[Interrelationship between the level of chromosomal aberrations and demographic parameters]

The interrelationship between the level of chromosomal abnormalities and demographic parameters has been studied using individuals from the natural population of bank vole (Clethrionomys glareolus) from a locality within the Middle Ural, of the southern taiga subzone (57 degrees 15' N, 58 degrees 44' E). Routine methods of cytogenetic analysis are applied to examination of variability in the frequency of structural chromosomal aberrations, gaps and changes in number of chromosomes in bank voles' bone marrow cells. Influence of demographic parameters, namely population density, age, sex, and reproductive status, on cytogenetic characteristics is estimated with the help of log-linear analysis. It is shown that population increasing in size leads to a decrease in the share of individuals characterized by higher frequency of cells with structural chromosomal abnormalities and gaps. This outcome appears to be in concordance with the notion of less amount of mutations in somatic cells to be favorable for organisms' survival rate. Such a pattern could emerge as a consequence of natural selection causing reorganization of genetic structure of a population. Alternatively, these changes may be a by-product of other processes accompanying population dynamics. High population density results in an increase of a share of individuals among young-of-the-years with higher frequency of cells subjected to abnormalities in chromosome number. Similar effects are possible as a result of asymmetric interference competition of adults in relation to younglings. Our data indicate that the share of animals having higher frequency of somatic cells with structual chromosomal aberrations and numerical chromosomal abnormalities is essentially increased by age, which is in accordance to theoretical concepts and experimental data. Gender and participation in reproduction do not render significant influence on the level of cytogenetic instability.