VARIATION OF REPETITIVE DNA AND ITS PHYLOGENETIC RELATION IN HYNOBIIDAE (CAUDATA)

Middle repetitive (MR) DNA comprising about 35% of the genomic DNA of Hynobius retardatus was isolated and used as mixed probes, A 1.3-kb Ba m HI fragment, the major repeating unit of the extensively amplified s equences in H. retardatus, was cloned, sequenced, and used as a probe, Dot blot hybridization under the conditions of probe excess revealed that the MR DNA sequences were shared among the three salamander gener a belonging to the family Hynobiidae. However, a large difference in t he amount of common sequences was found between Hynobius and Salamandr ella, and large differences in both amounts and sequence similarity we re found between Hynobius and Onychodactylus. Even among species belon ging to the genus Hynobius, relative contents of sequences common to t he H. retardatus MR DNA were 20% to 50%. Partially related sequences t o the 1.3-kb sequence seemed to be present in all the species of Hynob ius and Salamandrella, but the extensive amplification was found only in H. retardatus, Based on the relative contents of the common MR DNA and previously reported chromosomal banding characteristics, species i n the genus Hynobius are classified into at least three groups. An evo lutionary aspect of the emergence of the amplified sequence in H. reta rdatus is discussed.