Genetic and population structure of the least shrews Sorex minutissimus in Eurasia

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In 2005, samples obtained from reserved specimens and those captured by myself is as follows : 15 specimens from Finland, 1 from Norway, 1 from Kamchatka, 4 from Magadan region (Russia), 5 from Primorski, 1 from Khabarovsk region, 2 from Sakhalin, 1 from Kunashiri Island, 11 from Satobetsu (Hokkaido), 5 from Nemuro, 2 from Hamanaka-cho, and 5 from Kenbokki Island. In 2006, 12 shrews from Shiranuka-cho (Hokkaido), 1 from Sarufutsu-mura, and 1 from northern Mongolia were captured by myself. According to the sampling, new knowledge about habitat of Sorex minutissimus was obtained. Sorex minutissimus was captured in sand dune and rocky place, which are rarely used by other shrew species. Thus, it is suggested that S. minutissimus might be pushed to unpreferable habits by other competitively dominant species.Phylogenetic investigation was conducted based on sequences of the mitochondrial cytochrome b and the control region. Populations genetically rather differentiated between the eastern and western parts of Eurasia. In addition, within the eastern Eurasian population, genetic diversification was observed, corresponding to geographic position. There was little genetic variation within Hokkaido population whereas there was much genetic variation within Finnish population although sampling area were almost the same between the two. The low genetic variation in Hokkaido population may be the result of a recent bottleneck event of population. The high variation in Finland may have been related to continental ice sheet development in the last glacial age. In the last glacial age, northern Europe was covered with ice sheet. Thus, Finnish S. minutissimus might have retreated to several refugia and returned to the Finland from several regions after warming, causing a genetic mixture of various haplotypes.