We searched for areas of syntopy between hybrid-derived clonal complexes A and B of Cnemidophorus laredoensis and both of their gonochoristic progenitors, C. sexlineatus and C. gularis, in Texas and México from 1983 through 2000. We discovered that all sites inhabited syntopically or separately by these two clonal complexes of lizards are contained within the vast binational range of C. gularis, a widely tolerant species that is either present, or exists in neighboring plant communities, at all sites inhabited by these parthenogenetic forms. Conversely, the only sites of syntopy between C. laredoensis A and B and C. sexlineatus discovered during our study were clustered in a small area of northern Webb County, Texas. The basis for extensive syntopy between C. laredoensis A and B and maternal progenitor C. gularis and limited syntopy between these parthenogenetic forms and paternal progenitor C. sexlineatus includes components of both species-specific ecological adaptations and zoogeographical histories.