Journal articles: 'Models for competing specie'

1

A. Saenz, Roberto, and Herbert W. Hethcote. "Competing species models with an infectious disease." Mathematical Biosciences and Engineering 3, no. 1 (2006): 219–35. http://dx.doi.org/10.3934/mbe.2006.3.219.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Pereira, T. A., J. Menezes, and L. Losano. "Interface networks in models of competing species." International Journal of Modeling, Simulation, and Scientific Computing 09, no. 05 (October 2018): 1850046. http://dx.doi.org/10.1142/s1793962318500460.

Full text

Abstract:

We study a subclass of the May–Leonard stochastic model with an arbitrary, even number of species, leading to the rise of two competing partnerships where individuals are indistinguishable. By carrying out a series of accurate numerical stochastic simulations, we show that alliances compete each other forming spatial domains bounded by interfaces of empty sites. We solve numerically the mean field equations associated with the stochastic model in one and two spatial dimensions. We demonstrate that the stationary interface profile presents topological properties which are related to the asymptotic spatial distribution of species of enemy alliances far away from the interface core. Finally, we introduce a theoretical approach to model the formation of stable interfaces using spontaneous breaking of a discrete symmetry. We show that all the results provided by the soliton topological model, presented here for the very first time, are in agreement with the stochastic simulations and may be used as a tool for understanding the complex biodiversity in nature.

APA, Harvard, Vancouver, ISO, and other styles

3

Sumner, Suzanne. "Hopf bifurcation in pioneer-climax competing species models." Mathematical Biosciences 137, no. 1 (October 1996): 1–24. http://dx.doi.org/10.1016/s0025-5564(96)00065-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Szabó, György. "Competing associations in six-species predator–prey models." Journal of Physics A: Mathematical and General 38, no. 30 (July 13, 2005): 6689–702. http://dx.doi.org/10.1088/0305-4470/38/30/005.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Xu, Benlong, and Zhenzhang Ni. "Permanence of Diffusive Models for Three Competing Species in Heterogeneous Environments." Abstract and Applied Analysis 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/376919.

Full text

Abstract:

We address the question of the long-term coexistence of three competing species whose dynamics are governed by the partial differential equations. We obtain criteria for permanent coexistence in a Lotka-Volterra system modeling the interaction of three competing species in a bounded habitat whose exterior is lethal to each species. It is also proved that if the intercompeting strength is very weak, the system is always permanent, provided that each single one of the three species can survive in the absence of the two other species.

APA, Harvard, Vancouver, ISO, and other styles

6

Mwalusepo, Sizah, Henri E. Z. Tonnang, Estomih S. Massawe, Tino Johansson, and Bruno Pierre Le Ru. "Stability Analysis of Competing Insect Species for a Single Resource." Journal of Applied Mathematics 2014 (2014): 1–14. http://dx.doi.org/10.1155/2014/285350.

Full text

Abstract:

The models explore the effects of resource and temperature on competition between insect species. A system of differential equations is proposed and analysed qualitatively using stability theory. A local study of the models is performed around axial, planar, and interior equilibrium points to successively estimate the effect of (i) one species interacting with a resource, (ii) two competing species for a single resource, and (iii) three competing species for a single resource. The local stability analysis of the equilibrium is discussed using Routh-Hurwitz criteria. Numerical simulation of the models is performed to investigate the sensitivity of certain key parameters. The models are used to predict population dynamics in the selected cases studied. The results show that when a single species interacts with a resource, the species will be able to establish and sustain a stable population. However, in competing situation, it is observed that the combinations of three parameters (half-saturation, growth rate, and mortality rate) determine which species wins for any given resource. Moreover, our results indicate that each species is the superior competitor for the resource for the range of temperature for which it has the lowest equilibrium resource.

APA, Harvard, Vancouver, ISO, and other styles

7

Lopez-Gomez, Julian, and Jose C. Sabina De Lis. "Coexistence States and Global Attractivity for Some Convective Diffusive Competing Species Models." Transactions of the American Mathematical Society 347, no. 10 (October 1995): 3797. http://dx.doi.org/10.2307/2155205.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

López-Gómez, Julián, and José C. Sabina de Lis. "Coexistence states and global attractivity for some convective diffusive competing species models." Transactions of the American Mathematical Society 347, no. 10 (October 1, 1995): 3797–833. http://dx.doi.org/10.1090/s0002-9947-1995-1311910-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Sumner, Suzanne. "STABLE PERIODIC BEHAVIOR IN PIONEER-CLIMAX COMPETING SPECIES MODELS WITH CONSTANT RATE FORCING." Natural Resource Modeling 11, no. 2 (June 1998): 155–71. http://dx.doi.org/10.1111/j.1939-7445.1998.tb00306.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Dancer, E. N. "On the existence and uniqueness of positive solutions for competing species models with diffusion." Transactions of the American Mathematical Society 326, no. 2 (February 1, 1991): 829–59. http://dx.doi.org/10.1090/s0002-9947-1991-1028757-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

López-López, Pascual, Alvaro Soutullo, Clara García-Ripollés, Vicente Urios, Luis Cadahía, and Miguel Ferrer. "Markov models of territory occupancy: implications for the management and conservation of competing species." Biodiversity and Conservation 18, no. 5 (September 17, 2008): 1389–402. http://dx.doi.org/10.1007/s10531-008-9469-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Li, Yongfeng, Jingan Cui, and Xinyu Song. "Asymptotic behaviour of the non-autonomous competing two-species Lotka–Volterra models with impulsive effect." Journal of Biological Dynamics 3, no. 1 (January 2009): 58–72. http://dx.doi.org/10.1080/17513750802158661.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Dubey, B., and J. Hussain. "Nonlinear models for the survival of two competing species dependent on resource in industrial environments." Nonlinear Analysis: Real World Applications 4, no. 1 (March 2003): 21–44. http://dx.doi.org/10.1016/s1468-1218(02)00011-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

López-Gómez, Julián. "On the structure of the permanence region for competing species models with general diffusivities and transport effects." Discrete & Continuous Dynamical Systems - A 2, no. 4 (1996): 525–42. http://dx.doi.org/10.3934/dcds.1996.2.525.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Wisheu, Irene C., and Paul Keddy. "Three Competing Models for Predicting the Size of Species Pools: A Test Using Eastern North American Wetlands." Oikos 76, no. 2 (June 1996): 253. http://dx.doi.org/10.2307/3546197.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

van Vuuren, Jan H., and John Norbury. "Conditions for permanence in well-known biological competition models." ANZIAM Journal 42, no. 2 (October 2000): 195–223. http://dx.doi.org/10.1017/s1446181100011871.

Full text

Abstract:

AbstractReaction-diffusion systems are widely used to model the population densities of biological species competing for natural resources in their common habitat. It is often not too difficult to establish positive uniform upper bounds on solution components of such systems, but the task of establishing strictly positive uniform lower bounds (when they exist) can be quite troublesome. Two previously established criteria for the permanence (non-extinction and non-explosion) of solutions of general weakly-coupled competition-diffusion systems with diagonally convex reaction terms are used here as background to develop more easily verifiable and concrete conditions for permanence in various well-known competition diffusion models. These models include multi-component reaction-diffusion systems with (i) the by now classical Lotka-Volterra (logistic) reaction terms, (ii) higher order “logistic” interaction between the species, (iii) logistic-logarithmic reaction terms, (iv) Ayala-Gilpin-Ehrenfeld θ-interaction terms (which are used to model Drosophila competition), (v) logistic-exponential interaction between the species, (vi) Schoener-exploitation and (vii) modified Schoener-interference between the species. In (i) a known condition for permanence (for the ODE-system) is recovered, while in (ii)–(vii) new criteria for permanence are established.

APA, Harvard, Vancouver, ISO, and other styles

17

Heske, Edward J., Richard S. Ostfeld, and William Z. Lidicker Jr. "Does social behavior drive vole cycles? An evaluation of competing models as they pertain to California voles." Canadian Journal of Zoology 66, no. 5 (May 1, 1988): 1153–59. http://dx.doi.org/10.1139/z88-168.

Full text

Abstract:

The literature contains a number of verbal and mathematical models that assert that social behavior drives the multiannual density cycles characteristic of many vole species. Many of the assumptions about vole behavior on which the models are based remain unverified. In this paper we briefly review these models and their underlying assumptions. We then use natural history data on the social behavior of California voles (Microtus californicus) to critically examine the plausibility of these assumptions. We do not attempt to explain vole cycles, but only to evaluate models that rely strongly on social behavior as a critical component. Our results indicate that (i) critical assumptions of the behavioral polymorphism, social stress, and social breakdown hypotheses are not met; (ii) some assumptions of the kin selection hypothesis are met whereas others are not; and (iii) assumptions of the habitat patchiness – dispersal hypothesis are met. However, published models of dispersal and habitat patchiness must invoke additional factors, such as resource depletion or predation, before cycles result. We conclude that social behavior is unlikely to be a driving force in the generation of cycles in the California vole. We hope that our approach will stimulate further research specifically directed at assumptions of these models.

APA, Harvard, Vancouver, ISO, and other styles

18

Kunakh, Olga, and Darya Kovalenko. "Fitting Competing Models of the Population Abundance Distribution: Land Snails from Nikopol Manganese Ore Basin Technosols." Ekológia (Bratislava) 38, no. 4 (December 1, 2019): 367–81. http://dx.doi.org/10.2478/eko-2019-0027.

Full text

Abstract:

AbstractThis paper examines the temporal dynamics of terrestrial mollusks of the Nikopol manganese ore basin technosols. The research was carried out at the Research Centre of the Dnipro Agrarian and Economic University in Pokrov (Ukraine). Sampling was carried out in 2012–2014 on four variants of artificial soil: formed on red-brown clays, on loess-like loams, on gray-green clays, and on humus-rich layer. The distribution of the number of individuals in a mollusk population was described by broken stick, Motomura, log-normal, Zipf, and Zipf-Mandelbrot models. It was shown that the series of models that best describe mollusk abundance distribution is specific for a particular species and technosols type and generally is invariant over time.

APA, Harvard, Vancouver, ISO, and other styles

19

Visser, Hans. "The limits of economic theories and models." Central European Review of Economics and Management 4, no. 4 (December 17, 2020): 47–68. http://dx.doi.org/10.29015/cerem.887.

Full text

Abstract:

Aim: This article was written out of a felt need to reflect on the relationship between economic theories and models on the one hand and the empirical world as we experience it on the other. The question is in particular whether it is possible for economic models and theories to say anything definitive about the world we live in. Design/Research methods: The article relies on professional publications, both within the field of economics and outside of it. Conclusions/findings: There is much reason for humility, economic models and theories have hardly anything definitive to say about the empirical world, and there is a need for a more varied menu of theories and models and for a listening ear for the needs and fears of the population at large. The best we can do is discussing competing and conflicting views in a polite way. However, this requires a Sprachethik that looks more and more like an endangered species. Originality/value of the article: Recent developments concerning the reach of economic models and theories are related to earlier discussions and a way forward is sketched

APA, Harvard, Vancouver, ISO, and other styles

20

Rahbek, Carsten, Nicholas J. Gotelli, Robert K. Colwell, Gary L. Entsminger, Thiago Fernando L. V. B. Rangel, and Gary R. Graves. "Predicting continental-scale patterns of bird species richness with spatially explicit models." Proceedings of the Royal Society B: Biological Sciences 274, no. 1607 (October 20, 2006): 165–74. http://dx.doi.org/10.1098/rspb.2006.3700.

Full text

Abstract:

The causes of global variation in species richness have been debated for nearly two centuries with no clear resolution in sight. Competing hypotheses have typically been evaluated with correlative models that do not explicitly incorporate the mechanisms responsible for biotic diversity gradients. Here, we employ a fundamentally different approach that uses spatially explicit Monte Carlo models of the placement of cohesive geographical ranges in an environmentally heterogeneous landscape. These models predict species richness of endemic South American birds (2248 species) measured at a continental scale. We demonstrate that the principal single-factor and composite (species-energy, water-energy and temperature-kinetics) models proposed thus far fail to predict ( r 2 ⩽0.05) the richness of species with small to moderately large geographical ranges (first three range-size quartiles). These species constitute the bulk of the avifauna and are primary targets for conservation. Climate-driven models performed reasonably well only for species with the largest geographical ranges (fourth quartile) when range cohesion was enforced. Our analyses suggest that present models inadequately explain the extraordinary diversity of avian species in the montane tropics, the most species-rich region on Earth. Our findings imply that correlative climatic models substantially underestimate the importance of historical factors and small-scale niche-driven assembly processes in shaping contemporary species-richness patterns.

APA, Harvard, Vancouver, ISO, and other styles

21

MARVÁ, M., J. C. POGGIALE, and R. BRAVO DE LA PARRA. "REDUCTION OF SLOW–FAST PERIODIC SYSTEMS WITH APPLICATIONS TO POPULATION DYNAMICS MODELS." Mathematical Models and Methods in Applied Sciences 22, no. 10 (August 13, 2012): 1250025. http://dx.doi.org/10.1142/s021820251250025x.

Full text

Abstract:

This work deals with the approximate reduction of a nonautonomous two time scales ordinary differential equations system with periodic fast dynamics. We illustrate this technique with the analysis of two models belonging to different fields in ecology. On the one hand, we deal with a two patches periodic predator–prey model with a refuge for prey. Considering migrations between patches to be faster than local interaction allows us to study a three-dimensional system by means of a two-dimensional one. On the other hand, a two time scales periodic eco-epidemic model is addressed by considering two competing species, one of them being affected by a periodic SIR epidemic process which is faster than inter-species interactions. The difference between time scales allows us to study the asymptotic behavior of the four-dimensional system by means of a planar, reduced one. Furthermore, we propose a methodology straightforwardly applicable to a very large class of two time scales periodic systems.

APA, Harvard, Vancouver, ISO, and other styles

22

Lester, Rebecca E., Ian T. Webster, Peter G. Fairweather, and William J. Young. "Linking water-resource models to ecosystem-response models to guide water-resource planning - an example from the Murray - Darling Basin, Australia." Marine and Freshwater Research 62, no. 3 (2011): 279. http://dx.doi.org/10.1071/mf09298.

Full text

Abstract:

Objectively assessing ecological benefits of competing watering strategies is difficult. We present a framework of coupled models to compare scenarios, using the Coorong, the estuary for the Murray–Darling River system in South Australia, as a case study. The framework links outputs from recent modelling of the effects of climate change on water availability across the Murray–Darling Basin to a hydrodynamic model for the Coorong, and then an ecosystem-response model. The approach has significant advantages, including the following: (1) evaluating management actions is straightforward because of relatively tight coupling between impacts on hydrology and ecology; (2) scenarios of 111 years reveal the impacts of realistic climatic and flow variability on Coorong ecology; and (3) ecological impact is represented in the model by a series of ecosystem states, integrating across many organisms, not just iconic species. We applied the approach to four flow scenarios, comparing conditions without development, current water-use levels, and two predicted future climate scenarios. Simulation produced a range of hydrodynamic conditions and consequent distributions of ecosystem states, allowing managers to compare scenarios. This approach could be used with many climates and/or management actions for optimisation of flow delivery to environmental assets.

APA, Harvard, Vancouver, ISO, and other styles

23

Munteanu, Florian. "A study of a three-dimensional competitive Lotka–Volterra system." ITM Web of Conferences 34 (2020): 03010. http://dx.doi.org/10.1051/itmconf/20203403010.

Full text

Abstract:

In this paper we will consider a community of three mutually competing species modeled by the Lotka–Volterra system: $$ {\left\{ {\dot x} \right._i} = {x_i}\left( {{b_i} - \sum\limits_{i = 1}^3 {{a_{ij}}{x_j}} } \right),i = 1,2,3 $$ where xi(t) is the population size of the i-th species at time t, Ẋi denote $${{dxi} \over {dt}}$$ and aij, bi are all strictly positive real numbers. This system of ordinary diﬀerential equations represent a class of Kolmogorov systems. This kind of systems is widely used in the mathematical models for the dynamics of population, like predator-prey models or diﬀerent models for the spread of diseases. A qualitative analysis of this Lotka-Volterra system based on dynamical systems theory will be performed, by studying the local behavior in equilibrium points and obtaining local dynamics properties.

APA, Harvard, Vancouver, ISO, and other styles

24

Tucker, Anton D., Colin J. Limpus, Keith R. McDonald, and Hamish I. McCallum. "Growth dynamics of freshwater crocodiles (Crocodylus johnstoni) in the Lynd River, Queensland." Australian Journal of Zoology 54, no. 6 (2006): 409. http://dx.doi.org/10.1071/zo06099.

Full text

Abstract:

We analysed growth models for a population of Australian freshwater crocodiles (Crocodylus johnstoni). Competing growth models were tested with two data sets: individuals of known-age, and growth interval data from capture-recapture records. A von Bertalanffy function provided the best empirical fit of several growth models. The estimated asymptotic lengths (snout–vent length of males = 125.3 cm; females = 97.4 cm) agreed well with average lengths of the ten largest males and females in the population. Sexual size dimorphism in this species resulted from a combination of smaller mean length at maturity for females and a subsequent decline in female growth rate. Size dimorphism may result from individual trade-offs in age v. length at maturity as a consequence of sexual selection.

APA, Harvard, Vancouver, ISO, and other styles

25

Wenger, Seth J., James T. Peterson, Mary C. Freeman, Byron J. Freeman, and D. David Homans. "Stream fish occurrence in response to impervious cover, historic land use, and hydrogeomorphic factors." Canadian Journal of Fisheries and Aquatic Sciences 65, no. 7 (July 2008): 1250–64. http://dx.doi.org/10.1139/f08-046.

Full text

Abstract:

We evaluated competing models explaining the occurrence of five stream fishes in an urbanizing watershed to determine the relative importance of (a) impervious surface and other indicators of current land use, (b) historic land use (e.g., agriculture, impoundments), and (c) hydrogeomorphic characteristics (e.g., stream size, elevation, geology). For four of five species, the best-supported models were those that included both current effective impervious cover and historic land use predictor variables, although models with only effective impervious cover were equally well supported for two of those species. For the best-supported models for three species, occurrence probability was predicted to approach zero at levels of development equivalent to about 2%–4% effective impervious cover in the surrounding region. Data were drawn from 357 fish collections made in the Etowah River basin, Georgia, USA, between 1998 and 2003 and analyzed using hierarchical logistic regression accounting for imperfect species detection. This is the first study we know of to examine the response of individual fish species to both increasing impervious cover and historic land use. Such individual species assessments will be increasingly necessary to guide policies for managing urban effects and preventing extirpations of sensitive species.

APA, Harvard, Vancouver, ISO, and other styles

26

Gourbiere, Sébastien, Pierre Auger, Jean Luc Chassé, and Bruno Faivre. "Extinction Waves in Spatial Population Dynamic Models — the Case of two Sibling Bird Species H. Icterina and H. Polygotta." Journal of Biological Systems 05, no. 03 (September 1997): 359–74. http://dx.doi.org/10.1142/s0218339097000229.

Full text

Abstract:

Two spatial models of populations dynamics are presented to study the evolution of spatial distributions of two sibling species. We defined firstly an interspecific competition model and secondly a one predator-two preys model. They are constituted of a two dimensional discrete set of cells.Initially, the two competing or prey species occupy two complementary areas with common zone and the predator is regularly distributed. Populations of each cell are assumed to firstly have local interactions of competition or selective predation and secondly disperse to the four nearest neighbouring cells. We establish a typology of spatial structures obtained from both interspecific competition and selective predation. These two types of interactions are able to create a sympatric zone and to cause its motion.

APA, Harvard, Vancouver, ISO, and other styles

27

Menden-Deuer, Susanne, Julie Rowlett, Medet Nursultanov, Sinead Collins, and Tatiana Rynearson. "Biodiversity of marine microbes is safeguarded by phenotypic heterogeneity in ecological traits." PLOS ONE 16, no. 8 (August 4, 2021): e0254799. http://dx.doi.org/10.1371/journal.pone.0254799.

Full text

Abstract:

Why, contrary to theoretical predictions, do marine microbe communities harbor tremendous phenotypic heterogeneity? How can so many marine microbe species competing in the same niche coexist? We discovered a unifying explanation for both phenomena by investigating a non-cooperative game that interpolates between individual-level competitions and species-level outcomes. We identified all equilibrium strategies of the game. These strategies represent the probability distribution of competitive abilities (e.g. traits) and are characterized by maximal phenotypic heterogeneity. They are also neutral towards each other in the sense that an unlimited number of species can co-exist while competing according to the equilibrium strategies. Whereas prior theory predicts that natural selection would minimize trait variation around an optimum value, here we obtained a mathematical proof that species with maximally variable traits are those that endure. This discrepancy may reflect a disparity between predictions from models developed for larger organisms in contrast to our microbe-centric model. Rigorous mathematics proves that phenotypic heterogeneity is itself a mechanistic underpinning of microbial diversity. This discovery has fundamental ramifications for microbial ecology and may represent an adaptive reservoir sheltering biodiversity in changing environmental conditions.

APA, Harvard, Vancouver, ISO, and other styles

28

Yoshioka, Hidekazu, and Yumi Yoshioka. "On a non-standard two-species stochastic competing system and a related degenerate parabolic equation." ANZIAM Journal 61 (June 7, 2020): C1—C14. http://dx.doi.org/10.21914/anziamj.v61i0.15040.

Full text

Abstract:

We propose and analyse a new stochastic competing two-species population dynamics model. Competing algae population dynamics in river environments, an important engineering problem, motivates this model. The algae dynamics are described by a system of stochastic differential equations with the characteristic that the two populations are competing with each other through the environmental capacities. Unique existence of the uniformly bounded strong solution is proven and an attractor is identified. The Kolmogorov backward equation associated with the population dynamics is formulated and its unique solvability in a Banach space with a weighted norm is discussed. Our mathematical analysis results can be effectively utilized for a foundation of modelling, analysis, and control of the competing algae population dynamics. References S. Cai, Y. Cai, and X. Mao. A stochastic differential equation SIS epidemic model with two correlated brownian motions. Nonlin. Dyn., 97(4):2175–2187, 2019. doi:10.1007/s11071-019-05114-2. S. Cai, Y. Cai, and X. Mao. A stochastic differential equation SIS epidemic model with two independent brownian motions. J. Math. Anal. App., 474(2):1536–1550, 2019. doi:10.1016/j.jmaa.2019.02.039. U. Callies, M. Scharfe, and M. Ratto. Calibration and uncertainty analysis of a simple model of silica-limited diatom growth in the Elbe river. Ecol. Mod., 213(2):229–244, 2008. doi:10.1016/j.ecolmodel.2007.12.015. M. G. Crandall, H. Ishii, and P. L. Lions. User's guide to viscosity solutions of second order partial differential equations. Bull. Am. Math. Soc., 27(1):229–244, 1992. doi:10.1090/S0273-0979-1992-00266-5. N. H. Du and V. H. Sam. Dynamics of a stochastic Lotka–Volterra model perturbed by white noise. J. Math. Anal. App., 324(1):82–97, 2006. doi:10.1016/j.jmaa.2005.11.064. P. Grandits, R. M. Kovacevic, and V. M. Veliov. Optimal control and the value of information for a stochastic epidemiological SIS model. J. Math. Anal. App., 476(2):665–695, 2019. doi:10.1016/j.jmaa.2019.04.005. B. Horvath and O. Reichmann. Dirichlet forms and finite element methods for the SABR model. SIAM J. Fin. Math., 9(2):716–754, 2018. doi:10.1137/16M1066117. J. Hozman and T. Tichy. DG framework for pricing european options under one-factor stochastic volatility models. J. Comput. Appl. Math., 344:585–600, 2018. doi:10.1016/j.cam.2018.05.064. G. Lan, Y. Huang, C. Wei, and S. Zhang. A stochastic SIS epidemic model with saturating contact rate. Physica A, 529(121504):1–14, 2019. doi:10.1016/j.physa.2019.121504. J. L. Lions and E. Magenes. Non-homogeneous Boundary Value Problems and Applications (Vol. 1). Springer Berlin Heidelberg, 1972. doi:10.1007/978-3-642-65161-8. J. Lv, X. Zou, and L. Tian. A geometric method for asymptotic properties of the stochastic Lotka–Volterra model. Commun. Nonlin. Sci. Numer. Sim., 67:449–459, 2019. doi:10.1016/j.cnsns.2018.06.031. S. Morin, M. Coste, and F. Delmas. A comparison of specific growth rates of periphytic diatoms of varying cell size under laboratory and field conditions. Hydrobiologia, 614(1):285–297, 2008. doi:10.1007/s10750-008-9513-y. B. \T1\O ksendal. Stochastic Differential Equations. Springer Berlin Heidelberg, 2003. doi:10.1007/978-3-642-14394-6. O. Oleinik and E. V. Radkevic. Second-order Equations with Nonnegative Characteristic Form. Springer Boston, 1973. doi:10.1007/978-1-4684-8965-1. S. Peng. Nonlinear Expectations and Stochastic Calculus under Uncertainty: with Robust CLT and G-Brownian Motion. Springer-Verlag Berlin Heidelberg, 2019. doi:10.1007/978-3-662-59903-7. T. S. Schmidt, C. P. Konrad, J. L. Miller, S. D. Whitlock, and C. A. Stricker. Benthic algal (periphyton) growth rates in response to nitrogen and phosphorus: parameter estimation for water quality models. J. Am. Water Res. Ass., 2019. doi:10.1111/1752-1688.12797. Y. Toda and T. Tsujimoto. Numerical modeling of interspecific competition between filamentous and nonfilamentous periphyton on a flat channel bed. Landscape Ecol. Eng., 6(1):81–88, 2010. doi:10.1007/s11355-009-0093-4. H. Yoshioka, Y. Yaegashi, Y. Yoshioka, and K. Tsugihashi. Optimal harvesting policy of an inland fishery resource under incomplete information. Appl. Stoch. Models Bus. Ind., 35(4):939–962, 2019. doi:10.1002/asmb.2428.

APA, Harvard, Vancouver, ISO, and other styles

29

Hincal, Evren, Shorsh Mohammed, and Bilgen Kaymakamzade. "Stability analysis of an ecoepidemiological model consisting of a prey and tow competing predators with Si-disease in prey and toxicant." BULLETIN OF THE KARAGANDA UNIVERSITY-MATHEMATICS 99, no. 3 (September 30, 2020): 55–61. http://dx.doi.org/10.31489/2020m3/55-61.

Full text

Abstract:

In the present paper, we study two eco-epidemiological models. The first one consists of a prey and two competing predators with SI-disease in prey species spreading by contacts between susceptible prey and infected prey. This model assumes linear functional response. The second model is the modification of the first one when the effect of toxicant is taken into account. In this paper, we examine the dynamical behavior of non-survival and free equilibrium points of our proposed model.

APA, Harvard, Vancouver, ISO, and other styles

30

Kunakh, O. N., S. S. Kramarenko, A. V. Zhukov, A. S. Kramarenko, and N. V. Yorkina. "Fitting competing models and evaluation of model parameters of the abundance distribution of the land snail Vallonia pulchella (Pulmonata, Valloniidae)." Regulatory Mechanisms in Biosystems 9, no. 2 (April 25, 2018): 198–202. http://dx.doi.org/10.15421/021829.

Full text

Abstract:

This paper summarizes the mechanisms behind the patterning of the intra-population abundance distribution of the land snail Vallonia pulchella (Müller, 1774). The molluscs were collected in recultivated soil formed on red-brown clays (Pokrov, Ukraine). Data obtained in this study reveal that V. pulchella population abundance ranges from 1 to 13 individuals per 100 g of soil sample. To obtain estimates of the mean, three models were used: the model of the arithmetic mean, the Poisson model and a log-normal model. The arithmetic mean of the occurrence of this species during the study period was 1.84 individuals/sample. Estimation of the average number of molluscs in one sample calculated using the Poisson model is lower and equals 1.40 individuals/sample. The distribution of the number of individuals in a population was described by the graphics "rank – abundance". The individual sample plot sites with molluscs may be regarded as equivalents of individual species in the community. For the analysis, the following models were used: broken sticks model, niche preemption model, log-normal model, Zipf model, and Zipf-Mandelbrot model. Applying the log-normal distribution gives a lower estimate of the mean density at 1.28 individuals/sample. Median value and mode is estimated at 1.00 individuals/sample. The Zipf-Mandelbrot model was shown as the most adequate to describe distribution of the V. pulchella population within the study area. The Zipf-Mandelbrot model belongs to the family of so-called non-Gaussian distributions. This means that the sample statistics do not possess asymptotic properties and by increasing the sample size, they tend to infinity, and are not close to the values of the general population. Therefore, the average value of the random variable that describes the non-Gaussian distribution has no statistical meaning. From an environmental point of view, this means that within the study area the capacity of the habitat is large, and for some combination of environmental conditions the rapid growth of the abundance of a given species is possible.

APA, Harvard, Vancouver, ISO, and other styles

31

Cantrell, Robert Stephen. "Global higher bifurcations in coupled systems of nonlinear eigenvalue problems." Proceedings of the Royal Society of Edinburgh: Section A Mathematics 106, no. 1-2 (1987): 113–20. http://dx.doi.org/10.1017/s0308210500018242.

Full text

Abstract:

SynopsisCoexistent steady-state solutions to a Lotka–Volterra model for two freely-dispersing competing species have been shown by several authors to arise as global secondary bifurcation phenomena. In this paper we establish conditions for the existence of global higher dimensional n-ary bifurcation in general systems of multiparameter nonlinear eigenvalue problems which preserve the coupling structure of diffusive steady-state Lotka–Volterra models. In establishing our result, we mainly employ the recently-developed multidimensional global multiparameter theory of Alexander–Antman. Conditions for ternary steady-state bifurcation in the three species diffusive competition model are given as an application of the result.

APA, Harvard, Vancouver, ISO, and other styles

32

Rheims, Cristina, Bernhard Huber, and Antonio Brescovit. "Exaggerated female genitalia in two new spider species (Araneae: Pholcidae), with comments on genital evolution by female choice versus antagonistic coevolution." Insect Systematics & Evolution 36, no. 3 (2005): 285–92. http://dx.doi.org/10.1163/187631205788838375.

Full text

Abstract:

AbstractTwo new species are described that are remarkable in having exaggerated female genitalia: Mesabolivar samatiaguassu sp. n. and M. cuarassu sp. n.. Comparative evidence as well as size measurements of male and female structures suggest that the exaggerated female external genitalia correlate functionally with elongated male cheliceral apophyses. These morphological findings are discussed in the light of competing models of genital evolution. Luring mating acts, female cooperative behaviour and morphology, as well as the probable costs associated with the female structures argue against the antagonistic coevolution model and favour sexual selection by cryptic female choice.

APA, Harvard, Vancouver, ISO, and other styles

33

Pacciani-Mori, Leonardo, Samir Suweis, Amos Maritan, and Andrea Giometto. "Constrained proteome allocation affects coexistence in models of competitive microbial communities." ISME Journal 15, no. 5 (January 11, 2021): 1458–77. http://dx.doi.org/10.1038/s41396-020-00863-0.

Full text

Abstract:

AbstractMicrobial communities are ubiquitous and play crucial roles in many natural processes. Despite their importance for the environment, industry and human health, there are still many aspects of microbial community dynamics that we do not understand quantitatively. Recent experiments have shown that the structure and composition of microbial communities are intertwined with the metabolism of the species that inhabit them, suggesting that properties at the intracellular level such as the allocation of cellular proteomic resources must be taken into account when describing microbial communities with a population dynamics approach. In this work, we reconsider one of the theoretical frameworks most commonly used to model population dynamics in competitive ecosystems, MacArthur’s consumer-resource model, in light of experimental evidence showing how proteome allocation affects microbial growth. This new framework allows us to describe community dynamics at an intermediate level of complexity between classical consumer-resource models and biochemical models of microbial metabolism, accounting for temporally-varying proteome allocation subject to constraints on growth and protein synthesis in the presence of multiple resources, while preserving analytical insight into the dynamics of the system. We first show with a simple experiment that proteome allocation needs to be accounted for to properly understand the dynamics of even the simplest microbial community, i.e. two bacterial strains competing for one common resource. Then, we study our consumer-proteome-resource model analytically and numerically to determine the conditions that allow multiple species to coexist in systems with arbitrary numbers of species and resources.

APA, Harvard, Vancouver, ISO, and other styles

34

Barbosa, Lorena Oliveira, Emanuel Arnoni Costa, Cristine Tagliapietra Schons, César Augusto Guimarães Finger, Veraldo Liesenberg, and Polyanna da Conceição Bispo. "Individual Tree Basal Area Increment Models for Brazilian Pine (Araucaria angustifolia) Using Artificial Neural Networks." Forests 13, no. 7 (July 15, 2022): 1108. http://dx.doi.org/10.3390/f13071108.

Full text

Abstract:

This research aimed to develop statistical models to predict basal area increment (BAI) for Araucaria angustifolia using Artificial Neural Networks (ANNs). Tree species were measured for their biometric variables and identified at the species level. The data were subdivided into three groups: (1) intraspecific competition with A. angustifolia; (2) the first group of species that causes interspecific competition with A. angustifolia; and (3) the second group of species that causes interspecific competition with A. angustifolia. We calculated both the dependent and independent distance and the described competition indices, considering the impact of group stratification. Multi-layer Perceptron (MLP) ANN was structured for modeling. The main results were that: (i) the input variables size and competition were the most significant, allowing us to explain up to 77% of the A. angustifolia BAI variations; (ii) the spatialization of the competing trees contributed significantly to the representation of the competitive status; (iii) the separate variables for each competition group improved the performance of the models; and (iv) besides the intraspecific competition, the interspecific competition also proved to be important to consider. The ANN developed showed precision and generalization, suggesting it could describe the increment of a species common in native forests in Southern Brazil and with potential for upcoming forest management initiatives.

APA, Harvard, Vancouver, ISO, and other styles

35

Ghosh, Preetam, Pratip Rana, Vijayaraghavan Rangachari, Jhinuk Saha, Edward Steen, and Ashwin Vaidya. "A game-theoretic approach to deciphering the dynamics of amyloid- β aggregation along competing pathways." Royal Society Open Science 7, no. 4 (April 2020): 191814. http://dx.doi.org/10.1098/rsos.191814.

Full text

Abstract:

Aggregation of amyloid- β (A β ) peptides is a significant event that underpins Alzheimer's disease (AD). A β aggregates, especially the low-molecular weight oligomers, are the primary toxic agents in AD pathogenesis. Therefore, there is increasing interest in understanding their formation and behaviour. In this paper, we use our previously established results on heterotypic interactions between A β and fatty acids (FAs) to investigate off-pathway aggregation under the control of FA concentrations to develop a mathematical framework that captures the mechanism. Our framework to define and simulate the competing on- and off-pathways of A β aggregation is based on the principles of game theory. Together with detailed simulations and biophysical experiments, our models describe the dynamics involved in the mechanisms of A β aggregation in the presence of FAs to adopt multiple pathways. Specifically, our reduced-order computations indicate that the emergence of off- or on-pathway aggregates are tightly controlled by a narrow set of rate constants, and one could alter such parameters to populate a particular oligomeric species. These models agree with the detailed simulations and experimental data on using FA as a heterotypic partner to modulate the temporal parameters. Predicting spatio-temporal landscape along competing pathways for a given heterotypic partner such as lipids is a first step towards simulating scenarios in which the generation of specific ‘conformer strains’ of A β could be predicted. This approach could be significant in deciphering the mechanisms of amyloid aggregation and strain generation, which are ubiquitously observed in many neurodegenerative diseases.

APA, Harvard, Vancouver, ISO, and other styles

36

Sneddon, Lynne U. "Evolution of nociception and pain: evidence from fish models." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1785 (September 23, 2019): 20190290. http://dx.doi.org/10.1098/rstb.2019.0290.

Full text

Abstract:

In order to survive, animals must avoid injury and be able to detect potentially damaging stimuli via nociceptive mechanisms. If the injury is accompanied by a negative affective component, future behaviour should be altered and one can conclude the animal experienced the discomfort associated with pain. Fishes are the most successful vertebrate group when considering the number of species that have filled a variety of aquatic niches. The empirical evidence for nociception in fishes from the underlying molecular biology, neurobiology and anatomy of nociceptors through to whole animal behavioural responses is reviewed to demonstrate the evolutionary conservation of nociception and pain from invertebrates to vertebrates. Studies in fish have shown that the biology of the nociceptive system is strikingly similar to that found in mammals. Further, potentially painful events result in behavioural and physiological changes such as reduced activity, guarding behaviour, suspension of normal behaviour, increased ventilation rate and abnormal behaviours which are all prevented by the use of pain-relieving drugs. Fish also perform competing tasks less well when treated with a putative painful stimulus. Therefore, there is ample evidence to demonstrate that it is highly likely that fish experience pain and that pain-related behavioural changes are conserved across vertebrates. This article is part of the Theo Murphy meeting issue ‘Evolution of mechanisms and behaviour important for pain’.

APA, Harvard, Vancouver, ISO, and other styles

37

Alsolami, Abdulrahman Ali, and Miled El Hajji. "Mathematical Analysis of a Bacterial Competition in a Continuous Reactor in the Presence of a Virus." Mathematics 11, no. 4 (February 9, 2023): 883. http://dx.doi.org/10.3390/math11040883.

Full text

Abstract:

In this paper, we discuss the competition of two species for a single essential growth-limiting nutriment with viral infection that affects only the first species. Although the classical models without viral infection suggest competitive exclusion, this model exhibits the stable coexistence of both species. We reduce the fourth-dimension proposed model to a three-dimension one. Thus, the coexistence of the two competing species is demonstrated using the theory of uniform persistence applied to the three-variable reduced system. We prove that there is no coexistence of both species without the presence of the virus and the satisfaction of some assumptions on the growth rates of species. Finally, we give some numerical simulations to confirm the obtained theoretical findings.

APA, Harvard, Vancouver, ISO, and other styles

38

Calkin, David E., Claire A. Montgomery, Nathan H. Schumaker, Stephen Polasky, Jeffrey L. Arthur, and Darek J. Nalle. "Developing a production possibility set of wildlife species persistence and timber harvest value." Canadian Journal of Forest Research 32, no. 8 (August 1, 2002): 1329–42. http://dx.doi.org/10.1139/x02-056.

Full text

Abstract:

An integrated model, combining spatial wildlife population and timber harvest and growth models, was developed to explore tradeoffs between the likelihood of persistence of a wildlife species, the northern flying squirrel (Glaucomys sabrinus), and timber production on a landscape on the west side of the Oregon Cascade Range. A simplified wildlife model was developed from the fully parameterized spatial wildlife model, using a habitat neighborhood-weighting scheme, for use in the optimization. Simulated annealing, a heuristic optimization technique, was used to solve for harvest schedules that maximized the net present value of timber harvest subject to a target value for likelihood of species persistence over a 100-year planning period. By solving this problem for a range of species persistence targets, a production possibility frontier was developed that showed tradeoffs between timber harvest value and likelihood of species persistence on this landscape. Although the results are specific to the wildlife species and the landscape analyzed, the approach is general and provides a structure for future models that will help land managers and forest planners to understand tradeoffs among competing resource uses.

APA, Harvard, Vancouver, ISO, and other styles

39

Luiselli, Luca. "Site occupancy and density of sympatric Gaboon viper (Bitis gabonica) and nose-horned viper (Bitis nasicornis)." Journal of Tropical Ecology 22, no. 5 (July 27, 2006): 555–64. http://dx.doi.org/10.1017/s0266467406003397.

Full text

Abstract:

The presence and density of two sympatric, large-sized vipers (the Gaboon viper, Bitis gabonica and the nose-horned viper, Bitis nasicornis) were studied along several transects, during both dry and wet seasons, and at different times of day, in southern Nigeria (West Africa). Three habitat types were found along the various transects (mature rain forest (MF), secondary rain forest (SF), swamp forest (SW)). The detection probabilities for these vipers were modelled with a set of competing models, and the various models were ordered by Akaike Information Criterion procedures. Two classes of models were used: the single-season model, and the multi-species model. The best models (single-season model) suggested that: for the Gaboon viper, habitat types SF and SW were particularly important in detecting this species, especially during the rainy season at 08h00–16h00. For nose-horned vipers, the best models had SW and MF as site-covariates. Application of the multi-species model revealed that there were different detection functions if both species are present at a site, with a ‘negative’ interaction of occupancy between the species. Females and males were similarly detectable in a logistic regression model, but feeding status and pregnancy slightly increased detection probability in a logistic regression model. Viper density was modelled by a DISTANCE sampling procedure. The density of one species tended to be inversely correlated to the density of the other, suggesting that (1) the rain-forest environment does not support abundant populations of both vipers when sympatric, and (2) the two Bitis species subtly partition the habitat resources.

APA, Harvard, Vancouver, ISO, and other styles

40

Warnock, Rachel C. M., Ziheng Yang, and Philip C. J. Donoghue. "Testing the molecular clock using mechanistic models of fossil preservation and molecular evolution." Proceedings of the Royal Society B: Biological Sciences 284, no. 1857 (June 21, 2017): 20170227. http://dx.doi.org/10.1098/rspb.2017.0227.

Full text

Abstract:

Molecular sequence data provide information about relative times only, and fossil-based age constraints are the ultimate source of information about absolute times in molecular clock dating analyses. Thus, fossil calibrations are critical to molecular clock dating, but competing methods are difficult to evaluate empirically because the true evolutionary time scale is never known. Here, we combine mechanistic models of fossil preservation and sequence evolution in simulations to evaluate different approaches to constructing fossil calibrations and their impact on Bayesian molecular clock dating, and the relative impact of fossil versus molecular sampling. We show that divergence time estimation is impacted by the model of fossil preservation, sampling intensity and tree shape. The addition of sequence data may improve molecular clock estimates, but accuracy and precision is dominated by the quality of the fossil calibrations. Posterior means and medians are poor representatives of true divergence times; posterior intervals provide a much more accurate estimate of divergence times, though they may be wide and often do not have high coverage probability. Our results highlight the importance of increased fossil sampling and improved statistical approaches to generating calibrations, which should incorporate the non-uniform nature of ecological and temporal fossil species distributions.

APA, Harvard, Vancouver, ISO, and other styles

41

Northfield, Tobin D., Susan G. W. Laurance, Margaret M. Mayfield, Dean R. Paini, William E. Snyder, Daniel B. Stouffer, Jeffrey T. Wright, and Lori Lach. "Native turncoats and indirect facilitation of species invasions." Proceedings of the Royal Society B: Biological Sciences 285, no. 1871 (January 24, 2018): 20171936. http://dx.doi.org/10.1098/rspb.2017.1936.

Full text

Abstract:

At local scales, native species can resist invasion by feeding on and competing with would-be invasive species. However, this relationship tends to break down or reverse at larger scales. Here, we consider the role of native species as indirect facilitators of invasion and their potential role in this diversity-driven ‘invasion paradox’. We coin the term ‘native turncoats’ to describe native facilitators of non-native species and identify eight ways they may indirectly facilitate species invasion. Some are commonly documented, while others, such as indirect interactions within competitive communities, are largely undocumented in an invasion context. Therefore, we use models to evaluate the likelihood that these competitive interactions influence invasions. We find that native turncoat effects increase with the number of resources and native species. Furthermore, our findings suggest the existence, abundance and effectiveness of native turncoats in a community could greatly influence invasion success at large scales.

APA, Harvard, Vancouver, ISO, and other styles

42

da S Costa, Michel Iskin, and Lucas Dos Anjos. "The interplay between fishery yield and top predator culling in a multispecies fishery context." Mathematical Medicine and Biology: A Journal of the IMA 37, no. 3 (January 11, 2020): 351–63. http://dx.doi.org/10.1093/imammb/dqz017.

Full text

Abstract:

Abstract In food webs, fishery can play the role of top predator, competing thus with other top predators for valuable food resources. In this view, it has been claimed in fisheries management that culling of top predators can be a means to improve fishery yield. To investigate this hypothesis, we use theoretical population models to assess in a multispecies context how fishery yield from target species harvest responds to top predator cull. Defying crisp summary, the four analysed food web models show that this response may be either positive or negative or both, indicating that in terms of multispecies fishery management the harvest yield may not accrue as a consequence of predator removal. In addition, this multitude of behaviours points also to the fact that the response of fishery yield to top predator cull may be difficult to assess.

APA, Harvard, Vancouver, ISO, and other styles

43

Canham, Charles D., Philip T. LePage, and K. Dave Coates. "A neighborhood analysis of canopy tree competition: effects of shading versus crowding." Canadian Journal of Forest Research 34, no. 4 (April 1, 2004): 778–87. http://dx.doi.org/10.1139/x03-232.

Full text

Abstract:

We have developed extensions of traditional distance-dependent, spatial competition analyses that estimate the magnitude of the competitive effects of neighboring trees on target tree growth as a function of the species, size, and distance to neighboring trees. Our analyses also estimate inter- and intra-specific competition coefficients and explicitly partition the competitive effects of neighbors into the effects of shading versus crowding. We tested the method using data from forests of northern, interior British Columbia dominated by western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don). For both species, the most parsimonious regression models included terms for the effects of tree size, crowding, and shading and separate competitive effects of four different groups of competing species. The models explained 33%59% of the variation in radial growth of the two species. For both species, growth declined more steeply as a function of crowding than shading. There was striking asymmetry in the strength of interspecific competition between hemlock and redcedar, with crowding by hemlock having a strong per capita effect on redcedar, while crowding by redcedar had relatively little effect on the radial growth of hemlock.

APA, Harvard, Vancouver, ISO, and other styles

44

Ekama, G. A., M. C. Wentzel, and R. E. Loewenthal. "Integrated chemical–physical processes kinetic modelling of multiple mineral precipitation problems." Water Science and Technology 53, no. 12 (June 1, 2006): 65–73. http://dx.doi.org/10.2166/wst.2006.407.

Full text

Abstract:

A three-phase (aqueous/gas/solid) mixed weak acid/base chemistry kinetic model is applied to evaluate the processes operative in the aeration treatment of swine wastewater (SWW) and sewage sludge anaerobic digester liquor (ADL). In both applications, with a single set of constants (except for the aeration rates which are situation specific), close correlation could be obtained between predicted and measured data, except for the Ca concentration–time profile in the SWW. For this wastewater, the model application highlighted an inconsistency in the measured Ca data which could not be resolved; this illustrates the value of a mass balance-based model in evaluating experimental data. From the model applications, in both wastewaters the dominant minerals precipitating are struvite and amorphous calcium phosphate (ACP), which precipitate simultaneously competing for the same species, P. The absolute and relative masses of the two precipitants are governed by the initial solution state (e.g. total inorganic C (CT), Mg, Ca and P concentrations), their relative precipitation rates (struvite > ACP) and the system conditions imposed (aeration rates and time applied). It is concluded that the kinetic model is able to predict correctly the time-dependent weak acid/base chemistry reactions and final equilibrium state for situations where multiple minerals competing for the same species precipitate simultaneously or sequentially, a deficiency in traditional equilibrium chemistry-based algebraic models.

APA, Harvard, Vancouver, ISO, and other styles

45

Haddow, K. A., D. J. King, D. A. Pouliot, D. G. Pitt, and F. W. Bell. "Early regeneration conifer identification and competition cover assessment using airborne digital camera imagery." Forestry Chronicle 76, no. 6 (December 1, 2000): 915–28. http://dx.doi.org/10.5558/tfc76915-6.

Full text

Abstract:

The potential of low cost, high-resolution airborne digital camera imagery for use in early stage forest regeneration assessment was investigated. Airborne imagery with 2.5-cm pixel size was acquired near Sault Ste. Marie, Ontario, over a forest vegetation management research site to: i) evaluate capabilities for identification and stem counting of two-year old conifer crop species under leaf-off and leaf-on conditions using classification of spectral and textural image information, and ii) develop models relating vegetation cover parameters to image spectral and texture information. Results indicate strong potential for identification and counting of conifer trees when competing vegetation cover is low or in leaf-off condition. However, systematic decreases in class separability and conifer count accuracy were observed with increasing competition. In image modelling of competition Leaf Area Index and Cover, statistically significant relations were found using primarily spectral measures. Stratification by competition species improved model fits and included texture measures in some models. Key words: airborne remote sensing, forest vegetation management, regeneration, digital cameras, leaf area index, cover, tree classification

APA, Harvard, Vancouver, ISO, and other styles

46

Kirkmeyer, Brian P., Robert A. Weiss, and Karen I. Winey. "Imaging Ionic Aggregates in Zn-Neutralized Sulfonated Polystyrene Ionomers: Shape and Spatial Heterogeneity." Microscopy and Microanalysis 6, S2 (August 2000): 1112–13. http://dx.doi.org/10.1017/s1431927600038058.

Full text

Abstract:

Ionomers are ionically-associating copolymers whose distinctive rheological and mechanical properties arise from the formation of ionic aggregates. The ionic aggregates form when dipoles of minority anionic polymer backbone segments and cationic neutralizing species locally associate and dissociate among each other. Specific ionomer properties depend upon the base copolymer, the minority constituent and the neutralizing agent. One system that has been studied extensively is sulfonated polystyrene ionomer neutralized with Zn (Zn-SPS). The most common technique to date for studying ionomer morphology is small-angle x-ray scattering (SAXS). This technique has provided quantitative information about the aggregate morphology by imposing morphology models that have not been independently confirmed.In the present study, we demonstrate the capability to directly image the ionic aggregates of Zn-SPS ionomers using scanning transmission electron microscopy (STEM). This method will allow us to confirm or deny the competing morphological models applied to SAXS data. We have applied similar methods to polyethylene-based ionomers.

APA, Harvard, Vancouver, ISO, and other styles

47

Namba, Toshiyuki, Yasuhiro Takeuchi, and Malay Banerjee. "Stabilizing effect of intra-specific competition on prey-predator dynamics with intraguild predation." Mathematical Modelling of Natural Phenomena 13, no. 3 (2018): 29. http://dx.doi.org/10.1051/mmnp/2018033.

Full text

Abstract:

Multi-species population models with various types of interactions are important to understand the stable coexistence of prey and predator species and the role of various factors leading to complex dynamics and extinction of one or more species. Models of two predators sharing one prey population are analyzed by some researchers and the role of nonlinear functional responses and interaction strengths are reported to be responsible for the stable coexistence of three species. However, one-prey-two-predator models with intraguild predation have received relatively less attention from researchers. Recent literature on this topic mainly focused on the study of local and global stability properties of possible equilibria and appearance of various types of bifurcations. Intra-specific competition among predator species is an important factor for coexistence of more than one predator species competing for one shared prey. Hence it is quite essential to understand the role of intra-specific competition on the stability and bifurcation behavior. In this work we wish to demonstrate the stabilizing role of intra-specific competition among intermediate and top predators when the growth rate of prey species is adequate to support both the predator species. With the help of stability and bifurcation analysis we show the stabilizing role of intra-specific competition among predators. Moreover, strong self-regulation in intraguild predator prevents extinction of intraguild prey at high productivity and resolve the contradiction between empirical and previous theoretical results on the fate of intraguild prey at high productivity. To establish our claim we present, apart from analytical results, extensive numerical simulation results and couple of bifurcation diagrams.

APA, Harvard, Vancouver, ISO, and other styles

48

Chock, Rachel Y., Debra M. Shier, and Gregory F. Grether. "Niche partitioning in an assemblage of granivorous rodents, and the challenge of community-level conservation." Oecologia 198, no. 2 (January 15, 2022): 553–65. http://dx.doi.org/10.1007/s00442-021-05104-5.

Full text

Abstract:

AbstractCoexistence of competing species in the same foraging guild has long puzzled ecologists. In particular, how do small subordinate species persist with larger dominant competitors? This question becomes particularly important when conservation interventions, such as reintroduction or translocation, become necessary for the smaller species. Exclusion of dominant competitors might be necessary to establish populations of some endangered species. Ultimately, however, the goal should be to conserve whole communities. Determining how subordinate species escape competitive exclusion in intact communities could inform conservation decisions by clarifying the ecological conditions and processes required for coexistence at local or regional scales. We tested for spatial and temporal partitioning among six species of native, granivorous rodents using null models, and characterized the microhabitat of each species using resource-selection models. We found that the species’ nightly activity patterns are aggregated temporally but segregated spatially. As expected, we found clear evidence that the larger-bodied kangaroo rats drive spatial partitioning, but we also found species-specific microhabitat associations, which suggests that habitat heterogeneity is part of what enables these species to coexist. Restoration of natural disturbance regimes that create habitat heterogeneity, and selection of translocation sites without specific competitors, are among the management recommendations to consider in this case. More generally, this study highlights the need for a community-level approach to conservation and the usefulness of basic ecological data for guiding management decisions.

APA, Harvard, Vancouver, ISO, and other styles

49

Vasilyeva, Maria, Youwen Wang, Sergei Stepanov, and Alexey Sadovski. "Numerical Investigation and Factor Analysis of the Spatial-Temporal Multi-Species Competition Problem." WSEAS TRANSACTIONS ON MATHEMATICS 21 (November 4, 2022): 731–55. http://dx.doi.org/10.37394/23206.2022.21.85.

Full text

Abstract:

This work considers the spatial-temporal multispecies competition model. A mathematical model is described by a coupled system of nonlinear diffusion reaction equations. We use a finite volume approximation with semi-implicit time approximation for the numerical solution of the model with corresponding boundary and initial conditions. To understand the effect of the diffusion to solution in one and two-dimensional formulations, we present numerical results for several cases of the parameters related to the survival scenarios. We control all non-diffusion parameters, including reproductive growth rate, competition rate, and initial condition of population density of competing species, and compare the dynamic and equilibrium under regular diffusion rate and small diffusion rate; we found that competing species with small diffusion rate can reach a higher equilibrium over the whole geographic domain, but requires more time steps. The random initial conditions' effect on the time to reach equilibrium is investigated. We control other parameters and examine the impact of the initial condition of the species population; we found that regardless of the values of initial conditions in the system, competing species populations will arrive at an equilibrium point. The influence of diffusion on the survival scenarios is presented. We control other parameters and examine the effect of diffusion of species; we found that when the ratio of diffusion rates passes some thresholds, the survival status will change. In real-world problems, values of the parameters are usually unknown yet vary in some range. To evaluate the impact of parameters on the system stability, we simulate a spatialtemporal model with random parameters and perform factor analysis for two and threespecies competition models. From the perspective of the numerical experiment, we release control for all parameters and perform factor analysis on simulation results. We found that the initial population condition has a minimum effect on the final population, which aligns with the outcome of our controlled numerical experiment on the initial condition. Diffusion is the dominant factor when diffusion rates are on the same scale as other parameters. This dominant factor aligns with our controlled numerical experiment on diffusion rate, where the change in diffusion rate leads to different survival statuses of species. However, when diffusion rates are 1/10 on the scale of other parameters, reproductive growth rates and competition rates become the dominant factors.

APA, Harvard, Vancouver, ISO, and other styles

50

von Redwitz, Christoph, and Friederike de Mol. "The R Package PROSPER: An Environment for Modeling Weed Population Dynamics and the Evolution of Herbicide Resistance." Agronomy 10, no. 7 (July 3, 2020): 958. http://dx.doi.org/10.3390/agronomy10070958.

Full text

Abstract:

Weed management is a challenge for farmers worldwide, and the problem is exacerbated by the spread of weed herbicide resistance. Simulation models that combine population dynamics and genetics are valuable tools for predicting the impact of competing management options on weed density, allele frequency, and phenotypic resistance levels. The new R package PROSPER provides functions for the forward simulation of weed population dynamics on a field scale, the selection of individuals according to their sensitivity to herbicides, and the recombination of alleles during reproduction. Objects are provided to enter and save model parameters in a clear structure, and to save output data for further processing in R. The basic functions are extensible with R code. PROSPER combines individual-based population dynamics with monogenic or polygenic diploid inheritance and flexible selection pressure. Stochasticity can be included at all model steps. Two examples of the population dynamics of two annual weed species with herbicide resistance are presented. All parameters and the models are available in PROSPER. In addition to simulation, PROSPER is intended for sharing and publishing population dynamic parameters and models, which is easily done thanks to R.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Models for competing specie'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles