Process of floral differentiation between east and west of the Eurasian Continent based on fossil records

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The purpose of this study is to clarify relationships between the processes of differentiation of flora and environmental changes that have occurred in the temperate zones in the Eurasia since the Tertiary. I studied morphology of fossil taxa including Fagus and Trapa which have spread widely in Eurasia and became differentiated accompanying Neogene climatic change in Japan and Poland. In addition, I analyzed the composition of fossil assemblages including the taxa and its sedimentary environments based on recent geological data. This results are the following : 1)It indicates possibility of floral connection between east and west of the Eurasia that there was not clear morphological differentiation between Japan and middle Europe in the earliest late Miocene fossil Fagus and Trapa. 2)Japanese fossil Fagus leaves have temporal changes of the morphology similarly as European fossils, in that number of the secondary vein decreased and width of blade became wide since the latest middle Miocene to the Pliocene. 3)The process of reduction in the distribution of Fagus, Trapa and Metasequoia since the late Miocene indicates that climatic deterioration since the late Miocene influenced greatly on the floral differentiation between east and west of the Eurasia. 4)Plio-Pleistocene floral change from Katmandu Basin, Nepal is characterized by a floral modernization from dominance by East Asian elements to an expansion of West Asian elements. 5)East Asian early Holocene plant macrofossil flora reflects original phytogeography before alternations by human impacts.