Phylogeography of Fischer's blue, Tongeia fischeri, in Japan: Evidence for introgressive hybridization

► Tongeia fischeri consists of six mitochondrial clades in Japan. ► The existing evolutionary lineages are strongly associated with the geographical distribution. ► Geographical patterns of variation of mitochondrial and nuclear DNA are discordant. ► Evidence of introgressive hybridization was detected in the northeastern Kyushu population.