Abstracts

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

Analysis of conjugated population dynamics of three species of forest insects – phyllophagous (nun moth Lymantria monacha L., gypsy moth Lymantria dispar L., european pine sawflies Neodiprion sertifer Geoffr.) and insect-specific nuclear polyhedrosis viruses were performed in connection with a functional conditions of food plants. Structural and functional properties of both insect and virus populations during different periods of the insect population cycle epidemic and endemial phases and in various states of birch and pine trees were studied. As it was shown these parameters depend on plantation biotopical conditions and level of their defoliation. In pessimal growth conditions (plantations were in depression state) the insect's viability and resistance increase. Also there were revealed the low level of death rate during the juvenile phases, high indexes of a fecundity, sex ratio and net reproduction. In a result there was the population growth and it's transmission to the epidemic phase of population cycle. Expressed plant defoliation (not less than 50 %) had negative influence onto insect viability and resistance with respect to viruses. It led to increase of their death rate from pathogens and other regulative factors. Finally, as a result the insect population returned to the endemial phase of population cycle.

Endogenic nuclear polyhedrosis virus was detected in gypsy moth populations by molecular hybridization of nucleic acids and enzyme – linked immunosorbent assay (ELISA). The virus persistence appeared to depend on the population cycle phase. During epidemic phase the virus' level was lower for insect population growth period and higher during the declination period. DNA hybridization of the virus in gypsy moth populations, that depends on a degree of virus population heterogeneity, also depends on the phase of population cycle. For the peak phase and, especially, for declination period of gypsy moth population dynamics the virus genomes had the lowest hybridization level that point out onto the high order of virus population heterogeneity. The maximal hybridization level with all probes which correspond to conservative and variable segments of a virus genome was revealed during the growth period of the insect population.

Analysis of modern literature and experimental data allowed us to construct mathematical models of the resource - phytophagous - pathogen system dynamics. It was realized as on the base of traditional models (systems of ordinary differential equations) as on the base of differential equations with impulses. The phase portraits were constructed on the plane "population density - birth rate" for some partial cases. These phase portraits permitted to identify the outbreak types which can be realized in the models.

Note. Abstracts are published in author's edition

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