Postmating isolation and evolutionary relationships among species from Lesser Sunda, Indonesia and other Asian countries revealed by crossing experiments and mtDNA Cytb sequence analyses.

To evaluate the degree of postmating isolation and the evolutionary relationships among frog species in the genus from Indonesia (Lesser Sunda), Bangladesh, China, and Japan, crossing experiments and molecular phylogenetic analyses were carried out. Crossing experiments revealed that reciprocal hybrids among , , and . sp. large type and between and are viable through metamorphosis, while those between the group and group were completely or partially inviable at the tadpole stage and those between Southeast Asian and South Asian groups were completely inviable at the embryonic stage. The mature reciprocal hybrids between and from Lesser Sunda, Indonesia, showed some degree of abnormality in spermatogenesis. In phylogenetic analyses based on mtDNA sequences, formed a sister clade with from Lesser Sunda, Indonesia, with 8.1% sequence divergence. from China formed a clade with populations of in Thailand, Malaysia, and Indonesia (topotype), and these taxa showed sister relationships to from Japan with 8.9% sequence divergence. sp. small type from Bangladesh formed a clade with the other South Asian members of the group and formed a sister clade with the Southeast Asian group, with 23.1% sequence divergence in the gene. These results showed that the degree of postmating isolation reflects molecular phylogenetic relationships and that and from Indonesia (Lesser Sunda) are reproductively isolated by abnormalities in spermatogenesis and show genetic differentiation.