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Brigham Young University Science Bulletin, Biological Series

Abstract

Little work has been done previously on the taxonomy of Crotaphytus collaris baileyi. This and the demonstration by Fitch and Tanner that C. c. baileyi is a heterogeneous grouping prompted the present study. Only the populations of the type material, the Upper Colorado River Basin, and the Chihuahuan Desert were studied. Multivariate, variance, canonical and discriminant analyses of external characters were performed, and pattern-coloration characters were examined on living specimens.

The results of the analyses show significance between all three populations. The discriminant functions distinguished between the populations with 80% reliability and patternal characters were discriminatory with near 100% reliability. Therefore, a new subspecific name, C. c. fuscus, was applied to the Chihuahuan population.

The collaris-complex was shown to consist of at least four subspecies: C. c. auriceps, C. c. baileyi, C. c. collaris and the new subspecies, C. c. fuscus from the Chihuahuan Desert. C. c. auriceps' range was restricted to the area near Moab, Utah, and north of the union of the Green and Colorado rivers. A broad intergrade zone south into the Painted Desert was established between C. c. auriceps and C. c. baileyi. The range of C. c. baileyi was established as central Arizona. Southern and central New Mexico and most of Mexico east of central Sonora were established as the range for C. c. fuscus. Further study of the populations presently recognized as C. c. collaris was advised.

While all the populations were separable on the basis of morphology, the best characters for identification were color and pattern. C. c. auriceps has a light green body and the yellow of the head extends onto the side of the throat. C. c. baileyi has a darker green body with reduced yellow on the head. The area of the throat between the infralabials and the gular patch is always white. C. c. fuscus has a brown body and a white to cream head.

Important discoveries were also made in methodology. The necessity for using multivariate statistics in taxonomic studies which investigate more than one character was demonstrated. The use of a posteriori probabilities was presented as a new technique for investigation of taxonomic problems involving intergradation.

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