"False signature" of past population expansions in North Atlantic minke whales mitochondrial control region sequences

The most common approach used to assess the demographic history duringevolutionary time is by analysis of DNA sequences, typically mitochondrial(mt) DNA. The shape of the genealogy estimated all sampled mt controlregion sequences in a population differs between expanding, stable anddeclining populations. The mt control region genealogies estimated frompopulation samples in several North Atlantic cetaceans (e.g., minke whale,fin whale, beluga and narwhal) are highly consistent with exponentialpopulation expansions during recent evolutionary time. These results agreewell with the distribution of the ice coverage during the last glaciations. Wesequenced additional mt genes (cytochrome b and cytochrome oxidase I) inaddition to the entire control region in samples from North Atlantic minkewhales. While the mt control region showed the previously reportedexpansion signature, the distribution of genetic variation at the other twogenes was as expected for a population of constant population size. As allthree genes are fully linked the effects of selection and/or demographicchanges is expected to be observed at all three genes, contrary to ourobservation. The cause for the discrepancy appears to be due to the extremesite-heterogeneity in substitution rates at the mt control region. Our resultshave implications for the many studies in cetaceans, and other species whichhave inferred demographic history from sequence variation in the mt controlregion