Origin and formative process of the Japanese Fauna viewed from molecular phylogeny and fossil records

点击翻译按钮获取中文摘要

This project had the ambitious goal of clarifying both the dominant geographic origins of Japanese Fauna and how the original fauna developed into the modeen distributions and types. A major part of this project was the molecular phylogenetic analyses of a number of representative land and marine animals. The land animals investigated include the genera Sus (wild boars), Cervus (deer), Selenarctos (Asian black bears), Diplothrix (Ryukyu long-haired rat), Trimeresurus (Habu snakes), Agkistrodon (Mamushi snakes), Cynops (newts), Cobitids (loaches), Coreoperca (Percichthyd) and Semisulcospira (fresh-water snails). The marine organisms were all molluscan species including limpets ((Pattellogastropods), Haliotis (abalones), Turbinids (turban shells), Buccinum and Neptunea (Buccinids), Anadara (arcids), Crassostrea (oysters), and Meretrix (Venerid bibalves). The analyses used samples of most of the relevant species and subspecies of animals with distributions extending throughout the Japanes … More e Islands and Asia (or, in the case of marine organisms, throughout the world.) These results were combined with stratigraphical and paleontological studies of related fossils found in terrestrial and marine deposits throughout the Japanese Islands and Asian continent. Where relevant fossils in other locations throughout the world were also considered.These molecular phylogenetic analyses revealed that an animal species living in Japan generally treated as a single species are in fact commonly composed of two or more allopatrically distributed subspecies or species. Molecular phylogeny and fossil records suggest the most likely explanation for the present-day allopatric distribution of many species in the Japanese Islands is repeated migration of genetically separated subspecies or species from the Asian continent at different geological times following different migration routes. The same features are also observed in marine mollusks, and are particularly clearly exhibited by the molecular phylogeny and fossil records of Japanese limpets and ablones.The timing and location of immigration routes for land mammals that arrived from the Asian continent in the Japanese Islands during the Pleistocene were mainly estimated from the biostratigraphical distribution of elephant fossils in Japan and China. The occurrences of Mammuthus shigensis around 1.2 Ma, Stegodon orientalis around 0.6 Ma. Paleoloxodon naumanni around 0.35 Ma in Kyushu-Shikoku-Honshu, and Mammuthus primigenius around 0.02 Ma in Hokkaido strongly suggest the presence of land bridges at these times that enabled the immigration of the large land-based mammals.In the Ryukyu Islands, the present study revealed the presence of rich and varied Early to Middle Pleistocene vertebrate faunas in Okinawa Island. Until recently Pleistocene fossil records of this area were mostly restricted to the Late Pleistocene. Paleontological investigations of these fossil vertebrate faunas revealed that an ancestral fauna consisted of immigrants from the continents in the pre-Pleistocene and Early Pleistocene periods and also that the present-day endemic fauna of the Middle Ryukyu with a small number of species was formed by repeated extinction events affecting the varied ancestral fauna that has long been isolated from the continent after the formation of the Okinawa trough. This study also revealed that the fauna of the Southern Ryukyu is composed of both Late Pleistocene and much earlier immigrants. Less