THE DISTRIBUTION OF CALLIGONUM-POLYGONOIDES L IN WESTERN RAJASTHAN, INDIA - A PHYTOGEOGRAPHICAL APPRAISAL

The occurrence and distribution of the shrub Calligonum polygonoides L. and the vegetation associated with it is used as an index for the phytogeographical demarcation of the western Rajasthan desert of India into arid and semi-arid regions. The distribution of this species is presented according to districts based on pre- and post-monsoonal field observations made in recent years. Four types of vegetational associations of Calligonum were observed in the area. This shrub is more predominant in the districts of Jaisalmer and Bikaner than elsewhere. The region has five main refugia of relict forms. It is almost absent from Nagaur district. Analysis of the distribution of the shrub in western Rajasthan indicates that geographical isolation has played an important role for its occurrence.