Mitochondrial DNA insertion polymorphism and germ line heteroplasmy in the Triturus cristatus complex

Restriction enzyme analysis of mitochondrial (mt) DNA isolated from oocytes of 185 individuals of the T. cristatus complex collected from 10 European countries has demonstrated that large length variation (greater than 40 bp) is a common feature of the group. Insertion polymorphism was found both within and among populations, and in all cases maps to the control region of the molecule. In addition, 2 individuals from Pisa, (Italy) were each found to be heteroplasmic for 2 large insertions comprising tandem repeats of 1100 bp of the control region. Large-scale length variation has been described in a few other lower vertebrates, but some of the insertion variants within populations described here are of unprecedented size (up to 8500 bp). This is in dramatic contrast to mammalian mtDNA in which size variation is largely restricted to small (less than 15 bp) insertions and deletions.