Chromosomes and Evolution of the Species Groups of Cnemidophorus (Reptilia: Teiidae)

Abstract

Lowe, C. H. (Dept. Biol. Sci., Univ. Arizona, Tucson), Wright, J. W., Cole, C. J., and Bezy, R. L. 1970. Chromosomes and evolution of the species groups of Cnemidophorus (Reptilia: Teiidae). Syst. Zool., 19:128-141.-On the basis of chromosome data, the large and complex genus Cnemidophorus of the New World lizard family Teiidae is divided into five species groups (the deppei, lemniscatus, sexlineatus, tigris, and tesselatus groups). These species groups are, in the main, congruent with those customarily recognized on the basis of external morphology. The hyperythrus species group, however, is placed in the deppei group: (1) all species examined from these two groups have identical karyotypes which differ from those of all other species examined in the genus, and (2) the two groups were formerly distinguished primarily on the basis of a single variable morphological character. The tesselatus group contains two species (tesselatus and neomexicanus), each parthenogenetic and derived through intergroup hybridization. Both of these parthenospecies originated through hybridization between the same two species groups, but different parental species combinations were involved in the production of each of them. The karyotype of the deppet species group appears to be the most primitive among the extant species groups of the genus Cnemidophorus, and the karyotypes of the other species groups are readily derived from it primarily by means of Robertsonian centric fusioins and unequal pericentric inversions. The phylogeny of the genus based on the observed pattern of karyotypic evolution is consistant with the overall ecologic and biogeographic distributions of the species [Karyology; phylogeny; Cnemidophorus]. Based primarily on external morphological characters, five species groups (deppei, hyperythrus, lemniscatus, sexlineatus, and tesselatus) are customarily recognized in the large and complex genus Cnemidophorus of the New World lizard family Teiidae (Burt, 1931; Duellman and Wellman, 1960; Duellman and Zweifel, 1962). Overemphasis of a few external morphlogical characters has led to a certain amount of ambiguity and confusion in the delineation of species groups in the genus (Duellman and Zweifel, 1962:168; Walker, Taylor, and Maslin, 1966b). In problems concerning speciation and evolutionary pathways that have led to natural group assemblages above the species level, it is obviously appropriate to consider data on karyotypes and modes of reproduction. Accordingly, we consider here some of this newer information in conjunction with the more conventional data for species groups in the genus Cnemidophorus and discuss evolutionary relationships suggested by all of these data. ACKNOWLEDGMENTS Numerous graduate students at The University of Arizona have contributed live Cnemidophorus for our karyotypic investigations. In particular, we are grateful for the extraordinary field efforts of the following: Robert J. Baker (now at Texas Technological College, Lubbock), Eldon J. Braun, Stephen R. Goldberg, E. Annette Halpem, David S. Hinds, Richard D. Krizman, James L. Patton (now at The University of California, Berkeley), Michael D. Robinson, and Oscar H. Soule (now at The Missouri Botanical Garden, St. Louis). Kenneth K. Asplund (The University of California, Los Angeles), Joseph R. Lannom (The University of Utah, Salt Lake City), and Philip J. Regal (The University of California, Los Angeles) also contributed lizards that were particularly useful for