EVOLUTIONARY STUDY ON THE TERTIARY FAGACEAE

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THE FAGACEAE IS A LARGE FAMILY OF TREES AND SHRUBS, WHICH ARE DISTRIBUTED IN THE BOTH HEMISPHERES. IT IS THE PURPOSE OF THIS PROJECT TO INVESTIGATE PHYLOGENY AND STRATIGRAPHIC DISTRIBUTION OF EACH GENERA OF THIS FAMILY, BASED ON MACRO-AND MICROFOSSILS.1. NEARLY 200 LEAVES OF THE EXTANT FAGUS CRENATA COLLECTED FROM 154 LOCALITIES OF JAPAN, WERE EXAMINED ON LEAF ARCHITECTURAL CHARACTERS. THIS INVESTIGATION SHOWS THAT THE VENATION, ESPECIALLY VEINLETS NUMBER AND AREOLE SIZE, IS INVARIABLE AGAINST THE DIFFERENT CLIMATIC CONDITIONS OF SAMPLING LOCALITIES.2. REINVESTIGATING THE VENATION DETAILS FOR FOSSIL LEAF AND MORPHOLOGY FOR FOSSIL CUPULES AND SEEDS, ALL THE KNOWN SPECIES OF THE GENUS FAGUS IN EAST ASIA ARE REDESIGNTED AS 8 SPECIES. THE COMPARISON OF THESE 8 SPECIES WITH THE EXTANT SPECIES OF THE WORLD, REVEALS THAT EAST ASIAN FAGUS ORGINATED FROM THE F. GRANDIFOLIA GROUP, DIVERGED TO TWO PHYLADS IN THE MIDDLE MIOCENE, AND THAT THE TWO EXTANT SPECIES OF JAPAN APPEARED SINCE THE LATEST MIOCENE.3. INVESTIGATING CLEARED LEAVES OF ABOUT 220 OAK SPECIES, AN IDENTIFICATION SHEME FOR THE SUBGENERA AND SECTIONS OF THE GENUS QUERCUS IS ESTABLISHED ON THE BASIS OF LEAF ARCHITECTURE. BASED ON THIS SCHEME, A NUMBER OF FOSSIL OAK LEAVES DESCRIBED FROM THE TERTIARY OF EAST ASIA ARE REDESIGNATED AS 12 SPECIES. ALL THE DECIDUOUS OAKS FROM THE EOCENE TO EARLY MIOCENE BELONG TO SECTION CERRIS AND ALBAE, AND THOSE OF SECTION ILEX, SUBER AND DENTAE APPEARED SINCE THE MIDDLE MIOCENE. HOWEVER, FOSSIL LEAVES OF CYCLOBALANOPSIS REMAINED TO BE UNSOLVED IN PHYLOGENY.4. ALL THE FOSSILS REPORTED AS THE FAGACEAE FROM THE WORLD ARE EXAMINED. THE DIVERGENCE INTO THREE SUBFAMILIES OF FAGACEAE OCCURRED IN THE PALEOCENE OR EARLY EOCENE TIME, AND THE SPECIMENS REFERABLE DOUBTLESSLY TO THE EXTANT GENERA ARE CONFIRMED FIRST IN THE LATEST EOCENE OR EARLY OLIGOCENE.