Lagrangian models for the dynamics of a multistage population: effects of different development models
Giuseppe Buffoni, Sara Pasquali
CNR-IMATI
(Abstract received 08/04/2009 for session E)
ABSTRACT
It is assumed that the development process equations of an individual are stochastic equations, describing the time evolution of the status of an individual, in terms of a physiological age. General properties of development models of an individual, together with the basic steps identifying the life history of an individual, are briefly illustrated. Then, we address the formulation of development models, when "regression" effects (defined as negative development) on the status of an individual are forbidden; this is the case when the physiological age is defined in terms of an abstract non-decreasing indicator measuring maturity or the percentage of development. Three different discrete stochastic models of the development process are presented, and their responses compared. Their behaviours are analyzed by varying the stochasticity level, which takes into account the degree of intraspecific variability. A multi-stage system, representing a copepod population, is used to illustrate the different dynamics outcomes, depending on the dvelopment model applied, by means of numerical simulations. Some idealized situations will be considered, trying to separate the effects of the main processes influencing the life history of an individual. First, the stochastic development process from egg to juvenile and adult stages, neglecting the mortality events, and the consequent stage distributions of the individuals, is illustrated. Then, the effects of the stochastic mortality process on stage distribution is shown. Finally, the total population growth is estimated.
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