Genetic diversity and differentiation of coniferous species have been studied extensively using allozyme in the last two decades. Recently, the development of molecular techniques and knowledge have enabled phylogeographical studies using organelle DNA polymorphisms. We can now point out the original population in the ancient time and clarify historical change and/or expansion of distribution areas along climatic changes. In Japan, genetic diversity and differentiation have been studied in ten species of conifers so far. Among them, Pinus pumila, P. thunbergii, Abies homolepis, A. firma, and Chamaecyparis obtusa showed a clear geographical cline in their genetic diversity. Historical change of their distribution and factors leading to the cline formation are discussed. Finally, the future perspective for the study of historical distribution change by molecular population genetics is also discussed.
Plant macroremains of the Early Jomon Period obtained from the Ireibaru C Site at Chatan Cho, Okinawa, were described. In the Early Jomon horizon, plant macroremains composed middens with sea shells, bone tools, and Sobata-type potteries. We could identify 56 taxa with 17 unkown taxa. Fruits of Fagaceous trees, probably Castanopsis, and Pandanus odoratissimus were abundant. Morus, Broussonetia papyrifera, Mallotus, Elaeocarpus sylvestris, Styrax japonicus, Ehretia, Scirpus, Najas, and Melothria were relatively common. Dominance of Fagaceous fruits in the plant macroremain assemblage of this site seemed to imply selective dumping of these fruits at this site. Results of this site and the Mehbaru Site of the Late Jomon Period indicated that Fagaceous fruits were possibly important food resources also in Okinawa Island as in the mainland Japan during the Jomon Period.
Warm temperate mixed forests consisting of conifers (Pinus, Abies, Tsuga, and Pseudotsuga) and deciduous broad-leaved trees (Carpinus, Zelkova, Fagus, and Quercus subgen. Lepidobalanus) were reconstructed from fossil pollen and plant macrofossil assemblages in Middle Pleistocene deposits at Ohnodai (134°00´E, 33°26´N, Alt. 40–50m), Muroto-misaki Peninsula, Kochi Prefecture. The sediments including the fossil assemblages were identified as marine sediment, because they contained sulphur and fossil fruits of a seaside plant (Vitex rotundifolia L.f.), and were correlated with the Ma5 Marine Clay Layer in the Osaka Group based on topographic and paleomagnetic investigations. At the time of deposition of the fossil assemblages, evergreen broad-leaved trees such as Castanopsis and Quercus subgen. Cyclobalanopsis scarcely flourished in this area, while lucidophyllous forests were widely distributed during the Holocene in this same area. The difference in vegetation between the two interglacial periods suggests difference in climatic conditions, especially winter temperature defining the development of evergreen broad-leaved forests.