Consequences of polluted environments on population structure:: The bank vole (Clethrionomys glareolus) at Chornobyl

The accident at the Chornobyl Nuclear Power Plant in April 1986, released 100-200 million Curies of radioactive material into the surrounding environment. To investigate the possible genetic and population effects resulting from chronic exposure to this environmental radiation, we have examined mitochondrial DNA (control region) sequences from bank voles, Clethrionomys glareolus, inhabiting contaminated sites. Our analysis indicates genetic diversity is elevated in the contaminated sites when compared to relatively uncontaminated reference sites. This may be attributed to either an increased mutation rate in the mtDNA control region or immigration of individuals from surrounding areas into the contaminated environment. Although our observations do indicate that the contaminated areas represent sink populations, we cannot statistically discriminate between these two alternatives at this time. In addition, we have been unable to attribute any significant detrimental effects to bank vole populations inhabiting the contaminated Chornobyl environment based on these data. This is particularly paradoxical considering bank voles in the contaminated areas harbor the highest radiocesium (Cs-137) body burdens and external dose rates of any mammal ever measured. Our long-term research on the bank vole indicates that several factors, including contaminants, may affect haplotype dynamics both spatially and temporally. These multifarious influences subsequently affect population genetic estimates typically used to address the effects of environmental pollution on animal populations. Finally, we provide a general framework for designing experiments investigating the role contaminants play in altering the genetic characteristics of exposed populations.