Search results for " population dynamic"

Observations on population dynamics of leafhoppers in Western Sicily vineyards

2013

From 2007 to 2009 field observations were carried out in two vineyards (organically and conventionally managed) in Menfi (Agrigento province, Sicily). Population dynamics of two leafhoppers, Jacobiasca lybica (cotton leafhopper) and Zygina rhamni were followed by chromotropic traps and leaf observation in field. Both species were constantly present in vineyards. Z. rhamni did not register statistical differences between the two fields, while J. lybica was mostly present in the conventionally managed field. In this last vineyard for two consecutive years (2007 and 2008) J. lybica population exceeded the intervention threshold of 0.5 leafhopper/leaf. On the other hand, in the organically mana…

Osservazioni sulla dinamica di popolazione di due cicaline ampelofaghe nella Sicilia occidentale

2011

Observations on population dynamics of leafhoppers in Western Sicily vineyards From 2007 to 2009 field observations were carried out in two vineyards (organically and conventionally managed) in Menfi (Agrigento province, Sicily). Population dynamics of two leafhoppers, Jacobiasca lybica (cotton leafhopper) and Zygina rhamni were followed by chromotropic traps and leaf observation in field. Both species were constantly present in vineyards. Z. rhamni did not register statistical differences between the two fields, while J. lybica was mostly present in the conventionally managed field. In this vineyard for two consecutive years (2007 and 2008) J. lybica population exceeded the intervention th…

Crustacean dynamics in two argillotrophic, temporary ponds (North-Western Sicily, Italy)

2004

Ecology and distribution of Calanoid Copepods in Sicilian inland waters (Italy)

2006

(2006). Ecology and distribution of calanoid copepods in Sicilian inland waters (Italy) SIL Proceedings, 1922-2010: Vol. 29, No. 5, pp. 2150-2156.

A Simple Noise Model with Memory for Biological Systems

2005

A noise source model, consisting of a pulse sequence at random times with memory, is presented. By varying the memory we can obtain variable randomness of the stochastic process. The delay time between pulses, i. e. the noise memory, produces different kinds of correlated noise ranging from white noise, without delay, to quasi-periodical process, with delay close to the average period of the pulses. The spectral density is calculated. This type of noise could be useful to describe physical and biological systems where some delay is present. In particular it could be useful in population dynamics. A simple dynamical model for epidemiological infection with this noise source is presented. We …

Predator population depending on lemming cycles

2016

In this paper, a Langevin equation for predator population with multiplicative correlated noise is analyzed. The noise source, which is a nonnegative random pulse noise with regulated periodicity, corresponds to the prey population cycling. The increase of periodicity of noise affects the average predator density at the stationary state.

A stochastic dynamic model to evaluate the influence of economy and well-being on unemployment control

2018

[EN] This paper presents a stochastic dynamic mathematical model to study the evolution of the unemployment rate and other relevant related variables in a country. This model is composed by three basic interrelated subsystems: demographic, economic and wellbeing ones. A key aspect of this model is that it considers three UN well-being variables simultaneously: Human Development Index, Gender Empowerment Index and Gender Differentiation Index. These variables involve key concepts for human development, as Health, Education, Economy and Female Labor. With this model, the most outstanding variables found in the literature in relation with unemployment control can be used to design strategies a…

Graphical representation of some duality relations in stochastic population models

2007

We derive a unified stochastic picture for the duality of a resampling-selection model with a branching-coalescing particle process (cf. http://www.ams.org/mathscinet-getitem?mr=MR2123250) and for the self-duality of Feller's branching diffusion with logistic growth (cf. math/0509612). The two dual processes are approximated by particle processes which are forward and backward processes in a graphical representation. We identify duality relations between the basic building blocks of the particle processes which lead to the two dualities mentioned above.

Role of sub- and super-Poisson noise sources in population dynamics

2020

In this paper we present a study on pulse noise sources characterized by sub- and super-Poisson statistics. We make a comparison with their uncorrelated counterpart. i.e. pulse noise with Poisson statistics, while showing that the correlation properties of sub- and super-Poisson noise sources can be efficiently applied to population dynamics. Specifically, we consider a termite population, described by a Langevin equation in the presence of a pulse noise source, and we study its dynamics and stability properties for two models. The first one describes a population of several colonies in a new territory with adverse environmental conditions. The second one considers the development of a sing…

Noise Induced Phenomena in the Dynamics of Two Competing Species

2015

Noise through its interaction with the nonlinearity of the living systems can give rise to counter-intuitive phenomena. In this paper we shortly review noise induced effects in different ecosystems, in which two populations compete for the same resources. We also present new results on spatial patterns of two populations, while modeling real distributions of anchovies and sardines. The transient dynamics of these ecosystems are analyzed through generalized Lotka-Volterra equations in the presence of multiplicative noise, which models the interaction between the species and the environment. We find noise induced phenomena such as quasi-deterministic oscillations, stochastic resonance, noise …