Scientists have modeled the phylogeographic relationships and demographic changes of Castanopsis sieboldii, which is a dominant tree of the broadleaved evergreen forests of Japan, dating back to about 100,000 years ago. The model strongly suggested that C. sieboldii survived in at least 4 areas through the last glacial maximum (LGM). The results present new evidence concerning conservation of genetic diversity of C. sieboldii.