BANK VOLES IN LINEAR HABITATS SHOW RESTRICTED GENE FLOW AS REVEALED BY MITOCHONDRIAL-DNA (MTDNA)

Genetic structure of bank vole populations in linear river bank habita t in southeast Norway was determined from analyses of DNA sequences fo r the mitochondrial D-loop. Animals were sampled at sites separated by 1 km, along two forested river banks separated by approximate to 100 m of open water. Twenty-six distinct haplotypes were found among 120 v oles. The voles showed significant deviation from panmixis on both sid es of the river. Animals from the same site or from sites 1 km apart w ere more likely to share haplotypes than animals 2 km apart or more. C ommon haplotypes were widespread on both river banks, and had a wider distribution than relatively rare haplotypes. Some rare haplotypes wer e found on both banks, but most were restricted to a single bank. The results suggest that short-term gene flow may be restricted for female bank voles in linear habitats. Female territorial behaviour may vary with habitat geometry. In the linear habitat described here, females d efend only two territorial borders and may effectively limit female di spersal. Results were compared to a previous study of bank voles from this region in a two-dimensional habitat. Gene flow in the linear habi tat was much more restricted than gene flow in the two-dimensional hab itat. Probable mechanisms underlying this difference are discussed.