RAPID EVOLUTION OF A HETEROPLASMIC REPETITIVE SEQUENCE IN THE MITOCHONDRIAL-DNA CONTROL REGION OF CARNIVORES

We describe a repetitive DNA region at the 3' end of the mitochondrial DNA (mtDNA) control region and compare it in 21 carnivore species rep resenting eight carnivore families. The sequence and organization of t he repetitive motifs can differ extensively between arrays; however, a ll motifs appear to be derived from the core motif ''ACGT.'' Sequence data and Southern blot analysis demonstrate extensive heteroplasmy. Th e general form of the array is similar between heteroplasmic variants within an individual and between individuals within a species (varying primarily in the length of the array, though two clones from the nort hern elephant seal are exceptional). Within certain families, notably ursids, the array structure is also similar between species. Similarit y between species was not apparent in other carnivore families, such a s the mustelids, suggesting rapid changes in the organization and sequ ence of some arrays. The pattern of change seen within and between spe cies suggests that a dominant mechanism involved in the evolution of t hese arrays is DNA slippage. A comparative analysis shows that the mot ifs that are being reiterated or deleted vary within and between array s, suggesting a varying rate of DNA turnover. We discuss the evolution ary implications of the observed patterns of variation and extreme lev els of heteroplasmy.