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 1 00-200 million Curies of radioactive material into the surrounding environm ent. To investigate the possible genetic and population effects resulting f rom chronic exposure to this environmental radiation, we have examined mito chondrial DNA (control region) sequences from bank voles, Clethrionomys gla reolus, inhabiting contaminated sites. Our analysis indicates genetic diver sity is elevated in the contaminated sites when compared to relatively unco ntaminated reference sites. This may be attributed to either an increased m utation rate in the mtDNA control region or immigration of individuals from surrounding areas into the contaminated environment. Although our observat ions do indicate that the contaminated areas represent sink populations, we cannot statistically discriminate between these two alternatives at this t ime. In addition, we have been unable to attribute any significant detrimen tal effects to bank vole populations inhabiting the contaminated Chornobyl environment based on these data. This is particularly paradoxical consideri ng 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, includi ng contaminants, may affect haplotype dynamics both spatially and temporall y. These multifarious influences subsequently affect population genetic est imates typically used to address the effects of environmental pollution on animal populations. Finally, we provide a general framework for designing e xperiments investigating the role contaminants play in altering the genetic characteristics of exposed populations.