ISSN 2079-0864, Biology Bulletin Reviews, 2013, Vol. 3, No. 3, pp. 209–213. © Pleiades Publishing, Ltd., 2013. Original Russian Text © M.I. Cheprakov, S.B. Rakitin, 2012, published in Zhurnal Obshchei Biologii, 2012, Vol. 73, No. 4, pp. 253–258. 209 INTRODUCTION The errors in correcting abnormalities in DNA molecules used on various repair mechanisms lead to the emergence of chromosomal aberrations in living cells (Griffin and Thacker, 2004; Pfeiffer et al., 2004). It is known that the initial DNA structure is restored under genetic control (Thacker, 1999; Symington, 2002). Mutations in the genes that control repair pro- cesses may lead to an increase in the rate of chromo- somal abnormalities in cells of various tissues, as well as to a delay in the growth of individuals and a decrease in their viability at a particular developmental stage (Difilippantonio et al., 2000; Gao et al., 2000; Nijnik et al., 2007). On the other hand, the survival rate as a characteristic of viability regularly changes during population cycles (Krebs and Myers, 1974). This sug- gests a correlation between the intensity of mutation processes and population density. The clarification and understanding of this correlation will enhance the insight into the mechanisms underlying the popula- tion dynamics of living organisms. The previous stud- ies failed to provide a clear understanding of the pat- tern of this correlation (Dmitriev et al., 1997; Gileva et al., 2006). The current view on the cyclic pattern of popula- tion dynamics is based on the understanding that this phenomenon is influenced by a multitude of factors, in particular food abundance and accessibility, weather conditions, predation, social interactions, and diseases (Krebs, 2009). An essential issue is the potential interaction between these factors. Our results suggest that the intensity of the mutation process depends on the size of the population. MATERIALS AND METHODS The object of this work was the wildlife population of the bank vole (Clethrionomys glareolus) from a Mid- dle Ural locality in the southern taiga subzone (57°15′ N, 58°44′ E) with only a global technogenic pollution. The animals were trapped in the second half of July over 10 years (1999–2008). The population size was estimated according to the number of catches per 100 trap-days during the first 2 days of trapping. In a narrow sense, this is a relative population size and in a broad sense, it is characteristic of the population abundance of animals. In this work, the terms “popu- lation density” and “population size” are used in the broad sense as synonyms of animal abundance. The Correlation between Level of Chromosomal Aberrations and Demographic Parameters M. I. Cheprakov and S. B. Rakitin Institute of Plant and Animal Ecology, Ural Branch, Russian Academy of Sciences, ul. 8 Marta 202, Yekaterinburg, 620144 Russia e-mail: cheprakov@ipae.uran.ru Received June 14, 2011 Abstract—The correlation between the level of chromosomal abnormalities and demographic parameters has been studied using individuals from a local wildlife population of the bank vole (Clethrionomys glareolus) from a Middle Ural locality in the southern taiga subzone (57°15′ N, 58°44′ E). Variations in the rate of structural chromosomal aberrations, gaps, and changes in the number of chromosomes in the bone marrow cells of the bank vole has been examined using routine cytogenetic methods. The effect of demographic parameters, i.e., population density, age, sex, and reproductive status, has been estimated using log-linear analysis. It has been shown that the share of individuals with an elevated rate of cells that carry structural chromosomal abnormal- ities and gaps decreases with increases the population size. This pattern agrees with the standpoint that a lower rate of mutations in somatic cells enhances survival of organisms. This pattern can have established as a con- sequence of natural selection, which induces the rearrangement of the genetic structure in the population or as a byproduct of other processes in the population that accompanies the changes in its size. A high popula- tion density leads to an increase in the share of individuals that display an elevated rate of cells with abnormal chromosome numbers among the yearling voles. A similar effect may result from an asymmetric interference competition between adults and yearling individuals. Our results demonstrate that the proportion of animals that display an elevated rate of somatic cells with structural chromosomal abnormalities and aberrant chro- mosome numbers considerably increases with age, which agrees with both the theoretical concepts and experimental data. Neither sex nor involvement in reproduction has any significant effect on the level of cyto- genetic instability. DOI: 10.1134/S2079086413030043