2008 Volume 25 Issue 1 Pages 51-61
It is well-known that among the Castanopsis genus of Japan, Castanopsis sieboldii tends to distribute around the coastal regions and C. cuspidata distributes more inland. Although the detailed distribution pattern is unknown, the existence of an intermediate type that falls somewhere between both the species is known in the natural and secondary forests. Whether or not the intermediate type is considered a hybrid or an intraspecific variation differs depending on the researcher. This study aimed to clarify the distribution patterns of the Castanopsis species and their hybrids in 30 regions in southern Kyushu. In addition, detailed studies were conducted on the hybrid population around the coastal area of Mt. Inao, which is located on the southernmost tip of Kyushu and the Kugino Woods Tree Inheritance Resource Preservation Forest located inland. In this research, the discrimination method of the Castanopsis species based on the structure of leaf epidermis was improved by establishing the observational area of the specimen through a microscope. The following three hybrid types were distinguished based on the ratio of one-cell layers and two-cell layers of the leaf epidermis: C-type (the ratio of one-cell layers is high), H-type (the ratio of one and two-cell layers is almost equal), and S-type (the ratio of two-cell layers is high). From the results, the Kirishima region with its higher altitudes had only the distribution of C. sieboldii, and C. cuspidata showed a tendency to be distributed in the regions of relatively lower altitudes, including the inland regions. Five hybrids were found in the coastal region around Mt. Inao, and all five were S-type. On the other hand, Kugino had distribution patterns of C. cuspidata, the hybrid, and C. sieboldii in order as the altitude increased. The distribution patterns of three hybrid types were related to the distribution patterns of individuals of the mother species. The form of the Castanopsis nut was related to the distribution patterns of individuals of the mother species.
