GEOGRAPHICAL ECOLOGY OF MONGOLIAN DESERT RODENT COMMUNITIES

We analysed the spatial organization of Mongolian desert rodent fauna by stepwise discriminant function analysis and cluster analysis. Geogr aphical variation in niche breadth and niche position among three comm unity types of Southern, Western and Eastern Gobi was considered in ov erall coordinates for the whole desert. To reduce the environmental co nstraints in regional communities, niche breadth was estimated along c omparable parts of discriminant axes and was measured by use of the Sh annon-Weaver index. Niche overlap values were calculated for each of t he three communities as a probability of displacement along the discri minant axis. Guild structure of the fauna reflects the adaptation of s pecies to the range of main landscape types of the desert zone. Specie s shift their preferences along the axes of ecological space independe ntly. These results challenge the viewpoint that the spatial-guilds ar e stable co-adapted assemblages. The nearest neighbor analysis of nich e overlap indicates the absence of dense niche packing in the southern Mongolian desert, whereas the relatively even distribution of niche o verlap in communities of the northern Mongolian desert suggests more d ense niche packing. We did not find any features of regularity in body size distribution among Mongolian desert species. Pairs of congeneric species with low and high niche overlap have the same body weight rat io.