| Abstract: | DNA sequences from the mitochondrial DNA control region are used to test the phylogeographic relationships among the pike-perches,Stizostedion(Teleostei: Percidae) and to examine patterns of variation. Sequences reveal two types of variability: single nucleotide polymorphisms and 6 to 14 copies of 10- to 11-base-pair tandemly repeated sequences. Numbers of copies of the tandem repeats are found to evolve too rapidly to detect phylogenetic signal at any taxonomic level, even among populations. Sequence similarities of the tandem repeats amongStizostedionand other percids suggest concerted evolutionary processes. Predicted folding of the tandem repeats and their proximity to termination-associated sequences indicate that secondary structure mediates slipped-strand mispairing among the d-loop, heavy, and light strands. Neighbor-joining and maximum parsimony analyses of sequences indicate that the genus is divided into clades on the continents of North America and Eurasia. Calibrating genetic distances with divergence times supports the hypothesis thatStizostediondispersed from Eurasia to North America across a North Pacific Beringial land bridge approximately 4 million years before present, near the beginning of the Pliocene Epoch. The North AmericanS. vitreumandS. canadenseappear separated by about 2.75 million years, and the EurasianS. luciopercaandS. volgensisare diverged by about 1.8 million years, suggesting that speciation occurred during the late Pliocene Epoch. |
