Previous work found that different Japanese lineages of salamanders had quite different levels of species and genetic diversity.

Lineages vary from having one to several species and the extent of genetic variation among lineages differs substantially. Most speciose, genus Hynobius contains 18 species and several potential cryptic species.

Prof.ZENG Xiomao from Chengdu Institute of Biology explore genetic diversity in this genus by combining comprehensive sampling and mitochondrial DNA sequences. Based on this and previous analyses of salamanders, relative times of divergence are employed to evaluate the relationship between age and diversity among the four major lineages whose distributions broadly overlap on the islands.

For Hynobius, the analyses are congruent with the previously reported high level of cryptic diversity in morphology and allozymes, particularly in species composed of non-sister matrilines. Both species and genetic diversity correlate with the relative ages of the lineages. This correlation indicates that the variation in levels of diversity can be explained, to a considerable extent, by the hypothesis that older insular lineages have accumulated greater diversity.

In addition to the Korean Peninsula, H. leechii might have survived in another Pleistocene glacial refugium north of the peninsula and this refugium provided a source of colonization after the last glacial maximum.