Applying the Mutual Climatic Range method to the beetle assemblages in Japan using accurate data of climate and distribution of modern species

The Mutual Climatic Range method of Paleotemperature reconstruction is well suited to Japan, because the meteorological stations are densely located, and the modern distributions of beetles are well studied. Many of the cold adapted species which were in the Japanese lowlands during glacial periods still survive at higher elevations on the Japanese Archipelago, in high mountain refuges. A new way of drawing convex polygons as species envelopes is proposed here, make the method more accurate and objective. A test analysis using four beetle species from a stratum in the Nojiri-ko site, Nagano Prefecture is presented. The test shows a decline of temperatures, the first example of MCR from East Asia. The result agrees with the previous estimation based on modern range overlaps and on reconstructions based on vegetation.