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

本研究的目的是阐明第三纪以来欧亚大陆温带植物区系分化过程与环境变化之间的关系。研究了在欧亚大陆广泛分布并随新近纪气候变化在日本和波兰分化的Fagus和Trapa等化石类群的形态。此外，我还根据最近的地质资料分析了化石组合的组成，包括分类群及其沉积环境。结果如下：(1)晚中新世最早的Fagus和Trapa化石中，日本与中欧没有明显的形态分化，表明欧亚大陆东西有花系联系的可能性。(2)日本Fagus化石叶的形态变化与欧洲化石相似。中中新世至上新世以来，次脉数量减少，叶片宽度变宽。3)晚中新世以来，蕨类、水杉类和水杉类植物分布减少的过程表明，晚中新世以来的气候恶化对欧亚大陆东西区花的分异有重要影响。尼泊尔的特点是花卉现代化，从东亚元素的主导到西亚元素的扩展。5)东亚早全新世植物大化石区系反映了人类影响变化前的原始植物地理特征。

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.