Three species, Luciola unmunsana and L. papariensis, endemic to Korea and L. tsushimana, endemic to Japan, have been taxonomically controversial whether they are independent or a single species for a long time. Therefore, we examined genetic diversity and evolutionary history of these species as well as including the related congeners using COI gene sequences (DNA barcoding region). Interestingly, we found seven paraphyletic groups from three species: two paraphyletic groups from L. papariensis, three paraphyletic groups from L. unmunsana and two paraphyletic groups from L. tsushimana. Among them, the group III of L. unmunsana collected from Jeolla-do province has never been recognized in the previous studies. A molecular clock analysis indicated that the origin of the major lineages of L. unmunsana, L. papariensis and L. tsushimana occurred between ~5.62 to 3.16 Ma. The origin of the major lineages of the group II and III of L. unmunsana, the group II of L. papariensis and the three groups of L. tsushimana occurred in 3.49 Ma (4.45–2.51 Ma, 95% HPD), which is consistent with the final disconnection of Japan from Korean Peninsula. The subsequent divergences of these paraphyletic groups clearly showed they have undergone allopatric speciation associated with geologic events in Korea and the sea level changes between Korea and Japan.

The Wolbachia bacterium, one of the most prevalent endosymbiotic bacteria, is known to induce reproductive anomalies in various invertebrate taxa. We investigated Wolbachia infection frequency in 203 Coleopteran insects collected from Korea. Among them 26 species (12.8%) across families proved to harbor Wolbachia. The phylogenetic trees of two Wolbachia specific genes imply that there have been complex horizontal gene transfers and recombination events within and between divergent Wolbachia subgroups. Interestingly, we also find that the infection frequency is noticeably low and incongruent at the family level when compared to other literature cases of Wolbachia infection in beetle species.