and populations of many species are in decline. A better ability to quantify bat population status and trend is urgently needed in order to develop effective conservation strategies. We used a Bayesian autoregressive approach to develop dynamic distribution models for Myotis lucifugus, the little brown bat, across a large portion of northwestern USA, using a four-year detection history matrix obtained from a regional monitoring program. This widespread and abundant species has experienced precipitous local population declines in northeastern USA resulting from the novel disease white-nose syndrome, and is facing likely range-wide declines. Our models were temporally dynamic and accounted for imperfect detection. Drawing on species–energy theory, we included measures of net primary productivity (NPP) and forest cover in models, predicting that M. lucifugus occurrence probabilities would covary positively along those gradients.

  9. Population and reproductive dynamics of the polychaete Pygospio elegans in a boreal estuary complex

    DEFF Research Database (Denmark)

    Thonig, Anne; Knott, K Emily; Kesäniemi, Jenni E

    2016-01-01

    Pygospio elegans is an opportunistic, wide-spread spionid polychaete that reproduces asexually via fragmentation and can produce benthic and pelagic larvae, hence combining different developmental modes in one species. We documented the density, size distribution, and reproductive activity of P....... elegans at four sites in the Danish Isefjord-Roskilde Fjord estuary complex, where all modes of reproduction were reported. We compared population dynamics of this species to environmental parameters such as salinity, temperature, and sediment characteristics (grain size, sorting, porosity, water content...... reproductive peaks at three sites. At those sites, we also observed a switch in larval developmental mode. Asexual reproduction peaked in April. While the seasonal dynamics can be related to temperature to a large extent, the differences in population dynamics among sites also correlated with sediment...

  10. Population dynamics in a Floquet realization of the Harper-Hofstadter Hamiltonian

    Science.gov (United States)

    Bilitewski, Thomas; Cooper, Nigel R.

    2015-06-01

    We study a Floquet realization of the Harper-Hofstadter model that has recently been implemented in a gas of cold bosonic atoms. We study in detail the scattering processes in this system in the weakly interacting regime due to the interplay of particle interactions and the explicit time dependence of the Floquet states that lead to band transitions and heating. We focus on the experimentally used parameters and explicitly model the transverse confining direction. Based on transition rates computed within the Floquet-Fermi golden rule we obtain band population dynamics which are in agreement with the dynamics observed in experiment. Finally, we discuss whether and how photon-assisted collisions that may be the source of heating and band population dynamics might be suppressed in the experimental setup by appropriate design of the transverse confining potential. The suppression of such processes will become increasingly important as experiments progress into simulating strongly interacting systems in the presence of artificial gauge fields.

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

    Science.gov (United States)

    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.

  12. Climate variability, human wildlife conflict and population dynamics of lions Panthera leo

    Science.gov (United States)

    Trinkel, Martina

    2013-04-01

    Large carnivores are threatened by habitat loss, declining prey populations and direct persecution. Pride dynamics of eight lion prides in the centre of the Etosha National Park, Namibia are described during a 16-year study. Since the beginning of the 1980s, the number of adult and subadult lions declined continuously to two third of its initial population size, and reached a new equilibrium in the 1990s. Pride sizes decreased from 6.3 adult females in 1989 to 2.8 lionesses in 1997. While the number of adult females declined continuously, the number of adult males, subadult females and subadult males remained constant over the years. A severe drought period, lasting for more than 20 years, led to declining prey populations inside the lions' territory. Besides declining prey populations, conflict with humans at the border of Etosha puts substantial pressure onto the lion population: 82 % of all known lion mortalities were caused by humans, and most of these consisted of adult females (28 %) and subadult males (29 %). I postulate that the considerable decline in the lion population is a response to declining prey populations, and although the human predator conflict is severe, it does not seem to limit the size of Etosha's lion population.

  13. Population Dynamics Following the Last Glacial Maximum in Two Sympatric Lizards in Northern China

    Institute of Scientific and Technical Information of China (English)

    Yanfu QU; Qun ZHAO; Hongliang LU; Xiang JI

    2014-01-01

    Phylogeographic studies ofEremias lizards (Lacertidae) in East Asia have been limited, and the impact of major climatic events on their population dynamics remains poorly known. This study aimed to investigate population histories and refugia during the Last Glacial Maximum of two sympatricEremias lizards (E. argus andE. brenchleyi) inhabiting northern China. We sequenced partial mitochondrial DNA from theND4 gene for 128 individuals ofE. argus from nine localities, and 46 individuals ofE. brenchleyi from ifve localities. Forty-fourND4 haplotypes were determined fromE. argus samples, and 33 fromE. brenchleyi samples. Population expansion events began about 0.0044 Ma inE. argus, and 0.031 Ma inE. brenchleyi. The demographic history ofE. brenchleyi indicates a long-lasting population decline since the most recent common ancestor, while that ofE. argusindicates a continuous population growth. Among-population structure was signiifcant in both species, and there were multiple refugia across their range. Intermittent gene flow occurred among expanded populations across multiple refugia during warmer phases of the glacial period, and this may explain why the effective population size has remained relatively stable inE. brenchleyi and grown inE. argus.

  14. Algal Energy Conversion and Capture

    Science.gov (United States)

    Hazendonk, P.

    2015-12-01

    We address the potential for energy conversions and capture for: energy generation; reduction in energy use; reduction in greenhouse gas emissions; remediation of water and air pollution; protection and enhancement of soil fertility. These processes have the potential to sequester carbon at scales that may have global impact. Energy conversion and capture strategies evaluate energy use and production from agriculture, urban areas and industries, and apply existing and emerging technologies to reduce and recapture energy embedded in waste products. The basis of biocrude production from Micro-algal feedstocks: 1) The nutrients from the liquid fraction of waste streams are concentrated and fed into photo bioreactors (essentially large vessels in which microalgae are grown) along with CO2 from flue gasses from down stream processes. 2) The algae are processed to remove high value products such as proteins and beta-carotenes. The advantage of algae feedstocks is the high biomass productivity is 30-50 times that of land based crops and the remaining biomass contains minimal components that are difficult to convert to biocrude. 3) The remaining biomass undergoes hydrothermal liquefaction to produces biocrude and biochar. The flue gasses of this process can be used to produce electricity (fuel cell) and subsequently fed back into the photobioreactor. The thermal energy required for this process is small, hence readily obtained from solar-thermal sources, and furthermore no drying or preprocessing is required keeping the energy overhead extremely small. 4) The biocrude can be upgraded and refined as conventional crude oil, creating a range of liquid fuels. In principle this process can be applied on the farm scale to the municipal scale. Overall, our primary food production is too dependent on fossil fuels. Energy conversion and capture can make food production sustainable.

  15. Algal Accessory Pigment Detection Using AVIRIS Image-Derived Spectral Radiance Data

    Science.gov (United States)

    Richardson, Laurie L.; Ambrosia, Vincent G.

    1996-01-01

    Visual and derivative analyses of AVIRIS spectral data can be used to detect algal accessory pigments in aquatic communities. This capability extends the use of remote sensing for the study of aquatic ecosystems by allowing detection of taxonomically significant pigment signatures which yield information about the type of algae present. Such information allows remote sensing-based assessment of aquatic ecosystem health, as in the detection of nuisance blooms of cyanobacteria or toxic blooms of dinoflagellates. Remote sensing of aquatic systems has traditionally focused on quantification of chlorophyll a, a photoreactive (and light-harvesting) pigment which is common to all algae as well as cyanobacteria (bluegreen algae). Due to the ubiquitousness of this pigment within algae, chl a is routinely measured to estimate algal biomass both during ground-truthing and using various airborne or satellite based sensors, including AVIRIS. Within the remote sensing and aquatic sciences communities, ongoing research has been performed to detect algal accessory pigments for assessment of algal population composition. This research is based on the fact that many algal accessory pigments are taxonomically significant, and all are spectrally unique. Aquatic scientists have been refining pigment analysis techniques, primarily high performance liquid chromatography, or HPLC, to detect specific pigments as a time-saving alternative to individual algal cell identifications and counts. Remote sensing scientists are investigating the use of pigment signatures to construct pigment libraries analogous to mineral spectral libraries used in geological remote sensing applications. The accessory pigment approach has been used successfully in remote sensing using data from the Thematic Mapper, low-altitude, multiple channel scanners, field spectroradiometers and the AVIRIS hyperspectral scanner. Due to spectral and spatial resolution capabilities, AVIRIS is the sensor of choice for such

  16. Population physiology: leveraging electronic health record data to understand human endocrine dynamics.

    Directory of Open Access Journals (Sweden)

    D J Albers

    Full Text Available Studying physiology and pathophysiology over a broad population for long periods of time is difficult primarily because collecting human physiologic data can be intrusive, dangerous, and expensive. One solution is to use data that have been collected for a different purpose. Electronic health record (EHR data promise to support the development and testing of mechanistic physiologic models on diverse populations and allow correlation with clinical outcomes, but limitations in the data have thus far thwarted such use. For example, using uncontrolled population-scale EHR data to verify the outcome of time dependent behavior of mechanistic, constructive models can be difficult because: (i aggregation of the population can obscure or generate a signal, (ii there is often no control population with a well understood health state, and (iii diversity in how the population is measured can make the data difficult to fit into conventional analysis techniques. This paper shows that it is possible to use EHR data to test a physiological model for a population and over long time scales. Specifically, a methodology is developed and demonstrated for testing a mechanistic, time-dependent, physiological model of serum glucose dynamics with uncontrolled, population-scale, physiological patient data extracted from an EHR repository. It is shown that there is no observable daily variation the normalized mean glucose for any EHR subpopulations. In contrast, a derived value, daily variation in nonlinear correlation quantified by the time-delayed mutual information (TDMI, did reveal the intuitively expected diurnal variation in glucose levels amongst a random population of humans. Moreover, in a population of continuously (tube fed patients, there was no observable TDMI-based diurnal signal. These TDMI-based signals, via a glucose insulin model, were then connected with human feeding patterns. In particular, a constructive physiological model was shown to correctly

  17. The effect of static and dynamic spatially structured disturbances on a locally dispersing population.

    Science.gov (United States)

    Hiebeler, David E; Morin, Benjamin R

    2007-05-01

    Previous models of locally dispersing populations have shown that in the presence of spatially structured fixed habitat heterogeneity, increasing local spatial autocorrelation in habitat generally has a beneficial effect on such populations, increasing equilibrium population density. It has also been shown that with large-scale disturbance events which simultaneously affect contiguous blocks of sites, increasing spatial autocorrelation in the disturbances has a harmful effect, decreasing equilibrium population density. Here, spatial population models are developed which include both of these spatially structured exogenous influences, to determine how they interact with each other and with the endogenously generated spatial structure produced by the population dynamics. The models show that when habitat is fragmented and disturbance occurs at large spatial scales, the population cannot persist no matter how large its birth rate, an effect not seen in previous simpler models of this type. The behavior of the model is also explored when the local autocorrelation of habitat heterogeneity and disturbance events are equal, i.e. the two effects occur at the same spatial scale. When this scale parameter is very small, habitat fragmentation prevents the population from persisting because sites attempting to reproduce will drop most of their offspring on unsuitable sites; when the parameter is very large, large-scale disturbance events drive the population to extinction. Population levels reach their maximum at intermediate values of the scale parameter, and the critical values in the model show that the population will persist most easily at these intermediate scales of spatial influences. The models are investigated via spatially explicit stochastic simulations, traditional (infinite-dispersal) and improved (local-dispersal) mean-field approximations, and pair approximations.

  18. Postcatastrophe population dynamics and density dependence of an endemic island duck

    Science.gov (United States)

    Seavy, N.E.; Reynolds, M.H.; Link, W.A.; Hatfield, J.S.

    2009-01-01

    Laysan ducks (Anas laysanensis) are restricted to approximately 9 km2 in the Northwestern Hawaiian Islands, USA. To evaluate the importance of density dependence for Laysan ducks, we conducted a Bayesian analysis to estimate the parameters of a Gompertz model and the magnitude of process variation and observation error based on the fluctuations in Laysan duck abundance on Laysan Island from 1994 to 2007. This model described a stationary distribution for the population at carrying capacity that fluctuates around a long-term mean of 456 ducks and is between 316 to 636 ducks 95% of the time. This range of expected variability can be used to identify changes in population size that warn of catastrophic events. Density-dependent population dynamics may explain the recovery of Laysan duck from catastrophic declines and allow managers to identify population monitoring thresholds.

  19. [Age structure and dynamics of Quercus wutaishanica population in Lingkong Mountain of Shanxi Province, China].

    Science.gov (United States)

    Zhang, Jie; Shangguan, Tie-Liang; Duan, Yi-Hao; Guo, Wei; Liu, Wei-Hua; Guo, Dong-Gang

    2014-11-01

    Using the plant survivorship theory, the age structure, and the relationship between tree height and diameter (DBH) of Quercus wutaishanica population in Lingkong Mountain were analyzed, and the static life table was compiled and the survival curve plotted. The shuttle shape in age structure of Q. wutaishanica population suggested its temporal stability. The linear regression significantly fitted the positive correlation between tree height and DBH. The maximal life expectancy was observed among the trees beyond the age of the highest mortality and coincided with the lowest point of mortality density, suggesting the strong vitality of the seedlings and young trees that survived in the natural selection and intraspecific competition. The population stability of the Q. wutaishanica population was characterized by the Deevey-II of the survival curve. The dynamic pattern was characterized by the recession in the early phase, growth in the intermediate phase, and stability in the latter phase.

  20. Non-linear analysis indicates chaotic dynamics and reduced resilience in model-based Daphnia populations exposed to environmental stress.

    Directory of Open Access Journals (Sweden)

    Richard Ottermanns

    Full Text Available In this study we present evidence that anthropogenic stressors can reduce the resilience of age-structured populations. Enhancement of disturbance in a model-based Daphnia population lead to a repression of chaotic population dynamics at the same time increasing the degree of synchrony between the population's age classes. Based on the theory of chaos-mediated survival an increased risk of extinction was revealed for this population exposed to high concentrations of a chemical stressor. The Lyapunov coefficient was supposed to be a useful indicator to detect disturbance thresholds leading to alterations in population dynamics. One possible explanation could be a discrete change in attractor orientation due to external disturbance. The statistical analysis of Lyapunov coefficient distribution is proposed as a methodology to test for significant non-linear effects of general disturbance on populations. Although many new questions arose, this study forms a theoretical basis for a dynamical definition of population recovery.

  1. Variational Latent Gaussian Process for Recovering Single-Trial Dynamics from Population Spike Trains.

    Science.gov (United States)

    Zhao, Yuan; Park, Il Memming

    2017-05-01

    When governed by underlying low-dimensional dynamics, the interdependence of simultaneously recorded populations of neurons can be explained by a small number of shared factors, or a low-dimensional trajectory. Recovering these latent trajectories, particularly from single-trial population recordings, may help us understand the dynamics that drive neural computation. However, due to the biophysical constraints and noise in the spike trains, inferring trajectories from data is a challenging statistical problem in general. Here, we propose a practical and efficient inference method, the variational latent gaussian process (vLGP). The vLGP combines a generative model with a history-dependent point process observation, together with a smoothness prior on the latent trajectories. The vLGP improves on earlier methods for recovering latent trajectories, which assume either observation models inappropriate for point processes or linear dynamics. We compare and validate vLGP on both simulated data sets and population recordings from the primary visual cortex. In the V1 data set, we find that vLGP achieves substantially higher performance than previous methods for predicting omitted spike trains, as well as capturing both the toroidal topology of visual stimuli space and the noise correlation. These results show that vLGP is a robust method with the potential to reveal hidden neural dynamics from large-scale neural recordings.

  2. A discrete stage-structured model of California newt population dynamics during a period of drought.

    Science.gov (United States)

    Jones, Marjorie T; Milligan, William R; Kats, Lee B; Vandergon, Thomas L; Honeycutt, Rodney L; Fisher, Robert N; Davis, Courtney L; Lucas, Timothy A

    2017-02-07

    We introduce a mathematical model for studying the population dynamics under drought of the California newt (Taricha torosa), a species of special concern in the state of California. Since 2012, California has experienced a record-setting drought, and multiple studies predict drought conditions currently underway will persist and even increase in severity. Recent declines and local extinctions of California newt populations in Santa Monica Mountain streams motivate our study of the impact of drought on newt population sizes. Although newts are terrestrial salamanders, they migrate to streams each spring to breed and lay eggs. Since egg and larval stages occur in water, a precipitation deficit due to drought conditions reduces the space for newt egg-laying and the necessary habitat for larval development. To mathematically forecast newt population dynamics, we develop a nonlinear system of discrete equations that includes demographic parameters such as survival rates for newt life stages and egg production, which depend on habitat availability and rainfall. We estimate these demographic parameters using 15 years of stream survey data collected from Cold Creek in Los Angeles County, California, and our model captures the observed decline of the parameterized Cold Creek newt population. Based upon data analysis, we predict how the number of available newt egg-laying sites varies with annual precipitation. Our model allows us to make predictions about how the length and severity of drought can affect the likelihood of persistence and the time to critical endangerment of a local newt population. We predict that sustained severe drought will critically endanger the newt population but that the newt population can rebound if a drought is sufficiently short.

  3. Turkey’s Population Dynamics As A Candidate Country For EU Membership

    Directory of Open Access Journals (Sweden)

    Harun Uçak

    2011-01-01

    Full Text Available Literally, it has been accepted that one of the major obstacles to Turkey’s EU membership is in population term. There has not been any enlargement process as large as Turkey’s population as a single state in EU history before. The enlargement in 2004 which includes 10 states involved 74 million people as whole member states while Turkey’s population is 72 million inhabitants in 2007 data which is only lower than Germany’s population in all EU member states. Thus, Turkey's accession would be different from previous enlargements because of the combined impact of high population. This study compares the population dynamics, working conditions, minimum wage rates and main macroeconomic indicators between Turkey and EU member states. Turkey has young generations compared to EU countries. In the comparison of age groups proportion in total population, 0-19 age group %21,9 in EU 27 and %36,5 in Turkey, 20-39 age group is %28 in EU 27 and %34,3 in Turkey, 40-59 age group is %27,9 in EU and %20,9 in Turkey, 60 and above age group is %22,1 in EU and %9,5 in Turkey. Thus, population dynamics of Turkey could make a contribution to offsetting the ageing of EU 27 societies if the membership would occur in the future. However, minimum wage rates in Turkey are lower than many EU member states but generally higher than EU member states located in Central and Eastern Europe. Thus, immigration possibilities from Turkey can be expected to Western European Countries, but not the same direction to Central and Eastern Europe Countries. Furthermore, the process in macroeconomic indicators will be a determinant in immigration expectations while Turkey’s GDP has been grown faster than EU level recently.

  4. Seasonal Population Dynamics of the Asian Citrus Psyllid, Diaphorina citri Kuwayama in Sarawak

    Directory of Open Access Journals (Sweden)

    Stephen L.C. Teck

    2011-01-01

    Full Text Available Problem statement: Effective control of phytophagous pests requires a thorough understanding of their seasonal population dynamics, dispersion behavior, natural enemy activity and climate. To date, although very little detail information had been published on the ecology of Diaphorina citri. The objective of this investigation was to test through field experiment the hypothesis that the major factors influencing local D. citri populations particularly their seasonal population dynamics in Sarawak are (a flushing cycles, (b climate and (c the impact of the primary parasitoids namely Tamarixia radiata and Diaphorencyrtus aligarhensis. Approach: Seasonal abundance D. citri was studied weekly from March 1998 to December 2000 in the 1-ha citrus honey mandarin (Citrus aurantium L. commercial orchard at Jemukan (1° 33'N, 110° 41'E, Kota Samarahan Division, Southwest Sarawak, in Malaysia. Results: Field studies on citrus trees showed that the D. citri population fluctuates throughout the year on citrus honey mandarin in Sarawak. Generations overlapped but adult and egg population peaks for a short period generally coincided with three annual flushing cycles, in August-September, February-March and June-July between March 1998 and December 2000. Conclusion: Psyllid population levels are positively related to the availability of new shoot flushes. Psyllid populations are adversely affected by weather conditions and parasitoids. Adult psyllid populations increased exponentially during periods of flush growth and migration and dispersal of the adults was also related to flushing cycles. Dispersal and colonization of new trees is greatest in September-October, at the onset of the rainy season.

  5. Endogenous viral elements in algal genomes

    Institute of Scientific and Technical Information of China (English)

    WANG Liang; YU Jun; WU Shuangxiu; LIU Tao; SUN Jing; CHI Shan; LIU Cui; LI Xingang; YIN Jinlong; WANG Xumin

    2014-01-01

    Endogenous viral elements (EVEs) are host-genomic fragments originated from viral genomes. They have been found universally in animal and plant genomes. Here we carried out a systematic screening and analy-sis of EVEs in algal genomes and found that EVEs commonly exist in algal genomes. We classified the EVE fragments into three categories according to the length of EVE fragments. Due to the probability of sequence similarity by chance, we ignored the potential function of medium-length EVE fragments. However, long-length EVE fragments probably had capability to encode protein domains or even entire proteins, and some short-length EVE fragments had high similarity with host's siRNA sequences and possibly served functions of small RNAs. Therefore, short and long EVE fragments might provide regulomic and proteomic novelty to the host's metabolism and adaptation. We also found several EVE fragments shared by more than 3 algal genomes. By phylogenetic analysis of the shared EVEs and their corresponding species, we found that the integration of viral fragments into host genomes was an ancient event, possibly before the divergence of Chlorophytes and Ochrophytes. Our findings show that there is a frequent genetic flow from viruses to algal genomes. Moreover, study on algal EVEs shed light on the virus-host interaction in large timescale and could also help us understand the balance of marine ecosystems.

  6. Climate, invasive species and land use drive population dynamics of a cold-water specialist

    Science.gov (United States)

    Kovach, Ryan P.; Al-Chokhachy, Robert K.; Whited, Diane C.; Schmetterling, David A.; Dux, Andrew M; Muhlfeld, Clint C.

    2017-01-01

    Climate change is an additional stressor in a complex suite of threats facing freshwater biodiversity, particularly for cold-water fishes. Research addressing the consequences of climate change on cold-water fish has generally focused on temperature limits defining spatial distributions, largely ignoring how climatic variation influences population dynamics in the context of other existing stressors.We used long-term data from 92 populations of bull trout Salvelinus confluentus – one of North America's most cold-adapted fishes – to quantify additive and interactive effects of climate, invasive species and land use on population dynamics (abundance, variability and growth rate).Populations were generally depressed, more variable and declining where spawning and rearing stream habitat was limited, invasive species and land use were prevalent and stream temperatures were highest. Increasing stream temperature acted additively and independently, whereas land use and invasive species had additive and interactive effects (i.e. the impact of one stressor depended on exposure to the other stressor).Most (58%–78%) of the explained variation in population dynamics was attributed to the presence of invasive species, differences in life history and management actions in foraging habitats in rivers, lakes and reservoirs. Although invasive fishes had strong negative effects on populations in foraging habitats, proactive control programmes appeared to effectively temper their negative impact.Synthesis and applications. Long-term demographic data emphasize that climate warming will exacerbate imperilment of cold-water specialists like bull trout, yet other stressors – especially invasive fishes – are immediate threats that can be addressed by proactive management actions. Therefore, climate-adaptation strategies for freshwater biodiversity should consider existing abiotic and biotic stressors, some of which provide potential and realized opportunity for conservation

  7. Population dynamics in the presence of quasispecies effects and changing environments

    Science.gov (United States)

    Forster, Robert Burke

    2006-12-01

    This thesis explores how natural selection acts on organisms such as viruses that have either highly error-prone reproduction or face variable environmental conditions or both. By modeling population dynamics under these conditions, we gain a better understanding of the selective forces at work, both in our simulations and hopefully also in real organisms. With an understanding of the important factors in natural selection we can forecast not only the immediate fate of an existing population but also in what directions such a population might evolve in the future. We demonstrate that the concept of a quasispecies is relevant to evolution in a neutral fitness landscape. Motivated by RNA viruses such as HIV, we use RNA secondary structure as our model system and find that quasispecies effects arise both rapidly and in realistically small populations. We discover that the evolutionary effects of neutral drift, punctuated equilibrium and the selection for mutational robustness extend to the concept of a quasispecies. In our study of periodic environments, we consider the tradeoffs faced by quasispecies in adapting to environmental change. We develop an analytical model to predict whether evolution favors short-term or long-term adaptation and validate our model through simulation. Our results bear directly on the population dynamics of viruses such as West Nile that alternate between two host species. More generally, we discover that a selective pressure exists under these conditions to fuse or split genes with complementary environmental functions. Lastly, we study the general effects of frequency-dependent selection on two strains competing in a periodic environment. Under very general assumptions, we prove that stable coexistence rather than extinction is the likely outcome. The population dynamics of this system may be as simple as stable equilibrium or as complex as deterministic chaos.

  8. [Population dynamics of the palm Euterpe oleracea (Arecaceae) from flooded forests in Choco, Colombian Pacific].

    Science.gov (United States)

    Arango, Diego A; Duque, Alvaro J; Muñoz, Edinson

    2010-03-01

    The palm Euterpe oleracea is a dominant and promising species in flood plains of the Atrato river, Choco region of Colombia. We assessed the population dynamics of this species through growth rates, mortality and recruitment patterns for a period of two and a half years. Dynamic rates were compared among mixed and pure flood plain palm forests. These forests types were associated to different flooding regimes. Trees and palms were thinned in a portion for each forest type, the rest was left undisturbed. We used projection matrices to follow population trends. Thinning increased the transition probability of smaller individuals, but decreased it for larger individuals, as is typical of light demanding species. Thinning also increased mortality rates in almost all size classes, but did not affect recruitment rates. Under natural conditions, the E. oleracea populations are in equilibrium in pure and mixed forests. Thinning increased population growth in both forest types, suggesting the role played by density-dependent processes on the population size of this species.

  9. An Exergy-Based Model for Population Dynamics: Adaptation, Mutualism, Commensalism and Selective Extinction

    Directory of Open Access Journals (Sweden)

    Enrico Sciubba

    2012-10-01

    Full Text Available Following the critical analysis of the concept of “sustainability”, developed on the basis of exergy considerations in previous works, an analysis of possible species “behavior” is presented and discussed in this paper. Once more, we make use of one single axiom: that resource consumption (material and immaterial can be quantified solely in terms of exergy flows. This assumption leads to a model of population dynamics that is applied here to describe the general behavior of interacting populations. The resulting equations are similar to the Lotka-Volterra ones, but more strongly coupled and intrinsically non-linear: as such, their solution space is topologically richer than those of classical prey-predator models. In this paper, we address an interesting specific problem in population dynamics: if a species assumes a commensalistic behavior, does it gain an evolutionary advantage? And, what is the difference, in terms of the access to the available exergy resources, between mutualism and commensalism? The model equations can be easily rearranged to accommodate both types of behavior, and thus only a brief discussion is devoted to this facet of the problem. The solution space is explored in the simplest case of two interacting populations: the model results in population curves in phase space that can satisfactorily explain the evolutionistic advantages and drawbacks of either behavior and, more importantly, identify the presence or absence of a “sustainable” solution in which both species survive.

  10. Development of conceptual ecological models linking management of the Missouri River to pallid sturgeon population dynamics

    Science.gov (United States)

    Jacobson, Robert B.; Parsley, Michael J.; Annis, Mandy L.; Colvin, Michael E.; Welker, Timothy L.; James, Daniel A.

    2015-01-01

    This report documents the process of developing and refining conceptual ecological models (CEMs) for linking river management to pallid sturgeon (Scaphirhynchus albus) population dynamics in the Missouri River. The refined CEMs are being used in the Missouri River Pallid Sturgeon Effects Analysis to organize, document, and formalize an understanding of pallid sturgeon population responses to past and future management alternatives. The general form of the CEMs, represented by a population-level model and component life-stage models, was determined in workshops held in the summer of 2013. Subsequently, the Missouri River Pallid Sturgeon Effects Analysis team designed a general hierarchical structure for the component models, refined the graphical structure, and reconciled variation among the components and between models developed for the upper river (Upper Missouri & Yellowstone Rivers) and the lower river (Missouri River downstream from Gavins Point Dam). Importance scores attributed to the relations between primary biotic characteristics and survival were used to define a candidate set of working dominant hypotheses about pallid sturgeon population dynamics. These CEMs are intended to guide research and adaptive-management actions to benefit pallid sturgeon populations in the Missouri River.

  11. On the heterogeneity of human populations as reflected by mortality dynamics

    Science.gov (United States)

    Avraam, Demetris; Arnold, Séverine; Vasieva, Olga; Vasiev, Bakhtier

    2016-01-01

    The heterogeneity of populations is used to explain the variability of mortality rates across the lifespan and their deviations from an exponential growth at young and very old ages. A mathematical model that combines the heterogeneity with the assumption that the mortality of each constituent subpopulation increases exponentially with age, has been shown to successfully reproduce the entire mortality pattern across the lifespan and its evolution over time. In this work we aim to show that the heterogeneity is not only a convenient consideration for fitting mortality data but is indeed the actual structure of the population as reflected by the mortality dynamics over age and time. In particular, we show that the model of heterogeneous population fits mortality data better than other commonly used mortality models. This was demonstrated using cohort data taken for the entire lifespan as well as for only old ages. Also, we show that the model can reproduce seemingly contradicting observations in late-life mortality dynamics. Finally, we show that the homogenisation of a population, observed by fitting the model to actual data of consecutive periods, can be associated with the evolution of allele frequencies if the heterogeneity is assumed to reflect the genetic variations within the population. PMID:27875807

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

    Science.gov (United States)

    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.

  13. Factors affecting population dynamics of maternally transmitted endosymbionts in Bemisia tabaci.

    Directory of Open Access Journals (Sweden)

    Huipeng Pan

    Full Text Available While every individual of Bemisia tabaci (Hemiptera: Aleyrodidae harbors the primary symbiont (P-symbiont Portiera, the infection frequencies of the six secondary symbionts (S-symbionts including Hamiltonella, Arsenophonus, Cardinium, Wolbachia, Rickettsia and Fritschea vary greatly among different populations. To characterize the factors influencing the infection dynamics of the six S-symbionts in B. tabaci, gene-specific PCR were conducted to screen for the presence of the P-symbiont Portiera and the six S-symbionts in 61 (17 B and 44 Q biotypes field populations collected from different plant species and locations in China. All individuals of the 61 populations hosted the P-symbiont Portiera, but none of them harbored Arsenophonus and Fritschea. The presence and infection rates of Hamiltonella, Cardinium, Rickettsia, Wolbachia and their co-infections Rickettsia + Hamiltonella (RH, Rickettsia + Cardinium (RC, Hamiltonella + Cardinium (HC and Rickettsia + Hamiltonella + Cardinium (RHC varied significantly among the 61 field populations; and the observed variations can be explained by biotypes, sexes, host plants and geographical locations of these field populations. Taken together, at least three factors including biotype, host plant and geographical location affect the infection dynamics of S-symbionts in B. tabaci.

  14. Mitochondrial DNA variants help monitor the dynamics of Wolbachia invasion into host populations.

    Science.gov (United States)

    Yeap, H L; Rašić, G; Endersby-Harshman, N M; Lee, S F; Arguni, E; Le Nguyen, H; Hoffmann, A A

    2016-03-01

    Wolbachia is the most widespread endosymbiotic bacterium of insects and other arthropods that can rapidly invade host populations. Deliberate releases of Wolbachia into natural populations of the dengue fever mosquito, Aedes aegypti, are used as a novel biocontrol strategy for dengue suppression. Invasion of Wolbachia through the host population relies on factors such as high fidelity of the endosymbiont transmission and limited immigration of uninfected individuals, but these factors can be difficult to measure. One way of acquiring relevant information is to consider mitochondrial DNA (mtDNA) variation alongside Wolbachia in field-caught mosquitoes. Here we used diagnostic mtDNA markers to differentiate infection-associated mtDNA haplotypes from those of the uninfected mosquitoes at release sites. Unique haplotypes associated with Wolbachia were found at locations outside Australia. We also performed mathematical and qualitative analyses including modelling the expected dynamics of the Wolbachia and mtDNA variants during and after a release. Our analyses identified key features in haplotype frequency patterns to infer the presence of imperfect maternal transmission of Wolbachia, presence of immigration and possibly incomplete cytoplasmic incompatibility. We demonstrate that ongoing screening of the mtDNA variants should provide information on maternal leakage and immigration, particularly in releases outside Australia. As we demonstrate in a case study, our models to track the Wolbachia dynamics can be successfully applied to temporal studies in natural populations or Wolbachia release programs, as long as there is co-occurring mtDNA variation that differentiates infected and uninfected populations.

  15. Effect of abiotic factors on seasonal population dynamics of Lutzomyia longipalpis (Diptera: Psychodidae) in northeastern Brazil.

    Science.gov (United States)

    Ximenes, Maria de Fátima Freire de Melo; Castellón, Eloy G; De Souza, Maria de Fátima; Menezes, Alexandre A Lara; Queiroz, José Wilton; Macedo e Silva, Virgínia Penéllope; Jerônimo, Selma M B

    2006-09-01

    The resurgence of visceral leishmaniasis in Brazil increases the need for studies to elucidate the spatial and temporal dynamics of Lutzomyia longipalpis (Lutz and Neiva) (Diptera: Psychodidae), the vector of Leishmania infantum, the causative agent of visceral leishmaniasis in Brazil. Sand flies were captured in peridomestic habitats biweekly for 3 yr. Cross-correlation tests and spectral analysis were used to analyze the simultaneous and lag-time correlations between Lu. longipalpis population densities and abiotic factors of temperature, relative humidity, wind velocity, and rainfall. Distinct seasonal patterns were observed for males and females, with intervals of 6 mo between population peaks for males and 12 mo for females. Peak female population densities lagged 3 mo behind the maximum annual temperature. Female population density was negatively correlated with relative humidity. An increase in average wind velocity was followed by a decrease in the number of females for 2 wk. Understanding the relationship between the seasonal population dynamics of Lu. longipalpis and abiotic factors will contribute to the design of better control measures to decrease transmission of L. infantum and consequently the incidence of leishmaniasis.

  16. A consumer-resource approach to the density-dependent population dynamics of mutualism

    Science.gov (United States)

    Holland, J. Nathaniel; DeAngelis, Donald L.

    2010-01-01

    Like predation and competition, mutualism is now recognized as a consumer resource (C-R) interaction, including, in particular, bi-directional (e.g., coral, plant- mycorrhizae) and uni-directional (e.g., ant-plant defense, plant-pollinator) C-R mutualisms. Here, we develop general theory for the density-dependent population dynamics of mutualism based on the C-R mechanism of interspecific interaction. To test the influence of C-R interactions on the dynamics and stability of bi- and uni-directional C-R mutualisms, we developed simple models that link consumer functional response of one mutualistic species with the resources supplied by another. Phase-plane analyses show that the ecological dynamics of C-R mutualisms are stable in general. Most transient behavior leads to an equilibrium of mutualistic coexistence, at which both species densities are greater than in the absence of interactions. However, due to the basic nature of C-R interactions, certain density-dependent conditions can lead to C-R dynamics characteristic of predator-prey interactions, in which one species overexploits and causes the other to go extinct. Consistent with empirical phenomena, these results suggest that the C-R interaction can provide a broad mechanism for understanding density-dependent population dynamics of mutualism. By unifying predation, competition, and mutualism under the common ecological framework of consumer-resource theory, we may also gain a better understanding of the universal features of interspecific interactions in general.

  17. Ageing dynamics of a human-capital-specific population: A demographic perspective

    Directory of Open Access Journals (Sweden)

    Dimiter Philipov

    2014-12-01

    Full Text Available Background: Research on how rising human capital affects the consequences of population ageing rarely considers the fact that the human capital of the elderly population is composed in a specific way that is shaped by their earlier schooling and work experience. For an elderly population of a fixed size and age-sex composition, this entails that the higher its human capital, the greater the total amount of public pensions to be paid. Objective: The main purpose of this paper is to analyse the link between human capital and retiree benefits and its effect on population ageing from a demographic viewpoint. Methods: We construct an old age dependency ratio (OADR, in which each person, whether in the numerator or the denominator, is assigned the number of units corresponding to his/her level of human capital. Based on data for Italy, we study the dynamics of this human-capital-specific OADR with the help of multistate population projections to 2107. Results: Our results show that under specific conditions a constant or moderately growing human capital may aggravate the consequences of population ageing rather than alleviate them. Conclusions: With those findings, the authors would like to stimulate the debate on the search for demographic and/or socio-economic solutions to the challenges posed by population ageing.

  18. Population Dynamics of Anastrepha ludens (Loew) (Diptera: Tephritidae) on Citrus Areas in Southern Tamaulipas, Mexico.

    Science.gov (United States)

    Vanoye-Eligio, V; Barrientos-Lozano, L; Pérez-Castañeda, R; Gaona-García, G; Lara-Villalon, M

    2015-12-01

    An analysis of adult population fluctuation of Anastrepha ludens (Loew) was performed in southern Tamaulipas, Mexico from 2008 to 2011. The aim was to analyze population dynamics of A. ludens and its relationships with climatic factors in the citrus region of Llera, Tamaulipas, Mexico. Population densities were weekly examined to identify variation through the year and study period. Four periods were identified according to population size, amplitude, host availability and season of the year. The correlation between population density vs. rainfall and temperature (average, minimum and maximum) was determined by linear and multiple regression analyses. Simple linear regression analysis showed that population density with minimum temperature and rainfall was the most consistent correlation, whereas in multiple regression analysis, rainfall and maximum temperature showed more consistency. A seasonal association between the availability of commercial host, climatic variation, and population peaks of A. ludens was determined. This study may have practical implications for the design of specific control strategies, monitoring, and infestation prevention based on different phases of the pest through the year. This strategy, along with the area-wide approach implemented by the Plant Protection Service may lead to an optimization of material, financial and human resources.

  19. Recession of Tussilago farfara (L. population from the agro coenose as a result of cultivation abandonment. I The effect of fallowing on population dynamics

    Directory of Open Access Journals (Sweden)

    Anna Namura-Ochalska

    2014-01-01

    Full Text Available The paper evaluates the effect of fallowing on seasonal and multiyear dynamics, as well as on the spatial structure of Tussilago farfara population. In four years turfing and rapid increase in the size of grass populations - those of Agropyron repens (L. PB. and Dactylis glomerata caused the elimination of Tussilago farfara population. The studies have showed that a decrease in the population size resulted from hampering of both vegetative and generative reproduction. The interspecific competition for available space seems to be a crucial factor limiting emergence of new shoots. In the agrocoenose big population size of Tussilago farfara remained throughout the studies.

  20. Dynamics of a Lotka-Volterra type model with applications to marine phage population dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Gavin, C [School of Mathematical Sciences University College Cork, Cork (Ireland); Pokrovskii, A [School of Mathematical Sciences University College Cork, Cork (Ireland); Prentice, M [Department of Microbiology University College Cork, Cork (Ireland); Sobolev, V [Department of Differential Equations and Control Theory Samara State University, Akademika Pavlova Street, 1, 443011 (Russian Federation)

    2006-12-01

    The famous Lotka-Volterra equations play a fundamental role in the mathematical modeling of various ecological and chemical systems. A new modification of these equations has been recently suggested to model the structure of marine phage populations, which are the most abundant biological entities in the biosphere. The purpose of the paper is: (i) to make some methodical remarks concerning this modification; (ii) to discuss new types of canards which arise naturally in this context; (iii) to present results of some numerical experiments.

  1. Removal of Zn(II) from simulated wastewater using an algal biofilm.

    Science.gov (United States)

    Liu, Cuixia; Hu, Zhiquan; Zuo, Jiaolan; Hu, Mian; Xiao, Bo

    2014-01-01

    An algal biofilm was employed as a novel kind of adsorbing material to remove Zn(II) from simulated wastewater. The algal biofilm system formed by Oedogonium sp. was operated in a dynamic mode for a period of 14 days with an initial Zn(II) concentration of 10 mg/L. The average effluent Zn(II) concentration was 0.247 mg/L and the average removal efficiency reached 97.7%. The effects of Zn(II) on key algal physiological and biochemical indices such as chlorophyll content, nitrate reductase and superoxide dismutase activity, extracellular polysaccharides (EPS), and soluble protein levels were studied. Our results showed that the algal biofilm could adapt to the simulated wastewater containing Zn(II). Scanning electron microscope and Fourier transform infrared spectroscopy analyses of algal biofilm revealed the presence of carboxyl, amino, and sulphonate groups, which were the main functional groups of EPS and proteins, and these were likely responsible for biosorption of the Zn(II) ions.

  2. On Oscillatory Pattern of Malaria Dynamics in a Population with Temporary Immunity

    Directory of Open Access Journals (Sweden)

    J. Tumwiine

    2007-01-01

    Full Text Available We use a model to study the dynamics of malaria in the human and mosquito population to explain the stability patterns of malaria. The model results show that the disease-free equilibrium is globally asymptotically stable and occurs whenever the basic reproduction number, R0 is less than unity. We also note that when R0>1, the disease-free equilibrium is unstable and the endemic equilibrium is stable. Numerical simulations show that recoveries and temporary immunity keep the populations at oscillation patterns and eventually converge to a steady state.

  3. Seasonal population dynamics of the greenhouse whitefly Trialeurodes vaporariorum (Homoptera: Aleyrodidae) on strawberries in Southern California.

    Science.gov (United States)

    Bi, J L; Toscano, N C; Ballmer, G R

    2002-12-01

    The greenhouse whitefly, Trialeurodes vaporariorum (Westwood), has recently become a major insect pest of strawberries in Southern California. The population dynamics of this pest were monitored over 2 yr in six commercial strawberry fields near the coastal communities of Oxnard and Ventura under two crop-production regimes, summer- and fall-planted strawberries. Adult whitefly numbers generally peaked during the February through May period for fall-planted strawberries and during the October through November period for summer-planted strawberries. Population densities varied greatly among fields within each regime and the differences were likely caused by surrounding alternate host crops.

  4. Dynamics of sexual populations structured by a space variable and a phenotypical trait

    KAUST Repository

    Mirrahimi, Sepideh

    2013-03-01

    We study sexual populations structured by a phenotypic trait and a space variable, in a non-homogeneous environment. Departing from an infinitesimal model, we perform an asymptotic limit to derive the system introduced in Kirkpatrick and Barton (1997). We then perform a further simplification to obtain a simple model. Thanks to this simpler equation, we can describe rigorously the dynamics of the population. In particular, we provide an explicit estimate of the invasion speed, or extinction speed of the species. Numerical computations show that this simple model provides a good approximation of the original infinitesimal model, and in particular describes quite well the evolution of the species\\' range. © 2013 Elsevier Inc.

  5. Life history and population dynamics of an estuarine amphipod, Eriopisa chilkensis Chilton (Gammaridae)

    Digital Repository Service at National Institute of Oceanography (India)

    Aravind, N.P.; Sheeba, P.; Nair, K.K.C.; Achuthankutty, C.T.

    in fish culture. Eriopisa chilkensis can withstand wide variations in salinity (5-35) and temperature (27.5 - 34 degrees C) of the medium. It was cultured in un-aerated finger bowls using dried algal matter (Chara sp.) as food. The life span of females...

  6. Algal Biology Toolbox Workshop Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2016-08-01

    DOE-EERE's Bioenergy Technologies Office (BETO) works to accelerate the development of a sustainable, cost-competitive, advanced biofuel industry that can strengthen U.S. energy security, environmental quality, and economic vitality, through research, development, and demonstration projects in partnership with industry, academia, and national laboratory partners. BETO’s Advanced Algal Systems Program (also called the Algae Program) has a long-term applied research and development (R&D) strategy to increase the yields and lower the costs of algal biofuels. The team works with partners to develop new technologies, to integrate technologies at commercially relevant scales, and to conduct crosscutting analyses to better understand the potential and challenges of the algal biofuels industry. Research has indicated that this industry is capable of producing billions of gallons of renewable diesel, gasoline, and jet fuels annually. R&D activities are integrated with BETO’s longstanding effort to accelerate the commercialization of lignocellulosic biofuels.

  7. Environmental and Health Effects Associated With Harmful Algal Bloom and Marine Algal Toxins in China

    Institute of Scientific and Technical Information of China (English)

    TIAN YAN; MING-JIANG ZHOU

    2004-01-01

    The frequency and scale of Harmful Algal Bloom (HAB) and marine algal toxin incidents have been increasing and spreading in the past two decades, causing damages to the marine environment and threatening human life through contaminated seafood. To better understand the effect of HAB and marine algal toxins on marine environment and human health in China, this paper overviews HAB occurrence and marine algal toxin incidents, as well as their environmental and health effects in this country. HAB has been increasing rapidly along the Chinese coast since the 1970s, and at least 512 documented HAB events have occurred from 1952 to 2002 in the Chinese mainland. It has been found that PSP and DSP toxins are distributed widely along both the northern and southern Chinese coasts. The HAB and marine algal toxin events during the 1990s in China were summarized, showing that the HAB and algal toxins resulted in great damages to local fisheries, marine culture, quality of marine environment, and human health. Therefore, to protect the coastal environment and human health, attention to HAB and marine algal toxins is urgently needed from the environmental and epidemiological view.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    1999-07-01

    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.

  10. Phenogenetic analysis of crayfishes Astacus astacus population dynamics after introduction into natural lake

    Science.gov (United States)

    Sapunov, Valentin; Fedotov, Valery

    2016-04-01

    Phenogenetic indication is check of environment state by detectable characters of population, such as morphological variability, sex relation and sex dimorphism. This characters dynamics was followed within crayfish population during process of adaptation for pond. Crayfishes are stenobionts needing clean water. The pattern of different crayfish species is criteria for pond dynamics. Mathematical model describing occupation of lake by Nobel crayfishes Astacus astacus is describing by two variants. The first is general universal model, the second is model appropriate for lake Berezno from Pskov region (North - West of Russia). This situation may be considered as representative for different lakes taking into account ecological specific of every lake. Crayfishes were introduced into the lake at 1995. At 1998 population was reorganized by switching on genetic program of migration for maximal using of assimilating capacity of lake. During 2000 - 2015 population was stable and its characters were oscillated according to ecological state and automatic genetics processes. Population is monomorphic, the one morphotype is dominant. Sizes within this morpotype are distributed according to Gauss law (making correction for methods of catching). The square deviation increases in first generation and decreases in accordance to population adaptation. The Nobel crayfish is typical macrohydrobiont and may be used as biological indicator of ecological state of water. Such a method of monitoring is cheap and effective and may be used as adding to tradition monitoring manner. Parallel to monitoring of natural crayfish population the program of use of artificial test system for water quality was introduced in water-supply station of St. Petersburg.

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

    Science.gov (United States)

    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.

  12. Algal recycling enhances algal productivity and settleability in Pediastrum boryanum pure cultures.

    Science.gov (United States)

    Park, Jason B K; Craggs, Rupert J; Shilton, Andy N

    2015-12-15

    Recycling a portion of gravity harvested algae (i.e. algae and associated bacteria biomass) has been shown to improve both algal biomass productivity and harvest efficiency by maintaining the dominance of a rapidly-settleable colonial alga, Pediastrum boryanum in both pilot-scale wastewater treatment High Rate Algal Ponds (HRAP) and outdoor mesocosms. While algal recycling did not change the relative proportions of algae and bacteria in the HRAP culture, the contribution of the wastewater bacteria to the improved algal biomass productivity and settleability with the recycling was not certain and still required investigation. P. boryanum was therefore isolated from the HRAP and grown in pure culture on synthetic wastewater growth media under laboratory conditions. The influence of recycling on the productivity and settleability of the pure P. boryanum culture was then determined without wastewater bacteria present. Six 1 L P. boryanum cultures were grown over 30 days in a laboratory growth chamber simulating New Zealand summer conditions either with (Pr) or without (Pc) recycling of 10% of gravity harvested algae. The cultures with recycling (Pr) had higher algal productivity than the controls (Pc) when the cultures were operated at both 4 and 3 d hydraulic retention times by 11% and 38% respectively. Furthermore, algal recycling also improved 1 h settleability from ∼60% to ∼85% by increasing the average P. boryanum colony size due to the extended mean cell residence time and promoted formation of large algal bio-flocs (>500 μm diameter). These results demonstrate that the presence of wastewater bacteria was not necessary to improve algal productivity and settleability with algal recycling.

  13. Biodegradability of algal-derived organic matter in a large artificial lake by using stable isotope tracers.

    Science.gov (United States)

    Lee, Yeonjung; Lee, Bomi; Hur, Jin; Min, Jun-Oh; Ha, Sun-Yong; Ra, Kongtae; Kim, Kyung-Tae; Shin, Kyung-Hoon

    2016-05-01

    In order to understand the biodegradability of algal-derived organic matter, biodegradation experiments were conducted with (13)C and (15)N-labeled natural phytoplankton and periphytic algal populations in experimental conditions for 60 days. Qualitative changes in the dissolved organic matter were also determined using parallel factor analysis and the stable carbon isotopic composition of the hydrophobic dissolved organic matter through the experimental period. Although algal-derived organic matter is considered to be easily biodegradable, the initial amounts of total organic carbon newly produced by phytoplankton and periphytic algae remained approximately 16 and 44 % after 60 days, respectively, and about 22 and 43 % of newly produced particulate nitrogen remained. Further, the dissolved organic carbon derived from both algal populations increased significantly after 60 days. Although the dissolved organic matter gradually became refractory, the contributions of the algal-derived organic matter to the dissolved organic matter and hydrophobic dissolved organic matter increased. Our laboratory experimental results suggest that algal-derived organic matter produced by phytoplankton and periphytic algae could contribute significantly to the non-biodegradable organic matter through microbial transformations.

  14. Olive Fruit Fly (Bactrocera oleae) Population Dynamics in the Eastern Mediterranean: Influence of Exogenous Uncertainty on a Monophagous Frugivorous Insect.

    Science.gov (United States)

    Ordano, Mariano; Engelhard, Izhar; Rempoulakis, Polychronis; Nemny-Lavy, Esther; Blum, Moshe; Yasin, Sami; Lensky, Itamar M; Papadopoulos, Nikos T; Nestel, David

    2015-01-01

    Despite of the economic importance of the olive fly (Bactrocera oleae) and the large amount of biological and ecological studies on the insect, the factors driving its population dynamics (i.e., population persistence and regulation) had not been analytically investigated until the present study. Specifically, our study investigated the autoregressive process of the olive fly populations, and the joint role of intrinsic and extrinsic factors molding the population dynamics of the insect. Accounting for endogenous dynamics and the influences of exogenous factors such as olive grove temperature, the North Atlantic Oscillation and the presence of potential host fruit, we modeled olive fly populations in five locations in the Eastern Mediterranean region. Our models indicate that the rate of population change is mainly shaped by first and higher order non-monotonic, endogenous dynamics (i.e., density-dependent population feedback). The olive grove temperature was the main exogenous driver, while the North Atlantic Oscillation and fruit availability acted as significant exogenous factors in one of the five populations. Seasonal influences were also relevant for three of the populations. In spite of exogenous effects, the rate of population change was fairly stable along time. We propose that a special reproductive mechanism, such as reproductive quiescence, allows populations of monophagous fruit flies such as the olive fly to remain stable. Further, we discuss how weather factors could impinge constraints on the population dynamics at the local level. Particularly, local temperature dynamics could provide forecasting cues for management guidelines. Jointly, our results advocate for establishing monitoring programs and for a major focus of research on the relationship between life history traits and populations dynamics.

  15. Dynamics of a local badger (Meles meles) population in the Netherlands over the years 1983-2001

    NARCIS (Netherlands)

    Apeldoorn, van R.C.; Vink, J.; Matyástík, T.

    2006-01-01

    Long-term data on badger population dynamics are scarce. For 19 years data on badger and sett numbers were collected by direct observation of a Local population in the province of Utrecht, the Netherlands. Analysis of these data show two different patterns of population growth. The first shows a sto

  16. Uncoupling the effects of seed predation and seed dispersal by granivorous ants on plant population dynamics.

    Directory of Open Access Journals (Sweden)

    Xavier Arnan

    Full Text Available 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.

  17. Population Dynamics in Cold Gases Resulting from the Long-Range Dipole-Dipole Interaction

    CERN Document Server

    Mandilara, A; Pillet, P

    2009-01-01

    We consider the effect of the long range dipole-dipole interaction on the excitation exchange dynamics of cold two-level atomic gase in the conditions where the size of the atomic cloud is large as compared to the wavelength of the dipole transition. We show that this interaction results in population redistribution across the atomic cloud and in specific spectra of the spontaneous photons emitted at different angles with respect to the direction of atomic polarization.

  18. A distributional solution to a hyperbolic problem arising in population dynamics

    Directory of Open Access Journals (Sweden)

    Irina Kmit

    2007-10-01

    Full Text Available We consider a generalization of the Lotka-McKendrick problem describing the dynamics of an age-structured population with time-dependent vital rates. The generalization consists in allowing the initial and the boundary conditions to be derivatives of the Dirac measure. We construct a unique D'-solution in the framework of intrinsic multiplication of distributions. We also investigate the regularity of this solution.

  19. Evaluation of damage, food attractants and population dynamics of strawberry sap beetle

    OpenAIRE

    Fornari,Rodrigo A; Machota Junior,Ruben; Bernardi, Daniel; Botton, Marcos; Pastori,Patrik Luiz

    2013-01-01

    The strawberry sap beetle [Lobiopa insularis (Coleoptera: Nitidulidae)] is one of the most important pests of strawberry crops. This study aimed to determine the relationship between strawberry fruit maturation stages and the feeding of sap beetle in laboratory and to evaluate food attractants and population dynamics of this species during the crop season. To evaluate the feeding preference of strawberry fruits 'Camarosa' at different maturation stages [green (G), semi-ripe (SM) a...

  20. A General Discrete Time Model of Population Dynamics in the Presence of an Infection

    Directory of Open Access Journals (Sweden)

    Giuseppe Izzo

    2009-01-01

    Full Text Available We present a set of difference equations which generalizes that proposed in the work of G. Izzo and A. Vecchio (2007 and represents the discrete counterpart of a larger class of continuous model concerning the dynamics of an infection in an organism or in a host population. The limiting behavior of this new discrete model is studied and a threshold parameter playing the role of the basic reproduction number is derived.

  1. Human population and atmospheric carbon dioxide growth dynamics: Diagnostics for the future

    Science.gov (United States)

    Hüsler, A. D.; Sornette, D.

    2014-10-01

    We analyze the growth rates of human population and of atmospheric carbon dioxide by comparing the relative merits of two benchmark models, the exponential law and the finite-time-singular (FTS) power law. The later results from positive feedbacks, either direct or mediated by other dynamical variables, as shown in our presentation of a simple endogenous macroeconomic dynamical growth model describing the growth dynamics of coupled processes involving human population (labor in economic terms), capital and technology (proxies by CO2 emissions). Human population in the context of our energy intensive economies constitutes arguably the most important underlying driving variable of the content of carbon dioxide in the atmosphere. Using some of the best databases available, we perform empirical analyses confirming that the human population on Earth has been growing super-exponentially until the mid-1960s, followed by a decelerated sub-exponential growth, with a tendency to plateau at just an exponential growth in the last decade with an average growth rate of 1.0% per year. In contrast, we find that the content of carbon dioxide in the atmosphere has continued to accelerate super-exponentially until 1990, with a transition to a progressive deceleration since then, with an average growth rate of approximately 2% per year in the last decade. To go back to CO2 atmosphere contents equal to or smaller than the level of 1990 as has been the broadly advertised goals of international treaties since 1990 requires herculean changes: from a dynamical point of view, the approximately exponential growth must not only turn to negative acceleration but also negative velocity to reverse the trend.

  2. Population dynamics of wild rodents induce stochastic fadeouts of a zoonotic pathogen.

    Science.gov (United States)

    Guzzetta, Giorgio; Tagliapietra, Valentina; Perkins, Sarah E; Hauffe, Heidi C; Poletti, Piero; Merler, Stefano; Rizzoli, Annapaola

    2017-02-19

    Stochastic processes play an important role in the infectious disease dynamics of wildlife, especially in species subject to large population oscillations. Here we study the case of a free ranging population of yellow-necked mice (Apodemus flavicollis) in northern Italy, where circulation of Dobrava-Belgrade hantavirus (DOBV) has been detected intermittently since 2001, until an outbreak emerged in 2010. We analyzed the transmission dynamics of the recent outbreak using a computational model that accounts for seasonal changes of the host population and territorial behavior. Model parameters were informed by capture-mark-recapture data collected over 14 years and longitudinal seroprevalence data from 2010 to 2013. The intermittent observation of DOBV before 2010 can be interpreted as repeated stochastic fadeouts after multiple introductions of infectious rodents migrating from neighboring areas. We estimated that only 20% of introductions in a naïve host population results in sustained transmission after two years, despite an effective reproduction number well above the epidemic threshold (mean 4.5, 95% credible intervals, CI: 0.65-15.8). Following the 2010 outbreak, DOBV has become endemic in the study area, but we predict a constant probability of about 4.7% per year that infection dies out, following large population drops in winter. In the absence of stochastic fadeout, viral prevalence is predicted to continue its growth to an oscillating equilibrium around a value of 24% (95% CI: 3-57%). We presented an example of invasion dynamics of a zoonotic virus where stochastic fadeout have played a major role and may induce future extinction of the endemic infection. This article is protected by copyright. All rights reserved.

  3. A population-level model from the microscopic dynamics in Escherichia coli chemotaxis via Langevin approximation

    Institute of Scientific and Technical Information of China (English)

    He Zhuo-Ran; Wu Tai-Lin; Ouyang Qi; Tu Yu-Hai

    2012-01-01

    Recent extensive studies of Escherichia coli (E.coli) chemotaxis have achieved a deep understanding of its microscopic control dynamics.As a result,various quantitatively predictive models have been developed to describe the chemotactic behavior of E.coli motion.However,a population-level partial differential equation (PDE) that rationally incorporates such microscopic dynamics is still insufficient.Apart from the traditional Keller-Segel (K-S) equation,many existing population-level models developed from the microscopic dynamics are integro-PDEs.The difficulty comes mainly from cell tumbles which yield a velocity jumping process.Here,we propose a Langevin approximation method that avoids such a difficulty without appreciable loss of precision.The resulting model not only quantitatively reproduces the results of pathway-based single-cell simulators,but also provides new inside information on the mechanism of E.coli chemotaxis.Our study demonstrates a possible alternative in establishing a simple population-level model that allows for the complex microscopic mechanisms in bacterial chemotaxis.

  4. Endogenous Population Dynamics and Economic Growth with Free Trade between Countries

    Directory of Open Access Journals (Sweden)

    Wei-Bin Zhang

    2016-05-01

    Full Text Available This paper builds a model to deal with dynamic interdependence between different countries' birth rates, mortality rates, populations, wealth accumulation, and time distributions between working, leisure and children caring. The model shows the role of human capital, technological and preference changes on national differences in birth rates, mortality rates, time distributions, population change, and wealth accumulation. The economic mechanisms of wealth accumulation, production and trade are based the Solow growth model and the Oniki-Uzawa trade model. We use the utility function proposed by Zhang to describe the behavior of households. We model national and gender differences in human capital, propensity to have children, propensity to use leisure time, and children caring efficiency. We describe the dynamics of global economic growth, trade patterns, national differences in wealth, income, birth rates, mortality rates, and populations with differential equations. We simulate the model to show the motion of the system and identify the existence of equilibrium point. We also examine the effects of changes in the propensity to have children, the propensity to save, woman's propensity to use leisure, woman's human capital, and woman's emotional involvement in children caring on the dynamics of the global and national economies.

  5. Variation in the local population dynamics of the short-lived Opuntia macrorhiza (Cactaceae).

    Science.gov (United States)

    Haridas, C V; Keeler, Kathleen H; Tenhumberg, Brigitte

    2015-03-01

    Spatiotemporal variation in demographic rates can have profound effects for population persistence, especially for dispersal-limited species living in fragmented landscapes. Long-term studies of plants in such habitats help with understanding the impacts of fragmentation on population persistence but such studies are rare. In this work, we reanalyzed demographic data from seven years of the short-lived cactus Opuntia macrorhiza var. macrorhiza at five plots in Boulder, Colorado. Previous work combining data from all years and all plots predicted a stable population (deterministic log lamda approximately 0). This approach assumed that all five plots were part of a single population. Since the plots were located in a suburban-agricultural interface separated by highways, grazing lands, and other barriers, and O. macrorhiza is likely dispersal limited, we analyzed the dynamics of each plot separately using stochastic matrix models assuming each plot represented a separate population. We found that the stochastic population growth rate log lamdaS varied widely between populations (log lamdaS = 0.1497, 0.0774, -0.0230, -0.2576, -0.4989). The three populations with the highest growth rates were located close together in space, while the two most isolated populations had the lowest growth rates suggesting that dispersal between populations is critical for the population viability of O. macrorhiza. With one exception, both our prospective (stochastic elasticity) and retrospective (stochastic life table response experiments) analysis suggested that means of stasis and growth, especially of smaller plants, were most important for population growth rate. This is surprising because recruitment is typically the most important vital rate in a short-lived species such as O. macrorhiza. We found that elasticity to the variance was mostly negligible, suggesting that O. macrorhiza populations are buffered against large temporal variation. Finally, single-year elasticities to means

  6. Modeling the impacts of hunting on the population dynamics of red howler monkeys (Alouatta seniculus)

    Science.gov (United States)

    Wiederholt, Ruscena; Fernandez-Duque, Eduardo; Diefenbach, Duane R.; Rudran, Rasanayagam

    2010-01-01

    Overexploitation of wildlife populations occurs across the humid tropics and is a significant threat to the long-term survival of large-bodied primates. To investigate the impacts of hunting on primates and ways to mitigate them, we developed a spatially explicit, individual-based model for a landscape that included hunted and un-hunted areas. We used the large-bodied neotropical red howler monkey (Alouatta seniculus) as our case study species because its life history characteristics make it vulnerable to hunting. We modeled the influence of different rates of harvest and proportions of landscape dedicated to un-hunted reserves on population persistence, population size, social dynamics, and hunting yields of red howler monkeys. In most scenarios, the un-hunted populations maintained a constant density regardless of hunting pressure elsewhere, and allowed the overall population to persist. Therefore, the overall population was quite resilient to extinction; only in scenarios without any un-hunted areas did the population go extinct. However, the total and hunted populations did experience large declines over 100 years under moderate and high hunting pressure. In addition, when reserve area decreased, population losses and losses per unit area increased disproportionately. Furthermore, hunting disrupted the social structure of troops. The number of male turnovers and infanticides increased in hunted populations, while birth rates decreased and exacerbated population losses due to hunting. Finally, our results indicated that when more than 55% of the landscape was harvested at high (30%) rates, hunting yields, as measured by kilograms of biomass, were less than those obtained from moderate harvest rates. Additionally, hunting yields, expressed as the number of individuals hunted/year/km2, increased in proximity to un-hunted areas, and suggested that dispersal from un-hunted areas may have contributed to hunting sustainability. These results indicate that un

  7. Density-dependent population dynamics in larvae of the dragonfly Pachydiplax longipennis: a field experiment.

    Science.gov (United States)

    Van Buskirk, J

    1987-05-01

    Several features of dragonfly population biology suggest that population regulation occurs in the larval stage. This study was designed to determine if density-dependent interactions among larval odonates can affect survival, growth and emergence. First-instar larvae of the dragonfly Pachydiplax longipennis were raised in outdoor experimental ponds at initial densities of 38, 152, and 608 larvae · m(-2), under two levels of food availability. Food availability was supplemented in half the pools by volumetric addition of zooplankton every other day. Pools in the low food treatment did not receive the zooplankton supplement.There was a strong negative effect of density on the mean growth rate of survivors, which included both emerging tenerals and individuals overwintering in the larval stage. A higher proportion emerged from low density than high density pools. Metamorphs from high density populations were smaller and emerged slightly later than those from low density, but the absolute number of metamorphs did not differ significantly among density treatments. Food supplementation significantly increased the proportion of overwintering larvae. There were no significant food-by-density interactions, indicating that food and density acted independently on larval population dynamics. Density-dependent mechanisms can clearly contribute to odonate population regulation, especially by controlling the number of larvae which emerge and the average age at reproduction. Population-level responses to density may be a result of interference among larvae.

  8. Reproduction and Population Dynamics as Biotypic Markers of Russian Wheat Aphid Diuraphis noxia (Kurdjumov).

    Science.gov (United States)

    Ngenya, Watson; Malinga, Joyce; Tabu, Isaiah; Masinde, Emily

    2016-04-02

    Russian wheat aphid Diuraphis noxia (Kurdjumov) is widely established in wheat-growing countries where it causes significant economic losses. The development and use of Russian wheat aphid (RWA)-resistant wheat varieties has been constrained by the variation in resident RWA populations and the evolution of virulent biotypes. An experiment was set up at the Kenya Agricultural and Livestock Research Organization (KALRO), Njoro, to characterize RWA populations based on phenotypic characteristics of reproduction, development and population dynamics. RWA populations from the regions of Eldoret, Mau Narok and Njoro were used in the study. A factorial experiment was set up in randomized complete block design replicated eleven times. A single day-old nymph was placed on a new, fully-open leaf in a 0.5 cm-diameter clear plastic straw leaf cage and observed daily for its entire lifetime. The results showed that there were variations in aphid lifespan, reproductive longevity and aphid fecundity between populations, indicating that the phenotypic markers used to determine biotypes were good enough to show distinct biotypes among populations of the RWA in Kenya. Further, the study concluded that the use of phenotypic life and reproductive markers was a valid way of characterizing biotypes of RWA worldwide.

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

    Science.gov (United States)

    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.

  10. Reproduction and Population Dynamics as Biotypic Markers of Russian Wheat Aphid Diuraphis noxia (Kurdjumov

    Directory of Open Access Journals (Sweden)

    Watson Ngenya

    2016-04-01

    Full Text Available Russian wheat aphid Diuraphis noxia (Kurdjumov is widely established in wheat-growing countries where it causes significant economic losses. The development and use of Russian wheat aphid (RWA-resistant wheat varieties has been constrained by the variation in resident RWA populations and the evolution of virulent biotypes. An experiment was set up at the Kenya Agricultural and Livestock Research Organization (KALRO, Njoro, to characterize RWA populations based on phenotypic characteristics of reproduction, development and population dynamics. RWA populations from the regions of Eldoret, Mau Narok and Njoro were used in the study. A factorial experiment was set up in randomized complete block design replicated eleven times. A single day-old nymph was placed on a new, fully-open leaf in a 0.5 cm-diameter clear plastic straw leaf cage and observed daily for its entire lifetime. The results showed that there were variations in aphid lifespan, reproductive longevity and aphid fecundity between populations, indicating that the phenotypic markers used to determine biotypes were good enough to show distinct biotypes among populations of the RWA in Kenya. Further, the study concluded that the use of phenotypic life and reproductive markers was a valid way of characterizing biotypes of RWA worldwide.

  11. The Effects of Rainfall on the Population Dynamics of an Endangered Aquatic Plant, Schoenoplectus gemmifer (Cyperaceae).

    Science.gov (United States)

    Kitamura, Koshi; Kakishima, Satoshi; Uehara, Takashi; Morita, Satoru; Tainaka, Kei-Ichi; Yoshimura, Jin

    2016-01-01

    The conservation of aquatic plants in river ecosystems should consider the wash-out (away) problem resulting from severe rainfall. The aquatic plant Schoenoplectus gemmifer is an endangered species endemic to Japan. Our previous study reported that the population size of S. gemmifer in Hamamatsu city, Japan, had decreased by one-tenth because many individuals had been washed out by a series of heavy rains in 2004. However, there is insufficient information on the ecological nature of this endangered aquatic plant for adequate conservation. In this paper, we report the population dynamics of one population in Hamamatsu city from 2004 to 2012 in relation to rainfall. We surveyed the number and growing location of all living individuals in the population 300 times during the study period. To examine the temporal changes of individual plants, we also counted the number of culms for 38 individuals in four observations among 300 records. Decreases and increases in the population size of this plant were associated with washing out and the settlement of gemmae (vegetative propagation), respectively. The major cause of the reduction in the population size was an increase in the number of washed-out individuals and not the decreased settlement of gemmae. The wash-out rates for small and large individuals were not significantly different. Small individuals having a stream form with linear leaves resisted flooding, and large individuals were often partially torn off by flooding events. Modification of river basins to reduce the flow velocity may be effective for the conservation of S. gemmifer.

  12. Algal Bloom in Aquatic Ecosystems-an Overview

    OpenAIRE

    M. Ghorbani; S.A. Mirbagheri; A. H. Hasani; S. M. Monavari; J.Nouri

    2014-01-01

    Algae play an important role in all aquatic ecosystems by providing all living organisms of water bodies with preliminary nutrients and energy required. However, abnormal and excessive algal growth so-called algal bloom would be detrimental as much. Given the importance of algae in aquatic environment as well as their sensitivity to environmental changes, algal measurements are of key components of water quality monitoring programs. The algal blooms could include a variety of adverse impacts...

  13. Effects of growth curve plasticity on size-structured population dynamics

    DEFF Research Database (Denmark)

    Zhang, Lai; Lin, Zhigui; Pedersen, Michael

    2011-01-01

    The physiological-structured population models assume that a fixed fraction of energy intake is utilized for individual growth and maintenance while the remaining for adult fertility. The assumption results in two concerns: energy loss for juveniles and a reproduction dilemma for adults. The dile......The physiological-structured population models assume that a fixed fraction of energy intake is utilized for individual growth and maintenance while the remaining for adult fertility. The assumption results in two concerns: energy loss for juveniles and a reproduction dilemma for adults...... and reproduction. Moreover, the portion of surplus energy for reproduction is size-dependent and increases monotonically with size. Using the newly developed parameter continuation, we demonstrate their disparate effects on population dynamics. Results show that the size-dependent mechanism of energy allocation...

  14. Implications of interacting microscale habitat heterogeneity and disturbance events on Folsomia candida (Collembola) population dynamics

    DEFF Research Database (Denmark)

    Meli, Mattia; Palmqvist, Annemette; Forbes, Valery E

    2014-01-01

    human activities that may cause habitat destruction, we focused on agricultural practices. Soil organisms living in a cultivated field are subjected to habitat loss and fragmentation as well as disturbance events generated by the application of agrochemicals and related activities. In addition......The authors implemented a fractal algorithm in a spatially explicit individual-based model, in order to generate landscapes with different microscale patterns of habitat fragmentation and disturbance events, and studied their effects on population dynamics of the collembolan Folsomia candida. Among......, they are exposed to natural stressors, which might influence the effects of chemicals on populations. We designed simulation experiments that incorporate these 3 factors, and investigated their effects on populations of F. candida, in presence or absence of behavioural avoidance of contaminated habitat. Simulation...

  15. [Population of entophytic bacteria in maize roots and its dynamic analysis].

    Science.gov (United States)

    Gao, Zenggui; Zhuang, Jinghua; Chen, Jie; Liu, Xian; Tang, Shuge

    2004-08-01

    In 2001-2002, 14 maize cultivars in Liaoning Province were used for the analysis of their entophytic bacteria population. The entophytic bacteria strains with a higher frequency in maize roots were Bacillus spp., Enterobacter spp., Serratia spp., Pseudomonas spp., Xanthomonas spp., Clavibacter spp., Bacillus spp., Enterobacter spp. and Serratia spp. Comparatively, Bacillus spp. was the most prevalent entophytic bacterium, including 8 species, B. subtilis, B. megaterium, B. cereus, B. licheniformis, B. anthracis, B. mycoides, B. pumilus and B. circulans, and with an average isolation frequency of 75.5% at seedling stage and 77.6% at adult stage. There existed significant differences in the population and dynamics of endophytic bacteria among maize cultivars and growth periods, and a significant correlation was found between maize genetic background and entophytic bacteria population.

  16. Single-cell protein dynamics reproduce universal fluctuations in cell populations

    CERN Document Server

    Brenner, Naama; Rotella, James S; Salman, Hanna

    2015-01-01

    Protein fluctuations in cell populations have recently been shown to exhibit a universal distribution shape under a broad range of biological realizations. Here, measuring protein content in individual bacteria continuously over ~70 generations, we show that single-cell trajectories fluctuate around their average with the same distribution shape as the population, i.e. their relative fluctuations are ergodic. Analysis of these temporal trajectories reveals that one effective random variable, sampled once each cell cycle, suffices to reconstruct the distribution from the trajectory. This in turn implies that cellular microscopic processes are strongly buffered and population-level protein distributions are insensitive to details of the intracellular dynamics. Probing them thus requires searching for novel universality-breaking experimental perturbations.

  17. Combining a weed traits database with a population dynamics model predicts shifts in weed communities

    DEFF Research Database (Denmark)

    Storkey, Jonathan; Holst, Niels; Bøjer, Ole Mission;

    2015-01-01

    A functional approach to predicting shifts in weed floras in response to management or environmental change requires the combination of data on weed traits with analytical frameworks that capture the filtering effect of selection pressures on traits. A weed traits database (WTDB) was designed......, populated and analysed, initially using data for 19 common European weeds, to begin to consolidate trait data in a single repository. The initial choice of traits was driven by the requirements of empirical models of weed population dynamics to identify correlations between traits and model parameters....... These relationships were used to build a generic model, operating at the level of functional traits, to simulate the impact of increasing herbicide and fertiliser use on virtual weeds along gradients of seed weight and maximum height. The model generated ‘fitness contours’ (defined as population growth rates) within...

  18. Modeling the influence of polls on elections: a population dynamics approach

    Energy Technology Data Exchange (ETDEWEB)

    Hyman, James M [Los Alamos National Laboratory; Restrepo, Juan M [UNIV OF ARIZONA; Rael, Rosalyn C [UNIV OF ARIZONA

    2009-01-01

    We propose a population dynamics model for quantifying the effects of polling data on the outcome of multi-party elections decided by a majority-rule voting process. We divide the population into two groups: committed voters impervious to polling data, and susceptible voters whose decision to vote is influenced by data, depending on its reliability. This population-based approach to modeling the process sidesteps the problem of upscaling models based upon the choices made by individuals. We find releasing poll data is not advantageous to leading candidates, but it can be exploited by those closely trailing. The analysis identifies the particular type of voting impetus at play in different stages of an election and could help strategists optimize their influence on susceptible voters.

  19. Cell mass and cell cycle dynamics of an asynchronous budding yeast population

    DEFF Research Database (Denmark)

    Lencastre Fernandes, Rita; Carlquist, Magnus; Lundin, Luisa

    2013-01-01

    consumption observed during batch cultivation. The good agreement between the proposed multi-scale model (a population balance model [PBM] coupled to an unstructured model) and experimental data (both the overall physiology and cell size and cell cycle distributions) indicates that a mechanistic model...... of model predictions for cell property distributions against experimental data is scarce. This study focuses on the experimental and mathematical description of the dynamics of cell size and cell cycle position distributions, of a population of Saccharomyces cerevisiae, in response to the substrate......Despite traditionally regarded as identical, cells in a microbial cultivation present a distribution of phenotypic traits, forming a heterogeneous cell population. Moreover, the degree of heterogeneity is notably enhanced by changes in micro-environmental conditions. A major development...

  20. Population Dynamics of Heterodera glycines and Soybean Response in Soils Treated with Selected Nematicides and Herbicides.

    Science.gov (United States)

    Schmitt, D P; Corbin, F T; Nelson, L A

    1983-07-01

    Two field experiments were conducted in two locations to determine the effects of the nematicides aldicarb, phenamiphos, and ethoprop and/or the herbicides alachlor, linuron, or metribuzin on the population dynamics of Heterodera glycines and soybean growth and yield. Population densities of H. glycines were greater, at some time during the growing season, in several treatments with alachlor alone and in combination with nematicides. Numbers of H. glycines at harvest were greater in plots treated with aldicarb than in those treated with ethoprop or phenamiphos. The numbers in aldicarb treated plots were generally reduced when plots also received a herbicide. Soybean yields were negatively correlated with numbers of H. glycines eggs and juveniles in early to mid season but positively correlated with late season population densities.

  1. Coherence and population dynamics of chlorophyll excitations in FCP complex: Two-dimensional spectroscopy study

    CERN Document Server

    Butkus, Vytautas; Augulis, Ramūnas; Gall, Andrew; Büchel, Claudia; Robert, Bruno; Zigmantas, Donatas; Valkunas, Leonas; Abramavicius, Darius

    2015-01-01

    The energy transfer processes and coherent phenomena in the fucoxanthin-chlorophyll protein complex, which is responsible for the light harvesting function in marine algae diatoms, were investigated at 77 K by using two-dimensional electronic spectroscopy. Experiments performed on the femtosecond and picosecond timescales led to separation of spectral dynamics, witnessing evolutions of coherence and population states of the system in the spectral region of ${\\rm Q}_{y}$ transitions of chlorophylls $a$ and $c$. Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) $a$ and fucoxanthin intramolecular vibrations dominating over the first few picoseconds. Closer inspection of the spectral region of the ${\\rm Q}_{y}$ transition of Chl $c$ revealed previously not identified mutually non-interacting chlorophyll $c$ states participating in femtosecond or picosecond energy transfer to the Chl $a$ molecules. Consideration of separated coherent and incoherent dynamics allowed us to hypothesize the v...

  2. Coherence and population dynamics of chlorophyll excitations in FCP complex: Two-dimensional spectroscopy study.

    Science.gov (United States)

    Butkus, Vytautas; Gelzinis, Andrius; Augulis, Ramūnas; Gall, Andrew; Büchel, Claudia; Robert, Bruno; Zigmantas, Donatas; Valkunas, Leonas; Abramavicius, Darius

    2015-06-07

    Energy transfer processes and coherent phenomena in the fucoxanthin-chlorophyll protein complex, which is responsible for the light harvesting function in marine algae diatoms, were investigated at 77 K by using two-dimensional electronic spectroscopy. Experiments performed on femtosecond and picosecond timescales led to separation of spectral dynamics, witnessing evolutions of coherence and population states of the system in the spectral region of Qy transitions of chlorophylls a and c. Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) a and fucoxanthin intramolecular vibrations dominating over the first few picoseconds. Closer inspection of the spectral region of the Qy transition of Chl c revealed previously not identified, mutually non-interacting chlorophyll c states participating in femtosecond or picosecond energy transfer to the Chl a molecules. Consideration of separated coherent and incoherent dynamics allowed us to hypothesize the vibrations-assisted coherent energy transfer between Chl c and Chl a and the overall spatial arrangement of chlorophyll molecules.

  3. Development of a Dynamic Population Balance Plant Simulator for Mineral Processing Circuits

    Directory of Open Access Journals (Sweden)

    Fatemeh Khoshnam

    2015-06-01

    Full Text Available Operational variables of a mineral processing circuit are subjected to different variations. Steady-statesimulation of processes provides an estimate of their ideal stable performance whereas their dynamicsimulation predicts the effects of the variations on the processes or their subsequent processes. In thispaper, a dynamic simulator containing some of the major equipment of mineral processing circuits(i.e. ball mill, cone crusher, screen, hydrocyclone, mechanical flotation cell, tank leaching andconveyor belt was developed. The dynamic simulator of each mentioned unit was also developedaccording to population balance models with the help of MATLAB/Simulink environment and wasverified against the data from the literature. Comminution and separation sections were linked usingempirical models which correlate the separation and extraction kinetics to particle size. Applying thedeveloped simulator, the dynamic behavior of a grinding-leaching circuit was analyzed and the resultsshowed that such simulations are required for both designing and controlling the circuits.

  4. Evolutionary game theory for physical and biological scientists. I. Training and validating population dynamics equations.

    Science.gov (United States)

    Liao, David; Tlsty, Thea D

    2014-08-06

    Failure to understand evolutionary dynamics has been hypothesized as limiting our ability to control biological systems. An increasing awareness of similarities between macroscopic ecosystems and cellular tissues has inspired optimism that game theory will provide insights into the progression and control of cancer. To realize this potential, the ability to compare game theoretic models and experimental measurements of population dynamics should be broadly disseminated. In this tutorial, we present an analysis method that can be used to train parameters in game theoretic dynamics equations, used to validate the resulting equations, and used to make predictions to challenge these equations and to design treatment strategies. The data analysis techniques in this tutorial are adapted from the analysis of reaction kinetics using the method of initial rates taught in undergraduate general chemistry courses. Reliance on computer programming is avoided to encourage the adoption of these methods as routine bench activities.

  5. Line Emission from Radiation-Pressurized HII Region II: Dynamics and Population Synthesis

    CERN Document Server

    Verdolini, Silvia; Krumholz, Mark R; Matzner, Christopher D; Tielens, Alexander G G M

    2013-01-01

    Optical and infrared emission lines from HII regions are an important diagnostic used to study galaxies, but interpretation of these lines requires significant modeling of both the internal structure and dynamical evolution of the emitting regions. Most of the models in common use today assume that HII region dynamics are dominated by the expansion of stellar wind bubbles, and have neglected the contribution of radiation pressure to the dynamics, and in some cases also to the internal structure. However, recent observations of nearby galaxies suggest that neither assumption is justified, motivating us to revisit the question of how HII region line emission depends on the physics of winds and radiation pressure. In a companion paper we construct models of single HII regions including and excluding radiation pressure and winds, and in this paper we describe a population synthesis code that uses these models to simulate galactic collections of HII regions with varying physical parameters. We show that the choice...

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

    Science.gov (United States)

    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.

  7. Dynamic Heterogeneity of the Heart Valve Interstitial Cell Population in Mitral Valve Health and Disease

    Directory of Open Access Journals (Sweden)

    Tori E. Horne

    2015-08-01

    Full Text Available The heart valve interstitial cell (VIC population is dynamic and thought to mediate lay down and maintenance of the tri-laminar extracellular matrix (ECM structure within the developing and mature valve throughout life. Disturbances in the contribution and distribution of valve ECM components are detrimental to biomechanical function and associated with disease. This pathological process is associated with activation of resident VICs that in the absence of disease reside as quiescent cells. While these paradigms have been long standing, characterization of this abundant and ever-changing valve cell population is incomplete. Here we examine the expression pattern of Smooth muscle α-actin, Periostin, Twist1 and Vimentin in cultured VICs, heart valves from healthy embryonic, postnatal and adult mice, as well as mature valves from human patients and established mouse models of disease. We show that the VIC population is highly heterogeneous and phenotypes are dependent on age, species, location, and disease state. Furthermore, we identify phenotypic diversity across common models of mitral valve disease. These studies significantly contribute to characterizing the VIC population in health and disease and provide insights into the cellular dynamics that maintain valve structure in healthy adults and mediate pathologic remodeling in disease states.

  8. Approximate Inference for Time-Varying Interactions and Macroscopic Dynamics of Neural Populations

    Science.gov (United States)

    Obermayer, Klaus

    2017-01-01

    The models in statistical physics such as an Ising model offer a convenient way to characterize stationary activity of neural populations. Such stationary activity of neurons may be expected for recordings from in vitro slices or anesthetized animals. However, modeling activity of cortical circuitries of awake animals has been more challenging because both spike-rates and interactions can change according to sensory stimulation, behavior, or an internal state of the brain. Previous approaches modeling the dynamics of neural interactions suffer from computational cost; therefore, its application was limited to only a dozen neurons. Here by introducing multiple analytic approximation methods to a state-space model of neural population activity, we make it possible to estimate dynamic pairwise interactions of up to 60 neurons. More specifically, we applied the pseudolikelihood approximation to the state-space model, and combined it with the Bethe or TAP mean-field approximation to make the sequential Bayesian estimation of the model parameters possible. The large-scale analysis allows us to investigate dynamics of macroscopic properties of neural circuitries underlying stimulus processing and behavior. We show that the model accurately estimates dynamics of network properties such as sparseness, entropy, and heat capacity by simulated data, and demonstrate utilities of these measures by analyzing activity of monkey V4 neurons as well as a simulated balanced network of spiking neurons. PMID:28095421

  9. Long-term population dynamics of a managed burrowing owl colony

    Science.gov (United States)

    Barclay, John H.; Korfanta, Nicole M.; Kauffman, Matthew J.

    2011-01-01

    We analyzed the population dynamics of a burrowing owl (Athene cunicularia) colony at Mineta San Jose International Airport in San Jose, California, USA from 1990-2007. This colony was managed by using artificial burrows to reduce the occurrence of nesting owls along runways and within major airport improvement projects during the study period. We estimated annual reproduction in natural and artificial burrows and age-specific survival rates with mark-recapture techniques, and we estimated the relative contribution of these vital rates to population dynamics using a life table response experiment. The breeding colony showed 2 distinct periods of change: high population growth from 7 nesting pairs in 1991 to 40 pairs in 2002 and population decline to 17 pairs in 2007. Reproduction was highly variable: annual nesting success (pairs that raised =1 young) averaged 79% and ranged from 36% to 100%, whereas fecundity averaged 3.36 juveniles/pair and ranged from 1.43 juveniles/pair to 4.54 juveniles/pair. We estimated annual adult survival at 0.710 during the period of colony increase from 1996 to 2001 and 0.465 during decline from 2002 to 2007, but there was no change in annual survival of juveniles between the 2 time periods. Long-term population growth rate (lambda) estimated from average vital rates was lambdaa=1.072 with lambdai=1.288 during colony increase and lambdad=0.921 (DELTA lambda=0.368) during decline. A life table response experiment showed that change in adult survival rate during increasing and declining phases explained more than twice the variation in growth rate than other vital rates. Our findings suggest that management and conservation of declining burrowing owl populations should address factors that influence adult survival.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  12. Oenological prefermentation practices strongly impact yeast population dynamics and alcoholic fermentation kinetics in Chardonnay grape must.

    Science.gov (United States)

    Albertin, Warren; Miot-Sertier, Cécile; Bely, Marina; Marullo, Philippe; Coulon, Joana; Moine, Virginie; Colonna-Ceccaldi, Benoit; Masneuf-Pomarede, Isabelle

    2014-05-16

    Yeast species of Hanseniaspora and Candida genus are predominant during the early stages of winemaking, while species of Metschnikowia, Pichia, Zygoascus, Issatchenkia, Torulaspora and other genera are present at lower population levels. The impact of common oenological practices on yeast dynamics during the prefermentative stage and the early stage of alcoholic fermentation (AF) remains elusive. In this work, the effect of four prefermentative oenological practices (clarification degree, temperature, sulphite and starter yeast addition) on yeast dynamics was evaluated in a Chardonnay grape must. The growth curves of four genus or species, namely Saccharomyces spp., Hanseniaspora spp., Candida zemplinina and Torulaspora delbrueckii, were followed by quantitative PCR. The fermentation kinetics were also recorded, as well as the production of acetic acid. Variance analysis allowed determining the effect of each practice and their interaction factors, as well as their relative importance on yeast dynamics and fermentation kinetics. Our experimental design showed that the population dynamics of the four species were differently impacted by the oenological practices, with some species being more sensitive than others to the clarification degree (C. zemplinina), sulphite addition (Saccharomyces spp.), starter yeast inoculation (Hanseniaspora spp.) or prefermentation temperature (T. delbrueckii). Significant interaction effects between practices were revealed, highlighting the interest of experimental design allowing interaction analysis, as some factors may buffer the effect of other ones. Hanseniaspora genus showed atypical behaviour: growth dynamics showed a decrease during AF that we interpreted as early cellular lysis. In conclusion, this study provides new insights on the impact of common oenological practices on the dynamics of non-Saccharomyces yeast that will be useful for a better management of mixed fermentation between S. cerevisiae and non

  13. Modeling population dynamics of solitary bees in relation to habitat quality

    Directory of Open Access Journals (Sweden)

    K. Ulbrich

    2001-09-01

    Full Text Available To understand associations between habitat, individual behaviour, and population development of solitary bees we developed an individual-based model. This model is based on field observations of Osmia rufa (L (Apoideae: Megachilidae and describes population dynamics of solitary bees. Model rules are focused on maternal investment, in particular on the female’s individual decisions about sex and size of progeny. In the present paper, we address the effect of habitat quality on population size and sex ratio. We examine how food availability and the risk of parasitism influence long-term population development. It can be shown how population properties result from individual maternal investment which is described as a functional response to fluctuations of environmental conditions. We found that habitat quality can be expressed in terms of cell construction time. This interface factor influences the rate of open cell parasitism as the risk for a brood cell to be parasitized is positively correlated with the time of its construction. Under conditions of scarce food and under resulting long provision times even low parasitism rates lead to a high extinction risk of the population, whereas in rich habitats probabilities of extinction are low even for high rates of parasitism. For a given level of food and parasitism there is an optimum time for cell construction which minimizes the extinction risk of the population. Model results demonstrate that under fluctuating environmental conditions, decreasing habitat quality leads to a decrease in population size but also to rapid shifts in sex ratio.

  14. The habits of highly effective phages: population dynamics as a framework for identifying therapeutic phages

    Directory of Open Access Journals (Sweden)

    James J Bull

    2014-11-01

    Full Text Available The use of bacteriophages as antibacterial agents is being actively researched on a global scale. Typically, the phages used are isolated from the wild by plating on the bacteria of interest, and a far larger set of candidate phages is often available than can be used in any application. When an excess of phages is available, how should the best phages be identified? Here we consider phage-bacterial population dynamics as a basis for evaluating and predicting phage success. A central question is whether the innate dynamical properties of phages are the determinants of success, or instead, whether extrinsic, indirect effects can be responsible. We address the dynamical perspective, motivated in part by the absence of dynamics in previously suggested principles of phage therapy. Current mathematical models of bacterial-phage dynamics do not capture the realities of in vivo dynamics, nor is this likely to change, but they do give insight to qualitative properties that may be generalizable. In particular, phage adsorption rate may be critical to treatment success, so understanding the effects of the in vivo environment on host availability may allow prediction of useful phages prior to in vivo experimentation. Principles for predicting efficacy may be derived by developing a greater understanding of the in vivo system, or such principles could be determined empirically by comparing phages with known differences in their dynamic properties. The comparative approach promises to be a powerful method of discovering the key to phage success. We offer five recommendations for future study: (i compare phages differing in treatment efficacy to identify the phage properties associated with success, (ii assay dynamics in vivo, (iii understand mechanisms of bacterial escape from phages, (iv test phages in model infections that are relevant to the intended clinical applications, and (v develop new classes of models for phage growth in spatially heterogeneous

  15. Algal blooms and Membrane Based Desalination Technology

    NARCIS (Netherlands)

    Villacorte, L.O.

    2014-01-01

    Seawater desalination is rapidly growing in terms of installed capacity (~80 million m3/day in 2013), plant size and global application. An emerging threat to this technology is the seasonal proliferation of microscopic algae in seawater known as algal blooms. Such blooms have caused operational pro

  16. Resolving Mixed Algal Species in Hyperspectral Images

    Directory of Open Access Journals (Sweden)

    Mehrube Mehrubeoglu

    2013-12-01

    Full Text Available We investigated a lab-based hyperspectral imaging system’s response from pure (single and mixed (two algal cultures containing known algae types and volumetric combinations to characterize the system’s performance. The spectral response to volumetric changes in single and combinations of algal mixtures with known ratios were tested. Constrained linear spectral unmixing was applied to extract the algal content of the mixtures based on abundances that produced the lowest root mean square error. Percent prediction error was computed as the difference between actual percent volumetric content and abundances at minimum RMS error. Best prediction errors were computed as 0.4%, 0.4% and 6.3% for the mixed spectra from three independent experiments. The worst prediction errors were found as 5.6%, 5.4% and 13.4% for the same order of experiments. Additionally, Beer-Lambert’s law was utilized to relate transmittance to different volumes of pure algal suspensions demonstrating linear logarithmic trends for optical property measurements.

  17. A study of algal biomass potential in selected Canadian regions.

    Energy Technology Data Exchange (ETDEWEB)

    Passell, Howard David; Roach, Jesse Dillon; Klise, Geoffrey T.

    2011-11-01

    A dynamic assessment model has been developed for evaluating the potential algal biomass and extracted biocrude productivity and costs, using nutrient and water resources available from waste streams in four regions of Canada (western British Columbia, Alberta oil fields, southern Ontario, and Nova Scotia). The purpose of this model is to help identify optimal locations in Canada for algae cultivation and biofuel production. The model uses spatially referenced data across the four regions for nitrogen and phosphorous loads in municipal wastewaters, and CO{sub 2} in exhaust streams from a variety of large industrial sources. Other data inputs include land cover, and solar insolation. Model users can develop estimates of resource potential by manipulating model assumptions in a graphic user interface, and updated results are viewed in real time. Resource potential by location can be viewed in terms of biomass production potential, potential CO{sub 2} fixed, biocrude production potential, and area required. The cost of producing algal biomass can be estimated using an approximation of the distance to move CO{sub 2} and water to the desired land parcel and an estimation of capital and operating costs for a theoretical open pond facility. Preliminary results suggest that in most cases, the CO{sub 2} resource is plentiful compared to other necessary nutrients (especially nitrogen), and that siting and prospects for successful large-scale algae cultivation efforts in Canada will be driven by availability of those other nutrients and the efficiency with which they can be used and re-used. Cost curves based on optimal possible siting of an open pond system are shown. The cost of energy for maintaining optimal growth temperatures is not considered in this effort, and additional research in this area, which has not been well studied at these latitudes, will be important in refining the costs of algal biomass production. The model will be used by NRC-IMB Canada to identify

  18. Impact of unintentional selective harvesting on the population dynamics of red grouse.

    Science.gov (United States)

    Bunnefeld, Nils; Reuman, Daniel C; Baines, David; Milner-Gulland, E J

    2011-11-01

    1. The effect of selective exploitation of certain age, stage or sex classes (e.g., trophy hunting) on population dynamics is relatively well studied in fisheries and sexually dimorphic mammals. 2. Harvesting of terrestrial species with no morphological differences visible between the different age and sex classes (monomorphic species) is usually assumed to be nonselective because monomorphicity makes intentionally selective harvesting pointless and impractical. But harvesting of the red grouse (Lagopus lagopus scoticus), a monomorphic species, was recently shown to be unintentionally selective. This study uses a sex- and age-specific model to explore the previously unresearched effects of unintentional harvesting selectivity. 3. We examine the effects of selectivity on red grouse dynamics by considering models with and without selectivity. Our models include territoriality and parasitism, two mechanisms known to be important for grouse dynamics. 4. We show that the unintentional selectivity of harvesting that occurs in red grouse decreases population yield compared with unselective harvesting at high harvest rates. Selectivity also dramatically increases extinction risk at high harvest rates. 5. Selective harvesting strengthens the 3- to 13-year red grouse population cycle, suggesting that the selectivity of harvesting is a previously unappreciated factor contributing to the cycle. 6. The additional extinction risk introduced by harvesting selectivity provides a quantitative justification for typically implemented 20-40% harvest rates, which are below the maximum sustainable yield that could be taken, given the observed population growth rates of red grouse. 7. This study shows the possible broad importance of investigating in future research whether unintentionally selective harvesting occurs on other species.

  19. Sensitivity of Anopheles gambiae population dynamics to meteo-hydrological variability: a mechanistic approach

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    Gilioli Gianni

    2011-10-01

    Full Text Available Abstract Background Mechanistic models play an important role in many biological disciplines, and they can effectively contribute to evaluate the spatial-temporal evolution of mosquito populations, in the light of the increasing knowledge of the crucial driving role on vector dynamics played by meteo-climatic features as well as other physical-biological characteristics of the landscape. Methods In malaria eco-epidemiology landscape components (atmosphere, water bodies, land use interact with the epidemiological system (interacting populations of vector, human, and parasite. In the background of the eco-epidemiological approach, a mosquito population model is here proposed to evaluate the sensitivity of An. gambiae s.s. population to some peculiar thermal-pluviometric scenarios. The scenarios are obtained perturbing meteorological time series data referred to four Kenyan sites (Nairobi, Nyabondo, Kibwesi, and Malindi representing four different eco-epidemiological settings. Results Simulations highlight a strong dependence of mosquito population abundance on temperature variation with well-defined site-specific patterns. The upper extreme of thermal perturbation interval (+ 3°C gives rise to an increase in adult population abundance at Nairobi (+111% and Nyabondo (+61%, and a decrease at Kibwezi (-2% and Malindi (-36%. At the lower extreme perturbation (-3°C is observed a reduction in both immature and adult mosquito population in three sites (Nairobi -74%, Nyabondo -66%, Kibwezi -39%, and an increase in Malindi (+11%. A coherent non-linear pattern of population variation emerges. The maximum rate of variation is +30% population abundance for +1°C of temperature change, but also almost null and negative values are obtained. Mosquitoes are less sensitive to rainfall and both adults and immature populations display a positive quasi-linear response pattern to rainfall variation. Conclusions The non-linear temperature-dependent response is in

  20. Life-history and spatial determinants of somatic growth dynamics in Komodo dragon populations.

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    Rebecca J Laver

    Full Text Available Somatic growth patterns represent a major component of organismal fitness and may vary among sexes and populations due to genetic and environmental processes leading to profound differences in life-history and demography. This study considered the ontogenic, sex-specific and spatial dynamics of somatic growth patterns in ten populations of the world's largest lizard the Komodo dragon (Varanus komodoensis. The growth of 400 individual Komodo dragons was measured in a capture-mark-recapture study at ten sites on four islands in eastern Indonesia, from 2002 to 2010. Generalized Additive Mixed Models (GAMMs and information-theoretic methods were used to examine how growth rates varied with size, age and sex, and across and within islands in relation to site-specific prey availability, lizard population density and inbreeding coefficients. Growth trajectories differed significantly with size and between sexes, indicating different energy allocation tactics and overall costs associated with reproduction. This leads to disparities in maximum body sizes and longevity. Spatial variation in growth was strongly supported by a curvilinear density-dependent growth model with highest growth rates occurring at intermediate population densities. Sex-specific trade-offs in growth underpin key differences in Komodo dragon life-history including evidence for high costs of reproduction in females. Further, inverse density-dependent growth may have profound effects on individual and population level processes that influence the demography of this species.

  1. Yeast Population Dynamics during the Fermentation and Biological Aging of Sherry Wines

    Science.gov (United States)

    Esteve-Zarzoso, B.; Peris-Torán, M. J.; García-Maiquez, E.; Uruburu, F.; Querol, A.

    2001-01-01

    Molecular and physiological analyses were used to study the evolution of the yeast population, from alcoholic fermentation to biological aging in the process of “fino” sherry wine making. The four races of “flor” Saccharomyces cerevisiae (beticus, cheresiensis, montuliensis, and rouxii) exhibited identical restriction patterns for the region spanning the internal transcribed spacers 1 and 2 (ITS-1 and ITS-2) and the 5.8S rRNA gene, but this pattern was different, from those exhibited by non-flor S. cerevisiae strains. This flor-specific pattern was detected only after wines were fortified, never during alcoholic fermentation, and all the strains isolated from the velum exhibited the typical flor yeast pattern. By restriction fragment length polymorphism of mitochondrial DNA and karyotyping, we showed that (i) the native strain is better adapted to fermentation conditions than commercial strains; (ii) two different populations of S. cerevisiae strains are involved in the process of elaboration, of fino sherry wine, one of which is responsible for must fermentation and the other, for wine aging; and (iii) one strain was dominant in the flor population integrating the velum from sherry wines produced in González Byass wineries, although other authors have described a succession of races of flor S. cerevisiae during wine aging. Analyzing all these results together, we conclude that yeast population dynamics during biological aging is a complex phenomenon and differences between yeast populations from different wineries can be observed. PMID:11319081

  2. Sexual dimorphism, population dynamics and some aspects of life history of Echiniscus mauccii (Tardigrada; Heterotardigrada

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    Frank A. ROMANO III

    2007-09-01

    Full Text Available A fifteen month study (December 2002 though February 2004 of a meiofaunal community living in moss and lichen from a Pecan tree on the campus of Jacksonville State University reports 9,791 microinvertebrates. Echiniscus mauccii was the most prevalent tardigrade species (1,329 specimens and was chosen to determine population dynamics and some aspects of their life histories. The average length of all the specimens (adults, juveniles, males, and females for each month was determined. A plot of all E. mauccii specimens was used to determine the following life stages of this species; juvenile, pre-reproductive, and reproductive. The studied population exhibited relatively constant population size and juvenile recruitment occurred year round with no increased reproduction during a season of the year. Thus, E. mauccii is an opportunistic breeder. Males of this species were found for the first time on a Laurasian land mass and females were found to be significantly larger than males. A protected Fisher's LSD test revealed a significant negative relationship between average adult length and the number of adults collected per month, but not between adult and juvenile lengths. As the population became more dense the average adult size decreased suggesting competition between at least the adults. Echiniscus mauccii is a sexually dimorphic animal that is iteroparous, breeds whenever conditions are appropriate, has a relatively constant population size, produces a small number of large eggs, and exhibits competition between adults. Thus, E. mauccii exhibits classic K-selected traits.

  3. Population dynamics of shrimps in littoral marine waters of the Mekong Delta, south of Viet Nam.

    Science.gov (United States)

    Dinh, T D; Moreau, J; Van, M V; Phuong, N T; Toan, V T

    2010-07-15

    The population dynamics of eight commercial species of shrimp (Haliporoides sibogae, Harpiosquilla harpax, Metapenaeus affinis, Metapenaeus brevicornis, Metapenaeus tenuipes, Parapenaeopsis cultrirostris, Parapenaeopsis gracillima and Parapenaeus maxilipedo) distributed in littoral marine zone of the Mekong Delta were investigated. Length-based stock assessment using FiSAT II software package was used to assess the growth and mortality parameters: Asymptotic size (L8), growth coefficient (K), total (Z) and natural (M) mortality, exploitation rate (E), recruitment pattern, current probability of capture and selectivity of fishing gears. Yield-per-recruit analyses were carried out showing different levels of the exploitation. Results showed that the maximum sustainable yield would be reached for an exploitation rate higher than the current one for each population. However, the size of first capture should be increased for every population. The findings indicated that the current exploitations of shrimp populations distributed in littoral marine zone of the Mekong Delta are under exploitation level for maximum sustainable yield; however, all the shrimp populations are subject to growth over-exploitation.

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

    Science.gov (United States)

    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.

  5. Population dynamics of American horseshoe crabs-historic climatic events and recent anthropogenic pressures

    Science.gov (United States)

    Faurby, S.; King, T.L.; Obst, M.; Hallerman, E.M.; Pertoldi, C.; Funch, P.

    2010-01-01

    Populations of the American horseshoe crab, Limulus polyphemus, have declined, but neither the causes nor the magnitude are fully understood. In order to evaluate historic demography, variation at 12 microsatellite DNA loci surveyed in 1218 L. polyphemus sampled from 28 localities was analysed with Bayesian coalescent-based methods. The analysis showed strong declines in population sizes throughout the species' distribution except in the geographically isolated southern-most population in Mexico, where a strong increase in population size was inferred. Analyses suggested that demographic changes in the core of the distribution occurred in association with the recolonization after the Ice Age and also by anthropogenic effects, such as the past overharvest of the species for fertilizer or the current use of the animals as bait for American eel (Anguilla rostrata) and whelk (Busycon spp.) fisheries. This study highlights the importance of considering both climatic changes and anthropogenic effects in efforts to understand population dynamics-a topic which is highly relevant in the ongoing assessments of the effects of climate change and overharvest. ?? 2010 Blackwell Publishing Ltd.

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

    Science.gov (United States)

    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.

  7. Algal toxins alter copepod feeding behavior.

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    Jiarong Hong

    Full Text Available Using digital holographic cinematography, we quantify and compare the feeding behavior of free-swimming copepods, Acartia tonsa, on nutritional prey (Storeatula major to that occurring during exposure to toxic and non-toxic strains of Karenia brevis and Karlodinium veneficum. These two harmful algal species produce polyketide toxins with different modes of action and potency. We distinguish between two different beating modes of the copepod's feeding appendages-a "sampling beating" that has short durations (<100 ms and involves little fluid entrainment and a longer duration "grazing beating" that persists up to 1200 ms and generates feeding currents. The durations of both beating modes have log-normal distributions. Without prey, A. tonsa only samples the environment at low frequency. Upon introduction of non-toxic food, it increases its sampling time moderately and the grazing period substantially. On mono algal diets for either of the toxic dinoflagellates, sampling time fraction is high but the grazing is very limited. A. tonsa demonstrates aversion to both toxic algal species. In mixtures of S. major and the neurotoxin producing K. brevis, sampling and grazing diminish rapidly, presumably due to neurological effects of consuming brevetoxins while trying to feed on S. major. In contrast, on mixtures of cytotoxin producing K. veneficum, both behavioral modes persist, indicating that intake of karlotoxins does not immediately inhibit the copepod's grazing behavior. These findings add critical insight into how these algal toxins may influence the copepod's feeding behavior, and suggest how some harmful algal species may alter top-down control exerted by grazers like copepods.

  8. Algal MIPs, high diversity and conserved motifs

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    Johanson Urban

    2011-04-01

    Full Text Available Abstract Background Major intrinsic proteins (MIPs also named aquaporins form channels facilitating the passive transport of water and other small polar molecules across membranes. MIPs are particularly abundant and diverse in terrestrial plants but little is known about their evolutionary history. In an attempt to investigate the origin of the plant MIP subfamilies, genomes of chlorophyte algae, the sister group of charophyte algae and land plants, were searched for MIP encoding genes. Results A total of 22 MIPs were identified in the nine analysed genomes and phylogenetic analyses classified them into seven subfamilies. Two of these, Plasma membrane Intrinsic Proteins (PIPs and GlpF-like Intrinsic Proteins (GIPs, are also present in land plants and divergence dating support a common origin of these algal and land plant MIPs, predating the evolution of terrestrial plants. The subfamilies unique to algae were named MIPA to MIPE to facilitate the use of a common nomenclature for plant MIPs reflecting phylogenetically stable groups. All of the investigated genomes contained at least one MIP gene but only a few species encoded MIPs belonging to more than one subfamily. Conclusions Our results suggest that at least two of the seven subfamilies found in land plants were present already in an algal ancestor. The total variation of MIPs and the number of different subfamilies in chlorophyte algae is likely to be even higher than that found in land plants. Our analyses indicate that genetic exchanges between several of the algal subfamilies have occurred. The PIP1 and PIP2 groups and the Ca2+ gating appear to be specific to land plants whereas the pH gating is a more ancient characteristic shared by all PIPs. Further studies are needed to discern the function of the algal specific subfamilies MIPA-E and to fully understand the evolutionary relationship of algal and terrestrial plant MIPs.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.S.; Sokol, R.C.; Liu, X.; Bethoney, C.M.; Rhee, G.Y. [State Univ. of New York and New York State Department of Health, Albany, NY (United States)

    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. Environmental effects on cephalopod population dynamics: implications for management of fisheries.

    Science.gov (United States)

    Rodhouse, Paul G K; Pierce, Graham J; Nichols, Owen C; Sauer, Warwick H H; Arkhipkin, Alexander I; Laptikhovsky, Vladimir V; Lipiński, Marek R; Ramos, Jorge E; Gras, Michaël; Kidokoro, Hideaki; Sadayasu, Kazuhiro; Pereira, João; Lefkaditou, Evgenia; Pita, Cristina; Gasalla, Maria; Haimovici, Manuel; Sakai, Mitsuo; Downey, Nicola

    2014-01-01

    Cephalopods are a relatively small class of molluscs (~800 species), but they support some large industrial scale fisheries and numerous small-scale, local, artisanal fisheries. For several decades, landings of cephalopods globally have grown against a background of total finfish landings levelling off and then declining. There is now evidence that in recent years, growth in cephalopod landings has declined. The commercially exploited cephalopod species are fast-growing, short-lived ecological opportunists. Annual variability in abundance is strongly influenced by environmental variability, but the underlying causes of the links between environment and population dynamics are poorly understood. Stock assessment models have recently been developed that incorporate environmental processes that drive variability in recruitment, distribution and migration patterns. These models can be expected to improve as more, and better, data are obtained on environmental effects and as techniques for stock identification improve. A key element of future progress will be improved understanding of trophic dynamics at all phases in the cephalopod life cycle. In the meantime, there is no routine stock assessment in many targeted fisheries or in the numerous by-catch fisheries for cephalopods. There is a particular need for a precautionary approach in these cases. Assessment in many fisheries is complicated because cephalopods are ecological opportunists and stocks appear to have benefited from the reduction of key predator by overexploitation. Because of the complexities involved, ecosystem-based fisheries management integrating social, economic and ecological considerations is desirable for cephalopod fisheries. An ecological approach to management is routine in many fisheries, but to be effective, good scientific understanding of the relationships between the environment, trophic dynamics and population dynamics is essential. Fisheries and the ecosystems they depend on can only be

  11. Infection dynamics in frog populations with different histories of decline caused by a deadly disease.

    Science.gov (United States)

    Sapsford, Sarah J; Voordouw, Maarten J; Alford, Ross A; Schwarzkopf, Lin

    2015-12-01

    Pathogens can drive host population dynamics. Chytridiomycosis is a fungal disease of amphibians that is caused by the fungus Batrachochytrium dendrobatidis (Bd). This pathogen has caused declines and extinctions in some host species whereas other host species coexist with Bd without suffering declines. In the early 1990s, Bd extirpated populations of the endangered common mistfrog, Litoria rheocola, at high-elevation sites, while populations of the species persisted at low-elevation sites. Today, populations have reappeared at many high-elevation sites where they presently co-exist with the fungus. We conducted a capture-mark-recapture (CMR) study of six populations of L. rheocola over 1 year, at high and low elevations. We used multistate CMR models to determine which factors (Bd infection status, site type, and season) influenced rates of frog survival, recapture, infection, and recovery from infection. We observed Bd-induced mortality of individual frogs, but did not find any significant effect of Bd infection on the survival rate of L. rheocola at the population level. Survival and recapture rates depended on site type and season. Infection rate was highest in winter when temperatures were favourable for pathogen growth, and differed among site types. The recovery rate was high (75.7-85.8%) across seasons, and did not differ among site types. The coexistence of L. rheocola with Bd suggests that (1) frog populations are becoming resistant to the fungus, (2) Bd may have evolved lower virulence, or (3) current environmental conditions may be inhibiting outbreaks of the fatal disease.

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

    Directory of Open Access Journals (Sweden)

    Reeta Sharma

    Full Text Available 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

  13. Population Dynamics of Owned, Free-Roaming Dogs: Implications for Rabies Control.

    Directory of Open Access Journals (Sweden)

    Anne Conan

    2015-11-01

    Full Text Available Rabies is a serious yet neglected public health threat in resource-limited communities in Africa, where the virus is maintained in populations of owned, free-roaming domestic dogs. Rabies elimination can be achieved through the mass vaccination of dogs, but maintaining the critical threshold of vaccination coverage for herd immunity in these populations is hampered by their rapid turnover. Knowledge of the population dynamics of free-roaming dog populations can inform effective planning and implementation of mass dog vaccination campaigns to control rabies.We implemented a health and demographic surveillance system in dogs that monitored the entire owned dog population within a defined geographic area in a community in Mpumalanga Province, South Africa. We quantified demographic rates over a 24-month period, from 1st January 2012 through 1st January 2014, and assessed their implications for rabies control by simulating the decline in vaccination coverage over time. During this period, the population declined by 10%. Annual population growth rates were +18.6% in 2012 and -24.5% in 2013. Crude annual birth rates (per 1,000 dog-years of observation were 451 in 2012 and 313 in 2013. Crude annual death rates were 406 in 2012 and 568 in 2013. Females suffered a significantly higher mortality rate in 2013 than males (mortality rate ratio [MRR] = 1.54, 95% CI = 1.28-1.85. In the age class 0-3 months, the mortality rate of dogs vaccinated against rabies was significantly lower than that of unvaccinated dogs (2012: MRR = 0.11, 95% CI = 0.05-0.21; 2013: MRR = 0.31, 95% CI = 0.11-0.69. The results of the simulation showed that achieving a 70% vaccination coverage during annual campaigns would maintain coverage above the critical threshold for at least 12 months.Our findings provide an evidence base for the World Health Organization's empirically-derived target of 70% vaccination coverage during annual campaigns. Achieving this will be effective even in

  14. Injecting epidemiology into population viability analysis: avian cholera transmission dynamics at an arctic seabird colony.

    Science.gov (United States)

    Iverson, Samuel A; Gilchrist, H Grant; Soos, Catherine; Buttler, Isabel I; Harms, N Jane; Forbes, Mark R

    2016-11-01

    Infectious diseases have the potential to spread rapidly and cause high mortality within populations of immunologically naïve hosts. The recent appearance of avian cholera, a highly virulent disease of birds caused by the bacterium Pasteurella multocida, at remote Arctic seabird colonies is an emerging conservation concern. Determining disease risk to population viability requires a quantitative understanding of transmission potential and the factors that regulate epidemic persistence. Estimates of the basic (R0 ) and real-time (Rt ) reproductive number are critical in this regard - enumerating the number of secondary infections caused by each primary infection in a newly invaded host population and the decline in transmission rate as susceptible individuals are removed via mortality or immunized recovery. Here, we use data collected at a closely monitored common eider (Somateria mollissima) breeding colony located in the Canadian Arctic to examine transmission and host population dynamics. Specifically, we infer epidemic curves from daily mortality observations and use a likelihood-based procedure to estimate changes in the reproductive number over a series of annual outbreaks. These data are interpreted in relation to concurrent changes in host numbers to assess local extinction risk. Consistent with expectations for a novel pathogen invasion, case incidence increased exponentially during the initial wave of exposure (R0  = 2·5; generation time = 6·5 days ± 1·1 SD). Disease conditions gradually abated, but only after several years of smouldering infection (Rt  ≈ 1). In total, 6194 eider deaths were recorded during outbreaks spanning eight consecutive breeding seasons. Breeding pair abundance declined by 56% from the pre-outbreak peak; however, a robust population of >4000 pairs remained intact upon epidemic fade-out. Overall, outbreak patterns were consistent with herd immunity acting as a mitigating factor governing in the extent and duration of

  15. The engine of the reef: Photobiology of the coral-algal symbiosis

    Directory of Open Access Journals (Sweden)

    Melissa Susan Roth

    2014-08-01

    Full Text Available Coral reef ecosystems thrive in tropical oligotrophic oceans because of the relationship between corals and endosymbiotic dinoflagellate algae called Symbiodinium. Symbiodinium convert sunlight and carbon dioxide into organic carbon and oxygen to fuel coral growth and calcification, creating habitat for these diverse and productive ecosystems. Light is thus a key regulating factor shaping the productivity, physiology and ecology of the coral holobiont. Similar to all oxygenic photoautotrophs, Symbiodinium must safely harvest sunlight for photosynthesis and dissipate excess energy to prevent oxidative stress. Oxidative stress is caused by environmental stressors such as those associated with global climate change, and ultimately leads to breakdown of the coral-algal symbiosis known as coral bleaching. Recently, large-scale coral bleaching events have become pervasive and frequent threatening and endangering coral reefs. Because the coral-algal symbiosis is the biological engine producing the reef, the future of coral reef ecosystems depends on the ecophysiology of the symbiosis. This review examines the photobiology of the coral-algal symbiosis with particular focus on the photophysiological responses and timescales of corals and Symbiodinium. Additionally, this review summarizes the light environment and its dynamics, the vulnerability of the symbiosis to oxidative stress, the abiotic and biotic factors influencing photosynthesis, the diversity of the coral-algal symbiosis and recent advances in the field. Studies integrating physiology with the developing omics fields will provide new insights into the coral-algal symbiosis. Greater physiological and ecological understanding of the coral-algal symbiosis is needed for protection and conservation of coral reefs.

  16. Using Dynamic Stochastic Modelling to Estimate Population Risk Factors in Infectious Disease: The Example of FIV in 15 Cat Populations

    OpenAIRE

    David Fouchet; Guillaume Leblanc; Frank Sauvage; Micheline Guiserix; Hervé Poulet; Dominique Pontier

    2009-01-01

    BACKGROUND: In natural cat populations, Feline Immunodeficiency Virus (FIV) is transmitted through bites between individuals. Factors such as the density of cats within the population or the sex-ratio can have potentially strong effects on the frequency of fight between individuals and hence appear as important population risk factors for FIV. METHODOLOGY/PRINCIPAL FINDINGS: To study such population risk factors, we present data on FIV prevalence in 15 cat populations in northeastern France. ...

  17. Temporal dynamics and impact of event interactions in cyber-social populations

    Science.gov (United States)

    Zhang, Yi-Qing; Li, Xiang

    2013-03-01

    The advance of information technologies provides powerful measures to digitize social interactions and facilitate quantitative investigations. To explore large-scale indoor interactions of a social population, we analyze 18 715 users' Wi-Fi access logs recorded in a Chinese university campus during 3 months, and define event interaction (EI) to characterize the concurrent interactions of multiple users inferred by their geographic coincidences—co-locating in the same small region at the same time. We propose three rules to construct a transmission graph, which depicts the topological and temporal features of event interactions. The vertex dynamics of transmission graph tells that the active durations of EIs fall into the truncated power-law distributions, which is independent on the number of involved individuals. The edge dynamics of transmission graph reports that the transmission durations present a truncated power-law pattern independent on the daily and weekly periodicities. Besides, in the aggregated transmission graph, low-degree vertices previously neglected in the aggregated static networks may participate in the large-degree EIs, which is verified by three data sets covering different sizes of social populations with various rendezvouses. This work highlights the temporal significance of event interactions in cyber-social populations.

  18. Evolutionary dynamics of public goods games with diverse contributions in finite populations.

    Science.gov (United States)

    Wang, Jing; Wu, Bin; Chen, Xiaojie; Wang, Long

    2010-05-01

    The public goods game is a powerful metaphor for exploring the maintenance of social cooperative behavior in a group of interactional selfish players. Here we study the emergence of cooperation in the public goods games with diverse contributions in finite populations. The theory of stochastic process is innovatively adopted to investigate the evolutionary dynamics of the public goods games involving a diversity of contributions. In the limit of rare mutations, the general stationary distribution of this stochastic process can be analytically approximated by means of diffusion theory. Moreover, we demonstrate that increasing the diversity of contributions greatly reduces the probability of finding the population in a homogeneous state full of defectors. This increase also raises the expectation of the total contribution in the entire population and thus promotes social cooperation. Furthermore, by investigating the evolutionary dynamics of optional public goods games with diverse contributions, we find that nonparticipation can assist players who contribute more in resisting invasion and taking over individuals who contribute less. In addition, numerical simulations are performed to confirm our analytical results. Our results may provide insight into the effect of diverse contributions on cooperative behaviors in the real world.

  19. The dynamical state and blue straggler population of the globular cluster NGC 6266 (M62)

    CERN Document Server

    Beccari, G; Origlia, L; Possenti, A; Rood, R T; Valenti, E

    2006-01-01

    We have used a proper combination of multiband high-resolution {\\it HST-WFPC2} and wide-field ground based observations to image the galactic globular cluster NGC 6266 (M62). The extensive photometric data set allows us to determine the center of gravity and to construct the most extended radial profile ever published for this cluster including, for the first time, detailed star counts in the very inner region. The star density profile is well reproduced by a standard King model with an extended core ($\\sim 19''$) and a modest value of the concentration parameter ($c=1.5$), indicating that the cluster has not-yet experienced core collapse. The millisecond pulsar population (whose members are all in binary systems) and the X-ray emitting population (more than 50 sources within the cluster half mass radius) suggest that NGC 6266 is in a dynamical phase particularly active in generating binaries through dynamical encounters. UV observations of the central region have been used to probe the population of blue str...

  20. Assessing spatial coupling in complex population dynamics using mutual prediction and continuity statistics

    Science.gov (United States)

    Nichols, J.M.; Moniz, L.; Nichols, J.D.; Pecora, L.M.; Cooch, E.

    2005-01-01

    A number of important questions in ecology involve the possibility of interactions or ?coupling? among potential components of ecological systems. The basic question of whether two components are coupled (exhibit dynamical interdependence) is relevant to investigations of movement of animals over space, population regulation, food webs and trophic interactions, and is also useful in the design of monitoring programs. For example, in spatially extended systems, coupling among populations in different locations implies the existence of redundant information in the system and the possibility of exploiting this redundancy in the development of spatial sampling designs. One approach to the identification of coupling involves study of the purported mechanisms linking system components. Another approach is based on time series of two potential components of the same system and, in previous ecological work, has relied on linear cross-correlation analysis. Here we present two different attractor-based approaches, continuity and mutual prediction, for determining the degree to which two population time series (e.g., at different spatial locations) are coupled. Both approaches are demonstrated on a one-dimensional predator?prey model system exhibiting complex dynamics. Of particular interest is the spatial asymmetry introduced into the model as linearly declining resource for the prey over the domain of the spatial coordinate. Results from these approaches are then compared to the more standard cross-correlation analysis. In contrast to cross-correlation, both continuity and mutual prediction are clearly able to discern the asymmetry in the flow of information through this system.

  1. Population cycles and species diversity in dynamic Kill-the-Winner model of microbial ecosystems

    Science.gov (United States)

    Maslov, Sergei; Sneppen, Kim

    2017-01-01

    Determinants of species diversity in microbial ecosystems remain poorly understood. Bacteriophages are believed to increase the diversity by the virtue of Kill-the-Winner infection bias preventing the fastest growing organism from taking over the community. Phage-bacterial ecosystems are traditionally described in terms of the static equilibrium state of Lotka-Volterra equations in which bacterial growth is exactly balanced by losses due to phage predation. Here we consider a more dynamic scenario in which phage infections give rise to abrupt and severe collapses of bacterial populations whenever they become sufficiently large. As a consequence, each bacterial population in our model follows cyclic dynamics of exponential growth interrupted by sudden declines. The total population of all species fluctuates around the carrying capacity of the environment, making these cycles cryptic. While a subset of the slowest growing species in our model is always driven towards extinction, in general the overall ecosystem diversity remains high. The number of surviving species is inversely proportional to the variation in their growth rates but increases with the frequency and severity of phage-induced collapses. Thus counter-intuitively we predict that microbial communities exposed to more violent perturbations should have higher diversity.

  2. Analysis of algal bloom risk with uncertainties in lakes by integrating self-organizing map and fuzzy information theory.

    Science.gov (United States)

    Chen, Qiuwen; Rui, Han; Li, Weifeng; Zhang, Yanhui

    2014-06-01

    Algal blooms are a serious problem in waters, which damage aquatic ecosystems and threaten drinking water safety. However, the outbreak mechanism of algal blooms is very complex with great uncertainty, especially for large water bodies where environmental conditions have obvious variation in both space and time. This study developed an innovative method which integrated a self-organizing map (SOM) and fuzzy information diffusion theory to comprehensively analyze algal bloom risks with uncertainties. The Lake Taihu was taken as study case and the long-term (2004-2010) on-site monitoring data were used. The results showed that algal blooms in Taihu Lake were classified into four categories and exhibited obvious spatial-temporal patterns. The lake was mainly characterized by moderate bloom but had high uncertainty, whereas severe blooms with low uncertainty were observed in the northwest part of the lake. The study gives insight on the spatial-temporal dynamics of algal blooms, and should help government and decision-makers outline policies and practices on bloom monitoring and prevention. The developed method provides a promising approach to estimate algal bloom risks under uncertainties.

  3. Computational analysis of complex systems: Applications to population dynamics and networks

    Science.gov (United States)

    Molnar, Ferenc

    In most complex evolving systems, we can often find a critical subset of the constituents that can initiate a global change in the entire system. For example, in complex networks, a critical subset of nodes can efficiently spread information, influence, or control dynamical processes over the entire network. Similarly, in nonlinear dynamics, we can locate key variables, or find the necessary parameters, to reach the attraction basin of a desired global state. In both cases, a fundamental goal is finding the ability to efficiently control these systems. We study two distinct complex systems in this dissertation, exploring these topics. First, we analyze a population dynamics model describing interactions of sex-structured population groups. Specifically, we analyze how a sex-linked genetic trait's ecological consequence (population survival or extinction) can be influenced by the presence of sex-specific cultural mortality traits, motivated by the desire to expand the theoretical understanding of the role of biased sex ratios in organisms. We analyze dynamics within a single population group, as well as between competing groups. We find that there is a finite range of sex ratio bias that can be maintained in stable equilibrium by sex-specific mortalities. We also find that the outcome of an invasion and the ensuing between-group competition depends not on larger equilibrium group densities, but on the higher allocation of sex-ratio genes. When we extend the model with diffusive dispersal, we find that a critical patch size for achieving positive growth only exists if the population expands into an empty environment. If a resident population is already present that can be exploited by the invading group, then any small seed of invader can advance from rarity, in the mean-field approximation, as long as the local competition dynamics favors the invader's survival. Most spatial models assume initial populations with a uniform distribution inside a finite patch; a

  4. Population dynamics and movement of Ozark cavefish in Logan Cave NWR, Benton County, Arkansas, with additional baseline water quality information

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The population dynamics, general biology, and movements of the threatened Ozark cavefish (Amblyopsis rosae) were studied in Logan Cave National Wildlife Refuge,...

  5. Dynamics of two populations of phase oscillators with different frequency distributions

    CERN Document Server

    Terada, Yu

    2014-01-01

    A large variety of rhythms have been observed in nature. These rhythms can be often regarded to interact with each other, such as electroencephalogram (EEG) in the brain. To investigate the dynamical properties of such systems, in this paper, we consider two populations of phase oscillators with different frequency distributions, particularly under the condition that the average frequency of fast oscillators is almost equal to the integral multiple of that of slow oscillators. What is the most important point is that we have to use the specific type of the coupling function derived from the phase reduction theory. Under some additional assumption, moreover, we can reduce the system consisting of two populations of coupled phase oscillators to a low-dimensional system in the continuum limit. As a result, we find chimera states in which clustering and incoherent states coexist. We also confirm that the behaviors of the derived low-dimensional model fairly agree with that of the original one.

  6. Carnivora population dynamics are as slow and as fast as those of other mammals

    DEFF Research Database (Denmark)

    van de Kerk, Madelon; de Kroon, Hans; Jongejans, Eelke;

    2013-01-01

    in triangular elasticity plots as those of other mammal species, despite the specific place of Carnivora in the food chain. Furthermore, reproductive loop elasticity analysis shows that the studied species spread out evenly over a slow-fast continuum, but also quantifies the large variation in the duration...... of important life cycles and their contributions to population growth rate. These general elasticity patterns among species, and their correlation with simple life history characteristics like body mass, age of first reproduction and life span, enables the extrapolation of population dynamical properties...... to unstudied species. With several examples we discuss how this slow-fast continuum, and related patterns of variation in reproductive loop elasticity, can be used in the formulation of tentative management plans for threatened species that cannot wait for the results of thorough demographic studies. We argue...

  7. Global dynamics of delay equations for populations with competition among immature individuals

    Science.gov (United States)

    Liz, Eduardo; Ruiz-Herrera, Alfonso

    2016-04-01

    We analyze a population model for two age-structured species allowing for inter- and intra-specific competition at immature life stages. The dynamics is governed by a system of Delay Differential Equations (DDEs) recently introduced by Gourley and Liu. The analysis of this model presents serious difficulties because the right-hand sides of the DDEs depend on the solutions of a system of nonlinear ODEs, and generally cannot be solved explicitly. Using the notion of strong attractor, we reduce the study of the attracting properties of the equilibria of the DDEs to the analysis of a related two-dimensional discrete system. Then, we combine some tools for monotone planar maps and planar competing Lotka-Volterra systems to describe the dynamics of the model with three different birth rate functions. We give easily verifiable conditions for global extinction of one or the two species, and for global convergence of the positive solutions to a coexistence state.

  8. The Impact of Stellar Populations on the Dynamics of Merger Remnants

    CERN Document Server

    Rothberg, B

    2009-01-01

    Many studies and simulations suggest gas-rich mergers do not contribute significantly to the overall star-formation rate and total mass function of galaxies. The velocity dispersions (sigma) of Luminous & Ultraluminous Infrared Galaxies measured using the 1.62 or 2.29 micron CO bandheads imply they will form m m* ellipticals. Presented here are recent results, based on high-resolution imaging and multi-wavelength spectroscopy, which demonstrate the dominance of a nuclear disk of Red Supergiants (RSG) or Asymptotic Giant Branch (AGB) stars in the near-infrared bands, where dust obscuration does not sufficiently block their signatures. The presence of these stars severely biases the dynamical mass. At I-band, where dust can sufficiently block RSG or AGB stars, LIRGs populate the Fundamental Plane over a large dynamic range and are virtually indistinguishable from elliptical galaxies.

  9. A phenomenological approach to the simulation of metabolism and proliferation dynamics of large tumour cell populations

    CERN Document Server

    Chignola, R; Chignola, Roberto; Milotti, Edoardo

    2005-01-01

    A major goal of modern computational biology is to simulate the collective behaviour of large cell populations starting from the intricate web of molecular interactions occurring at the microscopic level. In this paper we describe a simplified model of cell metabolism, growth and proliferation, suitable for inclusion in a multicell simulator, now under development (Chignola R and Milotti E 2004 Physica A 338 261-6). Nutrients regulate the proliferation dynamics of tumor cells which adapt their behaviour to respond to changes in the biochemical composition of the environment. This modeling of nutrient metabolism and cell cycle at a mesoscopic scale level leads to a continuous flow of information between the two disparate spatiotemporal scales of molecular and cellular dynamics that can be simulated with modern computers and tested experimentally.

  10. Dynamic Change of Genetic Diversity in Conserved Populations with Different Initial Genetic Architectures

    Institute of Scientific and Technical Information of China (English)

    LU Yun-feng; LI Hong-wei; WU Ke-liang; WU Chang-xin

    2013-01-01

    Maintenance and management of genetic diversity of farm animal genetic resources (AnGR) is very important for biological, socioeconomical and cultural significance. The core concern of conservation for farm AnGR is the retention of genetic diversity of conserved populations in a long-term perspective. However, numerous factors may affect evolution of genetic diversity of a conserved population. Among those factors, the genetic architecture of conserved populations is little considered in current conservation strategies. In this study, we investigated the dynamic changes of genetic diversity of conserved populations with two scenarios on initial genetic architectures by computer simulation in which thirty polymorphic microsatellite loci were chosen to represent genetic architecture of the populations with observed heterozygosity (Ho) and expected heterozygosity (He), observed and mean effective number of alleles (Ao and Ae), number of polymorphic loci (NP) and the percentage of polymorphic loci (PP), number of rare alleles (RA) and number of non-rich polymorphic loci (NRP) as the estimates of genetic diversity. The two scenarios on genetic architecture were taken into account, namely, one conserved population with same allele frequency (AS) and another one with actual allele frequency (AA). The results showed that the magnitude of loss of genetic diversity is associated with genetic architecture of initial conserved population, the amplitude of genetic diversity decline in the context AS was more narrow extent than those in context AA, the ranges of decline of Ho and Ao were about 4 and 2 times in AA compared with that in AS, respectively, the occurrence of first monomorphic locus and the time of change of measure NP in scenario AA is 20 generations and 23 generations earlier than that in scenario AS, respectively. Additionally, we found that NRP, a novel measure proposed by our research group, was a proper estimate for monitoring the evolution of genetic diversity

  11. Population Dynamic of Dendronephthya sp.-Associated Bacteria in Natural and Artificial Habitats

    Directory of Open Access Journals (Sweden)

    SUSAN SOKA

    2011-06-01

    Full Text Available Dendronephthya sp. is a soft coral that has huge distribution starting from Indopacific, Tonga, Solomon Islands to Great Barrier Reef in Australia. However, this soft corals survive only in short period after cultivation in artificial habitat (aquarium. Recent study showed that the soft coral Dendronephtya sp. has an association or symbiotic relationship with several bacteria, commonly known as coral associated bacteria (CAB. In this study, we compared the population dynamic of Dendronephthya sp.-associated bacteria in natural and artificial habitat, resulting different bacterial community profiles using terminal restriction fragment length polymorphism (T-RFLP analysis of bacterial community DNA. There were 15 main classes of bacterial population identified along with uncultured microorganism, uncultured organism, uncultured bacteria and unidentified organism. Members of Actinobacteria, Arthrobacteria, Chlorobia, Caldilineae, -proteobacteria and Proteobacteria were predicted to give contributions in the survival ability of both Dendronephthya sp. The cultivation of soft corals after 2 weeks in artificial habitat increases bacterial population similarity on 2 different samples by 10%. Bacterial population similarity in artificial habitat would increase along with the longer cultivation time of soft corals.

  12. Genetic diversity and population dynamics of Bordetella pertussis in China between 1950-2007.

    Science.gov (United States)

    Xu, Yinghua; Zhang, Liu; Tan, Yajun; Wang, Lichan; Zhang, Shumin; Wang, Junzhi

    2015-11-17

    Pertussis is an acute respiratory infectious disease caused by the bacterium Bordetella pertussis. Although pertussis vaccination was introduced in the 1960s, pertussis is still an endemic disease in China. To better understand the genetic diversity of the Chinese B. pertussis population, we characterized 115 clinical isolates obtained in China during 1950-2007 using multilocus variable-number tandem repeat analysis (MLVA). Forty-six different B. pertussis MLVA profiles (MTs) were identified, of which 13 were new MTs. Analysis using a minimum-spanning tree showed that distinct MTs were prevalent during different periods, suggesting that a dynamic change in B. pertussis MTs occurred over time in China. The predominant MTs in recent isolates from China were different from those of many developed countries. A decreasing trend in genetic diversity of the B. pertussis population was observed following the introduction of pertussis vaccines. Similar to the pertactin 2 (prn2) allele, the novel pertussis toxin promoter (ptxP3) allele first emerged in 2000, but unlike trends elsewhere, ptxP1 remained predominant among the isolates, further reflecting the unique temporal trends in the B. pertussis population in China. Our results suggest that temporal changes in the B. pertussis population may be closely associated with vaccination coverage and the vaccine types used. These data may lead to an improved understanding of the virulence mechanism of B. pertussis and facilitate new strategies for controlling this infectious disease.

  13. Population dynamics, distribution, and species diversity of fruit flies on cucurbits in Kashmir Valley, India.

    Science.gov (United States)

    Ganie, S A; Khan, Z H; Ahangar, R A; Bhat, H A; Hussain, Barkat

    2013-01-01

    Given the economic importance of cucurbits and the losses incurred by fruit fly infestation, the population dynamics of fruit flies in cucurbit crops and the influence of abiotic parameters, such as temperature, relative humidity, rainfall, and total sunshine hours per day on the fruit fly population were studied. The study was carried out at six locations; in district Srinagar the locations were Batmaloo, Shalimar, and Dal, while in district Budgam the locations were Chadoora, Narkara, and Bugam (Jammu and Kashmir, India). Various cucurbit crops, such as cucumber, bottle gourd, ridge gourd and bitter gourd, were selected for the study. With regard to locations, mean fruit fly population was highest (6.09, 4.55, 3.87, and 3.60 flies/trap/week) at Batamaloo and Chadoora (4.73, 3.93, 2.73, and 2.73 flies/trap/week) on cucumber, bottle gourd, ridge gourd, and bitter gourd, respectively. The population of fruit flies was significantly correlated with the minimum and maximum temperature. The maximum species diversity of fruit flies was 0.511, recorded in Chadoora. Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) was the most predominant species in both Srinagar and Budgam, followed by B. dorsalis (Hendel) and B. tau (Walker), while B. scutellaris (Bezzi) was found only in Chadoora. Results of the present investigation may be utilized in developing a sustainable pest management strategy in the agroecological system.

  14. Modelling the impact of marine reserves on a population with depensatory dynamics.

    Science.gov (United States)

    Chan, Matthew H; Kim, Peter S

    2014-09-01

    In this study, we use a spatially implicit, stage-structured model to evaluate marine reserve effectiveness for a fish population exhibiting depensatory (strong Allee) effects in its dynamics. We examine the stability and sensitivity of the equilibria of the modelled system with regards to key system parameters and find that for a reasonable set of parameters, populations can be protected from a collapse if a small percentage of the total area is set aside in reserves. Furthermore, the overall abundance of the population is predicted to achieve a maximum at a certain ratio A of reserve area to fished area, which depends heavily on the other system parameters such as the net export rate of fish from the marine reserves to the fished areas. This finding runs contrary to the contested "equivalence at best" result when comparing fishery management through traditional catch or effort control and management through marine reserves. Lastly, we analyse the problem from a bioeconomics perspective by computing the optimal harvesting policy using Pontryagin's Maximum Principle, which suggests that the value for A which maximizes the optimal equilibrium fishery yield also maximizes population abundance when the cost per unit harvest is constant, but can increase substantially when the cost per unit harvest increases with the area being harvested.

  15. Role of Demographic Dynamics and Conflict in the Population-Area Relationship for Human Languages

    Science.gov (United States)

    Manrubia, Susanna C.; Axelsen, Jacob B.; Zanette, Damián H.

    2012-01-01

    Many patterns displayed by the distribution of human linguistic groups are similar to the ecological organization described for biological species. It remains a challenge to identify simple and meaningful processes that describe these patterns. The population size distribution of human linguistic groups, for example, is well fitted by a log-normal distribution that may arise from stochastic demographic processes. As we show in this contribution, the distribution of the area size of home ranges of those groups also agrees with a log-normal function. Further, size and area are significantly correlated: the number of speakers and the area spanned by linguistic groups follow the allometric relation , with an exponent varying accross different world regions. The empirical evidence presented leads to the hypothesis that the distributions of and , and their mutual dependence, rely on demographic dynamics and on the result of conflicts over territory due to group growth. To substantiate this point, we introduce a two-variable stochastic multiplicative model whose analytical solution recovers the empirical observations. Applied to different world regions, the model reveals that the retreat in home range is sublinear with respect to the decrease in population size, and that the population-area exponent grows with the typical strength of conflicts. While the shape of the population size and area distributions, and their allometric relation, seem unavoidable outcomes of demography and inter-group contact, the precise value of could give insight on the cultural organization of those human groups in the last thousand years. PMID:22815726

  16. Finite-time singularity in the dynamics of the world population, economic and financial indices

    Science.gov (United States)

    Johansen, Anders; Sornette, Didier

    2001-05-01

    Contrary to common belief, both the Earth's human population and its economic output have grown faster than exponential, i.e., in a super-Malthusian mode, for most of the known history. These growth rates are compatible with a spontaneous singularity occurring at the same critical time 2052±10 signaling an abrupt transition to a new regime. The degree of abruptness can be infered from the fact that the maximum of the world population growth rate was reached in 1970, i.e., about 80 years before the predicted singular time, corresponding to approximately 4% of the studied time interval over which the acceleration is documented. This rounding-off of the finite-time singularity is probably due to a combination of well-known finite-size effects and friction and suggests that we have already entered the transition region to a new regime. As theoretical support, a multivariate analysis coupling population, capital, R&D and technology shows that a dramatic acceleration in the population growth during most of the timespan can occur even though the isolated dynamics do not exhibit it. Possible scenarios for the cross-over and the new regime are discussed.

  17. Population dynamics of Azotobacter chroococcum in sugarbeet rhizosphere depending on mineral nutrition

    Directory of Open Access Journals (Sweden)

    Mrkovački Nastasija B.

    2003-01-01

    Full Text Available Population dynamics of Azotobacter chroococcum has been studied in the rhizosphere of a sugarbeet hybrid inoculated with Azotobacter strains 5, 8 and 14. Simultaneously we examined the effects of four levels of nitrogen fertilization (non-fertilized control, 50, 100, 150 and 200 kg N/ha and the applications of manure and harvest residues. Samples were taken three times in May, July and October. The experiment included inoculated and non-inoculated variants at all four levels of fertilization, in five replicates.

  18. Investigating population dynamics of the Kumbh Mela through the lens of cell phone data

    CERN Document Server

    Onnela, Jukka-Pekka

    2015-01-01

    The Kumbh is a religious Hindu festival that has been celebrated for centuries. The 2013 Kumbh Mela, a grander form of the annual Kumbh, was purportedly the largest gathering of people in human history. Many of the participants carried cell phones, making it possible for us to use a data-driven approach to document this magnificent festival. We used Call Detail Records (CDRs) from participants attending the event, a total of 390 million records, to investigate its population dynamics. We report here on some of our preliminary findings.

  19. Analysis of Head and Neck Dynamic Response of the U.S. Adult Military Population.

    Science.gov (United States)

    1986-04-15

    simulation results at -6Gx showed the largest error in condyles extension to be in peak and duration of condylar extension motion. Therefore, neck ...satisfactory. It was subsequently concluded that a two-joint neck with pivot points at the occipital * condyles and at T1 cannot produce a condylar ...Report No. 3 Analysis of Head and Neck Wow Dynamic Response of the U.S. Adult Military Population A.C. Bosio B.M. Bowman L-LECTEK JUL 08 i82 PREPARED

  20. Catalysis of protein folding by chaperones accelerates evolutionary dynamics in adapting cell populations.

    Science.gov (United States)

    Cetinbaş, Murat; Shakhnovich, Eugene I

    2013-01-01

    Although molecular chaperones are essential components of protein homeostatic machinery, their mechanism of action and impact on adaptation and evolutionary dynamics remain controversial. Here we developed a physics-based ab initio multi-scale model of a living cell for population dynamics simulations to elucidate the effect of chaperones on adaptive evolution. The 6-loci genomes of model cells encode model proteins, whose folding and interactions in cellular milieu can be evaluated exactly from their genome sequences. A genotype-phenotype relationship that is based on a simple yet non-trivially postulated protein-protein interaction (PPI) network determines the cell division rate. Model proteins can exist in native and molten globule states and participate in functional and all possible promiscuous non-functional PPIs. We find that an active chaperone mechanism, whereby chaperones directly catalyze protein folding, has a significant impact on the cellular fitness and the rate of evolutionary dynamics, while passive chaperones, which just maintain misfolded proteins in soluble complexes have a negligible effect on the fitness. We find that by partially releasing the constraint on protein stability, active chaperones promote a deeper exploration of sequence space to strengthen functional PPIs, and diminish the non-functional PPIs. A key experimentally testable prediction emerging from our analysis is that down-regulation of chaperones that catalyze protein folding significantly slows down the adaptation dynamics.