Fine-scale phylogeography of the Japanese Genji firefly

The Japanese Archipelago consists of four major islands and numerous small islands. The Goto Islands are located near Kyushu, a major island in the Japanese Archipelago. We have previously reported that the population of the Japanese Genji firefly, Nipponoluciola cruciata, inhabiting the Goto Islands displays a unique flashing pattern that is used for pre-mating communication between males and females, indicating the possibility of genetic isolation of the Goto Islands population from neighbouring N. cruciata populations. In this study, we aimed to elucidate the gene flow between the Goto Islands N. cruciata population and its neighbouring island populations by molecular phylogenetic analyses based on the mitochondrial DNA regions of cytochrome c oxidase subunit II and ND5, also coupled to genome-wide analysis of nuclear DNA single nucleotide polymorphisms. Our results suggested that the Goto Islands N. cruciata population is genetically isolated from other populations of this species. Nuclear DNA-based population analyses indicated gene flow between the populations inhabiting the Kyushu and Iki Islands, situated at a distance approximately equal to that between the Goto and Kyushu Islands. Therefore, the genetic isolation of the Goto Islands N. cruciata population is largely affected by flashing pattern behaviour, underlining an ongoing speciation process.