Universality and hierarchy in evolutionary pattern-approach from "marine insect" Ostracoda

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Evolutionary characteristics of ostracodes ware comprehended through this work. Marine cytheroidean ostrcaodes, which are probably most diversified taxa in ostracodes, are known for its increasing of diversity in Paleogene. The super family is proved to have paedomorphic characters against the other primitive superfamilies such as Bairdoidea and Cythpridoidea. This is seen in the number of pores in carapaces and the number of setae in brachial plates. The results are obtained from the detail observation and description of representatives from each superfamilies through ontogeny. On the other hand, four genera belonging to the superfamily cytheroidea and bairdioidea were especially studied well on the process and timing of the speciation and evolution. They were the genera Loxoconcha, Xestoleberis, Paradoxostoma of cytheroidea and the genus Neonesidea of bairdoidea, and their taxonomiy and geographical distribution were studied in Japan, Philippines and the west coast of North America. The common pattern found in the evolution of these genera lead to the conclusion that the biodiversity of related species are extgremely high around Japan compared with other areas in the world. These related species are living separately in Pacific, Sea of Japan, Okhotsk Sea and cold Oyashio areas, which corresponds to the currents and/or marine climatic divisions. The reason of this fact may be because the glacial eustatic sea level changes in the Quaternary caused the isolation of the marginal seas, and eventually a natural selection for the mutation which was able to adapt to the cold climate during glacial ages. As mentioned above, through this study, the evolutionary model which can be applicable to the isolated marginal sea area was first acquired.