Phylogeography of Meimuna cicadas on continental and oceanic islands of Japan in the north-western Pacific region

Islands are a challenging habitat for organisms with weak dispersal power. We aimed to elucidate how geological history, geography, accidental dispersal events and species ecology affected different colonisation and genetic divergence patterns on continental and oceanic islands among species of a cicada group, which are poor dispersers. Location: Japanese Archipelago, Ogasawara Islands, Ryukyu Archipelago. Taxon: Cicadas of the genus Meimuna (Hemiptera: Cicadidae). We performed phylogenetic analysis, divergence time estimation, and ancestral area reconstruction using two mitochondrial and four nuclear gene sequences and population genetics analyses, including Bayesian skyline plotting using a mitochondrial gene sequence. Meimuna opalifera in the Japanese Archipelago, which was connected to the continent during the glacial periods, diverged from the continental populations 0.4 million years ago (Ma). In the Ryukyu Archipelago, which became disconnected from the continent earlier, two endemic species M. kuroiwae and M. oshimensis diverged 2.5 Ma; these species showed differences in intraspecific genetic differentiation and range expansion. Furthermore, M. iwasakiicolonised the South Ryukyus from Taiwan Island later than 1.4 Ma, whereas M. boninensis, which is endemic to the oceanic Ogasawara Islands, diverged from M. kuroiwae in the Middle Ryukyus 1.4 Ma. Genetic divergence among Meimuna species was larger on the continental islands that disconnected earlier, as was expected from the geological history of the islands. However, the pattern of intraspecific genetic differentiation differed between species within the same island region, possibly due to their ecological characteristics. In addition, colonisation of oceanic islands was achieved by long-distance (possibly wind-borne) dispersal from the continental islands. Thus, the formation of island cicada fauna was affected by islands’ geological history and species’ ecological characteristics, as well as accidental long-distance dispersal events.