Diversification process of high mountain oaks with uplift of Himalayas and Quaternary climatic changes

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The aim of the present research is to clarify the process of the evolution and development of Quercus sect. Heterobalanus (Fagaceae) that dominates in alpine vegetation in and around Himalayas and is considered to have evolved accompanied with uplift of Himalayas. We obtained plant macrofossil assemblages including Quercus sect. Heterobalanus from the Kathmandu, Nepal and southwestern Yunnan by sieving sediments to reconstruct paleovegetation with the paleoenvironments based on composition of the fossil assemblages. We collaborated with Dr. Zhou ZK. in the Yunnan Institute of Botany, Academia Sinica for identification of fossils with the discussion. We collected geological data as for climatic fluctuation in the Plio-Pleistocene in East Asia with data of plant macrofossil assemblages from the Uonuma Group in central Japan to produce paleoclimatic curve since 2.4Ma. We compared plant macrofossil data including Quercus sect. Hetelobalanus in and around Himalayas with the paleoclimatic data in and around Japan. In the fossil assemblages form Nepal and southwest China, fossils of Quercus sect. Hetelobalanus occur with Picea and Abies that indicate cold climate. This shows that this section expanded the distribution in the glacial stages since the late Pliocene and was confined in higher altitudes in the interglacial stages. A fossil assemblage from southwestern Yunnan Province described by Momohara et al. (2006) indicated that the forest zone of subalpine evergreen conifer and alpine Hetelobalanus vegetation was distributed in the altitude about 1000m lower than extant elevation in a late Pliocene cold stage. Thus, the vegetation zones migarate about 1000 m vertically with the glacial-interglacial climatic cycles since the late Pliocene not only in the middle latitudes including Japan but also in alpine areas in lower latitude including Himalayas and southern China and it enhanced the expansion and speciation of Quercus sect. Heterobalanus since the late Cenozoic.