Phylogeography of cicadas on continental and oceanic islands in the northwestern Pacific region

Abstract

AbstractAimGenetic differentiation of terrestrial organisms among islands is assumed to be affected by the geological history of the islands, such as the time elapsed since the formation of islands or straits. Cicadas are generally poor dispersers, but some cicada groups have colonised continental and oceanic islands and evolved into endemic species. Here, we focused on a cicada group in the northwestern Pacific region to reveal the association between intra‐ and interspecific genetic differentiation and the geological history of islands for cicadas on continental islands. We also clarified whether colonisation of oceanic islands was achieved by long‐distance dispersal or artificial introduction.LocationJapanese Archipelago, Ogasawara Islands, Ryukyu Archipelago.TaxonCicadas of the genus Meimuna (Hemiptera: Cicadidae).MethodsWe 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.ResultsMeimuna 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 Meimuna kuroiwae and M. oshimensis diverged 2.4 Ma; these species showed differences in intraspecific genetic differentiation and range expansion. Furthermore, Meimuna iwasakii colonised 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 1.04 Ma.Main conclusionsGenetic 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.