Killer Typhoons Began to Impact the Japanese Islands from ca.1.55 Ma, Based on Phylogeography of Chlorogomphus (Gliding Dragonfly)

Abstract

Chlorogomphus is a golden ring dragonfly, and characterized by swarming behavior, and strong gliding and flying. Therefore this dragonfly is expected to be easily carried by typhoon winds. This dragonfly immigrated and colonized the Pacific coast of southern Japan main islands from the Ryukyu islands. In this study, we demonstrate that the Japan mainland population is phylogenetically common to the northern Ryukyu population, but distinct from the southern Ryukyu and Taiwan populations. The East China Sea was formed between the Ryukyu island arc and Asian mainland by the rifting of the Okinawa trough that started at 1.55 Ma. Prior to this time typhoons lost strength when heading overland over the Ryukyu continental arc and continental China, but since then have maintained their strength northward because they were over water (the newly opened Okinawa trough). Chlorogomphus is interpreted to have speciated on each island, but it also migrated northward as a result of typhoons that carried it further than it could normally fly. The present paper shows that such typhoons that now ravage Japan may have been generated since 1.55 Ma and will continue to be dangerous, because the opening of the Okinawa trough is an ongoing process. This phenomenon is unrelated to global warming.