Morphometric variation analyses and revision of the Japanese toads (Genus Bufo, Bufonidae)

Two problems havc been involved in the classification of the Japanese toads : (1) relationships with the continental forms, and (2) relationships among forms hitherto described within the islands. The present study was undertaken with the purpose otresolving the latter problem, and to achieve this, morphometric variation analyses were made ofa large number of preserved specimens. The results were synthesized with the hitherto accumulated nonmetrical and non-morphological information so as to taxonomfcally revise the Japanese toads. A historical review of the classificat{on of theJapanese toads revealed that the most complex problems were involved in the still-water breeding forms from the main islands (= the Japanese common toad), and that thc taxonomic confusion was caused mainly by previous authors' classification through examination ofa small number ofspecimens notwithstanding the great variability ofexternal morphometric characters ofthe toads. The critical points for measurcments fbr each character, and problcms with measurement crrors duc to variant fixation and preservation are discussed. Allomorphic relations of 30 charactcrs to SVL were analyzed fbr four age/sex groups o{' 147 Japanese common toads from rvlomoyama, Kyoto, with thc result that many characters should be trcated separately tbr three groups, i.c. , young, adult males, and adult females. Besides, it was determined that simple ratios to SVL should not be calculated for many characters. For theJapanese common toad, SVL and relativc value (ACV:=theoretical value calculated by the allomorphic relationship of each character to SVL) of 10 selected characters for each of 2,525 specimens belonging to 96 populations were analyzed, and the presence or absence of intrapopulational age and sexual variations and of interpopulational variations was noted. From these analyses, the Japanese common tbad was divided into northeastern (A) and southwestern (B) types chiefiy by the relative size of thc tympanum diameter. For the two types of the . Japanese common toad, presence of morphometric clines in re! ation to geographical and/or climatological parameteis was investigated. Clear clinal tendencies were found mostly in type A, whereas few clear trends were detected in type B. Taxonomical meaning of the clines was discussed, and it was suggested that the Japanese common toad should be split into taxa beiow the species level. Similar morphometric analyses were made on the still-water breeding Miyako toad from thc Ryukyu Archipelago. The results for 176 specimens from 4 populations ind{cated that this form was very uniform in. external morphometry, that it greatly differed from the Japanesc common toad in several characters, and that the differences were greater bctween this form and geograph{cally adjacent type B Japanese common toads in some characters. Similar analyscs were also performed on 265 specimens of 13 populations of thc stream-breeding ,Japanese stream toad. Interpopulation variation in this form was very small. Comparisons with sympatric and allopatric populations of thc Japanese common toad wcre made with the, result that the two fbrms were found to be morphometrically almost complctcly separatcd, showing grcatest differentiation in thc zQne. of sympatry. Taxonomic ('onclusions wcre drawn with thesc rcsults in mind. For tlie.Japa. ncsÅë c,ommon toad, thc typc scries or topc)types of each of the hitherto described fbrms wcre compared with thc othcr populations and it was determined that neither type A nor typc B can bc split further. Thc syntypes of Bqfo l) Part of a thesis submitted to the Faculty of Scien(:e of Kyoto University in partial fu1filment requirein(,". nts for the D. Sc. degree. ot' the