Variation in Pied Flycatcher (Ficedula hypoleuca) Mitochondrial DNA

Pied Flycatchers (Ficedula hypoleuca) in Sweden have low levels of variation in nuclear genes relative to most other bird species. This lack of variation has been attributed to population bottlenecks caused by Pleistocene glaciations. We studied mitochondrial DNA (mtDNA) variation in 20 Pied Flycatchers from four Swedish localities. Eight restriction endonucleases yielded a total of 207-212 DNA fragments (approximately 5% of the mtDNA genome). The mean pairwise divergence between the individuals was 0.35 ± 0.16% (range 0.00-0.82%), which suggests that the 18 identified mtDNA clones diverged within the past million years, and that the majority of clones evolved within the last 100,000 years. If genetic variation was reduced by prolonged bottlenecking during the last glacial period, low protein heterozygosity and high variability in mtDNA can be explained by a difference in rates of recovery of nuclear and mtDNA variation. The Pied Flycatcher in northern Europe may have only recently begun to regain variation in nuclear genes, whereas considerable variation in mtDNA has already accumulated through mutation.