A stochastic model for the dynamics of a
single species of a stage structured population is presented. The model
(in Lagrangian or Monte Carlo formulation) describes the life history
of an individual assumed completely determined by the biological
processes of development, mortality and reproduction. The dynamics of
the overall population is obtained by the time evolution of the number
of the individuals and of their physiological age. No other assumption
is requested on the structure of the biological cycle and on the
initial conditions of the population. Both a linear and a nonlinear
models have been implemented. The nonlinearity takes into account the
feedback of the population size on the mortality rate of the
offsprings. For the linear case, i.e. when the population growths
without any feedback dependent on the population size, the balance
equations for the overall population density are written in the
Eulerian formalism (equations of Von Foerster type in the deterministic
case and of Fokker-Planck type in the stochastic case). The asymptotic
solutions to these equations, for sufficiently large time, are in good
agreement with the results of the numerical simulations of the
Lagrangian model.
As a case study the model is applied to simulate the dynamics of the greenhouse whitefly, Trialeurodes vaporarioum (Westwood), a highly polyphagous pest insect, on tomato host plants.
As a case study the model is applied to simulate the dynamics of the greenhouse whitefly, Trialeurodes vaporarioum (Westwood), a highly polyphagous pest insect, on tomato host plants.
