Spatial organization of a rodent community in the Western Rajasthan desert (India)

We studied the distribution of niches in the resource space and niche patterns of a 9-rodent-species community of the Thar desert (Western Rajasthan, India) using discriminant function analysis. We measured eighteen quantitative parameters of the environment (soil structure and vegetation) at 375 sample plots within 15 1-ha grids. The first two canonical axes of resource space account for 95 % of the variance ; the first axis accounting for 89.6 % of the variance represents a general landscape gradient from sand desert with sparse shrub vegetation to sandy-clay soils with dense annual grass vegetation of semi-savannah type. The second axis reflects a gradient of increasing gravel in the substrata with decreasing crown volumes of perennial vegetation. The distribution of niches in the resource space reflects the complex structure of the environment. Considerable opposition of a typical desert psammophilous Gerbillus gleadowi to all other species is a characteristic of geographical location and young age of Rajasthan sand desert. There were no significant correlations between niche position (distance from species centroid to the center of the resource space) and maximal population density or biomass. Also, there were no significant correlations between the niche breadth and the niche position due to the absence of species with quite broad niches. The rodent biomass increased along the first, and, to a lesser extent along the second axis of the resource space and peaked in the most productive semi-savannah areas. Rodent species diversity also increased in parallel fashion, but a more complex, hump-shaped pattern of variation was noted. This could be viewed as a result of a complex structure of the environment and historical events in origin of the fauna.