Studies on diversity, natural history, and conservation of amphibians.
My first concern was proper classification of Japanese toads, and I was engaged in macro-biology of Bufo . At the same time, I noticed that there remained many taxonomic problems about other amphibian taxa in Japan. Similarly, it was made clear that taxonomic problems remained unresolved outside of Japan, even in Borneo where quite a few studies had already been made. I found many taxa that have been synonymized or relegated to be subspecies actually represent good species. Within these 30 years, I described a total of 22 species and one subspecies of 10 genera (four species in one genus of hynobiids, two species and one subspecies in two genera of bufonids, four species in three genera of megophryids, 11 species in three genera of ranids, and one species in one genus of rhacophorids), but there still remain many undescribed taxa at hand. Through recent studies of DNA phylogeny, phylogenetic relationships of many lineages that were systematically complex have been resolved, and on the bases of results obtained, I am now trying to elucidate history of diversity formation in Asian amphibians. At the species level, amphibians are even more diversified than mammals, and thus, elucidation of whole species diversity of this group and description of all species even in the Asian region surely require much more time.