| Research Abstract |
This study was made as a part of phylogenetic analyzes of the family Ranidae, which nobody has succeeded since 1920, by applying a new method of comparing DNA sequences to clarify relationships among related taxa.
First, phylogenetic relationships among all known 10 nominate taxa of Japanese brown frogs (Rana pirica, R.dybowskii, R.ornativentris, R.japonica, R.tagoi tagoi, R.t.yakushimensis, R.t.okiensis, R.sakuraii, R.tsushimensis, and R.okinavana) are assessed on the basis of the sequence of 456 base pairs of the mitochondrial cytochrome b genes. The resultant phylogenetic trees indicate that the R.tagoi group with distinct breeding habits, differentiated earliest, followed by R.tsushimensis and R.okinavana, both isolated on islands. Considerable genetic differentiation is found between subspecies of R.tagoi and between two populations of R.okinavana. Species with 2n=24 chromosomes form a monophyletic group, and appear to be derived from a 26-chromosome ancestor.
Second, phylogenetic relationships of brown frogs with 2n=24 chromosomes are analyzed using topotypic R.chensinensis from Tsingling, China. The result indicated that R.ornativentris, R.pirica or R.dybowskii, all once regarded as conspecific with R.chensinensis was found to be distinct from R.chensinensis from the type locality not only morphologically but also genetically.
DNA sequences of major brown frog taxa from China, Taiwan, and Russia have already been determined, and analyzes of their phylogenetic relationships are now under way. Further, phylogenetic relationships of representative ranid genera from Southeastern Asia has also been studied, and by accumulating these data and comparing the result with morphological and ecological information, relationships of the family Ranidae as a whole would be made clear and limit of biochemical methods would be elucidated.
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