| In order to provide genetics basis for the classification of the subspecies of Microtus fortis in china, the chromosome, isozyme, protein, DNA were used to study the genetic characteristics and phylogenetic relationship of four groups of close-bred Microtus fortis from three regions -Hunan, Ningxia as well as Heilongjiang.We observed the chromosomes of the bone marrow cells from four groups of Microtus fortis. The formulas of karyotype were as follows: for voles from Hunan, 2n = 52 = 12( m + sm ) + 38( t + st) + XY ( m, t); for voles from Ningxia, 2n = 52 = 10( m + sm ) + 40( t + st) + XY( m, t); for big voles from Heilongjiang, 2n = 40 = 18( m + sm ) + 20( t + st ) + XY( t, t); for small voles from Heilongjiang, 2n = 40 = 16( m + sm ) + 22( t + st) + XY( m,t).Ten isozymes and proteins were investigated by cellulose acetate membrane electrophoresis, the phylogenetic relationship among four groups of Microtus fortis was analyzed based on the alleles frequency at these biochemical loci. All groups of Microtus fortis showed polymorphism at most of the ten loci investigated. The electrophoretic mobilities of the small voles from Heilongjiang revealed great divergence with the other three groups: the small voles from Heilongjiang had their particular alleles at six loci (Es-1, Hbb, Gpi, Akp-1, Trf-1, Ce-2) and the phenotypes of them were completely different at three (Es-1, Hbb, Gpi-1) of these loci. The genetic distances among the voles from Hunan, Ningxia and the big voles from Heilongjiang were ranged from 0.0633 to 0.2107 while that between the small voles from Heilongjiang and the other three groups were ranged from 0.7068 to 0.8953. The phylogenetic tree constructed by UPGMA showed that: the voles from Hunan, Ningxia and the big voles from Heilongjiang could be gathered in one group (the voles from Hunan and Ningxia gathered firstly, then gathered to the big voles from Heilongjiang ), but the small voles from Heilongjiang were in the other group alone. These results indicated that the phylogenetic relationship among the voles from Hunan, Ningxia and the big voles from Heilongjiang is closer than that between the small voles from Heilongjiang and them.We present a preliminary study on the zymograms of esterase (EST), lactatedehydrogenase (LDH), malate dehydrogenase (MDH) from four groups of Microtus fortis by vertical discontinous polyacrylamide gel electrophoresis method. The number, mobility and dye intensity of the enzyme band were analyzed. The results revealed that: (1) The zymogram of EST isozyme in the livers from all Microtus fortis existed widespread polymorphism. They were similar to each other at the I area while quite different at the III and IV area. At the II area, the voles from Hunan, Ningxia and the big voles from Heilongjiang were close but the difference between the small voles from Heilongjiang and three other groups was obviously. (2) The liver MDH isozymes of Microtus fortis were rather conservation in evolution. The MDHm zones of all voles were located to the same migratory line with the similar activity. The migratory rates of the MDHs zones from all voles were identical but the activity of MDHs of the voles from Ningxia was weaker than that of the other voles. (3) There was only LDH5 in the livers of all groups of Microtus fortis. The LDH4 and LDH5 were absent in the kidneys of the small voles from Heilongjiang, but five kinds of LDH isozymes were all found in the kidneys of the other three groups.By means of the random amplified polymorphic DNA (RAPD) technique we analyzed the genome DNA from four groups of Microtus fortis. The RAPD results indicated as the following: The average band similarity index ( ABS) within each group of Microtus fortis is high: for voles from Hunan, 0.9287+0.0436; for voles from Ningxia, 0.9223+0.0533; for big voles from Heilongjiang, 0.9515 + 0.0289; for small voles from Heilongjiang, 0.8900 + 0.0328. The genetic similarity coefficients (I) among the voles from Hunan, Ningxia and the big voles from Heilongjiang were all up to 0...
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