• evolutionary rate;
  • genetic variation;
  • mitochondrial DNA;
  • pulmonata

Exceptionally high levels of intraspecific variation of mitochondrial DNA (mtDNA) sequences encoding 16S ribosomal RNA (16SrRNA) were detected in populations of the land snail Euhadra peliomphala from the eastern part of Japan. Geographical isolation has occurred within small areas and has created many genetically distinct local populations. These are morphologically segregated into two groups: the first consists of populations from the southern part of the Izu Peninsula, and the second of populations from other areas within the peninsula. They are separated by mountains in the middle of the peninsula. Sequence divergences between these two groups were 7.6–9.5%. The sequence divergences and geological ages of the Izu peninsula and its mountains suggest that the divergence rate of mitochondrial 16SrRNA sequences of this species is extremely rapid, approximately 10% per million years. This rapid evolutional“)‘ rate of mtDNA and vicariance events due to tectonic events and sea level changes has also contributed to creating exceptional geographical variation in the mtDNA of this species.