第四紀の東アジアにおけるジャイアントパンダ属の分布

The genus Ailuropoda includes the extant giant panda (A. melanoleuca) which is now restricted to small areas of high mountains in South China, and inhabits mainly bamboo forests there. This paper reviews chronospatial distributions of the genus in East Asia during the Quaternary on the basis of published data including recent ones. The genus comprises two species such as A. microta of the early Early Pleistocene and A. melanoleuca of the middle Early Pleistocene onward. The latter species includes two fossil subspecies such as A. m. wulingshanensis and A. m. baconi (= A. m. fovealis). We have made distribution maps of the genus in East Asia for the Early, Middle, and Late Pleistocene as well as for the Holocene, which indicate its chronospatial distribution. The maps show that the localities are almost restricted to the land area of South China and their distributions are much wider in all the periods of the Quaternary than the present-day distribution of A. melanoleuca. However, the localities are absent from the land areas of East Asia other than South China except those just north of the Qinling Mountains as well as from the prsent-day sea areas of East Asia where mammal fossils have obtained from some places on the seabed. In the Pleistocene fossil localities mapped, the genus is mostly associated with the extinct proboscideans (Stegodon, especially S. orientalis in the Middle and Late Pleistocene localities). S. orientalis has also occurred in the Middle Pleistocene of Honshu-Shikoku-Kyushu in mainland Japan. This fact indicates that S. orientalis immigrated from South China to Honshu-Shikoku-Kyushu in the Middle Pleistocene through a land bridge formed between them, but no fossil records of Ailuropoda are known from Honshu-Shikoku-Kyushu. It is inferred that continuous bamboo forests from South China were not formed on the land bridge, and Ailuroloda could not immigrate into Honshu-Shikoku-Kyushu.