Genetic homogeneity based on skin histocompatibility and the evolution and systematics of parthenogenetic Cnemidophorus laredoensis (Sauria: Teiidae)

Abstract

The parthenogenetic whiptail lizard Cnemidophorus laredoensis of Texas and México was derived from one or more hybrids between the gonochoristic species Cnemidophorus gularis and Cnemidophorus sexlineatus. We analyzed clonal structure in C. laredoensis on the basis of histocompatibility reactions to reciprocal skin grafting. Individuals of C. laredoensis rejected skin grafts from both parental species and from a hybrid between C. gularis and an undescribed parthenogenetic species. One lizard initially identified as C. laredoensis was found to be a triploid C. laredoensis × C. gularis hybrid, based on its histocompatibility reactions. The hybrid accepted grafts from individuals of C. laredoensis; however, C. laredoensis rejected grafts from this and a second hybrid. Seventeen individuals of C. laredoensis from six sites located throughout the range of the species in Texas were fully histocompatible, based on a large number of reciprocal skin grafts. Only three individuals of C. laredoensis from three sites donated grafts to other individuals of the species, but they were unable to host all or most of the reciprocal grafts. The skin histo compatibility among 17 individuals of C. laredoensis from six widely separated geographic sites points to a high level of genetic homogeneity in the species due to clonal descent from one parthenogenetic C. gularis × C. sexlineatus hybrid. Unidirectional rejection of skin grafts by three lizards could be a result of postformational mutations within this lineage, though this suggestion is open to question. The name C. laredoensis should be restricted to populations in Texas and México that are diagnostically identical with the parthenogenetic species described from two sites in Laredo, Webb County, Texas, in 1973.