The heterogeneous nature of the collared lizards west of the Colorado River prompted this study. Samples from known populations of C. c. auriceps, C. c. baileyi, and C. c. fruscus were used as a base for defining the western populations. External morphology and cranial morphology were compared by cluster, canonical, and discriminant analyses.
Results of these analyses show a western complex of four populations which are distinct from the three base populations of the collaris complex. Members within the western complex are distinguishable with at least 90 percent reliability by discriminant analysis. Because of intergradation patterns seen in western Sonora, Mexico, Crotaphytus dickersonae is considered to be Crotaphytus collaris dickersonae. The Great Basin population is retained as Crotaphytus collaris bicinctores. The population from southern California and Baja California, which is distinct and has no demonstrated intergrades with C. c. bicinctores, is considered Crotaphytus insularis vestigium, and the population from Isla Angel de la Guarda is designated Crotaphytus insularis insularis.
The range of C. c. dickersonae is shown to extend from Isla Tiburon onto the Sonoran coast opposite the island and from Bahia Kino north to El Desemboque. Crotaphytus c. bicinctores extends from the Yuma, Arizona, area north through eastern California, western Arizona, Nevada, central Utah (west of the Colorado River), southern Idaho, and southeastern Oregon. The western range of C. c. baileyi is restricted to central Arizona. The range of C. i. insularis is restricted to Isla Angel de la Guarda and C. i. vestigium to a narrow strip extending along the eastern mountain slopes from central Baja California, Mexico, to the foothills south of the San Gorgonio Pass, near Palm Springs, California.
Smith, Nathan M. and Tanner, Wilmer W.
"A taxonomic study of the Western Collared Lizards, Crotaphytus collaris and Crotaphytus insularis,"
Brigham Young University Science Bulletin, Biological Series: Vol. 19
, Article 1.
Available at: https://scholarsarchive.byu.edu/byuscib/vol19/iss4/1