Harvesting of a single-species system incorporating stage structure and toxicity.
Herbivore harvesting and alternative steady states in coral reefs
Coral reefs can undergo relatively rapid changes in the dominant biota, a phenomenon referred to as phase shift. Degradation of coral reefs is often associated with changes in community structure towards a macroalgae-dominated reef ecosystem due to the reduction in herbivory caused by overfishing. We investigate the coral-macroalgal phase shift due to the effects of harvesting of herbivorous reef fish by means of a continuous time model in the food chain. Conditions for local asymptotic stability...
Homoclinic orbits in a two-patch predator-prey model with Preisach hysteresis operator
Systems of operator-differential equations with hysteresis operators can have unstable equilibrium points with an open basin of attraction. Such equilibria can have homoclinic orbits attached to them, and these orbits are robust. In this paper a population dynamics model with hysteretic response of the prey to variations of the predator is introduced. In this model the prey moves between two patches, and the derivative of the Preisach operator is used to describe the hysteretic flow between the...
Homogeneous Systems with a Quiescent Phase
Recently the effect of a quiescent phase (or dormant/resting phase in applications) on the dynamics of a system of differential equations has been investigated, in particular with respect to stability properties of stationary points. It has been shown that there is a general phenomenon of stabilization against oscillations which can be cast in rigorous form. Here we investigate, for homogeneous systems, the effect of a quiescent phase, and more generally, a phase with slower dynamics. We show that...
Hopf bifurcation for simple food chain model with delay.
Influence of diffusion on interactions between malignant gliomas and immune system
We analyse the influence of diffusion and space distribution of cells in a simple model of interactions between an activated immune system and malignant gliomas, among which the most aggressive one is GBM Glioblastoma Multiforme. It turns out that diffusion cannot affect stability of spatially homogeneous steady states. This suggests that there are two possible outcomes-the solution is either attracted by the positive steady state or by the semitrivial one. The semitrivial steady state describes...
Instability of traveling waves for a generalized diffusion model in population problems.
Internal exact controllability of the linear population dynamics with diffusion.
Iterates approaching hyperbolic manifolds of fixed points.
Iterative methods for generalized von Foerster equations with functional dependence.
Když se matematika potká s biologií: matematická ekologie
Článek se zabývá některými aplikacemi matematiky v ekologii. V historickém kontextu ukazuje, že jednak teoretické základy populační a evoluční ekologie využívají matematické metodologie založené na diferenciálních či diferenčních rovnicích, jednak ekologické problémy motivují vznik nových matematických disciplín, jako je např. evoluční teorie her.
Kermack-McKendrick epidemic model revisited
This paper proposes a stochastic diffusion model for the spread of a susceptible-infective-removed Kermack–McKendric epidemic (M1) in a population which size is a martingale that solves the Engelbert–Schmidt stochastic differential equation (). The model is given by the stochastic differential equation (M2) or equivalently by the ordinary differential equation (M3) whose coefficients depend on the size . Theorems on a unique strong and weak existence of the solution to (M2) are proved and computer...
Kermack-McKendrick epidemics vaccinated
This paper proposes a deterministic model for the spread of an epidemic. We extend the classical Kermack–McKendrick model, so that a more general contact rate is chosen and a vaccination added. The model is governed by a differential equation (DE) for the time dynamics of the susceptibles, infectives and removals subpopulation. We present some conditions on the existence and uniqueness of a solution to the nonlinear DE. The existence of limits and uniqueness of maximum of infected individuals are...
Large population limit and time behaviour of a stochastic particle model describing an age-structured population
We study a continuous-time discrete population structured by a vector of ages. Individuals reproduce asexually, age and die. The death rate takes interactions into account. Adapting the approach of Fournier and Méléard, we show that in a large population limit, the microscopic process converges to the measure-valued solution of an equation that generalizes the McKendrick-Von Foerster and Gurtin-McCamy PDEs in demography. The large deviations associated with this convergence are studied. The upper-bound...
Large time behavior in a density-dependent population dynamics problem with age structure and child care
Two asexual density-dependent population dynamics models with age-dependence and child care are presented. One of them includes the random diffusion while in the other the population is assumed to be non-dispersing. The population consists of the young (under maternal care), juvenile, and adult classes. Death moduli of the juvenile and adult classes in both models are decomposed into the sum of two terms. The first presents death rate by the natural causes while the other describes the environmental...
Large time behaviour of moments of solution of parabolic differential equations with random coefficients
Les processus itératifs en dynamique des populations et la théorie d'Easterlin
Lévy Processes, Saltatory Foraging, and Superdiffusion
It is well established that resource variability generated by spatial patchiness and turbulence is an important influence on the growth and recruitment of planktonic fish larvae. Empirical data show fractal-like prey distributions, and simulations indicate that scale-invariant foraging strategies may be optimal. Here we show how larval growth and recruitment in a turbulent environment can be formulated as a hitting time problem for a jump-diffusion process. We present two theoretical results. Firstly,...
Limit cycles in a Kolmogorov-type model.
Limitation and Regulation of Ecological Populations: a Meta-analysis of Tipula paludosa Field Data
Whether the size of an animal population is environmentally limited or regulated by density dependent negative feedback mechanisms is of ecological interest. Proponents of limitation theory have issued a set of specific challenges which are addressed in this paper using field data for the insect Tipula paludosa. This species is known to be subject to population crashes caused by adverse environmental conditions and assumed to be limited. We re-examine published data in support of this hypothesis...