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 common f eature of animal mitochondrial DNA; however, the evolutionary dynamics of repeated sequences are not well understood. Using phylogenetic ana lysis, predictions of three models of repeat evolution were tested for arrays of 260-bp repeats in the cyprinid fish Cyprinella spiloptera. Variation at different nucleotide positions in individual repeats supp orted different models of repeat evolution. One set of characters incl uded several nucleotide variants found in all copies from a limited nu mber of individuals, while the other set included an 8-bp deletion fou nd in a limited number of copies in all individuals. The deletion and an associated nucleotide change appear to be the result of a determini stic, rather than stochastic, mutation process. Parallel origins of re peat arrays in different mitochondrial lineages, possibly coupled with a homogenization mechanism, best explain the distribution of nucleoti de variation.