Abstracts

Evolution of Species and Ecosystems: Theoretical Analysis and Computer-Assisted Modeling

Insects with eruptive type of population dynamics are an important component of most forest ecosystems. They are capable to cause significant damage under unfavorable conditions.

The purpose of the work was to develop a general model to allow analysis of regulating and modifying factors’ influence on character and parameters of insect population dynamics. Realization of such models is related with great amount of calculations and from the very beginning the model was developed as a computer programming complex.

The model is grounded on the followings:
– life cycle of the insect is described by a discrete set of stages and transitions.
– on the each stage there were determined factors affecting the number of survived individuals, type and parameters of influence functions describing the effect.
– environmental influence is modeled by stochastic functions with parameters related to current environmental status and given scenario.

Technically the stages are defined as separate objects with connected factors. Factors are independent blocks which save information on statistical distribution, variance, mean, and long-term trends.

When the factor is connected with a stage function affecting one of the characteristics: population, density, the mean larvae weight is chosen. As insect species differ by number, dynamics of life cycle stages, and intensity of environmental influence the approach presented gives the possibility to construct the model from the blocks models for different insect populations. The approach generality allows comparative analysis of several populations having the same area and being impacted by similar factors.

The calculated time-series of insect populations are studied to reveal frequency and amplitude of possible outbreaks and cyclic components.

Parameters of influence functions are adjusted to the observed population dynamics. The final model helps to research how population responses to environmental changes. It also calculates ranges of the parameter changes. If the parameters are out of the range the population dynamics changes abruptly and the outbreak occurs or population is eliminated. So the model is a tool to study the different strategies in environmental changes and their influence on forest insect population dynamics. The model is realized as a program in the operation system Windows 98 with the programming tool Borland Delphi 4. Finally the program is interactive application for Windows. It allows adjusting model parameters, saving and loading models for various insect species, graphical displaying population changes at different stages of the life cycle and phase portraits of population growth.

Note. Abstracts are published in author's edition

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