Evolutionary dynamics of tandem repeats in the mitochondrial DNA control region of the minnow Cyprinella spiloptera

Length variation due to tandem repeats is now recognized as a commonfeature of animal mitochondrial DNA; however, the evolutionary dynamics ofrepeated sequences are not well understood. Using phylogenetic analysis,predictions of three models of repeat evolution were tested for arrays of260-bp repeats in the cyprinid fish Cyprinella spiloptera. Variation atdifferent nucleotide positions in individual repeats supported differentmodels of repeat evolution. One set of characters included severalnucleotide variants found in all copies from a limited number ofindividuals, while the other set included an 8- bp deletion found in alimited number of copies in all individuals. The deletion and an associatednucleotide change appear to be the result of a deterministic, rather thanstochastic, mutation process. Parallel origins of repeat arrays indifferent mitochondrial lineages, possibly coupled with a homogenizationmechanism, best explain the distribution of nucleotide variation.